Prof. agr. Thomas Rademacher, Life Sciences and Engineering, Technical University in Bingen, Germany
The manufacturers of technologies for threshing crop harvesting have primarily submitted Agritechnica innovations for an award in the automation and IT applications area. In order to use combine harvesters at the economic and/or technical performance limit, further technical solutions for calibrating the loss sensor system will be presented The focus is also on combine harvester series that are manufactured even more consistently according to the modular principle than before, thereby enabling a broad portfolio of products to be offered. A completely new combine harvester design opens up new performance dimensions.
Continued trend towards belt cutting systems and detail solutions
Current general conditions are forcing farmers to grow crops from more southern regions in more diverse crop rotations. The designers of specialized companies of harvesting headers and combine harvester manufacturers are responding to this with adapted designs. Belt cutting systems are gaining an increasing market share, as they are equipped with flex cutter bars and also adapt to uneven ground with segmented frames at right angles to the direction of travel. This reduces pick-up losses, especially in large working widths and in cropped terrain. To exploit this advantage more intensively, additional feeler wheels are used to adapt to the ground in the direction of travel. The inclination of the belt cutting system is therefore automatically adjusted to the operating conditions during harvesting work.
While fewer and fewer large-growing line rapeseed varieties are being grown, the nature of rapeseed varies greatly depending on the seasonal weather, so pick-up losses can still occur. Designers counter this with detailed solutions such as guide and compression screws, as well as profiled cross-conveyor belts and belt guides in dense guide rails.
Detailed improvements to the cutting system are required when mowing near the ground surface. Similar to the sliding surface of an ear lifter above the ground, mower fingers are also bevelled on the underside in order to mow with as little blockage as possible and at higher harvesting speeds with an adapted cutting system inclination in the direction of travel. Special mowing fingers are even adjustable without a tip in two parts against the mowing blades to maximise the shear cut.
Trends in threshing and separation
New combine harvesters in the top performance classes with increased threshing performance were presented by several manufacturers at the last Agritechnica. A further increase in threshing performance requires extremely high design effort, because the construction volume limits the growth in size. Then the machine weight also increases, because a higher output of threshing and separating techniques naturally requires more engine power and therefore more robust drive trains. Top models with almost 800 hp engine power reach kerb weights of more than 20 tonnes without the harvesting attachment. Soil-protecting wide or double wheels and half-tracks are therefore a “must” for these machines. The trend towards larger threshing drum and axial rotor diameters continues. Small threshing drums with a diameter of less than 60 cm are increasingly being abandoned for more swallowing capacity. Even in combine harvesters with double axial rotors, their diameter is up to more than 60 cm. To achieve high threshing outputs, axial threshing and separator rotors are also extended.
A new development is an axial rotor combine with counter-rotating axial threshing and separating rotor. The crop stream is fed tangentially to the rotor, which divides it on both sides. This saves drive power because the crop need not be diverted into the axial crop flow through the auger-shaped intake area and appropriately shaped housing, as is the case with conventional axial rotor combines. The design allows an increase in technical threshing performance beyond known dimensions. This combine is extremely short and mounted transversely in a carrier vehicle that travels longitudinally during transport. The carrier vehicle is consistently designed for controlled traffic farming with a bed dimension of 12 metres. It is also consistently designed for alternative drive technologies and fully automatic operation. As a result, the overall concept can be rated as resource-saving.
Trends in information and control technologies
The information and control technologies for threshing crop harvesting are becoming increasingly complex. On the one hand, machine-based intelligence is being developed further in the form of control technologies. For the first time, these include an automatic chopping unit and an automatic chopped material spreader. In the automatic chopping units, the correct reel position and cutting table length are set in order to create as even a crop flow as possible in the cutting system, which then has a positive effect on threshing performance. A scanner records the geometry of the threshed crop in order to position the reel appropriately. The layer thickness sensor for the headway controller also detects irregularities in the crop flow. When the layer thickness of the crop stream is most uniform, the cutting table length is suitable.
The lateral distribution of the chopped material over the entire working width is now also measured directly by laser sensors. If the chopped material distribution does not correspond to the set value, the throwing speed of the distribution rotors on both sides is adjusted independently of each other until the chopped material is evenly distributed again.
The many approaches to measuring grain losses are commendable. Especially with large combines, calibration of the loss sensors is increasingly necessary to ensure that the automatic adjusters work according to the design. In addition, harvesting at the agronomically defined or technically or economically given performance limit is particularly important with these combines, as the actual grain losses of combines with large working widths are usually overestimated. And this reduces the economic efficiency of the combine.
