Abnormality Monitoring Circuit for Electric Power Steering
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Solution Overview
Problem
Existing abnormality monitoring systems in microcomputers, such as those used in electric power steering devices, can erroneously detect Built-In Self-Test (BIST) processing as an abnormality, leading to incorrect resets and repeated self-diagnosis cycles.
Innovation Solution
An abnormality monitoring device with a self-diagnosis circuit and a monitoring unit that disables abnormality monitoring during BIST processing and enables it only after the BIST is completed, preventing erroneous determinations and ensuring proper operation of user programs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If abnormality monitoring is continuously performed on the control unit, then reliability of abnormality detection is improved, but false detection of self-diagnosis processing as abnormality occurs
Solution Approach 1:
The abnormality monitoring circuit is configured to determine whether self-diagnosis processing is finished before initiating abnormality monitoring. This preliminary action prevents the monitoring from starting during BIST processing, thereby avoiding false detection while maintaining continuous monitoring capability for actual abnormalities.
Solution Approach 2:
The abnormality monitoring function is made dynamic by enabling it only after self-diagnosis processing is detected as finished. The monitoring circuit adapts its operation state based on the processing phase, being disabled during BIST and enabled during normal operation, thus resolving the contradiction between continuous monitoring and false detection.
2Manufacturing precision
If self-diagnosis processing is performed in the control unit, then manufacturing precision of the control unit is improved, but productivity is reduced due to inhibition of other processing
Solution Approach 1:
Self-diagnosis processing is performed periodically at predetermined timings rather than continuously. This periodic execution allows the control unit to maintain high quality through regular self-checks while minimizing the impact on productivity by limiting self-diagnosis to specific time windows when it does not conflict with other processing.
Solution Approach 2:
Self-diagnosis processing is executed preliminarily at predetermined timings before normal operation. By performing self-checks in advance at scheduled intervals, the control unit ensures its own quality without continuously inhibiting other processing, thus balancing manufacturing precision and productivity.
Data Source
AI summary
An abnormality monitoring device includes a control unit and a monitoring unit. The control unit includes a self-diagnosis circuit configured to perform a self-diagnosis processing during which other processing is inhibited. The monitoring unit includes an abnormality monitoring circuit and a reset circuit. The abnormality monitoring circuit is configured to perform an abnormality monitoring of the control unit. The reset circuit is configured to reset the control unit when the abnormality monitoring circuit decides an abnormality of the control unit. The abnormality monitoring circuit is configured to determine whether the self-diagnosis processing is finished, disable the abnormality monitoring of the control unit during the self-diagnosis processing, and start the abnormality monitoring of the control unit when the self-diagnosis processing is determined to be finished. Accordingly, the abnormality of the control unit is accurately monitored.