Allowed sloppy magnet placement due to learning control

Linear motors are typically used in applications that require high speed, high force and high precision actuation. A linear synchronous motor consists of two parts, the moving part and the stationary part. The motor we investigated had permanent magnets fixed on the stationary part. To generate a force, a three phase current has to be applied with a certain phase depending on the position. To increase this force, iron-core coils are used that bundle the flux. The permanent magnets in the stationary part attract these iron which results in cogging forces. The motor has preference positions due to this attraction. By skewing the permanent magnets this effect can be minimized [1], however, at the cost of a smaller peak force. If the magnets are placed with small tolerance and the generated magnetic field would be equal, the cogging force would be periodic. This would mean that the cogging force is known before-hand and can be compensated for. However this would require a set of tightly toleranced magnets that are placed accurately.