Design and Analysis of Observer-Based Full-Closed Loop Position Control for Servomechanism With Elasticity

It is cost-efficient to attain high-performance position control on the semiclosed loop structure. However, the control deviation exists on the load side due to the low-stiffness shaft. This article constructs an observer-based full-closed loop position control (OFPC) using a state feedback method that offers the advantage of flexible pole assignment and high positioning accuracy. The utilization of an observer will introduce the nonlinear elements in the closed-loop system, which causes a limit cycle potentially. To solve this issue, the disturbance function has been developed, and the limit cycle phenomenon induced by motor and load friction has been studied emphatically via the describing function approach. Furthermore, this article presents an effective control gain boundary to prevent the load side limit cycle, and offers an adaptive compensation algorithm of motor friction to suppress the residual limit cycle. The effectiveness of the proposed strategy is validated on the linear tooth belt drive. The experimental results indicate that the OFPC scheme can achieve relatively high positioning performance.