Simultaneous Estimation of States and Unknown Inputs for Linear Systems Based on Auxiliary Outputs
基于辅助输出的线性系统状态和未知输入同时估计方法

This paper considers the problem of simultaneously estimating the states and unknown inputs for linear systems when the so-called observer matching condition is not satisfied. Based on the relative degree of the output with respect to the unknown input, a kind of auxiliary output vector which may satisfy the observer matching condition is constructed. To deal with the unknown information contained in the auxiliary output vector, a kind of high-gain observer is developed. The high-gain observer is able to estimate the auxiliary output vector and its derivative. Then, we construct a reduced-order observer which can track the system's states based on the estimation of auxiliary output vector. Moreover, through employing the estimation of auxiliary output vector's derivative, unknown inputs can be estimated. The simulation results of a real model show that the proposed method is effective.