Smooth variable structure control of train systems

The impact of resistance forces on train operation performance becomes increasingly significant as the train speed increases, thus should be explicitly addressed in developing control schemes for high speed train systems. This paper presents a smooth VSC approach for automatic train speed and position tracking control under varying operation conditions. In contrast to most existing methods that either assume the availability of resistance forces for feedback control design, or consider constant resistance coefficients, we consider the case that the basic resistance forces and additional resistance forces are both time-varying and unknown. A smooth VSC method is proposed to achieve high precision position and velocity tracking. The fundamental idea behind this method is to directly design the control rate, instead of the control action itself, thus the chattering problem in most existing VSC methods is removed because the integration of the control rate smoothens the control action.