Experimental analysis and modelling of a suspension test bench

A suspension test bench is used to simulate the behaviour of a real front double-wishbone suspension tested under shaking. Different proofs were done by modifying some parameters, like mounting position, steer angle, and spring position so that it was possible to understand what the reaction of the suspension was. In detail, what was analysed is: wheel travel in longitudinal and lateral direction, camber, caster, and steer angle variation as a consequence of wheel centre movement in vertical direction. Suspension shaking is simulated by means of a pantograph jack manually managed. The acquisition and analysis of the data were made by means of the software “poliTO suspension test bench” implemented on Matlab, released with the test bench. It is a code that, through the functions “fcn_posizione_centro_ruota” and “fcn_sterzo” can give as output the quantities mentioned above, both in function of time and wheel centre displacement. The obtained results were then post-processed, analysed and compared one each other but also with the theoretical ones, obtained by means of Adams Car. The latest is a multibody environment which enables the simulation of bodies in a dynamic field, with the possibility to act in different parameters and to reproduce various types of inputs. The outputs are available both as plots and numerical data, which were later postprocessed on Matlab. You can also review the animation, which allows to have clearer ideas about the behaviour of the suspension. To do the tests, as a first step, the parameters to be varied between the various proofs were decided, choosing those deemed most relevant. Once we realise this, the series of tests were carried out and the results were postprocessed and analysed. Next step was to reproduce the geometry of the double-wishbone suspension in Adams Car, by creating a model as much similar as possible, to make numerical results comparable with the experimental ones. This step required the accurate measurement of the various geometries, taken manually on the test bench and confirmed by the 3D CAD model, released together with the test bench. All these measures were taken with the wheel centre in a central position, which is the position it assumes in the 3D CAD, and which was chosen as the reference position for the construction of the model. Adam’s suspension assembly has some components which are not physically present on the test bench, since they are substituted by potentiometers. Because of that, these components coordinates were chosen with criteria, by reproducing a situation as likely as possible. Once the model was ready, several tests were made, varying some inputs, and keeping track of them to understand how they affect the outputs. What was modified is the geometry of the upper control arm, according to different mounting positions. Also, an analogy between the original suspension and the modified one was done. The purpose was to highlight the differences in the behaviour between a generical double wishbone suspension and the one analysed in this thesis work. In the following step, a comparison was made between the results obtained on the test bench and on the software, to understand how much reliable the test bench is. Once the reliability of model was confirmed on some fronts, other tests, which could not be conducted on the test bench, were carried out exclusively on Adams Car. These tests were finalized on finding the best inclination of the steering tie-rod for havi