Proceedings of the 2005 IEEE International Workshop on Safety, Security and Rescue Robotics Kobe, Japan, June 2005
Development of a Shape Shifting Robot for Search and Rescue * Bin Li*1, Shugen Ma*2*1, Jinguo Liu*1*3, and Yuechao Wang*1 *1. Robotics Laboratory of Chinese Academy of Sciences, Shenyang Institute of Automation (SIA), China *2. Department of Systems Engineering, Faculty of Engineering, Ibaraki University, JAPAN *3. Graduate School of Chinese Academy of Sciences, Bejing, China
[email protected],
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[email protected] Abstract- In this paper, a novel link-type modular robot, which can change its shape, has been developed for potential application in Urban Search and Rescue (USAR) operation. The advantages of the robot with link-type structure have been specified, and its shape shifting principle has been discussed. A three-module shape shifting robot has three kinds of symmetry configurations, that is, line type, triangle type and row type. Each configuration possesses its unique mobility. A tracked prototype has been built and tested under various unstructured environment. Experiments have demonstrated its mobility and flexibility.
has performed perfect mobility and flexibility in uneven terrain.
I. INTRODUCTION (a)Snake climbing up stairs
Recently the frequent nature disasters and man-made catastrophes have aroused people’s attention on the importance of Urban Search and Rescue (USAR). Although people have more watchfulness than before, a large number of people still have died in unprofessional rescue due to inadequate equipment and being lack of professional manpower[1,2]. It is a great challenge in robotics research to develop search and rescue robot with fusing the robotics technology, rescue technology and disaster science. Researches sponsored by the countries and by the companies have resulted in the emergence of various kinds of search and rescue robots, especially after the World Trade Center attack[2]. As a frequently earthquake country, Japan government supports this research by the program--“Development of Advanced Robots and Information Systems for Disaster Response”. Hirose is one of the first researchers in this field. With his fellows, he has developed many kinds of search and rescue robot such as “ACM”, “HELLOS”, “Genbu” and "SORYU"[3,4]. And “CUBIC-R” which can change its shape into cubic or into line is also a kind of search and rescue robot in Japan[8]. In America this research has focused a lot attention too. In University of South Florida(USF), Murphy and her fellows have developed “Bujold”---a kind of search and rescue robot which has the ability of shifting shape and has been equipped with sensors[9]. In Carnegie Mellon Robotics Institute, researchers have developed multi-joint robot for inspection[10]. Foster-Miller Company also carries out three types of TALON robots.
The disaster locale is typical unstructured environment and the terrain’s variation is unpredictable. Mobility, adaptability and flexibility of the robot are crucial to rescue operation. Autonomy, high mobility, robustness and modularity are critical design issues of rescue robotics[1]. The link-type mechanisms, which are also widely used in snake-like robot or serpentine robot and multi-joint robot, have turned out to be effective and reliable in rescue operation for reasons in literature as listed bellow[1,4,11]: 1) With a low barycenter and sufficient contact to the ground, it has high stability over uneven terrain. 2) The link-type structure is a hyper-redundant system which has more degrees than that of its motion space. It has high flexibility to pose many kinds of configurations. 3) A link-type robot has excellent mobility. It can pass through the narrow space in line, can stand part of the body to overcome the obstacle in its way and can loose some degrees to adapt its body to the terrain. Link-type structure’s advantage is readily apparent in Fig.2. 4) For a link-type structure, it can adopt manifold gaits such as serpentine motion, concertina motion, sidewinding motion, rectilinear motion, thrusting motion, pushing motion, jumping and scrambling like a nature snake under different environments. They can move smoothly and fluently in lawn, in the sand ground, on the tree, in the water, in the ruins and even on the precipice. 5) The link-type structure is repeat, easily modularized and reconfigurable. A single modular unit may have limited mobility, but a swarm of them have good performance in collecting data and information.
II. LINK-TYPE STRUCTURE In nature there are many kinds of creature are in linktype. It can be seen from Fig.1 that the link-type structure *
This work is partially supported by China National High Technology 863 Program No.2001AA422360.
0-7803-8945-X/05/$20.00 ©2005 IEEE.
