Reduction of detent force in flat permanent magnet linear synchronous machines by means of three different methods

This paper proposes two different techniques to reduce detent force in flat permanent magnet linear synchronous motors (PMLSM). The first one is the choice of an optimal constructive design, taking into account the width and arrangement of the magnets, and the length and shape of the solid iron core. The second is the employment of a force compensator in the control algorithm, which counteracts the detent force effects. Both methods are based on a Fourier analysis of the detent force curve as a function of the machine position. The curve is broken down into harmonics. The constructive method considers that each harmonic has its peculiar source and is independent from the others. The force compensator employs a detent force model based on the Fourier series of the curve. The two methods were tested separately, and their results were compared. Experimental tests were performed to verify the effectiveness of the methods. A very important reduction with a constructive optimization of the machine was achieved. The reduction by means of a compensator in the control scheme also reaches excellent results. In order to achieve the maximum reduction of detent force, both techniques can be combined. This measure will increase the precision features of this kind of machine.