Integrated control of active vehicle chassis control systems

The principle of integrated vehicle dynamics is investigated in this thesis by proposing a new control scheme to coordinate active aerodynamics subsystems, active rear steering, and hydraulically interconnected suspension. A nonlinear vehicle model is utilized by employing VICarRealTime commercial software for this study, incorporating nonlinear tire model. This model consists of 14 degrees of freedom that include longitudinal, lateral and yaw motions of the vehicle and body roll, pitch and heave motions relative to the chassis about the roll, pitch and heave axis as well as the rotational dynamics of four wheels. The vehicle dynamics are analyzed for the entire handling region, and three distinct control objectives are defined, i.e., safety, performance, and comfort which correspond to yaw rate tracking, sideslip and roll motion bounding, respectively. In this thesis, different subsystems are developed in order to improve safety, performance, and comfort of the vehicle. Active Aerodynamics Control (AAC) subsystem is designed based on the response of vehicle in cornering maneuvers at high speeds. This control logic monitors the states of the vehicle to correct vehicle behavior by altering load distribution of the vehicle. Active Rear Steering (ARS) is utilized to track the yaw rate reference and bound the sideslip motion of the vehicle. Electronic Stability Control (ESC) is developed in order to increase the safety of the vehicle. Hydraulically Interconnected Suspension (HIS) is employed to reduce roll motion and lateral load transfer. Active Anti-Roll Bar (AARB) is designed to increase the comfort of the vehicle, reduce the lateral load transfer and enhance the safety and performance of the vehicle. Torque Vectoring system (TV) is used in high-performance vehicles in order to enhance traction and cornering ability. Active Suspension system (ASS) is employed to be able to change the longitudinal load distribution of the vehicle to overcome the understeer and oversteer situations in transient situations. The effectiveness of each standalone chassis control system is assessed for the different range of handling via various maneuvers. It is proved that each controller has a capability of improving vehicle handling in the certain range of handling where a passive vehicle cannot. After analyzing and investigation, four subsystems are selected in order to develop integrated vehicle chassis control system. In the first part, three controllers (ARS, TV and HIS) are integrated based on two methods: an optimal control and a fuzzy logic approach. These proposed integrated control systems are evaluated by comparing passive, each subsystem and combined control. The second part is related to the integration of four controllers (AAC, ARS, TV and HIS) based on a fuzzy logic approach. The results demonstrate that the proposed integrated scheme can optimize the overall vehicle performance by minimizing the objective conflicts of the subsystems and increasing the functionalities of individual subsystems.