Brushless Motor Rotor Position Detection via Coil Removal
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Solution Overview
Problem
Conventional brushless motor control systems face challenges in accurately detecting the rotor stop position due to variations in inductance values of the coils, leading to false detection and difficulty in precise positioning without using Hall elements or position detection magnets.
Innovation Solution
A brushless motor control system that removes one phase coil from each pole, allowing for direct current voltage application between the remaining phases to detect electric current patterns and determine the rotor stop position, eliminating the influence of inductance variations and reducing component count.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If sensorless type drive control is implemented to eliminate Hall elements and position detection magnets, then device complexity and cost are reduced, but rotor stop position detection accuracy deteriorates due to inductance variations in coils
Solution Approach 1:
The invention changes the detection parameter from direct current comparison (which is affected by inductance variations) to alternating current frequency analysis. By applying AC voltage and detecting the resonance frequency of the coil circuit, the system can identify rotor position without being influenced by coil inductance variations, thus maintaining detection accuracy while using sensorless control
Solution Approach 2:
The invention replaces the mechanical/sensor-based position detection method with an electrical field-based detection method. Instead of using Hall elements or position detection magnets that require physical installation, the system uses AC voltage application and current frequency analysis to detect rotor position, eliminating mechanical components while improving reliability
2Device complexity
If conventional rotor stop position detection method is used with equal L values assumption, then detection process is simplified, but detection accuracy deteriorates due to actual inductance variations in motor coils
Solution Approach 1:
The invention changes the detection approach from DC current magnitude comparison to AC frequency domain analysis. By applying AC voltage and analyzing the resonant frequency characteristics of the coil circuit, the system can detect rotor position accurately without being affected by inductance variations, while maintaining a relatively simple detection process
Solution Approach 2:
The invention introduces AC voltage as an intermediary signal to facilitate rotor position detection. By using AC excitation and analyzing the resulting current frequency characteristics, the system creates an intermediate measurement that is insensitive to inductance variations, thereby achieving accurate position detection without directly measuring affected parameters
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
Enables reliable detection of the rotor stop position without Hall elements or position detection magnets, reducing the number of components and size while improving accuracy and reducing weight.
Implementation Method 1
a brushless motor control system that removes one phase coil from each pole, allowing for direct current voltage application between the remaining phases to detect electric current patterns and determine the rotor stop position
Data Source
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AI summary
A brushless motor control system according to the present invention detects a rotor stop position when activating the brushless motor including a stator having coils of three phases U, V, and W, and controls a phase voltage for energizing the coils of the respective phases U, V, and W, and the brushless motor includes the stator having coils of phases U, V, and W ofN (N ≥ 2) poles, in which any one phase coil among the coils of the phases U, V, and W is removed in one of the N poles, and the brushless motor control system includes: a current rise detecting circuit that, when the brushless motor is in a stop state, sequentially selects coils of two phases from the coils of the respective phases U, V, and W, applies a predetermined direct current voltage between the selected coils of the two phases, and detects a value of an electric current flowing to the selected coils of the two phases; and a rotor stop position detecting unit that determines a rotor stop position of the brushless motor based on information of the value of the electric current flowing to the respective phase coils which is detected by the current rise detecting circuit.