Research On Performance Guaranteed Fault-tolerant Control Of Joint-robot Under Motion Constraints

The joint-robots,also known as robotic arms,are mechanical devices that are widely used in industry,life,and military.With the popularization and diversification of the application of the manipulator,higher requirements are placed on the fault tolerance of the actuator.Because the actuator of the articulated robot is often composed of a plurality of joints,the movement position of the end of the actuator and the movement speed are controlled by controlling the corresponding motor.However,in operation,friction and collision are inevitable between joints,and these effects will lead to control deviation and even control failure.In addition,due to the physical limitations of the actuator and the motor,its moving position and moving speed need to be guaranteed to be within the operational range,otherwise it will lead to task failure or even system downtime.Although there are articles dealing with actuator failures and state constraints,there are few studies that consider actuator failures and ensure stateful constraints in controller design.In addition,due to the flexibility and anthropomorphism of the manipulator actuator operation,even the precise task of needle threading can be accomplished.Therefore,it is necessary to conduct an in-depth study of the transient performance of its tracking process.At present,the most commonly used and most popular method for guaranteeing transient performance is the Predetermined Performance(PPB)technique,but at present the technology requires that the initial value of the convergence error satisfies the limit of its predetermined boundary.In other words,in the current research on PPB,subsequent derivation design under the assumption that the initial value requirements are met,there is little research to optimize this hypothesis.Therefore,based on the research status of articulated robots,in the case of driving faults in the control system,the PPB technology is optimized by designing the switching control scheme to achieve any performance constraints on the error and meet the requirements of full state limitation.Finally,the micro-carving robot is used as the physical platform,combined with matlab for joint simulation to prove the effectiveness of the proposed control strategy.The main contributions of this paper are as follows:(1)According to the commonly used adaptive control method,an adaptive control method independent of the model parameters is designed for the control system with uncertainties such as actuator failure,joint friction and external disturbance.And its stability and effectiveness are proved by the Lyapunov method.(2)Based on the fault-tolerant adaptive control method,for the problem that the initial error value of PPB technology is limited,the paper uses the switching control technology(supervised control and PPB-based control)to attenuate the error from any initial condition to the allowed residual set,which guarantees The entire tracking process meets predetermined performance metrics.The continuity of the control action is ensured by adding a soft linker at the switching point..(3)For the micro-screw robot physical platform,the above research results are applied to the robot end trajectory tracking control.The simulation results show that the tracking control method designed by the paper can achieve better tracking performance for the tracking control of complex end trajectories.