servoventil

Servoventil, or servo valve, is a high-precision hydraulic valve that converts an electrical control signal into a precise hydraulic output. It forms the core of closed-loop hydraulic control systems, enabling accurate positioning, force, and speed of hydraulic actuators in industrial machines, aerospace, and robotics.

Operation is based on electrohydraulic control. An electrical input signal is amplified by a servo amplifier and used to move a pilot or main spool inside the valve. The resulting pressure differences regulate the flow to the actuator. A feedback mechanism, which may be a mechanical linkage or an integrated position sensor, provides a signal proportional to the valve or actuator position. The servo amplifier compares the feedback signal with the command and adjusts the input to minimize error, achieving precise closed-loop control.

Common configurations include two-stage servo valves, where a small pilot valve controls a larger main stage, and single-stage variants. Valves can be linear (spool) or rotary and may use analog or digital control. Two-stage designs are prevalent because they combine high gain with good stability and bandwidth.

Applications span machine tools, aerospace flight and hydraulic control systems, robotic manipulators, injection molding, and testing apparatus. Performance is characterized by bandwidth, gain, resolution, and minimal hysteresis or leakage. Servo valves offer high dynamic response and accuracy but require clean hydraulic fluid, proper filtration, temperature control, and periodic calibration. Potential failure modes include spool sticking, leakage, coil or sensor faults, and contamination-related wear.