Sensorless Motor Control via Angle-Axis Position Estimation
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Solution Overview
Problem
Conventional sensorless driving methods for three-phase brushless DC motors estimate rotor position based on a time axis, leading to inefficiencies and errors during speed variations, resulting in reduced torque, motor efficiency, and potential step-out issues due to phase advance and delay.
Innovation Solution
The method estimates rotor position based on an angle axis by time-integrating angular speeds, allowing for optimal excitation switching regardless of speed changes, reducing torque ripples and improving motor efficiency by correcting phase errors and eliminating the need for time-axis estimation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If rotor position is estimated based on a time axis using conventional sensorless driving methods, then the control system is simple and cost-effective, but excitation switching phase advance or delay occurs during speed variations, reducing torque and motor efficiency
Solution Approach 1:
The patent changes the fundamental parameter for position estimation from time-based to angle-based. By integrating angular speed to obtain rotor angle and using this angle to determine excitation switching timing, the system eliminates phase advance/delay errors during speed variations while maintaining sensorless operation and simple control architecture.
2Ease of operation
If rotor position is estimated based on a time axis, then the control implementation is straightforward, but phase errors occur during speed variations leading to reduced torque
Solution Approach 1:
The patent transitions from time-axis to angle-axis based control by integrating angular speed to obtain rotor angle. This angle-based parameter is then used to determine excitation switching timing, eliminating phase errors that reduce torque during speed variations while keeping the control implementation straightforward.
3Device complexity
If conventional time-axis estimation is used, then no additional sensors are required, but step-out issues occur during rapid speed changes
Solution Approach 1:
The patent changes the estimation basis from time to angle by integrating angular speed to obtain accurate rotor angle information. This angle-based estimation method accurately tracks rotor position during rapid speed changes, preventing step-out issues while maintaining sensorless operation without additional sensors.
4Device complexity
If excitation switching is controlled by timer delay from zero-cross point, then the control circuit is simple, but the excitation switching position is inaccurate during speed variations
Solution Approach 1:
The patent changes the control parameter from time-delay based to angle-based by using integrated rotor angle to determine excitation switching position. This approach accurately identifies the 30° electrical angle offset from the zero-cross point regardless of speed variations, improving switching position accuracy while keeping the control circuit simple.
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 enhances motor efficiency, reduces torque ripples, and prevents step-out by ensuring optimal excitation switching, even during speed variations, while minimizing the impact of sensor errors and magnetization errors, and can be applied to small-sized motors without the need for hall sensors.
Implementation Method 1
detecting a rotor angle by time-integrating an induced voltage
Implementation Method 2
time-integrating angular speeds
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The present invention addresses the problem of proposing a method for driving a sensorless motor, wherein the method is different from a conventional rotor position estimation method according to a time axis and performs rotor position estimation according to an angle axis, thus making it possible for excitation switching to always be achieved at an optimal angle in response to a change in speed. According to the present invention, an MCU (5) starts excitation of a coil at an excitation section starting point, measures an induced voltage component generated in the coil by a certain period of energization, integrates the voltage component, and sets an excitation section ending position when the integral value reaches zero. In addition, the motor is continuously rotated by repeating the same integration operation by switching to an excitation pattern in the next excitation section.