How Does Electric Power Steering Work?

Electric power steering (EPS) systems have largely supplanted older hydraulic setups, offering better efficiency, easier calibration and integration with driver-assist technology. Below we’ll explore what EPS is, how it functions, its key components, advantages compared with hydraulic systems, and what this means for drivers and vehicle engineers.

What is Electric Power Steering (EPS)?

Electric power steering (also referenced as electric power-assisted steering or EPAS) replaces the traditional hydraulic pump-driven power assist with an electric motor plus sensors and control electronics.
In short: rather than a belt-driven hydraulic pump constantly providing pressure, an EPS system only consumes power when steering assistance is required.
This makes EPS more efficient and allows for tailored assist behaviour depending on vehicle speed, steering demands and even driver preferences.

Key Components of an EPS System

Here are the primary building blocks of how an electric power steering system works:

• Torque sensor / Steering input sensor: Measures how much force or torque the driver is applying to the steering wheel (or column).
• Steering angle / vehicle speed sensor: Provides data on how much the wheels are turned, as well as the vehicle’s speed, which influences the amount of assist.
• Electronic control unit (ECU): Computes how much assistance the motor should provide based on inputs (torque, angle, speed) and system state.
• Electric motor / actuator: Provides the actual assist torque, coupled to either the steering column, the pinion gear, or rack (depending on variant) to reduce driver effort.
• Mechanical linkage: Maintains the mechanical connection between the steering wheel and the wheels (in most EPS systems). If the assist fails, you still have steering—just heavier.

Here’s a simplified step-by-step explanation of how an EPS system behaves when you steer:

1. You turn the steering wheel; this mechanical action is transferred down the column or linkage to the steering gear.
2. The torque sensor detects the driver’s steering effort and sends a signal to the ECU.
3. At the same time, the vehicle speed sensor and other sensors provide data to the ECU (for example: low speed vs high speed).
4. The ECU calculates how much assist torque the vehicle should provide — for example, at low speeds more assist (lighter steering), at higher speeds less assist (for better feel and stability).
5. The electric motor is activated and supplies assist torque via its mechanical coupling (column, pinion, or rack) to lighten the load on the driver’s arms.
6. The driver steers, aided by the motor. If the system detects a fault (sensor, motor, or controller), the assist can be reduced or disabled, but mechanical steering remains.

Why Is EPS Better Than Hydraulic Power Steering?

The move from hydraulic to electric power steering brings several advantages:

• Energy Efficiency: Hydraulic systems require a pump driven by the engine continuously, leading to “parasitic” losses. Electric systems only draw power when the motor is assisting.
• Adaptability & Feel: Because electronics control the assist, the system can vary the level dynamically (more assist at low speeds, less at high speeds) improving both maneuverability and high-speed stability.
• Simpler Packaging & Maintenance: Fewer parts (no hydraulic hoses, fluid, pump) means lower maintenance and fewer fluid leaks.
• Integration with Advanced Systems: EPS systems integrate more easily with driver-assist features (lane keeping, autonomous steering) because they are electronically controlled.

What It Means for Drivers & Vehicle Designers

For drivers: smoother, lighter steering effort at low speeds (parking, city driving), more stable and precise feel at higher speeds. Lower fuel consumption and potentially lower maintenance costs.
For vehicle designers (especially if you’re dealing with conversions, electric vehicles, or custom builds): EPS offers a modular, tunable steering assist solution that fits well with electric drivetrains, battery systems and advanced electronics. You can calibrate the assist curve to match vehicle weight, chassis, speed, etc.

Potential Limitations / Considerations

No system is perfect. Some things to keep in mind:

• If the EPS motor or electronics fail, you revert to manual (non-assisted) steering which requires more effort. Designers must ensure safe fallback.
• Steering feel / feedback: Some enthusiasts feel that electric systems can lack the “organic” feel of a well-tuned hydraulic system if not calibrated well.
• Integration and calibration: For custom vehicles or conversions (which sounds relevant for your work), the ECU calibrations, torque sensor alignment, motor selection and mechanical coupling need to be done well to ensure optimal feel and behaviour.
• Compatibility with electric systems: On vehicles with 12 V, 48 V or high-voltage systems, ensuring your EPS design works with your electrical architecture is important (especially given your interest in converting vehicles).

As  a conclusion

In summary, EPS uses sensors to detect your steering input, an ECU to calculate the required assist, and an electric motor to deliver that assist—replacing older hydraulic components. The result: better efficiency, improved adaptability, easier integration into modern vehicle systems and reduced maintenance. For anyone involved in vehicle conversions, house-built chassis or electric vehicle design (like your off-road vehicles), understanding EPS is key to delivering quality steering performance and driver feel.

Feel free to conact CMVTE if anything interests you.