Research On Disturbance Observer Based On Robust Control For Several Complex Systems With Intermittent Measurement Mechanisms

In the past four decades,the disturbance observer-based control method(DOBC)has been researched and applied in various industrial fields.Espe-cially with the advancement of science and technology and the development of network technology in the past decade,various control strategies,such as intermittent control,adaptive control,switching control,traction control,re-cursive design,sampled-data control,robust control,etc.,were introduced.Different control systems to suppress disturbance,and achieved a series of important results.This thesis focuses on three kinds of complex systems and studies the robust control problems based on disturbance observers,including the robust control problem of uncertain systems with external disturbances,the robust control problem of Lipschitz nonlinear stochastic systems with unknown external disturbances and robust control problems for stochastic time-delay systems with external disturbances.Compared with the tradition-al disturbance observer design method,the disturbance observer designed in this paper is intermittently measurable based on the state information of the system,which can truly reflect the fact that the system state information can-not be completely measurable due to data transmission delay,data packet loss,and limited communication bandwidth bytes in an actual network con-trol system.Therefore,the disturbance observer designed in this thesis has very important theoretical significance and application value.Its main work is as follows:(1)Study the robust control problem for a class of uncertain systems with external disturbances.Assume that the disturbances are generated by the exogenous system,and the state information is assumed to be available only for some non-overlapping time intervals.Different from the traditional disturbance observer,the proposed disturbance observer is modeled by the switching impulse method,which uses intermittent state data to estimate the disturbance.Based on the output of disturbance observer,a compound con-troller composed of intermittent state feedback controller is designed.The stability of the closed-loop system is analyzed by applying a piecewise-time-dependent Lyapunov function.Then the gain matrix of the disturbance ob-server and compound controller is obtained by solving a set of linear matrix inequalities(LMIs).(2)The robust control problem of a class of Lipschitz nonlinear systems with unknown external disturbances is studied.It is assumed that the external disturbances are generated by the exogenous system and the state information is only available at partially broken time intervals.A compound controller us-ing intermittent state feedback is proposed.The controller consists of an in-termittent state feedback controller and a compensation controller(output of a disturbance observer).The stability of the closed-loop system is analyzed by used the piecewise time-dependent Lyapunov function simultaneously com-bined with convex combinations,bilinear matrix inequalities(BMIs)and oth-er techniques,and a new design strategy for the disturbance observer is ob-tained.Then,the inequality is deduced from the matrix inequality.Sufficient conditions for the existence of a compound controller.(3)The robust control problem for a class of nonlinear stochastic time-delay systems with external disturbances is studied.Assume that the state in-formation of the systems is available on some non-overlapping time intervals.Based on this,the aperiodically intermittent control strategy based on distur-bance observer guarantees the exponential stability of the mean square expo-nent of the composite stochastic time-delay system proposed in this thesis.At the same time,for time-varying delays systems,this chapter constructs a piece-wise time-dependent Lyapunov functional to fully exploit the dynamic characteristics of the interference error system,and based on the constructed Lyapunov functional,the robust control problem of stochastic time-delay sys-tems with external disturbances is ingeniously translated into a set of LMIs feasibility problems.Then using the BMIs technique to deal with the inequal-ity,the gain matrix of the disturbance observer and compound controller is obtained.