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Development of a Control System for a Small Size Seeding-performance Test Rig
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IFAC PapersOnLine 52-30 (2019) 202–206
Development of a Control System for a Small Size Seeding-performance Test Rig Development of a Control System for a Small Size Seeding-performance Test Rig Development for aa Small Size Seeding-performance Test Development of of a a Control Control System SystemWei for Small Test Rig Rig Liu*, JianpingSize Hu**Seeding-performance , Wei Liu*, Jianping Hu** , Haoran. Pan*** Wei Jianping Hu** Haoran. Pan*** Wei Liu*, Liu*, Jianping Hu** ,, Haoran. Pan*** Haoran. Pan*** *Jiangsu University, Zhenjiang, 212013, School of Agriculture Engineering, *Jiangsu University, Zhenjiang, 212013,e-mail: [email protected]) of Agriculture Engineering, PR China (Tel: +8618851409914; *Jiangsu University, Zhenjiang, 212013, School of Agriculture Engineering, PR China (Tel: +8618851409914; e-mail: [email protected]) *Jiangsu University, Zhenjiang, 212013, School of **Jiangsu University, Zhenjiang, 212013,e-mail: [email protected]) ofAgriculture AgricultureEngineering, Engineering, PR China (Tel: +8618851409914; **Jiangsu University, Zhenjiang, 212013, School of Agriculture Engineering, PR PR China (Tel: +8618851409914; e-mail: [email protected]) China (Tel: +8613852984643; e-mail: [email protected]) **Jiangsu Zhenjiang, 212013, School Agriculture Engineering, PRUniversity, China (Tel: +8613852984643; e-mail:of [email protected]) **Jiangsu University, Zhenjiang, 212013, of Agriculture ***Jiangsu University, Zhenjiang, 212013,School School of AgricultureEngineering, Engineering, PR China (Tel: +8613852984643; e-mail: [email protected]) ***Jiangsu 212013, School of Agriculture Engineering, PRUniversity, China (Tel:Zhenjiang, +8613852984643; e-mail: [email protected]) PR China (Tel: +8615966091908; e-mail: [email protected]) ***Jiangsu Zhenjiang, School of PR ChinaUniversity, (Tel: +8615966091908; e-mail: [email protected]) ***Jiangsu University, Zhenjiang, 212013, 212013, School of Agriculture Agriculture Engineering, Engineering, PR China (Tel: +8615966091908; e-mail: [email protected]) PR China (Tel: +8615966091908; e-mail: [email protected])
Abstract: Testing a seed drill indoors can save a great amount of time and labour force. Conventional Abstract: Testing a seed drill usually indoorsneed can save a great time and seeding-performance test rigs at least two amount people toof operate it. labour Thus, aforce. smallConventional size test rig Abstract: Testing aa seed drill indoors can save aa great time labour Conventional seeding-performance test rigs usually need atdeveloped. least two amount people toof it. Thus,system aforce. smallwas sizedesigned test rig Abstract: Testing control seed drill indoors can save great amount ofoperate time and and labour force. Conventional with an automatic system need to be In this research, a control seeding-performance test rigs usually need at least two people to operate it. Thus, a small size test with an automatic control system need to be developed. In this research, a control system was designed seeding-performance test rigs usually need at leastshaft two were people to operate Thus, aand small size test rig rig firstly. After that, rotation speed ofneed seed-metering simulated bya it. Simulink the parameters with an automatic control system to be developed. In this research, control system was designed firstly. After that, rotation speed ofneed seed-metering shaft were simulated by and the with ancontrol automatic controlwere system toMoreover, be developed. In this research, a Simulink control system wasparameters designed of the algorithm obtained. an experiment were conducted to calibrate the seed the parameters firstly. After rotationwere speed of shaft were Simulinktoand of thedischarged control algorithm obtained. an experiment were by conducted calibrate the seed and the results, parameters firstly. After that, that, speed of seed-metering seed-metering shaft were simulated simulated by According to Simulink the experimental the mass inrotation per cycle rotated by Moreover, seed-metering shaft. of the control algorithm were obtained. Moreover, an experiment were conducted to calibrate the mass discharged in per cycle rotated by seed-metering shaft. According to the experimental results, the of the control algorithm were obtained. Moreover, an experiment were conducted to calibrate the seed seed average seed mass in per cycle was 12.61 g. In each validating experiment, the value that the theoretical mass discharged cycle rotated by shaft. According to experimental the average seed massin per cycle was g. In divided each validating experiment, value theasresults, theoretical mass mass discharged ininper per cycle rotated by seed-metering seed-metering shaft. According to the the experimental results, the seed subtracted the actual one12.61 and then the theoretical seed mass wasthat seen the error average seed mass in per cycle was 12.61 g. In each validating experiment, the value that the theoretical seed mass subtracted the actual one and then divided the theoretical seed mass was seen as the error average seed mass in per cycle was 12.61 g. In each validating experiment, the value that the theoretical percentage of seed mass. Furthermore, 100% subtracted the error percentage was viewed as the accuracy seed mass subtracted the actual and then divided the seed was seen as the error percentage of The seed results mass. 100% the theoretical error percentage was as the accuracy seed mass subtracted the Furthermore, actual one one thensubtracted divided the theoretical seed mass mass was as error of seed mass. showed that and all accuracies of seed mass were higher thanviewed 82%,seen and thethe average the error percentage was viewed as the accuracy percentage of seed mass. Furthermore, 100% subtracted showed that all accuracies of seed mass were higher than 82%, and the average of seed mass. The results the error percentage was viewed as the accuracy percentageofof total seed mass. Furthermore, 100% subtracted was 89.12%. Furthermore, t-test results showed that there was not accuracy experiments of seed The showed that all accuracies of seed mass higher than the average accuracy ofdifference total experiments was 89.12%. Furthermore, t-testwere results showed that and there was not of seed mass. mass. The results results showed that allseed accuracies ofand seed mass were higher than 82%, 82%, and thestatistical average significant between the actual masses the theoretical ones. According to the accuracy total experiments 89.12%. Furthermore, t-test results showed that was not significant between thewas actual seed masses andapplied the theoretical ones. According tothere the accuracyweof ofdifference experiments was 89.12%. Furthermore, t-test results showed thattest there was results, cantotal conclude that the control system can be on seeding-performance rigsstatistical withnot an significant difference between the actual seed masses and the theoretical ones. According to the statistical results, weperformance. can conclude that the system can be on seeding-performance rigsstatistical with an significant difference between thecontrol actual seed masses andapplied the theoretical ones. Accordingtest to the desirable results, can desirable results, we weperformance. can conclude conclude that that the the control control system system can can be be applied applied on on seeding-performance seeding-performance test test rigs rigs with with an an performance. desirable © 2019, IFAC (International Federation of laboratory Automatic Control) HostingPID by Elsevier Ltd. All rights reserved. Keywords: seeding-performance, experiment, controller, calibrating experiment, performance. desirable Keywords: seeding-performance, laboratory experiment, PID controller, calibrating experiment, simulation. Keywords: simulation. Keywords: seeding-performance, seeding-performance, laboratory laboratory experiment, experiment, PID PID controller, controller, calibrating calibrating experiment, experiment, simulation. simulation. 