Steering gear is an important mechanical equipment to control and manipulate the deflection of rudder blade. In order to sail safely and smoothly and reach the destination or the scheduled berth quickly, the ship must have good maneuverability besides the propulsion of the main engine, that is, the ability to maintain or change the course according to the driver's intention. At present, the method of steering the ship's course varies with different ship equipment, and the most common application is to use the rudder installed at the stern to steer the ship's course. A complete steering gear (hereinafter referred to as steering gear) consists of remote control mechanism, steering gear power machinery, steering mechanism and rudder. In addition, the control device is also provided with a feedback device (rudder angle indicator) for reporting the actual angular position of the rudder blade, the maximum rudder angle limiting device and the emergency steering mechanism.