Steering Angle Sensor Redundancy to Reduce Hysteresis Failure
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Solution Overview
Problem
Steering by Wire systems face issues with complete system failure upon component failure and limited accuracy due to hysteresis, affecting driving experience and safety.
Innovation Solution
A fail operational steering angle sensor with a disk-shaped hub, two disk-shaped outer gears of different materials, a printed circuit board, and a metallic rotor, providing redundant magnetic and inductive signals to ensure continued functionality and improved accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single gear system is used in the steering angle sensor, then the device complexity is reduced, but the reliability decreases because complete system failure occurs upon component failure
Solution Approach 1:
The patent divides the single gear system into two independent outer gears (Gear A and Gear B) that operate simultaneously. Each gear has its own reading system on the printed circuit board, creating segmented measurement paths. This segmentation ensures that if one gear fails, the other continues to provide valid steering angle data, preventing complete system failure while maintaining acceptable device complexity.
Solution Approach 2:
The patent applies local quality by using different materials for Gear A and Gear B, optimizing each gear for specific local conditions. Gear A uses a material with higher magnetic permeability for better magnetic field interaction, while Gear B uses a material with lower thermal expansion for stability in temperature variations. This localized material optimization improves overall reliability without requiring a complete redesign of the entire gear system.
2Temperature
If gaps are maintained between gear teeth for thermal expansion accommodation, then the reliability across temperature ranges is improved, but measurement precision deteriorates due to hysteresis effects
Solution Approach 1:
The patent employs composite material strategies by combining gears made of different materials with complementary properties. Gear A uses a magnetically soft material optimized for magnetic field interaction, while Gear B uses a material with superior thermal stability. The printed circuit board integrates multiple reading systems that can compensate for thermal effects. This composite approach allows the system to accommodate thermal expansion through material selection rather than relying solely on physical gaps, thereby reducing hysteresis and improving measurement precision while maintaining temperature range reliability.
3Measurement precision
If a single reading system is used on the printed circuit board, then the device complexity is reduced, but measurement precision decreases due to limited accuracy in detecting gear position
Solution Approach 1:
The patent merges multiple reading systems onto a single printed circuit board, combining the reading capabilities for both Gear A and Gear B into one integrated board. This merging approach improves measurement precision by providing redundant measurement paths and enabling cross-validation of readings, while avoiding the complexity of completely separate reading systems. The integrated board shares common components such as power supply and signal processing circuits, reducing overall device complexity compared to fully independent reading systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Ensures continued vehicle operation and safety by maintaining sensor functionality despite component failures, reducing hysteresis, and enhancing accuracy through heterogeneous redundancy.
Implementation Method 1
providing redundant magnetic and inductive signals to ensure continued functionality and improved accuracy
Implementation Method 2
providing redundant magnetic and inductive signals to ensure continued functionality and improved accuracy
Implementation Method 3
at least two disk-shaped outer gears, gear A and gear B, mechanically connected to the disk-shaped hub by means of protruding teeth
Data Source
AI summary
A fail operational steering angle sensor for vehicles is provided. The fail operational Steering Angle Sensor comprises one central gear (hub) and two outer gears (Gear 1 and Gear 2) mechanically connected to the hub. The two outer gears have magnetic properties, and they are arranged in the vicinity of a Printed Circuit Board (PCB). The SAS Fail Operational is connected to a Steering Wheel Actuator shaft that, by means of a mechanical connection with the central gear, the two outer gears and a rotor arranged between the central gear and the PCB, provides angular rotation to the above-mentioned moving parts. The variations of the magnetic field and flux originated in the rotation of the mechanical parts will be determined by the PCB.