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Road Veichles Dynamics

The Research Group on road vehicles deals with the modelling and experimental analysis of passenger cars, heavy vehicles, farm tractors and motorcycles exploring both mechanical and electronic aspects. Research links have been established with important automotive companies. The research is organised into five application topics.

Vehicle modelling and testing

Several numerical Multi-Body models were developed using both commercial codes and general purpose software for vehicle dynamic simulation, allowing the optimization of performance, handling and ride comfort as well as the design of new actively controlled subsystems. In particular, a 14 degrees-of-freedom real-time car model (including a race driver model) was developed for Hardware-In-the-Loop simulations and Rapid Control Prototyping. Moreover, a model of a heavy vehicle was developed to evaluate load spectra on axles, tyre wear and the effect of sloshing. Models of farm tractors were implemented considering the soil deformability. Innovative models of subsystems (braking system, hydraulic power steering system, power train, bushing, semi-active dampers) were also developed and integrated within vehicle models. All simulation models were validated through comparison with experimental data using the indoor and outdoor facilities of the Department. Among these, an instrumented vehicle (dynamometric hubs, braking pressure transducers, inertial gyroscopic platform, vehicle speed and sideslip angle optical sensor, dynamometric steering wheel and accelerometers) was set up for full scale tests, a Hardware-Inthe-Loop test bench was developed to investigate performance of ABS and ESP control units and ad hoc test benches were designed and built to analyse the behaviour of vehicle subsystems. For motorcycles, an innovative measuring system was set up to assess the relative movements between driver and bike.

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Tyre modelling and testing

Thanks to a long lasting cooperation with Pirelli Tyre, a 3D rigid ring tyre model was developed for both comfort and handling analyses also accounting for the contact patch dynamics. Several experimental indoor and outdoor tests were performed to validate it. In order to be able to correctly predict both passive and active vehicle performances, the tyre model was integrated into different vehicle models. A further development of the model is presently underway to be able to better predict F1 tyre behaviour. A deformable tyre model was implemented to be able to predict the dynamics of agricultural vehicles taking into account the tread pattern design and the soil deformation. Two projects (Cyber Wheel and Cyber Tyre in cooperation with Pirelli Tyre) were carried out with the aim of turning the tyre into a sensor to provide active control systems with additional information. Several algorithms were developed and patented to estimate contact forces, grip margin and hydroplaning risk.

Aerodynamics

The aerodynamics of several heavy vehicles (high sided lorry, tractor and semi-trailer combination, tanked truck) have been studied within the WEATHER EU Project (in collaboration with the Universities of Birmingham and Nottingham). The overturning risk associated with cross wind has been studied by means of numerical multibody - CFD coupled simulations as well as experimental tests performed in the wind tunnel of Politecnico di Milano where different atmospheric boundary layers and scenarios were reproduced.

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Active control systems

Actively controlled subsystems were designed and developed aimed at improving vehicle stability, performance and ride comfort: a semi-active differential (currently equipping F430) was developed in cooperation with Ferrari. A Brake Torque Vectoring control logic was designed to enhance vehicle performance; semi-active dampers were employed to improve ride comfort, while active camber control and suspensions with active kinematics were developed to enhance vehicle handling performance. Active suspensions were also applied to prevent rollover of heavy vehicles induced by cross wind and sloshing.

Hybrid / electric vehicles

Researchers have been involved and are presently working on several projects and activities with hybrid/ electric vehicles: optimisation of delivery management with electric commercial vehicles in Milan, hybridisation of a city car and of a commercial 3.5 ton van (from design to prototype), modelling and energy flow analysis in high performance hybrid cars and heavy duty operating machines and the study of full electric retrofit for Alfa Mito. In this research field different international patents were issued.


Contacts
Prof. Federico Cheli
e-mail: federico.cheli@polimi.it