RICERCA ITALIANA     

Innovative solutions for power saving in hydraulic circuits of agricultural tractors

Università degli Studi di Modena e Reggio Emilia

Abstract

The Research Program deals with the analysis and the design of the main hydraulic circuits of mid-power agricultural tractors (90-150 kW), with the aim of determining those conceptual innovations and design developments needed to improve their global efficiency and to allow a large scale power saving. The hydraulic circuits taken into account in the research program are: the transmission system, the handling and loading system and the auxiliary actuations system.
The research activities, to be performed starting from the same point of origin and developed under a proper synergic collaboration, will lead to an integrated design enhancement of the reference agricultural tractor hydraulic architecture, characterized by stronger performances and higher global efficiency.
The study of the transmission system is divided into two parts: the first part involves the power split transmission; this part is focused on the study of a hydrostatic hybrid transmission system made by a combination of a hydrostatic unit and a planetary gear. The second part of the study involves the full power shift transmission; it deals with the optimisation of electro-hydraulically controlled multiple clutches.
The study of the handling and loading hydraulic circuit involves multiple linear actuators circuits. Some architectures of handling and loading systems will be defined, with particular attention to the analysis of the widely diffused load-sensing solutions; in particular, in >>>

Principal Investigator

Massimo Borghi Università degli Studi di MODENA e REGGIO EMILIA

Research Objectives

The research program is aimed at investigating different suitable solutions in order to improve the energy conversion efficiency of hydraulic systems equipping mid-power agricultural tractors (90-150 kW). Moreover, according to the general guidelines reported in the "Off-Highway Vehicle Technology Roadmap - U.S. Department of Energy" [www.trucks.doe.gov] which will condition the agricultural equipment technical development in the next decade, it is devoted to define possible strategies to obtain performances improvement and consumptions reduction through a generalized power systems efficiency increasing.
Medium size agricultural tractors (and other off-road machinery) considered in this research program are widely represented in the international market share. In particular, several of the most qualified agricultural tractors and associate components producers are located in Italy, hence the project presented is of significant relevance for Italy. The continuous technical and technological development, and the high quality standard level reached in the national industrial division, lead Italian hydraulic components production to hold the 13% of international production, being the 4th producer in the word. It becomes necessary that agricultural tractors and machinery manufacturers focus efforts in particular on the technological innovation of their products, especially as far as energy conversion efficiency in the hydraulic system devoted to movement >>>

First Results

Expected results from the project are diverse in kind, and must be considered in view of the complementary role played by all research units throughout the project timeline.
During the project, a significant number of individual partial, yet significant, results will be produced by all the research units, but it will only be at the end of the activity, when all contributes will be put together that the major contribution to the advances in the field of activity are expected.
The observation of present trends in simulation of fluid power systems show a significant highlight of control theory and detail investigation. Only few examples may be found, however, where the problem of how different subsystems may interact at the vehicle level is tackled. Also the problem of the definition of an adequate representation of the machine working cycle or mission profile, is today grossly underestimated.
The interaction with the i.c. engine on one end of the power train, and with the working tool on the other have never been considered together in an integrated simulation environment, and this aspect assumes even higher relevance when the objective is the integration of optimization processes performed on portions of the fluid power transmission system onboard machines.
The main result expected will be therefore a solid methodology, to assist the global evaluation of efficiency of a machine in broad sense, combined with, on the practical side, a simulation >>>

Timescale

24 months

National and international background

The great impulse given in last decades by the technological progress to all industrial fields allowed a strong design development and a relevant efficiency improvement of hydraulic applications for heavy duty machines, such agricultural and earthmoving vehicles. The great attention devoted to the environment, the need of limiting the internal combustion engines pollution and the increasing costs of fuels force the hydraulic designer to develop more efficient hydraulic actuation systems, in order to achieve an overall power saving without reducing the machineries performances. In this scenario must be located the design limitations coming from future standards for the control of the exhaust emissions in internal combustion engines, and in particular those imposed by the EPA-TIER IV, which will force manufacturers to reduce the energy consumption by improving the hydraulic circuits with the aim of reducing energy losses (see the cited "Off-Highway Vehicle Technology Roadmap - U.S. Department of Energy" [www.trucks.doe.gov]). Consequently, the main targets to be achieved by the mobile application designers are on one hand the operating performances optimization, with particular care devoted to the metering and the modulation of the hydraulic power addressed to the actuators; on the other hand, the increasing of the energy conversion efficiency related to the power transmission, in order to minimize both prime mover power requirement and power dissipations (limiting >>>