Universal Navigation Algorithm Planning Platform for Unmanned Systems P. Leomar*, R. Sell* *Department of Mechatronics, Tallinn University of Technology, Ehitajate tee 5, 19086 Tallinn, Estonia
[email protected],
[email protected] Keywords: autonomous navigation, unmanned vehicle, robotics Abstract The paper deals with route planning and message exchange platform development for unmanned vehicle systems like Unmanned Ground Vehicle (UGV) and Unmanned Aerial Vehicle (UAV). Existing solutions for both types of vehicles are discussed and analyzed. Based on existing solution a unified concept is introduced. In this paper we introduce the study where the universal navigation algorithm planning platform is developed aiming to provide common platform for different unmanned mobile robotic systems. The platform is independent from the application and target software. The navigation and action planning activity is brought to the abstract layer and specific interfaces are used to produce the target specific code. Test platforms of this problem and cooperation scenarios are described. Introduction Unmanned mobile systems like UGV and UAV have been getting lot of focus in today’s world. Both types of vehicles are highly sophisticated robotic and mechatronic systems used nowadays widely in military conflicts but have been entered also into civilian sector. Unmanned vehicles (UV) are driven manually, in autonomous- or semi-autonomous regime. They can be controlled remotely by the operator, for example demining robot in rescue operations or ran by the on-board autonomous algorithm, for example surveillance unmanned plane or helicopter, detecting specific situation awareness. The autonomous regime needs the pre-defined algorithm which takes into account external sensor readings and internal calculations. In autonomous navigation the precise positioning and vehicle attitude are main input parameters from the sensors. The common navigation scenario is to reach certain waypoint and fulfill assigned mission or task in this position. At the present moment the navigation algorithm development is a device specific task in terms of technical point of view and has usually specific software or coding environment for this purpose. This brings us to the main lack of this kind of applications where every type of vehicle has its own system for algorithm development and action planning. This approach lacks of maturity in some cases as the platform development is time and resource dependent; lack of compatibility like systems used for UAVs do not comply the systems used for UGVs. There is very limited number of systems available which deals mainly with co-operational action planning where several unmanned systems from different categories are involved. Our development is aimed to solve these issues and offer open universal platform for common navigation and action planning. For the experiments and result validation two different unmanned system are used. The first test platform is UGV developed in Tallinn University of Technology. Autonomous vehicle is a prototype for the security purpose and can be used to guard a territory bounded by GPS coordinates. Robot is shown in Fig.1 a). Second test platform is a UAV developed by the Estonian company. Both systems had initially separately developed navigation planning systems but can now be integrated by using new solution.
The paper also discusses about the co-operation issues of unmanned vehicles, namely UAV and UGV. The tasks and problems in this domain are pointed out and benefits of using common platform explained.
