Electric Power Steering (EPS)

Electric Power Assisted Steering, abbreviated as EPS, means Electric Power Steering. It’s also referred to as EPAS. Nearly all modern vehicles use Electric Power Steering. The fundamental purpose of any hydraulic steering system is to reduce the effort the driver needs to steer the vehicle, that is, the torque applied to the steering wheel, and this system uses an electric motor for the same purpose.

How Electric Power Steering Works

The steering angle sensor and torque sensor respectively measure the steering wheel’s position and the torque the driver applies to the steering wheel. This data is then fed into the Electronic Control Unit (ECU).

The ECU also monitors the vehicle’s overall speed. Based on this information, the ECU calculates the assist torque that needs to be applied, and accordingly signals the assist unit, i.e. the motor, to apply the desired torque to the steering gear.

electric power steering operating system how eps works

Depending on the vehicle’s speed, Electric Power Assisted Steering provides variable assist to the steering gear. At low speeds, the system operates at its maximum efficiency compared to high speeds.

eps electric power steering system parts — A typical EPAS (Babcox Media Inc.)

Fuel Savings

Electric power steering systems save fuel by eliminating the hydraulic pump’s constant load on the engine.

Speed-Sensitive Steering

EPS can be electronically tuned to feel lighter at low speed and firmer at high speed.

Easier Maintenance

Since it doesn’t require hydraulic fluid or a pump, EPS systems require less maintenance than conventional hydraulic steering.

Advantages of EPS:

It’s an extremely precise system, and therefore provides better control over the vehicle.
Since no fuel is needed to run the steering pump, it helps improve the vehicle’s fuel economy.
It’s a lighter system.
It’s more efficient than a hydraulic steering system.

Classification of EPS:

Depending on the position of the assist motor, EPAS is classified into four different types:

Column assist type: In this system, the assist unit is attached to the steering column.

Pinion assist type: In this system, the assist unit is attached to the steering system’s pinion shaft. Small cars in particular use this design.

Direct drive type: This system features a combined steering gear unit and assist unit.

Rack assist type: In this category, the assist unit is attached to the steering rack. It’s generally found in medium and heavy vehicles.

Related Questions

At low speed (like when parking), high assist is needed to turn the wheel easily, while at high speed, a very light steering feel could be dangerous. The system provides a safe and controlled feel in every situation by decreasing or increasing assist based on speed.

Hydraulic steering needs a pump that the engine constantly turns; this pump consumes power as long as the engine is running. In an electric system, the motor only engages when the wheel is being turned, which prevents unnecessary energy consumption.