On-line compensation of magnetic position sensor using recursive least square method

This paper presents the error correction method for magnetic position sensor using recursive least square method (RLSM) with forgetting factor. The magnetic sensor modules are proposed for linear position detection of the linear motor which has tooth shape stator. The modules are consists of permanent magnet, iron core and linear hall sensor and generates sine and cosine waveforms according to the movement of the mover of the linear motor. From the output of magnetic sensor modules, the position of the linear motor can be detected using arc-tan function. But the variation of the air gap between magnetic sensor modules and the linear motor stators, and some errors in manufacturing process can cause the variation in offset, phase and amplitude of the generated waveforms when the linear motor moves. These variations in sine and cosine waveforms are changed according to the current linear motor position, and it is very difficult to compensate the errors using constant value. In this paper, the generated sine and cosine waveforms from the magnetic sensor modules are compensated in real time using the RLSM with forgetting factor. And the speed observer is introduced to reduce the effect of uncompensated harmonic component. The proposed methods are verified by some simulations and experiments.