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

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State of the art 20 Figure 2.1 a) Finger weeder (1 - hoeing head with 14 rigid fingers made from plastic, 2 - mounting arms allowing the adjustment of approaching angles) (Anonymous 3 2007) b) Torsion weeder (1 - spring tines mounted to not overlap each other, providing low disturbance, 2 - springs allow flexibility of the tines (Ascard 2007) A torsion weeder is another alternative that reaches very close to the crop. Two spring mounted tines drag along the ground parallel to the plant row, and on their ends have a bent section that is angled toward the plant (see Figure 2.1 b). At low tractor speeds, they overlap and are pushed apart by the plant as it passes. As long as weeds are small, they will not survive the tines. At greater speeds, the tines spread apart as they penetrate the soil, cultivating the ground more but removing fewer weeds. The main disadvantage of passive systems is that they are only suitable in a situation when the crop is robust enough to withstand damage (e.g. from the 4 th – 6 th true leaf stage of sugar beets) and the weeds must be relatively weak. Timing is the most important factor when these implements are used. Unfortunately determining the exact time and being able to weed on the field is not always possible, because of changeable weather conditions. If the weeding is done late, weeds are stronger and they could withstand tillage. Both methods are effective only with small weeds, so the weeding operation which is delayed has usually a decreased impact on weeds.
2.1.2 Active tools for intra-row weed control State of the art There are no commercially available powered intra-row weeders, but several prototypes have been developed over the past 15 years. One was developed in the late 1990’s at Halmstadt University, Sweden. It is an autonomous robot with a vision-guided plant recognition system developed for sugar beet plants. Standing on four wheels, it is driven by two DC-servo motors on the two rear wheels and uses a rotating hoeing tool (1) which is lowered to weed and raised to pass over plant by use of hydraulic cylinder (see Figure 2.2). The vision system uses up to 19 plant characteristics to differentiate plants and weeds. The concept and a prototype of this system are shown in Figure 2.2. Figure 2.2 Concept and prototype of the intra-row hoeing developed at Halmstadt University (1 - weeding tool, 2 - colour camera for plant identification, 3 - computer) (Åstrand B. 2002) In Denmark, a hoeing system based on geo-referenced plant maps has been developed using the Osnabrück hoe (Griepentrog 2005). During the planting a location of every seed is recorded and this data are used for development of a geo-referenced seed map. The same map is a background for the control of the hoeing tool during the weeding process. This hoeing system uses two RTK- GPS receivers and a tilt sensor for exact orientation during the weeding. The Osnabrück hoe is a cycloid hoe consisting of a rotating cylinder on a vertical axis. Eight tines extend down vertically from the cylinder and are used to work the ground (see Figure 2.3). While the tractor moves forward, the 21
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
Page 13 and 14: Symbol Unit Description Mmmax Nm Ma
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Page 20 and 21: Introduction The most frequently us
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Page 24 and 25: Introduction be to go from a system
Page 26 and 27: Introduction limited and environmen
Page 28 and 29: Introduction than 40 years before g
Page 30 and 31: Introduction techniques. It is know
Page 32 and 33: Introduction Sowing and planting al
Page 34 and 35: Introduction Inter-row weeding syst
Page 36 and 37: Introduction 18 Figure 1.3 Inter-ro
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Page 48 and 49: Definition of the problem and resea
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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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