Steering Column Position Sensing Without Recalibration After Power Loss
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Solution Overview
Problem
Current steering column systems face challenges in reliably detecting the position of the steering wheel, especially in autonomous driving modes, where accurate and continuous position detection is crucial for safety and airbag system activation, and existing solutions require recalibration after voltage loss.
Innovation Solution
A steering column with a position detection device comprising a contactless position sensor unit, which includes a first and second element that move relative to each other, allowing for continuous and accurate determination of the actuating unit's position relative to the supporting unit, using a control unit to process signals and calculate the position, and featuring a redundant system for increased reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a separate transmission is used to determine the adjustment position (as in US 2018/086378 A1), then the position detection is achieved, but the device complexity increases
Solution Approach 1:
The patent combines the position detection function with the existing adjustment drive mechanism by using the rotor's rotation to directly drive the encoder, eliminating the need for a separate transmission system. The encoder is integrated into the adjustment drive's rotor, merging two functions into one compact unit.
Solution Approach 2:
The patent extracts the position detection function from a separate transmission system and integrates it directly into the adjustment drive's rotor. The encoder is positioned to detect rotor rotation directly, removing the intermediary transmission components while maintaining accurate position measurement.
2Ease of operation
If magnetic sensor systems are used with elements that only produce signals within the adjustment path (as in DE 10 2004 044 472 A1), then the adjustment operation is enabled, but the position detection reliability deteriorates near mechanical end stops
Solution Approach 1:
The patent replaces the magnetic sensor system with an encoder that directly detects the rotor's rotational position. This mechanical-to-electrical conversion provides reliable position detection throughout the entire adjustment path, including at the mechanical end stops where magnetic sensors fail.
Solution Approach 2:
The encoder acts as an intermediary between the rotor's mechanical rotation and the electronic control system. It converts the mechanical position into electrical signals that can be accurately processed, providing continuous and reliable position information even when the adjustment drive reaches its mechanical limits.
3Device complexity
If the steering wheel position is detected from rotor rotation without redundancy, then the system is simpler, but the functional safety (ASIL) requirement is not met
Solution Approach 1:
The patent implements redundancy specifically at the critical position detection point by using multiple encoders (e.g., two independent encoders) to detect the rotor's rotational position. This localized redundancy ensures that if one encoder fails, the other can still provide accurate position information, meeting the ASIL functional safety requirement.
Solution Approach 2:
The patent prepares for potential encoder failure by implementing redundant encoding systems before any fault occurs. The redundant encoders are pre-installed and continuously monitor the steering column position, providing a backup that activates automatically if the primary encoder fails, ensuring uninterrupted safe operation.
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
The solution provides reliable and cost-effective position detection along the entire adjustment path, enhancing safety by enabling precise control of airbag systems and energy absorption devices, and maintaining accuracy without the need for recalibration after power loss.
Implementation Method 1
a contactless position sensor unit, which includes a first and second element that move relative to each other, allowing for continuous and accurate determination of the actuating unit's position
Data Source
AI summary
A steering column for a motor vehicle includes comprising a supporting unit which can be connected to the chassis of the motor vehicle and an actuating unit, which is mounted on the supporting unit and which supports a steering shaft for rotation. The position of the actuating unit can be adjusted in relation to the supporting unit and the steering column has a position detection device for determining the position of the actuating unit relative to the supporting unit.