Cascade Control Solution for Traction Motor for Hybrid Electric Vehicles

In this paper a hybrid electric vehicle is considered, which contains both aninternal combustion engine and an electric motor (EM). Without focusing on the othercomponents of the vehicle, the EM is treated in detail, both regarding modelling aspectsand control solutions.After a brief modelling of the plant, two cascade speed control solutions are presented: firsta classical PI+PI cascade control solution is presented. The control systems related totraction electric motors (used in vehicle traction) must be able to cope with differentrequests, such as variation of the reference signal, load disturbances which depend on thetransport conditions and parametric disturbances regarding changes in the total mass ofthe vehicle. For this purpose, in the design of the speed controller (external loop) a specificmethodology based on extension of the symmetrical optimum method is presented. Thecontrollers are developed using the Modulus–Optimum method for the inner loop, and theExtended Symmetrical Optimum Method, corrected based on the 2p-SO-method, for theouter loop (for a more efficient disturbance rejection).In order to force the behaviour of the system regarding the reference input, a correctionterm is introduced as a non-homogenous structured PI controller solution.Simulations were performed using numerical values taken from a real applicationconsisting in a hybrid vehicle prototype, showing satisfactory behaviour.