a) Unmanned Ground Vehicle
b) Unmanned Aerial Vehicle Fig. 1 Test platforms
Unmanned vehicle navigation Unmanned Aerial Vehicle (UAV) In recent years, unmanned systems and UAVs in particular have become very popular, with estimates predicting a significant growth in the number of users. Nowadays different civilian applications like pollution monitoring, geophysical prospecting, and disaster monitoring and coast card services utilize benefits offered by use UAVs besides military applications. The widespread adopting of such devices has been till now delayed by mainly an accident rate higher than would be acceptable in the context of manned aircraft. However, the situation is now being improved by the development of automated take-off, landing and navigation systems that not only improve safety but also can eliminate the need for piloted operator. The phenomenal success of unmanned air vehicles during different operations is fostering a view that the days of the manned platform for intelligence, surveillance and monitoring duties are soon over. This booming progress can be attributed to the following reasons [1]: ● low cost compared to manned aircraft; ● low operating costs and a capability of operating from unprepared; ● rapid development of the most up-to-date information technologies; ● no risk of flight crew accidents. Currently more than 30 countries are developing and manufacturing up to 150 types of unmanned air vehicles. Moreover over 80 UAV types are in service with 55 world armies [2]. UAVs are developed and manufactured following many different design principles. Majority of UAV’s are developed and manufactured by Aerospace industry in different countries. Many of those UAV systems capable, at various levels, of autonomous flight are in operation worldwide, where the military market plays an important role determining progress trends in most cases still far. The facts played an important role initiating the interest of Estonian Defense Forces. A relevant interest in UAV’s has also been raised, in the last decade, in the academic community for following
reason. The UAV’s have been developed and constructed provide an excellent research platforms for objectively testing maturing technologies, particularly different actuators and sensors, driving and behavioral models [4]. UAV programs range from the combat tested MQ-1 Predator to the NASA funded Aero Vironment Helios drone which demonstrated about 40 hours of solar-powered flight attained by covering wings upper surfaces with solar panels, providing long endurance. Size and range of UAVs also vary very greatly, for instance the Pioneer at 14 feet long has an operational radius of 100 nm [5], while Global Hawk at 44 feet long has an operational radius of 13,500 nautical miles [4]. EADD’S Corporate Research Centre has built an MAV, weighing 520 g and measuring 44×44 cm, to demonstrate the potential of miniature technologies. Tallinn University of Technology (TUT) has always had close link with innovative technology firms in Estonia. A good example is ongoing collaboration between company and TUT in the field of UAV development and research. Unmanned Ground Vehicle (UGV) Unmanned Ground Vehicles are similar in principle of working except they are operating on the ground. There are many types of UGVs in worldwide, staring from tiny micro robot up to big military vehicles. Most well known UGVs are operating in military field especially bomb disposal applications. However these vehicles are mostly man operated and do not have lot of autonomity. In civilian market UGVs are mostly used in warehouses and closed areas for routine tasks. In recent years the UGVs are entered into the service market and are now popular for the hose cleaning (e.g. iRobot vacuum cleaner and pool cleaner), lawn mower and other everyday tasks. In Tallinn University of Technology (TUT) several mid-class UGVs are developed already five years. In this study the successor “UKU” of first civilian mid-class robot is used. UKU is a standard four wheel robot. Electrically powered the robot can have different applications like cleaning the roads, serving the agricultural works, guarding the restricted area, etc. Modular structure grants the flexibility of defining the task. Nevertheless whatever task is assigned to the robot the main navigation and obstacle avoidance is needed and is built in as base algorithm. Robot has two types of operations: man operated or autonomous regime. In autonomous regime the algorithm consists of base functionality and task specific functionality. Base functionality is similar to most unmanned vehicles and can therefore be designed in more abstract level than just device specific level. For base route planning and waypoint action a common system can be applied as well as common software platform for different vehicles used. The special development methodology is used for UKU design already in conceptual design phase where new integrated approach is applied [6]. Taking into account our development activity in UGV field and co-operation with UAV developers in private sector the co-operation between vehicles and common navigation planning platform is very much needed. Software Platform Every UMS has do have some kind of control system. Pre-Programmable or online programmable, it always has some kind of software platform to control or program the vehicle. So fare every autopilot or control system developer has its own vehicle and software platform. It is not possible do use the platforms or software independently. There is no official software for UAV ground control stations. All autopilot producers have their own software for ground control units. There is no common software platform for UAV applications. There for it would be could idea to start making universal navigation algorithm for UAV systems and if possible include UGVs as well. UAVs usually have ground control software divided into two main parts. Map window and controls panel. On the Fig. 2 the map window is in the left and control panel at the right. Map window is used for mission planning and online situation awareness and control panel for controlling the plain sensors and its withal parameters.
