Wheel Clearance Testing in a Test Rig Simulation with Operational Chassis Displacement

Abstract: Volvo Cars proving ground in Hällered is a place for cars to be tested around the clock, in the most rough environments. Testing the wheel clearance today is done by putting modelling clay in the wheelhouse, and then drive through several different obstacles. By doing this, the wheel clearance can be measured where the wheel has left a mark on the modelling clay. The thesis is based on a question if wheel clearance testing can be performed on a test rig, and therefore the issue we decided to work with was what differences in the modelling clay marks could be observed between running the test on the proving ground and simulating the same movement on the test rig. We have made several limitations, the most obvious limit we have chosen is to only focus on the movement in vertical direction. We used a camera measuring system that was mounted onto our test vehicle. It measures the position from a set origin to the wheel centre in three dimensions over time. We ran tests out on the proving ground, focusing on one obstacle. The test was run for two reasons, to get the imprints from the tire on the clay and to obtain the measurement data from the measuring system. We then identified the maximum reached positive wheel position in vertical direction by using a MATLAB script. We then used the test rig to position the front wheels in the same three-dimensional positions as when the wheel centre reached its maximum vertical value according to the measuring data mentioned above. We measured the imprints of the wheel in the modelling clay after the positioning procedure in the test rig and began to compare the different clay imprints and evaluating the results. The measurements indicated a significant difference between the two, even though the positioning used in the three dimensions were identical. We discuss the possible reasons for any source of error that we could think of. We also come up with suggestions how to reduce the impact of some of the sources of error.