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

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Materials and methods change its input to the motor to cause the desired motion. If the servo motor in speed-control mode is trying to achieve a speed of 1000 rpm but is only running at 900 rpm, the feedback control will detect the problem and inform the positioning controller to provide more power until the detected speed reaches 1000 rpm (Baldor Electric company 2007). Closed loop systems are required for applications whose motion profile is complex, when high resolution and accuracy are necessary, when the rotation speed ranges from very slow to very high and when high torques are demanded in small package sizes. The actual feedback device is the last important part of a servo device. Feedback devices included analog and digital tachometers and resolvers. An analog tachometer is essentially a small generator, usually hard-wired to the output shaft of the motor and using the resulting rotational speed to output a variable voltage which varies linearly with speed. While they are cheap and simple, analog tachometers always introduce some AC-type ripple into the output signal because they are not ideal devices and subject to design and manufacturing tolerances. Digital tachometers operate either optically with photoelectric detection or with contact through a brush assembly. Two types exist: absolute encoders which assign a discrete address to each position through 360° and incremental encoders which simply emit electrical pulses at defined intervals which must then be counted to obtain position and distance (Baldor Electric company 2007). A concept of a servo system is illustrated in the Figure 4.5. 50 External controller + Servo amplifier Servo motor Feedback loop Encoder Figure 4.5 Concept of a servo system in a closed loop Controlled system (load)
Materials and methods A command signal created by the software or issued from the user interface enters as a low level power signal into the servo drive. In the servo drive, this signal is compared with the feedback value from the encoder to calculate the reference signal. The reference signal needs to be multiplied with the loop gain to generate appropriately amplified outgoing signal for motor control; higher voltage level for higher speed and higher current level for higher torque value. 4.3.1.2 Power transmission All the motors appropriate for the intra-row weeding system including the selected one, run at speeds higher than is required. To reduce the speed and increase the torque the output shaft of the motor was attached to a transmission. The rotational speed of the hoeing tool is G times slower than the input speed of the servo motor shaft. If the input shaft to an ideal gearbox is turning with a speed ωin and torque Min, then the output turns with a speed ωout and torque Mout can be calculated as M = G * M and (4.2) out in ω in ω out = (4.3) G where G is the gear ratio, and usually G > 1. In case of ideal gearbox output power Pout stays equal to input power Pin ωin Pout = Mout * ωout = G * Min * = Min * ωin = Pin (4.4) G Due to the power lost caused by friction between moving parts of the gearbox efficiency of the transmission can not reach 100%. Gearboxes have an associated coefficient of efficiency η < 1, and the output power is smaller than the input power 51
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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
Page 17: ωold ωout rad s -2 Latest rotatio
Page 20 and 21: Introduction The most frequently us
Page 22 and 23: Introduction application that had p
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
Page 38 and 39: State of the art 20 Figure 2.1 a) F
Page 40 and 41: State of the art cylinder rotates a
Page 42 and 43: State of the art 1998). This device
Page 44 and 45: State of the art 26 2.2 Detection o
Page 46 and 47: State of the art The fluorescence s
Page 48 and 49: Definition of the problem and resea
Page 51 and 52: 4 Materials and methods 4.1 Detecti
Page 53 and 54: Materials and methods Figure 4.1 a)
Page 55 and 56: Materials and methods Figure 4.3 a)
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
Page 61 and 62: 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: Materials and methods (PFM). As the
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 114 and 115: Results and discussion 96 5.3.4 Alg
Page 116 and 117: 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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