A Hierarchical Control of Independently Driven Electric Vehicles Considering Handling Stability and Energy Conservation

Independently driven electric vehicles (IDEVs) with typical redundancy characteristics provide more potential to improve global performance. However, the model uncertainties would cause extra energy consumption and even destroy vehicle safety. This study presents a hierarchical control scheme to simultaneously guarantee the vehicle energy conservation and handling stability. In the upper layer, the tire nonlinear characteristics are reconstructed by the polytopic method to facilitate the controller design. Then a robust controller is developed to address the model uncertainties and ensure the vehicle handling stability by integrating the direct yaw moment control (DYC) system and the active front wheel steering (AFS) system. Furthermore, the stability performance of independently driven electric vehicles is analyzed and quantified with different regions in the tire slip angles phase plane. Considering the uncertain longitudinal velocity, the lower layer utilizes a linear time-varying model predictive controller (LTV-MPC) to develop the torque allocation strategy and realize energy conservation. The control authority for stability performance and energy conservation is dynamically adjusted by assessing the vehicle safety state. Hardware-in-the loop (HIL) tests are carried out to verify the effectiveness. The test results demonstrate the proposed method is feasible to balance different control objectives.