An observer-based approximate optimal tracking control for nonlinear systems with persistent disturbances
基于观测器的受扰非线性系统近似最优跟踪控制

The optimal output tracking control(OOTC) problem for a class of nonlinear systems with persistent distur-bances is considered.An approximate design algorithm of the OOTC law is presented in the finite time domain.Firstly,the two-point boundary value(TPBV) problem,which is derived from the original OOTC theory,is transformed to a coupled nonlinear TPBV problem in state vectors and adjoint vectors.The coupled TPBV problem is further transformed to two decoupled linear differential sequences via a recently developed successive approximation approach(SAA).By iteratively solving the adjoint vector sequence,the OOTC law can be obtained,which consists of analytic linear feedforward and feed-back terms,as well as a nonlinear compensation term determined by the limit of the adjoint vector sequence.Furthermore,a reduced-order reference input observer and a reduced-order disturbance observer are constructed in order to solve the physically realizable problem of feedforward control.Finally,simulation examples show the effectiveness of the presented approach.