Rakib Islam

Analytical Model for Predicting Noise and Vibration in Permanent-Magnet Synchronous Motors

This paper analyzes the noise and vibration in permanent-magnet synchronous motors (PMSMs). Electromagnetic forces have been identified as the main cause of noise and vibration in these machines, rather than the torque ripple and cogging torque. A procedure for calculating the magnetic forces on the stator teeth based on the 2-D finite-element (FE) method is presented first. An analytical model is then developed to predict the radial displacement along the stator teeth. The displacement calculations from the analytical model are validated with structural finite-element analysis (FEA) and experimental data. Finally, the radial displacement is converted into sound power level. Four different PMSM topologies, suitable for the electric power steering application, are compared for their performances with regard to noise and vibration.

Noise and Vibration Characteristics of Permanent-Magnet Synchronous Motors Using Electromagnetic and Structural Analyses

This paper provides a detailed finding of the mechanics of vibration in permanent magnet (PM) synchronous motors due to electromagnetic (EM) origins. Several fractional-slot PM topologies are investigated to quantify the vibration phenomenon that is influenced by motor slot/pole and winding configurations. This paper also sorts out the vibration mode order that is responsible for deformation and the resulting excitation frequency. A finite-element-based cosimulation in the EM and structural domain is used to find the radial forces and, hence, the displacement, to quantify the vibration/noise performance of these selected motors. The displacement and frequency are converted to the sound pressure level to show the relative differences in the noise levels among these motor topologies. The selected motors were experimentally tested to verify the theoretical findings.

Cogging Torque Minimization in PM Motors Using Robust Design Approach

Cogging torque minimization is necessary for low torque ripple applications such as precision tooling, robotics, etc. Various techniques are available but few techniques are proved to be effective in mass production under manufacturing tolerances/variations. The research provides a design approach to minimize cogging torque by making the motor robust to manufacturing variations and dimensional tolerances. Several control and noise factors are identified to apply the robust design technique. The quality of robustness is judged by the signal-to-noise ratio. A tradeoff is exercised to maximize output torque in selecting the control parameters. The research shows the effectiveness of such design techniques in designing motors for mass production without adding cost or complexity. Experimentation by modeling has been chosen using finite element analysis. Motors using the optimized parameters are built and tested thus verifying the design approach.

Experimental Verification of Design Techniques of Permanent-Magnet Synchronous Motors for Low-Torque-Ripple Applications

High-performance motor drive applications require smooth operation with minimum torque ripple. This paper is focused on identifying various design parameters in the stator and rotor that can be utilized to reduce the torque ripple of sinusoidally excited permanent-magnet synchronous motors. This paper investigates the sensitivity of various design parameters on torque ripple and torque linearity that must be considered at the design stage for low-torque-ripple applications. Only the torque ripple and torque nonlinearity due to electromagnetic origin are considered in this paper. Finite-element analysis along with experimental data is provided to validate the findings. Design techniques have been provided to minimize the overall torque ripple and increase the torque linearity. Tradeoff between magnetic flux per pole and electrical loading of the machine is needed for low-torque-ripple performance. This also provides superior torque linearity.

Noise and vibration characteristics of permanent magnet synchronous motors using electromagnetic and structural analyses

This research provides a detailed finding of the mechanics of vibration in permanent magnet synchronous motors due to electromagnetic origins. Several fractional slot PM topologies are investigated to quantify the vibration phenomenon that is influenced by motor slot/pole and winding configurations. The research also sorts out the vibration mode order responsible for deformation and the resulting excitation frequency. A finite element based co-simulation in electromagnetic and structural domain is used to find the radial forces and hence the displacement to quantify the vibration/noise performance of these selected motors. The displacement and frequency is converted to sound pressure level to show the relative differences in noise levels among these motor topologies.

