Design of Electromagnetic Actuators Using Layout Optimization With Distributed Current Source Models

This paper presents a layout optimization method for maximizing the torque-to-weight ratio of an electromagnetic actuator. Layout optimization, which focuses on finding practical designs to maximize output performance in a compact design, avoids nonlinearity and local convergence problems in the optimization of the electromagnetic system using two sequential steps; linear topology optimization and integer programming. Formulated in terms of decomposed volume and surface elements with equivalent current sources, the linear topology optimization optimizes the permanent magnet material distribution in the rotor. With the linearly optimized designs, integer programming determines the “most preferred” design in the second step by evaluating performances over design complexity. As illustrations, the method is applied to maximize the torque performance of two different three-phase disk-shaped synchronous motors. The effects of two different current waveforms, sinusoidal and square wave, on the torque magnitude and ripple are considered in the optimization. The design method has been experimentally validated by comparing simulated results of the layout optimization with measured magnetic field and torque output. This component-wise method that maximizes the net force/torque averaged over various orientations represents an improvement over existing algorithms where topology optimization is conducted at a specific rotor orientation to reduce the computational cost.