Vehicle response on standardized tracks

Identi�cation of vehicle response is something which gets a lot of attention within the Technical Analyses department at DAF trucks N.V. This study was done to get more insight in truck-road interaction.. The motivation to investigate this speci�c interaction came from newly measured road data from Brazil. The road conditions in Brazil di�er a lot compared to the roads in Europe, these roads consist of a large variety of bumps and holes which have a large impact on the truck's lifespan. Measurements at DAF's proving ground in St Oedenrode already provided a large amount of data, but this data still lack the highest peaks as measured in Brazil. Therefore this study was used to map the truck's behaviour to arti�cial road pro�les and evaluate the virtual response in order to de�ne possible alternative road inputs. Before any road pro�le can be used, the road has to be enveloped. This basically means that sharp road irregularities will be �ltered and an e�ective road pro�le is created. This is related to tyre properties and independent of velocity. With the use of TricaT (Toolkit for Ride Comfort Analysis of Trucks), an internally developed toolbox by DAF, road input can be coupled to truck response. TricaT uses parameters such as velocity, tyre properties and road input to obtain the response of the truck. This can be displacements, acceleration, forces, springtravel and more. In order to limit the amount of output, only symmetric road input is used in this study. Cleats are used to map and identify the truck's response. By altering the height and length of the cleat from -100 to 100 mm and 0 to 1000 mm respectively, large differences in response are found. Some interesting height/length ratio's are used to map the specifi�cs of the response. These �rest analyses resulted in the conclusion that the overall shape of the response pro�files do not differ for alternating cleat heights, it only changed the absolute values. By changing the length of the cleat, a maximal output can be provoked when the combination of driving velocity and the length of the cleat (up and over time) matched the eigenfrequency of the axle. Knowing that it is possible to get a maximal output under the right circumstances, a sine sweep with speed bumps is used for further exploration. The ideal dimensions of the sine shaped speed bump were found to be 30 mm heigh and 350 mm long. These dimensions give the some of the best results after enveloping. A total of 61 speed bumps with a decreasing subsequent distance are used. The �rest bump to bump distance is 2525 mm, and this decreases with 40 mm after every bump. The sine sweep demonstrates the possibility of resonance. All of the components under investigation started to resonate when the combination of velocity and excitation frequency matched the eigenfrequency of the components. In the �final stage of this study, the previously found insights are coupled to the theory about mass spring damper systems. This was done to see whether resonance could actually cause problems in some of the components. It has been shown that the required amount of repetations to reach the maximal amplitude highly depends on the amount of damping acting on a component. This resulted in the conclusion that under real life road conditions, a poorly damped component, such as the fuel tank, will probably never reach the maximum response amplitude caused by resonance. However, it has been shown that the amplifi�cation factor can highly vary for poorly and minor damped systems. For damped components such as the axis, the cabin and the engine, resonance is something to take into account. They need much less cycles to reach the maximal excitation and therefore the possibility that a maximum is reached by resonance is a lot higher. This research has led to the identifi�cation of the truck's response for several road inputs. It has identifi�ed some of the most crucial road conditions and eventually it has been shown how resonance could affect different components. These insights can be used in further research on road simulation, and eventually data from real life road conditions can be coupled to virtual test conditions.