Anew scheme sensorless control of BLDC motor using software PLL and third harmonic back-emf

Abstract

High performance sensorless permanent magnet brushless DC motor operation requires proper and precise commutation sequence. In general, the average torque falls rapidly as the rotor speed increases above the base speed, hence the motor will frequently be found to have insufficient torque at higher speed. One way to counter this problem is by using third harmonic back-emf detection technique during high speed operation because the third harmonic is usually kept a constant relationship with rotor position for any motor speeds and load conditions. Therefore, we could potentially avoid the torque deterioration which commonly occurs in traditional sensorless technique due to the delay of the phase angle between current and back-emf. Furthermore this method is practically free of noise which may be introduced from inverter switches. In this work, we propose a new software scheme of phase-locked loop (PLL) of third harmonic back-emf detection in order to accomplish a precise switching strategy for improving torque produced during high speed operation.Keyword-brushless direct current (BLDC) motor, sensorless control, third harmonic back electromotive force (EMF), phase-locked loop(PLL).

Sensorless Control of Outer Rotor Brushless DC Motor With Back-EMF Observer for Drone

“…Complex algorithm expressions required for field-oriented control cause limited use due to memory size in microprocessors [13]. In the 3rd Harmonic detection method, which is another control method, the fact that the 3rd Harmonic has 3 times the frequency of the 1st Harmonic caused errors due to the low-pass filter, thus reducing a sensitivity of this system [14]. Apart from these disadvantages, starting the motor becomes a problem as a result of the absence of the back emf signal at low speeds.…”

Position sensorless and adaptive speed design for controlling brushless DC motor drives

“…Although Hall sensors are the best type of sensors for BLDC motors due to soft starting, it has several drawbacks, such as: cost, sensitivity to the temperature, and unreliable performance in industrial areas. To overcome these problems diverse approaches have been addressed in articles [9][10][11][12][13][14][15][16]. For example, the proposed methods for folding trace technique of Magnet Resistors as well as shielding for Hall effect sensing element [17] could enhance bandwidth for advanced current controlling schemes.…”

Influence of Stator Current and Machine Saliency on Sensorless Control Performance Based on Third-Harmonic Back-EMF

“…Several sensorless control technologies based on third harmonic back-EMF have been proposed recently [5][6][7][8][9][10][11][12][13]. Shen in [5,6] presented the application for flux-weakening and ultrahigh speed sensorless control.…”