Working Principle:​ The electronic controller sends an electrical command signal to the torque motor servovalve inside the TM-55 actuator; the servovalve generates a differential pressure that drives the second-stage spool valve, regulating hydraulic oil flow to both ends of the double-acting servo piston. Piston motion rotates the final output shaft, thereby driving the metering sleeve of the 3103 gas valve to change its opening. The built-in electrical position sensor continuously detects actuator/valve position and feeds it back to the controller, forming a high-accuracy closed-loop position control. Upon loss of control power, the spring-loaded mechanism of the actuator pushes the valve toward the minimum-fuel position, achieving fail-safe protection.