Electric Power Steering System
Electric power steering (EPS) uses an electric motor to steer movement, unlike hydraulic systems which use hydraulic pressure from the engine pump. The pump runs continually whether the steering wheel is turned on or not, hence affecting vehicle fuel efficiency.
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EPS supplement torque applied on the steering wheel. It eliminates some components found in hydraulic power steering systems including pump, fluid, hoses, pulley and drive belt. Therefore, electric power steering systems tend to be much lighter and smaller than hydraulic systems.
This steering system does not use any power when no steering is required. It is more energy efficient compared to a hydraulic power steering system. In fact, it has a power assistance that reduces in high speed and increases in lower speed.
The electric power steering, on the other hand, has better fuel economy because the engine load is reduced to when the steering is turned. The load is also applied when the steering wheel is turned by drag. A drag occurs when the alternator places the load on the engine when more electric load is needed.
How it works
The system consists of an electric motor that is mounted on the steering column or gear. This motor applies torque to the column enabling the drive to turn a steering wheel.
The electronic control unit determines the power required to steer a wheel based on torque, vehicle speed and positions of the steering wheel. The motor uses force applied by the driver to rotate the steering wheel hence reducing the torque required by the driver.
Sensor use input from the driver and position of the steering wheel to change the direction of the vehicle. Control sensors apply torque through an electric motor. If the wheel is steady, the system will not offer any assistance.
In addition to better fuel economy EPS can be programmed to offer various qualities. For instance, assistance can be increased during parking and reduce in a highway to boost stability. Similarly, the steering system can be programmed to support safety systems such as stay on lanes. Similarly, EPS can help to dampen vibrations and in camber control.
EPS system powers the motor only when it is necessary to do so. This improves efficiency and reduces fuel consumption. The systems can be tweaked using software to control the ECU. EPS also integrates a failsafe mechanism that disconnects power from the motor if there is a fault in the Electronic control unit. It removes mechanical linkage leading to a purely electronic controlled system
EPS is also able to compensate for single-sided forces for instance in during a flat tire. It also works together with electronic stability control to t steer in emergency maneuvers.
Types of EPS
There are four types of EPS which are based assist motor position. They include
- Column assist (C-EPS)
- Rack assists (R-EPS)
- Direct drive (D-EPS)
- Pinion assist type (P-EPS)
Signs of a faulty EPS
- Illuminating engine light
- Stiff wheel
Read more about your car’s suspension and steering systems: