Optimized fuzzy controller for a power-torque distribution in a hybrid vehicle with a parallel configuration

In this study, an optimized fuzzy controller was designed for a power-torque distribution in a hybrid passenger vehicle using the bees algorithm. For this purpose, a dynamic model for a parallel hybrid vehicle, including an internal-combustion engine, an electric motor and battery, a torque converter, a continuously variable transmission, torque-speed coupling and wheels (forward dynamic), is built. To simulate the driver's skill and performance when facing different conditions, a fuzzy controller (which is called the first-layer controller) is used. On the one hand, decisions made by the first-layer controller are a function of the desired acceleration, the desired speed and the speed error and, on the other hand, they depend on the vehicle's performance mode. The vehicle's performance mode is determined with regard to the charged condition (the state of charge) of the batteries, the vehicle's required power and the driver commands by another fuzzy controller which is called the second-layer controller. The necessary commands for the subsystems such as the throttle angle, the controller command for the electric motor and the appropriate speed ratio in the continuously variable transmission are determined by another controller, called the third-layer controller. Both the first layer and the second layer are optimized using the bees algorithm. According to the results, the optimized controller indicates an appropriate performance based on the defined rules in different situations. It also improves the vehicle's performance parameter and decreases the fuel consumption and the pollutions produced by the engine.