Three-Phase DC Brushless Motor Control Using Temporal Pole Estimation
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Solution Overview
Problem
Existing control methods for three-phase DC brushless motors with one position sensor struggle to accurately switch magnetic fields at suitable timings due to magnetization variations, leading to rotation irregularities.
Innovation Solution
A control method that detects the first magnetic pole using a sensor, estimates the time until the second position is reached, and adjusts the magnetic field generation parts to ensure suitable magnetic field switching when the first magnetic pole passes through the second position, thereby controlling rotation irregularity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If magnetic poles are assumed to be arranged at equal intervals for position estimation, then device complexity is reduced by using one position sensor, but measurement precision deteriorates due to magnetization variations
Solution Approach 1:
The invention changes the estimation parameter from spatial interval (assuming equal angular intervals between magnetic poles) to temporal interval (measuring actual time between pole detections). By detecting the actual time period between consecutive magnetic poles passing the sensor and using this measured time parameter to estimate positions of other poles, the system maintains accurate position estimation even when magnetic pole intervals vary due to magnetization differences, thus resolving the contradiction between using one sensor and maintaining precision.
2Ease of operation
If position estimation is performed based on equal interval assumption, then ease of operation is improved, but reliability deteriorates due to rotation irregularity
Solution Approach 1:
The invention introduces feedback by continuously measuring the actual time period between magnetic pole detections and using this feedback information to adjust the timing of magnetic field switching. The control device measures the real-time period T between consecutive poles, then uses this measured value to accurately determine when to switch magnetic fields for other poles, creating a closed-loop control system that adapts to actual rotor conditions, thereby improving rotation reliability while maintaining operational simplicity.
3Productivity
If magnetic field switching is performed at fixed timing intervals, then productivity is improved, but manufacturing precision deteriorates due to inaccurate pole position detection
Solution Approach 1:
The invention makes the magnetic field switching timing dynamic rather than fixed. Instead of switching fields at predetermined fixed intervals, the system dynamically adjusts switching timing based on the actually measured time period T between magnetic pole detections. This dynamic adaptation allows the motor to maintain high productivity through rapid response while achieving precise magnetic field switching accuracy that matches the actual physical conditions of each specific motor instance, resolving the contradiction between speed and precision.
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 allows for precise switching of magnetic fields at optimal times, effectively mitigating rotation irregularities and improving control accuracy compared to previous methods.
Implementation Method 1
a sensor to detect a magnetic pole of the rotor which pole passes through a first position in the stator
Implementation Method 2
a stator that includes a plurality of magnetic field generation parts to generate a magnetic field to be a driving source of the rotor
Implementation Method 3
magnetic fields generated by a plurality of coils provided in the stator are serially switched and the rotor is rotated
Data Source
AI summary
A control method for a three-phase DC brushless motor including a rotor that includes a plurality of magnetic poles and that is rotatable, a stator that includes a plurality of magnetic field generation parts to generate a magnetic field to be a driving source of the rotor, and a sensor to detect a magnetic pole of the rotor which pole passes through a first position in the stator is provided, the method including: detecting in which the sensor detects a first magnetic pole of the rotor which pole passes through the first position; estimating, based on a result of the detection of the first magnetic pole, time until the first magnetic pole reaches a second position in the stator; and controlling the plurality of magnetic field generation parts in such a manner that a suitable magnetic field is generated when the first magnetic pole passes through the second position.