PLC/PAC/PC - based control of an electro-hydraulic servo system

Selection of an appropriate control system is an important decision in the process of designing an electro-hydraulic servomechanism. Nowadays, end- users have a number of options for the choice of control systems and it can sometimes be a bit confusing. The most common applied control system today are the Programmable Logic Controller (PLC), the industrial PC-based Data Acquisition (DAQ) system, and more recently the Programmable Automation Controller (PAC). In this paper, all three of these control methods will be discussed on the example of position control of electro- hydraulic servo mechanisms. The experimental system consists of a main cylinder which is controlled by using a proportional directional control valve, while disturbance (i.e. reaction force) is generated by using a load cylinder with a pressure control valve.