Rotation Angle Detector Fourth Order Error Cancellation
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Solution Overview
Problem
Existing rotation angle detectors and torque sensors fail to thoroughly remove the fourth order error component from angle information, which affects the accuracy of rotation angle calculations.
Innovation Solution
A rotation angle detector with a multipolar magnet ring and multiple magnetic sensors arranged along its circumference, where each sensor outputs angle information with a phase difference of 360/N degrees, and an arithmetic unit calculates the rotation angle to reduce the fourth order error component by offsetting and averaging the phase differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple magnetic sensors are arranged along the circumferential direction of the multipolar magnet ring to detect rotation angle, then the rotation angle can be calculated based on angle information from each sensor, but the fourth order error component may not be thoroughly removed from the angle information
Solution Approach 1:
The magnetic sensor group is segmented into N magnetic sensors arranged at different circumferential positions around the multipolar magnet ring. Each sensor detects angle information with a specific phase characteristic, and the arithmetic unit processes these segmented measurements to eliminate error components through mathematical operations.
Solution Approach 2:
The phase difference parameter between adjacent magnetic sensors is specifically set to 360/N degrees in electrical angle. This parameter configuration enables the arithmetic unit to process the angle information in a way that cancels out the fourth order error component while preserving the accurate rotation angle signal.
2Reliability
If N magnetic sensors are arranged with phase difference of 360/N degrees to reduce fourth order error component, then the error reduction is achieved, but the device complexity increases
Solution Approach 1:
The magnetic sensor group with N sensors arranged at 360/N degree intervals serves multiple functions: it detects the rotation angle, provides phase-differentiated angle information for error cancellation, and maintains scalability for different error component orders by adjusting N.
Solution Approach 2:
The magnetic sensors are asymmetrically positioned around the magnet ring at specific angular intervals rather than uniformly distributed, creating phase differences that are specifically designed to cancel fourth order error components while maintaining detection accuracy.
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 configuration effectively shifts and cancels out the fourth order error component, enhancing the accuracy of rotation angle detection by averaging the phase differences among the sensors.
Implementation Method 1
a multipolar magnet ring magnetized multipolarly along a circumferential direction
Implementation Method 2
at least one magnetic sensor group including N (N is a natural number of 3 or higher, except 4) magnetic sensors being placed along the circumferential direction of the multipolar magnet ring, and outputting angle information
Data Source
Figure 1
Figure 2A~2F
Figure 3A~3D
AI summary
A rotation angle detector (1) includes: a multipolar magnet ring (2) magnetized multipolarly along a circumferential direction, at least one magnetic sensor group including three magnetic sensors (3) being placed along the circumferential direction of the multipolar magnet ring (2), and outputting angle information in association with the rotation of the multipolar magnet ring (2), the respective pieces of the angle information having a phase difference therebetween of 120 degrees in an electrical angle, and an arithmetic unit (4) configured to calculate a rotation angle of the multipolar magnet ring (2) based on the angle information outputted from the three magnetic sensors (3) included in the magnetic sensor group.