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Combined torque and velocity control of a redundant robot system

出版	INTECH Open Access Publisher, 2006
ISBN	386611284X9783866112841
URL	http://books.google.com.hk/books?id=NSnioAEACAAJ&hl=&source=gbs_api

註釋The use of the robots in the real world mostly depends on the development of a autonomous robotic systems that integrate mobility and manipulability. This chapter has presented a new approach to the robot control. The control is called combined control since it combines (integrates) two different types of robot control, i.e. the torque and the velocity control in a single robot system. Later on the mathematical analysis of the proposed combined control has been shown. Verification has been done on a simulated and a real system composed of a velocity controlled mobile platform and a torque controlled manipulator. The results show good tracking of the desired trajectory in the task space and in the null space depending on the controller gains. Controller gains also define the compliance of the system in the task and in the null space. We defined the stability region of controller gains. Regarding the system performance the combined control can be placed somewhere between velocity and torque control. Most of the properties of the combined control are comparable to those of the torque control and they are much better than those of the velocity control. When considering the trajectory tracking the combined control is comparable to the torque control, since in both cases most of dynamic interactions are compensated. The disadvantage of the combined control is inability of dynamic consistency and stiff behavior of the system when external forces act on the velocity controlled subsystem. On the other hand, the system with the combined controller can be compliant to external forces acting on the end-effector or on the segments of the torque controlled subsystem. We have proved on a real system that the compliant control enables the mobile manipulator to avoid all obstacles in its workspace. Some of the obstacles are detected and they generate repulsive velocity. On the other hand we do not detect obstacles near the manipulator; avoidance is obtained by compliant control in the null space. We achieved a compliancy also in the task space. Summarizing, the combined control is suitable for most applications where torque control is desired and part of the system can not be torque controlled. Additionally, no hardware modification of the motor controller in velocity controlled subsystem is necessary.