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

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Adaptive operator systems in tractors : analysis of potentials and methods for specification and evaluation
(2024) Schempp, Timo Thomas
Der Ackerschlepper wird in der Landwirtschaft, auf dem Bau, im Forst und im Kommunalbereich als Universalmaschine eingesetzt. Dazu wird er wechselnd mit einer Vielzahl von Maschinen gekoppelt, um diese zu betreiben. Es ergeben sich wechselnde Bedienszenarien mit unterschiedlichen Anforderungen an die Bedienung der gekoppelten Maschinen. Heutige Bediensysteme sind statisch und müssen daher als Kompromisslösung für diese unterschiedlichen Anforderungen an die Bedienung eingeordnet werden. Adaptive Bediensysteme können sich hingegen an wechselnde Bedienszenarien anpassen. Diese Arbeit beleuchtet den Stand der Technik der Bediensysteme in Ackerschleppern allgemein und explizit an drei ausgewählten Beispielen. Ferner werden zwei Methoden beschrieben, mit denen ein adaptives Bediensystem spezifiziert werden kann. Für die Bewertung der kognitiven und physischen Ergonomie von Bediensystemen allgemein werden zwei weitere Methoden vorgestellt. Alle Methoden sind für einen auf dem V-Modell basierenden Entwicklungsprozess geeignet. Die beschriebenen Ergebnisse einer theoretischen und praktischen Potentialanalyse motivieren den Einsatz adaptiver Bediensysteme im Ackerschlepper. Die theoretische Potentialanalyse stützt sich auf die Grundlagen der Ergonomie und auf die Art und Weise wie die Funktionen in einem Ackerschlepper genutzt werden. Die praktische Potentialanalyse stützt sich auf die Auswertung und Analyse von Messdaten aus dem Feld mit fast 500 Arbeitsstunden aus 14 Bedienszenarien. Ferner beschreibt diese Arbeit die Anwendung der Methoden zur Spezifikation, das entwickelte und funktionsfähige adaptive Bediensystem und die Anwendung der Bewertungsmethoden, die für das adaptive Bediensystem eine signifikante Verbesserungen der physischen und kognitiven Ergonomie zeigen.
Analyse der Maschinenkosten mittels automatisierter und manueller Maschinendokumentation im ackerbaulichen Produktionsprozess
(2023) Lattke, Justus; Böttinger, Stefan
“Smart Farming”, “Agriculture 4.0” and the “Internet of Things” are terms set to define the future of global agriculture. Many studies predict that these new technologies will have more impact on agricultural productivity than the “Green Revolution” of the 1970s. Upstream and downstream agricultural suppliers claim that their products and services will benefit farmers and their businesses. In this study, several farm management software programs were tested for their capacity to add value to the cropping division of a large and diversified farm. The evaluation showed that a farm management software program based on automatic collection of machinery cost data, gave more precise and timely information than a process relying on manual data collection. This conclusion was arrived at by calculating total cropping equipment costs over a full season using two cost accounting methods – an adaptable planned cost calculation and a process cost calculation – and comparing the results from the automatic and the manual collection of data. To determine the most suitable method and to select the various software programs to evaluate, various trade fairs and companies were visited, and websites searched. The most promising software programs were then tested for functionality and ease of use at the Horsch farm, “Agrovation”. It turned out difficult to establish an incentive system for employees to use the new technologies. For this reason, the farm machines at Agrargesellschaft Pfiffelbach were equipped with the 365FarmNet application without employee registration. The entire production period of crops harvested in 2018 was included. Both automatic and manual data collection took place from August 1, 2017 to December 31, 2018. To evaluate the quality of the two methods of data acquisition, the actual hours worked were compared with the hours recorded according to the type of cost collection.
