Integrated Chassis Control for Improving On-Center Handling Behavior 2014-01-0139

This paper proposes a new integrated chassis control (ICC) using a predictive model-based control (MPC) for optimal allocation of sub-chassis control systems where a predictive model has 6 Degree of Freedom (DoF) for rigid body dynamics. The 6 DoF predictive vehicle model consists of longitudinal, lateral, vertical, roll, pitch, and yaw motions while previous MPC research uses a 3 DoF maximally predictive model such as longitudinal, lateral and yaw motions. The sub-chassis control systems in this paper include four wheel individual braking torque control, four wheel individual driving torque control and four corner active suspension control. Intermediate control inputs for sub-chassis control systems are simplified as wheel slip ratio changes for driving and braking controls and vertical suspension force changes for an active suspension control. These control inputs are obtained by solving a quadratic optimization problem with constraints limiting vehicle motions and control inputs where a cost function represents tracking errors of vehicle target motions and control efficiency. Using simulation the control performance of the proposed ICC is evaluated in terms of on-center steering feel for a weave test where on-center steering feel is represented by lateral acceleration response to steering inputs. The proposed ICC shows the improvement of lateral response according to driver's intention, for example, driving torque control for acceleration, braking torque control for deceleration, or the combination of sub-chassis controls for aggressive driving.