Wheel slip control based on traction force estimation of electric locomotives

In the development of control strategies for traction control in railway systems or locomotive applications, the dynamic interaction is known as traction force coefficient between the wheel and the rail must be carefully considered. Identification of the traction force coefficient between a railway wheel and rail track is a challenging task because of the difficulty in its measurement directly. Railway systems experiences wheel slip due to their acceleration and deceleration and also due to rail surfaces. Therefore, the traction force coefficient is an important factor in maintaining high acceleration and braking performance of railway. This study proposes a new approach to estimate the traction force coefficient using a Kalman Filter structured to included unknown input and then utilize the traction force between the wheel and rail where it reaches the maximum traction force level which is an adhesive force. For proper acceleration or braking of the wheel, the driving torque should be kept near to the adhesive level for the desired anti-slip control. Consequently, the motor drive system is required to make an instant and fast torque control to adjust the speed of a railway vehicle. The focus of this research project is to develop a dynamic model of the wheel slip controller that will be subsequently used to design a model for an induction motor driven locomotive.