Steer-by-Wire Absolute Angle Detection Using Vernier Sensors
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Solution Overview
Problem
Existing steer-by-wire steering systems face challenges in reliably and precisely determining the absolute steering angle, particularly at system startup, without requiring mechanical reference movements, and meeting the stringent ASIL-D safety requirements, which necessitate redundant sensor configurations that increase system complexity.
Innovation Solution
A steer-by-wire steering system utilizing a steering wheel angle detection device with directly connected gears and redundant rotation angle sensors, coupled with a feedback actuator and wheel actuator control units, calculates the absolute steering angle using the Vernier principle, eliminating the need for additional sensors on the steering wheel detection device and ensuring redundant communication and power supply for enhanced reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If redundant sensor configurations are implemented to meet ASIL-D safety requirements, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent combines the absolute angle detection function with the existing relative angle sensor system. By integrating an absolute angle sensor that provides both absolute and relative angle information, the system achieves ASIL-D redundancy requirements without adding completely separate sensor systems. The control unit processes signals from both sensor types, merging their functions to meet safety requirements while managing complexity.
Solution Approach 2:
The absolute angle sensor is designed to provide multiple functions: it delivers both absolute steering angle information for safety-critical backup and relative steering angle information for normal operation. This multi-functionality allows a single sensor component to serve dual purposes, reducing the need for entirely separate sensor systems and thereby managing device complexity while maintaining high reliability.
2Measurement precision
If multiple angle sensors are used to determine absolute steering angle, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The system merges the functionality of absolute and relative angle measurement into an integrated sensor arrangement. The absolute angle sensor provides precision measurement capabilities while the control unit processes signals from both the absolute angle sensor and the relative angle sensor, combining their measurement functions to achieve high precision without requiring completely separate sensor systems.
Solution Approach 2:
The control unit acts as an intermediary that processes and coordinates signals from multiple sensor types. It receives absolute angle signals from the absolute angle sensor and relative angle signals from the relative angle sensor, then integrates these signals to determine the steering angle with high precision, managing the complexity of multiple sensors through centralized signal processing.
3Productivity
If absolute steering angle is determined at system startup without steering movements, then productivity is improved, but measurement precision may be compromised
Solution Approach 1:
The absolute angle sensor is pre-configured to provide absolute steering angle information immediately at system startup without requiring steering movements. This preliminary capability allows the system to initialize with accurate absolute angle data from the absolute angle sensor, while the relative angle sensor continues to provide complementary measurement data, ensuring both productivity and precision are maintained.
Solution Approach 2:
The control unit continuously monitors and compares signals from both the absolute angle sensor and the relative angle sensor. This feedback mechanism allows the system to verify the accuracy of absolute angle measurements taken at startup by comparing them with subsequent relative angle changes, thereby maintaining measurement precision while enabling immediate operation at system startup.
Data Source
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Figure 3
AI summary
The invention relates to a steer-by-wire steering system for a motor vehicle, wherein the steer-by-wire steering system comprises a steering wheel angle detection device (10), a feedback actuator (7), and a wheel actuator (9). The wheel actuator (9) includes a wheel actuator control unit (91) which is communicatively connected to a feedback actuator control unit (71) and is configured to calculate an absolute steering angle based on sensor values from at least two first rotation angle sensors (3a, 3b) on a second gear (2) of the steering wheel angle detection device (10) and sensor values from at least two second rotation angle sensors (6a, 6b) on a motor shaft (5) of the feedback actuator (7). The invention further relates to a motor vehicle and a method for determining an absolute steering angle.