Anforderungs- und einsatzgerechte Auslegung von Fahrantrieben mobiler Erntemaschinen
(2019) Häberle, Steffen
Fahrantriebe mobiler Erntemaschinen werden im Rahmen einer fortschreitenden Automatisierung zunehmend zum integralen Bestandteil der Prozessführung. Komplexe Anforderungen, die sich aus deren Einsatz ergeben, haben zu einer Etablierung hydrostatischer Fahrantriebe geführt. Der zunehmende legislative Druck und die steigenden Vermarktungschancen kraftstoffsparender Technologien rücken die Effizienzbewertung von Antriebssystemen stärker in den Fokus der Forschung und Entwicklung. Standardisierte Bewertungssysteme lassen sich bei mobilen Arbeitsmaschinen, wegen deren Heterogenität und Vielfältigkeit ihrer Aufgaben, allerdings nur schwer umsetzen. Die vorliegende Arbeit zeigt einen allgemeingültigen methodischen Ansatz zur Effizienzbewertung anhand von Lastkollektiven und eines Simulationsmodells auf. Dieser lässt sich auf alle mobilen Arbeitsmaschinen mit quasistationären Lastanteilen anwenden. Am Beispiel eines Mähdreschers werden typische Einsatzbedingungen mit gemessenen Einsatzprofilen und Lastkollektiven ermittelt und in den Gesamtkontext möglicher Nutzungsszenarien kategorisiert. Mittels eines Antriebsstrangmodells wird damit die Energieausnutzung des Fahrantriebs, entsprechend den Einsatzbedingungen, berechnet. Basierend auf diesen Ergebnissen und einer detaillierten Anforderungsanalyse sind neue Antriebslösungen erarbeitet und entsprechenden Leistungsklassen zugeordnet worden. Für einen Referenzmähdrescher wird ein methodisch ausgewähltes Fahrantriebskonzept, ein sogenannter Summierungsantrieb, ausgelegt und modellbasiert bewertet. Die berechneten Ergebnisse der optimierten Antriebsvariante zeigen deutliche Verbesserungen der Energieausnutzung bei einem erhöhten Kundennutzen.
Applikationstechnische Untersuchungen im Weinbau an Pflanzenschutzgeräten mit Einrichtungen zur Rückführung nicht angelagerter Spritzflüssigkeit
(1990) Kleinlagel, Bernd; Kutzbach, Heinz Dieter
Zur Verringerung der Umweltbelastung bei Pflanzenschutzmaßnahmen sind u.a. technische Weiterentwicklungen der Pflanzenschutzgeräte notwendig. Die erst seit kurzer Zeit im deutschen Weinbau anzutreffenden Pflanzenschutzgeräte mit Einrichtungen zur Rückführung nicht angelagerter Spritzflüssigkeit, kurz Recyclinggeräte genannt, versprechen neben einer deutlichen Reduzierung von Abdrift und Bodensedimentation der Pflanzenschutzmittel auch eine Verbesserung der Wirtschaftlichkeit durch Wiederverwendung der nicht zur Anlagerung gelangten Spritzflüssigkeit. Die unter Laborbedingungen durchgeführten Versuche zur Bestimmung der Auffangraten liefern grundlegende Daten zu den verschiedenen technischen Lösungen. Ziel der unter praxisüblichen Bedingungen durchgeführten Freilanduntersuchungen war es, aufzuzeigen, inwieweit diese neue Applikationstechnik Spritzmittelverluste mindert und dennoch eine qualitativ und quantitativ ausreichende Wirkstoffanlagerung auf den Rebblättern ermöglicht.
Dynamische Eigenschaften von Ackerschlepper-Triebradreifen bei höheren Rollgeschwindigkeiten
(1989) Schrogl, Horst; Kutzbach, Heinz Dieter
Da über das dynamische Verhalten rollender Ackerschlepperreifen bisher nur wenig bekannt war, war es das Ziel dieser Arbeit, die Einflüsse von Reifenabmessungen und -bauart, sowie der Betriebsbedingungen wie Rollgeschwindigkeit, Belastung und Reifeninnendruck zu ermitteln. Durch die umfangreichen Versuchsreihen mit einem neuen Flachbahnprüfstand konnten dabei zum großen Teil sehr eindeutige und neue Erkenntnisse gewonnen werden.
Einfluss der Hangneigung auf die Leistungsfähigkeit von Reinigungsanlagen im Mähdrescher
(2011) Fliege, Lars; Böttinger, Stefan
The performance of a combine harvester is determined by the maximum throughput at acceptable grain losses. At optimum throughput, the cleaning system reacts very sensitively to variations of the gradient, whereby the influence of lateral inclination is much higher than the influence of longitudinal inclination. The grain losses increase when the inclination of the cleaning unit is suboptimal. The performance of the combine harvester is then determined by the performance of the cleaning devices. Combine harvesters with hillside levelling systems solve that problem with their special chassis. Independent of the gradient these chassis hold the complete combine in a level position. Other hillside adapted cleaning systems are less effective and reach their limits already at medium gradients. The presented paper analyses the influence of gradients up to 15% on the performance of cleaning units with lateral hillside modulation. For this purpose several combines of equal type of construction have been analysed in different crops using large-scale parcel tests. The deployed measurement instrumentation corresponds to the series-production status of the combine harvesters. Various testing conditions and systematic errors make the handling of the collected data very complex. However, it enables the evaluation of the measurement characteristics of different sensors at variable gradient. The results, between the several test combines, indicate specific differences, caused by disparities in the level of development of the individual machines. Previous analyses of the influence of hillside are limited to throughputs of at most 4.8 kg/s per meter cleaning width. The tested combines achieved more than 9.4 kg/s per meter cleaning width in large-scale parcel tests. This result is a combine specific throughput of more than 55 t/h. The results display a possible triplication of cleaning losses in different throughput ranges between 15 t/h and 55 t/h already at a lateral inclination of 10%. The influence of longitudinal inclination is marginal. The analysis of overlaid lateral and longitudinal inclination demonstrates the significant influence of lateral inclination compared to longitudinal inclination.
