Sensorless Brushless Motor Drive Initial Position Detection
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Solution Overview
Problem
Existing methods for driving three-phase brushless motors using sensorless control require positioning processing to determine the initial magnetic pole position, which can be time-consuming, especially when motor inertia is high, leading to delays in starting the motor.
Innovation Solution
The solution involves energizing one phase and the other two phases of the brushless motor to create positive and negative currents, allowing the detection of the initial position based on the difference in induced voltage when the current changes polarity, enabling the motor to start without extensive positioning processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If positioning processing is performed to determine initial magnetic pole position before motor start, then motor control accuracy is improved, but start-up time is significantly delayed especially when motor inertia is large
Solution Approach 1:
The patent replaces the mechanical positioning system (which physically rotates and stops the motor at a predetermined position) with an electrical detection system. The control device detects the initial magnetic pole position by measuring induced voltage in the motor windings without any mechanical movement, thereby eliminating the time-consuming positioning processing while maintaining accurate initial position detection.
Solution Approach 2:
The patent performs preliminary detection of the initial magnetic pole position using induced voltage measurement before the motor starts rotating. By obtaining the initial position information in advance through electrical measurement rather than mechanical positioning, the system prepares the necessary control parameters beforehand, enabling immediate motor start-up without waiting for mechanical positioning to complete.
2Measurement precision
If mechanical positioning is used to fix magnetic pole position to predetermined position, then initial position accuracy is improved, but response speed to motor driving request deteriorates
Solution Approach 1:
The patent substitutes the mechanical positioning mechanism with an electrical detection method. Instead of physically moving the motor to a predetermined position, the control device electrically detects the initial magnetic pole position by measuring induced voltage in the windings. This electrical approach provides both high position accuracy and fast response to driving requests.
Solution Approach 2:
The motor itself provides the information needed for position detection through its own induced voltage during the startup process. The control device utilizes the induced voltage naturally generated in the motor windings when current flows through them, eliminating the need for external positioning mechanisms or additional sensors.
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 rapid estimation of the motor's initial position, enabling immediate start-up without the need for lengthy positioning procedures, thus reducing delays and improving responsiveness.
Implementation Method 1
a difference between induced voltage of a non-energized phase when a current in the one phase becomes positive, and induced voltage of the non-energized phase when the current in the one phase becomes negative
Data Source
AI summary
The present invention allows a driving device, which drives a three-phase brushless motor in a sensorless manner, to detect an initial position of the brushless motor and start drive of the motor without performing positioning processing. In a device for driving a brushless motor by sequentially switching six energizing modes, in which two phases to be energized are selected out of three phases, energization is performed sequentially in six energizing modes before start of drive so that the motor does not rotate, and each induced voltage of an opened phase is acquired, induced voltage difference is obtained in each predetermined combination of energizing modes, and it is estimated to which one of six divided regions an initial position of the brushless motor corresponds based on a maximum value of induced voltage differences obtained.