Speed Control of Hybrid Electric Vehicle using cascade control of Fractional order PI and PD controllers tuned by PSO

A nonlinear hybrid electric vehicle (HEV), taken as a challenge due to its uncertainty in speed control, is controlled using cascade control loop of FO-PI (Fractional order PI) and FO-PD (Fractional order PD) controllers in this research. HEVs have a combination of mechanical and electrical subsystems arranged in cascade configuration. Mechanical subsystem consists of dynamics of vehicles and electrical subsystem comprises of Electronic Throttle Control System (ETCS). The other controllers evaluated are fractional order PID (FOPID), classical PID and PI cascaded with PD (PI-PD). The gains of the proposed and other controllers are tuned by Particle Swarm optimisation algorithm (PSO). Performance is examined for tracking of speed profile trajectory, rejection of disturbance phenomenon. Different performance parameters such as IAE (Integral of Absolute Error), OS (Overshoot), Rise time, Settling time are measured for examining behaviour of different controllers designed for controlling the speed of HEVs. The IAE of FOPI-FOPD tuned by PSO is 17.077 is least amongst the IAE of FOPID, PI-PD, PID tuned by PSO with values 22.771, 25.250, 29.134 respectively for set point tracking profile. The results show that FOPI-FOPD controller tuned by PSO has superior performance as compared to other competitive controllers in controlling the speed of HEVs.