Physical Modelling and Automatic Configuration of CES Valve

This thesis has been performed at Öhlins Racing AB which is known world-wide for its high quality racing shock absorbers. Öhlins have been developing shock absorbers for more than 30 years and in addition to this they also develop a technology for semi-active suspension. Semi-active suspension technology makes it possible to achieve an intelligent and dynamic vehicle chassis control. Compared to standard passive suspensions, semiactive dampers allow improving vehicle cornering performance while still providing good comfort when cruising. This is achieved by a real time adjustment of the suspensions damping characteristics. Öhlins system for semi-active suspension is called CES (Continuously controlled Electronic Suspension). The systems consist of electronically controlled hydraulic valves for uniflow dampers. These valves are mounted on all four dampers of the vehicle and are controlled individually to provide the desired ride quality. The valves are configurable to suit many types of vehicles by changing internal parts. The first goal of this thesis project was to study the behaviour of the CES valve and uniflow damper. In order to achieve this a simulation model was created using Hopsan which is a 1-dimensional multi-domain modelling tool developed at the division of Fluid and Mechatronic Systems at Linköping University. The model considers mechanical forces from for example springs together with hydraulic forces. It was validated against static and dynamic measurements made in a flow bench and a dynamometer. The second goal was to use the simulation model as part of a tool that configures the CES valve according to a requirements specification. To achieve this goal a method of estimating the characteristics of the internal damper valves was developed. This estimation method, together with the simulation model, was used to choose the best valve configuration by using weighted least-squares. The result is presented in a Matlab-based graphical user interface