Einfluss der mechanischen und pneumatischen Anregung auf die Entmischung und Abscheidung in der Mähdrescherreinigungsanlage
(2021) Beckmann, Konstantin
Due to the legal limitation of the maximum machine width the throughput increase is realized by further developing of the process technology. This requires precise knowledge of the ongoing processes. The aim of this work is the metrological investigation of the combine cleaning system according to the white-box model by analyzing the process sequence of the sub-processes.This enhances process understanding and enables the validation and verification of DEM-CFDsimulations. The evaluation of the segregation and separation process is based on the movement behavior of grain and straw. For this purpose, 2D high-speed x-ray images, static 3D reconstructions and 2D high-speed camera images are analyzed. The segregation in the lower layers is limited by the compression of the material layer due to its own weight. Due to the higher porosity the segregation of the grain near the wall is slightly faster. Additional relative movements of the material based on the superimposed conveying process. The resulting voids are used for a faster segregation. The influence decreases with increasing mechanical and pneumatic excitation in vertical direction. The influencing factors on the movement behavior of the material in the cleaning system is investigated with a test-rig. In the unloaded state the airflow decreases along the sieve. Due to higher sieve loads the airflow is flatter. Therefore the maximum air speed under the lower sieve is shifted to larger sieve lengths. The front area of the upper sieve is less loaded. The air passes by these areas and causes an increase of the air speed. High air speeds in the winnowing steps result in a high grain separation. A high component of the air velocity in the conveying direction between the sieves causes a shift of the separation on the lower sieve to longer lengths. The air throughput must be within the limits between a sufficient material fluidisation and a low conveying process on the sieves. In addition to identifying development potential, the results are used to verify DEM-CFDsimulations. There are deviations of movement behavior between grain and straw. Nevertheless,the influencing factors can also be examined qualitatively on the basis of the simulations.
Einfluss dynamischer Radlastschwankungen und Schräglaufwinkeländerungen auf die horizontale Kraftübertragung von Ackerschlepperreifen
(2006) Schlotter, Volkmar
Given the large variation of application conditions of tractors and agricultural machinery, the force transmission between tyre and ground is of particular importance for the efficiency in agricultural use. For a proper assessment of the tyre the exact knowledge of the tyre force behaviour in vertical, longitudinal and lateral direction is required as well as their inter-dependences. Besides the steady-state behaviour the dynamic behaviour of the force transmis-sion is of high relevance. This thesis centres on the investigation of the lateral-force behaviour which is highly important for cornering, for driving on slopes, and also for vehicle roll. The steady-state and transient behaviour of the lateral force has been investigated using the Single Wheel Tester of Hohenheim University. Comparative tests for the longitudinal force transmission have been carried out. The focus was the assessment of dynamic behaviour under the influence of transient parameters particularly on rigid surfaces. The investigations for the steady-state lateral-force transmission show higher lateral forces for wider tyres especially in case of small slip angles. Tyre load has a strong influence on the cornering stiffness. A large increase in tyre load can lead to doubling the cornering stiffness. For small slip angles the lateral force tends to a maximum or even declines with increasing tyre load, so that for the same lateral force larger slip angles are required. The test results with non-steady-state slip angle excitation reveal a time delay in the lateral-force generation. This behaviour can be described by a time constant. An increase of the tyre inflation pressure from 0.5 bar to 1.6 bar leads to a decrease of the time constant by more than one third. A hyper-bolic decrease of the time constant with increasing driving speed confirms a stroke-dependency and leads in consequence to the introduction of a relaxation length. The relaxa-tion length derived from the measurements shows an increase with reduced tyre inflation pressure and rising tyre load. The values for the relaxation length are in a range of approx. 