Development of a novel mechatronic system for mechanical weed ...

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Introduction Inter-row weeding systems, their operating speeds and limitations were reviewed by Marfield and Bond (Marfield 2002; Bond et al. 2003). Weeding quality is highly dependant on equipment adjustment and on the row steering accuracy. Steering can be done manually, where experience and skills are expected from operator, or with sophisticated equipment e.g. computer vision guidance system or DGPS. Typical systems for inter-row weed control are toolbars pulled or pushed by a tractor. A tractor can simply be driven along the crop row carrying a toolbar with the weeding implement mounted at a constant horizontal spacing. The weeding tool as a part of the system can usually be adjusted to different inter-row distances and plant sizes. To achieve optimum weed reduction, the goal is to work as close to the plant as possible to minimise the non-hoed intra-row area. For most inter-row systems, the operator is just as important as the machinery. Without precise steering and appropriate adjustment, the equipment will damage the plant row and result in a crop loss. Generally, inter-row weeding system can be divided into non-powered and powered systems. The simplest non-powered systems are duckfoot-hoes with hoeing blades either rigidly mounted to the crossbar or mounted on a spring, forming a so called vibrating hoe. With an optimal hoeing depth of 1-2 cm, multiple hoeing tools can be placed side by side to accommodate larger row widths. Vibrating hoes usually cultivate the soil surface more deeply, uprooting a larger portion of the weeds. On that way they disturb the soil more and bring weed seeds to the surface, increasing the number of seeds which could germinate. The rigidly mounted type effectively cuts the weeds with less disturbance of the soil. Both types can be mounted on a parallelogram carriers providing accommodation of the hoeing blades to different soil contours. When a hoe is not sufficient in weed removal, powered equipment is an often- used option. A brush weeder consists of stiff bristles mounted to a rotating disk, which rotates with a high speed to uproot shallow weeds. The main advantage is very minimum disturbance of the soil since the brushes do not penetrate the ground. However, it is hard to adjust the brush width and the tractor’s speed needs to be kept below 4 km/h. Also, they are ineffective in hard soil and can 16
Introduction cause dust contamination on the plants. For harder soils, a rotary strip cultivator is an option. It works on the concept of rotating cutting blades which can cultivate very hard soils. Working depth can be 2-3 cm or more if the weeds are very thick or large, but depths over 4 cm can cause damage on the plant’s root system. Disadvantages are that the working width is very hard to change and the soil must not be too wet. One other powered cultivator option is a weed-fix. Unlike most powered cultivators that rotate on an axis parallel to the ground, a weed-fix’s rotating axis is perpendicular to the ground surface. A set of two or three rotating tines works the ground and uproots the weeds. It works especially well with hard soils because of the powerful fixed tines and allows a tractor speed of up to 8 km/h. There are other alternatives such as pneumatic systems but they are not used on a large scale because of very high operating costs. One of the main problems with inter-row weeding systems is steering. Weeding increases and decreases in effectiveness with every centimetre closer to, or further from the row. Because most weeding systems are rigidly mounted to a crossbar on the front of a tractor, driver skill is crucial. Even the slightest deviation in direction can cause a movement of 3-4 cm in the toolbar position, which added to the usual buffer space from the plant can result in a 6-8 cm width that is not weeded. Mounted on the front of the tractor, the toolbar can be easily seen by the driver, but is very sensitive to steering. If the toolbar is mounted directly below or behind the driver it is much less sensitive to small, immediate changes in steering but does not allow the driver to see the hoeing machinery, increasing error to sometimes 8 cm per side of the crop row. The displacement of the hoeing machinery’s centre of rotation can help to reduce this error, as can having the centre of rotation of each individual hoe directly behind the blade. This approach has been successfully applied on the Mutsaers QI steering system (see Figure 1.3). 17
Page 1 and 2: Institut für Landtechnik der Rhein
Page 3 and 4: Development of a novel mechatronic
Page 5 and 6: Kurzfassung Entwicklung eines neuar
Page 7 and 8: Acknowledgements Acknowledgements M
Page 9 and 10: Table of contents Table of contents
Page 11 and 12: Glossary of abbreviations and symbo
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Page 30 and 31: Introduction techniques. It is know
Page 32 and 33: Introduction Sowing and planting al
Page 36 and 37: Introduction 18 Figure 1.3 Inter-ro
Page 38 and 39: State of the art 20 Figure 2.1 a) F
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Page 48 and 49: Definition of the problem and resea
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Page 57 and 58: 4.1.2 Data acquisition 4.1.2.1 Hard
Page 59 and 60: 4.1.4 Test objects Materials and me
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Results and discussion Plant positi
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Results and discussion Plant positi
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Results and discussion 70 5.1.4 Dis
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Results and discussion 72 Figure 5.
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Results and discussion Connection b
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Results and discussion 76 5.2.1 Opt
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Results and discussion xmi1 = ( RLA
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Results and discussion With the inv
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Results and discussion 82 Horizonta
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Results and discussion 84 5.2.4 Sel
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Results and discussion 86 5.2.5 Dis
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Results and discussion Conventional
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Results and discussion Since the fi
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Results and discussion To avoid con
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Results and discussion As the size
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Results and discussion 96 5.3.4 Alg
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Results and discussion 98 V = zc( t
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Results and discussion corresponds
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Results and discussion 102 5.3.6 Me
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Results and discussion hoeing accur
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Results and discussion between the
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Results and discussion distance fro
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Results and discussion Distribution
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Results and discussion cuts are ran
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Results and discussion Forward spee
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Results and discussion x [mm] Distr
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Results and discussion The experime
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6 Summary Summary Neither a mechani
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Summary The third part of the work
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7 Conclusions Conclusions The prese
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8 References References Agrios, G.
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References in California's Sacramen
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References Johnson, W C and Mullini
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References Schans, D. v. d. et al.
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List of figures List of figures Fig
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List of figures Figure 5.24 Scheme
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Plant position 9 Appendix Table 9.1
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Plant position Table 9.3 Detection
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Personal data Education About the a
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