Structural Expression Code Method And Its Application In Optimal Design Of Permanent Magnet In PMSM

In designing of permanent magnet synchronous motor,how to obtain the required distribution of magnetically dense precisely though variation of permanent magnet structure is a big challenge.The existing methods only do optimization for parameters under a fixed or several fixed structures.However,no optimization is done concern both structure and parameters simultaneously.In this thesis,structural expression code method is proposed.It can encode the structure and parameters simultaneously,realizing the optimization of the real structure scheme and parameters at the same time.The structure and parameters of the rotor permanent magnet are encoded as fixed length nonlinear strings(symbols and variables).Different strings can be decoded into different structure expression trees,and each structure expression tree corresponds to the structure and parameters of a rotor permanent magnet.In this thesis,the air-gap magnetic density waveform generated by sine wave is taken as the target.The structural expression code method is proved by optimizing the structure and parameters of permanent magnet for permanent magnet synchronous motor combined with genetic operator and evolutionary framework.The simulation result obtained by finite element method shows the optimal designed permanent magnet shape produces an air gap flux density waveform whose sinusoidal distribution is 99.78%.