Range Sensor Brick for Modular Robotics

Range Sensor Brick for Modular Robotics

A Project in Lieu of Thesis Presented for the Master of Science Degree In Electrical and Computer Engineering

Santosh B. Katwal December 2004

Imaging, Robotics, and Intelligent Systems Laboratory Department of Electrical and Computer Engineering The University of Tennessee Email: [email protected]

Acknowledgements I would like to dedicate this work to my parents: my father, Ram B. Katwal, and my mother, Urmila Katwal, who have always been my source of inspiration and energy for hard-work. I am greatly indebted to them for their continuous support and unconditional love. My sister, Archana Katwal, and my brother, Shyam B. Katwal, are also greatly responsible for boosting my career. Thanks very much for your love and affection. I would like to express my sincere gratitude to my advisor Dr. Mongi A. Abidi who nurtured me and helped me to complete my Masters. His great persona and positive attitude towards work have helped me a lot to come out as a more professional and hardworking person. He is greatly responsible for the inception and completion of this research work. Thanks a lot, Sir! I would like to thank Dr. Laura M. Edwards who worked as my lead faculty for a couple of semesters. Her friendly nature and a habit of encouraging her students are inexplicable. I also thank Dr. David L. Page for being my lead faculty for a semester. He helped me to learn more about work ethics and individual responsibilities. I am also indebted to Dr. Andrei Gribok for his hard work to complete this thesis writing. He helped me in a great deal to hone my writing skill and organize the materials for this thesis. I am thankful to Dr. Andreas Koschan and Dr. Besma Abidi for their moral support. Thanks are also due to Dr. Seong Kong for being an integral part of the thesis committee and his invaluable suggestions towards the work. I also thank Justin Acuff and Doug Warren for their precious help with the hardware and mechanical stuffs in this research. I would like to thank Vicky Courtney Smith and Kim Cate for their help with the administrative work. Lastly, I am thankful to all the IRIS lab students and colleagues for their support and help throughout my Masters. I am grateful to have such a wonderful company. Thanks a lot.

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Abstract This thesis describes the designing and building of the “Range Sensor Brick” for modular robotics. The technology and principle of operation of the range sensor brick have been presented in detail with an in-depth description of the hardware and software architecture of the brick. The range sensor brick extends the idea of devising a generic, compact, modular and independent sensor brick technology by specializing in the range or depth sensing technique. The concept of modularity evolved with the wide gamut of applications in mind, primarily in the navigation of the robot. The range sensor is capable of providing the 3D geometry of the object and the range map of the surrounding space thus helping in traversing a path for the robot. The brick can also be maneuvered for scanning the road surface which could be useful for analyzing the road terrain. There are several other fields of application where the brick can be put into operation. Under-vehicle inspection for threat detection poses serious challenges especially with traditional method of inspection in the form of “mirror-ona-stick”. The method worsens with low illumination condition and difficulties in accessing the complete under-vehicle surface including the narrow and hard-to-reach areas. Range sensor brick placed on a low-level track wheeled robotic platform offers an efficient and scientific way of performing the under-vehicle inspection irrespective of illumination condition and region under the vehicle. Laser range sensor can be employed to measure the geometry of objects and the range map of the surrounding space. It operates by sweeping a laser across a scene and at each angle measuring the range and the returned intensity. Range images are different from the images acquired by a normal camera in a sense that a normal camera measures reflected light from the scene being observed and each pixel value of the obtained image represents the intensity of the reflected light value, whereas the pixel value of a range image represents the distance from the object being acquired by the camera. The range sensor brick comprises a laser scanner (LMS 200 manufactured by the SICK Inc.) for acquisition, micro ATX board (ASUS P4GE-VM) for preprocessing of the acquired range data and wireless network card (Linksys wireless-G) for communication with the central control unit or remote server that could control the operation of the sensor brick. The power unit comprises PW-200-V dc-to-dc converter for the motherboard, VI-LJ03-CY dc-todc converter for the Sick scanner and a 12 V Panasonic LC-RA1212P battery. Software is developed for performing the data acquisition and data visualization from the range sensor brick. The GUI has been developed in Borland C++ builder and Visual C++.NET and it has the provision for displaying the range profiles and the range image of the acquired scene in real time.

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Contents ABSTRACT............................................................................................................................ II 1 1.1

INTRODUCTION........................................................................................................... 1 Motivation..................................................................................................................... 1

1.2 Application.................................................................................................................... 4 1.2.1 Navigation................................................................................................................. 4 1.2.2 Under-vehicle Inspection .......................................................................................... 5 1.2.3 Road Profiling and Terrain Mapping........................................................................ 6 1.2.4 Reverse Engineering ................................................................................................. 6 1.3 2

Document Organization ................................................................................................ 7 HARDWARE ARCHITECTURE................................................................................. 8

2.1 Acquisition Block ......................................................................................................... 8 Technical Specifications ..................................................................................................... 11 2.2 Preprocessing Block.................................................................................................... 11 Technical Specifications ..................................................................................................... 13 2.3

Communication Block ................................................................................................ 13

2.4 Power Block................................................................................................................ 15 2.4.1 PW-200-V (12V), DC-to-DC Converter................................................................. 17 2.4.2 VI-LJ03-CY 12V-to-24 V, DC-to-DC Converter................................................... 18 2.4.3 Panasonic LC-RA1212P, Lead-Acid 12V Battery ................................................. 19 2.5

Physical Layout of the Brick....................................................................................... 20

2.6

Electrical Circuit and Power Distribution Diagrams .................................................. 24

2.7

Bill of Materials .......................................................................................................... 26

2.8

Brick Models............................................................................................................... 27

3

SOFTWARE ARCHITECTURE ................................................................................ 31

3.1 Communication Interface between Sick and the Host Computer............................... 31 3.1.1 RS 232..................................................................................................................... 32 3.1.2 RS 422..................................................................................................................... 32 3.2

Communication Technique......................................................................................... 34 iii

3.3 GUI Design ................................................................................................................. 37 Steps of Operation............................................................................................................... 37 4

DATA COLLECTION WITH THE RANGE SENSOR BRICK............................. 46

4.1

Scanning along the Length of the Vehicle.................................................................. 47

4.2

Scanning along the Width of the Vehicle ................................................................... 51

4.3

Scanning with the threat object placed under the vehicle without jacking it up......... 52

5

CONCLUSIONS ........................................................................................................... 54

6

FUTURE WORK .......................................................................................................... 56

BIBLIOGRAPHY ................................................................................................................. 57 APPENDIX............................................................................................................................ 58 A.1 Components and Typical Setup of LMS 200................................................................... 58 A.2 Interface Plugs (Plug Modules)........................................................................................ 59 A.3

LMS 200/LMS 291 Electrical Connection ................................................................. 60

A.4

RS 232/RS 422 Conversion ........................................................................................ 61

VITA....................................................................................................................................... 62

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List of Tables Table 2.1: Major specifications of the LMS 200 Sick scanner (Taken from [Sic02])............ 11 Table 2.2: Major specifications of the ASUS P4GE-VM board (Taken from [Asu04]). ....... 13 Table 2.3: Comparison between different members of IEEE 802.11 wireless technologies.. 14 Table 2.4: Electrical specifications for PW-200-V (Taken from [Pw204])............................ 17 Table 2.5: Panasonic LC-RA1212P lead acid battery product specification (Courtesy: [Pan04])........................................................................................................................... 19 Table 2.6: Panasonic LC-RA1212P lead acid battery characteristics (Courtesy: [Pan04]).... 20 Table 2.7: Bill of materials for the range sensor brick. .......................................................... 27 Table 3.1: Relations beween angular resolution and maximum number of range values (Courtesy: [Hai03])......................................................................................................... 31 Table 3.2: Differences between RS232 and RS 422 (Courtesy: [Hai03]). ........................... 33 Table 3.3: LMS Addresses (Courtesy: [Hai03]). ................................................................... 35

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List of Figures Figure 1.1: Range sensor brick placed on the low-platform track wheeled under-vehicle robot. ................................................................................................................................. 2 Figure 1.2: Generic sensor brick architecture. .......................................................................... 3 Figure 1.3: (a) Indoor vehicle equipped with the Sick scanner, (b) map of an indoor environment generated using the Sick scanner (Taken from: www.acfr.usyd.edu.au). ... 4 Figure 1.4: “Mirror -on-a-stick” for under-vehicle inspection (Taken from: www.lynnrobertsonline.com) ........................................................................................... 5 Figure 1.5: (a) Low–level track wheeled under-vehicle robot, (b) range sensor brick placed on the robotic platform performing the under-vehicle inspection. ................................... 6 Figure 1.6: Range scanner placed on the vehicle edge to scan the road (Taken from imaging.utk.edu/research/grinstead/projects.htm). ........................................................... 6 Figure 1.7: (a) Visual image of a socket, (b) 3D range image of the socket. ........................... 7 Figure 2.1: Range sensor brick architecture and its components.............................................. 8 Figure 2.2: Sick LMS 200 scanner. .......................................................................................... 8 Figure 2.3: Spot Sizes/Spot Spacing (Taken from [Sic02])...................................................... 9 Figure 2.4: Operating principle of Sick LMS 200 (Taken from [Hai3]). ................................. 9 Figure 2.5: Principle of the time-of-flight............................................................................... 10 Figure 2.6: Mother-board (ASUS P4GE-VM) for preprocessing........................................... 12 Figure 2.7: Linksys wireless-G PCI card for communication. ............................................... 15 Figure 2.8: Power block architecture. ..................................................................................... 16 Figure 2.9: PW-200-V DC-DC converter............................................................................... 18 Figure 2.10: VI-LJ03-CY dc-to-dc converter. ........................................................................ 18 Figure 2.11: Panasonic LC-RA1212P lead acid battery. ........................................................ 19 Figure 2.12: Isometric view of the first physical layout. ........................................................ 21 Figure 2.13: Top view of the aluminum sheet which houses all the components of the brick. ......................................................................................................................................... 22 Figure 2.14: Different views of the outer box which encloses the aluminum sheet with the components of the brick.................................................................................................. 23 Figure 2.15: (a) Top view of the sheet for the cover at the top, (b) Top view of the sheet for making the box. A 29×33 piece of sheet metal is cut and 6”×5 5/8” piece is stripped off from each corner. The sides are then bent to form the box as shown in the Figure 2.14. ......................................................................................................................................... 23 Figure 2.16: Top View of the cover for the box which houses the Sick scanner. .................. 24 Figure 2.17: Electrical circuit diagram of the range sensor brick........................................... 25 Figure 2.18: Power distribution diagram of the range sensor brick........................................ 26 Figure 2.19: (a) Front view of the first model of the brick made of wooden box, (b) Isometric view................................................................................................................................. 27 Figure 2.20: (a) Top view of the second model of the brick circuitries using the CPU casing, (b) Front view. ................................................................................................................ 28 Figure 2.21: (a) Top view of the second model of the brick using the CPU casing for packaging, (b) Front view. .............................................................................................. 28 vi

