Design and control of a closed-loop hydraulic energy-regenerative system

In this study, a novel hydraulic energy-regenerative system was presented from its proposal through modeling to its control. The system was based on a closed-loop hydrostatic transmission and used a hydraulic accumulator as the energy storage system fabricated in a novel configuration to recover the kinetic energy without any reversion of the fluid flow. The displacement variation in the secondary unit was reduced, increasing the uses of several types of hydraulic pump/motors. The proposed system was modeled based on its physical attributes. A hierarchal control system was implemented and focused on the design of an adaptive fuzzy sliding mode control for speed control of the secondary unit. The energy utilization and the influences on the energy-recovery potential of the system were analyzed. Simulation and experiments were performed to evaluate the validity of the employed mathematical model and the effectiveness of the control system. The experimental results indicated that the designed system was effective and that the round trip recovery efficiency varied from 22% to 59% for the test bench.