Parallel Processing Paths for EPS Error Verification
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Solution Overview
Problem
Existing electric power steering (EPS) systems face challenges in mitigating software errors that can lead to abnormal assist torque outputs without degrading steering system performance or interfering with assist torque calculations.
Innovation Solution
A control system with parallel primary and secondary processing paths, where the secondary path verifies the output commands from the primary path for errors, generating a fault signal and initiating corrective actions to maintain system reliability without affecting performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If saturation limiters are used in the assist torque calculation paths to mitigate errors, then software systematic errors can be mitigated, but steering system performance and assist torque output calculation are degraded
Solution Approach 1:
The control system is divided into two independent processing paths: a primary path for normal assist torque calculation and a secondary path for error detection and verification. This segmentation allows the system to maintain high performance in the primary path while using the secondary path solely for safety verification, thus resolving the contradiction between reliability and productivity.
Solution Approach 2:
A secondary processing path acts as an intermediary verification mechanism that monitors the primary path's output without interfering with its normal operation. The secondary path generates reference values and compares them with primary path outputs to detect errors, enabling error mitigation while preserving the primary path's performance characteristics.
2Reliability
If redundant memory storage and comparison of safety critical software variables are used, then hardware sources of errors can be mitigated, but device complexity increases
Solution Approach 1:
The system segments error mitigation functions into distinct modules: one module handles redundant memory storage and comparison for hardware error detection, while another module handles the secondary processing path for systematic error detection. This modular segmentation manages complexity by organizing redundant functions into separate, well-defined units.
Solution Approach 2:
The secondary processing path creates a virtual copy of the primary path's computational logic to generate reference assist torque values. This copying approach enables verification without requiring complete hardware redundancy, reducing overall system complexity while maintaining reliability.
Data Source
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AI summary
A method for generating and verifying an output command for using in a power steering system is provided. The method receives, by a module having at least a primary processing path and a secondary processing path that is in parallel with the primary processing path, a set of input signals. In the primary processing path, the method generates a primary output command based on the set of input signals and sends the primary output command out of the module. In the secondary processing path, the method generates a first range of command values based on the set of input signals, determines whether the primary output command falls within the range of command values, and generates a fault signal based on determining that the primary output command does not fall within the first range of command values.