Position sensorless brushless DC motor start control and low speed operation method

Abstract

A starting control and low-speed operation method of a brushless DC motor without a position sensor belongs to the technical field of motor starting. A pulse generation module generates wide / narrow pulses, a position detection module detects current response under the effect of the pulse generation module via a current sensor so as to determine a present rotor position, a torque calculating moduleestimates the approximate rotating speed of a rotor, a rotating speed closed loop is formed, and finally, a Buck converter adjusts the output voltage by adjusting the conduction duty ratio of a powertube. Thus, the brushless DC motor without the position sensor can run at low speed, the speed range of the motor is broadened, high-frequency harmonic waves of the motor when detecting line voltagesignals and the like are reduced, the torque pulses of the motor during starting and low-speed operation are reduced, the average torque is improved, and thus, the brushless DC motor can be started rapidly and accurately.

Description

technical field [0001] The invention belongs to the technical field of motor starting, and in particular relates to a starting control and low-speed operation method of a brushless DC motor without a position sensor. Background technique [0002] Brushless DC motor (Brushless DC Motor, hereinafter referred to as BLDCM) has many outstanding advantages such as simple structure, convenient control and reliable operation, so it is widely used in various fields. The operation of a BLDC motor requires the detection of six discrete rotor positions for winding commutation, usually using three Hall sensors to provide position information. However, rotor position sensors add cost and bulk and reduce reliability. Therefore, sensorless brushless DC motors and their control methods have become a research hotspot in recent years. The position sensorless control technology eliminates the position detection device, so that the system is smaller in size, lower in cost and higher in reliabi...

AI Technical Summary

Problems solved by technology

However, when the brushless DC motor is controlled without a position sensor, the starting process is still a technical difficulty

When the motor is at rest or running at low speed, the counter electromotive force is too small to detect, and all position sensorless control technologies based on counter electromotive force and its harmonics cannot be applied at this stage

At present, the most commonly used three-stage starting method is an open-loop starting method. The rotor position cannot be determined during the speed-up process, which will cause excessive starting current and affect the operation of the motor. The average torque is too large, resulting in speed fluctuations.

When the bus voltage and motor load change, the winding commutation cannot be accurately controlled, and the reliable starting of the motor cannot be guaranteed

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