Compensation of Disturbances in Segmented Long Stator Linear Drives using Finite Element Models

Linear drives traveling on a carriageway with curves and closed paths are proposed for process integrated material handling. High precision and high throughput are required for this type of application. The long stator of the proposed permanent magnet synchronous machine is divided into many segments, each is fed by an inverter. When a vehicle enters a new segment, its EMF acts as a ramp-type disturbance for the current controller. Furthermore, asymmetries in the magneto motive force distribution are observed at the beginning and at the end of a segment. Also slot harmonics act as a considerable source of disturbance for the current control loop. To compensate these disturbances, the classical P-I current controllers should be supported by feed forward signals. In this paper, the feed forward signals are generated by a series of 2D finite element calculations. The geometrical data are taken from an experimental machine. As result of the FEM-calculations, look up tables where implemented in the control program and tested at the experimental setup. The experimental results show the effectivity of the feed forward