Analysis and Compensation of End Effects for Improved Force Control of Linear Machines

Experimental setups have shown that a non-sinusoidal back-EMF influences the operation and efficiency of permanent magnet machines. Compensating for the negative effects is a common research topic. In the paper at hand the end effects of linear machines, caused by the limited stator and mover lengths, are analyzed. The resulting non-sinusoidal and asymmetric flux linkage and accompanying fluctuating back-EMF were described. To avoid that these effects have an impact on the drive system with a linear machine, a method of compensating them was analytically derived. Three compensation methods with different requirements and efficiency were described. In simulations was shown, that adapted field orientation transformations could be used to achieve smooth output force while reducing necessary current. An experimental implementation was successful and the theoretical considerations regarding the energy efficiency could be proved.

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