Force Control of Electro-Hydraulic Servo System Based on Load Velocity Compensation

In an electro-hydraulic servo control system, the force servo system is an important component. However, due to the nonlinear characteristic of hydraulic systems, traditional control methods cannot achieve satisfactory control performances. To deal with this issue, a load velocity compensation algorithm based on the structural invariant principle is proposed in this paper. First, the theoretical analysis of the hydraulic and cylindrical force control system is presented, and the mathematical model of the force control system is established. Then the open-loop frequency response characteristics of the system are analyzed, in which the Bode diagram shows that the bandwidth of the system is obviously expanded after adopting the load velocity compensation algorithm. Finally, a practical hydraulic and cylindrical force servo system is introduced to validate the feasibility of the proposed controller, the experimental results demonstrate that the proposed method can improve the performance of force control and eliminate the influence of load stiffness on the dynamic characteristics of the system through a set of comparative experiments with different elastic loads.