Hydraulic drive unit operated electrically using a stepper motor or DC motor with integrated control unit (following control valve) and integrated, mostly mechanical feedback. The following control valve provides, on the one hand, the synchronisation between the drive motor and the hydraulic motor and, on the other hand, an increase in the output torque of up to 104 times (Figure E 20).
On the usage of a DC motor as an analogue setpoint generator, an external speed control circuit is required that can be avoided on the usage of a digitally operated stepper motor.
Figure E 20: Electrohydraulic torque amplifier, stepper motor-controlled