Figure 2.22: (a) Top view of the aluminum sheet which houses the components, (b) Front view of the box which encloses the aluminum sheet...................................................... 29 Figure 2.23: (a) Front view of the brick components housed on the aluminum sheet, (b) Isometric view................................................................................................................. 29 Figure 2.24: (a) Front view of the range sensor brick (first prototype), (b) Isometric view... 29 Figure 2.25: (a) Side view of the brick showing the switch that controls the operation of the processing board, (b) Side view of the brick showing the switch to control the operation of the Sick scanner. ......................................................................................................... 30 Figure 2.26: (a) Front view of the range sensor brick on the track wheeled robotic platform, (b) Isometric view. .......................................................................................................... 30 Figure 3.1: Unbalanced single-wire (RS 232) and two-wire transmission (Courtesy: [Hai03]). ......................................................................................................................................... 32 Figure 3.2: Balanced (RS 422) transmission (Courtesy: [Hai03]).......................................... 33 Figure 3.3: GUI for the operation of the range sensor brick................................................... 38 Figure 3.4: Step 1- Selecting the COM port. .......................................................................... 39 Figure 3.5: Step 2- Selecting the baud rate. ............................................................................ 39 Figure 3.6: Step 3- Opening the port. ..................................................................................... 40 Figure 3.7: Step 4- Receiving the confirmation data. ............................................................. 40 Figure 3.8: Step 5- Click on the “Config Mode” button to enter the configuration mode of the scanner. ........................................................................................................................... 41 Figure 3.9: Step 6- Click on the “Change Baud” button to change the speed of the scanner. 41 Figure 3.10: Step 7- Click on the “Get LMS Status” button to ensure the scanner has reached the maximum baud rate configuration. ........................................................................... 42 Figure 3.11: Step 8- Click on the “Get LMS Type” button. ................................................... 43 Figure 3.12: Step 9- Click on the “Continuous Scan” button to start scanning...................... 44 Figure 3.13: Step 10- Click on the “Stop” button to stop scanning........................................ 44 Figure 3.14: (a) Real time continuous line profiles, (b) real time range image of the muffler section of the under-vehicle. ........................................................................................... 45 Figure 3.15: GUI designed in Visual C++.NET (Showing range profiles). ........................... 45 Figure 4.1: (a) Low-platform track wheeled under-vehicle robot with the range senor brick, (b) Dodge RAM 3500 IRIS van...................................................................................... 46 Figure 4.2: (a) Visual image of the under-vehicle showing the muffler and the shaft, (b) Visual image of the catalytic converter. ......................................................................... 47 Figure 4.3: (a) Visual image of the differential, (b) Visual image of the muffler. ................. 47 Figure 4.4: (a) Scanning along the length of the vehicle, (b) Scanning along the width of the vehicle. ............................................................................................................................ 48 Figure 4.5: (a) through (f) - Range images of the under-vehicle obtained by scanning along the length of the vehicle with the van jacked up to a height of 60 inches from the ground. ............................................................................................................................ 49 Figure 4.6: (a) through (h) - Range images of the under-vehicle obtained by scanning along the length with the van jacked up to a height of 32” from the ground. .......................... 51 Figure 4.7: (a) through (f) - Range images of the under-vehicle obtained by scanning along the width of the vehicle with the van jacked up to a height of 49”................................. 52 Figure 4.8: (a) Color coded range image, (b) Grey-coded range image of the muffler section without jacking the vehicle up. ....................................................................................... 53

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Figure 4.9: (a) Color coded range image, (b) Grey-coded range image of the muffler section with the threat object without jacking the vehicle up. .................................................... 53 Figure A.1: LMS 200/ LMS 291 components and typical setup. ........................................... 58 Figure A.2: Scanner with Plug-in connection boxes. ............................................................. 59 Figure A.3: Electrical connection. .......................................................................................... 60 Figure A.4: Interface plug....................................................................................................... 61

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1 Introduction This thesis describes the project on building an independent unit for sensing the depth of the scene, the Laser Range Sensor Brick. The brick is capable of acquiring the images of the scanned objects and scenes through LMS 200 Sick scanner, preprocessing or postprocessing the raw data or image to the required extent, if necessary, and then communicating with the remote host or destination by sending and receiving the data and images or video back and forth in real time for decision-making. This thesis is aimed at providing an insight into the technology and the principle and steps of operation of the Range Sensor Brick with in-depth descriptions on the software and hardware architecture of the brick. The overall idea of the Range Sensor Brick is to devise a generic and independent sensor brick architecture with a maximum possible extent of modularity, compactness and autonomous capability. The purpose of such a flexible architecture is to widen the range and area of applications of the brick. The designing of the sensor brick layout started with the motive of incorporating it as a plug and play device for the modular, multipurpose and multi-sensor robot for navigation. The modularity would help in enhancing the capabilities of the brick to be able to use it as a plug and play sensor device. The brick will have its own acquisition, processing, communication and power units which would enable it to perform the acquisition and processing of the input data locally as well as remotely by communicating with the local and the remote host as per requirement. Because of its modularity and independent capability, the brick can be incorporated for several other applications, primarily for the purpose of under-vehicle scanning for security. Laser range scanner is a special type of sensor, which uses laser light for determining the shape and geometry of the object or scenes. Unlike normal camera, which captures the reflected light from the object, laser range sensor measures the distance of the object being scanned from the reference point on the sensor. Therefore, each pixel in a normal image represents the intensity value whereas that in case of a range image represents the range. Range is defined as the distance from a known reference co-ordinate system to a point in the scene being examined. A laser sensor provides range image that gives direct three-dimensional information about a scene that is unattainable by normal imagery.

1.1 Motivation The concept of the generic sensor brick architecture evolved with the objective of incorporating modularity and generality in the sensor technology. This will make the system robust, compact and autonomous thus extending its capabilities. One of the primary goals for devising such a brick is to incorporate it as a plug and play sensor in a robot, which can help it to make it autonomous depending upon the sensing camera in use. Vision camera can be used to obtain the visual image of the scene of interest. Thermal camera on the other hand gives information about the temperature and distribution of heat in an object irrespective of illumination. Therefore, thermal camera can be employed in dark when the light is absent. Laser range scanner gives the direct 3D 1

information about the objects or scene, which is not possible by other forms of imagery. It provides information about the depth of the scene and hence can extensively be used for navigation of the robot without any collision with the obstacles in the path. The data acquired by the sensor can be sent in a raw format or in preprocessed form to the central server or remote host for further processing with reference to which it can take appropriate decisions. Apart from navigation, the range scanner can also help in visualizing objects in 3 dimensions which is extremely important in the area of reverse engineering and 3D computer vision. Another potential area of application of the range sensor brick is the under-vehicle scanning for security. Under-vehicle scanning poses serious challenges especially under the condition of low illumination and difficulties in accessing the full surface under the vehicle primarily around the center region. The range sensor brick can simply be placed as a plug and play device in a low level tracked vehicle robot as shown in Figure 1.1 and maneuvered under the vehicle to take the scans of the under-vehicle scene. These scans can be displayed in real time on the screen to verify the presence of the possible threat objects under the vehicle.

Figure 1.1: Range sensor brick placed on the low-platform track wheeled under-vehicle robot. The laser scanner that is employed for the brick is the Sick LMS 200 manufactured by Sick Inc. It is a non-contact measurement unit that scans the surroundings twodimensionally. As a scanning system, the device requires neither reflectors nor position marks. It can be used for area monitoring, object detection and measurement and determining positions. The generic sensor brick architecture is shown in Figure 1.2. The idea is to make the unit robust, compact, modular and independent. The unit only needs to be powered on and the operation can be done remotely via wireless connection. The laser sensor brick comprises four functional units in the form of blocks. If a unit needs to be replaced for some reasons, the replacement can be done reasonably easily due to the modularity in the design architecture of the brick. This allows the luxury of being able to use the brick in difficult environment and abnormal situations where the brick needs to be operated 2

continuously without interruptions due to emergency repair, maintenance or malfunctioning.

Figure 1.2: Generic sensor brick architecture. The different blocks of the brick are: Acquisition Block: The main objective of this block is to acquire the object or scene and display the profile and range image of the scanned scene. LMS 200 scanner manufactured by the Sick Company is employed for the purpose. Preprocessing Block: Data captured by the acquisition block will be in raw format therefore preliminary processing is needed to be done to get the image or profile in the required form. Basic processing might involve noise removal, contrast enhancement, rotation, smoothing, edge detection and so on. Sometimes high level processing is required to be conducted on the raw data. This would include registration, fusion and 3-D modeling. ASUS P4GE-VM micro ATX board manufactured by ASUSTeK Computer Inc is used for the purpose. Communication Block: This block is responsible for communicating back and forth with the central control unit or remote host. The block can send and receive the range data or image in raw form or in the processed format to the remote host via a communication interface. For this purpose we have used wireless-G PCI card manufactured by Linksys. Power Block: This unit does the electrical activation of the brick. It is responsible for providing the electrical input to all other blocks depending upon the requirement of each block. A 12V Panasonic LC-RA1212P battery is used to fulfill the requirement of power.

