Comparison of locomotive adhesion force estimation methods for a wheel slip control purpose

Locomotives are equipped with slip controllers to limit a value of a wheel slip velocity and conducive to reach required locomotive tractive effort. The slip control methods are developed for tenths years, and the methods are based on several principles. Progressive methods determine an adhesion-slip characteristic slope. This method requires knowledge of an adhesion coefficient value or an adhesion force value. These quantities cannot be measured directly during the train run. Therefore, these quantities are estimated by some estimation techniques. A Kalman filter or its nonlinear variants as an extended Kalman filter or an unscented Kalman filter can be used as estimators of the quantities. Every filter has different features, and the estimated output is different. The filters performance during adhesion estimation for a locomotive slip control is presented in the paper. The comparison of the filters is made for various filters setting. The comparison is based on measured data as offline simulation in Matlab software.