Redundant Design And Fault-Tolerant Control Of 3-PRS Parallel Robot With Actuator Fault

The Parallel Robot has the advantages of high stiffness,high speed,high precision and high load,and are widely used in machinery manufacturing,medical equipment and aerospace.However,in the process of operation,if any subsystem of the robot fails,the task will be unable to complete or even disastrous consequences.Therefore,this paper analyzes the dynamics of 3-PRS Parallel Robot with actuator fault for the purpose of fault-tolerant control;A new redundant mechanism of 3-PRS Parallel Robot is designed for actuator failure and its workspace is studied,and on this basis,the fault detection and fault-tolerant control methods for actuator of the robot are discussed.The specific research contents are as follows:(1)Dynamics analysis of 3-PRS Parallel Robot with actuator failure.The kinematic model of 3-PRS Parallel Robot is established by using closed vector method,and velocity and acceleration equations of moving components are derived;The dynamics of 3-PRS Parallel Robot with actuator failure is analyzed by using d’Alembert’s principle,and mathematical expression between driving force and internal force of moving member is established.The variation of driving force and joint internal force of 3-PRS Parallel Robot and driving force at different stuck positions are obtained through simulation.It provides theoretical basis for redundant mechanism design.(2)Design the redundant mechanism of 3-PRS Parallel Robot.Aiming at actuator faults,a redundant mechanism of a new 3-PRS Parallel Robot is designed based on the sub-chain of kinematics and its structural characteristics;The spiral theory and modified Kutzbach-Grubler formula are used to analyze and calculate the degree of freedom of the redundant mechanism.The results verify the rationality of the redundant mechanism designed and provide conditions for subsequent fault-tolerant control.(3)Study the workspace of 3-PRS Parallel Robot with redundant configuration.The kinematics model of parallel robot with redundant configuration is established,and an improved Monte Carlo method is put forward to solve the workspace,and specific steps are given to improve the calculation efficiency and boundary accuracy;By analyzing the factors affecting workspace,the workspace maps of parallel robot is drawn through MATLAB programming,and the reachable workspace under different parameters is analyzed.(4)Discuss the actuator fault detection and fault-tolerant control of 3-PRS Parallel Robot with redundant configuration.The dynamic equation and actuator fault model of single-branch drive subsystem are established,and the state space equation under fault is derived;Then the sliding mode observer is designed and the appropriate observer gain and sliding mode control law are selected to detection the actuator fault.The fault-tolerant control strategy and implementation method under position mode control are discussed,that is,the system detects the fault actuator in time,and calculates the input parameters for redundant actuators based on the inverse kinematics solution according to the fault position and end trajectory,so as to realize the fault-tolerant control under the fault and complete the target trajectory.