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1.2 Application Over the past few years, range imagery has become one of the most important aspects of computer vision. Unlike images obtained from normal camera, an image obtained through range scanner gives direct 3D information about a region captured by the scanner therefore range images are useful in object modeling, creation of virtual environments, robot navigation and tool manipulation. The concept of modularity in the design of the sensor brick evolved from the idea of building an autonomous sensing unit that possesses a wide range of application. Some of the main applications of the range sensor brick are listed below:

1.2.1 Navigation One of the major forms of application of the range sensor brick would be to help in the navigation of the robot. Navigation is the process to make the robot to go where it should. The main purpose of navigation is to reach a target point from the given position avoiding all obstacles that come in the way through. For this the robot must know from where it starts, at what position it is during the motion, where the obstacles are; which is especially difficult when they are discovered during the motion and can move themselves; where the goal is; and when the goal is actually reached. Figure 1.3 shows an indoor-vehicle robot equipped with the LMS 200 Sick scanner and the range map of the indoor environment provided by the scanner.

(a)

(b)

Figure 1.3: (a) Indoor vehicle equipped with the Sick scanner, (b) map of an indoor environment generated using the Sick scanner (Taken from: www.acfr.usyd.edu.au).

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1.2.2 Under-vehicle Inspection The growing terrorist activities especially after the incident on the 11th of September, 2001 have presented serious challenges as far as the security of life and private property is concerned. One of the frightening terrorist activities has been vehicle bombs which kill many innocent lives and destroy valuable properties. Various attempts to detonate the threat objects are being made to overcome this security issue but the problem becomes more challenging in situations when the threat objects are concealed in the narrow and inaccessible corners and space under the vehicle and when the inspection has to be done in low illumination conditions. The Imaging, Robotics and Intelligent Systems (IRIS) laboratory at the University of Tennessee has devised a modular robotic platform in the form of a low-platform track wheeled under-vehicle robot to perform the under-vehicle scanning for the detection of the possible threat objects present under the vehicle. This eliminates the use of a traditional “mirror-on-a-stick”, shown in Figure 1.4 which is still under operation in many cases for the inspection of the under-vehicle for security. One of the main drawbacks of these traditional “mirror-on-a-stick” is that they can only reach the edges of the vehicle and cannot view the central inaccessible region of the under-vehicle where the threat objects are more likely to be kept. Another disadvantage is they cannot be operated effectively in the dark when the light is absent i.e. the method of inspection is illumination variant.

Figure 1.4: “Mirror -on-a-stick” for under-vehicle inspection (Taken from: www.lynnrobertsonline.com) The range sensor brick can be easily plugged into the low-level track wheeled undervehicle robot to perform the scanning. The robot can literally scan through the entire under-vehicle area and provide the real time image of the under-vehicle which can be used to detect the threat objects and explosive, if any. Figure 1.5 (a) shows the low-level track wheeled under-vehicle robot which can house the range sensor brick in the space between the mobility units along its two sides. Figure 1.5 (b) shows the robot along with the range sensor brick scanning along the vehicle for inspection. The under-vehicle robot is controlled by the joystick and it can traverse through the entire under-vehicle surface thus making it possible for the sensor brick housed on it to capture the image and send it to the remote controller.

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(a)

(b)

Figure 1.5: (a) Low–level track wheeled under-vehicle robot, (b) range sensor brick placed on the robotic platform performing the under-vehicle inspection.

1.2.3 Road Profiling and Terrain Mapping This is another potential area of application of the range sensor brick. Road authorities and road construction contractors around the world require accurate, periodic road surface condition data in order to manage their networks, and construction and rehabilitation projects. The topographical information about the road can be provided by the range scanner. The range sensor brick can be placed on the vehicle with the scanner facing down towards the road surface to acquire the profiles. Figure 1.6 shows how a range scanner can be mounted on the vehicle to take the profiles of the road.

Figure 1.6: Range scanner placed on the vehicle edge to scan the road (Taken from imaging.utk.edu/research/grinstead/projects.htm).

1.2.4 Reverse Engineering Another area of application of range imagery is reverse engineering. Reverse engineering is a process of replicating an object by capturing its physical dimension. It helps in generating the Computer-Aided Design (CAD) models of objects which can be used to duplicate an existing object. Reverse engineering holds a great scope in preserving the 6

cultural arts and sculptures, which are valuable assets of human culture. The range sensor brick can be used to perform the reverse engineering of objects of different geometry. Figure 1.7 (a) shows the visual image of a socket and the 3D range image of the same is shown in Figure 1.7 (b).

(a)

(b)

Figure 1.7: (a) Visual image of a socket, (b) 3D range image of the socket. Laser measurement systems are suitable for determining the volumes or contours of bulk materials or objects or the position of the objects. They can be employed for classifying the objects such as vehicle detection or object recognition. Several automated tasks such as process automation or area monitoring can be conducted with the aid of LMS sensors. The automated monitoring of buildings and open spaces for security can be achieved through these sensors. Three-dimensional scene visualization is a promising technology for automatic control, manufacturing and robotics. 3D laser range sensors can give direct geometric information of the environment. In [WulWag03], the writer makes a point that 3D scanning using 3D scanner such as those of Riegls does not fulfill the requirements of factory automation and robotics because of the heavy weight and more cost. This problem can be overcome by the use of 2D scanners. 2D scanners can be employed along with a mechanical actuator (servo drive) to reach the third dimension. This is indeed one of the fast 3D scanning methods that have been employed in 3D range imagery.

1.3 Document Organization The remainder of this document features the designing, building and implementation of the range sensor brick with under-vehicle inspection as a primary focus of application of the brick. Chapter 2 presents the hardware architecture of the brick where we explain about the technical characteristics of different components that we selected for the brick. It features the physical architecture of the brick including the electrical and mechanical characteristics of different components. Chapter 3 deals with the software architecture of the range sensor brick. It explains about the communication aspect between the Sick scanner and the host computer and the designing of GUI for acquisition. The results of under-vehicle scanning have been documented in the fourth chapter. Finally, we conclude with closing remarks and future works in the last two chapters. 7

2 Hardware Architecture In this section, we will discuss about the overall sensor hardware architecture with focus on each component. As discussed earlier, the brick comprises four main blocks namely, acquisition block, preprocessing block, communication block and the power block. The general sensor brick architecture and its various components are depicted in Figure 2.1. COMMUNICATION BLOCK

PREPROCESSING BLOCK

P

ACQUISITION BLOCK

R S

C Linksys Wireless-G PCI Card

I

ASUS-P4GE-VM Micro ATX Board (244mm × 219mm)

4 2 2

LMS-200 Sick Sensor (210L×156W×155D mm3)

POWER BLOCK

Panasonic LC-RA1212P 12V Lead Acid Battery (151L×98D×94W mm3)

Figure 2.1: Range sensor brick architecture and its components.

2.1 Acquisition Block The main purpose of this block is to acquire the scene or objects. LMS 200, Laser Measurement System shown in Figure 2.2 is employed as a scanner for this component of the brick. This scanner is manufactured by a German company called Sick.

Figure 2.2: Sick LMS 200 scanner. 8

The LMS 200 is a non-contact Laser Measurement System that works under the principle of pulsed time-of-flight [Sic02]. It is an active scanning system that scans the surroundings and objects two dimensionally without the need of passive components such as reflectors or position markers. The pulsed laser beam is deflected by an internal rotating mirror so that a fan shaped scan is made of the surrounding area and the shape of the object is determined by the sequence of impulses received. The scanner provides a distance value every 0.25°, 0.5° or 1° per individual impulse, depending on angular resolution of the scanner. As a result of the beam geometry and the diameter of the individual spots, the spots overlap on the target object or up to a certain distance. Figure 2.3 shows spot spacing in relation to the range and the corresponding spacing diameter.

Figure 2.3: Spot Sizes/Spot Spacing (Taken from [Sic02]). The scanner has a maximum range capacity of 80 m. although ideally it is suited for a 60 m. distance. It has a variable data transfer rate with four options: 9.6, 19.2, 38.4 and 500 K baud. It can be connected with the processing board via RS 422 serial interface card. The real time measurement data scanned by the device is given out in binary format via the serial interface. The LMS 200 Sick sensor operates under the principle of pulsed time-of-flight. As shown in Figure 2.4, time taken by a pulse of laser beam to travel from the scanner to the target point and back is measured to determine the range or depth of the target point from the source. Figure 2.5 depicts how the principle of time-of-flight works.

Figure 2.4: Operating principle of Sick LMS 200 (Taken from [Hai3]). 9

Figure 2.5: Principle of the time-of-flight. A coded pulse of laser beam is emanated by a semiconductor laser diode which when strikes the object’s surface is reflected back and then registered by the scanner’s receiver diode. The time taken by the pulse beam to get transmitted from the transmitter diode, reflected off the scene’s surface and then received by the receiver diode is measured by the time measurement unit. The distance of the point on the scene from the laser diode is measured using the distance formula d=c×t/2, where c is the speed of light (3×108 m/s) and t is the total time taken. The resulting range values are calculated by the processor and the corresponding digital values of the range are provided as the output of the measurement. Sick scanner data can be used for object measurement and determining position. The measurement data corresponds to the surrounding contour scanned by the device and is given out in binary format via RS 232/RS422 interface. This data when displayed in a GUI gives the co-ordinates of every point in the field of view. Therefore all the objects in the field of view, which reflect the laser beam, can be located with their position and size. In the binary format as the individual values are given in sequence, respective angular position can be allocated on the basis of the position of the values in the data string. Some of the applications where in this sensor can be employed are area monitoring, object measurement and detection and determining position. With this sensor, measurement data is available in real time and can be processed for further applications. It can scan at a very fast rate thus the measuring object can move at high speeds. The LMS scanner is basically suited for indoor operation although it can also be employed for outdoor operations such as detecting objects within its range capacity. Table 2.1 shows the technical specification of the Sick LMS 200 scanner. Detail specification of the same along with the dimensional drawing can be found in [Sic02].

