Magnetic Sensor Electrical Correction for Rotational Angle Measurement
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Solution Overview
Problem
Conventional rotational angle-measurement apparatus using magneto-resistance elements face challenges such as difficult mechanical alignment, requirement of an actuator/encoder for electrical correction, accuracy deterioration due to nearby magnetic substances, complex assembly with waterproof structures, and slow response times for high-speed operations.
Innovation Solution
A rotational angle-measurement apparatus that allows electrical correction without an encoder, featuring a magnetic sensor with a chassis made of low magnetic susceptibility material, where the electric motor, rotation shaft, and magnet are covered, and the sensor is disposed outside the chassis, enabling correction by rotating the shaft multiple times at a known speed, and using bridges that output signals proportional to cosine and sine of the rotational angle for quick angle calculation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If magnetic sensor is mounted inside chassis for protection, then reliability improves, but mechanical alignment difficulty increases
Solution Approach 1:
The patent replaces mechanical alignment procedures with electrical correction. Instead of precisely positioning the magnetic sensor during assembly, the system performs post-assembly electrical correction by rotating the shaft and measuring actual magnetic field orientations, then storing correction values in memory to compensate for misalignment.
Solution Approach 2:
The patent performs preliminary electrical correction during the assembly process. By rotating the shaft through multiple revolutions and measuring magnetic field characteristics before final installation, the system pre-determines correction values that will be applied during operation, eliminating the need for precise mechanical alignment.
2Measurement precision
If actuator/encoder is added for electrical correction, then measurement precision improves, but device complexity increases
Solution Approach 1:
The magnetic sensor performs self-correction by utilizing its own output signals during a correction routine. The sensor rotates with the shaft, measures magnetic field orientations at known positions, and automatically determines correction values without requiring external encoders or actuators, thereby achieving high precision while maintaining simple device structure.
Solution Approach 2:
The magnetic sensor serves dual functions: it acts as both the measurement device and the correction device. The same sensor that measures rotational angle during operation is also used to determine correction values during the correction routine, eliminating the need for separate correction mechanisms.
3Adaptability or versatility
If correction is performed after system incorporation, then adaptability improves, but productivity decreases
Solution Approach 1:
The correction process utilizes periodic rotation of the shaft to gather measurement data. By rotating the shaft through a known number of revolutions at a controlled speed, the system periodically samples magnetic field signals at regular intervals, enabling efficient determination of correction values without requiring extended correction time.
4Ease of repair
If magnetic sensor is placed outside chassis for easy replacement, then ease of repair improves, but measurement precision deteriorates due to magnetic substances
Solution Approach 1:
The patent extracts the magnetic sensor from the chassis interior and positions it on the outer surface, separating the sensor from potential magnetic interference sources while maintaining measurement capability through electrical correction.
Solution Approach 2:
The patent introduces electrical correction as an intermediary mechanism that compensates for the reduced measurement precision caused by placing the sensor outside the chassis. The correction values, determined during a calibration routine, mediate between the sensor's external position and the required measurement accuracy.
5Reliability
If waterproof structure is implemented with sensor inside, then reliability improves, but device complexity increases
Solution Approach 1:
The patent extracts the magnetic sensor from the waterproof-enclosed chassis interior and positions it on the outer surface, eliminating the need for complex waterproof penetration structures while maintaining reliability through protective coating on the sensor itself.
6Productivity
If correction routine rotates shaft at high speed, then productivity improves, but measurement precision deteriorates
Solution Approach 1:
The correction routine utilizes periodic rotation at controlled speed to gather sufficient measurement data points. By rotating the shaft through a known number of revolutions and sampling signals at regular intervals, the system achieves both efficient correction speed and adequate measurement precision.
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
Enables accurate and responsive rotational angle measurement even in the presence of high permeability materials, allows for easy sensor replacement, and provides a fault-detection signal for abnormal conditions, improving the apparatus's reliability and measurement speed.
Implementation Method 1
giant magneto-resistance elements (hereafter referred to as GMR elements)... The element resistance varies depending on the difference Δθ=θf−θp between the magnetization direction θp of the pinned magnetic layer and the magnetization direction θf of the free magnetic layer
Implementation Method 2
a magnet mounted on one end of the rotation shaft
Data Source
AI summary
A rotational angle-measurement apparatus with high accuracy is provided through electric correction of the rotational angle-measurement apparatus by rotating the rotation shaft at a constant speed. The rotational angle-measurement apparatus includes an electric motor having a rotation shaft, a magnet mounted on one end of the rotation shaft, and a magnetic sensor with an output signal that changes in accordance with an orientation of a magnetic field surrounding the magnetic sensor. The magnetic sensor outputs an angle signal representing the rotational angle of the rotation shaft, and the correction procedure utilizes rotation of the electric motor shaft through more than one revolution at a rotational speed with a known rate of change.