0.5 m to 1.6 m. A strong dependence on the respective method of measurement was found this means that measured values should always be reported in connection with the employed measurement method. With longitudinal force measurements the longitudinal stiffness, analogous to the cornering stiffness, was determined. For the longitudinal stiffness of the traction force values nearly twice as high are determined compared to the longitudinal stiffness of the braking force. For both parameters a nearly linear increase with the tyre load was found. The comparison of lug-excited and surface-excited tyre load fluctuations indicates a dominant influence of the lug excitation and the radial run-out of the wheel compared to stochastic excitations on road surfaces. For stochastic excitations in form of a bump the tyre load fluc-tuations are strengthened. A different behaviour of the lateral force with positive and negative gradient of the tyre load can be seen. Therefore the mean lateral forces are decreased for stochastic excitations. With low frequency excitations of the tyre load up to 2 Hz realised with the Single Wheel Tester the mean lateral force decreases by up to around 6%. The transient response of the lateral force has been determined using sinusoidal excitation of the tyre load. The relaxation length of 0.40 m to 0.75 m for tyre load excitation is lower than the relaxation length for slip angle excitation. Here as well a decrease with increasing tyre inflation pressure can be observed. Comparison with the results for the longitudinal force transmission under the influence of tyre load fluctuations shows that the time constant of the traction force amounts to only approx. one third of the time constant of the lateral force: the traction-force transmission reacts faster to tyre-load fluctuations than the lateral force transmission. Simulation of stationary lateral forces with various models shows good accordance with the measured results. For interdependent longitudinal and lateral forces the Slip-Drift-Model with appropriate adaptation of the input parameters shows good results. For modelling the non-steady-state lateral force transmission the Maxwell model was used. The spring and damping parameters have been determined with the results of measurements. An increase of the lateral tyre stiffness due to increasing tyre inflation pressure or reduced tyre load can be seen. The damping constant is strongly reduced with increasing driving speed, whereas the tyre load and the tyre inflation pressure have only a slight influence. The lateral damping constant is considerably higher than the vertical damping constant.
Einfluss mechanischer und pneumatischer Parameter auf die Leistungsfähigkeit von Reinigungsanlagen im Mähdrescher
(2002) Zhao, Yuanguo; Kutzbach, Heinz Dieter
Ziel der vorliegenden Arbeit ist die Erarbeitung von Grundlagen für die Konstruktion von Mähdrescherreinigungsanlagen durch die Untersuchung der Wirkung der Fallstufen. Da die Wirkung der Fallstufen von der mechanischen Anregung durch das Schwingsieb sowie von der Luftströmung unter dem Sieb stark beeinflusst wird, werden sowohl die Wirkung der Luftströmung unter dem Sieb wie auch der Einfluss der mechanischen Parameter ohne Fallstufe untersucht. Bei Schwingsieben mit einer Fallstufe bzw. mit zwei Fallstufen werden die Einflüsse der Luftströmungen auf die Leistungsfähigkeit der Reinigungsanlage und die Wechselwirkungen ermittelt.
Einfluss verschiedener Parameter auf die Trenneigenschaften des Planetentrommelsortierers bei der Korn-Spreu-Trennung
(1989) González Oliva, Abel; Kutzbach, Heinz Dieter
Der erhöhte Kurzstrohanteil moderner Mähdrescher mit rotierenden Dresch- und Trennelementen und der Wunsch nach einer hangunabhängigen Reinigungsanlage macht die Entwicklung und Untersuchung neuer Separationsverfahren zur Korn-Spreu-Trennung notwendig. Als eine Alternative zu den konventionellen Flachsieb-Reinigungsanlagen wurde der Planetentrommelsortierer untersucht. Ziel dieser Arbeit war die Untersuchung des Arbeitsverhaltens und des Einflusses verschiedener Parameter auf die Trenneigenschaften dieses Verfahrens.
