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Forschungsbericht Agrartechnik des Fachausschusses Forschung und Lehre der Max-Eyth-Gesellschaft Agrartechnik im VDI (VDI-MEG)

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Browsing Forschungsbericht Agrartechnik des Fachausschusses Forschung und Lehre der Max-Eyth-Gesellschaft Agrartechnik im VDI (VDI-MEG) by Subject "Automatic steering"

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    Untersuchungen zur automatischen Erntemaschinenführung mit Satellitennavigation und Leitlinienplanung
    (2006) Stoll, Albert
    The working devices of agricultural machines have been optimised continuously in the last decades. Additionally, the size of the machines, the working width and the installed power have been increased. The common combination of a tractor and a mounted, exchangeable implement is often replaced by specialized, self-propelled machines for one definite operation. Especially for harvesters this development can be noticed. The operation of a harvester requires a high concentration of the driver. He has to operate and monitor the complex and numerous working devices. Depending on the harvester the crop has to be transferred continuously or with interrupts to a transport vehicle. Working widths of harvester headers can reach to 9 m in Germany. In other countries they can be even exceeded. The working edge of these wide headers can be surveyed badly. Therefore, it is difficult to guide the machine in that way that the whole working width is used. Furthermore, the driver has to adjust the driving speed according to the local harvesting conditions. Regarding the harvesting process the driver has to choose an efficient course inside the field and at the headland. Bad sight conditions caused by back light, dust or darkness as well as time pressure caused by weather conditions and ripeness of the crop make the drivers tasks even more difficult. If suitable control systems steer the machine and adjust the driving speed automatically, the driver can concentrate on the main functions of the harvester. Therefore, the throughput and the working quality can be increased. The aim of this thesis is to develop the basic theory for an automatic guidance for harvesters which has to be investigated with a self-propelled forage harvester in practice. It was demanded that the positioning data which are necessary for the automatic guidance are provided by receivers for the differential Global Positioning System. They have an accuracy of a few centimetres. No other navigation sensors should be used. The developed guidance system is structured in the closed loop transversal and the closed loop longitudinal control system. The lateral control reduces the lateral offset to the guidance path and the longitudinal control keeps the throughput constant in the field with varying yields. The control plan is defined by the guidance path which describes the desired driving route and the speed of the harvester. Path planning methods have been developed and investigated for different harvest operations. Path planning methods for swath harvesting and field covering operations are presented. The driving course of the swather is recorded during operation. With these data the guidance path for the forage harvester is calculated. The path allows a harvest operation in forward motion in every case, in order to avoid problems between harvester and transport vehicles at the headland. In order to plan the guidance path for a field covering harvest operation, the field is first structured into a headland and a main operation area. The headland provides the turning area. Also neighbour areas are considered which can be passed. Therefore, soil damaging turning manoeuvres can be carried out outside the field. The main operation area is divided into further areas, so that the guidance path has as many straight parts as possible. The number of turns can be reduced in this manner. The simulation of the path planning process and an automatically guided harvester shows that 20% of the turning distance and 10% of the total distance can be saved in comparison to a manually guided harvester without path planning.