Coordinated Control of Trajectory Tracking and Yaw Stability of Four-Wheel-Independent-Drive Autonomous Electric Vehicles

Abstract:

To investigate the multi-objective control problem of trajectory tracking and vehicle stability， a hierarchical coordinated control strategy of trajectory tracking and yaw stability was proposed for four-wheel-independent-drive autonomous electric vehicles. In the upper controller， the linear-time-varying model predictive control （LTV MPC） was employed to generate the desired front road wheel steering angle and yaw moment， and the PID speed control embedded in the model predictive optimization solutions was introduced to generate the desired total driving/braking torque. In the lower controller， the generalized forces from the upper layer were allocated to the four wheels based on quadratic programming. An 8-degree-of-freedom （DOF） vehicle model was used as the prediction model and a high-fidelity 14-DOF vehicle model with longitudinal and lateral combined brush tire model was used as the plant. Numerical simulation results under different speeds， road adhesion coefficients and conditions of whether to consider yaw stability control， demonstrate that the proposed controller possesses good trajectory tracking performance and robustness， which improves the tracking accuracy while ensuring the yaw stability under the limit condition.

Key words:four-wheel-independent-drive electric vehicles;trajectory tracking;yaw stability;model predictive control;control allocation