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Technical Specifications General: Sensor Type Range Resolution Angular resolution Response Time Electrical: Laser Class Data Interface Transfer Rate Power Supply Power Consumption

Pulsed time of flight Max. 80 meters 10 mm 1°/0.5°/0.25° 13/26/53 ms I

RS 232/RS 422 9.6/19.2/38.4/500KBaud 24 V DC +/- 15% 20 W (without output load) plus heating with approx. 140 W Operating ambient Temperature 0° C to +50° C Storage Temperature -30° C to +70°C Mechanical: Weight 4.5 Kg Dimension (L×W×H)

210mm×156mm×155 mm

Table 2.1: Major specifications of the LMS 200 Sick scanner (Taken from [Sic02]).

2.2 Preprocessing Block After acquisition, the block that comes into operation is the preprocessing block. The range data acquired by the acquisition block is in a binary format. The data needs to be manipulated so as to obtain the range profile and then the corresponding range image. The main purpose of this block is to carry out basic low level processing or preliminary processing that is needed to be done on the raw range image. Preliminary processing involves general techniques for filtering for noise removal, rotation of the image, smoothing, and sharpening, zooming, cropping and edge detection. At times, the block might need to perform high level processing tasks such as matching profiles, registration and 3D scene reconstruction. Most of these high level techniques of processing are expected to be done at the central remote host, however, the sensor preprocessing block is supposed to be capable enough to perform these operations as well at times as far as maintaining the modularity of the overall system is concerned. In general, this block is meant for processing, storing and transmitting the acquired images. The board which we have selected for the brick is ASUS P4GE-VM micro ATX board manufactured by ASUSTeK Computer Inc. It supports a Pentium IV processor and has three PCI expansion slots. One slot is used for placing the RS 422 interface card that connects the scanner with the board. Another slot is used for the communication interface with the remote host. It has two 184 pins DIMM sockets for RAM. The dimension of this board is 9.6” × 8.6” (244mm × 219mm) which is reasonable as far as the idea of 11

making the brick compact is concerned. Figure 2.6 shows a picture of the ASUS P4GEVM board.

Figure 2.6: Mother-board (ASUS P4GE-VM) for preprocessing. Several other components need to be connected to this board to operate it as a fully functional processing block. A Central Processing Unit (CPU) is required to process and execute the instructions that are sent to it for processing. A hard disk drive is needed to store the range values and the range images of the acquired scenes and a Random Access Memory (RAM) is used for temporary storage for executing the data. A brief description of each of these components is given below. Processor: The processor that we have used for processing is Intel Pentium IV, 2.4 GHz, with a 512 K cache and 533 MHz Front Side Bus. Hard Disk Drive: 15.3 GB hard drive manufactured by Fujitsu is used. It has a fast access time of 9.5ms with 37.8 MB/sec media transfer rates. It has an UDMA 66 interface with a cache buffer of 512 KB. Detail specification is given in [Fuj03] RAM: The memory we used for the processing block is KVR333X64C25/512 manufactured by Kingston Technology. It is 512MB, 333MHz 184 Pin SD RAM-DDR. Detail specifications and description of the same is given in [Kin04].

12

Major technical specification of the Asus P4GE-VM board is shown in Table 2.2. A detail specification of the board can be found in [Asu04].

Technical Specifications Processor Cache Chipset Front Side Bus Memory

Expansion Slots Special Features

Socket 478 for Intel Pentium 4/ Celeron upto 3.06Ghz+ On-die 512KB/256KB L2 cache Intel 82845GE GMCH 533/400MHz 2×184-pin DIMM sockets support maximum 2GB PC2700/PC2100 (FSB533) or PC2100/PC1600 (FSB400) non-ECC DDR SDRAM memory 1× AGP, 3× PCI Power loss Restart Crash-Free BIOS

Back Panel 1× Parallel I/O Ports 1× Serial 1× PS/2 Keyboard 1× PS/2 Mouse 1× Audio I/O 4× USB 2.0 1× RJ45 20 Pin ATX Power Connectors Internal I/O 4 Pin ATX 12V Power Connector Connectors COM2 Connector 2MB Flash ROM, AwardR BIOS BIOS Dimension 9.6” × 8.6” (244mm × 219mm) Table 2.2: Major specifications of the ASUS P4GE-VM board (Taken from [Asu04]).

2.3 Communication Block After preprocessing, the processed data have to be sent to the remote host for further processing or decision-making. The communication block of the sensor brick is responsible for transferring the data back and forth between the sensor and the central unit. We selected wireless-G PCI card manufactured by Linksys for the communication purpose. It is an IEEE 802.11g card which works at a great data transfer rate of 54 Mbps. It is five times faster than 802.11b, another class of IEEE 802.11 wireless LAN standard. It also has a good range (about 100-150 feet) compared to 25-75 feet of 802.11a. The card is also relatively inexpensive compared to other classes of IEEE 802.11 standard.

13

A comparative study of all the classes of IEEE 802.11 wireless LAN standard is shown in Table 2.3. This justifies our selection of the wireless ‘g’ standard for the application. Wireless Standard

802.11b

802.11a

802.11g

Speed

Up to 11 Mbps.

Up to 54 Mbps. Five times greater than 802.11b.

Up to 54 Mbps. Five times greater than 802.11b.

Frequency

Uses a more crowded 2.4 GHz band. Might interfere with the devices like cordless phone and microwave which use the same 2.4 GHz band frequency.

Uses uncrowded 5.7 GHz band therefore can remain with 2.4 GHz networks without interference.

Uses the 2.4 GHz band as 802.11b.

Range

Good range. Typically 100-150 feet indoors depending on construction, building material and room layout. Compatible with 802.11 g.

Shorter Range (2575 feet) indoors due to higher frequency band.

Good range. 100150 feet. Same as 802.11b.

Incompatible with both 802.11b and 802.11 g.

Inexpensive.

Relatively more expensive.

Backward compatible with 802.11b. Incompatible with 802.11a. Relatively inexpensive.

Compatibility

Relative Cost

Table 2.3: Comparison between different members of IEEE 802.11 wireless technologies. Figure 2.7 shows the card and its specification can be found in [Lin04].

14

Figure 2.7: Linksys wireless-G PCI card for communication.

2.4 Power Block The power block is responsible for electrically activating all the components of the brick. This block supplies electrical power to each component so that a continuous operation could be maintained. The best estimate of the power requirement for the sensor brick can be made only after the calculation of the power demand of each component in the brick is done precisely. Therefore analysis is needed to be done for each component to know the amount of electrical energy it needs for functioning. The LMS 200 Sick scanner operates at 24 V DC (+/- 15%) and it consumes 20W power without output load. Therefore it would be taking approximately 1 A. of current while in operation. We assume that it takes roughly 2 A. for the sake of safety. VI-LJ03CY 12V-to-24 V, DC-to DC converter manufactured by Vicor is used to provide isolated supply for the sensor. The ASUS P4GE-VM motherboard used for processing is powered up by the PW200-V dc-to-dc converter that takes 10A at 12V during full load under normal condition. The Linksys Wireless-G PCI communication card is placed in the PCI slot of the board and therefore the board itself powers it. On an average, the brick will need around 12A at 12 Volt. Panasonic LC-RA1212P 12 Volt Lead Acid Battery is employed to power the whole system. Therefore following are the different components that comprise the power block of the sensor brick: 1) 2) 3)

PW-200 12V-to-12V, dc-to-dc converter VI-LJ03-CY 12V-to-24 V, dc-to-dc converter Panasonic LC-RA1212P 12 Volt Lead Acid Battery

The overall architecture of the power block is as shown in Figure 2.8.

15

PREPROCESSING BLOCK

ACQUISITION BLOCK

ASUS-P4GE-VM Micro ATX Board

LMS-200 Sick Sensor

PW-200-V dc-to-dc VI-LJ03-CY dc-to-dc Converter (12V-24V)

Converter (12V Input) (12V-12V)

Panasonic Lead-Acid 12 V Battery, LC-RA1212P 12 Ah @ 20 Hr Rate

Figure 2.8: Power block architecture.

16

2.4.1 PW-200-V (12V), DC-to-DC Converter The PW-200-V is a small yet powerful and fully compliant power supply designed to power a wide variety of standard PCs from a single 12 V power source. The PW-200-V is the only 12V dc-to-dc cable less mini-ITX power supply solution [Pw204]. Compatible with an entire range of mini-ITX motherboards as well as regular boards, the PW-200-V provides cool, silent power for the system. The PW-200-V has many advantages over a regular power supply: - 100% silent operation - Low heat dissipation with efficiency over 95% - Low RFI/RMI and low ripple noise. - Plugs directly into the motherboard’s power connector, i.e. no cable mess. - Long life (Mean time between Failure, MTBF rated at >200,000 hours) Table 2.4 shows the electrical specifications for the PW-200-V converter. Power Ratings (Maximum Power = 205 Watts) Nominal Voltage (DC)

Load Current

Regulation (%)

Max Load (A)

Peak Load (A)

5V

6A

10 A

+/- 3

5 VSB

2A

10 A

+/- 3

3.3 V

6A

10 A

+/- 3

-12 V

0.1A

0.2 A

+/- 5

+12 V

12A

13.5 A

N/A

Table 2.4: Electrical specifications for PW-200-V (Taken from [Pw204]). Some of the important features of the PW-200-V converters are: Size: 155mm (L) ×23mm (W) ×30mm (H) Overload Protection: Overload Protection will be affected when either of the loads, +5V and +3.3V exceeds greater than 200% of the maximum Load. Turn-on Delay: After turning on, at least 20 ms will be needed for the rise of +5V output voltage (measured from 10% to 95%) to reach its peak. Remote ON/OFF Control: Logic level is LOW – Output voltage is enabled. Logic level is HIGH – Output voltage is disabled. Operating Environment: Temperature: 0 to 80 degree centigrade. 17

Relative Humidity: 10 to 90 percent, non-condensing. Altitude: 60,000 ft. Efficiency: Greater than 95% at full load. Shipping and Storage: Temperature -40 to +90 degree centigrade Relative Humidity: 5 to 95 percent, non-condensing. MTBF: 200,000 hours Figure 2.9 shows the picture of the PW-200-V DC-DC converter.

Figure 2.9: PW-200-V DC-DC converter.

