The current study aims to improve the performance of the electrohydraulic servo system (EHSS) by increasing the volumetric efficiency of the pump and reducing electrical power consumption to a minimum value. An experimental setup has been designed and built to control the cylinder position using a programmable logic controller to provide the appropriate motor speed from the AC drive to control the velocity of the hydraulic actuator; the induction motor is driven by an AC drive using a tune proportional-integral-variable frequency drive (TPI-VFD) space vector modulation (SVM) hybrid technology. Theoretically, it was analyzed and simulated by MATLAB, which showed that the starting current was reduced by 81% compared to the traditional system. Also, the settling time of the system decreased to 0.35 s to reach a steady state with a minimum error of 0.03 and an overshoot of 0.3%. On the other hand, the experimental results of the EHSS show that the three-phase induction motor with a closed-loop speed control AC drive with a programmable logic controller PLC based system is the best case for determining the appropriate operating speed. The optimum speed, frequency, and voltage were 1325.3 rpm, 46.6 Hz, and 354.16 V. In addition, enhancement is achieved in closed-loop VFD-PLC, where at 6.5 bar pressure and 3.4 LPM flow, the volumetric efficiency after the pump improves to 98.6% while it reaches 96.3% before the cylinder at a flow rate of 3.32 LPM. Finally, in the closed-loop VFD-PLC in the expansion stroke, the rated electrical power consumption of the three-phase IM decreased to 532 W at the speed of 1325.3 rpm, resulting in energy savings of 20.6%.
Hassan et al. (Thu,) studied this question.