Comparison of Sliding Mode Controller for Classical and Direct Driven Electrohydraulic System

In this paper, a novel energy-efficient Direct Driven Hydraulic (DDH) drive is made in parallel with a classical valve-controlled proportional electrohydraulic system. In the proposed concept asymmetrical hydraulic cylinder is controlled with two reversible pumps directly connected to a servo motor. Due to direct control of the oil flow, such system provides higher energy efficiency in comparison to a valve-controlled hydraulic system. The experimental setup is designed with the possibility of easy switching between both systems, which enables an exact comparison of the experimental results. Sliding Mode Controller (SMC) is designed for the DDH system and also for the classical proportional electro-hydraulic system. A comparison study of two systems is done based on the experimental results obtained with the SMC while reference results are obtained with a widely used PID controller. Parameters for the PID controller are obtained with the Ziegler-Nichols method. The same parameters are used for both controllers in all test cases. The performance and energy efficiency of the proposed system is evaluated through a step and sine wave reference signal with different payloads varying from 0 to 200 kg with 20 kg increments. Additionally, system performance is evaluated based on six parameters calculated from the system response while energy efficiency is calculated based on input and output powers of the systems.