Motor Position Sensing With Opposed Magnetic Sensor Averaging
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Solution Overview
Problem
Conventional methods for estimating the rotational position of a motor using magnetic sensors face accuracy issues when the rotor shaft is eccentric or the position detection magnet is inclined, leading to fluctuating output signal amplitudes that affect estimation accuracy.
Innovation Solution
A position detection device comprising a first sensor group and a second sensor group of magnetic sensors arranged symmetrically across a motor's rotation shaft, with a signal processing unit that averages signals from both groups to estimate the motor's rotational position, thereby stabilizing amplitude values and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If three magnetic sensors are used to estimate rotational position, then cost and size are reduced, but measurement precision deteriorates when rotor shaft is eccentric or magnet is inclined
Solution Approach 1:
The patent applies asymmetry by arranging sensors in two groups (first sensor group and second sensor group) at different radial positions relative to the rotor shaft. The first sensor group is positioned at a first radial distance while the second sensor group is positioned at a second radial distance, creating an asymmetric sensor configuration that compensates for eccentricity and inclination effects through differential measurement.
Solution Approach 2:
The patent extends the sensor arrangement from a single radial plane to multiple radial dimensions by positioning sensor groups at different radial distances from the rotor shaft. This multi-dimensional arrangement allows the system to detect and compensate for position deviations caused by eccentricity and inclination, improving measurement accuracy across different spatial dimensions.
2Measurement precision
If magnetic sensors are positioned to detect rotor position, then position detection is achieved, but signal amplitude fluctuates due to eccentricity or inclination
Solution Approach 1:
The patent uses the second sensor group as a counterbalancing measurement system. By positioning sensors at different radial distances and processing the differential signals between the two sensor groups, the system compensates for amplitude fluctuations caused by eccentricity and inclination, effectively canceling out the destabilizing effects through opposite-signed measurements.
Solution Approach 2:
The patent changes the radial position parameter of the sensors by arranging them at different radial distances from the rotor shaft. This parameter variation allows the system to capture different aspects of the magnetic field, and through signal processing that considers these positional differences, the system maintains stable amplitude characteristics despite mechanical imperfections.
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 solution enhances the accuracy of rotational position detection by generating constant amplitude average signals, even in cases of eccentricity or inclination, thereby maintaining detection precision.
Implementation Method 1
a first sensor group including N (N is a multiple of 3) first magnetic sensors facing a magnet that rotates in synchronization with a rotation shaft of the motor
Data Source
AI summary
A position detection device includes: a first group including N (a multiple of 3) first magnetic sensors facing a magnet that rotates in synchronization with a rotation shaft of a motor and arranged at intervals along a rotation direction of the magnet, and a second group including N second magnetic sensors arranged opposite respectively to the N first magnetic sensors across the rotation shaft in a radial direction of the magnet; and a signal processing device processing output signals respectively output from the first and second magnetic sensors. The signal processing device executes averaging processing of generating N average signals by averaging an output signal of the first magnetic sensor and an output signal of the second magnetic sensor arranged at the position opposite to the first magnetic sensor across the rotation shaft, and estimation processing of estimating a rotational position of the motor based on the N average signals.