Rotational Angle Sensor Diagnosis at Low Motor Speeds
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing rotational angle detection apparatuses in electric vehicles struggle to accurately detect abnormalities at low rotational speeds, leading to delayed fault detection and reduced precision due to low induced voltage and inaccurate estimation of motor angles.
Innovation Solution
A rotational angle detection apparatus utilizing multiple rotation detection sensors with sine wave output patterns, where the total output values sum to zero, and an abnormality diagnosis unit calculates estimation values and differences to determine sensor abnormalities, including fixing and connection failures, even at low speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the motor rotational speed is low, then the induced voltage is low, but the estimation motor angle cannot be calculated with good accuracy and abnormality detecting precision becomes low
Solution Approach 1:
The patent introduces an intermediary estimation method using counter electromotive voltage as a mediator to calculate the estimation motor angle. This allows abnormality detection to proceed even when direct measurement from Hall sensors is insufficient at low speeds, bridging the gap between speed limitations and detection requirements.
Solution Approach 2:
The patent changes the parameter used for angle estimation from relying solely on Hall sensor output patterns to using counter electromotive voltage characteristics. By changing the estimation parameter to one that remains effective at low speeds, the system maintains abnormality detection precision across the full rotational speed range.
2Reliability
If the motor rotational speed is low, then the induced voltage is low, but the time until abnormality is detected becomes quite long
Solution Approach 1:
The patent performs preliminary calculation of the estimation motor angle using counter electromotive voltage before actual abnormality detection is needed. This preliminary action ensures that detection can proceed immediately when required, eliminating delays that would occur from waiting for Hall sensor output changes at low speeds.
Solution Approach 2:
The patent implements feedback by continuously comparing the estimation motor angle (calculated from counter electromotive voltage) with the actual motor angle (from Hall sensors). This continuous feedback mechanism enables timely abnormality detection regardless of rotational speed, as the comparison occurs at every measurement cycle rather than waiting for signal changes.
3Measurement precision
If the estimation motor angle is calculated based on the counter electromotive voltage, then the abnormality can be detected, but the abnormality cannot be detected only by detection information of the rotational angle detection apparatus
Solution Approach 1:
The patent makes the rotational angle detection apparatus multi-functional by enabling it to perform both normal angle detection (using Hall sensors) and abnormality detection (using counter electromotive voltage estimation). This universality allows the same apparatus to operate independently across different functional modes without requiring separate external systems.
Solution Approach 2:
The patent enables the rotational angle detection apparatus to self-diagnose abnormalities using its own internal resources - the counter electromotive voltage is already present in the motor system, and the apparatus uses this existing signal to calculate the estimation motor angle and perform self-checks, making the system self-sufficient for abnormality detection.
Data Source
AI summary
To provide a rotational angle detection apparatus which can determine abnormality of the rotational angle detection apparatus only by detection information of the rotational angle detection apparatus even when the rotational speed is low. A rotational angle detection apparatus totals sensor output values of N−1 pieces of the rotation detection sensors other than the diagnosis object sensor; calculates a value obtained by inverting positive/negative of a total value, as an estimation value of sensor output value of the diagnosis object sensor; calculates an estimation difference which is a difference between a sensor output value of the diagnosis object sensor, and the estimation value of sensor output value of the diagnosis object sensor; and determines that abnormality occurred in the diagnosis object sensor, when the estimation difference is out of a determination range for estimation difference.