Finite-Time Adaptive Fault-Tolerant Control Of Manipulator Systems

In industrial control,there are many complicated and repetitive tasks that cannot be completed by human beings,such as space exploration,deep-sea exploration and other tasks with certain risks.With the development of robotic arm technology,these tasks can be easily accomplished by using robotic arm.However,due to the long-term work in extreme working conditions and the limitation of the structure of the manipulator itself,the sensors or actuators carried by the manipulator will inevitably fail,which will affect the control performance of the system,and even the manipulator will not move according to people’s expected trajectory.At present,the research on fault tolerance of manipulator is not comprehensive,and there are still some problems to be solved.Therefore,it is necessary and meaningful to study the fault-tolerant control of manipulator system when sensors or actuators fail.In this thesis,Lyapunov stability theory,fault-tolerant control,finite time theory,adaptive control and so on are used to study the trajectory tracking fault-tolerant control of a class of rigid manipulators with sensor or actuator faults.The research results are as follows:(1)Aiming at the sensor failure,drift,fixed deviation and precision decline of the manipulator,a fault model of the manipulator system is established.Combining adaptive control,fault-tolerant control and finite time theory,a finite-time adaptive fault-tolerant controller for the manipulator system with sensor failure is designed.In addition,Lyapunov obstacle function and radial basis function neural network technology are introduced in the design.The former is used to achieve the approximation of unknown functions in the system,and the latter is used to ensure that the tracking error of the system is limited to a given region.The results show that under the action of the controller,even if the sensor fault occurs in the controlled system,a better trajectory tracking effect is achieved.(2)Considering that sensors and actuators may fail at the same time,and in order to further improve the convergence speed of the manipulator system,a fast finite time adaptive fault-tolerant controller is designed.At the same time,by introducing a tracking differentiator,the complexity problem caused by repeated derivation of virtual control law in backstepping method is overcome.The results show that the controller can achieve faster response speed and better robustness.(3)The feasibility of the above schemes is verified through simulation examples.Whether sensor or actuator failures occur in the manipulator system,the two schemes can ensure that the actual output of the manipulator system and the desired trajectory have a good tracking effect.