Invariance Compensation Pid Control for a Proportional Valve-controlled Asymmetric Cylinder System

Abstract A load flow model of a proportional valve-controlled asymmetric cylinder system is developed to assess inconsistent dynamic properties. The load flow property is analyzed, and the basic state is defined for the system. In addition, an invariance compensation method is proposed that considers the structure and load effect. If any asymmetric state of the system is equivalent to the basic state through invariance compensation, then the symmetrical load flow property is obtained, which is verified through simulation. Proportion–integration–differentiation (PID) control based on invariant compensation is used in the system, and the dynamic characteristics are almost the same. The experimental results show that the flow error between the load state and the basic state is less than 11% in the linear region of the proportional valve for the asymmetric cylinder system when the system load pressure is less than half of the pump pressure. The response error is approximately 0.04 s between the forward and reverse directions under the given asymmetric load.