(b) Centipede moving in debris
Fig.1 Link-type structure in nature
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(a) Initial connection
Fig.2 Possible posture of link-type robot (b) Yaw180
Therefore, robot with link-type structure has a widely application not only to urban search and rescue but also to planet exploration, military reconnaissance, underground search or pipeline’s inspection.
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$ $ (c) Yaw 180 and then Pitch 180
Fig.4 A novel link-type structure
This type, with offset joints at both sides and with the link arm between adjacent modules, has enough flexibility to metamorphose. Most of important, no matter how many modules it has, this kind of link type robot can pose various kinds of symmetry configurations and trim configurations, especially being in line or in row.
III. SHAPE SHIFTING OF LINK-TYPE STRUCTURE Since a link-type robot can change its configuration to adapt to its surroundings when it navigates through debris. Shape shifting robot’s research has focused our attention. There are two kinds of shape shifting technique for linktype robot: reconfigurable and metamorphism. As mentioned before, the link-type structure is reconfigurable because the structure is repeat and modularized. The reconfigurable robot can change its configuration through restructuring, while the metamorphism robot changes its configuration with joints’ motion and without body parts’ disconnection or connection. Since the disaster locale is unstructured, restructuring is useful but difficult, metamorphism is more available than restructuring to some extent from the literature. First, the rescue work is time pressure while they consume a great deal of time to control pose to connect or disconnect. Second, the restructuring consumes more computation and power than shape shifting. Furthermore it is inefficient to telecontrol a swarm since there is short of hands in rescue operation. Therefore restructuring for shape shifting only can be used in urgent need whereas metamorphism can be widely used. For a link-type structure, the joint’s degree of freedom between adjacent units is usually limited by physical structure as shown in Fig.3.
IV. MECHANICAL DESIGN OF THE SHAPE SHIFTING ROBOT The wheel type, the leg type and the track type are often used in the mobile robot’s driving system. The wheel type system can move with high speed and high efficiency, but it has only limited wall-climbing ability and can not overcome the trench. The wheel type mobile robot has very low mobility over rough terrain. The leg type robot, which can move on almost all kinds of terrain, is difficult to design small and hard to control its balance. The leg type system has a complicated structure and a complicated control system. Both its speed and efficiency are very slow. Moreover, the leg has a small contact area to the ground. It thus makes a strong pressure on the soil. Since the module robot has mainly been developed for unstructured environment or hazard environment application, the tracked type is a suitable choice. The tracked type has good terrain adaptability and full contact the ground. Like a tank, the tracked robot has good mobility over uneven terrain and swamp. Based on above discussion, a standard module is designed to be mainly composed of a link arm, a trackdriven system, an offset Pitch joint, an offset Yaw joint and so on, as shown in Fig.5. It has three DC motors in which one drives the track, one is for Pitch joint and another is for Yaw joint respectively. Timing pulleys are used to driving the wheels forwards and backwards. The link arm is used to connect and disconnect the adjacent modules. The module in Fig.5 is a standard one. A novel link-type robot is repetitively composed of such modules. The key advantage of this type over other link-type vehicle is their ability adapted to the environments through various configurations.
Fig.3 A typical link-type structure
T
It is clearly seen that the range of both T H and v are $ less than 360 . In this paper we have proposed a novel kind of link-type structure which can shift shape as in Fig. 4.
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Centralized controller
CAN BUS
Performing controller
a. track with high gousers b. center-hollowed wheel c. Pitch joint driving motor d. link arm e. box cover f. track driving motor g. Yaw joint driving motor h. Yaw joint i. link handle
Performing controller
Performing controller
Ξ
Fig.7 Configuration of the Control System
Fig.5 A standard module
The centralized controller and each performing controller of the robot have the same configuration of hardware. When we have downloaded different program to it, we can get centralized controller or performing controller. It is easy for making and changing. The dimension of controller is 30mm * 42mm, as seen in the right of Fig.8.
Using such kind module, we have developed a threemodule shape shifting robot. To make full use of motors and minimize the weight and complexity, Pitch motor or Yaw motor often has been reduced at the free joints. The adjacent modules are connected through the link arm, the link handle and the offset joints. The three-module robot can change its shape by moving the offset joints. It can be seen from Fig.6 that the three-module shape shifting robot has three kinds of symmetry configuration. Each has its advantage and shortage for a certain obstacle or in a certain environment.
