An energy-saving position control strategy for electro-hydraulic servo system with parallel dual valves

Proportional directional control valves (PDCVs) with large flow and high control accuracy in electro-hydraulic servo systems(EHSS) are usually expensive, at the same time, the demand for energy-saving in EHSS is increasing rapidly. In order to solve the cost and achieve energy-saving, an energy-saving position control strategy for EHSS with parallel dual valves is designed. First, the mathematical model of the system is established. Secondly, to obtain a high position tracking performance, the basic controller of the system was designed by back-stepping control method to solve the virtual control law. Then, a control distributor was designed to obtain the smooth switching strategy between different modes. Next, the main approach to energy-saving was to decrease the supply pressure and supply flow as much as possible. A nonlinear set of laws are derived to vary the supply pressure according to the required forces during position tracking, while a servo motor controller was designed for the fixed displacement pump to vary supply flow according to the required flow. Experiment results show that, the cheap parallel dual-parallel PDCVs with common performance can achieve high position tracking performance of EHSS to replace an expensive high performance PDCV, and the effect of energy-saving is obvious.