Active vibration control for electric vehicle compliant drivetrains

The present work describes a novel controller based on perturbation observers for reducing the oscillations and improving the stability in the powertrain of a full electric vehicle with in-board motors. Compared with more classical approaches, the proposed strategy permits to damp the resonance in the transmission line and to control the reaction torque on the road. To do that, the controller combines state feedback with a tyre reaction tracking loop. The former is intended to damp the resonance frequency of the drivetrain using pole placement, and the latter avoids low frequency oscillations and assures the proper reaction on the road. The inner state feedback loop is applied to the subsystem motor-gearbox-halfshaft-wheel, which can be perfectly characterized, and it is not affected by the nonlinear time-varying response of the tyre. This last magnitude is estimated with a perturbation observer without requiring complex nonlinear representations, and the obtained value is compared with the reference driver command. The outer tracking loop compensates for the tracking error. The proposed controller is compared with a more traditional algorithm based on a tachometric feedback, and it has proved a good performance in dry and snowy road conditions, properly working in presence of actuations of the traction control system in low adherence situations.