Coordinated and reconfigurable vehicle dynamics control
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This dissertation describes a coordinated and reconfigurable vehicle dynamics control system. With the continuous development of vehicle actuation/sensing technologies, coordinating all the available actuation resources to improve system performance and expand system operational envelope has become an active research topic that has received significant attention from both academia and industry. Given the complex nature of tire forces that are relied upon for inducing generalized forces for vehicle motion control, the main challenge is how to coordinate all the tire forces in a unified and optimal manner to achieve the overall control objectives even under adverse conditions. In this dissertation, a hierarchically-coordinated and reconfigurable vehicle dynamics control system is proposed. A higher-level robust nonlinear controller is designed to produce the generalized forces/moment for controlling vehicle planar motions. An innovative control allocation scheme is designed to distribute the generalized forces/moment to slip and slip angle of each tire with the considerations of vehicle dynamics and environmental variations. Individual tire slip and slip angles are selected as the control variables to resolve the inherent tire force nonlinear constraints which otherwise may make the system more complex and computationally expensive. A real-time adaptable, computationally efficient accelerated fixed-point method with improved convergence rate when actuation saturates is proposed to solve the amplitude and rate constrained quadratic programming (QP) control allocation problem. To track the desired allocated slip and slip angle of each tire and therefore the required tire longitudinal and lateral forces to fulfill the control objectives, a combined tire slip and slip angle tracking control system is developed to manipulate the driving/braking/steering actuation of each wheel independent to vehicle body states. The overall system is evaluated on a commercial full-vehicle model provided by CarSim® under various adverse driving conditions including scenarios where vehicle actuator failures occur. Compared with those of existing vehicle control systems, significantly expanded system operational envelop and greatly reduced driver efforts were observed.