Position Control of Direct Driven Hydraulic Drive

This paper investigates directly driven hydraulic setup for non-road mobile machinery (NRMM) application. The purpose of this research is to utilize the excellent control capabilities of modern electric drives in electro-hydraulic systems, create direct drive position control for the hydraulic cylinder and verify the results by measurements. The control is implemented directly with a motor drive without conventional control valves. Speed and position of the double-acting cylinder is determined by in-coming oil flow from the pump, out-coming flow of hydraulic motor and angular speed of the electric motor with a single feedback from motor rotor encoder. Empirical results proved that the control suits NRMM application. The achieved maximum final position error of 3.1 % of the position control for tested cycle is fulfilling required accuracy.