Multipole Encoder Angular Position Detection with Irregular Pole Correction
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Solution Overview
Problem
Existing angular position measurement devices using multipole annular encoders face inaccuracies due to irregular pole distribution and power consumption issues when detecting angular position changes during motor stoppages, particularly due to internal stress relaxation and micro-movements.
Innovation Solution
A method and device that utilize a multipole annular encoder with N pairs of poles, where the sensor detects transitions and calculates characteristic times and angles to determine absolute angular position, employing an estimated complete rotation time and characteristic angles to correct counter values and account for irregular pole distribution, thereby reducing measurement errors and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the measuring device is powered down when the rotating member is stopped to limit power consumption, then power consumption is reduced, but the device becomes blind and unable to detect angular position variations during stoppages
Solution Approach 1:
The sensor operates periodically rather than continuously - it is activated at specific moments (when transitions are detected or at scheduled intervals) and powered down at other times. This periodic operation reduces overall power consumption while ensuring the device is awake and capable of detection during critical moments when angular position changes occur, even during motor stoppages.
2Ease of manufacture
If the pole distribution in the encoder is irregular (non-equidistributed), then the encoder can be manufactured more easily, but measurement precision deteriorates due to inaccuracies in determining absolute angular position
Solution Approach 1:
The system uses feedback by detecting actual transition times between poles and comparing them with expected transition times based on the known (but irregular) pole distribution. The difference between actual and expected transition times provides correction information that compensates for the irregular pole spacing, allowing accurate determination of angular position despite the non-equidistributed pole arrangement.
Solution Approach 2:
The invention changes the approach from assuming uniform pole distribution to explicitly accounting for irregular pole distribution. By measuring actual transition times and using these measurements to calculate angular position with correction factors, the system adapts to the actual (irregular) pole parameters rather than relying on idealized uniform spacing, thereby maintaining measurement precision despite manufacturing realities.
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 detection and correction of absolute angular position and travel, even during motor stoppages, with reduced power consumption and computational complexity, by identifying indexing transitions and adjusting counter values based on characteristic angles and times.
Implementation Method 1
a multipole annular encoder comprising N pairs of poles that is fastened to a member that rotates with respect to a reference member and a sensor fastened to the reference member, each pair of poles comprising a pole of north type and a pole of south type
Data Source
AI summary
A multi-pole annular encoder having 2N poles distributed irregularly is positioned facing a sensor that detects transitions between the poles. Times corresponding to the detected transitions are stored and the times that have elapsed between each transition and the previous transition of order 2N, which constitute durations for a complete revolution of a rotating member, are calculated. When the durations thus calculated are stable, a time that has elapsed between a tested transition and the previous transition is calculated, and a characteristic angle of the tested transition is deduced therefrom, this being proportional to a ratio between a time that has elapsed since the previous transition and a stabilized duration for a complete revolution. An index transition is identified and is used to ascertain absolute position of the encoder with respect to the sensor.