Fig. 2 UAV map and control panel window Route Planning Metamodel and Unified Platform Concept When planning autonomous navigation for unmanned vehicles different aspects have to be taking into account. For example for ground vehicle it is important to have good obstacle avoidance algorithm and object detection on the route whereas aerial vehicle have to deal with wind and altitude. However many high level operational targets have similar structure and can be unified for both type of vehicles. This benefits especially if we need to plan joint mission for the vehicles and where the autonomity is required. In this study we have focused for the waypoint action defining and high level rout planning. The platform uses newly developed System Modeling Language (SysML) [7] for the activity planning. Special SysML profile is developed for the mobile robots [8], which provide common scenarios for the faster development. Route planning metamodel defines the planning method and process of building autonomous navigation algorithm. Simplified metamodel is shown in Fig. 3. The main aspects of creating algorithm is setting waypoints, action selecting in this waypoint, action parameter definition, guard conditions of accomplishing task in the waypoint and message exchange.
Fig. 3 Simplified metamodel of autonomous navigation planning
In every waypoint certain task can be picked. If there is no suitable task in the database a new task can be dynamically defined according to the task definition rules. In total following common actions are defined in the system: • border patrol • disaster monitoring • nuclear radiation probing or sampling • day/night reconnaissance • target positioning • field/area monitory As an example some vehicle specific tasks are listed: • aerial photography • geophysical prospecting • artillery spotting • field damage and casualty assessment • atmosphere gas analyses • plot cleaning These actions are defined in the system and when selected, custom parameters have to be assigned. Every functional action is defined as a certain chain of single actions by the SysML activity or state machine diagram. In the Fig. 4 the example scenario is shown where SysML with custom profile is used. act target positioning
Get_object(dist) Operator interrupt
Scan Area false
object found?
Get_object_pattern[] Object lost
true
Record detection
Object Identification Get_object_params[]
false
Send stream
target object?
true
Alert
Fig. 4 Target positioning activity
Track object
When the navigation scenario is defined the target specific source code is expected to be delivered, which can be uploaded directly to the onboard control computer. This requires target specific interfaces especially when non-standard control system is used on the vehicle. The developed system uses newest technological and operational concepts, providing a solution to a wide range of requirements targeting flexibility and cost efficiency, which are considered the most important factors in small country case. It is considered that the developed system can be operable standalone, or integrated into a comprehensive surveillance and collaborative system. Conclusions and further work This paper discusses the status of the development activities in the field of making universal navigation algorithm planning platform for unmanned systems. Brief overview is given of different unmanned systems used as test platforms. Targeting on universal applicability of the UAV and UGV route planning metamodel and unified platform concept is presented. The overview is given of the current achievements and main considerations are discussed. The efforts for improving the route planning and message exchange platform design for various civilian applications taken into focus and near future conceptual software design will be concluded. As the areal platform (UAV) have usually better line of sight capabilities, it is better do use UAV as relay platform for message exchange with UGV and GCS (Ground Control Station). If the GCS is very close to UGV it is better do use GCS as the main message exchange unit. Both platforms can then communicate with GCS directly. Acknowledgment This research was supported by the Estonian Scientific Foundation grant ETF7542. References [1] [2] [3] [4]
[5] [6] [7] [8]
Information in: http://www.puav.com Information in: http://www.capitol.northgrum.com Unmanned Aerial Vehicles Roadmap, Office of the Secretary of Defense, 2002 Leomar, P.; Tamre, M.; Riibe, T.; Vaher, T.; Haggi, T. Optimal Design and Analysis of UAV Swan Fuselage. Solid State Phenomena, 113 : Mechatronic Systems and Materials, p. 91 - 96., 2006 North Atlantic Treaty Organization, Applications, Concepts and Technologies for Future Tactical UAVs, Tallinn RTO Lecture Series Sell R., Coatanea E., Christophe F. Important aspects of early design in mechatronic, 6th International Conference of DAAAM Baltic Industrial Engineering, Tallinn, 2008 System Modeling Language (SysML) Specification. Version 1.0 Draft. OMG document ad/2006-03-01, 2006. http://www.sysml.org Sell, R. Model Based Mechatronic Systems Modeling Methodology In Conceptual Design Stage, PhD thesis, TUT Press, Tallinn, 2007