Einsatzmöglichkeiten elektrischer Antriebe für landwirtschaftliche Maschinenkombinationen
(2011) Hahn, Klaus; Böttinger, Stefan
Tractor-Implement-Systems are a vital component of agricultural mechanization. Their replacement by self propelled machines seems unlikely in the foreseeable future. At the same time, rising needs for food, high cost of energy, and a limited workforce require continuing increases in productivity. However, this should not have a negative impact on the environment. Technological progress is therefore of outstanding importance. Looking for trends in neighboring domains an increase in the utilization of electric drives can be observed. The research presented in this thesis shows that electric drives offer various benefits for agricultural tractors and implements ? the most important advantages being efficiency, controllability, and the possibility to distribute components. Yet, to fully utilize what electric drives have to offer it is necessary to pay close attention to system architecture as well as operator control concepts to make them work in the special environment of agricultural machinery. A concept was developed that is building on the ISOBUSidea of distributed control systems. For instance, the controller (i.e. the inverter) was placed on the tractor whereas the actuator (i.e. the motor) is on the implement. Given the frequent reconfiguration of the machines the inverter thus becomes a multi-purpose component. Easy, safe, comfortable, and profitable use is achieved by a high degree of standardization of the connector ? which includes automatic identification and configuration. Analytical models as well as prototype machinery of a fertilizer spreader, a sprayer, and a trailer with a propelled axle yielded a multitude of benefits. These include reduced fuel consumption for the spreader, less residual volume for the sprayer and better traction and vehicle dynamics for the propelled trailer. The good controllability of electric drives proved to be especially beneficial for those implements usually associated with precision farming: spreader and sprayer. Unproductive times for coupling and filling can be reduced. A propelled trailer helps to reduce soil compaction. The systems presented here are, however, in an early phase of development. The benefits of decoupling implement drivelines form the tractor?s engine speed could be proven. Due to their superior efficiency under partial loads electric drives are especially advantageous in applications that come with a wide range of loads. As far as complexity and ease of use are concerned, all three implements profited from the implementation of electric drives. In all cases safety and comfort of coupling the implement did increase. However, the systems are still limited both in functionality as well as level of automation. But given the good controllability, which is independent of most external influences, it is fair to assume that there is a high potential for improvements in this regard. When it comes to system control, a high degree of integration will be mandatory for the operator to fully utilize this increasing functionality. The required standardization is yet to be achieved. A mere substitution of a given drive by an electric drive is not always sensible. The use of electric drives necessitates a revision of rotational speed levels ? or more generally speaking ? of the working principle. It is vital to include the overload capability of electric drives into these considerations. The propelled trailer has a clear advantage in traction in the field whereas driving dynamics have a higher importance on the road. Whether it is a traction-assist or a drive that can be utilized over the entire speed range drives the power required and hence cost, weight, and space. In the end, this is an economical question but it may also be significantly influenced by legislation.
Energiebedarf von Traktoren und ausgewählten Anbaugeräten in der Außenwirtschaft landwirtschaftlicher Betriebe
(2024) Schwehn, Julian; Böttinger, Stefan
Vor dem Hintergrund des Klimawandels und hoher Ressourcenpreise ist der umsichtige Einsatz der zur Verfügung stehenden Energieträger von besonderer Bedeutung. Um die Folgen anthropogener Treibhausgasemissionen auf das Klima zu minimieren, sehen legislative Vorgaben in Europa und Deutschland ambitionierte Reduktionsziele für einzelne Sektoren wie die Landwirtschaft vor. Die heterogene Agrarstruktur erfordert standortgerechte Produktions und Arbeitsverfahren, was zu einer großen Vielfalt an eingesetzten Maschinen und Anbaugeräten führt. Neben der Untersuchung von Einsparpotentialen einzelner Fahrzeugkomponenten bieten landwirtschaftliche Verfahrensketten mögliche weitere Einsparungen. Die Erforschung dieser prozessualen Potentiale macht eine detaillierte Kenntnis der eingesetzten Maschinen und Anbaugeräte aus energetischer Sicht notwendig. Um die Einsparpotentiale innerhalb der Prozesse sowie der eingesetzten Technologien quantifizieren zu können, wird in der vorliegenden Arbeit der Energiebedarf von Traktoren und ausgewählten Anbaugeräten ermittelt. Dazu wird nach der Einführung einzelner Maschinen und Anbaugeräte eine Metastudie verschiedener Testverfahren und Literaturquellen durchgeführt, um die vorhandene Datenbasis zu bewerten und Datenlücken aufzuzeigen. Soweit es die Datenbasis zulässt, werden der aktuelle Stand und eine Entwicklung seit 1990 dargestellt, um die bereits erzielten Einsparungen aufzuzeigen. Darüber hinaus erfolgt ein Vergleich sowie eine Evaluierung bestehender Modellansätze zur Berechnung des Energiebedarfs einzelner Maschinen und Anbaugeräte. Aus der Kenntnis vorhandener Datenlücken sowie der Güte aktueller Parametersätze können systematische Feldversuche für weiterführende Arbeiten abgeleitet werden.