1. INTRODUCTION 1. INTRODUCTION INTRODUCTION The performance of 1. seed drill plays a vital role in the quality 1. INTRODUCTION The performance of seed drill playsisa avital in the quality of sowing. Seed-metering device keyrole component of a The performance of seed drill plays a vital role of sowing. Seed-metering device is a key component The performance of seed playstoatest vitalperformances role in in the the quality quality seedsowing. drill. Therefore, it is drill essential ofof theaa of Seed-metering device is a key component of seed drill. Therefore, it is essential to test performances of of sowing. Seed-metering device is a key component ofthea seed-metering device itduring the development process. Using seed drill. Therefore, is essential to test performances of the seed-metering device during the development process. Using seed drill. Therefore, it is essential to test performances of the conventional methods, seed drills have to run in the fields. It seed-metering device during the development process. Using conventional methods, seed drills have to run in the fields. It seed-metering device during the development process. Using can really assess the performance of the seed drill with the conventional methods, seed drills have to run in the fields. It can really assess the performance of the seed drill with the conventional methods, seed drills have to run in the fields. It influences causedthe byperformance external inference, suchdrill as with machine can really assess of the seed the influences caused by external inference, such as machine can really assess the performance of the seed drill with the and so on. However, due bumping, ground surficial stubble, influences caused by external inference, such as machine and so on. due bumping, ground surficial stubble, influences caused by external inference, suchHowever, as machine to covered soil, the discharged seeds in the fields are difficult and so on. However, due bumping, ground surficial stubble, to covered soil, the discharged seeds in the fields are difficult and so on. However, bumping, ground surficial stubble, to find, let soil, alonethe count exact seed number. Also, this workdue is to covered discharged seeds in the fields are difficult to find, let alone count exact seed number. Also, this work is covered soil, the discharged seeds in the fields are difficult labour-consuming andexact time-consuming. Moreover, the to find, let alone count seed number. Also, this work is labour-consuming and time-consuming. Moreover, the to find, let alone exact seed work or is experiments are count alsoand affected by number. weather.Also, IfMoreover, it this is rainy labour-consuming time-consuming. the experiments are alsoand affected by weather. orIfMoreover, it is rainy the or labour-consuming time-consuming. snowy, the experiments have to be canceled delayed. experiments are weather. it snowy, the experiments have to by be canceled experiments are also also affected affected by weather. orIf Ifdelayed. it is is rainy rainy or or snowy, the experiments have to be canceled or delayed. Thus, rigscanceled used in or laboratories snowy,seeding-performance the experiments havetest to be delayed. were Thus, seeding-performance test drawbacks. rigs used in That laboratories were developed to overcome above is to say, it Thus, seeding-performance test rigs used in laboratories were developed to overcome above drawbacks. That is to say, it Thus, seeding-performance test rigs used in laboratories were the weather is, and can be used at any time no matter what developed to overcome above drawbacks. That is to say, it the weather is, and can be used at any time no matter what developed to overcome above drawbacks. That is to say, it just a few researchers could operate it the via weather its automation is, and can be used at any time no matter what just a few researchers could operate it via its automation the weather is, and can be used at any time no matter what control system. just researchers control system. just aa few few researchers could could operate operate it it via via its its automation automation control system. In ordersystem. to simulate the condition that a seed drill travels in control In order theseeding-performance condition that a seedtest drill travels in the field,to thesimulate available rigs usually In order to simulate the condition that aa seed drill travels in the field, the available seeding-performance test rigs usually In order to simulate the condition that seed drill travels in contain a cycle moving belt. In 1998, Hao Jin test et al.rigs developed the field, the available seeding-performance usually contain a cycle moving belt. In 1998, Hao Jin et al. developed the field, the available seeding-performance test rigs usually a seeding-performance test rig based on the visual instrument contain aa cycle belt. In 1998, Hao Jin et developed a seeding-performance contain cycle moving moving test belt.rig In based 1998, on Haothe Jinvisual et al. al. instrument developed aa seeding-performance test rig based on the visual instrument seeding-performance test rig based on the visual instrument
technique. The test rig had a graphic human machine technique.to show The test rigchart had ofa seed graphic human machine interface the line spaces. technique. The rig had graphic human interface the line spaces. technique.to show The test test rigchart had ofaa seed graphic human machine machine show the line chart of seed spaces. interface to In 2008, Yanxia et al.chart developed control system which interface to showGuo the line of seed aspaces. In 2008, Yanxia Guo etControl al. developed a control system whicha used a MCU (Micro Unit) AT89S52 to control In 2008, Yanxia Guo et al. developed aa control system whicha used a MCU (Micro Control Unit) AT89S52 to control In 2008, Yanxia Guo et al. developed control system variable-frequency motor which connected with a which seed-a used a MCU (Micro Control Unit) AT89S52 to control variable-frequency motor which a seedused a MCU (Micro Control Unit)connected AT89S52with tomotor control metering shaft. Thus, the variable-frequency cana variable-frequency motor which connected with aa seedmetering shaft. Thus, the variable-frequency motor variable-frequency motor which connected with seedchange theshaft. rotations of the seed-metering shaft based on can the metering Thus, variable-frequency motor change the rotations of seed-metering shaft based on can the meteringfrequencies shaft. Thus, the from variable-frequency motor can adjusted received the MCU. change the rotations of seed-metering shaft based on adjusted frequencies received from the MCU. change the rotations of seed-metering shaft based on the the adjusted frequencies received Also, seeding-performance test MCU. rig control system adjustedthe frequencies received from from the the MCU. Also, the from seeding-performance test rig technologies. control system benefited advanced communication In Also, the seeding-performance test rig control system In benefited from advanced communication technologies. Also, the seeding-performance test rig control seedingsystem 2011, Quanze Wu et al. developed the JSP-16 benefited from advanced