In addition to the usual shuttering systems, image processing techniques have also been developed for simple grain loss determination. The loss grains lying on the ground are photographed, the image processing technology recognises the number of grains per unit area and the associated app calculates the amount of grain loss after entering the technical data of the combine harvester and the yield. In any case, this technique promises a higher accuracy than the usual blowing free and estimating of grain losses. Whether these digital methods for grain loss determination will establish themselves in the market depends on their measuring accuracy, especially in forage harvester operation. The scanned area, which is too small for precise measurement, can be compensated through multiple scanning. Digital methods for determining grain losses during combine threshing are user-friendly to a similar degree as those for determining the lateral distribution during fertiliser spreading and involve very little effort – their chances of implementation are therefore good.
Smartphone-based systems are also taking advantage of people’s changed information-gathering behaviour. If problems occur during combine operation or adjustment, the relevant information can be downloaded from the control terminal screen by scanning the QR code. This method, which is in principle not new, but user-friendly, is used to quickly obtain assistance from the manufacturer for the proper use of the combine.
Trends in straw chaff management
The use of large combines with working widths of more than 10 metres is often associated with design challenges in the construction of chopping and spreading techniques. Here, the so-called radial distributors have established themselves, however not worldwide, as the requirements for chopping and distributing vary greatly depending on the cultivation method and threshed crop.
In arid regions with high levels of herbicide-resistant weeds, grist mills are built onto combine harvesters to destroy the cleaning effluents and with them the weed seeds. Such seed destructors are basically hammer mills with a high drive power requirement, which were already presented at Agritechnica. New design approaches mainly focus on reduced power requirements and a compact construction that allows all combine functions to be retained, as well as the coupling of a cutting system wagon. Overseas, these techniques can destroy about 80 % of weed seeds.
Under Central European harvesting conditions, however, about 80% of the grass seeds (foxtail, wind stalk) have already dropped out by the time the threshed crop is harvested. In addition, higher straw masses are harvested with higher water contents, which means that weed seeds also persist in the straw. The natural conditions for a technology for mechanical weed seed destruction are therefore completely different from those overseas. This means that the efficiency of such a system with a drive power requirement of approx. 70 to 130 kW is insufficient.
Trends for all aspects of combine harvesters
With increasing outputs of combine harvesters, the setting optimisation and sensor technology adjustment play an ever more important role, as incorrect settings on large machines cause proportionately higher economic damage than on small machines. This is why manufacturers continue to develop their adjustment and other control technologies. In addition to threshing performance, the quality of work plays an increasingly important role. For example, in the dry years from 2018 to 2020, the focus was on grain cracking. Axial rotor combines with a system-related lower risk of grain cracking are promoted by the manufacturers’ marketing departments as being particularly superior to combines with tangential threshing units.
However, when assessing work qualities, it is not only the agricultural dealers’ deduction lists and their sample analysis techniques that need to be taken into account. The crop flows within a combine must also be evaluated objectively. The proportion of cracked grain contained in the grain losses is often completely overestimated. Not every app reflects exactly what happens in and around the combine. Further scientific findings will be taken into account here in the future. The fact is and remains: each threshing and separation system has specific advantages and disadvantages, and each manufacturer offer suitable equipment options and intelligent control technologies for the various markets. Otherwise, not all combine harvesters would be suitable for worldwide use and consequently marketable.
Summary: the manufacturers of technologies for threshing crop harvesting have submitted a large number of innovations in the threshing crop harvesting segment. The world-wide trend to belt cutting systems and techniques for the adaptation of harvesting headers to a broad range of conditions is continuing. The belt cutting systems of the manufacturers that market their products internationally are becoming increasingly Europeanised. As a result, the choice for farmers and contractors is increasing.
This also applies to combine harvester series, which are being manufactured more and more consistently according to the modular principle, and therefore allow a very large number of equipment options, i.e. offer a broad range of products. Despite the restriction of the construction volumes, the threshing outputs are on the rise. Control techniques, now also on harvesting headers, improve the uniformity of crop flow, thereby increasing harvesting performance. The exact lateral distribution of chopped straw is directly measured as an important building block in the crop production process and adapted to the external conditions.
A newly designed combine harvester in a carrier vehicle opens up a further step towards higher threshing performance while at the same time increasing energy efficiency. This overall concept, designed for future process technologies and alternative energies, which can be operated manually as well as autonomously, represents a paradigm shift in the entire area of agricultural process technology.
The innovations represent current and long-term trends with many innovations around the combine harvester – so things will continue to be exciting. The current market and price situation for the main threshing crops means that high revenues can still be expected, but the price situation for farm inputs and their availability will have a more intensive effect on the willingness of farmers and contractors to invest than the range of products offered by the equipment manufacturers.