Rejecting the effects of both input disturbance and measurement noise: A second‐order control system example

Abstract

SummaryThis article originates from the well‐accepted observations in practice: rejection of both input disturbance and measurement noise is practically important for high‐precision tracking control, and the classic estimators, such as the uncertainty and disturbance estimator (UDE) and disturbance observer, are proven to be inherently sensitive to measurement noises. Motivated by these observations, we develop a robust control solution and demonstrate the possibility of unifying the design of noise estimator (NE) and UDE for a class of second‐order systems. Interestingly, the NE and UDE have three important features in common: (i) the designs are based on system model and reliable state measurement; (ii) a first‐order filter is used to ensure that the design is physical realizable, rather than to filter out undesired signals; (iii) the filter parameters are readily determined by an introduced singular perturbation parameter. The performance of UDE is improved when augmented with NE to reject measurement noises. Then, a simple mapping for parameter tuning is presented, by which the estimation performance can be explicitly analyzed using the singular perturbation theory. Comparative simulation and experimental studies show that the proposed NE+UDE‐based solution is not only less sensitive to measurement noise than the classic UDE‐based control, but also able to deliver superior trajectory‐tracking performance over other robust output feedback control approaches.