Improving Wheel Speed Sensing and Estiamtion

Abstract: This master thesis project commissioned by Haldex Brake Products AB (in Landskrona, Sweden), and in association with the Department of Automatic Control, Lund Institute of Technology, deals with the problem of correct wheel speed measurements. Investigation into different types of sensors, Inductive-, Hall Effect- and Magneto-Resistive sensors have been carried out, which are sensors that may be used, when measuring the velocity of a wheel. It also looks into different types of methods that can be used to estimate a velocity; zero detection, estimation with few measurements, and tracking demodulation. Problems, such as noise, time demanding calculations and adapting the sensor signal so it may be used in a microcontroller, which could arise when implementing these methods into a microcontroller, are also investigated. The conclusions are that to obtain wheel speed estimates at low speed sufficiently fast, the information in the sinusoidal signal from the sensors has to be used, and therefore, if one sensor is used, the Few Measurements method is the most appropriate, and if two sensors are used the Tracking Demodulation method. Finally scheduling is suggested, which means that the normal zero detection is used at high speed and the tracking demodulation method is used at low speed.