Analysis of sensorless control of brushless DC motor using unknown input observer with different gains

Abstract

A sensorless control scheme based on an unknown input observer is presented in this paper in which back EMF of the Brushless DC Motor (BLDC) is continuously estimated from available line voltages and currents. During negative rotation of motor, actual and estimated speed fail to track the reference speed and if the corrective action is not taken by the observer, the motor goes into saturation. To overcome this problem, the speed estimation algorithm has been implemented in this paper to control the dynamic behavior of the motor during negative rotation. The Ackermans method was used to calculate the gains of an unknown input observer which is based on the appropriate choice of the eigenvalues in advance. The criteria to choose eigenvalue is to obtain a balance between faster convergence rate and the least noise level. Simulations have been carried out for different disturbances such as step changes in motor reference speed and load torque. The comparative simulation results clearly depict that the disturbance effects in actual and estimated responses minimizes as observer gain setting increases.

Hardware implementation of interconnection and damping assignment passivity-based control for BLDC motor using microcontroller

“…Figure 1 shows the phase-currents and back-EMFs waveform of the BLDC motor. The three phase currents are controlled to take a type of quasi square waveform to synchronize with the trapezoidal back EMF to produce the constant torque according to the rotor position (Astik et al , 2017). Equation (4) represents the relationship between the three-phase back EMFs and flux functions for the BLDC motor and can be expressed by: where f a ( θ ), f b ( θ ) and f c ( θ ) are the flux functions with respect to the angular position and f abc ( θ ) is the notation for generalized flux function altogether.…”

“…Several speed and torque estimation methods have been presented in literature (Astik et al , 2017; Astik et al , 2018; Chun et al , 2014; Ogasawara and Akagi, 1990) to regulate the dynamic behavior of the brushless direct current (BLDC) motor. The method based on back electromotive force (EMF) estimation may not give satisfactory output during starting and low-speed operations.…”

Development and Implementation of a Low Cost μC- Based Brushless DC Motor Sensorless Controller: A Practical Analysis of Hardware and Software Aspects

“…Thus, the signals must be shifted in phase by 90 • electrical, before they will be used for commutation. In order to overcome the phase-shifting problem different methods have been presented in the literature, including the detection of the third harmonic component in back EMF, direct current control algorithm and phase locked loops [8,12,28,29]. Nevertheless, as stated in [14], BLDC motor systems are typically applied to low-cost systems of small capacity.…”