Research On Active Anti-disturbance Control For Port-controlled Hamiltonian Systems

As an important class of nonlinear systems,the Port-controlled Hamiltonian(PCH)system has a clear physical meaning structure and widely exists in many fields such as life science,physical science and engineering science.The PCH system is the extension of the Euler-Lagrange system,many engineering systems,such as celestial mechanics and biological engineering,can be described by the PCH system and have been extensively studied.Through the tireless efforts of experts and scholars,Hamiltonian system theory has been a very significant research direction of today's nonlinear scientific research.In practical engineering systems,disturbances(including parameter perturbations,unmodeled dynamics and external disturbances)are ubiquitous,which seriously deteriorates the control performance of systems.In order to improve the precision of the control system,disturbance rejection control has become a core technique in the design of the control system.Active anti-disturbance control(AADC)is a meaningful disturbance rejection control frame: it employs disturbance observer to estimate disturbance,and then introduces the disturbance estimation to compensate the disturbance in a feedforward way,and finally constructs a composite controller by combining the feedback controller.AADC can significantly improve the disturbance rejection performance of closed-loop system,which not only has been widely concerned and recognized by the control theory community,but also has been successfully applied in industrial processes.As for the adverse effects caused by disturbances in PCH systems,some problems on AADC are studied in this dissertation.The contents mainly involve global stabilization for a class of PCH systems with matched disturbances,global simultaneous stabilization for a class of two PCH systems with matched disturbances,global output regulation for a class of PCH systems with mismatched disturbance,and protocol design for group output consensus of a class of PCH multi-agent systems with matched disturbances.The main research results and contributions of the dissertation are summarized as follows:(1)For a class of PCH systems under matched disturbances,two composite anti-disturbance control schemes on stabilization and finite time stabilization of Hamiltonian system are presented.Firstly,based on the damping injection method,two baseline feedback controllers are designed for the nominal PCH systems,respectively.Secondly,the nonlinear disturbance observer(NDOB)/ finite time disturbance observer(FTDO)is introduced to estimate the disturbance for disturbed Hamiltonian system and further two feedforward compensation control are designed.Thirdly,the composite control scheme is presented by combining the first baseline feedback control with the feedforward compensation control based on NDOB,and the finite time composite control scheme is designed based on the second baseline feedback control,the feedforward compensation control based on FTDO,and finite time control technique.Under the two composite control strategies,the global asymptotic stability and global finite time stability of the closed loop system are proposed,respectively.Finally,the two composite control strategies are applied to the disturbed circuit system,and the proposed methods are verified by numerical simulations.The simulation results illustrate that the proposed control approaches not only improve the anti-disturbance control performance of the closed-loop system but also guarantee the property of the nominal performance recovery.(2)For simultaneous stabilization and finite time simultaneous stabilization problem of a class of two PCH systems with matched disturbances,two composite control schemes are proposed.Firstly,based on the structure of Hamiltonian system,two nominal PCH systems are combined together to generate a globally asymptotically stable/ finite time stable augmented PCH system by designing an output feedback controller/finite time output feedback controller.Secondly,to estimate disturbances effectively,it is essential to design the NDOB/ FTDO and further two disturbance compensation controllers are designed based on the estimation information.Then,a composite simultaneous controller is developed based on the output feedback part and the disturbance compensation part based on NDOB,and a finite time composite simultaneous controller is designed by combining the finite time output feedback part,the disturbance compensation part based on FTDO with the finite time control technique.Under the two composite control strategies,the global asymptotic stability and global finite time stability of the closed loop augmented system are proposed,respectively,i.e.,the two composite control strategies can simultaneously stabilize and finite time simultaneously stabilize two Hamiltonian systems subject to matched disturbances,respectively.Finally,to verify the validity of the proposed composite strategies,the numerical simulations are carried out.Simulation results illustrate that the proposed composite control approaches can not only simultaneously stabilize and finite time simultaneously stabilize two disturbed PCH systems but also guarantee the the property of the nominal performance recovery.(3)For global output regulation problem of two order and high order PCH systems with mismatched disturbance,two composite control strategies are developed.Firstly,based on the damping injection technology,two baseline feedback controllers are designed for the nominal PCH systems,respectively.Secondly,considering the influence of mismatched disturbances on the system,the FTDO/ NDOB is designed to estimate disturbances accurately.Based on the disturbance estimation information and a coordinate transformation/ a series of coordinate transformations,the system with mismatched disturbance is transformed into a matched disturbance system,and then two disturbance compensation controllers are designed.Thirdly,two composite controllers are designed by combining baseline feedback controls with the disturbance compensation controls,and the composite control schemes can not only suppress the influence of mismatched disturbance on system outputs,but also ensure the asymptotic convergence of system outputs.Finally,an example of a permanent magnet synchronous motor and a numerical example are given and simulation results demonstrate the effectiveness and superiority of the proposed composite control strategies.(4)For a class of PCH multi-agent systems with matched disturbances,a composite control method is designed to study the group output consensus problem.The composite distributed control protocol is developed by combining the energy shaping and damping injection technique,the FTDO technique and distributed protocol together,which makes the closed-loop Hamiltonian multi-agent systems achieve the consensus of the group output.At the same time,more kinds of disturbances can be estimated accurately via the FTDO and the composite control protocol is able to eliminate the disturbances' influence from the output channels.This control scheme exhibits not only better robustness against disturbance,but also the nominal system recovery performance.An illustrative example reveals that the designed control protocol can not only make the multiagent system achieve the consensus of the group output,but also has better anti-disturbance performance.