2.4.2 VI-LJ03-CY 12V-to-24 V, DC-to-DC Converter This is a MegaMod family 25W to 50W (12V to 24V) dc-to-dc converter manufactured by Vicor. Vicor’s Mega Module and Mega Module Jr. families of single, dual and triple output DC-DC converters provide cost effective, high performance, off-the-shelf solutions to applications that might otherwise require a custom supply [Vic04]. Totally isolated outputs eliminate efficiency penalties and output interaction problems. The VILJ03-CY operates at –25°C to +100°C. It has the dimension of 4.9×2.5× 0.62 in. Figure 2.10 shows a picture of the converter.

Figure 2.10: VI-LJ03-CY dc-to-dc converter.

18

2.4.3 Panasonic LC-RA1212P, Lead-Acid 12V Battery The DC power supply to the PW-200-V 12V-to-12V dc-to-dc converter and VI-LJ03-CY 12V-to-24 V dc-to-dc converter is provided by the 12 V Panasonic LC-RA1212P lead acid battery as shown in Figure 2.11.

Figure 2.11: Panasonic LC-RA1212P lead acid battery. Panasonic’s tough Valve Regulated Lead Acid rechargeable batteries are designed to provide outstanding performance in withstanding overcharge, over discharge, and resisting vibration and shock [Pan04]. Compact, these batteries save installation space, while providing full and reliable power. The use of special sealing epoxies, tongue and groove case and cover construction, and long-sealing paths for posts and connectors, assures that the Valve Regulated Lead Acid battery will offer exceptional leak resistance, and allows them to be used in any position. Some of the important features of this battery are listed below: • High quality and reliability • Exceptional Deep Discharge recovery • No corrosive gas generation • Long service life • Quick Chargeability • High Power Density • Maintenance free operation Table 2.5 shows the major specifications and Table 2.6 lists the major characteristics of the battery. 12V Nominal Voltage 12Ah Rated Capacity (20 hour rate) 5.945 inches(151.0 mm) Length 3.860 inches (98.0 mm) Width Dimensions 3.702 inches (94.0 mm) Height 3.937 inches (100.0 mm) Total Height 8.36 lbs (3.8 kg) Approx. mass Table 2.5: Panasonic LC-RA1212P lead acid battery product specification (Courtesy: [Pan04]).

19

20 hour rate (600mA) 10 hour rate (1130mA) 5 hour rate (2080mA) 1 hour rate (8100mA) 1.5 hour rate discharge Cut-off voltage 10.5V Fully charged battery Internal Resistance 77°F(25°C) 104°F (40°C) Temperature dependency of capacity 77°F (25°C) (20 hour rate) 32°F (0°C) 5°F (-15°C) Residual capacity after standing Self discharge 3 months 77°F(25°C) Residual capacity after standing 6 months Residual capacity after standing 12 months Charge Cycle Use Initial Current Method (Repeating Control Voltage (Constant use) Voltage) Tickle use Initial Current

12 Ah 11.3 Ah 10.4 Ah 8.1 Ah 5.8A

Capacity 77°F (25°C)

Control Voltage

Approx. 30 mΩ 102% 100% 85% 65% 91% 82% 64% 4.8 A or smaller 14.5V to 14.9V (per 12V cell 25°C) 1.8 A or smaller 13.6V to 13.8V (per 12V cell 25°C)

Table 2.6: Panasonic LC-RA1212P lead acid battery characteristics (Courtesy: [Pan04]).

2.5 Physical Layout of the Brick In this section, we shall discuss about the electrical and mechanical design and fabrication of the range sensor brick. After selection of all the components for the brick, we needed to design the physical layout of the brick so that packaging of all the components into one single unit could be done. After building a one piece range sensor brick, we could operate the brick as an autonomous and an independent unit. The criteria for the instrumentation and packaging were as follows: 1) The range sensor brick should be packaged into one unit without any externals. 2) It should use a single battery. 3) It should be air resistant and robust enough to withstand minor vibrations and fall. 4) It should be modular enough so that the components can be replaced with reasonable ease. 20

5)

Since the brick is to be used for the under-vehicle inspection, the height of the brick should be as small as possible. Figure 2.12 shows the isometric view of the first layout that we came up with.

Figure 2.12: Isometric view of the first physical layout. The brick consists of four main units all connected together to form a single compact laser sensor brick. In Figure 2.12, the blue unit is the one for the Sick sensor. The sensor will be packaged vertically with its front face in front of the brick. The part of the sensor comprising the scanning mirror will be outside of the brick as can be marked by the front protuberance in the figure. The green unit represents the block for processing and communication. It is just behind the sensor and above the power and hard disk drive units as shown in Figure 2.12. The block is a rectangular cube with dimension 260×255×170 mm3. The communication block is not actually a separate unit but just a card which fits in the slot of the board therefore it comes in the same unit for processing. Underneath the processing block are the power unit and the unit for the hard disk and Vicor dc-dc converter. The power unit is denoted by red color in Figure 2.12 and will comprise the battery. Its dimension is 255×144×100 mm3. Another unit shown by the brown color will comprise hard disk and the Vicor dc-dc converter for the sensor. It measures 255×116×100 mm3. 21

The first layout could not meet all the design criteria we suggested in the beginning so we decided not to implement it. With the objective of under-vehicle scanning in the mindset, another design was devised. We decided to mount all the components of the brick on an aluminum sheet and then enclose the sheet by an external box of suitable dimensions. The top cover of the box will house the scanner. We therefore needed to draw the layout of the inner aluminum sheet, outer box and the top cover. We first drew the layout of the inner aluminum sheet which is shown in Figure 2.13. The layout shows the detail information with the positions of holes for the screws to house the components of the brick. It also shows the positions of different components of the brick. This layout is a top view of the sheet and it measures 19”×15” in dimension. Figure 2.14 shows the top view, side views and the isometric view of the outer frame that encloses the different components of the brick mounted on the aluminum sheet.

Figure 2.13: Top view of the aluminum sheet which houses all the components of the brick.

22

Figure 2.14: Different views of the outer box which encloses the aluminum sheet with the components of the brick.

Figure 2.15: (a) Top view of the sheet for the cover at the top, (b) Top view of the sheet for making the box. A 29×33 piece of sheet metal is cut and 6”×5 5/8” piece is stripped off from each corner. The sides are then bent to form the box as shown in the Figure 2.14. 23

Figure 2.15 (a) shows the top view of the cover plate for closing the box at the top. This cover box will house the Sick scanner facing upwards. The dimension of this cover is 21 1/8” × 17 1/8” with a small edge of width 3/8” all around the sheet. Figure 2.15 (b) shows the sheet for the box. To make the box, first a sheet of dimension 29”×33” is cut then a small piece 6” × 5 5/8” is stripped off from each corner. The projections along the sides are then bent along the dotted lines to form a box measuring 21”×17”× 6”. The layout for the top cover for the box is shown in Figure 2.16. This cover measures 17 1/8” × 21 1/8” and it will house the Sick scanner at the top. The Sick scanner will be held in with 8 bolts in total four on each side of the scanner with two on the scanner side and two into the cover.

Figure 2.16: Top View of the cover for the box which houses the Sick scanner.

2.6 Electrical Circuit and Power Distribution Diagrams The next stage was to draw the electrical circuit diagram of the brick showing the electrical connection of all the components. Figure 2.17 shows the electrical connection of the different components of the brick. As can be seen, the source of electricity for the brick is the single 12V battery. This battery supplies two channels of the brick. The first channel is that of the scanner which is fed through the Vicor 12V-24V Dc-Dc converter and the other channel is that of the board in which the power is supplied via PW-200-V 24

converter. Each channel has a separate on/off switch and fuse for safety. The fuse rating for the first channel is 7A and that for the second channel is 18A.

Figure 2.17: Electrical circuit diagram of the range sensor brick. The power distribution of the brick is shown in Figure 2.18. The system is fed by the 12V, 12Ah battery which produces a total of 144W. The battery feeds the PW-200 converter and Vicor 12V-24V converter. The PW-200-V converter gives a 200W output at most whereas the Vicor converter takes a 75W input and supplies a 50W to the output channel. The output from the PW-200-V converter is taken by the Asus motherboard which takes about 100-120W input and the output from the Vicor converter is fed to the Sick scanner which takes an input of 20W. 25

Figure 2.18: Power distribution diagram of the range sensor brick.

2.7 Bill of Materials The bill of materials is a list of different components of the brick, their quantities and price. We have tried to list all the materials as precisely as possible, however, the exact number of components like screws, nuts and bolts might vary later when the brick is ready as a finished product. As can be seen from the Table 2.7, the most expensive component of the brick is the scanner itself which costs around 5000 USD. The system including the board, processor, RAM, hard disk and the Linksys 802.11g communication card makes second most expensive component in the list with the price approximately equal to 506 USD. No. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.

Parts Description Sick LMS 200 Range Sensor Asus P4GE-VM Micro ATX Board 15 GB Maxtor HDD KVR333X64C25/512, 512MB, 333MHz 184 Pin SD RAM-DDR Intel Pentium IV, 2.4 GHz Processor Linksys Wireless-G PCI Card RS-422 Qualtech PCI Card Vicor (12V/24 V) DC-DC Converter PW-200 (12V/12V) DC-DC Converter Panasonic LCRA1212P 12V Lead Acid Battery In-line fuse 4A 26

Qty. 1 1 1 1

Price ($) 5000 105 115 91

1 1 1 1 1 1 1

125 70 100 115 50 60 5

13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25.

On/Off Switch LED indicator 6-32×1” thru screws 6-32×1 ½” thru screws 8-32×20 mm Hex Bolts 10-24×1” thru screws 10-24×¾” thru screws ¼” OD×½” SCR #6 RD Unthreaded Spacer ¼” OD×¾” SCR #6 RD Unthreaded Spacer ¼” OD×1” SCR #6 RD Unthreaded Spacer 15” ×19” Aluminum Sheet 17.5” ×21.5” Sheet 30” ×34” Sheet

2 2 10 2 8 4 4 6 4 4 1 1 1

16 5 3 2 3 2 2 2 2 2 30 100 150

Table 2.7: Bill of materials for the range sensor brick.

