Shift Range Control Device Sensor Abnormality Compensation
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Solution Overview
Problem
Conventional shift range switching devices face challenges in proper motor control due to potential abnormalities in the output shaft sensor, which can lead to inadequate motor operation.
Innovation Solution
A shift range control device that acquires motor rotation angle signals and output shaft signals, learns position correction values, sets motor angle target values, and controls the motor to achieve the target position, while also monitoring the availability of output shaft signals for abnormality detection and notification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the output shaft sensor is used to detect rotation position for motor control, then the shift range switching accuracy is improved, but the system reliability deteriorates when the sensor experiences abnormalities
Solution Approach 1:
The system performs preliminary learning of the relationship between encoder counts and output shaft sensor signals during normal operation. This pre-acquired knowledge is stored and used to maintain control accuracy when the output shaft sensor becomes abnormal, allowing the system to anticipate and compensate for sensor failure conditions.
Solution Approach 2:
The encoder serves as an intermediary measurement device that provides backup rotation position information. When the output shaft sensor fails, the control unit switches to using encoder data combined with learned relationships to maintain control functionality, effectively using the encoder as a mediator to bridge the gap caused by sensor failure.
2Reliability
If the motor control system switches to using encoder data when output shaft sensor is abnormal, then the system reliability is improved, but the control precision deteriorates due to lack of direct output shaft position feedback
Solution Approach 1:
The control unit pre-learns the relationship between encoder counts and actual output shaft positions during normal operation. This learned mapping is stored and applied when switching to encoder-based control, allowing the system to maintain measurement precision by translating encoder data into accurate position information even without direct output shaft sensor feedback.
Solution Approach 2:
The system changes the control parameters from direct output shaft sensor signals to encoder-based calculated positions. By transforming the measurement approach and using pre-acquired relationship data, the system maintains control precision while relying on the more reliable encoder input during abnormal conditions.
3Reliability
If the system continuously monitors output shaft signal availability for abnormality detection, then the system reliability is improved, but the device complexity increases
Solution Approach 1:
The control unit performs self-diagnosis by monitoring the plausibility of output shaft sensor signals against expected patterns derived from encoder data and learned relationships. The system detects abnormalities through self-comparison and consistency checks, eliminating the need for separate complex monitoring hardware while maintaining high reliability.
Solution Approach 2:
The system uses feedback from the relationship between encoder counts and output shaft sensor signals to detect abnormalities. By continuously comparing expected signal patterns with actual readings, the system automatically identifies sensor failures and switches control modes, providing reliable abnormality detection through simple comparative feedback logic.
Data Source
AI summary
A shift range control device switches a shift range by controlling driving of a motor. A learning unit learns, as a position correction value, a normal state time correction value calculated based on first and/or second reference angles when an output shaft signal is available when turning on of a start switch. The first reference angle is a motor angle when the output shaft signal changes in response to the rotation of the motor in a first direction. The second reference angle is the motor angle when the output shaft signal changes in response to the motor rotation in a second direction opposite to the first direction. A motor angle target value is set by using the normal state time correction value stored during a period from when all the output shaft signals are determined to be unavailable to when the start switch is turned off.