Sensorless Single-Phase AC Permanent Magnet Motor Control
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Solution Overview
Problem
Single phase alternating current permanent magnet motors require additional fixing accessories for hall units, which increase cost, volume, and reduce reliability due to occupied space.
Innovation Solution
A sensorless driving method for single phase alternating current permanent magnet motors, comprising a starting drive mode and a stable drive mode, where currents are input and terminated based on detected zero crossing points of back electromotive force to determine and maintain rotor position without external sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hall unit is installed to determine rotor position accurately, then position detection reliability is improved, but device complexity and volume increase due to additional fixing accessories
Solution Approach 1:
The patent extracts and eliminates the hall unit and its associated fixing accessories from the motor structure. Instead of using external sensors, the invention uses the motor's own winding to detect rotor position through back electromotive force signals, thereby removing the problematic components while maintaining position detection capability
Solution Approach 2:
The motor system performs self-diagnosis and self-positioning by using its own winding to generate and detect back electromotive force signals. The control unit utilizes these signals to determine rotor position and speed without external sensors, making the system self-sufficient and eliminating the need for hall units and fixing accessories
2Reliability
If a hall unit with fixing accessories is used, then position detection is reliable, but motor volume increases due to occupied space
Solution Approach 1:
The hall unit and fixing accessories are completely extracted from the motor structure. The invention replaces these external components with an integrated sensing method that uses the existing winding, thereby eliminating the space occupation while maintaining position detection functionality
Solution Approach 2:
The winding serves multiple functions: it generates electromagnetic torque for motor operation and simultaneously generates back electromotive force signals for position and speed detection. This multi-functionality eliminates the need for separate sensing components and their associated space requirements
3Measurement precision
If a hall unit is installed for accurate position determination, then position detection accuracy is improved, but manufacturing cost increases due to additional components
Solution Approach 1:
The patent removes the hall unit and fixing accessories from the bill of materials. By using the existing winding for both torque generation and position sensing, the invention eliminates additional component costs while maintaining position detection accuracy through back electromotive force signal analysis
Solution Approach 2:
The invention uses software-based signal processing algorithms to extract position information from back electromotive force signals. This approach replaces expensive hardware sensors with computational methods, significantly reducing manufacturing costs while maintaining measurement 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 method reduces the need for additional fixing accessories, enhancing motor reliability and efficiency by accurately determining rotor position and speed, thus minimizing space and cost while maintaining stable operation.
Implementation Method 1
detecting generation of a back electromotive force, detecting a first zero crossing point of the back electromotive force
Data Source
AI summary
A sensorless driving method for a single phase alternating current permanent magnet motor is described. The method comprises a starting drive mode and a stable drive mode. The starting drive mode comprises inputting a first current to drive a rotor to rotate to a stable position, the first current comprising a pulse current flowing in a first direction for a first predetermined starting time interval and a constant current flowing in a second direction contrary to the first direction for a second predetermined time interval, terminating the first current, determining generation of a back electromotive force, detecting a first zero crossing point of the back electromotive force, inputting a second current for a first charge time interval, waiting for a first post-charge time interval, detecting a second zero crossing point to define a previous half period between the first zero crossing point and the second crossing point, inputting the second current for a second charge time interval, waiting for a second post-charge time interval, and detecting speed of the rotor to compare the speed to a predetermined value. The second current flows in a direction in which the back electromotive force is generated.