The Fault-tolerant Control For Manipulators With Actuator Failure

In industrial,robots can easily accomplish many different tasks,such as space exploration,deep-sea exploration and other high-risk tasks.The development of technology promotes the application of the manipulators,and it is hoped that the manipulators can complete the tasks better.However,the manipulators system working in the extreme work environment for a long time,which limited by its own structure,resulting in the failure of actuators,sensors or other components inevitably.This may affect the system's control performance,even lead to system instability.Therefore,the problem of fault tolerant control on manipulators is something that must be solved.This paper mainly studies the fault tolerant control of manipulators system with actuator failure.The main work of this paper can be summarized as follows:Firstly,a fault tolerant control strategy is proposed based on model predictive control method for a robotic manipulator with actuator faults and input constraints to be considered.The system dynamics model with actuator faults is established by Taylor series.The Fault Detection and Diagnosis unit is designed to diagnose the fault and estimate the fault information.Then the controller is achieved by virtue of model predictive control approach which can stabilize the closed loop systems,which tracking of given instructions,and satisfy the input constraints even though some actuator faults occur in a manipulator.Finally,a numerical simulatio n is carried out to verify the proposed fault tolerant control method in this paper is feasible.Secondly,a fault tolerant control strategy by combining Model Predictive Control and Sliding Mode Control is presented for uncertain robotic manipulators with constraints and actuator faults.Setting up a fault model,and design Fault Detection and Diagnosis unit to estimate the fault information.Sliding Mode Control is employed for its robustness to deal with unexpected uncertainties,and employing Model Predictive Control in order to consider the input constraints.The predictive sliding mode control method combined with the advantages of Model Predictive Control and Sliding Mode Control strategies is so popular and overcome most of their drawbacks,and can solve the problem of nonlinearity,strong coupling and uncertainty of the manipulators system.The predictive sliding mode control method when occur actuator failure can ensure the stability of the system,while the chattering phenomenon is eliminated.Finally,a numerical simulation is carried out to demonstrate the effectiveness of the proposed method.Thirdly,a fault tolerant control strategy is presented for uncertain robotic manipulators with constraints and actuator faults.A double-layered control structure for manipulator control is proposed.Setting up a fault model,and design Fault Detection and Diagnosis unit to estimate the fault information.The control structure is composed of planning layer and tracking layer.For the uncertain manipulators system which considered the possible failure of actuator,the planning layer designs designs an optimal reference trajectory by the model predictive controller,and the tracking layer mainly computes optimal control torque to make the manipulator accurately track the reference trajectory though the fault tolerant controller based on the predictive sliding mode control.According to the requirements of different control targets,a controller with corresponding functions is designed to complete the motion control of the manipulator.Finally,a numerical simulation is carried out to demonstrate the effectiveness of the proposed method.