Steer-by-Wire Angle Sensor Fail-Safe Using Motor Position Feedback
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Solution Overview
Problem
In Steer-by-Wire (SbW) systems, synchronization failures between angle sensors can lead to difficulties in steering vehicle control, and existing solutions like additional angle sensors or repetitive initialization logic are costly and time-consuming.
Innovation Solution
A fail-safe system using multiple angle sensors and motor position sensors, where MCUs compare signals to determine the steering angle, and motor position sensors remain operational regardless of ignition state, allowing for continuous vehicle control without additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate angle sensor is added to detect sensor failures, then the reliability of steering angle detection is improved, but the system cost and development time increase
Solution Approach 1:
The motor position sensor, originally designed for motor control, is made to serve dual purposes: both motor position feedback and steering angle detection. By configuring the sensor to operate in both ignition ON and OFF states, it can detect steering angle information without requiring additional dedicated angle sensors, thus improving reliability while avoiding increased system complexity
Solution Approach 2:
The existing motor position sensor performs self-service by simultaneously fulfilling its original motor control function and providing steering angle detection capability. The sensor's output signals are reused by the control unit to determine steering angle information, eliminating the need for separate detection components
2Ease of manufacture
If steering angle initialization setting logic is implemented to handle sensor failures, then the system can operate without additional sensors, but the initialization process becomes time-consuming and troublesome
Solution Approach 1:
The motor position sensor is pre-configured to maintain operation during ignition OFF states, establishing readiness for fail-safe operation before actual steering angle detection is needed. This preliminary configuration eliminates the need for time-consuming initialization routines that repeatedly move the steering wheel
Solution Approach 2:
The motor position sensor maintains continuous operation across ignition state transitions, providing uninterrupted steering angle information. This continuity eliminates the need for repeated initialization sequences that currently require multiple steering wheel movements to establish baseline angles
3Reliability
If the motor position sensor is separated from the IGN signal and connected to battery power, then the sensor can operate during ignition OFF state for fail-safe detection, but the power supply system becomes more complex
Solution Approach 1:
The power supply system is configured to provide universal power to the motor position sensor from both ignition-related and battery sources, enabling the sensor to function regardless of ignition state. This multi-source power configuration ensures reliable operation without requiring complex additional power management circuitry
Data Source
AI summary
A fail-safe structure for angle sensors in a Steer-by-Wire (SbW) system may include first and second angle sensors configured to sense a steering angle of a steering wheel associated with a steering feedback actuator assembly, a first MCU configured to receive a first angle signal from the first angle sensor, a second MCU configured to receive a second angle signal from the second angle sensor, and a motor position sensor configured to sense a position of a motor associated with the steering feedback actuator assembly. The first MCU may be configured to, if the first angle signal and the second angle signal do not match each other, receive a motor position signal associated with the position of the motor from the motor position sensor to determine the steering angle of the steering wheel.