A Novel Control Strategy for an Energy Saving Hydraulic System With Near-Zero Overflowing Energy-Loss

The relief valve overflowing energy loss is considered impossible to solve. This paper proposes a new type of proportional relief valve (PRV) with a hydraulic energy regeneration unit (HERU) connected to its outlet. The mathematical model of the proposed PRV is set up, and its stability is analyzed. A control strategy is put forward for designing the working modes which are based on the pressure of the hydraulic accumulator. The simulation model and the test rig, where a hydraulic accumulator is used as a HERU, are established to verify the effectiveness of the control strategy and energy savings of the proposed PRV. The results show that the system can switch among energy regeneration, energy release, and traditional modes according to the hydraulic accumulator pressure, indicating that the proposed control strategy works well. During the energy regeneration mode, the hydraulic accumulator is charged and the PRV inlet pressure decreases only slightly, indicating the HERU has little influence on the PRV working performance. During the energy release mode, the hydraulic accumulator is discharged and the PRV inlet pressure increases to its preset value. Both during the regeneration and release modes, the driving electric motor consumed less energy. Higher hydraulic accumulator pre-charging pressure can achieve higher energy regeneration efficiency, whereas lower hydraulic accumulator pre-charging pressure can regenerate more overflowing energy.