Numerical modelling of the rotor movement in a permanent‐magnet stepper motor

Abstract

This manuscript deals with predicting the dynamic behavior of the rotor in a claw-poled, permanent-magnet (PM), stepper motor. The FEM model of a prototype stepper is used to calculate the magnetic forces on the rotor, where the PM is modeled with an altered geometry approach. This altered geometry helps achieving a realistic magnetic flux density profile and direct PM material property input. The obtained forces are used in the following analysis as the excitation, to simulate the rotor's rotational and also axial movements with the help of proposed system of equations. To validate the introduced modeling approach, a measurement of the rotational and axial movement was performed on a motor with the same geometry and material properties. The results of the simulated movement are in good agreement with the experimental data for the tested motor.

Parametric Study of a Permanent-Magnet Stepper Motor’s Stepping Accuracy Potential

“…Due to these problems with the need of scaling the magnetic material properties and obtaining sinusoidal shaped magnetic density profile ( Fig. 4c) a simple method for changing the geometry of the PM was developed [15]. The segment's geometry and volume are changed to suit the volume portion of the magnetic material and also the inner and outer PM diameters.…”

“…The stepping simulation was performed with the help of a developed system of equations [15] that uses torque-displacement curves and the forcedisplacement curves obtained, as described in section 2.1, to simulate both the rotational and axial [17] movements of the rotor. Once the FEM results for torque-displacement and force-displacement curves are obtained and stored, any movement simulation can be quickly calculated using Eq.…”

“…In order to validate the proposed simulation method, a simple experiment allowing the measurement of the rotational displacement of the shaft was made [15]. The shaft of the motor was coupled with a Scancon miniature encoder using 10 -7 kgm 2 of inertia and 0.5 Nmm of friction torque.…”

“…12 consecutive steps are enough to see the motors poor stepping abilities. The schematics of experimental setup, additional measurements and model validation is available in previous work [15].…”

Effect of 3D Unidirectional and Hybrid SAGE on Electromagnetic Torque Fluctuation Characteristics in Synchronous Generator

“…However, the axial SAGE as well as the hybrid SAGE does exist in practice, though the eccentricity degree may not be so large. For example, [24] studied the axial movement (i.e., axial SAGE) and the axial electromagnetic forces of the rotor in hydro-generators, [25] investigated the axial rub-impact fault (which reflects the axial SAGE) in turbogenerator sets, [26] studied the axial movement of a stepper motor. It is actually easy to understand why axial SAGE could be caused in generators: fluid-solid-interaction will produce an axial force on the rotor and after a long-term impact the rotor will get an axial displacement (axial SAGE).…”