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Summary: Sensorless control of BLDC motors is preferred nowadays due to a number of drawbacks in sensor based control. Line‐to‐line back EMF is generally extracted by filtering the terminal voltages. In case of high‐speed operation, the phase delay becomes very large and result in imprecise commutation with large phase currents, high torque ripple, and reduced efficiency. In such case, linear strategy of commutation advancement alone cannot be successful. In this paper, a Fuzzy based phase delay compensation scheme has been proposed. The smooth variation of coefficients of the least Pth‐Norm IIR digital filter is achieved using close loop Fuzzy control for operation from low‐ to high‐speed range without commutation precision loss. This enables the increase of filter cut‐off frequency and gain to overcome the phase delay and attenuation at higher speeds. The commutation delays may still be present even after phase delay compensation because of filtering frequency limitation to avoid the effect of spikes occurring due to diode freewheeling. Equal area criterion (EAC) has been proposed for commutation error correction. The required correction in threshold constant is calculated by difference of ripple current integral before and after the valley point. The controller has been developed using MATLAB/Simulink and validated using real‐time windows target NI PCI‐6221 DAQ and 400 W, 12000 rpm brushless spindle motor. Experimental phase delay of 13.6° and commutation error of 2° was achieved after application of EAC at 11250 rpm. The proposed system provides higher efficiency with reduced startup time. [ABSTRACT FROM AUTHOR]

In this paper, an effective scheme of on-load startup with reduced current has been proposed for BLDC motor and the steady as well as dynamic performance in all four quadrants was verified. Hysteresis band-limited back EMF noise provides the starting pulses, the frequency of which depends on the threshold factor in speed proportional threshold. Scheme is quite fast, comparatively to the state-of-the art schemes of startup and less complex than time-consuming initial position detection (IPD) algorithm. Second-order least P th-norm infinite impulse response (IIR) digital low pass filter realized in MATLAB/Simulink has been used for extraction of line-to line back EMF from line-to-line terminal voltages measured with two voltage sensors. Proposed filter has wide flexibility of online variation of cut-off frequency, gain and phase without any circuit-based modification due to variability of filter coefficients. This enables the smooth filtering with minimized phase delay in low speed range irrespective of any duty cycle and PWM frequency. Linear compensation of phase error or phase advancement for desired current profile can easily be achieved by the varying the threshold factor. In this experiment, the threshold factor of 1/1460 has been found most suitable for smooth sensorless startup without jerk, vibration and reverse rotation, as the motor operates in advanced mode with this value. First, the performance of Hall sensor-based drive was studied using open loop variable duty cycle speed control. The controller was designed in MATLAB/Simulink platform and implemented using TMS320F28069M DSP control stick with Code composer Studio V5. Later on, a complete controller for proposed sensorless scheme was developed in MATLAB/Simulink environment and was implemented using NI-PCI6221 Controller installed in PC. The proposed sensorless drive has been found capable of operating at very low speed of 50 rpm in voltage control mode and 85 rpm in current chopping PWM mode. Approximately 85 ms less time was taken by sensorless drive to reach the same speed when compared with Hall-based control for identical loading. Also less overshoots during startup was observed. Overlap time of 0.05 ms between phase currents has been achieved during commutation period. [ABSTRACT FROM AUTHOR]