Line back-EMF Research Articles

Design study of an aerospace motor for more electric aircraft

This study proposes an improved power density permanent magnet synchronous motor (PMSM) for more electric aircraft (MEA) and conducts a design study on aerospace motors. To improve the power density of PMSM, a dual permanent magnet structure using high-temperature resistant high-performance permanent magnets and high-performance soft magnetic alloy material is creatively designed. Methods of lightweight structure designed in both stator and rotor meanwhile are combined as another mean to increase power density. The optimisation models for 6-slot/8-pole and 12-slot/10-pole configurations are first established based on finite element analysis. Methods of improving the power density of PMSM are then given, including minimum core back yoke thickness and lightweight structure design. The electromagnetic characteristics of the optimised machine are analysed by finite element analysis software, including back electromotive force (back-EMF), inductance, and power loss. The configuration of 12-slot/10-pole is selected as the best design scheme for MEA, based on which a prototype is manufactured and tested. The experiment results of cogging torque and line back-EMF are in good agreement with the simulation results, which shows the rationality of the designed new machine. The design proves to be effective for improving the power density of aerospace motors.

Design and fault tolerant analysis of five-phase permanent magnet synchronous motor

<span lang="EN-IN">This paper presents a design of 15-slot/12-pole, five-phase, surface-mounted permanent magnet synchronous motor (PMSM). The five-phase PMSM can be an attractive solution to few applications that demand fault tolerant capability such as in aerospace engineering and electric propulsion. The motor model is first investigated based on the implementation of analytical method. The analytical method derived from the subdomain model of the permanent magnet machine is initially applied to estimate the magnetic flux density distributions for the radial component <em>B</em><sub>r</sub> and the tangential component <em>B</em><sub>t</sub> in the machine air gap. Other important motor characteristics such as phase back-EMF, line back-EMF, cogging torque and electromagnetic torque are also calculated. The analytically calculated results are then compared with the numerical method in a 2D finite element analysis. Additionally, the capability of this PMSM model against faulty conditions are further investigated. The results show that the analytical model of the 15-slot/12-pole, five-phase PMSM provides very accurate motor performance within acceptable error margin. For instance, the average electromagnetic torques, inclusive of the cogging torque, as computed by the analytical and numerical methods are 5.53Nm and 5.33Nm respectively, yielding an error of 3.6%. During faulty conditions, the PMSM can possibly continue to operate with lower output torque, about 60% to 80% of its rated torque, when one-phase or two phase windings are out of service.</span>

High Load Fast Startup Sensorless Control of Wheel BLDC Motor with Line-to-Line Back EMF Extraction Using Least Pth-Norm IIR Digital Filter

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 [Formula: see text]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[Formula: see text]rpm in voltage control mode and 85[Formula: see text]rpm in current chopping PWM mode. Approximately 85[Formula: see text]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[Formula: see text]ms between phase currents has been achieved during commutation period.

Design and Research of a Sliding Mode Observer Based on Line Back-EMF for Brushless DC Motors

This paper designs and implements a sliding mode observer with line-to-line trapezoidal back-EMF for brushless DC (BLDC) motor. Through the detection of three phase voltage and the current, the phase to-phase back-EMF is observed, and then the position signal and the rotor speed are estimated. The corresponding relationship between back-EMF and six rotor positions of the motor is established in this paper. With saturation function instead of sign function, the line current difference is used as the sliding surface. The whole control system employs an inner current PI loop with an outer speed PI loop. Simulation results show that the designed observer can correctly estimate the position information and speed, with strong robustness to changes of system parameters and external disturbances.

Speed Control for Four Quadrant Operation of Three Phase Bldc Motor Using Digital Controller

This paper proposes a method that estimates rotor position by using an unknown input observer over a full speed range. In this method, a trapezoidal back emf is modeled as an unknown input and the proposed unknown input observer estimating line to line back emf in real time makes it possible to detect the rotor position. This observer has high performance even at low speed range because rotor position is calculated independently of the rotor speed without adding any additional circuit or complicated operation process. Simulations have been carried out for the verification of proposed control scheme. MAT LAB/SIMULINK model is used for software simulation. Keywords-BLDC motor, Four quadrant operation, sensorless control, full speed range, unknown input observer.

Rotor Position Phase Correction for Sensorless Brushless DC Motor Based on Line Back EMF

This paper proposes a novel rotor position estimation method based on line back EMF for brushless DC motor (BLDCM). The relationship between position phase error and the symmetric line back EMF is analyzed. It is noted that line back EMF error can exactly reflect rotor position phase error. If the amplitude of line back EMF at the beginning of commutation is equal to the amplitude of line back EMF at the end of commutation, the waveform of line back EMF should be symmetric. Based on the above analysis, a closed loop control method to correct rotor position phase is presented. Line back EMF error is employed to keep the waveform of line back EMF symmetrical by PI controller. This paper also develops a sensorless BLDCM driver to implement the proposed method based on DSP and the experimental results prove the validity of the proposed method.

Line back-EMF oriented 6/4 pole PMA-SynRM drive based on third harmonic current injection

This paper presents a line back-EMF oriented current vector drive (LBOCVD) that increases torque density and reduces acoustic noise in a three-phase 6/4 pole permanent magnet-assisted synchronous reluctance motor (PMA-SynRM). To implement LBOCVD, three-phase Y-connected windings are excited by three-phase sinusoidal currents with third harmonic component. Torque angle measurement (TAM) is used to control the motor's space current vector, thereby regulate its loading and increase the system's overall efficiency. To verify the high-performance of the proposed drive, a 400 W three-phase 6/4 pole SRM and a PMA-SynRM were operated at the rated load and below 2500 rpm. Experimental results showed that the SRM drive generated maxima of 96 dB acoustic noise, 16 kg cm torque, and 65% system efficiency. In contrast, the PMA-SynRM drive yielded maxima of 70 dB acoustic noise, 30 kg cm torque, 93% system efficiency, and 0.8% steady speed error. The proposed drive is thus very useful for industrial products geared toward energy saving. Copyright © 2010 John Wiley & Sons, Ltd.