Entwicklung und Applikation eines instationären Reifenmodells zur Fahrdynamiksimulation von Ackerschleppern
(2009) Ferhadbegovic, Bojan
The driving speed of modern agricultural tractors increased continuously during the last years. Nowadays, a maximum driving speed of 50 km/h is standard for agricultural tractors in Germany. To be able to drive safely at such high speeds, the agricultural tractors are equipped with a suspended front axle. However, a rear axle suspension for standard tractors is still too expensive and has thus not prevailed yet. The increasing percentage of transportation duties and the efforts to increase the productivity generate a high demand for even faster agricultural tractors. Therefore, the first standard tractor with a maximum driving speed of 60 km/h was presented in 2005. This speed was achievable without a major change of the vehicle?s basic design. However, even higher driving speeds will require substantial modifications of the vehicle?s concept and are thus not expected very soon. Since the agricultural tractors are designed mainly for the field work, their driving dynamics characteristics on the road are not always perfect. The high vehicle masses, possible insufficiencies in the construction and interaction of various vehicle components together with the missing rear axle suspension can lead to critical behaviour of the vehicle, especially during high speed cornering. The entire suspension on the rear axle is accomplished by the tyres. Since the agricultural tyres are mainly designed for carrying high loads and generating high draft forces on soft soil, their driving dynamics properties on the road are rather insufficient. They usually have a radial run-out with an amplitude of 1-2 mm. Due to the rather low damping of the agricultural tyres, this rather small run-out can cause vibrations with a quite high amplitude, especially if the excitation is close to the eigenfrequency of the vehicle. Furthermore, the tyre inflation pressure varies between 0.8 and 2.0 bar - which is a relatively large span - making the vehicle setup more difficult. To analyse the driving dynamics of agricultural tractors and to identify possible problems and insufficiencies at an early stage of development simulation models are used. A very important part of a vehicle model is the tyre model. Being the link between the vehicle and the ground, the tyre has a high influence on the vehicle behaviour. It is therefore essential to use an accurate tyre model. Most of the commercially available tyre models today are optimized for passenger car tyres and are thus of limited use for soft and large agricultural tyres. In this doctoral thesis at the University of Hohenheim a dynamic model for agricultural tyres on rigid surfaces was developed ? the Hohenheim Tyre Model. It is a hybrid model since it needs physical parameters like spring and damper coefficients as well as empirically obtained data for the tyre-ground-characteristics. The Hohenheim Tyre Model uses the wheel speeds and the speed of the tyre tread to calculate the deflection velocity and the deflection of the tyre and subsequently uses both values as inputs for spring-damper-elements. The force calculated in these so-called Voigt-Kelvin-Elements is finally used to determine the slip and the slip angle of the wheel. The tyre model was created in MATLAB/Simulink and can be coupled to any multi-body-software. The model allows to calculate the transient tyre behaviour in three dimensions with a low computational effort, which makes it adequate for driving dynamics simulation. It takes the nonlinearities of the tyre into account and calculates the forces for pure longitudinal or lateral slip as well as for combined slip conditions.
Experimental investigations on tractor tire vibration properties
(2017) Brinkmann, Christian
Vehicle vibrations have raised articulate awareness in agricultural industry during the last years. Especially, the legal basis with the EU directive 2002/44/EC and its implementation into national law with the corresponding ordinance have sensitized the manufacturers concerning the vibration behaviour of their vehicles accompanied with an increasing demand for ride comfort by the customers. Furthermore, vehicle components’ stress due to vibration and shock is also significantly dependent on the tire’s vibration characteristics. Only an optimized design and combination of the vehicle components can reduce vibrations and improve ride comfort and endurance strength. In this thesis mechanical vibrations in the ride comfort frequency range between 10 Hz and 80 Hz are regarded. For the investigations a new mechanical shaker device has been developed and single frequency force excitations in the mentioned frequency range can be applied to a rolling tire. From excitation and response of the system it is possible to identify the vibration modes of the rolling tire. The shaker is designed to be applied both to a flat-belt test stand and a research tractor. Additionally, uniformity and cleat tests have been conducted with the research tractor in order to compare shaker, tire and impact excitations.