2.8 Brick Models In this sub-section, we will see different models of the range sensor brick that we came up with. Model I: To start with, we decided to build a wooden box because we thought that wood would be easier to work on. We hoped that this would also give us sufficient knowledge about building the box before the final piece is out. Figure 2.19 shows the front view and the isometric view of the wooden box that we devised. We packaged all the components but the scanner in the CPU casing by replacing the SMPS of the CPU with the DC battery. The scanner was placed on the side of the casing as shown. This brick measures 26”×19”×6”.

(a)

(b)

Figure 2.19: (a) Front view of the first model of the brick made of wooden box, (b) Isometric view. 27

Model II: Secondly, we tried to use the CPU casing for packaging different components of the brick. The SMPS of the CPU was replaced with the battery and the converters were also placed in the casing as shown in Figure 2.20. The unit was enclosed by the CPU casing cover which housed the Sick scanner. The scanner was fixed on the cover by drilling holes and tightening through bolts underneath the scanner as shown in Figure 2.21.

(a)

(b)

Figure 2.20: (a) Top view of the second model of the brick circuitries using the CPU casing, (b) Front view.

(a)

(b)

Figure 2.21: (a) Top view of the second model of the brick using the CPU casing for packaging, (b) Front view. Model III: This is the final model for the first prototype of the brick. As we suggested earlier in the design layout section, an aluminum sheet was cut which measured 15”×19” and the holes for the screws are made at respective positions on the sheet for placing various components of the brick. The sheet is shown in Figure 2.22 (a). All the components of the brick except for the scanner were housed on this sheet as shown in Figure 2.23. The sheet with the components mounted was enclosed by the box shown in 28

Figure 2.22 (b). The scanner was housed in the cover for the box as shown in the layout Figure 2.16.

(a)

(b)

Figure 2.22: (a) Top view of the aluminum sheet which houses the components, (b) Front view of the box which encloses the aluminum sheet.

(a)

(b)

Figure 2.23: (a) Front view of the brick components housed on the aluminum sheet, (b) Isometric view.

(a)

(b)

Figure 2.24: (a) Front view of the range sensor brick (first prototype), (b) Isometric view. 29

The sheet on which all the brick components are housed is enclosed by the outer box and the top cover. The top cover houses the Sick scanner. After all the components are integrated, the final product of the first prototype is completed. Figure 2.24 shows the different views of the range sensor brick.

(a)

(b)

Figure 2.25: (a) Side view of the brick showing the switch that controls the operation of the processing board, (b) Side view of the brick showing the switch to control the operation of the Sick scanner. Figure 2.25 shows the side views of the brick. On one side of the brick, there is a switch with the LED indicators to control the turning on and off of the processing board of the brick. On the other side of it, the switch to control the powering up of the Sick scanner is located. The Sick scanner needs to be powered on only when the processing board is on and reset after a complete single scan is performed, therefore, it needs to be controlled by a separate switch. Figure 2.26 shows the range sensor brick placed on the robotic platform to perform the scanning.

(a)

(b)

Figure 2.26: (a) Front view of the range sensor brick on the track wheeled robotic platform, (b) Isometric view. 30

3 Software Architecture After hardware architecture, we now look into the software aspect of the range sensor brick. The main software that is needed for the brick operation is that for the acquisition. The Sick Company does provide software for acquisition which displays the profile in real time but it does not have the provision for saving the acquired image and is not suited for our application as well. Also the modification of the software is not possible as they only provide the executables and not the source code. This leaves us with the option of writing our own program which would be user-interactive allowing us to see the range profiles in real time and at the same time has options to save the acquired range values so that further processing of the images for analysis is possible. The data measured by the Sick scanner corresponds to the surrounding contours scanned by the device and are given out in binary format via the RS 232/RS 422 interface. As the individual values are given in sequence, corresponding angular positions can be allocated on the basis of the position of the values in the data string. Fundamentally, the distance value per individual impulse (spot) is evaluated meaning that a distance value is provided every 0.25°, 0.5° and 1°, depending on the angular resolution of the scanner. The relation between the angular resolution and maximum number of measured values is shown in Table 3.1 below:

Table 3.1: Relations beween angular resolution and maximum number of range values (Courtesy: [Hai03]).

3.1 Communication Interface between Sick and the Host Computer When selecting the appropriate equipment for the data communication application, it is important to examine both the application and the communication peripherals that must be incorporated into the system. First it is important to determine if the application uses a standalone PC or whether a networked solution is needed that will enable ports to be used across a LAN or WAN. The second step is to determine the ports available and the type of the expansion boards that the motherboard can best accommodate. Then, a decision 31

should be taken of which of those options will best meet the speed and versatility demanded by the application. Once an interface is selected, the next step is to look at the type of data communication adapter needed. The distance needed between the communication peripherals and the host computer as well as the data transfer speed required for the application to function properly must be considered. The LMS 200 Sick scanner offers two communication interfaces possibilities. RS 232 and RS 422. Both use serial communication method.

3.1.1 RS 232 RS 232 is a single-ended data transmission system, which means that it uses a single wire for data transmission as shown in Figure 3.1. Since useful communication is generally two way, a two-wire system is employed, one to transmit and one to receive. Signals are processed by determining whether they are positive or negative when compared with a ground. Because signals traveling this single wire are vulnerable to degradation, RS 232 systems are recommended for communication over short distances (up to 50 feet) and at relatively slow data rates (up to 20 kbps). However in practice, these limits can be exceeded.

Figure 3.1: Unbalanced single-wire (RS 232) and two-wire transmission (Courtesy: [Hai03]).

3.1.2 RS 422 The RS 422 protocol greatly expands the practical possibilities of the serial bus. It provides a mechanism by which serial data can be transmitted over great distances (to 40,000 feet) and at very high speeds (up to 10 Mbps). This is accomplished by splitting 32

each signal across two separate wires in opposite states, one inverted and one noninverted as shown in Figure 3.2. The difference in voltage between the two lines is compared by the receiver to determine the logical state of the signal. This wire configuration, called differential data transmission or balanced transmission, is well suited to noisy environments.

Figure 3.2: Balanced (RS 422) transmission (Courtesy: [Hai03]). Table 3.2 explains the difference between RS 232 and RS 422 Serial communication interfaces.

Table 3.2: Differences between RS232 and RS 422 (Courtesy: [Hai03]).

33

After taking into consideration the available interfaces on the LMS and the due advantages of RS 422 especially in offering much less noisy communication environment in addition to a very fast baud rate (limited in this rate to 500K baud), we decide to go with the LMS 422 serial interface between the Sick scanner and the processing board.

3.2 Communication Technique The communication technique between the LMS and the host computer is based on sending and receiving telegrams [LMS02]. Telegram: A telegram is defined as a written matter intended to be transmitted for delivery to the addressee. In the case of LMS, telegrams are the protocol packets of data exchanged between the LMS and the host computer to send orders, replies, distances etc. Run-up Period for LMS: The system (Computer) and LMS units are generally ready for communication when the ‘POWER-ON’ string is sent by the LMS. The run-up period depends on a variety of software- and hardware-related parameters and is at most 60 seconds. This period should be handled by the host computer's evaluation software by its waiting for the receipt of the POWER-ON message for at least this maximum run-up period. Address Decoding: LMS has the address 0 on delivery – also repaired and replacement devices. The devices answer with their individual address that corresponds, as standard, to the broadcast address 0. If the application requires no individual address it is not vitally necessary to check the address. The individual address has no effect on the functional behavior of devices. Byte Time Intervals: On transferring data packets from the LMS to the host, time periods of up to 14 ms between two bytes must be taken into account depending on the LMS variant. Transmission of Continuous Measured Values: The data flow may be interrupted by byte time intervals. Synchronization should at least take place at STX, and 08H address, and when possible length and command, to rule out any erroneous synchronizations. Change of Operating Mode: A change of operating mode can take up to 3 seconds and corresponding time considerations should take this into account. On changing to an operating mode with continuous data transmission, the transfer of data also takes place after an initial period of 2 – 4 seconds after the change has been confirmed, the period depending on the device in question. Transfer and Data Format: The baud rate of the LMS is variable and can be set as follows: · 500,000 Baud · 38,400 Baud · 19,200 Baud · 9,600 Baud. The standard baud rate after power has been switched on is 9,600 baud. However, the LMS can be configured in such a way that the baud rate defined by the user remains set after power has been switched on. 34

Data Byte Structure: A byte of data consists of 1 start bit, 8 data bits, a parity bit with even parity or without parity (depending on the variant) and 1 stop bit. Telegram Structure: Pre-defined telegrams are available for communication with the host computer via the serial interface of the LMS. Transfer is initiated by STX (02h). Data is transferred in INTEL data format, i.e. word transfer takes place with the lower address and the least significant byte first and then bytes of higher significance and higher address. LMS Telegram structure

Table 3.3 gives the description of the LMS addresses.

Table 3.3: LMS Addresses (Courtesy: [Hai03]).

