Evaluation of Different Methods to Compute Excitation Signals Based on Measured Targets in Agricultural Machines

Basis for a strength calculation of a mechanical system is the knowledge of the outer excitation. In the case of agricultural machines it is either not possible or financially not affordable to measure such variables directly at the wheels. Therefore, measureable output parameters are defined as targets and they are used to calculate the input variables in an inverse process. Trailed agricultural machines are characterized by nonlinearities like complex tires, bearing slackness or elasticity of hydraulic components. All these phenomena have to be included in a MBS (multi-body simulation) in order to describe the behaviour of the real system. As shown in this paper, the results of a test track can be reproduced with a model consisting of rigid and flexible bodies. The excitation signals can be calculated in different ways. A well known method and a new approach are evaluated. By using mathematical methods in combination with a virtual test rig, time and costs can be reduced compared to a real test rig. Another advantage is that inner variables can be calculated, which cannot be taken out from the physical system.