Comparative analysis of methods for computing pole angle offsets in magnetic pole wheels using ABS sensor

Magnetic pole wheels, that are typically used in vehicles to measure speed, have inherent manufacturing intolerance resulting in variable pole length in each pole wheel. Moreover, due their use in harsh and prone to dust environment, magnetic characteristics of each pole change over a period of time. This gives rise to change in pole pitch reported by the ABS sensors. The target here is to accurately measure pole angles by analyzing the ABS sensor signal. This paper describes two methods to achieve optimum pole angle or offset calculation by Synchronous Averaging and Kalman Filter accompanied by a novel Pole Skipping technique to compensate for the speed variations. The computed pole angles can be used to calculate the speed signal more accurately. Besides that, application of pole offset correction will remove the regular pattern from the speed signal data, which prevails in its spectrum suppressing important information related to tire vibrations.