Objective The gap sensor measurement accuracy is directly related to the performance of the suspension control system of EMS (electromagnetic suspension) high-speed maglev train. In practice, the presence of cogging structure of track iron core may cause significant fluctuations in the output voltage, thereby reducing measurement accuracy; this phenomenon is referred to as the groove effect. Existing studies have mostly focused on suppressing the groove effect by optimizing structural design; however, this approach is difficult to implement and offers limited suppression effectiveness. Therefore, it is necessary to investigate a new suppression method.

Method Based on the fundamental operating principle and the circuit model of gap sensor, finite element models of gap sensor are analyzed using simulation software. Gap prediction is performed according to the output voltage signals, thereby verifying the existence of cogging effect. Harmonic analysis of the groove-effect waveform is conducted to obtain the main harmonic components and their amplitudes, and on this basis, a groove-effect compensation function suitable for the full gap range is constructed. The output voltages of two speed coils within a single levitation coil set are subtracted, then the differential voltage signals of two groups of levitation speed-coil with a phase difference of 1/4 cogging-slot width period are divided. The current positional information of the gap coil is calculated using inverse trigonometric functions. The obtained positional information is substituted into the compensation function, thereby achieving compensation of the measurement results.

Result & Conclusion  Using the output data from finite element simulations, and combining both the groove-effect compensation function and the positional information calculated from the levitation coils, the measurement accuracy error over the 2 - 20 mm full gap range can be reduced from 1.32 mm for scenarios without clogging-effect compensation to 0.40 mm, demonstrating that the accuracy after groove-effect compensation meets engineering requirements.