Feasibility study on the mechanical adjustment of the vibration behaviour of a powertrain test rig for validating longitudinal vehicle shuffle

Vehicle manufacturers use Hardware-in-the-loop (HiL) approaches to validate overall vehicle characteristics, including those dependent on the powertrain, at an early stage of vehicle development. A powertrain test rig is a typical example. In the specific setup, the vehicle engine and side shafts are mechanically coupled to the load machines of the test rig, eliminating the physical influence of the rims, tires and vehicle body. Adapting a specimen to the test rig changes some characteristics. This affects the specimen's vibration behaviour, making it more challenging to validate comfort-related characteristics. A particular example is longitudinal vehicle shuffle; the powertrain's first torsional natural frequency causes it. The natural frequencies of the real vehicle and device under test differ significantly, so a road-matching approach is not directly feasible. To account not only for tire-road contact but also for the missing vehicle mass, some scientific studies propose a purely model-based adjustment, without significant evidence. On the one hand, this has the advantage of flexible parameter adjustment, but on the other hand, the necessary computing technology and suitable parameterisation methods must be available. To investigate the extent to which the demand for a purely simulated adjustment is justified, this paper will consider a feasibility study that physically corrects for the missing vehicle influence. The method must determine the necessary target moment of inertia of real vehicles and the given one on the rig. This study presents a solution for reaching the target value. In addition, secondary constraints, such as manufacturing effort and costs, and safety aspects, must be considered. The approach should be flexible to accommodate variations in the most common vehicle and tire dimensions. Only by adapting the HiL to the target system, the actual vehicle, is it possible to perform road matching and thus validate driveability at an early stage in the development process.