Fuzzy-logic-based control applied to a hybrid electric vehicle with four separate wheel drives

The authors present a detailed modelling study and a control system for a hybrid electric vehicle with four separate wheel drives. This configuration allows an improvement in the operability and thereby the safety of vehicles either during cornering or under slippery road conditions. Using electric motors it is possible to implement a quick and precise torque control. In order to obtain a better and precise dynamic performance a combined strategy Slip-ESP (electronic stability program) is created. A ´fuzzy estimator of vehicle speed´ which assures the reference vehicle speed used in the control system is also presented.