Kinematic Control Of Serial Manipulator Under Complex Constraints

Since first robot was born in 1950s, robot technology has attracted much attention. Compared with the parallel robot, the serial manipulator has larger reachable workspace and better controlla-bility, as a result it has been widely applied in industry. As in the past twenty years, with the rapid development of computer technology and sensor technology, robot application is no longer limited to industrial field or in the laboratory, robots are gradually applied in the deep-sea operation, the unknown space exploration and home service and other fields. and in these new applications, robot should be more adaptive for complex dynamic environment. How to handle a variety of complex constraints in dynamic environment is a new challenge for robotic technology.The research focuses on manipulator kinematic control under time-dependent constraints, second-order kinematic control under joint constraints, in order to find serial manipulator kinemat-ic control method under complex dynamic constraints, as well as obtaining an effective solution of theory and technology for robot application in complex environment. An intelligent arc welding robot named ZT-010 is developed by our laboratory and Zhejiang Zhengte Group Co., Ltd and another pingpong robot is designed for research. Theoretical research with simulation and exper-imental verification is systematicly carried out on these robots. Our research work of this thesis include:1) Time-dependent general-weighted least-norm method is proposed to solve redundant manipu-lator control problem with time-dependent constraints. Tradition on-line algorithm can not deal with manipulator under time dependent constraint, this paper proposes time-dependent general-weighted least-norm method, based on general-weighted least-norm (GWLN) method. By intro-ducing time-dependent virtual joints, inverse kinematic problem is solved in the virtual joint space. A new inverse-weighted matrix setting criterion is proposed to replace the one-step prediction that originally complicated implementation of the GWLN method. To demonstrate the efficacy of the method, simulations and experiments are carried out on a five-link welding manipulator ZT-010 to track the welding trajectory. Time-dependent orientation constraint and preventing joint limits is guaranteed using this method.2) Time-dependent general-weighted least-norm method could deal with manipulator control under time-dependent constraints, but it can not deal constraint with joint velocity. This paper proposed a method, which could deal with both joint limit constraint and joint velocity constraint. First, the method converts the joint limit as a joint velocity constraint with time variant thresholds. Then real joint space mappings into the revised joint space. In the revised joint space, joint limit constraints can be guaranteed by the weighted least-norm method, meanwhile this method can achieve joint velocity constraint by adjusting the weight factors. The paper also gives a further proof that the both joint limit constraint and joint velocity constraint can be guaranteed by the method.3) Second-order inverse kinematics control for redundant manipulator may exhibit instabilities as a result of joint self motion, which makes the control algorithm of non-redundant manipulator with both joint velocity and joint limit constraints can not be applied to the case of redundant manipula-tor. This paper proposes a new idea of second-order kinematic control of redundant manipulator: if the end-effector moves, ensure the homogeneous joint velocity is bounded; if the end-effector of manipulator is still, the homogeneous joint velocity convergence. And the clamping weighted-least norm (CWLN) method is applied to solve second-order kinematic problem of redundant manip-ulator with joint constraint. The clamp velocity has two effect:when joint velocity constraint is triggered, it accelerates joint velocity away from the velocity threshold. When the end-effector of the manipulator is still, it will suppression of self motion.