Comparison of two controllers for directional control of a hybrid electric vehicle
Directional response of a vehicle implies changing its direction when sustaining lateral acceleration while moving on the road. From this response, the vehicle's explicit capabilities as well as its contribution to the system performance of the driver/vehicle combination are obtained. In vehicle control literature, handling is often used interchangeably with cornering, turning, or directional response. This paper focuses one aspect of the handling i.e. directional response. Two different controllers, namely a PID controller and a Fuzzy Logic Controller (FLC) for a hybrid electric vehicle (HEV) are designed in this paper to control the vehicle's steering in a smooth lane change maneuver. The performances of the aforesaid two controllers have been studied extensively in this paper. For achieving an improved path tracking and directional response, parameters of both the PID and FLC have been tuned and their performances have been compared. Further, the effect of changing the scale factors in the fuzzy logic approach to obtaining directional response is presented. To validate the above two control performances, a nonlinear simulation model of a HEV is developed and is used in simulation studies. Both the controllers track the desired directional signal efficiently. Both PID and Fuzzy controllers provide competitive performances. Although with the assumption of all parameters of the vehicle available PID controller exhibits slightly better dynamic performance but in the real-world scenario the fuzzy controller is preferred due to its robustness i.e. it does not depend on the parameters of the vehicle.