Command Filtering Control Of Flexible Joint Manipulator Considering Time-varying Full-state Constraint

With the advancement and progress of sci-tech,robotic manipulators have been widely used in many important fields such as biomedicine,3C electronics,disaster relief detection,aerospace and so on.Compared with traditional rigid manipulator,flexible joint manipulator(FJM)has such advantages as safe,low consumption,light weight and high flexibility,which is more suitable for the manipulator applying in the above-mentioned important fields.However,the FJM system is a high ordered system with strong coupling and nonlinear,and the problems of time-varying parameters and external disturbance in practical application greatly increase the difficulty of FJM control.In addition,the working space of the FJM is often constrained to a certain extent in practical work,beyond which the structure of the manipulator may be damaged,and even personal safety may be endangered in serious cases.Therefore,how to improve the control accuracy of FJM while satisfying the state constraints of the system has become a very practical research topic.Regarding the above issues,this paper combined the log-type time-varying barrier Lyapunov function,command filtered technology and backstepping control methods,proposed the command filtered backstepping control based on time-varying full state constraints for single-link systems and n-link FJM systems.the main research results are as follows:(1)For a single-link FJM system,the position tracking control problem of manipulator end under symmetric time-varying full state constraints was studied.The amplitude of state variables such as joint angle position and motor angle position of single-link FJM was constrained by symmetric time-varying Lyapunov function,so as to ensure that all state variables would not exceed the given limited area.A command filtered backstepping controller based on symmetric time-varying constraints is built by introducing command filtered control technology with error compensation mechanism to tackle the problem of "explosion of complexity" in the classical backstepping method.Finally,the system’s stability is demonstrated using the Lyapunov stability theorem,and the simulation experiment demonstrates that the control method provided in this chapter can satisfy the system’s state requirements while achieving good tracking control effect.(2)For an n-link FJM system with uncertain parameters,a command filtered adaptive fuzzy control method based on symmetric time-varying full-state constraints is studied.The fuzzy logic system is used to deal with the uncertain nonlinear term in the FJM system model.On this basis,the time-varying symmetric barrier Lyapunov functions are used to verify that none of the system’s state variables exceed the time-varying constraint ranges.The command filtered backstepping technology with error compensation mechanism eliminates the influence of filtering error on system control performance.The stability is displayed through Lyapunov theory.The simulation results show that the trajectory tracking errors of two linkages in the two-link FJM system can be controlled within 0.0003 rad and0.0016 rad respectively,and the advantages of the method in this chapter are verified by comparison.(3)Based on the previous research,the event-triggered mechanism is introduced to further investigate the trajectory tracking control problem of the n-link FJM under the condition of asymmetric time-varying full state constraints.A command filtered eventtriggered adaptive fuzzy controller based on asymmetric time-varying full state constraints is designed by combining fuzzy logic system with the command filtered backstepping method.Therefore,the system communication resources can be well saved with the premise of ensuring good tracking performance,the stability of the system is demonstrated through Lyapunov theory.Finally,the simulation experiment of a two-link FJM system is carried out,and the results show that the method in this chapter can control the tracking errors of the two links within 0.007 rad and 0.0052 rad respectively,and can satisfy the asymmetric time-varying state constraints of the system.