Analytical Model for Predicting Effects of Manufacturing Variations on Cogging Torque in Surface-Mounted Permanent Magnet Motors

In a mass production environment, due to the manufacturing tolerances, additional orders of cogging torque are created in addition to the fundamental components. The tolerances lead to asymmetry conditions both in the rotor as well as in the stator. Finite-element models can be used to analyze the cogging generated due to these asymmetries. However, it is extremely time consuming to study this uneven geometry numerically since periodicity and symmetry conditions cannot be used to reduce the model. Moreover, the experimental verification of all possible variations would be very challenging, as it would require part dimensioning, part sorting, a large quantity of motor builds, and finally testing of all samples. Therefore, in this paper, an analytical model is presented to study the effect of such imbalance on the cogging torque. The model is validated against finite-element models and also with experimental results.

Inter winding short circuit faults in permanent magnet synchronous motors used for high performance applications

This paper examines the effect of all possible stator winding short circuit conditions on the performances of permanent magnet synchronous motors (PMSM) used in high performance applications like aerospace, automotive, medical and military. The study identified stator fault due to insulation failure and categorized them into turn-to-turn, phase-to-neutral, phase-to-phase and all phases short circuit conditions. Two types of winding configuration are considered to address the transient torque capabilities of a particular PMSM design. The transient behavior of the short-circuited motor drive is characterized analytically with a simple circuit model. The analytical model is then verified using 2D finite element analysis (FEA). Finally, few scenarios of the fault conditions are created in a real motor to validate the analysis. Also, the severity assessment of such faults is extended towards two different kind of winding arrangement commonly used for PMSMs.

Vibration and torque ripple reduction of switched reluctance motors through current profile optimization

This paper proposes a differential evolution (DE) optimization-based current profiling method for simultaneous reduction of the torque ripple and vibration of switched reluctance motors (SRMs). The mechanism of torque generation in SRMs produces radial forces in addition to the required tangential force. It has been shown that the radial forces acting on the stator are the main vibration source in SRMs and keeping the sum of the radial forces constant can reduce the magnitude of the significant harmonics of the sum of radial forces and further reduce vibration by avoiding the resonance caused by those harmonics. A simple method is proposed to model the torque and radial forces generated in the SRMs while considering the saturation effects. The resulting torque and radial force models are then used in the DE optimization process to generate the current profile of each phase in the form of Fourier series, where the Fourier coefficients of each phase current profile are determined to minimize the torque ripple and significant harmonics in the sum of the radial forces. The proposed method significantly reduces the computational cost of the finite element analysis (FEA)-based methods. The effectiveness of the proposed method is verified through both FEA simulation and experimental results.

Cogging torque minimization in PM motors using robust design approach

Cogging torque minimization is necessary for low torque ripple applications such as precision tooling, robotics etc. Various techniques are available but few techniques are proved to be effective in mass production under manufacturing tolerances/variations. The research provides a design approach to minimize cogging torque by making the motor robust to manufacturing variations and dimensional tolerances. Several control and noise factors are identified to apply the robust design technique. The quality of robustness is judged by the signal-to-noise ratio. A trade-off is exercised to maximize output torque in selecting the control parameters. The research shows the effectiveness of such design techniques in designing motors for mass production without adding cost or complexity. Experimentation by modeling has been chosen using finite element analysis. Motors using the optimized parameters are built and tested thus verifying the design approach.

Effect of radial asymmetry of magnets in surface-mounted permanent magnet motors on cogging torque

During the mass production of surface-mounted permanent magnet motors the rotor and stator geometrical dimensions usually deviate from their nominal values due to manufacturing tolerances which impact machine performance. One such common tolerance can be noticed in the placement of the permanent magnets on the rotor surface which creates new orders of cogging torque. Finite element models can be used to analyze the cogging generated due to the asymmetry in the magnet placement. However, it is time consuming to study the effect of imbalance of each magnet numerically since periodicity and symmetry conditions cannot be used to reduce the model. Therefore, in this paper an analytical model is presented to study the effect of such imbalance on the cogging torque. The model is validated against a finite element model and also with experimental results.