Steering Angle Sensor Redundancy With Dual Gear Sensing
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Solution Overview
Problem
Current steering angle sensors in Steer by Wire systems face issues of complete failure upon component failure and limited accuracy, leading to potential safety risks and poor driving experience.
Innovation Solution
A fail operational steering angle sensor with a redundant mechanical and signal configuration, utilizing two outer gears of different materials and an additional rotor, combined with inductive and magnetic sensing, to ensure continuous operation and enhanced accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single gear configuration is used in the steering angle sensor, then the device complexity is reduced, but the reliability decreases because the entire sensor fails when one component fails
Solution Approach 1:
The sensor is divided into two independent gear systems (first and second outer gears) that can operate independently. Each gear has its own reading mechanism, allowing the sensor to function even if one gear or its reading mechanism fails. This segmentation creates redundancy without requiring a completely duplicated system.
Solution Approach 2:
Different materials are used for the first and second outer gears based on their specific functional requirements. The first outer gear may use a material optimized for magnetic reading, while the second outer gear uses a material optimized for inductive reading. This allows each component to have locally optimized properties for its specific reading mechanism.
2Temperature
If gears with larger gaps between teeth are used to accommodate thermal expansion, then the reliability across temperature ranges is improved, but the measurement precision decreases due to increased hysteresis
Solution Approach 1:
The patent replaces direct mechanical reading of gear positions with magnetic and inductive sensing systems. Magnetic sensors detect the position of magnetized features on the gears, while inductive sensors detect changes in electrical impedance caused by gear tooth proximity. This substitution eliminates the need for tight mechanical tolerances and reduces hysteresis effects.
Solution Approach 2:
Different materials are selected for the first and second outer gears to optimize their thermal and magnetic properties. The first outer gear may use a material with low thermal expansion and good magnetic properties, while the second outer gear uses a material with different characteristics suitable for inductive sensing. This composite approach allows each gear to be optimized for its specific sensing mechanism and thermal environment.
3Ease of operation
If higher steering ratio is used in Comfort Mode, then the ease of operation is improved, but the measurement precision requirement increases to maintain wheel position accuracy
Solution Approach 1:
The system dynamically switches between different gear configurations or reading mechanisms based on the steering mode. In Comfort Mode with higher steering ratio, one gear system is prioritized for ease of operation, while in Sport Mode with lower steering ratio, the other gear system provides higher precision measurement. This dynamic adaptation allows the system to optimize for either ease of operation or measurement precision depending on the driving conditions.
Solution Approach 2:
The dual gear system is designed to serve multiple functions: the first outer gear and its reading mechanism handle one steering mode optimization, while the second outer gear and its reading mechanism handle the other steering mode optimization. Both systems work together to provide both ease of operation and measurement precision across different driving conditions, making the sensor universally applicable to various steering modes.
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 continuous vehicle operation and safety by maintaining sensor functionality even with component failures, and significantly reduces hysteresis and improves accuracy, allowing safe parking or driving to a workshop.
Implementation Method 1
a set of inductive coils (111) evenly distributed over its surface in a circular arrangement and correctly aligned with the set of openings of the disk-shaped rotor
Implementation Method 2
an integrated circuit (IC) incorporating sensing elements which are installed in a printed circuit board (PCB)
Data Source
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AI summary
The present application describes a fail operational steering angle sensor for vehicles. The fail operational Steering Angle Sensor comprises one central gear (hub) and two outer gears (Gear 1 and Gear 2) mechanically connected to said 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.