Steering Rotation Sensor Gear Pair for ASIL-D Plausibility
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Solution Overview
Problem
Existing rotation angle sensors in motor vehicle steering systems, particularly those used in steer-by-wire systems and autonomous driving, do not meet the stringent ASIL-D safety integrity level requirements for plausibility checks, necessitating a method that ensures reliable determination of absolute rotation angles with improved reliability and compliance.
Innovation Solution
A rotation angle sensor unit with an intermeshing gearwheel pair and two independent controller units, each synchronized at initialization to determine and plausibly combine absolute rotation angles from two sets of rotation angle sensors, ensuring ASIL-D compliance even if one controller unit fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single controller unit determines absolute rotation angle using a gearwheel pair, then device complexity is reduced, but reliability does not meet ASIL-D safety integrity level requirements
Solution Approach 1:
The control device is segmented into a first controller unit and a second controller unit, each independently determining absolute rotation angles using the same gearwheel pair and rotation angle sensors. This segmentation provides functional redundancy required for ASIL-D compliance while maintaining relatively simple individual controller structures.
Solution Approach 2:
The system implements beforehand cushioning through redundant controller units that can take over if one fails. The plausibility check mechanism预先 prepares for potential failures by continuously verifying rotation angle data from both controller units, ensuring ASIL-D safety integrity level compliance without requiring complex error correction circuits.
2Reliability
If redundant sensor systems are implemented to achieve ASIL-D compliance, then reliability is improved, but device complexity and cost increase
Solution Approach 1:
The rotation angle sensors serve multiple functions: they provide primary rotation angle data for normal operation and simultaneously enable plausibility checks for safety-critical ASIL-D compliance. The same physical sensors are used by both controller units, avoiding the need for separate redundant sensor sets while achieving the required reliability.
Solution Approach 2:
Instead of physically duplicating sensors, the system creates a functional copy through the second controller unit that independently processes data from the same rotation angle sensors. This virtual copying approach achieves redundancy without the physical complexity and cost of duplicate hardware.
3Reliability
If initialization synchronization is implemented between controller units, then reliability for ASIL-D compliance is achieved, but initialization time and complexity increase
Solution Approach 1:
The system performs preliminary action by synchronizing both controller units to a common initial absolute rotation angle value during initialization. This preliminary synchronization establishes a reliable baseline for subsequent independent operation and plausibility checks, enabling ASIL-D compliance without requiring continuous complex synchronization protocols during operation.
Data Source
AI summary
A method for operating a rotation angle sensor unit for steering systems of motor vehicles, wherein the rotation angle sensor unit has an intermeshing gearwheel pair, wherein a first gearwheel is provided to be connected to the steering component for conjoint rotation and a second gearwheel is mounted in a rotationally fixed manner with respect to the first gearwheel, wherein two first and two second rotation angle sensors are assigned to the first and second gearwheels respectively, and the rotation angle sensor unit comprises a control unit with two independent control units, wherein, for operation of the rotation angle sensor unit with the predetermined vehicle safety integrity level, at the time of initialization of the rotation angle sensor unit each controller unit determines an initial absolute rotation angle for the steering component, and the initial absolute rotation angles are initially synchronized once, wherein each controller unit after initial synchronization continuously determines a first and second absolute rotation angle of the steering component from rotation angle data of a first rotation angle sensor on the one hand and from rotation angle data of a second rotation angle sensor on the other hand and combines these in a plausibilized manner to form an absolute rotation angle.