Experimenteller Beitrag zum Schräglauf- und Lenkmomentverhalten rollender Reifen landwirtschaftlicher Fahrzeuge auf starrer und nachgiebiger Fahrbahn
(1991) Heine, Adolf
Beim Einsatz landwirtschaftlicher Fahrzeuge können zwei Fahrzustände mit schrägrollenden Reifen unterschieden werden. Die Spurhaltung beim Fahren am Hang oder beim Pflügen erfolgt durch konstant (stationär) schräglaufende Reifen, wohingegen Lenkvorgänge zur Änderung der Fahrtrichtung als instationäre Fahrzustände anzusehen sind, weil sich der Reifenschräglauf hierbei ständig ändert. Um das instationäre Schräglaufverhalten der Reifen landwirtschaftlicher Fahrzeuge auf starren und nachgiebigen Fahrbahnen untersuchen zu können, wurde als Versuchseinrichtung ein Einachsanhänger mit stufenlos gegeneinander einlenkbaren Versuchsreifen und einer Fünf-Komponenten-Kraft- und Momentmessnabe entwickelt.
Förderung und Entmischung auf dem Vorbereitungsboden des Mähdreschers
(2013) Timofeev, Andrey; Böttinger, Stefan
In the last years with the increasing performance of the combine harvester capacity, the performance of the cleaning system has been the limiting factor, because the capacity of the threshing drum and the separation elements by the use of additional separation drums and rotors is not a problem anymore. The performance of the cleaning system can be greatly increased, especially through intense pre- segregation, whereas grain losses remain at a relatively low level even at high particle rates of approximately of m˙ K = 5,5 kg/(s·m). Grain- and NKB (chaff and other plant residue) -throughput affect both the conveying speed and the segregation on the grain pan. The grain throughput has a particularly strong impact on the conveyor speed, when throw occurs in the conveying process (Frv > 1). Thereby the elastic properties of the crop layer (straw and chaff rack) damps very strong the introduced mechanical agitation. This decreases the conveying speed strongly. The segregation in turn affects positively the speed of transfer from the grain pan to the material. The separation takes place substantially in the last third of the grain pan.
Grundlagenuntersuchungen am Mähdrescher-Vorbereitungsboden mit pneumatischer Unterstützung
(2017) Schwarz, Michael
Nowadays the cleaning unit in combines is often the power limiting assembly unit. There are no additional accelerating fields acting to segregate and separate grain besides gravitational acceleration. A strengthened pre separation of the material mixture acting in front of the winnowing step in the combine can increase the power of the cleaning unit without additional accelerating fields. A pneumatically supported separation process at the preparation floor is a promising measure. The target is to generate a fluidized bed. Conveying and segregation at the preparation floor are modeled following different approaches. The analytical description of the conveying at the pneumatically supported preparation floor by means of extended point mass approaches in conjunction with a stochastic description of the segregation is suitable for conventional modeling approaches for complex process engineering processes to a limited extent. For the experimental evaluation of the conveying and segregation a test rig with an additional fan at the preparation floor is developed. The test rig allows the determination of grain losses, cleanliness, return and separation characteristic in the cleaning unit. As typically handled in combines the feeding of the material is handled via the preparation floor and return pan. In order to be able to assign the grain losses to the point of delivery, the grains transported on the return pan are coloured. To evaluate the segregation at the preparation floor, the average height of the grain above the preparation floor is to be determined. This determination is done by means of a high-speed camera recording with subsequent particle tracking. The investigations at the preparation floor without pneumatically support show that the segregation at the preparation floor is restricted at high throughputs. Furthermore, it demonstrates that upon increasing throughput the proportion of the grains in the share of grain losses from the return pan increases disproportionally higher than the total grain losses. The design notes derived therefrom include the adaptation of the preparation floor length as well as the optimization of the return pan’s connectivity to the cleaning unit. By means of a pneumatic support arranged in the last third of the preparation floor, a fluidized bed is generated in the investigation, which increases the work efficiency of the cleaning unit by approximately 10%.
Influences on the performance of the stripper rotor in rice
(2002) Tado, Caesar Joventino M.; Kutzbach, Heinz Dieter
Rice is the most important food crop in many countries of Asia. In the Philippines, it is the staple food for more than 80% of the people while 70% of our population depend on rice farming and marketing for livelihood. However, despite the importance of rice in the lives of the Filipinos, production has not been able to consistently meet their needs. The ever-growing population continues to exert tremendous pressure on the rice farmers to produce more. The principle of stripping, that is, collecting the grains without harvesting the straw, presents a bright prospect in mechanical harvesting technology. A kinematic analysis of the stripper rotor during operation was made with a newly designed stripper test rig.
