Modeling of a World Rally Championship Car Damper and Experimental Testing of Its Components

Sammanfattning: Rally cars are driven on many different types of surfaces. Each type of surface demands a special type of damper setup. In order to achieve optimum performance on the snow covered and icy Swedish roads, the gravel of the Spanish rallies and the smooth tarmac of the German rallies, a large flexibility in the possible damper settings is required. Prodrive, a British motorsport group, has been racing two Mini Countryman as factory team cars for BMW Mini as of Rally D’Italia in Sardinia in May 2011 and has requested that Öhlins Racing AB equips these cars with dampers. Öhlins Racing AB has been developing a damper for rally applications called the TPX. This damper is equipped with an Active Rebound Control system (ARC). The ARC allows for high levels of grip to be achieved together with good chassis control. The TPX damper with its ARC system is quite complex in structure. As there are many parts in the damper which can be altered, optimizing the damper would require a very large number of tests. A physical model of the TPX damper with its ARC system would reduce the time spent in the lab and help speed up the development of the damper. Prodrive would also like to a have a model of the damper that they can use in their model of the entire car which they use to setup the cars for races and to develop the car. The goal of this Master’s Thesis was therefore to create a model based in MatLab Simulink that qualitatively but not necessarily quantitatively replicated the dampers behavioral trends. Components which are very difficult to model, such as shim stacks, needed not be modeled. Their characteristics could be measured in the lab. During this Master’s Thesis project a model for the TPX damper was created using Simulink to model most of the physical parts of the damper. The rest of the model including its inputs and control were taken care of by a GUI. The model functions so simulations can be performed. Plotting the results of the simulations together with data from experimental tests was also made easy by the GUI. The results from comparisons between the simulated damper and the real object indicate that refinements need to be made to the model before it can be put to use as a tool for helping in optimizing the TPX damper’s construction. Hysteresis in the form of friction as well as damper flexibility does not seem to be negligible. The variation of the oil’s compressibility and the dynamic behavior of the check valves also need to be looked into. The graphs from the simulations seem to replicate the real dampers performance trends as intended. The numerical magnitudes of the data produced by the simulation are however not accurate. Overall the model produced during this master’s thesis seems to be a good step forward on the path to producing a useful model. Some suggestions for the next steps in improving the model are provided.