This term covers all combinations of electrical (electronic) signal processing with hydraulic drives. These combinations can be divided into three groups:
- Electro-hydraulic technology in which hydraulic valves are opened or closed by switching solenoids. The signal processing is generally undertaken using relay technology (Figure E 22 a).
- Electro-hydraulic control technology with continuously adjustable valves (proportional valves). This technology permits continuous adjustment to changing setpoints and therefore better compensation to the progression of processes. The setpoints are retrieved via the machine controls or via a PLC. The signal processing is undertaken electronically (b).
- Electro-hydraulic control technology with continuously adjustable valves (high response proportional valves, servo valves). This technology operates with continuous sensors and electronic control amplifiers. The program is executed via the machine controls (NC, CNC, DNC).
Figure E 22: Electro-hydraulic systems; a) in relay technology, b) in proportional technology