BLDC Rotor Standstill Position Detection Using Pulse-Time Interpolation
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Solution Overview
Problem
Sensor-less BLDC motors face challenges in accurately determining the angular position of the rotor at standstill, leading to reduced performance and reliability due to limited accuracy in estimating the rotor position based on winding inductance, which is typically within a 60-degree range.
Innovation Solution
A method involving the application of current pulses to multiple windings while the rotor is at standstill, measuring the time it takes for the current to reach a threshold, and using an interpolation function to improve the accuracy of the rotor position detection by determining an angular adjustment value, thereby enhancing the resolution from approximately 60 degrees to 10 degrees or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensor-less BLDC motors use winding inductance detection to determine rotor position at standstill, then the method is simple and does not require additional sensors, but the measurement precision is limited to within a 60-degree range
Solution Approach 1:
The patent segments the rotor position detection into multiple discrete measurement points around the rotor circumference. By taking measurements at different angular positions and using interpolation between these points, the system achieves higher precision (within 10 degrees or less) while maintaining the simplicity of sensor-less operation. The segmentation of the measurement space allows transformation of coarse 60-degree measurements into fine-grained position data.
Solution Approach 2:
The patent transitions from one-dimensional direct position measurement to a multi-dimensional approach by measuring inductance at multiple angular positions and using interpolation algorithms. This dimensional expansion in the measurement space (adding angular position as a variable) enables the system to achieve sub-10-degree precision from what would otherwise be coarse 60-degree measurements.
2Ease of manufacture
If current pulses are applied to determine rotor position using basic inductance measurement, then the implementation is straightforward, but the position determination accuracy remains limited
Solution Approach 1:
The patent applies preliminary actions by taking multiple inductance measurements at different predetermined angular positions before performing the final position calculation. This preliminary data collection at multiple points enables the interpolation algorithm to achieve high precision (within 10 degrees) while maintaining straightforward implementation using standard current pulse excitation and inductance measurement techniques.
Solution Approach 2:
The patent replaces direct mechanical or sensor-based position detection with an electrical measurement system that uses inductance variations. By substituting physical sensors with electrical inductance measurements and computational interpolation, the system achieves high precision angular position determination (within 10 degrees) while maintaining ease of implementation through standard motor control electronics.
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 significantly improves the accuracy of rotor position determination, enhancing the performance and reliability of the BLDC motor start-up process by providing a more precise angular position, which can be within 10 degrees or even less.
Implementation Method 1
providing a plurality of current pulses to a plurality of windings of the BLDC motor while the rotor of the BLDC motor is at a standstill position
Implementation Method 2
measuring a plurality of times that it takes for the plurality of current pulses to reach a threshold for respective ones of the plurality of windings
Data Source
AI summary
A method for determining a position of a rotor of a brushless direct current (BLDC) motor at standstill. The method includes providing a plurality of current pulses to a plurality of windings of the BLDC motor while the rotor of the BLDC motor is at a standstill position. The method further includes measuring a plurality of times that it takes for the plurality of current pulses to reach a threshold for respective ones of the plurality of windings. A first position corresponding to a shortest time of the plurality of times is determined. A position detection value is determined based on the shortest time and based on times corresponding to positions that are adjacent to the first position. A position of the rotor at the standstill position is determined based on the position detection value and an interpolation function.