A steering actuator is a device used to assist with the steering of a vehicle. The most common type of steering actuator resembles a double-ended, hydraulic ram that is able to push out both ends of the device. When the actuator is mounted to a chassis, the rams on either end of the actuator push against the steering linkage, effectively aiding in the steering of the vehicle. Sensors located on the steering linkage use computer assistance to activate the actuator and apply the correct amount of steering assistance or hydraulic pressure.
Nearly every type of vehicle, from sports cars to boats and farm tractors, uses a steering actuator to assist in the turning of the vehicle. Similar to a power-assist, hydraulic cylinder used on conventional steering-box equipped vehicles, the actuator is designed to work with rack-and-pinion steering systems. In some rear-wheel steer applications of four-wheel steer vehicles, the actuator works unassisted in steering the rear wheels. In a marine application, the steering actuator is typically mounted near the rear of the vessel and applies steering pressure to the outboard boat motor. This pressure causes the motor to pivot more easily in its mount, thereby allowing the operator to steer the boat using much less physical effort.
As the vehicle's steering wheel is turned, a sensor detects the movement and the direction of the movement, which sends a signal to the computer system. The computer reads several sensors to calculate the vehicle speed, the amount of effort that is being applied to the steering wheel and the gear that the transmission is being operated in. With this information gathered and processed in a fraction of a second, the computer signals the steering actuator to apply a specific amount of pressure in one direction or another to ease the steering system pressure that is being exerted against the steering system. In the case of a farm tractor, the steering may be requiring assistance due to the tires being submerged in deep mud, sand or soil.
Monitoring the vehicle's speed is essential on four-wheel steer vehicles and sports cars. If the computer was to apply even the slightest amount of excessive steering pressure on the steering system at high speeds, the vehicle could potentially snap out of control and crash. Most actuators rely on restrictive valves inside of the actuator body to prevent the application of excessive pressure at high speeds.