Active drive control of electric vehicles using a modal state observer

The drivetrain of an electric vehicle is not a stiff but a compliant system. Hence, it can be excited to strong torsional oscillations, in particular by fast changes of the air-gap torque. Furthermore, wheelspin during an acceleration process is critical, because this can lead to unstable driveability. The active drive control presented in this paper allows to improve the overall performance of an electric vehicle. Thus, it effects an active damping of torsional oscillations in the drivetrain and a fast adaptation of the air-gap torque of the electrical drive in case of wheelspin. Since additional sensors shall be avoided, inner state variables of the electromechanical system are estimated by a state observer. For the specific application, an observer in a modal structure turns out to be an adequate solution which simplifies the adaptation process to different types of drivetrains. The performance of the drive control is demonstrated by measurement and simulation results.