Vehicle Dynamic Simulation for efficiency improvement in Agricultural Tractors

The paper describes the activity performed within the frame of the research "Innovative solution for power saving in hydraulic circuits of agricultural tractors" Italian National Research Program (PRIN-2007). It aims at showing a new paradigm in the study of the agricultural machine energy saving solutions by means of an agricultural tractor global simulation model developed at IMAMOTER-C.N.R. A multi-body model of an agricultural tractor has been made. The transmission system, the handling and loading system, and the auxiliary actuation sub-systems have been modeled using a traditional specialized simulation program and then integrated in the tractor dynamic model. Two different transmission systems have been compared: the power split transmission and the full power shift transmission. For both of them, a study of the control problems related to the optimal management of the engine and the transmission has been performed. For the full power shift transmission the main objective was the optimization of the dynamic interaction between the hydraulic actuators and the multiple clutches control system to investigate the behavior of a standard mechanical two-shaft transmission. The integration of the detail models into the tractor dynamic model made a direct comparison possible, under a prescribed, yet flexible, mission profile. The model has been used to assist the global optimization of parameters, using as objective functions general indicators of the global machine productivity, rather than often misleading partial efficiency values. Thanks to this approach, it was possible to study the main hydraulic circuits of midpower agricultural tractors (90-150 kW), with the ability to tell those conceptual innovations and design developments needed to enhance their global efficiency and to increase a power saving on a larger scale.