This paper investigates reduction of acoustic noise and cogging torque in a BLDC motor with larger stator slot open width. Using energy method, cogging torque is analytically determined with airgap MMF function and airgap permeance function and confirmed by FEM analysis. It shows that the cogging torque is firstly governed by NL GNL BNL with the fundamental period of NL, where NL is the least common multiple of the number of slots and the number of poles, GNL, airgap permeance function and BNL, airgap MMF function. It also shows that there exist several tooth width which minimizes the cogging torque, for the motors that smaller slot open width or stator teeth notching is not available. And it proposes a teeth pairing with two different tooth width which can effectively eliminate the cogging torque and thus the acoustic noise. Experimental results show that the proposed teeth pairing reduces the cogging torque by 85% and the acoustic noise by 3.1dB.

In order to design and predict the performance of the harmonic side drive motor, it is necessary to analyze the torque generated by the structure. In this paper, an analytical model is proposed for design. Conformal mapping is used to model the capacitance and torque of the motor as a function of the rotor angular position with two-dimensional approximation. Then the result of conformal mapping analysis is verified with F.E.M result.

This paper describes the effect of eddy currents in the rotor steel shell of exterior-rotor permanent magnet BLDC motor of which rotor is revolving at a high speed. A two-dimensional time-stepping finite element method is used for analyzing electromagnetic field and computing performances of the motor. As a result the effect of the eddy currents in the rotor steel shell is shown by comparing the analysis results from both the proposed method and the conventional one.

This paper describes the finite element procedure including the magnetic hysteresis phenomena. The magnetization-dependent Preisach model is employed to simulate the magnetic hysteresis and applied to each elements. Magnetization is calculated by the Fibonacci search method for the applied field in the implementation of the magnetization-dependent model. This can calculate the magnetization very accurately with small iteration numbers. The magnetic field intensity and the magnetization corresponding to the magnetic flux density obtained by the finite element analysis(FEA) are computed at the same time under the condition that these balues must satisfy the constitutive equation. In order to reduce the total calculation cost, pseudo-permeability is used for the input for the FEA. It is found that the presented method is very useful in combining the hysteresis model with the finite element method.

Speed and position sensors require the additional mounting space, reduce the reliability in harsh environments and increase the cost of motor. Various control algorithms have been proposed for the elimination of speed senor. This paper investigates a novel speed sensorless control of induction motor. The proposed control strategy is based on MRAS(Model Reference Adaptive System) using state observer as a reference model for flux estimation. This algorithm may overcome several shortages of conventional MRAS: integrator problems, small EMF at low speed and relatively large sensitivity to resistance variation. The proposed algorithm is verified through simulation and experiment.

Generally, the digital controller has many advantages such as high precision, robustness to electrical noise, capability of flexible programming and fast response to the load variation. In this study, we have established proper mathematical equivalent model of Brushless DC (BLDC) motor and estimated the motor parameter by means of the back-emf measurement as being the step input to the controlled target BLDC motor. And the validity of proposed estimation method is confirmed by the test result of step response. As well, we have designed the reasonable digital controller as a consequence of the root locus method which is obtained from the open-loop transfer function of BLDC motor with hall sensor, and the determination of control gain for variable speed control. Here, revised Ziegler-Nichols tuning method is applied for the proper digital gain establishment, and the system stability is verified by the frequency domain analysis with Bode-plot and experimentation.

This paper is on realization of the speed-sensorless vector control of an induction motor using the RLS(Recursive Least Square) algorithm. The speed estimator is including the RLS algorithm and a rotor flux observer. The RLS algorithm has speed and rotor time constant as parameter vectors and rotor flux observer is designed to have robustness to stator resistance variation and through the IP(Integral and Proportional) speed controller stable performance is obtained for estimating rotor speed. Finally the total algorithm are realized in induction motor drive system and its effectiveness is verified.