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Results and discussion 96 5.3.4 Algorithm for the online control of the hoeing tool’s rotational speed The idea built into the algorithm for online control of the hoeing tool’s rotational speed is based on the theoretical approach presented in the previous chapter. Before the rotational speed unew can be calculated, it is necessary to know the relative distance between the hoeing tool and the plant which need to be hoed, the latest forward speed V, latest angular position of the hoeing tool and latest rotational speed uold. With assumption that the forward speed will not change on the next section of travelled distance equal to the average intra-row distance between plants d, the forward speed can be calculated using the following equitation: zc( tL) − zc( tL−1) V = t − t L L−1 (5.18) where zc(tL) is the absolute coordinate of the last detected plant’s centre position in direction of traveling, zc(tL-1) is the absolute coordinate of the last but one detected plant’s centre position and the tL and tL-1 are the time stamps when the detection unit was above the centre position of the last and last but one plant successively. Knowing the distance and the forward speed it is possible to estimate the time in which the hoeing tool will arrive to the position exactly above the plant centre position. T z ( t ) − z( t) − D V c L−1 sens−hoe = (5.19) where z(t) corresponds to the absolute position of the detection unit for plant detection. At that moment the angular position of the hoeing tool φrecent needs to be acquired. Because of non uniform distances between plants it can happen that one very fast rotating sequence can be followed by one very slow sequence or vice versa. It means that the system needs to accelerate or decelerate depending on the recent angular position of the hoeing tool. As the angular
Results and discussion position of the tool is acquired with an incremental encoder the most recent position of the system can be calculated as the reminder value after dividing the value acquired from encoder N with the number of pulses corresponding to one rotation RESsys. To make a decision of whether the hoeing tool needs to be accelerated or decelerated a simple rule was applied: in cases where the latest position is between 0° and 180°, the system needs to be decelerated and between 180° and 360° it needs to be accelerated as defined in Equation 5.20. ⎧ ⎛ N ⎞ R ⎛ sys N ⎞ ⎪rest ⎜ ⎟ for ≥ rest ⎜ ⎟ ≥ 0 ⎪ ⎜ RES ⎟ sys 2 ⎜ RES ⎟ ⎝ ⎠ ⎝ sys ⎠ ϕ recent = ⎨ (5.20) ⎪ ⎛ N ⎞ ⎛ N ⎞ RESsys ⎪rest ⎜ − R sys for Rsys > rest > ⎜ ⎟ ⎜ ⎟ RES ⎟ ⎜ sys RES ⎟ ⎩ ⎝ ⎠ ⎝ sys ⎠ 2 where rest is defined as: x / y = q * y + rest (5.21) The required rotation speed value ωnew can be estimated based on the recent angular position and the remaining time until the hoeing tool arrives to the position exactly above the next plant centre position, as follows: ωnew ϕ − ϕ T desired recent = (5.22) The required rotational speed need to be transformed into voltage and sent to the servo drive as an external control signal. If there is only a small difference between unew and uold it is better to leave the servo system in the steady state, achieved after the previous adjustment, than to change the input voltage and upset the system from the steady state. A size of the difference between unew and uold which will be considered as small can be defined in the VI and it depends on the size of the protected area, number of arms, number of cuts between successive plants and angular adjustment of the arms. The flow chart of the algorithm for the hoeing tool’s rotational speed control is illustrated in Figure 5.22. 97
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Institut für Landtechnik der Rhein
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Development of a novel mechatronic
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Kurzfassung Entwicklung eines neuar
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Acknowledgements Acknowledgements M
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Table of contents Table of contents
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Glossary of abbreviations and symbo
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Symbol Unit Description Mmmax Nm Ma
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Symbol Unit Description Glossary of
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ωold ωout rad s -2 Latest rotatio
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Introduction The most frequently us
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Introduction application that had p
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Introduction be to go from a system
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Introduction limited and environmen
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Introduction than 40 years before g
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Introduction techniques. It is know
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Introduction Sowing and planting al
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Introduction Inter-row weeding syst
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Introduction 18 Figure 1.3 Inter-ro
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State of the art 20 Figure 2.1 a) F
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State of the art cylinder rotates a
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State of the art 1998). This device
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State of the art 26 2.2 Detection o
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State of the art The fluorescence s
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Definition of the problem and resea
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4 Materials and methods 4.1 Detecti
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Materials and methods Figure 4.1 a)
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Materials and methods Figure 4.3 a)
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4.1.2 Data acquisition 4.1.2.1 Hard
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4.1.4 Test objects Materials and me
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Materials and methods become a poss
Page 63 and 64: Materials and methods environments
Page 65 and 66: Materials and methods dimensions ne
Page 67 and 68: Materials and methods (PFM). As the
Page 69 and 70: Materials and methods A command sig
Page 71 and 72: Materials and methods The drive con
Page 73: Materials and methods Another tool
Page 76 and 77: Results and discussion 58 Figure 5.
Page 82 and 83: Results and discussion objects. Acc
Page 84 and 85: Results and discussion Plant positi
Page 86 and 87: Results and discussion Plant positi
Page 88 and 89: Results and discussion 70 5.1.4 Dis
Page 92 and 93: Results and discussion Connection b
Page 94 and 95: Results and discussion 76 5.2.1 Opt
Page 96 and 97: Results and discussion xmi1 = ( RLA
Page 98 and 99: Results and discussion With the inv
Page 100 and 101: Results and discussion 82 Horizonta
Page 102 and 103: Results and discussion 84 5.2.4 Sel
Page 104 and 105: Results and discussion 86 5.2.5 Dis
Page 106 and 107: Results and discussion Conventional
Page 108 and 109: Results and discussion Since the fi
Page 110 and 111: Results and discussion To avoid con
Page 112 and 113: Results and discussion As the size
Page 116 and 117: Results and discussion 98 V = zc( t
Page 118 and 119: Results and discussion corresponds
Page 120 and 121: Results and discussion 102 5.3.6 Me
Page 122 and 123: Results and discussion hoeing accur
Page 124 and 125: Results and discussion between the
Page 126 and 127: Results and discussion distance fro
Page 128 and 129: Results and discussion Distribution
Page 130 and 131: Results and discussion cuts are ran
Page 132 and 133: Results and discussion Forward spee
Page 134 and 135: Results and discussion x [mm] Distr
Page 136 and 137: Results and discussion The experime
Page 139 and 140: 6 Summary Summary Neither a mechani
Page 141 and 142: Summary The third part of the work
Page 143 and 144: 7 Conclusions Conclusions The prese
Page 145 and 146: 8 References References Agrios, G.
Page 147 and 148: References in California's Sacramen
Page 149 and 150: References Johnson, W C and Mullini
Page 151 and 152: References Schans, D. v. d. et al.
Page 153 and 154: List of figures List of figures Fig
Page 155 and 156: List of figures Figure 5.24 Scheme
Page 157 and 158: Plant position 9 Appendix Table 9.1
Page 159 and 160: Plant position Table 9.3 Detection
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Plant position Table 9.9 Detection
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Plant position Table 9.11 Detection
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Personal data Education About the a
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