Overview of Electric Power Steering Systems
1. Basic Structure and Principle of EPS
EPS uses an electric motor to assist the driver's steering operation. Depending on the location of the motor in the EPS model, different EPS structures exist, mainly including: Column-EPS, Pinion-EPS, and Rack-EPS (i.e., column, gear, and rack).
2. EPS Components
EPS consists of a torque sensor, ECU, power steering motor, reduction mechanism, and mechanical steering mechanisms such as gears and racks. The purpose is to understand the working principle of each electronic component.
The torque sensor receives the steering wheel angle and torque signals. After quantization via an analog-to-digital converter (ADC), the signals are sent to the MCU in the ECU. The MCU calculates the signals and sends corresponding commands to the controller, and the motor outputs the appropriate torque as needed.
The principle of an Analog-to-Digital Converter (ADC): It converts continuous analog signals into discrete digital signals.
Steering-by-Wire Solution
SBW consists of a steering wheel actuator and front wheel actuators. The biggest difference between SBW and EPS is the absence of a central shaft. The Handwheel Actuator (HWA) and Road Wheel Actuator (RWA) are mechanically completely decoupled, allowing for more flexible and adjustable steering ratios and road feedback.
HWA: Includes the steering wheel, steering column, reducer, TAS sensor, and redundant electronic control unit; Function: Acquires the driver's intention, sends the desired steering wheel angle signal to the RWA, and simultaneously simulates road feel feedback to the driver based on the rack force fed back from the RWA.
RWA: Includes a mechanical steering mechanism, angle sensor, and redundant electronic control unit.
