Rotating Field Sensor Angle Detection Error Cancellation
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Solution Overview
Problem
Rotating field sensors using magnetoresistive elements often detect angles with errors due to distortion in output signal waveforms caused by the elements themselves, particularly at varying magnetic field intensities, leading to inaccuracies in determining the angle of a rotating magnetic field relative to a reference direction.
Innovation Solution
A rotating field sensor design incorporating multiple detection units and arithmetic circuits that process signals from magnetoresistive elements to reduce error components, with specific phase differences between detection circuits' outputs, allowing error components to cancel out and improve angle detection accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetoresistive elements are used to detect the rotating magnetic field, then the sensor can measure the angle of rotation, but the output signal waveforms are distorted from sinusoidal curves causing angle detection errors
Solution Approach 1:
The sensor is divided into multiple detection units (first detection unit with first and second detection circuits, second detection unit with third and fourth detection circuits), each detecting different components of the rotating magnetic field. This segmentation allows independent processing of error components from each circuit, enabling more effective error cancellation through the arithmetic circuits that combine these segmented signals.
Solution Approach 2:
The patent introduces specific phase differences (odd multiples of 1/4 period) between the output signals of different detection circuits. By changing the phase parameters of the detection circuits and using arithmetic operations, the error components with 1/3 period are transformed and canceled out, converting the distorted waveforms into more accurate sinusoidal representations for angle calculation.
2Measurement precision
If correction sensing elements are added to reduce waveform distortion, then angle detection accuracy improves, but the device complexity increases
Solution Approach 1:
Each detection circuit serves multiple functions: it detects a specific magnetic field component, generates an output signal with characteristic phase properties, and provides input to arithmetic circuits for error cancellation. The arithmetic circuits themselves perform multiple operations including phase shifting, signal combination, and error component elimination, making the system multi-functional without proportionally increasing physical complexity.
Solution Approach 2:
Instead of adding more physical sensing elements or mechanical correction mechanisms, the patent uses electronic arithmetic circuits to process and combine the signals from the existing magnetoresistive elements. This substitution of mechanical/physical correction methods with electronic signal processing achieves waveform correction and error cancellation while maintaining relatively simple device structure.
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
The proposed solution effectively reduces the angular error in detected angles by canceling out error components in the output signals, enhancing the accuracy of angle detection in rotating field sensors.
Implementation Method 1
Each of the bridge circuits includes four magnetoresistive elements (hereinafter referred to as MR elements) serving as magnetic detection elements
Data Source
AI summary
A first detection unit has first and second detection circuits. A second detection unit has third and fourth detection circuits. Output signals of the second and fourth detection circuits differ from output signals of the first and third detection circuits in phase, respectively, by an odd number of times ¼ the signal period. The output signal of the third detection circuit differs from the output signal of the first detection circuit in phase by an integer multiple of ⅙ the signal period other than an integer multiple of ½ the signal period. A rotating field sensor generates a first signal based on the output signals of the first and third detection circuits, generates a second signal based on the output signals of the second and fourth detection circuits, and calculates a detected angle value based on the first and second signals.