communication technologies. In 2011, Quanze Wu et al. developed the JSP-16 seedingbenefited from advanced communication technologies. In performance test rig which is based on the real-time 2011, Quanze Wu et al. developed the JSP-16 seedingperformance test rig which is based on the real-time 2011, Quanze Wu et al. developed the JSP-16 seedingcommunication between a PLC and a variable-frequency performance test rig which is based on communication between a PLC a industrial variable-frequency performance testthe rig which is and based on the the real-time real-time driver. As for control system, an personal communication between a PLC and a variable-frequency driver. As for the control system, an industrial personal communication between a PLC and a variable-frequency computer was usedcontrol as thesystem, host computer to load the driver. As for the an industrial personal computer was used as the host computer to load the driver. As for parameters the control inputted system, an personal experimental by industrial researchers and computer was used as the host computer to load the experimental parameters by researchers and computer the wasspecific used as theinputted host computer to loadmotor the calculate rotations of the seed-metering experimental parameters inputted by researchers and calculate the specific rotations of the by seed-metering experimental parameters inputted researchers motor and automatically. calculate automatically. calculate the the specific specific rotations rotations of of the the seed-metering seed-metering motor motor automatically. In 2014, Jian Zhao designed a seeding-performance which automatically. In 2014,silver Jian Zhao designed seeding-performance which applied sand to replaceaa oil to capture seeds on the designed seeding-performance which In 2014, Jian Zhao silver sand to replace oil to capture seeds on the applied designedthea control seeding-performance which In 2014,belt Jianand Zhao moving simplified system compared to applied sand to to seeds on moving beltsystem. and simplified therigoil control system compared to applied silver silver sand to replace replace oil to capture capture seeds on the the traditional This test can reuse the discharged moving beltsystem. and simplified control system compared to traditional This testthe can reuse discharged moving andsands. simplified therig control system compared to seeds andbelt silver In 2014, Deividson L. etthe al. applied an traditional system. This test rig can reuse the discharged seeds and silver sands. In 2014, Deividson L. et al. applied an traditional system. This test rig can reuse the discharged infrared ray sensor to detect the corn seed on the running belt. seeds silver sands. In Deividson L. et applied an infrared sensor to detect the corn seed on running belt. seeds and andray silver sands. In 2014, 2014, Deividson L.the et al. al. applied an infrared ray sensor to detect the corn seed on the running belt. infrared ray sensor to detect the corn seed on the running belt.
2405-8963 © 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Copyright © 2019 IFAC 202 Peer review©under of International Federation of Automatic Copyright 2019 responsibility IFAC 202Control. 10.1016/j.ifacol.2019.12.522 Copyright © 2019 IFAC 202 Copyright © 2019 IFAC 202
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However, the moving belt results in the factor that test rigs are extremely bulky. In addition, some traditional seeding test rigs need to hang the whole seed drill over the belt, which is difficult to be done by only one researcher. Hence, a smallsize and user-friendly seeding-performance test rig need to be developed. As a crucial part of the above objective, the aim of this research was to develop a control system for a small-size seeding-performance test rig. Only one person is needed to operate the test rig. Moreover, based on stepper motor, a rotation control algorithm was proposed to enable the seedmetering shaft rotate follow the theoretical rotation speed as accuracy as possible. In next step, a calibrating experiment was conducted to calibrate the mass of discharged seeds when seed-metering device rotates a cycle, and then a validating experiment was conducted to assess the performance of the designed control system. 2. MATERIALS AND METHODS 2.1 Working Principles and Key Components of the Smallsize Seeding-performance Test Rig The control system incorporated of a upper computer, a ACDC power converter（Siemens, Germany）, a controller, an embedded data acquisition unit, a seed flow rate sensor, a stepper motor driver, a stepper motor (Time Brilliant, Co Ltd., China), an universal seed-metering device and a digital balance. The sketch and real product photo of the seedingperformance test rig are shown in Fig. 1 and Fig. 2.
Fig. 2. Real product photo of the seeding-performance test rig. When seeds were ejected by the seed-metering device, they would pass through the opposite-type seed flow rate sensor unit which contained a fiber transmitter, a fiber receiver (FUA40, KEYENCE Co Ltd., Japan) and a amplifier (FSN11MN, KEYENCE Co Ltd., Japan). The amplifier can output an analog value from 1 to 5V. The value of the output was linear to the receiver area which can receive lights, i.e. the output of the sensor had a linear relationship with the seed flow rate at sampling points. The fiber sensor unit was installed at the outlet of the seed-metering device, as seen in Fig. 3.
Fig. 3. Installation position of the fiber sensor unit.
Fig. 1. Sketch of a small size seeding-performance test rig. The static seeds in the hopper would be discharged by the seed-metering device and then formed a continuous seed flow. It was easy to replace any type of seed-metering devices on the seeding-performance test rig. We can input the experimental parameters into the controller. After that, the controller would transmit electric impulses at a certain frequency to the motor driver which would control the stepper motor to rotate at a theoretical rotation speed. 203
A digital balance (BSM520.3, Shanghai Zhuojing electronic Co Ltd., China) was used to measure the real value of seed flow rates. In order to reduce the measure errors caused by seeds impact, a little cotton was matted between the seed container and the digital balance. The digital balance was communicated with the embedded data acquisition unit by RS232 serial communication protocol. The transmission period was 0.33s.
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The core component of the embedded data acquisition unit was a micro control unit (STM32F103ZET6, STMicroelectronics, Italy). The port PA1 was used as an ADC to detect the analog value of the seed flow rate sensor and port PA9 and PA10 were used to communicate with the digital balance. 2.2 Simulation of the Control System. The simulation of the control system was conducted in Matlab/Simulink 2014 environment (Fig. 4). Four parameters, including seed amount per hectare, seed drill forward speed, machine width and the number of single seeding units need to be set at beginning. The seed amount was a typical value in
Jiangsu province of China. The other inputted values were as same as them of a seed drill product (Xintian machinery manufacture Co Ltd, Jiangsu, China) on the market. The theoretical seed flow rate was calculated using (1), f
Q V W . 10 U n
(1)
where f represents the theoretical seed flow rate, g/s; Q is the total seed amount in per hectare, kg/ha; V indicates the forward speed of the seed drill, m/s; W is the width of the seed drill, m; Un is the number of single seeding units. In this research, the Q, V, W and Un were 150-225, 0.83-2, 2.4 and 14 respectively.
