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KUBOTA has been marketing M Series tractors to the world since 1955. As shown in Fig.1, this series consists of five models ranging from 33.6 to 59.7kW (45-80) PTO horsepower. The four configurations are equipped with either ROPS or ROPS cabin, and an optional 4-wheel drive for each model is available. In this series, we have pursued “excellent-stability, high-productivity superior-mobility, and good operator-comfort” with a renewed effort to remove the bulky image of tractors regarding mobility. The New M series tractors were developed to meet multi purpose requirements of the market place. In this paper, the author will introduce the technologies utilized to enhance the concepts of “excellent-stability, high-productivity, superior-mobility and good operator-comfort”. We pursued this course of development for the new generation M series tractors.

Recently most of the Japanese tractors (10 - 40kw) have been equipped with an electro-hydraulic system for automatic depth and tilt control for the rotary tiller. This is a typical implement for the Japanese rice farming. The improved performance was needed to deal in the following areas. 1. In the muddy and rough soil pan condition, the tillage depth has to be kept at the satisfactory level while the engine speed stays within the operating range. 2. An automatic depth control must apply to rough tillage without using the conventional depth sensor (i.e. rotary tiller rear cover angle sensor). To meet these requirements, an automatic depth and tilt control system was developed. The two control modes (called MC-AUTO and E-AUTO) for the automatic depth control were developed by combining the conventional control method plus a load control method based on the fuzzy control theory.

A dynamic simulation and analysis system for sophisicated electro-hydraulic circuits ( called “HYCAS” ) was developed by KUBOTA for performance estimation and parameter optimization. The structure consisting of six fundamental functions and simple interactive operation makes the system a more convenient and practical CAE tool for design engineers and researchers.