35

Data (example for received data = B0H): 2 Byte + n x 2 Byte (Low, High) 100°; 1° =204 Byte Total = 204+8 = 212 Byte 100°; 0.5° =404 = 412 100°; 0.25° =804 = 812 180°; 1° =364 = 372 180°; 0.5° =724 = 734 180°; 0.25° =1444 = 1452 A byte of data consists of 1 start bit, 8 data bits, and a parity bit with even parity or without parity (depending on the variant) and 1 stop bit. Pre-defined telegrams are available for communication with the host computer via the serial interface of the LMS. Telegrams are hexadecimal codes, which change the response of either the computer or the Laser scanner when transferring data. Data is transferred in binary format. Transfer is initiated by STX (02h). ________________________________________________________________________ STX ADR LENL LENH CMD LMS No. MODE CRCL CRCH ________________________________________________________________________ 0x02 0x00 0x03 0x00 0x30 0x00 0x01 0x71 0x38 where, 0x02 is the start character for initiation of transmission 0x00 is the LMS address, which is the BROADCAST address 0x0003 is the length = 3, i.e. three data bytes follow 0x30 is the command for request for measured values 0x00 is the LMS number 0, i.e. the LMS currently active sends the measured values 0x01 is the mode for all 361 measured values of the current scan 0x3871 is the CRC 16 checksum. We give 02h/00h/02h/00h/20h/24h/34h/08h/ command to change the operating mode of LMS to send all measured values of the scans continuously. For this command we get the following response from LMS: 06h/02h/80h/03h/00h/A0h/00h/10h/16h/0Ah/ The scanner now sends the complete measured value in a continuous stream of data. The corresponding evaluation software, which is a C++ code, is capable of synchronizing itself to the start of the telegram. Command: B0h Number of measured value 361: (LOWBYTE) 69h (HIGHBYTE) 41h Measured values in mm: ADh/01h/9Bh/01h/... Status byte for LMS Type 6: 10h CRC16: E3h/1Bh/ When we give the telegram number B0 to the LMS we get a continuous stream of data. For every two bytes of data, which are useful to us, we have the following format: The number of measured values transmitted (2 Bytes) is laid down in bits 0 to 13. Bit 15 and bit 14 code for the unit of the measured values: 0 0 Unit = 1 cm 0 1 Unit = 1 mm (default setting) 1 0 Unit = 10 cm 36

Bit 13 Bit 12 0 0 1 1

0 - complete scan (Standard) 1 - Partial scan Bit 11 coding of number of partial scan: 0 measured values belong to partial scan X.00 1 measured values belong to partial scan X.25 0 measured values belong to partial scan X.50 1 measured values belong to partial scan X.75

The Sick LMS 200 scanner can operate at various speeds depending upon the type of the serial interface it is connected to for the communication. The scanner can operate at 9600, 14400, 19200, 38400 and 500,000 bps speeds. When a RS232 mode of communication is used, a maximum speed of only up to 19600 bps is possible. With RS422, a maximum of 500 Kbps speed of data communication can be achieved. The scanner always starts with the lowest speed of 9600 bps then once the communication link between the host computer and the Sick scanner via RS232 or RS422 port is established, higher speed can be achieved. Once the scanning is done, it has to be physically reset and again be restarted at 9600 bps speed to perform another scanning.

3.3 GUI Design After knowing the theory of how the LMS communicates with the host computer, the next step is to design the Graphical User Interface (GUI) for the software. Designing GUI is one of the most critical parts of the software. GUI is the interface through which the user interacts with the software. The GUI is needed to provide all the facilities that the application offers in a user interactive way and at the same time be user-friendly. We have coded the entire software for acquisition using Borland C++ Builder. This software has the option for both the range profile display as well as the image of the scanned scene in real time.

Steps of Operation We now look upon the various steps that are to be followed while using the range sensor brick software for acquisition. Figure 3.3 shows the GUI for the operation of the range sensor brick. As shown, it has the provision for displaying both the continuous line profiles and the range image in real time.

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Figure 3.3: GUI for the operation of the range sensor brick. Let’s go through each step of operation of the software in brief. 1) Turn on the brick system and when the system is on, open the GUI and select the port through which the scanner is connected to the board using the “Port” radio buttons. The GUI can be accessed either locally or from a remote host as per requirement. If the RS232 port is used then COM3 and COM4 represent the two common ports COM1 and COM2 respectively. COM3 and COM4 represent the two serial ports for the RS422 interface. The text box in the right as shown in Figure 3.4 displays a message “Port 2 Selected”.

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Step 1

Figure 3.4: Step 1- Selecting the COM port. 2) The second step is to select the baud rate through the “Select BaudRate” combo box control as shown in Figure 3.5. The speed is in default 9600 bps for the starting purpose.

Step 2

Figure 3.5: Step 2- Selecting the baud rate. 3) After selecting the COM port and the speed, the third step is to open the port for communication using the “Open” command button. The text box in the right displays a message “Port opened successfully” as shown in Figure 3.6. The “Open” command button will toggle with the “Close” command button. Turn the sensor on. Both red and yellow LED on the sensor will glow. Wait until only the green LED glows and red and yellow LED turns off indicating that the sensor is ready for scanning.

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Step 3

Figure 3.6: Step 3- Opening the port. 4) When the green LED glows, a response message stream will be displayed on the text box at the bottom of the window as shown in Figure 3.7. This indicates that the sensor has charged up and is ready for scanning.

Step 4

Figure 3.7: Step 4- Receiving the confirmation data. 5) Click on the “Config Mode” button to enter the configuration mode. This step is mandatory to change the baud rate of the scanner. The text box will generate a message “Entering Configuration Mode…” and then “…Okay” when it is done after few milliseconds as shown in Figure 3.8.

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Step 5

Figure 3.8: Step 5- Click on the “Config Mode” button to enter the configuration mode of the scanner. 6) After the configuration mode of the scanner is reached, the next step would be to click on the “Change Baud” button to change the baud rate to the maximum of 500 Kbps for RS422 or 19600 bps for RS232. A confirmation message is displayed in the text box as “Changing baud rate…” and then “…Okay” when it is done after few milliseconds as shown in Figure 3.9. Skip this step if the minimum speed of 9600 bps is sufficient.

Step 6

Figure 3.9: Step 6- Click on the “Change Baud” button to change the speed of the scanner. 7) Click on the “Get LMS Status” to ensure that the scanner has achieved the maximum baud rate configuration. A message will be generated in the text box at the lower left corner as shown in Figure 3.10. This is not a mandatory step. 41

Step 7

Figure 3.10: Step 7- Click on the “Get LMS Status” button to ensure the scanner has reached the maximum baud rate configuration. 8) Click on the “Get LMS Type” to see information about the scanner in the text box at the lower left as shown in Figure 3.11. Again this is not a mandatory step.

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Step 8

Figure 3.11: Step 8- Click on the “Get LMS Type” button. 9) Now the scanner is ready to scan at a maximum baud rate. Click “Continuous Scan” to start reading the scanned data. This will show the live profile in the range profile section and live image in the Range image section of the GUI as shown in Figure 3.12. The live profile shows both the vertical and the horizontal depths of the acquired scene in mm. The “Continuous Scan” button will toggle to “Stop” button.

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Step 9

Figure 3.12: Step 9- Click on the “Continuous Scan” button to start scanning. 10) After the scanning is completed, the “Stop” button (toggle of “Continuous Scan” button) can be clicked to stop the scanning. The software will display the total time for scanning and the speed of scanning in number of profiles per second in the upper right text box as shown in Figure 3.13.

Step 10

Figure 3.13: Step 10- Click on the “Stop” button to stop scanning. 11) “Profile Display” button can be clicked to see the scanned profiles offline when the scene has already been scanned and the “Image Display” button displays the range image from the stored file after the scene has been scanned. 44

(a)

(b)

Figure 3.14: (a) Real time continuous line profiles, (b) real time range image of the muffler section of the under-vehicle. Figure 3.14 (a) shows the 2D range map and Figure 3.14 (b) shows the range image of the muffler section under the vehicle as visualized by the GUI. The GUI was designed in Borland C++ Builder which uses its own library for compilation. To establish a common standard to make the communication between various units in the robotic platform possible, we decided to rewrite the code in Visual C++. We were able to open the com ports and establish communication channel through which the scanner can send the telegrams back and forth to and from the host computer. The GUI in Visual C++ is shown as in Figure 3.15.

Figure 3.15: GUI designed in Visual C++.NET (Showing range profiles).

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4 Data Collection with the Range Sensor Brick In this section, we would discuss about the under-vehicle scanning performed by the range sensor brick. Here, we used the low-platform track wheeled under-vehicle robot incorporated with the range sensor brick to perform the scanning. The robot can literally be navigated by a joystick controller under the entire vehicle to take the scans. The brick can provide a real time range image of the under-vehicle region so any possible threat object present under the vehicle can be detected. This will help in providing a reliable mode of security as such scheme is far safer and reliable compared to the traditional “mirror-on-a-stick” method. Figure 4.1 (a) shows the range sensor brick placed on the low platform track-wheeled under-vehicle robot. The system is used to take the scanning of the under-vehicle as shown in Figure 4.1 (b). We used the Dodge RAM 3500 IRIS van for the scanning. The scanning is performed in three stages. First the van is jacked up to a certain height and the scanning is done along the length of the vehicle. Then in the second stage, the scanning is done along the width of the vehicle. Then an object is placed under the vehicle and the scanning is done again to see how effective the system is in detecting the threat object. These scanning are done by jacking the vehicles at different heights from the ground and even without jacking to see how the sensor brick performs under practical situation.

(a)

(b)

Figure 4.1: (a) Low-platform track wheeled under-vehicle robot with the range senor brick, (b) Dodge RAM 3500 IRIS van. Figure 4.2 (a) shows the visual images of the under-vehicle showing the muffler and the shaft whereas Figure 4.2 (b) shows the normal visual image of the catalytic converter. Figure 4.3 (a) shows the image of the differential and Figure 4.3 (b) shows the image of the muffler.

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(a)

(b)

Figure 4.2: (a) Visual image of the under-vehicle showing the muffler and the shaft, (b) Visual image of the catalytic converter.

(a)

(b)

Figure 4.3: (a) Visual image of the differential, (b) Visual image of the muffler. The major parts of the vehicle are the muffler, shaft, catalytic converter and the differential. Several other structures and the connecting pipes also run through the undervehicle. The van is 18 feet long and 6 feet wide.

4.1 Scanning along the Length of the Vehicle As the first part of data collection, we jacked the vehicle up from the ground to a height of 60 inches. The scanning was done along the length of the vehicle by moving it in the conveyor belt as shown in Figure 4.4 (a). Entire vehicle was covered in six frames.

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(a)

(b)

Figure 4.4: (a) Scanning along the length of the vehicle, (b) Scanning along the width of the vehicle. The images of the entire under-vehicle are shown below from Figure 4.5. Each image is 1200×900 pixels in resolution. While doing the visualization of the image, we take the reference point i.e. ‘0’ range at the lowest point of the vehicle from the ground which is 60 inches in the first case. Since the horizontal angle of vision of the scanner is 180° with the maximum depth of vision of 8000mm. and the scanner is literally on the ground level, it can view everything sideways. Therefore to ignore the scene outside the boundary of the vehicles, we have considered the range values within -2000mm. to +2000mm. instead of between -4000mm. to +4000mm.

