Position Sensor Tolerance Adaptation for Brushless DC Motor Control
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Solution Overview
Problem
Existing methods for measuring rotational speed and position using position sensors and rotating targets are prone to inaccuracies due to mechanical defects and sensor imprecisions, leading to reduced precision and responsiveness in motor control, especially in high-speed applications.
Innovation Solution
A method that adapts to tolerances by calculating theoretical passing times of singularities on an ideal target, converting time differences into angular differences, and applying corrective terms to improve measurement accuracy, particularly suitable for brushless DC electric machines with Hall-effect sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional position sensors and rotating targets are used for measuring rotational speed and position, then the system is simple and easy to manufacture, but measurement precision deteriorates due to mechanical defects and sensor imprecisions
Solution Approach 1:
The patent performs preliminary actions by measuring timing data during a learning phase before actual operation. During this learning phase, the system acquires timing information for multiple revolutions and calculates average values to determine corrective terms. These pre-calculated corrections are then stored and applied during normal operation, allowing the system to compensate for manufacturing tolerances without adding complex hardware.
Solution Approach 2:
The patent implements feedback by continuously comparing measured timing data with theoretical timing data and using the differences to generate corrective terms. The measured timing for each singularity is compared with the theoretical timing calculated from average rotation period, and the resulting time differences are converted to angular differences that serve as feedback corrections for subsequent measurements.
2Measurement precision
If corrective terms are calculated using multiple measurements and theoretical values, then measurement precision improves, but calculation complexity and processing time increase
Solution Approach 1:
The patent performs all complex calculations during a learning phase before actual operation. Multiple timing measurements are collected and processed to calculate average rotation periods and corrective terms. Once these corrective terms are determined and stored, the actual operation phase only requires simple lookups and applications of the pre-calculated values, significantly reducing real-time processing requirements.
Solution Approach 2:
The patent segments the operation into two distinct phases: a learning phase where complex measurements and calculations are performed, and an operation phase where simple applications of corrective terms occur. This segmentation allows the system to perform complex analysis offline during learning while maintaining simple, fast operation during actual use.
3Productivity
If the system operates at high rotational speeds, then productivity increases, but measurement precision deteriorates due to reduced responsiveness
Solution Approach 1:
The patent uses feedback corrections derived from timing measurements to compensate for errors that increase at high speeds. By continuously comparing actual timing data with theoretical values and applying corrective angular differences, the system maintains measurement precision even when rotational speeds are high and measurement intervals are short.
Solution Approach 2:
The patent performs preliminary calculation of corrective terms based on average rotation periods measured during learning phase. These pre-calculated corrections are then applied during high-speed operation, allowing the system to maintain accurate measurements without performing complex real-time calculations that would reduce responsiveness.
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
Enhances measurement precision by accounting for manufacturing and mounting tolerances, allowing for more accurate control of electric motors and improved responsiveness in high-speed conditions.
Implementation Method 1
use is made of a target having several magnetic poles and associated with at least one Hall-effect sensor
Data Source
AI summary
A method for adapting to the tolerances of a system including at least one position sensor and a rotary target. When the target rotates, the sensor(s) detects (detect) a predefined singularity on the target at an instant T_i, including: acquisition of a series of n+1 instants T_0 to T_N corresponding to a rotation R of the target; determination of theoretical values Theo_i for each instant T_i while considering that the time corresponds to the time that the target takes to effect the rotation R, taking account of any acceleration during the rotation R and as a function of a position of the predefined singularities on an ideal target produced without tolerance; conversion of the time difference between Theo_i and T_i into an angular difference A_i for a corresponding singularity of the target detected by a sensor; and memory-storage of the angular differences A_i for each singularity of the target.