Fig. 4. Simulation model of the control system. And then the theoretical seed flow rate need to be transferred to the rotational speed of motor, (2) A 360 f q 1 . Where A is the theoretical rotational speed, ° /s; q indicate the falling seed mass when seed-metering shaft rotates a cycle. The PID controller contained three parameters,namely proportion (Kp), integrate (Ki) and differential (Kd) parameter respectively. With respect to the simulation, the exact number of the parameters were listed in Table 1 and the performance indexes of the PID controller were listed in Table 2. Table 1. Parameters of the PID controller. Parameters
Kp
Ki
Kd
N
Value
12.36
8.05
6.57
187.26
The parameter N was the filter coefficient of the differential parameter, which was used to eliminate peak noises. With the filter parameter N, the Laplace transform of the differential item can be written as N Kd N (3) s K , 1 sN d 1 N s Where Kd is the differential parameter and s represents the Laplace operator. 204
Table 2. Performance indexes of the PID controller
Index
Rising Time (s)
Settling Time (s)
Value
0.0145
2.19
Overshoot (%) 11.5
Peak Time (s) 1.12
The output of the stepper motor was the rotated angle in per second, and then it should multiple the mass of the discharged seeds in per second. The mass curve of discharged seed flow rate is illustrated in Fig. 5.
Fig. 5. Theoretical seed flow rate versus the real one.
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2.3 Experimental Research In order to assess the stability and robustness of the control system, a one-factor and five levels validating experiment should be conducted under different theoretical seed flow rates. According to (1), the levels of the theoretical seed flow rate were 2.1, 3.15, 4.2, 5.25 and 6.3 g/s, which can cover whole actual seed flow rate in practice. Every level would be replicated 5 times and the experimental time of each treatment was 5s; so the theoretical total seed masses were 10.5, 15.75, 21, 26.25 and 31.5 grams, respectively. In this study, wheat seeds whose thousand mass is 42.00 g were used as experimental materials. The shape of those seeds was elongated shape and the size of them were length 6.17± 0.33mm, width 3.28±0.35mm and thickness 2.96± 0.5mm respectively. 3. RESULTS AND DISCUSSIONS
more time, the accuracy would rise, because according to Fig. 5, after 5 seconds, the steady-state error would be less than 2%. We can see from Table 3. When theoretical total seed mass was 15.75g, the errors of the seed flow rate reach to the maximum. As the seed flow rate went up, the accuracy of the control system would increase. The average accuracy of total treatments was 89.12%. When the seed flow rate less than 6.3 g/s, the actual seed mass would less than the theoretical value; nevertheless, when the rotation speed of the seed-metering shaft was fast enough, i.e. the theoretical seed mass was up to 31.5 grams per 5 seconds, resulting in the control error decreasing to minimum. Table 3. Theoretical seed masses and actual ones in each repetition. Rn R1 Va (g)
Vt
3.1 Seed Flow Rate Calibration In order to control seed flow rate accurately, it is necessary to understand the mass of discharged seeds during a cycle of the seed-metering shaft. The stepper motor revolved 5 cycles under different rotation speeds, namely 10, 15, 20, 25, 30 rotations per minute. The seed-metering shaft was directly driven by the stepper motor via a coupling and the transmission ratio was 1:1. The experimental results are shown in Fig. 6.
205
R2
R3
R4
R5
Mean
ACY
(g)
(g)
(g)
(g)
(g)
(%)
10.5
9.17
10.28
10.81
9.03
9.79
9.82
93.52
15.75
14.69
12.81
13.17
12.56
13.49
13.35
84.76
21
20.28
18.79
17.03
18.18
18.37
18.53
88.24
26.25
23.65
22.95
21.03
21.46
22.53
22.33
85.07
31.5
30.64
29.54
30.13
28.49
30.69
29.90
94.92
Note: ACY is mean accuracy; Vt indicates the theoretical seed mass; Va represents the actual seed mass under different theoretical seed masses and repetitions; and the Rn is the number of repetitions. The actual seed mass would show an obvious linear relationship as the theoretical seed mass increases (Fig. 7). According to the statistical results (obtained by IBM SPSS Statistical 21), the coefficient of determination R 2 was 0.981. The fit equation was also calculated by SPSS software as follows: (4) M a 0.936 M t 0.870 , where Ma is the actual seed mass, g; Mt represents the theoretical seed mass. The actual seed mass increased trend and its fit equation both show in the Fig. 7.
Fig. 6. Discharged seed masses during a seed-metering shaft cycle. The results showed that the rotation speed of the seedmetering shaft was not a significant factor on mass of seeds discharged in per cycle. Thus, the average value q (12.61 g) of the discharged seed mass in per cycle was applied in the subsequent experiment. 3.2 Validating Experiment The actual seed masses versus the theoretical ones are shown in Table 3. There were 29 out of 30 of actual seed masses are less than their corresponding theoretical value. Combing with the simulation curve (Fig. 5), the control system would approach to the theoretical seed flow rate gradually after overshoot. Since the peak time, the actual seed flow rate was lower than the theoretical one. If the experiments continue 205
Fig. 7. Average of actual seed mass at each level and the fit equation between the actual masses and the theoretical ones.
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According to the Table 4, the actual seed mass does not have significant different with the theoretical values, as the value of sig. was more than 0.05. Thus, we can conclude the control system can control the seed-metering device to generate accurate seed flow rates. Table 4. Independent t-test result.
