Wide-speed-regulation-range brushless direct current motor position sensorless control device and method

Abstract

The invention relates to a wide-speed-regulation-range brushless direct current motor position sensorless control device and a method. The device comprises a direct current power supply, a three-phase inverter, a brushless direct current motor, a three-phase inverter power device driving circuit, a microcontroller and a rotor position detection circuit, wherein the direct current power supply is connected with the brushless direct current motor through the three-phase inverter; a signal which is output after the rotor position detection circuit is connected with the brushless direct current motor to perform detection is directly connected to an analog-digital conversion input pin of the microcontroller; and six paths of output of the microcontroller are connected to the three-phase inverter through the three-phase inverter power device driving circuit. In the method, terminal voltage of a three-phase winding of a motor is obtained through sampling by using an XC878 single-chip embedded analog-digital conversion unit, and real-time computing processing is performed on a sampling value by using a voltage difference conversion-based signal processing method, so that a feedback signal which contains open-phase counter electromotive force information and of which the amplitude is double that of actual counter electromotive force is obtained, and a zero crossing point of the counter electromotive force is obtained as a basis for phase change of a motor winding; and thus, detection accuracy of the zero crossing point of the counter electromotive force during low-speed running is improved, and the aim of wide-speed-regulation-range running is fulfilled.

Description

technical field [0001] The present invention relates to a control device and method for a brushless DC motor without a position sensor, in particular to a control device and method for a brushless DC motor without a position sensor which has the characteristics of low cost and can effectively improve the accuracy of position detection and realize a wide range of speed regulation . Background technique [0002] At present, the conventional method adopted for the position sensorless control of the brushless DC motor is the back EMF zero-crossing detection method. This detection method is mainly used in two-two conduction, three-phase six-state square-wave brushless DC motors. Its working principle is: due to the back EMF of the non-conducting phase of the brushless DC motor, there are two zero-crossing points in one cycle, and each zero-crossing point is 30° electrical angle ahead of the next commutation point. Therefore, as long as each zero-crossing point in the non-conduc...

AI Technical Summary

Problems solved by technology

However, the traditional back-EMF zero-crossing detection method has the following defects: First, the amplitude of the back-emf sampling signal is small at low speeds, and the existing method is difficult to accurately detect the back-emf zero-crossing point, resulting in the control system of the brushless DC motor without a position sensor. The low-speed operation performance is not ideal, and a wide speed range cannot be realized, which limits the application range of the existing position sensorless control technology

Secondly, if image 3 As shown, due to the influence of pulse width modulation during speed regulation operation, the back EMF sampling signal in the existing method contains rich high-frequency interference, resulting in low position detection accuracy and affecting the speed regulation performance

Third, most of the existing methods use the comparison between the terminal voltage and the reconstructed motor center point to indirectly obtain the zero-crossing point of the back EMF. The implementation method is usually realized by using an analog comparator and related peripheral hardware circuits, thus increasing the cost of the system

The above reasons severely limit the application and popularization of brushless DC motor position sensorless control system

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