Active Model-Based Suppression of Secondary Ride for Electric Vehicles With In-Wheel Motors

In vehicle motion control, the objective is to improve both dynamic performance and ride comfort through vibration analysis and compensation. Conventional drivetrains (combustion engines or on-board eletric motors) can only suppress primary modes (0.1-3 Hz) due to their limited torque response though the transmission shaft. In the case of electric vehicles with in-wheel motors (IWM), the shaft-less drivetrain enables besides primary also the active suppression of secondary ride modes (3-25 Hz). These compact and light-weight drivetrains have a higher unsprung mass, and therefore, require advanced suppression control methods that encompass both vibration regimes (0.1-25 Hz). The approach presented in this article aims to suppress the secondary ride in IWM vehicles through experimental model analysis and model-based control. In this study, the frequency characteristics of a Toyota IWM vehicle are experimentally analyzed on vibration test rigs, and subsequently, in multiple driving conditions. Based on the identified frequency responses, a model-based longitudinal acceleration control method is then analytically derived to suppress the vibration over a wide frequency band. The proposed technique is validated through experiments on Toyota's IWM prototype vehicles.