System and method for controlling modular robots

• US 20060095169A1
• Filed: 04/15/2005
• Published: 05/04/2006
• Est. Priority Date: 04/15/2004
• Status: Active Grant

• Current Assignee: University of Utah Research Foundation (State of Utah)
• Original Assignee: University of Utah Research Foundation (State of Utah)
• Inventors: Minor, Mark A., Schwensen, Corey
• Granted Patent: US 7,400,108 B2
• Time in Patent Office: Days
• US Class Current: 701/23
• CPC Class Codes: G05D 1/0293 Convoy travelling

Abstract

Techniques are described for control of a robot system, wherein the robot system includes a plurality of individual wheeled robot modules interconnected by at least one compliant member. The technique includes developing a kinematic control model of the robot system from a combination of the kinematic characteristics of the individual wheeled robot modules and the stiffness properties of the compliant member. Development of the kinematic control model for a reconfigurable robot system is enhanced by the scalable nature of the technique.

Claims

1. A method of controlling motion of a robot system wherein the robot system includes a plurality of individual wheeled robot modules interconnected by at least one partially compliant member, the method comprising:

developing at least one scalable kinematic model corresponding to one of the plurality of individual wheeled robot modules;

deriving a system kinematic model of the robot system based on a combination of the at least one scalable kinematic model and stiffness properties of the at least one partially compliant member; and

translating a planned motion of the robot system into planned motions of the plurality of individual wheeled robot modules using the system kinematic model.

2. The method of claim 1 wherein developing at least one scalable kinematic model comprises developing a single scalable kinematic model corresponding to a plurality of substantially identical individual wheeled robot modules.

3. The method of claim 1 wherein developing at least one scalable kinematic model comprises developing N scalable kinematic models corresponding to N different individual wheeled robot module configurations.

4. The method of claim 1 wherein deriving a system kinematic model of the robot system further comprises forming a frame stiffness matrix wherein the frame stiffness matrix represents coupling between the plurality of individual wheeled robot modules through the at least one partially compliant member.

5. The method of claim 1 wherein translating a planned motion of the robot system further comprises maximizing wheel traction forces.

6. The method of claim 1 wherein translating a planned motion of the robot system further comprises sensing a relative posture of the plurality of individual wheeled robot modules.

7. The method of claim 1 wherein translating a planned motion of the robot system further comprises maintaining a predefined mechanical constraint on the at least one partially compliant member.

8. The method of claim 7 wherein the predefined mechanical constraint is to limit force applied to the at least one partially compliant member to a bending force.

9. A method of controlling motion of a robot system wherein the robot system includes a plurality of individual wheeled robot modules interconnected by at least one partially compliant member, the method comprising developing a kinematic model of the robot system for translating between planned robot system motion and individual wheeled robot module motion commands based on a combination of kinematic characteristics of the plurality of wheeled robot modules and stiffness properties of the at least one partially compliant member.

10. The method of claim 9 further comprising accounting for force-deflection coupling between the plurality of individual wheeled robot modules through the at least one partially compliant member.

11. The method of claim 9 further comprising accounting for post-buckling force-deflection of the compliant member.

12. The method of claim 9 further comprising translating a planned motion of the robot system into planned motions of the plurality of individual wheeled robot modules using the system kinematic model wherein mechanical loading on the at least one partially compliant member is taken into account.

13. The method of claim 9 further comprising adjusting planned motions of the plurality of individual wheeled robot modules based on sensed deflection in the compliant member.

14. A module controller for a robot system wherein the robot system includes a plurality of individual wheeled robot modules, at least two of the wheeled robot modules having drive means and interconnected by at least one partially compliant member, the module controller comprising:

an input device configured to receive a desired robot system motion;

a processor circuit coupled to the input device and configured to determine at least one output control value corresponding to at least one of the drive means, wherein the at least one output control value is developed from kinematic model of the robot system and the kinematic model is based on a combination of kinematic characteristics of the individual wheeled robot modules and stiffness properties of the at least one partially compliant member; and

at least one control driver coupled to the processor circuit and configured to output the at least one output control value to at least one of the drive means.

15. A robot system, comprising:

a plurality of individual wheeled robot modules, at least two of the individual wheeled robot modules having drive means and interconnected by at least one a partially compliant member; and

a control system in communication with the plurality of individual wheeled robot modules, the control system configured to translate a desired robot system motion into individual wheeled robot module motion commands using a kinematic model obtained from a combination of kinematic characteristics of the individual wheeled robot modules and stiffness characteristics of the at least one partially compliant member.

16. The robot system of claim 15 wherein the control system is mounted to one of the plurality of individual wheeled robot modules.

17. The robot system of claim 16 wherein the control system further comprises a communication link configured to communicate individual wheeled robot module motion commands from the control system to the plurality of individual wheeled robot modules.

18. The robot system of claim 15 wherein the control system is physically distributed across the plurality of individual wheeled robot modules so that each individual wheeled robot module has a portion of the control system.

19. The robot system of claim 18 further comprising a communication network configured to communicate the desired robot system motion and the individual wheeled robot module motion commands between the plurality of individual wheeled robot modules.

20. A robotic system comprising:

at least one partially compliant frame connecting a plurality of substantially rigid axles, each substantially rigid axle having at least two wheels wherein a coordinated actuation of said wheels controls deflection of the at least one partially compliant frame;

a compliance control model configured to control the robotic system, said model employing scalable dynamic models and a modular modeling structure and comprising at least one dynamic controller.

21. The system of claim 20, wherein compliance in the at least one partially compliant frame is provided by rotary joints coupled to at least one end of each partially compliant frame.

22. The system of claim 20, wherein a wheel is rotationally connected to a first side and a second side of each substantially rigid axle.

23. The system of claim 20, wherein a first side of each partially compliant frame is connected to a first substantially rigid axle and a second side of each partially compliant frame is connected to a second substantially rigid axle.

24. The system of claim 23, wherein each partially compliant frame is connected to an approximate center of the first and second substantially rigid axles respectively.

25. The system of claim 20, wherein each of the at least one partially compliant frames is responsive to rotation of the wheels to enable roll and yaw degrees of freedom for the compliant frame.

26. The system of claim 25, wherein the roll facilitates adjustment of the frame to enable mobility of the robotic system on uneven surfaces.

27. The system of claim 25, wherein the yaw allows the substantially rigid axles to independently change heading via independent wheel control.

28. The system of claim 20, wherein the compliance control model establishes a scalable foundation of modular dynamic models.

29. The system of claim 20, wherein the compliance control model supports backstepping control algorithms for dynamic trajectory tracking.

30. The system of claim 20, wherein the compliance control model includes a modular kinematical model.

31. The system of claim 20, wherein the compliance control model includes a compliant frame model.

32. The system of claim 20, wherein the compliance control model includes an axle module dynamic model.

33. The system of claim 20, wherein the compliance control model includes a backstepping control model.