Fault Tolerant Control For Unknown Nonlinear Systems With Unknown Parameterizable Friction

In recent decades,along with the prosperity and development of society and science,industrial technology has been developed at a high speed and the complexity of modern control systems has been increasing.The control system that can be seen everywhere in every field,has brought great convenience to human life.Because of this,people are very concerned about the reliability and safety of the system,worried that the system failure will bring great harm to life,so fault tolerant control technology was born.Once actuators,sensors and system components fail,fault tolerant control technology can ensure the safe operation of the system or keep the system to complete the original mission objectives within a certain error tolerance range.In practical application studies,most of the systems are nonlinear,Therefore,the research of fault-tolerant control for nonlinear systems has become the focus of attention.This paper mainly introduces the fault-tolerant control problem of nonlinear systems with unknown parameter friction.Using fuzzy logic system,sliding mode control,adaptive control and other technologies,several fault-tolerant control schemes are proposed to eliminate the influence of faults and friction on system.Friction as a complex uncertain nonlinear phenomenon has not been considered in traditional control schemes,and this paper proposes a corresponding fault-tolerant control strategy for this phenomenon:Firstly,This paper deals with a kind of nonlinear uncertain dynamic systems with unknown friction,the fault-tolerant tracking control problem is studied,and an adaptive fuzzy control strategy is presented.This scheme uses the approximation ability of the fuzzy system and uses methods such as sliding mode control to determine the adaptive law of the adjustable parameters in the fuzzy system,and finally gives the control law.Based on Lyapunov stability theory,the closed-loop control system is proved to be consistent and bounded.Finally,the effectiveness of the design scheme is verified by the simulation results.Secondly,the problem of fault-tolerant control for a kind of nonlinear systems with unknown frictions and control directions is studied.For the problem of unknown control direction,the Nussbaum function is invoked.for the sake of solve the unknown nonlinear matter in the system,fuzzy logic system is used to estimate the unknown nonlinear function.The unknown friction of the system is estimated,then a fault tolerant control scheme by using sliding mode control design method has been pointing out.Through stability theory,the stability of the algorithm is analyzed,and it is proved that the tracking error can converge to an adjustable neighborhood of the origin.Finally,the effectiveness of the design scheme is verified by the simulation results.Thirdly,for a kind of multi-agent nonlinear systems with unknown parameters and friction terms,based on the sliding mode control principle,an adaptive coordinated tracking fault-tolerant control scheme is proposed to ensure that all followers asymptotically synchronize to a leading node,and tracking error A small adjustable neighborhood converges to the origin,and a distributed sliding mode adaptive controller is designed for each follower node to make the tracking error uniformly terminated and bounded.Based on algebraic graph theory and stability theory,the stability of the algorithm and the convergence of parameters are analyzed.Finally,the effectiveness of the design scheme is verified by the simulation results.