Frequency and time domain characteristics of digital control of electric vehicle in-wheel drives

In-wheel electric drives are promising as actuators in active safety systems of electric and hybrid vehicles. This new function requires dedicated control algorithms, making it essential to deliver models that reflect better the wheel-torque control dynamics of electric drives. The timing of digital control events, whose importance is stressed in current research, still lacks an analytical description allowing for modeling its influence on control system dynamics. In this paper, authors investigate and compare approaches to the analog and discrete analytical modeling of torque control loop in digitally controlled electric drive. Five different analytical models of stator current torque component control are compared to judge their accuracy in representing drive control dynamics related to the timing of digital control events. The Bode characteristics and stepresponse characteristics of the analytical models are then compared with those of a reference model for three commonly used cases of motor discrete control schemes. Finally, the applicability of the presented models is discussed.