Nowadays, many new cars are equipped with an EPS (Electronic Power Steering) system to reduce the effort applied by the driver on the steering wheel. This system uses a torque sensor, the sensor senses the movement of the steering wheel as well as the movement of the vehicle.
EPS uses three vital components for actuation. ECU, a motor and a reduction gear.
The ECU receives a signal from the torque sensor and converts this signal into the force required. The output of the ECU is fed to the motor, which produces a turning force according to the signal from the ECU. A reduction gear is used to convert a small amount of force into a large amount and transfer it to the steering mechanism. The force applied by the reduction gear totally depends upon the vehicle speed.
There are two different types of EPS system; depending upon the location and construction of the reduction gear. The first type is a Column type in which reduction gear is located directly under the steering wheel. Pinion type is the one in which, reduction gear is directly attached to the pinion of a rack and pinion setup.
The main components of an Electric Power Steering system are:
Torque sensor: Torque sensor is used to measure the torque which is applied to the steering wheel in the power steering system. Torque sensor decides the amount of force and direction required to actuate the motor with the help of torque that is applied to the steering wheel.
The torque sensor detects the twist of the torsion bar and converts this twist into an electric signal which is sent to the ECU. The ECU monitors this signal and gives output in terms of the amount of power required by the DC motor, to operate the steering wheel.
Steering Gear: In the steering mechanism, the torsion bar is connected to the pinion via input shaft. When the driver steers the steering wheel, the torque of the steering wheel is transmitted to the input shaft via a pinion. This causes the input shaft to turn in its place and also rotate the torsion bar.
DC motor: A DC motor is located in between the worm gear and steering column shaft. It is used to develop torque and transfer it to the steering column shaft.
CPU: It is a vital component of EPS. It receives signals from various sensors and according to those signals, it analyzes the data and outputs the proper force needed to operate the actuator.
EPS systems offer reduced steering effort, increased fuel economy and more reliability. However, they can be more expensive than the traditional belt-driven hydraulic power steering we’re all used to.