Value
F
t
df
Sig. (two sides)
0.025
-0.433
8
0.676
4. CONCLUSIONS This paper proposed a control system for a small-size seeding-performance test rig. Firstly, the hardware of the control system was designed and then the whole control model was built. Based on the mathematical model , the PID parameters were tuned by the Simulink software. Moreover, an experiment was performed to calibrate the mass of the seeds ejected in one seed-metering shaft cycle. Furthermore, a one-factor validating experiment was conducted to evaluate the accuracy of the developed control system. The results showed that the actual seed masses were slight less than the theoretical ones, but all accuracies were more than 82% and the average accuracy was 89.12%. Moreover, according to the linear regression result, it is obvious that the actual seed theoretical mass is linear as the theoretical seed flow rate went up. In addition, the fit equation illustrate that there was a strong linear relationship between the actual seed masses and the theoretical ones. Finally, an independent t-test was performed. The results showed that the significance was more than 0.05; therefore the actual seed masses were not significantly different with the theoretical ones. That is, the performance of the control system is acceptable and the small size seeding-performance test rig can be used for seed-metering device testing in laboratory. REFERENCES Deividson L.O. and Rosane F. (2014). Computers and electronics in Agriculture. Usage of the DFRobot RB-DFR49 Infrared Sensor to detect maize seed passage on a conveyor belt, 102, 106-111. Hao Jin and Huanwen Gao.(1999). Transactions of the Chinese Society for Agricultural Machinery. Virtual instrument technique and its applications in agriculture automatinon [J], 30(3), 108-112. Jian Z. Seeding-performance test rig control system and the design of its key components. Diss. 2014. Yanxia Guo, Weina Liu, Qiuxia Zhao, Na Li. (2008). Journal of Agricultural Mechanization Research. Research on microprocessing control system of precision seeding, 9, 81-83.
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Zequan Wu, Junjie Liu, Xu Yang. (2011). Journal of Agricultural Mechanization Research. The design of the JSP16 seeding test rig, 10, 34-37.
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IFAC PapersOnLine 52-30 (2019) 202–206
Development of a Control System for a Small Size Seeding-performance Test Rig Development of a Control System for a Small Size Seeding-performance Test Rig Development for aa Small Size Seeding-performance Test Development of of a a Control Control System SystemWei for Small Test Rig Rig Liu*, JianpingSize Hu**Seeding-performance , Wei Liu*, Jianping Hu** , Haoran. Pan*** Wei Jianping Hu** Haoran. Pan*** Wei Liu*, Liu*, Jianping Hu** ,, Haoran. Pan*** Haoran. Pan*** *Jiangsu University, Zhenjiang, 212013, School of Agriculture Engineering, *Jiangsu University, Zhenjiang, 212013,e-mail: [email protected]) of Agriculture Engineering, PR China (Tel: +8618851409914; *Jiangsu University, Zhenjiang, 212013, School of Agriculture Engineering, PR China (Tel: +8618851409914; e-mail: [email protected]) *Jiangsu University, Zhenjiang, 212013, School of **Jiangsu University, Zhenjiang, 212013,e-mail: [email protected]) ofAgriculture AgricultureEngineering, Engineering, PR China (Tel: +8618851409914; **Jiangsu University, Zhenjiang, 212013, School of Agriculture Engineering, PR PR China (Tel: +8618851409914; e-mail: [email protected]) China (Tel: +8613852984643; e-mail: [email protected]) **Jiangsu Zhenjiang, 212013, School Agriculture Engineering, PRUniversity, China (Tel: +8613852984643; e-mail:of [email protected]) **Jiangsu University, Zhenjiang, 212013, of Agriculture ***Jiangsu University, Zhenjiang, 212013,School School of AgricultureEngineering, Engineering, PR China (Tel: +8613852984643; e-mail: [email protected]) ***Jiangsu 212013, School of Agriculture Engineering, PRUniversity, China (Tel:Zhenjiang, +8613852984643; e-mail: [email protected]) PR China (Tel: +8615966091908; e-mail: [email protected]) ***Jiangsu Zhenjiang, School of PR ChinaUniversity, (Tel: +8615966091908; e-mail: [email protected]) ***Jiangsu University, Zhenjiang, 212013, 212013, School of Agriculture Agriculture Engineering, Engineering, PR China (Tel: +8615966091908; e-mail: [email protected]) PR China (Tel: +8615966091908; e-mail: [email protected])
Abstract: Testing a seed drill indoors can save a great amount of time and labour force. Conventional Abstract: Testing a seed drill usually indoorsneed can save a great time and seeding-performance test rigs at least two amount people toof operate it. labour Thus, aforce. smallConventional size test rig Abstract: Testing aa seed drill indoors can save aa great time labour Conventional seeding-performance test rigs usually need atdeveloped. least two amount people toof it. Thus,system aforce. smallwas sizedesigned test rig Abstract: Testing control seed drill indoors can save great amount ofoperate time and and labour force. Conventional with an automatic system need to be In this research, a control seeding-performance test rigs usually need at least two people to operate it. Thus, a small size test with an automatic control system need to be developed. In this research, a control system was designed seeding-performance test rigs usually need at leastshaft two were people to operate Thus, aand small size test rig rig firstly. After that, rotation speed ofneed seed-metering simulated bya it. Simulink the parameters with an automatic control system to be developed. In this research, control system was designed firstly. After that, rotation speed ofneed seed-metering shaft were simulated by and the with ancontrol automatic controlwere system toMoreover, be developed. In this research, a Simulink control system wasparameters designed of the algorithm obtained. an experiment were conducted to calibrate the seed the parameters firstly. After rotationwere speed of shaft were Simulinktoand of thedischarged control algorithm obtained. an experiment were by conducted calibrate the seed and the results, parameters firstly. After that, that, speed of seed-metering seed-metering shaft were simulated simulated by According to Simulink the experimental the mass inrotation per cycle rotated by Moreover, seed-metering shaft. of the control algorithm were obtained. Moreover, an experiment were conducted to calibrate the mass discharged in per cycle rotated by seed-metering shaft. According to the experimental results, the of the control algorithm were obtained. Moreover, an experiment were conducted to calibrate the seed seed average seed mass in per cycle was 12.61 g. In each validating experiment, the value that the theoretical mass discharged cycle rotated by shaft. According to experimental the average seed massin per cycle was g. In divided each validating experiment, value theasresults, theoretical mass mass discharged ininper per cycle rotated by seed-metering seed-metering shaft. According to the the experimental results, the seed subtracted the actual one12.61 and then the theoretical seed mass wasthat seen the error average seed mass in per cycle was 12.61 g. In each validating experiment, the value that the theoretical seed mass subtracted the actual one and then divided the theoretical seed mass was seen as the error average seed mass in per cycle was 12.61 g. In each validating experiment, the value that the theoretical percentage of seed mass. Furthermore, 100% subtracted the error percentage was viewed as the accuracy seed mass subtracted the actual and then divided the seed was seen as the error percentage of The seed results