Research And Application Of Robot Force Position Control Methods For Robot-Environment Interaction

With the continuous expansion of the application area of robotics and the sustained growth of the robot intelligent level request, the position tracking control pointed robot control system can no longer meet the application in complex environments(assembly, polishing, deburring, human augmentations, rehabilitation robotics). The position force control method for the robot-environment interaction is aimed at establishing robotic end-effector force and position tracking control simultaneously, it meets the requirements of robot motion control in the complex environment. At present,studies on force position control between robot and environment mainly focus on the robot impedance control and the hybird position/force control of a robot.This thesis, supplied by the National Natural Science Foundation, the National Science and Technology major project, specializes the key technologies of the robot force position control method for the robot-environment interaction, the main content and innovation of the thesis is as follows:The performance of conventional robot impedance control mainly depends upon the environment dynamics and the choice of the expected impedance model. To maintain the performance of the robot impedance control in a wide range of environments, the expected impedance model needs to be adjusted adaptively. The caculation of the spring parameter of the impedance model in system steady-state conditions is based on the self-defined force impedance control performance index. Combined with the environment spring equivalence value estimated by neural networks and the second-order systems critical damping condition, the damping initial value of the impedance model is determined. In order to improve the force position tracking static-dynamic performance, the self-turning fuzzy control method is designed to achieve adjustment for the damping and spring parameters of the impedance model based on the measured force, position and its derivative in real time. Moreover, the environment position tolerance for maintaining contacted status and establishing expected force tracking control for the robot-environment interaction is illustrated.The quasi-velocity-based robot position control method for a robot in the operational space is also proposed to improve the dynamic performance of the robot motion control.The hybrid position, posture, force, and moment control method of a robot is proposed by the modification of the conventional hybrid position/force control. As for the question of the hybrid position/force control of a robot susceptible to system disturbance, the robot force control method based on Kalman active observers is proposed. Moreover, combined with the advantages of Kalman active observers and the hybrid position, posture, force and moment control method, the designed hybird position/force control of a robot exhibits good performance and is robust to system disturbances.The robot's physical impact and contact with the stiff environment is divided into approaching movement, impact oscillation, damping oscillation and steady stage successively. In order to stabilize the robot's physical impact and contact with an environment and achieve the expected contact force control, control strategies are designed for different phases:the robot noncontact impedance control method is designed for the approaching movement and the impedance parameters are adjusted by neuron networks for changing robot dynamics characteristics during the approaching movement, it decreases the succeeding impact/contact effect on the premise of fast approaching;in order to diminish the amplitude of the oscillation and shorten the impact duration time, the designed suppression controller represses the position rebound based on the robot end-effector's displacement, velocity and driving force in the impact oscillation phase, the varying-parameter robot force/velocity control method is designed to improve the stability of the damping oscillation phase based on the fast rate of energy dissipation of the system. Meanwhile, combined the control methods for the impact oscillation and damping oscillation, a fuzzy control method is designed to facilitate fine adjustments of the system force feedback coefficient based on the suppression control principle, it improves the force tracking control performance and stability of the impact/contact transition processes for the interaction between the robot and environment in contact.In the design of the polishing robot control system, the polishing force and position control is implemented by integrating the hybird position/force control and the robot impedance control principle:the designed impedance model following control method is adopted to realize the polishing force control in the constrained surface normal direction, the fuzzy logic controller plans the speed feed-forward in the constrained surface tangential direction based on the tool path data. In addtion, the realization of the software and hardware structure of the polishing robot control system based on the fieldbus is introduced.The feasibility and effectiveness of the control methods is confirmed by some experiment.