Fig.8 The configuration of control hardware
VI. PRELIMINARY TESTS OF THE PLATFORM Fig.6 The shape shifting principle
According to the design described above, a novel link-type modular robot which can shift shape has been developed. The specifications of the robot are given in Table 1.
V. CONTROL SYSTEM DESIGN OF THE SHAPE SHIFTING ROBOT
TABLE 1 SPECIFICATIONS OF ROBOT
Each processor (performing controller) controls the movement of the joint. A centralized controller is in the section of the middle module. All performing controllers are linked via a single serial bus (CAN-Bus) to the centralized controller that coordinates their movement, as seen in Fig.7. The performing controller sends the messages to the centralized controller by CAN bus and gets control commands from it. The performing controller outputs signal to the motion controller(MCDC2805). The motion controller can drive DC motor to move the joint.
Number of module
3
Dimension of module
0.24m*0.1m*0.1m
Weight of module
3kg
A. Experiment of Shape Shifting To test the shape shifting and to find out the problem existing in current design, we have performed shape shifting experiment on the three-module robot as shown in Fig.9.
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5) Climb up the obstacle: All the three types have obstacle climbing ability. The max heights for the line type, the triangle type and the row type are 270mm, 210mm and 50mm respectively, as in Fig.10 (e). 6) Climb over the debris: We have emulated the debris after building collapse by setting up a pile of wood and bricks. The row type and the triangle type have excellent stability while the line type is easy to lateral tipover, as seen in Fig.10 (f).
Fig 9 Experiment for the shape shifting of the robot
The three-module robot can change it configuration from one to the other fluently. The three-module shape shifting robot has three kinds of symmetry configuration, that is, the line type in Fig.9(a), the triangle type in Fig.9(e), and the row type in Fig.9(i). Experiment has demonstrated how the robot changes it configuration from in line type to in row type. The reverse process is exactly in the same manner. B. Experiment of mobility in the three symmetry types Each configuration has its own mobility correspondingly. There are many kinds of environments thought to be difficult for the robot to overcome. We choose the typical ones in the experiment to test the mobility of the link-type shape-shifting robot in line type, in triangle type and in row type. 1) Climb slope: The three types almost have the same slope climbing ability. The grade of slope is mainly decided by the friction coefficient between the track and the slope. Fig.10 (a) demonstrates that the robot can climb on a route with slope degree of 25°. 2) Pass through the trench: The robot in line has the best mobility in passing the trench for its long body as shown in Fig.10 (b). The maximum trench breadths for the line type, the triangle type and the row type are 450mm, 250mm and 150mm respectively. 3) Climb up stairs: The line type has the best stairs climbing ability as shown in Fig.10(c). The line type can climb the stairs whose tread is 300mm in length and riser is 150mm, while for the triangle type, 250mm and 125mm, and for the row type, 200mm and 100mm respectively. 4) Pass the hole: The robot passes the narrow hole mainly being limited by the configuration geometry. The line type passes the narrow space fluently as in Fig.10 (d).
Fig 10 Experiment for testing mobility of the robot
The experimental results show that the link-type shape shifting robot has high mobility in line type. For various kinds of environments, almost each configuration has its advantage and shortage. For instance, the robot in row has low mobility in the experiment to some extent, but it has a compact structure with good turning performance and tipover stability. It also can be seen from the experimental results that the shape shifting robot has a suit application in search and rescue. In the complicated environment, the shape shifting robot can be used as instrument-carrying platform. With certain instruments equipped, the shape shifting robot can be used in appointed task accordingly. VII. CONCLUSION In this study, we have proposed a novel link-type shape shifting modular robot for search and rescue operation. Being hyper-redundant, modularized and reconfigurable, the link-type shape shifting modular robot has a widely
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application such as Urban Search and Rescue (USAR) efforts and military reconnaissance. The key advantage of this design over other link-type vehicle is their adaptation ability to the environments through various configurations. Experiments have demonstrated that such kind structure permits good mobility and high flexibility to uneven terrain. The current platform has only limited application for its simple control system. When it comes to practical application, it is important to improve the control system, sensor system and communicating system in the near future. For various tasks, requirements such as the material of the robot, gas proof, water proof, power, wireless control, communication, and sensor have to be taken into consideration at the next step. REFERENCES [1]
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