Ride behaviour analysis of an agricultural tractor during its road displacement. Relations with driver's comfort standards
1994
Deltenre, A.
Ride vibrations on agricultural tractors have an adverse effect on the health and comfort of drivers, especially during road operation. The experimental part of this study aims to quantify tractor vibrations and find the parameters that affect them both in level and frequency content. Although measured signals present a great variability, it may be noticed that vertical vibrations are highest, they are located in a low frequency range and influenced by travel speed, tyre profile and implement characteristics. The tyre lugs are found to be a large excitation source. An analytical criterion aimed at evaluating comfort is proposed. In the second part, tractor dynamic behaviour is simulated. The simplest approach assumes that the tractor can be represented by a plane model possibly including a mounted or pulled implement. Computed natural frequencies are located below 5 Hz. A more complex approach is based on a model composed of six differential equations governing the motion. Natural frequencies are closely related to experimental values. Furthermore, the frequency response function is computed in order to obtain tractor motion amplitudes. Finally, the response to particular inputs is evaluated. This technique shows the lack of comfort in the tractor tested and the pre-eminence of vertical vibrations.
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