Longitudinal control of hybrid electric buses using traction motor and pneumatic braking system

Additional energy source of hybrid electric buses comprises new control tasks. One of the main challenges of hybrid electric buses is the integrated control between traction motor and brakes, associated with which is the problem of switching traction motor and brakes. Existing control techniques only provide a result of frequent switch and jerky ride. In this paper, we propose a control strategy including two control laws, which are calculated simultaneously to optimize a certain tracking criterion by a fuzzy adaptive algorithm. Considering parametric uncertainties, the two control laws are used to determine whether to activate the traction motor or the pneumatic brake. The stability and convergence properties of the longitudinal brake control system are analytically proved by using Lyapunov stability theory and Barbalat's lemma. We examine the proposed algorithm with different mass uncertainties and the simulation results demonstrate stable behaviors when two buses drive into a bus station.