Force ripple compensation of linear synchronous motors

Linear synchronous motors are finding expanded use in high-performance applications where high speed and high accuracy is essential. The main problem in improving the tracking performance of linear synchronous motors is the presence of force ripple caused by mismatched current waveforms and unbalanced motor phases or amplifier gains. This paper presents a method to optimize the waveform of the phase currents in order to generate smooth force. The optimized current waveforms produces minimal copper losses and maximize motor efficiency. The waveforms are implemented in a waveform generator of the motion controller and approximated with Fourier series. The optimization method consist of three stages. In every stage, different harmonics of the force ripple are reduced. A comparison of the tracking performance with optimized waveforms and with sinusoidal waveforms shows the effectiveness of the proposed method.