mass. 100% the theoretical error percentage was as the accuracy seed mass subtracted the Furthermore, actual one one thensubtracted divided the theoretical seed mass mass was as error of seed mass. showed that and all accuracies of seed mass were higher thanviewed 82%,seen and thethe average the error percentage was viewed as the accuracy percentage of seed mass. Furthermore, 100% subtracted showed that all accuracies of seed mass were higher than 82%, and the average of seed mass. The results the error percentage was viewed as the accuracy percentageofof total seed mass. Furthermore, 100% subtracted was 89.12%. Furthermore, t-test results showed that there was not accuracy experiments of seed The showed that all accuracies of seed mass higher than the average accuracy ofdifference total experiments was 89.12%. Furthermore, t-testwere results showed that and there was not of seed mass. mass. The results results showed that allseed accuracies ofand seed mass were higher than 82%, 82%, and thestatistical average significant between the actual masses the theoretical ones. According to the accuracy total experiments 89.12%. Furthermore, t-test results showed that was not significant between thewas actual seed masses andapplied the theoretical ones. According tothere the accuracyweof ofdifference experiments was 89.12%. Furthermore, t-test results showed thattest there was results, cantotal conclude that the control system can be on seeding-performance rigsstatistical withnot an significant difference between the actual seed masses and the theoretical ones. According to the statistical results, weperformance. can conclude that the system can be on seeding-performance rigsstatistical with an significant difference between thecontrol actual seed masses andapplied the theoretical ones. Accordingtest to the desirable results, can desirable results, we weperformance. can conclude conclude that that the the control control system system can can be be applied applied on on seeding-performance seeding-performance test test rigs rigs with with an an performance. desirable © 2019, IFAC (International Federation of laboratory Automatic Control) HostingPID by Elsevier Ltd. All rights reserved. Keywords: seeding-performance, experiment, controller, calibrating experiment, performance. desirable Keywords: seeding-performance, laboratory experiment, PID controller, calibrating experiment, simulation. Keywords: simulation. Keywords: seeding-performance, seeding-performance, laboratory laboratory experiment, experiment, PID PID controller, controller, calibrating calibrating experiment, experiment, simulation. simulation. 1. INTRODUCTION 1. INTRODUCTION INTRODUCTION The performance of 1. seed drill plays a vital role in the quality 1. INTRODUCTION The performance of seed drill playsisa avital in the quality of sowing. Seed-metering device keyrole component of a The performance of seed drill plays a vital role of sowing. Seed-metering device is a key component The performance of seed playstoatest vitalperformances role in in the the quality quality seedsowing. drill. Therefore, it is drill essential ofof theaa of Seed-metering device is a key component of seed drill. Therefore, it is essential to test performances of of sowing. Seed-metering device is a key component ofthea seed-metering device itduring the development process. Using seed drill. Therefore, is essential to test performances of the seed-metering device during the development process. Using seed drill. Therefore, it is essential to test performances of the conventional methods, seed drills have to run in the fields. It seed-metering device during the development process. Using conventional methods, seed drills have to run in the fields. It seed-metering device during the development process. Using can really assess the performance of the seed drill with the conventional methods, seed drills have to run in the fields. It can really assess the performance of the seed drill with the conventional methods, seed drills have to run in the fields. It influences causedthe byperformance external inference, suchdrill as with machine can really assess of the seed the influences caused by external inference, such as machine can really assess the performance of the seed drill with the and so on. However, due bumping, ground surficial stubble, influences caused by external inference, such as machine and so on. due bumping, ground surficial stubble, influences caused by external inference, suchHowever, as machine to covered soil, the discharged seeds in the fields are difficult and so on. However, due bumping, ground surficial stubble, to covered soil, the discharged seeds in the fields are difficult and so on. However, bumping, ground surficial stubble, to find, let soil, alonethe count exact seed number. Also, this workdue is to covered discharged seeds in the fields are difficult to find, let alone count exact seed number. Also, this work is covered soil, the discharged seeds in the fields are difficult labour-consuming andexact time-consuming. Moreover, the to find, let alone count seed number. Also, this work is labour-consuming and time-consuming. Moreover, the to find, let alone exact seed work or is experiments are count alsoand affected by number. weather.Also, IfMoreover, it this is rainy labour-consuming time-consuming. the experiments are alsoand affected by weather. orIfMoreover, it is rainy the or labour-consuming time-consuming. snowy, the experiments have to be canceled delayed. experiments are weather. it snowy, the experiments have to by be canceled experiments are also also affected affected by weather. orIf Ifdelayed. it is is rainy rainy or or snowy, the experiments have to be canceled or delayed. Thus, rigscanceled used in or laboratories snowy,seeding-performance the experiments havetest to be delayed. were Thus, seeding-performance test drawbacks. rigs used in That laboratories were developed to overcome above is to say, it Thus, seeding-performance test rigs used in laboratories were developed to overcome above drawbacks. That is to say, it Thus, seeding-performance test rigs used in laboratories were the weather is, and can be used at any time no matter what developed to overcome above drawbacks. That is to say, it the weather is, and can be used at any time no matter what developed to overcome above drawbacks. That is to say, it just a few researchers could operate it the via weather its automation is, and can be used at any time no matter what just a few researchers could operate it via its automation the weather is, and can be used at any time no matter what control system. just researchers control system. just aa few few researchers could could operate operate it it via via its its automation automation control system. In ordersystem. to simulate the condition that a seed drill travels in control In order theseeding-performance condition that a seedtest drill travels in the field,to thesimulate available rigs usually In order to simulate the condition that aa seed drill travels in the field, the available seeding-performance test rigs usually In order to simulate the condition that seed drill travels in contain a cycle moving belt. In 1998, Hao Jin test et al.rigs developed the field, the available seeding-performance usually contain a cycle moving belt. In 1998, Hao Jin et al. developed the field, the available seeding-performance test rigs usually a seeding-performance test rig based on the visual instrument contain aa cycle belt. In 1998, Hao Jin et developed a seeding-performance contain cycle moving moving test belt.rig In based 1998, on Haothe Jinvisual et al. al. instrument developed aa seeding-performance test rig based on the visual instrument seeding-performance test rig based on the visual instrument
