Attitude Control Of A Rigid Body And Its Application To Robot Control

Robotics research is the embodiment of man's long-standing and deep desire to create something like himself,and robot is the highest form of the achievements in mechanical bionics. Now robot is the integration of many high and new technologies.As is well-known,the intelligence of a robot is derived from its control system,and the basic problem of a robot control system is the manipulation of the robot arm and its end-effector. When the robot arm and its end-effector is treated as a rigid body,as is quite reasonable in most cases,the motion control,especially attitude control,of a rigid body becomes the basic problem of robot control.Based on the above perception,we carried out systematic research on attitude control of a rigid body and its application to robot control. Our research is supported partly by the National Natural Science Foundation of China (Grant No. 69774010),Aeronautical Science Foundation of China (Grant No. 97D53040) and the National 973 Fundamental Research Program of China ( Grant No. G1988030417).The main contributions of this dissertation are as follows:(1) Four kinds of parameters for representing the attitude of a rigid body are studied. They are attitude matrix,Euler angles,quaternion,and Rodrigues parameters. Formulas are given for changing from any kind of parameters to the other three kinds of parameters. The model for attitude stabilization is established using quaternion or Rodrigues parameters,and the model for attitude tracking is established using error quaternion or error Rodrigues parameters.(2) Attitude stabilization and attitude tracking are then studied. As is known,the existing control laws require full state information,including attitude parameters and angular velocities. Usually,angular velocities are difficult to oh tain,or even if they can be obtained,they are usually contaminated by noises. Tosolve this problem,we propose an output feedback control law without angular velocities by making use of the inherent passivity of the attitude control system.(3) Usually,there are two kinds of unknown external disturbances and/or modeling uncertainties:one in the inertial matrix,and the other in the control matrix. The existing robust attitude controllers can only deal with disturbances and/ or uncertaities in the inertial matrix. In this paper,we for the first time present an adaptive robust attitude controller which is robust to the disturbances and/or uncertaities in both the inertial matrix and the control matrix.(4) Output feedback controllers are proposed for eliminating velocity measurement in robot control systems. In the task space,the attitude space of the robot end-effector is parameterized by Rodrigues parameters,and an output feedback controller without the generalized velocity is designed for controlling the position and attitude of the end-effector of a rigid robot. The existing dynamic output feedback schemes use a seven-order passive network,but our dynamic controller is realized by a six-order square linear system. In the joint space,proportional plus derivative (PD) controllers without joint velocity measurement are designed by making use of the inherent passivity of the robot control system.(5) In the existing robot controller,the gravity compensation item needs to be computed for each joint state,it is quite a burden for real-time control. We proved in this paper that under a certain condition the gravity compensation item can be replaced by the constant gravity compensation item at the equilibrium point,thus greatly reducing the computation overhead.(6) We also improved the existing controllers for elastic joint robot by the passivity approach,and an output feedback controller is designed,which only requires the measurement of the actuator position.(7) Finally,based on the linearization of the robot control system,we studied the stability criterion of an Internet-based robot control system which is a linear system with multiple time-delays. A new and less conservative stability criterion is given,and a controller for...