Motion Sensor Module Failsafe Self-Test Method
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Solution Overview
Problem
Existing motion sensor module self-test methods are limited by saturation and bandwidth, restricting testing to when the vehicle is stationary and may fail to indicate faults in moving components, especially if the test status port develops a short to the supply voltage.
Innovation Solution
A failsafe self-testing method involving a first and second change of state in the test activation port, with the second change being shorter in duration, allowing continuous verification of the motion sensor module's functionality without affecting the output signal, even when the vehicle is moving, by monitoring the test status port's response time and setting an error flag for consistent failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a self test signal is applied to the motion sensor module, then the sensor module can be tested for proper functioning, but the test signal may saturate the device and limit the usefulness of the sensor during the self test
Solution Approach 1:
The patent segments the self-test signal into two distinct phases: a first change of state with first predetermined duration for complete testing, and a second change of state with second predetermined duration (shorter than the first) for rapid continuous testing. This segmentation allows the system to perform both comprehensive tests and quick status checks without saturating the sensor for extended periods, thereby maintaining sensor availability while ensuring thorough testing.
2Reliability
If the self test frequency is increased to improve fault detection, then fault detection capability improves, but the bandwidth of the motion sensor module limits the testing frequency
Solution Approach 1:
The patent implements dynamic test frequency adjustment by using two different test signal durations. The system dynamically selects between a longer first duration for comprehensive testing when needed and a shorter second duration for rapid continuous testing during vehicle motion. This dynamic approach allows the system to adapt the test frequency to the operational context, improving fault detection capability without being constrained by the sensor's bandwidth limitations during normal operation.
3Measurement precision
If the test status port is monitored continuously to detect faults, then fault detection accuracy improves, but the system complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the microprocessor monitors the test status port voltage level after applying the test signal. The system applies a test signal, waits for a predetermined time, then reads the test status port to determine if the sensor is functioning properly. This feedback loop provides continuous fault detection capability with relatively simple implementation, as it only requires monitoring a single status port voltage level rather than complex continuous analysis of multiple parameters.
Data Source
AI summary
A short duration test activation signal is applied to the test activation port of a motion sensor module and the test activation status port observed with an error flag being set if a corresponding signal does not appear at the test activation status port within a predetermined time period.