Research on Control and Energy Efficiency Characteristics of Electro-Hydraulic Actuators for Servo Deep Drawing Dies

Improving energy efficiency while maintaining accurate force and displacement control is a key requirement for servo deep-drawing die-cushion systems. Electro-hydraulic actuators (EHAs), which combine the high power density of hydraulic transmission with the controllability of electric drives, provide an effective approach for improving the dynamic performance and energy efficiency of metal-forming equipment. This paper investigates the control and energy-efficiency characteristics of an EHA applied to a servo deep-drawing die-cushion system, with particular emphasis on the working mechanism of its hydraulic system, the AMESim-Simulink co-simulation control strategy, and the energy-efficiency distribution characteristics. Firstly, an electro-hydrostatic actuator (EHA) model composed of a permanent magnet synchronous motor, a fixed-displacement pump, valve block unit, accumulator, and single-rod double-acting hydraulic cylinder is established. The power flow relationship of the system in the four-quadrant working condition is analyzed, and the flow distribution characteristics of the main oil circuit, supplementary oil circuit, and bypass branch are studied. Secondly, a joint simulation platform is built based on AMESim and Simulink to achieve bidirectional coupling between the hydraulic actuator and the motor drive control system. In the speed control loop, the traditional PI and fuzzy PI control strategies are compared; in the position control loop, the PID control and sliding mode control strategies are simulated and analyzed. The results show that the fuzzy PI control has better dynamic regulation ability under load torque and speed step change conditions, which can reduce speed overshoot and shorten the regulation process; the position-control results under a step-displacement command show that the sliding-mode controller improves the transient response and steady-state tracking accuracy compared with the conventional PID controller. Finally, the system’s four-quadrant energy efficiency, motor efficiency, pump volumetric efficiency, and mechanical efficiency are analyzed from the perspective of energy conversion. The results show that the system efficiency is affected by load, actuator speed, motor speed, and pump pressure difference, and the efficient working area is mainly distributed in the medium-high speed and moderate load range.