Shift-By-Wire Motor Position Learning via Minimum Current
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Solution Overview
Problem
The electric shift-by-wire system faces issues with shift stage deviation due to position errors caused by magnetism and motor-driven torques, requiring continuous learning of the motor's reference position to accurately position the detent spring at the root fillet of the detent plate, which is costly with high-precision position sensors.
Innovation Solution
A motor position learning method and apparatus that uses a relatively inexpensive Hall sensor to determine the exact gear shift position by driving the motor in opposite directions and measuring the driving current, calculating the rotation amount where the current is minimum, and setting a new reference position based on this data, allowing for efficient learning without changing the shift stage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high-precision position sensor is used to check the absolute position of the motor, then the measurement precision is improved, but the device cost increases
Solution Approach 1:
The patent replaces expensive high-precision position sensors with a combination of inexpensive Hall sensors and software-based position learning algorithms. The system uses multiple low-cost Hall sensors to detect magnetic field changes and calculates motor position through computational methods, achieving accurate position detection without relying on costly dedicated position sensors.
Solution Approach 2:
The patent substitutes mechanical position sensing with a magnetic field-based detection system. Instead of using mechanical encoders or optical sensors, the system employs Hall sensors to detect magnetic field variations caused by the motor's magnetic poles, converting mechanical position information into magnetic field signal processing.
2Reliability
If the motor position is continuously checked and learned using a high-precision position sensor, then the reliability of shift control is improved, but the device complexity increases
Solution Approach 1:
The patent implements a self-learning position calibration system that automatically determines the relationship between Hall sensor signals and motor position without requiring external calibration equipment or complex sensor systems. The controller performs position learning by analyzing magnetic field patterns and calculating reference positions autonomously, reducing system complexity while maintaining reliability.
Solution Approach 2:
The system continuously monitors Hall sensor outputs and uses feedback algorithms to track motor position changes. The controller compares expected magnetic field patterns with actual sensor readings, dynamically adjusting position calculations to compensate for deviations and maintain accurate shift control.
3Ease of manufacture
If an inexpensive Hall sensor is used instead of a high-precision position sensor, then the device cost is reduced, but the measurement precision deteriorates
Solution Approach 1:
The patent divides the position measurement task into multiple segments handled by separate Hall sensors positioned at different locations. Instead of relying on a single high-precision sensor, the system uses multiple lower-precision Hall sensors to detect magnetic field changes from different angles, combining their outputs through computational methods to achieve accurate overall position measurement.
Solution Approach 2:
The patent creates a composite sensing system that combines multiple Hall sensors with different orientations and positions, along with computational algorithms, to achieve measurement precision comparable to or exceeding that of single high-precision sensors. The system integrates magnetic field data from multiple sources to synthesize accurate position information.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate learning of the motor's reference position using a cost-effective sensor, improving the price competitiveness and reliability of shift control, and can be performed within a short time without changing the shift stage, even when the vehicle is not in the parking stage.
Implementation Method 1
using a relatively inexpensive Hall sensor
Data Source
AI summary
Motor position learning method and apparatus for an electric shift-by-wire system are proposed. The method includes setting, as a first reference position, a motor position at a time point when shift is completed; driving the motor in opposite directions on the basis of the first reference position; measuring a rotation amount of the motor and a driving current flowing through the motor while the motor is driven in opposite directions; and calculating a rotation amount of the motor at a point where the driving current of the motor becomes minimum, and setting, as a second reference position, a position resulting after the motor rotates further by the calculated rotation amount from the first reference position.