technique. The test rig had a graphic human machine technique.to show The test rigchart had ofa seed graphic human machine interface the line spaces. technique. The rig had graphic human interface the line spaces. technique.to show The test test rigchart had ofaa seed graphic human machine machine show the line chart of seed spaces. interface to In 2008, Yanxia et al.chart developed control system which interface to showGuo the line of seed aspaces. In 2008, Yanxia Guo etControl al. developed a control system whicha used a MCU (Micro Unit) AT89S52 to control In 2008, Yanxia Guo et al. developed aa control system whicha used a MCU (Micro Control Unit) AT89S52 to control In 2008, Yanxia Guo et al. developed control system variable-frequency motor which connected with a which seed-a used a MCU (Micro Control Unit) AT89S52 to control variable-frequency motor which a seedused a MCU (Micro Control Unit)connected AT89S52with tomotor control metering shaft. Thus, the variable-frequency cana variable-frequency motor which connected with aa seedmetering shaft. Thus, the variable-frequency motor variable-frequency motor which connected with seedchange theshaft. rotations of the seed-metering shaft based on can the metering Thus, variable-frequency motor change the rotations of seed-metering shaft based on can the meteringfrequencies shaft. Thus, the from variable-frequency motor can adjusted received the MCU. change the rotations of seed-metering shaft based on adjusted frequencies received from the MCU. change the rotations of seed-metering shaft based on the the adjusted frequencies received Also, seeding-performance test MCU. rig control system adjustedthe frequencies received from from the the MCU. Also, the from seeding-performance test rig technologies. control system benefited advanced communication In Also, the seeding-performance test rig control system In benefited from advanced communication technologies. Also, the seeding-performance test rig control seedingsystem 2011, Quanze Wu et al. developed the JSP-16 benefited from advanced communication technologies. In 2011, Quanze Wu et al. developed the JSP-16 seedingbenefited from advanced communication technologies. In performance test rig which is based on the real-time 2011, Quanze Wu et al. developed the JSP-16 seedingperformance test rig which is based on the real-time 2011, Quanze Wu et al. developed the JSP-16 seedingcommunication between a PLC and a variable-frequency performance test rig which is based on communication between a PLC a industrial variable-frequency performance testthe rig which is and based on the the real-time real-time driver. As for control system, an personal communication between a PLC and a variable-frequency driver. As for the control system, an industrial personal communication between a PLC and a variable-frequency computer was usedcontrol as thesystem, host computer to load the driver. As for the an industrial personal computer was used as the host computer to load the driver. As for parameters the control inputted system, an personal experimental by industrial researchers and computer was used as the host computer to load the experimental parameters by researchers and computer the wasspecific used as theinputted host computer to loadmotor the calculate rotations of the seed-metering experimental parameters inputted by researchers and calculate the specific rotations of the by seed-metering experimental parameters inputted researchers motor and automatically. calculate automatically. calculate the the specific specific rotations rotations of of the the seed-metering seed-metering motor motor automatically. In 2014, Jian Zhao designed a seeding-performance which automatically. In 2014,silver Jian Zhao designed seeding-performance which applied sand to replaceaa oil to capture seeds on the designed seeding-performance which In 2014, Jian Zhao silver sand to replace oil to capture seeds on the applied designedthea control seeding-performance which In 2014,belt Jianand Zhao moving simplified system compared to applied sand to to seeds on moving beltsystem. and simplified therigoil control system compared to applied silver silver sand to replace replace oil to capture capture seeds on the the traditional This test can reuse the discharged moving beltsystem. and simplified control system compared to traditional This testthe can reuse discharged moving andsands. simplified therig control system compared to seeds andbelt silver In 2014, Deividson L. etthe al. applied an traditional system. This test rig can reuse the discharged seeds and silver sands. In 2014, Deividson L. et al. applied an traditional system. This test rig can reuse the discharged infrared ray sensor to detect the corn seed on the running belt. seeds silver sands. In Deividson L. et applied an infrared sensor to detect the corn seed on running belt. seeds and andray silver sands. In 2014, 2014, Deividson L.the et al. al. applied an infrared ray sensor to detect the corn seed on the running belt. infrared ray sensor to detect the corn seed on the running belt.
2405-8963 © 2019, IFAC (International Federation of Automatic Control) Hosting by Elsevier Ltd. All rights reserved. Copyright © 2019 IFAC 202 Peer review©under of International Federation of Automatic Copyright 2019 responsibility IFAC 202Control. 10.1016/j.ifacol.2019.12.522 Copyright © 2019 IFAC 202 Copyright © 2019 IFAC 202
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However, the moving belt results in the factor that test rigs are extremely bulky. In addition, some traditional seeding test rigs need to hang the whole seed drill over the belt, which is difficult to be done by only one researcher. Hence, a smallsize and user-friendly seeding-performance test rig need to be developed. As a crucial part of the above objective, the aim of this research was to develop a control system for a small-size seeding-performance test rig. Only one person is needed to operate the test rig. Moreover, based on stepper motor, a rotation control algorithm was proposed to enable the seedmetering shaft rotate follow the theoretical rotation speed as accuracy as possible. In next step, a calibrating experiment was conducted to calibrate the mass of discharged seeds when seed-metering device rotates a cycle, and then a validating experiment was conducted to assess the performance of the designed control system. 2. MATERIALS AND METHODS 2.1 Working Principles and Key Components of the Smallsize Seeding-performance Test Rig The control system incorporated of a upper computer, a ACDC power converter（Siemens, Germany）, a controller, an embedded data acquisition unit, a seed flow rate sensor, a stepper motor driver, a stepper motor (Time Brilliant, Co Ltd., China), an universal seed-metering device and a digital balance. The sketch and real product photo of the seedingperformance test rig are shown in Fig. 1 and Fig. 2.
Fig. 2. Real product photo of the seeding-performance test rig. When seeds were ejected by the seed-metering device, they would pass through the opposite-type seed flow rate sensor unit which contained a fiber transmitter, a fiber receiver (FUA40, KEYENCE Co Ltd., Japan) and a amplifier (FSN11MN, KEYENCE Co Ltd., Japan). The amplifier can output an analog value from 1 to 5V. The value of the output was linear to the receiver area which can receive lights, i.e. the output of the sensor had a linear relationship with the seed flow rate at sampling points. The fiber sensor unit was installed at the outlet of the seed-metering device, as seen in Fig. 3.
