Fuzzy Adaptive Dynamic Surface Control Of Flexible Joint Manipulator

The dynamic characteristics of flexible joint manipulator are complex,time-varying,highly coupled and strongly nonlinear.Considering the uncertainties of unmodeled dynamics,parameter measurement error,modeling error,load variation and joint friction,it is difficult to establish an accurate dynamic model of flexible joint manipulator.The above factors seriously affect the dynamic and steady-state performance of flexible joint manipulator control,so it is of great significance to study the control problem of flexible joint manipulator with modeling error and internal model uncertainty.In this thesis,the trajectory tracking control problem of flexible joint manipulator without precise dynamic model is studied,and the problems of difficult measurement of angular position,angular velocity and limited input torque are considered.The main contents of this paper are as follows:(1)Aiming at the modeling error and internal uncertainty of flexible joint manipulator,a fuzzy adaptive dynamic surface state feedback control strategy is proposed.Firstly,an adaptive fuzzy logic system is constructed.Through the continuous adjustment of the adaptive law,the fuzzy logic system approaches the nonlinear term of the flexible joint manipulator.Then the backstepping controller is designed according to the state feedback information of the flexible joint manipulator.In the backstepping design process,the dynamic surface control technique is integrated,and the system control signal is constructed by error surface variables and low-pass filter variables,so as to avoid the explosion of computational complexity caused by iterative differentiation of nonlinear functions.The Lyapunov stability theorem is used to prove that the trajectory tracking error of the flexible joint manipulator converges to the zero point,which ensures the trajectory tracking control of the flexible joint manipulator.(2)Aiming at the problem that the angular position of motor,angular velocity of motor and angular velocity of connecting rod of flexible joint manipulator are easily polluted by noise and difficult to measure accurately,a fuzzy adaptive dynamic surface output feedback control strategy is proposed.According to the mathematical model of the flexible joint manipulator,the corresponding state observer is designed and the output feedback control algorithm is completed,which solves the problem of trajectory tracking control of the flexible joint manipulator whose state is not completely measurable.At this time,the flexible joint manipulator can realize trajectory tracking control without adding speed and position sensors.The advantage of output feedback control algorithm is that it simplifies the complexity of physical structure of flexible joint manipulator and reduces the economic cost of components.(3)Aiming at the problem of input torque limitation of flexible joint manipulator,a fuzzy adaptive dynamic surface control strategy is proposed,which can effectively restrain the input limitation.Due to the physical structure limitation,mechanical manufacturing and other practical factors of flexible joint manipulator,it is inevitable that the expected torque cannot match the actual torque,which will reduce the control accuracy of the system,or cause the system to stop normal operation.In this paper,a fuzzy adaptive dynamic surface control strategy is proposed by introducing auxiliary signal to suppress the influence of actual torque limitation and combining with backstepping method.By using Lyapunov stability theorem,it is proved that the trajectory tracking error of flexible joint manipulator converges to the zero point,and the trajectory tracking control problem of flexible joint manipulator considering input torque limitation is solved.