Proposal of Torque-Correct-by-Construction Optimization Method for Axial Flux Machines

We propose an innovative optimization method for axial flux machine that keeps the output torque constant in the process of weight reduction. A concept of framework is introduced that provides guidance for optimization design on how to choose and redesign the relevant parameters. Unlike the conventional algorithms that search candidates in sample space, new designs with reduced weight are directly determined by following the developed optimization strategy using two-dimensional finite element analysis (FEA). The torque error is restricted by a maximum allowable error introduced in the framework. A single-sided axial flux permanent magnet synchronous machine is used as a starting design. A total of 29 new designs are derived with gradually varying optimization variables. The optimization trend and limit are investigated with respect to the redesigned parameters as well as the resulting weights, which provide an overview for selecting optimal design. At last, the torque of every design is verified by both two-dimensional and three-dimensional FEA. The effectiveness of proposed method is demonstrated by the result that the weight is significantly and continuously reduced as the independent optimization variable increases while the torque error remains in a small extent.