EPS (Electric Power Steering) system replaces hydraulic power assistance with electronic control. It works jointly with torque sensors, vehicle speed sensors, ECU, assist motors and reduction mechanisms to realize accurate, adaptive and high‑efficiency steering assistance.
Main components of EPS electric power steering:
Sensors:
Torque Sensor: Detects the magnitude and direction of torque applied by the driver on the steering wheel, converts the signal into voltage and transmits it to the control unit.
Vehicle Speed Sensor: Monitors vehicle driving speed to adjust assist force (higher assist at low speed, lower assist at high speed for better stability).
Steering Angle Sensor (partial systems): Detects the rotation angle and position of the steering wheel.
Control Unit (ECU):
Receives signals from sensors, calculates required assist torque and direction according to preset control strategies (e.g. assist characteristic curve).
Drives the motor for steering assistance, and integrates functions such as fault diagnosis and safety protection (degraded operation under overheating or abnormal voltage).
Assist Motor:
Permanent magnet DC motors or brushless motors are commonly used to output auxiliary torque according to ECU commands.
It features high reliability, fast response and low noise.
Reduction Mechanism:
Reduces motor speed and amplifies torque via worm gear, planetary gear and other devices, and transfers motor output to the steering system.
Mechanical Steering Gear:
Retains traditional mechanical structures such as rack‑and‑pinion to ensure manual steering is available when EPS fails.
Additional Components (partial systems):
Electromagnetic Clutch: Cuts off connection between motor and steering column under system fault or high‑speed condition, switching to manual mode.
Redundant Design (high‑level systems): Such as dual‑MCU, redundant sensors or dual motors to improve safety for autonomous driving scenarios.
Working Process of EPS Electric Power Steering
When the driver turns the steering wheel, the torque sensor detects steering torque in real time, and the vehicle speed sensor sends speed signals to ECU simultaneously.
Based on parameters including torque and vehicle speed, ECU determines target assist current via preset algorithms (e.g. look‑up table or PID control).
ECU drives the motor to output corresponding torque. The torque is amplified by the reduction mechanism and acts on the steering system to assist the driver in steering.
Under intelligent control modes:
Assist Control: Provides basic steering assistance;
Return‑to‑center Control: Assists fast steering‑wheel return at low speed and applies damping to prevent excessive return at high speed;
Damping Control: Suppresses interference to steering wheel caused by road vibration.
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