Kraftstoffverbrauch beim Einsatz von Ackerschleppern im besonderen Hinblick auf die CO2-Emissionen
(2006) Schreiber, Matthias; Kutzbach, Heinz Dieter
Agricultural tractors are currently almost exclusively driven by diesel engines. By rising fuel prices and growing ecological awareness concerning CO2-emissions and preservation of fossil fuel resources the importance of fuel consumption has been increasing. Generally, the substitution of diesel by alternative fuel based on vegetable oil is possible, however the potential for the substitution is limited by the scarcity of agricultural farmland and categorized as low. The cost savings are not very big due to higher fuel consumption with bio fuel. Therefore, only the reduction of fuel consumption for different agricultural operations and if applicable the reorganisation of the production chains can contribute to a sustained reduction of fuel consumption and costs. In this thesis the basic influencing factors on fuel consumption of tractors are shown. Field tests are only of limited usefulness for the examination of single influencing variables. For those studies a model had to be developed. The presented model is based on the status of science concerning engine and transmission performances as well as tractive performance for agricultural tractors and is combined with the ASAE-Standard 497.4-model for the tractive force needed to pull the implement. As existing tyre-soil-models are only of limited use to predict tractive performance in the field and to deliver these values to the tractor model, an independent traction prediction model was developed. It is based on empirical equations, which were parameterized on the basis of numerous field tests. Furthermore, the influence of the fuel consumption for turning over in the headlands and for transportation work were investigated and considered in the model. The new model was implemented into the software Matlab to determine fuel consumption for different agricultural work and defined parameter variations. The calculated values were compared to the results of field tests with a special equipped tractor at the University of Hohenheim to validate the model. The model was used to investigate the influence of numerous influencing parameters, the effect on fuel consumption was shown and optimization strategies were developed. The saving potential by the optimization of the working process is up to 30 % for different implements, depending on the current state. For this purpose the tractive efficiency must be maximized by the correct weight of the tractor and the correct tyres, tractor and implement must be adjusted ideal, four wheel drive and differential locks must be used if necessary and the transmission ratio must be chosen to run the engine close to the optimum working point with the optimum engine load. Besides the process optimisation it is important to deliver standard values for the fuel consumption for different working operations and production chains for the practical use. For the presented model a large number of parameters has to be determined, thus it is of limited use to calculate standard values. Furthermore, it is too accurate for those calculations. Therefore, the model was used to obtain simplified equations for a quick and simple calculation of fuel consumption values, considering the major criteria of engine, transmission and tractive performance of the tractor as the drawbar pull and the needed PTO-power of the implement. On the basis of these equations, implemented into Microsoft Excel, the required standard values for fuel consumption can be calculated for different tractors with implements of different size and defined soil conditions. However, the required data of some implements are not complete. For the most important agricultural implements these parameters were determined by measurements or collected from KTBL- or FAT-values. The results for different operations and production chains are correlating well with values measured in the field. The effect of the field size or the distance between field and the farm yard on fuel consumption can be shown as well. The saving potential by changing the whole production chain (like zero tillage) is enormous, however, there are horticultural and economical external effects. As those economical effects can hardly be estimated, the conversion of the production chain has to be reviewed for the individual case. In the future the importance of fuel consumption will increase. Different saving strategies will gain in importance in order to optimize agricultural operations with respect to fuel consumption. The approach of this thesis can be used to show saving potentials, to develop optimization strategies and to calculate values for the fuel consumption of different agricultural operations.
Load based evaluation of machines using the example of a tractor
(2018) Balbach, Florian; Böttinger, Stefan
The estimation of tractor value requires a lot of experience and knowledge and relies mainly on to-tal operation hours and manufacturing year. Today each tractor operation hour is considered to be equal because tractor meters operate time based only and do not consider the varying loads. But tractors face multiple applications within a year. Each application puts different loads on each tractor assembly such as engine, gearbox, axles or power take-off. A more precise method is introduced to evaluate tractor operation hours on basis of real applica-tion loads of each tractor assembly within the drivetrain separately. The method relates accumulat-ed tractor loads to standard operation loads which are defined by a reference load spectrum for the specific assembly. For the load evaluation a pseudo damage calculation similar to the Miner’s rule is used. A test tractor was equipped with strain gauge sensors to measure torque flow within the drivetrain. A variety of different tractor applications were measured and load spectra for different assemblies were generated. Based on different tractor application profiles lifetime load spectra for the differ-ent assemblies can be calculated. Further consolidation of the individual load factors can be done by weighting of the assemblies. The resulting load factor brings transparent information about in-tensity of tractor usage. Results show big differences between the assemblies and between the different application profiles. This supports the demand for a new method for tractor evaluation

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