(a)

(b)

(a) Color coded range image of the front part, (b) Range image of the front wheels.

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(c)

(d)

(c) Range image of the muffler, catalytic converter and the shaft, (d) Range image of the muffler section and rear wheels.

(e)

(f)

(e) Range image of the rear wheels, (f) Range image of the bumper. Figure 4.5: (a) through (f) - Range images of the under-vehicle obtained by scanning along the length of the vehicle with the van jacked up to a height of 60 inches from the ground. In the next stage, we jacked the van to a lesser height of 32 inches with the wheels at a height of 16 inches from the ground. The purpose was to see the difference in the images at different depths. As expected, the results were pretty much similar to the previous ones. The results are shown in Figure 4.6.

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(a)

(b)

(a) Color coded range image, (b) Grey-coded range image of the front wheels.

(c)

(d)

(c) Color coded image, (d) Grey-coded range image of the muffler section.

(e)

(f)

(e) Color coded image, (f) Grey-coded image of the catalytic converter section. 50

(g)

(h)

(g) Color coded range image, (h) grey-coded range image of rear wheels. Figure 4.6: (a) through (h) - Range images of the under-vehicle obtained by scanning along the length with the van jacked up to a height of 32” from the ground.

4.2 Scanning along the Width of the Vehicle In the second stage, the scanner is moved along the width of the van as shown in Figure 4.4 (b). Here, the van was jacked to the height of 49 inches from the ground level. The results are shown in Figure 4.7. The result shows that if we need to focus on one or two particular portions of the under-vehicle while scanning, the result seems to be better with the scanning done along the width of the vehicle.

(a)

(b)

(a) Color coded range image, (b) Grey coded range image of the rear part (spare wheel).

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(c)

(d)

(c) Color coded range image, (d) Grey-coded range image of the differential.

(e)

(f)

(e) Color coded range image, (f) grey coded range image of the muffler section. Figure 4.7: (a) through (f) - Range images of the under-vehicle obtained by scanning along the width of the vehicle with the van jacked up to a height of 49”.

4.3 Scanning with the threat object placed under the vehicle without jacking it up In the third step we took the normal scanning of the muffler region without jacking up the vehicle. The results are shown in Figure 4.8. Lastly, we tied a box made of paper at the muffler region and scanned the view again without jacking the vehicle up to see the reliability of the scanner in detecting the threat objects. Figure 4.9 shows the result of the scanning. The result clearly showed the presence of the external object. Comparing Figures 4.8 and 4.9 to figure out the presence and location of the threat object, we can 52

conclude that Figure 4.9 clearly indicates the presence of the external object under the vehicle.

(a)

(b)

Figure 4.8: (a) Color coded range image, (b) Grey-coded range image of the muffler section without jacking the vehicle up.

(a)

(b)

Figure 4.9: (a) Color coded range image, (b) Grey-coded range image of the muffler section with the threat object without jacking the vehicle up. The results obtained imply that the range sensor brick can be used effectively to scan the under-vehicle surface to check the threat and other external objects that might be concealed under the vehicle.

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5 Conclusions The objective of this project was to build a modular range sensor brick which could operate as an independent unit capable of providing information about the range or depth of the scanned object or scene continuously in real time. The sensor brick was expected to be highly modular, robust and compact so that it could be operated in any environment whether indoor or outdoor. Making it wireless and compact would help to use it as a plug and play sensor device which could be accessed remotely from a local or global host to exchange information between the host and the brick itself. Such a modular feature would be very useful to employ it in various areas of the robotics. Generic sensor brick architecture was devised comprising four different functioning blocks namely, acquisition block, preprocessing block, communication block and power block. The acquisition block is responsible for acquiring the data in the form of the range profiles or image of the scanned object. Basic preliminary operations are performed through the preprocessing block and the processed data is sent to the remote host or any other controller via communication block. The power block helps to make the brick independent and plug and play by electrically activating the brick. The task of building the range sensor brick was divided into two fundamental aspects, hardware architecture and the software architecture. A selection of suitable components for the different functioning blocks of the brick was done based upon the requirement and the objectives of the project. Next, the components were connected and packaged in a single box making it completely wireless, compact and robust. The software architecture of the brick dealt with coding the acquisition software to control the overall activity of data acquisition through the scanner. A GUI was developed which could show the range profiles and the range image of the acquired scene continuously in real time which was necessary as far as introducing autonomous capability in the robot is concerned. After coming up with the single, fully functional, robust and compact sensor brick, the next step was to test the brick in the real practical scenario. As mentioned in the first chapter, the brick was aimed for using in various applications. The range map provided by the range sensor is useful in planning the path for the robot for navigation which is one of the major fields of application. The process of replicating an existing object by capturing its physical dimension popularly known as reverse engineering is another field of application where the range sensor brick can be extensively used. Another major field of application is in digitizing the real world environment. Considering the alarming rate at which the terrorist activities is growing in the present world, security of the people and their property has become really important and challenging. Under-vehicle inspection for threat detection is one area where we thought the brick could be most useful in the present context. The final prototype of the brick for this project is aimed at fulfilling this particular objective. We used the brick itself to take the under-vehicle scanning with different conditions to test the reliability of the brick for the purpose. The result obtained verified that the brick is very effective and efficient in performing the under-vehicle inspection. In contrary to the traditional methods of inspection, this method of using the range sensor brick is reliable and scientific as brick placed on the robotic platform is capable of traversing along the entire under-vehicle 54

region and the scans of the surface are shown in real time on the screen of the remote controller.

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6 Future Work As mentioned previously, there are several other applications where the brick can be tested for suitability and adaptability. As a part of the future work, it may be tested for robot path planning to see whether the range map provided by the scanner is good enough to help the robot in navigation. The sick scanner is chiefly an indoor scanner but it can also be used for outdoor environment. It can also be tested for road profiling and terrain mapping to assess its efficiency in outdoor environment. The concept of modular robotics is an attempt to make the overall robotic system highly efficient by devising independent bricks for all the major functionalities of the robotic system. Mobility, sensing, intelligence, control and communication are the major areas for functioning of the robotic system and these will operate independently yet coherently in the form of bricks. Range sensor brick is a unit for sensing the three dimensional model of the object and it works independently although it is capable of communicating with the other bricks say mobility or control or intelligence bricks. The overall mode of communication between these bricks has to be common so that a meaningful job can be done. The integration between various units of the robotic system with common the communication module is necessary and this could be another future work of improvement.

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Bibliography [WulWag03]

[Hai03]

Oliver Wulf, Bernardo Wagner: Fast 3D Scanning Methods for Laser Measurements Systems. Institute of System Engineering, University of Hannover, Germany. Hasan Samih Haider: Laser Measurement and Positioning System. MS

Thesis Report, University of Applied Sciences, Offenburg, Germany, 2003. [Sic02]

LMS 200 / LMS 211 / LMS 220 / LMS 221 / LMS 291Laser Measurement Systems Manual (PDF-3.23 MB)

[LMS02]

LMS/LMI 400 Definition of telegrams between the user interface and LMS or LMI systems via RS 422/RS 232 Manual (PDF-400KB)

[Asu04]

ASUSTeK Motherboards’ Website

[Fuj03]]

Fujitsu Hard-Drive Manual (PDF-88 KB)

[Kin04]

Kingston, “SDRAM-DDR memory manufacturer’s Website”

[Lin04]

Wireless-G PCI network card from Linksys Website

[PW204]

PW-200-V dc-to-dc Converter Website

[Vic04]

VI-LJ030-CY dc-to-dc Converter Website

[Spr04]

Sick LMS Product Overview Manual (PDF-1.7 MB)

[Pan04]

Panasonic LC-RA1212P 12V Lead Acid Battery Product Specification (PDF-36 KB)

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Appendix A.1 Components and Typical Setup of LMS 200 Figure A.1 shows the components and typical setup for the LMS 200.

Figure A.1: LMS 200/ LMS 291 components and typical setup.

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A.2 Interface Plugs (Plug Modules) The interface plugs are built into plug modules. Figure A.2 shows the interface plug and the power supply plug of the Sick LMS 200.

Figure A.2: Scanner with Plug-in connection boxes.

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A.3 LMS 200/LMS 291 Electrical Connection Scanners require an operating voltage of 24 V DC ± 15% with a power consumption of 20 W plus the load on the three possible outputs OUT A (max. 250 mA.), OUT B (max. 250 mA.) and OUT C (max. 100 mA.). The restart input can be allocated as restart or for changing field. Power is supplied to the devices using a plug-in connection box with a high enclosure rating while interface connection takes place through another connection box (RS 232 or RS 422). Figure A.3 shows the electrical connection of LMS 200/LMS 291.

Figure A.3: Electrical connection.

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A.4 RS 232/RS 422 Conversion The prepared interface plug is converted to an RS 422 form using a standard bridge. The interface plug reverts to the RS 232 form on removal of the bridge. Bridging may only be carried out within the plug module. Figure A.4 depicts how the conversion can be made possible.

Figure A.4: Interface plug.

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Vita Santosh B. Katwal was born in Kathmandu, Nepal as the youngest son of Ram B. Katwal and Urmila Katwal. After completing his schooling from Gyanodaya Bal Batika, Secondary Boarding School in Kathmandu, he joined St. Xavier’s College, affiliated under the Tribhuvan University, Kathmandu where he completed his Intermediate degree in Science in 1995. In 1996, he joined the Institute of Engineering, Pulchowk campus affiliated by Tribhuvan University to complete Bachelors degree in Electrical Engineering. After graduation in 2000, he joined a private software company in Kathmandu and worked as a professional software developer for 2 years. He also worked as a program co-ordinator and lecturer of the engineering program in Pokhara University affiliated “Asian College of Engineering and Management” for 3 years. In fall 2003, he joined the University of Tennessee, Knoxville as a graduate Masters student in the Electrical and Computer Engineering Department. He worked as a Graduate Research Assistant in the Imaging, Robotics and Intelligent Systems (IRIS) Lab at the University of Tennessee where he completed his Masters of Science degree in Electrical Engineering in fall 2004.

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