Rotor position detection method of brushless direct current motor without sensor

Abstract

The invention discloses a rotor position detection method of a brushless direct current motor without a sensor. The rotor position detection method of the brushless direct current motor without the sensor comprises a detection method of a rotor start position and a detection method of a rotor position after the motor rotates. According to the detection method of the rotor start position, current relative positions of a coil magnetic field and a permanent magnetic field can be judged according to a law of variation of motor coil magnetic flux along with the permanent magnetic field, specially, symmetric voltage Uvu and Uuv, Uvw and Uwv, and Uuw and Uwu with equal pulse width and the same voltage value are connected with three phase circuits v, u and w of the motor in pairs, the voltage can not enable a rotor of the motor to deflect, the voltage or current of brushless direct current motor coil three phases is sampled, and current relative positions of coil of the rotor and the permanent magnetic field when the motor is started can be estimated according to a voltage circuit equation. According to the rotor position detection method of the brushless direct current motor without the sensor, the position of the rotor can be detected without the requirement for motor rotation, and therefore a current blind starting mode of the brushless direct current motor without a Hall sensor is replaced.

Description

technical field [0001] The invention relates to a method for detecting the rotor position of a DC brushless motor, in particular to a method for detecting the rotor position of a sensorless DC brushless motor. Background technique [0002] Nowadays, with the promotion and popularization of brushless motors, the inherent problems also appear at the same time, which also makes the majority of users feel a little headache. Because the Hall installation is cumbersome, and 80% of the faults of the brushless motor are caused by the Hall element, and even a considerable part of the fault misjudgment of the brushless motor controller is also caused by the Hall element. The performance and life of the Hall element will be affected by electromagnetic interference in the circuit, thus affecting the normal operation of the entire circuit system. Due to its low withstand voltage value, it is very easy to cause breakdown when the motor coil leaks electricity. At the same time, the insta...

AI Technical Summary

Problems solved by technology

Because the installation of Hall is cumbersome, and 80% of the faults of brushless motors are caused by Hall elements, and even a considerable part of the fault misjudgment of brushless motor controllers is also caused by Hall elements.

The performance and life of the Hall element will be affected by electromagnetic interference in the circuit, thus affecting the normal operation of the entire circuit system

Due to its low withstand voltage value, it is very easy to cause breakdown when the motor coil leaks

At the same time, the installation accuracy of the Hall element directly affects the operation performance of the motor of the brushless electric vehicle. If there is a problem, it is necessary to replace the Hall, and generally three of them are required to ensure the consistency of the Hall and make the brushless motor work normally. Even if some motor manufacturers use high-end Hall elements, the Hall elements will eventually become the bottleneck of the motor under the ever-increasing demand for motor power

In recent years, although Hall-free electric vehicle controllers have also appeared on the market, based on the previous scheme, there is no Hall controller. When the motor speed is close to the zero speed area, the exact position of the current rotor cannot be known. Vibration will cause discomfort when riding and starting, and may even fail to start on roads with a certain slope in some areas or under heavy load

In the final analysis, the current Hall-free controllers need to judge the current coil position. There are also some Hall-less controllers on the market, which use the motor to rotate to detect the back EMF. It brings about various problems such as motor jitter, failure to start, poor start, etc.

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