An energy-saving robust motion control of redundant electro-hydraulic servo systems

The main concern of this paper is the study of energy saving for a class of Electro-Hydraulic Servo Systems (EHSS)s with application of motion tracking. To achieve energy conservation, considering the actuation demands, a proportional relief valve (PRV) is used for pressure regulation in the power supply. A force feedback also used to evaluate the effects of external forces on required pressure of the actuation. Considering the tracking demands, a proportional directional valve (PDV) is used for flow regulation. The proposed configuration makes an analytical redundancy in control algorithm based on the operation of the PDV and the PRV. In fact, multiple situations of the control valves exist for position tracking. To design a control algorithm with the ability of satisfying all control objectives, four operation modes including both active and passive modes are defined. Then an optimal robust control approach is synthesized for each mode and a switching strategy between modes is devised. In addition, the force feedback is used to benefit from the effect of external force on motion tracking, within the passive modes. Finally, experimental results verify the stability and the performance of the proposed system in the presence of model uncertainties.