Modelling and simulation of an hydraulic interconnected suspension: analysis of vertical and roll characteristic

In literature there are several options for active and semi-active suspensions able to perform height adjustment and damping characteristic control, but very few examples of suspension systems capable of performing the mentioned functions and controlling the car's roll behaviour. One possible alternative is represented by a system that replaces the canonical anti-roll bar, using an interconnected hydraulic circuit. The whole system is composed of an active suspension able to lift the car's body and a hydraulic interconnected circuit which replaces the shock absorber and can change the damping characteristic controlling the internal active valves. The main object of this project is to study and understand the vertical and rolling behaviour of the car, starting from the company request in terms of vertical and rolling stiffness and to analyze the damping characteristics of the car, by designing and optimizing the hydraulic circuit of the suspension system. In order to achieve these results, a new model of the suspension scheme, using a Simulink toolbox called Multibody to model the mechanical part and the Simscape library to recreate the hydraulic circuit. Once the physical model was created, it was possible to study the kinematic characteristic of the scheme and its role in the system's dynamic behaviour. Eventually, several and different tests were performed to analyze the stiffness and damping characteristics of the suspension. The results showed a good response in the vertical and lateral direction, proving that the system discussed fulfils the vertical stiffness request given by the company and, in addition, provides good results in terms of rolling behaviour. Same considerations can be made for the damping characteristic, which showed decent results in vertical analysis while, though it seemed to be less performing, in the roll behaviour. According to the analysis results, future studies can be carried out to optimize and improve the car's dynamic behaviour, starting by choosing different hydraulic components or varying the suspension scheme.