Global chassis control using braking and suspension systems

In the current design practice several individual active control mechanisms are applied in road vehicles to solve different control tasks. As an example, the suspension system is the main tool to achieve comfort and road holding for a vehicle whilst the braking system is the main tool applied in emergency situations. Since there is a certain set of dynamical parameters influenced by both systems, due to the different control goals, the demands for a common set of dynamical parameters might be in conflict if the controllers of these systems are designed independently. This fact might cause a suboptimal actuation, especially in emergencies such as an imminent rollover. For example, the suspension system is usually designed to merely improve passenger comfort and road holding although its action could be used to improve safety. The aim of the global chassis design is to use the influence of the systems in an optimal way. The goal is to design a controller that uses active suspensions all the time to improve passenger comfort and road holding and it activates the braking system only when the vehicle comes close to rolling over. In extreme situations, such as imminent rollover, the safety requirement overwrites the passenger comfort demand by executing a functional reconfiguration of the control goals by generating a stabilizing moment to balance an overturning moment. This reconfiguration can be achieved by a sufficient balance between the performance requirements imposed on the suspension system. In the presentation an integration of the control of braking and suspension systems is proposed.