Fig. 3. Installation position of the fiber sensor unit.
Fig. 1. Sketch of a small size seeding-performance test rig. The static seeds in the hopper would be discharged by the seed-metering device and then formed a continuous seed flow. It was easy to replace any type of seed-metering devices on the seeding-performance test rig. We can input the experimental parameters into the controller. After that, the controller would transmit electric impulses at a certain frequency to the motor driver which would control the stepper motor to rotate at a theoretical rotation speed. 203
A digital balance (BSM520.3, Shanghai Zhuojing electronic Co Ltd., China) was used to measure the real value of seed flow rates. In order to reduce the measure errors caused by seeds impact, a little cotton was matted between the seed container and the digital balance. The digital balance was communicated with the embedded data acquisition unit by RS232 serial communication protocol. The transmission period was 0.33s.
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The core component of the embedded data acquisition unit was a micro control unit (STM32F103ZET6, STMicroelectronics, Italy). The port PA1 was used as an ADC to detect the analog value of the seed flow rate sensor and port PA9 and PA10 were used to communicate with the digital balance. 2.2 Simulation of the Control System. The simulation of the control system was conducted in Matlab/Simulink 2014 environment (Fig. 4). Four parameters, including seed amount per hectare, seed drill forward speed, machine width and the number of single seeding units need to be set at beginning. The seed amount was a typical value in
Jiangsu province of China. The other inputted values were as same as them of a seed drill product (Xintian machinery manufacture Co Ltd, Jiangsu, China) on the market. The theoretical seed flow rate was calculated using (1), f
Q V W . 10 U n
(1)
where f represents the theoretical seed flow rate, g/s; Q is the total seed amount in per hectare, kg/ha; V indicates the forward speed of the seed drill, m/s; W is the width of the seed drill, m; Un is the number of single seeding units. In this research, the Q, V, W and Un were 150-225, 0.83-2, 2.4 and 14 respectively.
Fig. 4. Simulation model of the control system. And then the theoretical seed flow rate need to be transferred to the rotational speed of motor, (2) A 360 f q 1 . Where A is the theoretical rotational speed, ° /s; q indicate the falling seed mass when seed-metering shaft rotates a cycle. The PID controller contained three parameters,namely proportion (Kp), integrate (Ki) and differential (Kd) parameter respectively. With respect to the simulation, the exact number of the parameters were listed in Table 1 and the performance indexes of the PID controller were listed in Table 2. Table 1. Parameters of the PID controller. Parameters
Kp
Ki
Kd
N
Value
12.36
8.05
6.57
187.26
The parameter N was the filter coefficient of the differential parameter, which was used to eliminate peak noises. With the filter parameter N, the Laplace transform of the differential item can be written as N Kd N (3) s K , 1 sN d 1 N s Where Kd is the differential parameter and s represents the Laplace operator. 204
Table 2. Performance indexes of the PID controller
Index
Rising Time (s)
Settling Time (s)
Value
0.0145
2.19
Overshoot (%) 11.5
Peak Time (s) 1.12
The output of the stepper motor was the rotated angle in per second, and then it should multiple the mass of the discharged seeds in per second. The mass curve of discharged seed flow rate is illustrated in Fig. 5.
Fig. 5. Theoretical seed flow rate versus the real one.
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2.3 Experimental Research In order to assess the stability and robustness of the control system, a one-factor and five levels validating experiment should be conducted under different theoretical seed flow rates. According to (1), the levels of the theoretical seed flow rate were 2.1, 3.15, 4.2, 5.25 and 6.3 g/s, which can cover whole actual seed flow rate in practice. Every level would be replicated 5 times and the experimental time of each treatment was 5s; so the theoretical total seed masses were 10.5, 15.75, 21, 26.25 and 31.5 grams, respectively. In this study, wheat seeds whose thousand mass is 42.00 g were used as experimental materials. The shape of those seeds was elongated shape and the size of them were length 6.17± 0.33mm, width 3.28±0.35mm and thickness 2.96± 0.5mm respectively. 3. RESULTS AND DISCUSSIONS
more time, the accuracy would rise, because according to Fig. 5, after 5 seconds, the steady-state error would be less than 2%. We can see from Table 3. When theoretical total seed mass was 15.75g, the errors of the seed flow rate reach to the maximum. As the seed flow rate went up, the accuracy of the control system would increase. The average accuracy of total treatments was 89.12%. When the seed flow rate less than 6.3 g/s, the actual seed mass would less than the theoretical value; nevertheless, when the rotation speed of the seed-metering shaft was fast enough, i.e. the theoretical seed mass was up to 31.5 grams per 5 seconds, resulting in the control error decreasing to minimum. Table 3. Theoretical seed masses and actual ones in each repetition. Rn R1 Va (g)
Vt
3.1 Seed Flow Rate Calibration In order to control seed flow rate accurately, it is necessary to understand the mass of discharged seeds during a cycle of the seed-metering shaft. The stepper motor revolved 5 cycles under different rotation speeds, namely 10, 15, 20, 25, 30 rotations per minute. The seed-metering shaft was directly driven by the stepper motor via a coupling and the transmission ratio was 1:1. The experimental results are shown in Fig. 6.
205
R2
R3
R4
R5
Mean
ACY
(g)
(g)
(g)
(g)
(g)
(%)
10.5
9.17
10.28
10.81
9.03
9.79
9.82
93.52
15.75
14.69
12.81
13.17
12.56
13.49
13.35
84.76
21
20.28
18.79
17.03
18.18
18.37
18.53
88.24
26.25
23.65
22.95
21.03
21.46
22.53
22.33
85.07
31.5
30.64
29.54
30.13
28.49
30.69
29.90
94.92
Note: ACY is mean accuracy; Vt indicates the theoretical seed mass; Va represents the actual seed mass under different theoretical seed masses and repetitions; and the Rn is the number of repetitions. The actual seed mass would show an obvious linear relationship as the theoretical seed mass increases (Fig. 7). According to the statistical results (obtained by IBM SPSS Statistical 21), the coefficient of determination R 2 was 0.981. The fit equation was also calculated by SPSS software as follows: (4) M a 0.936 M t 0.870 , where Ma is the actual seed mass, g; Mt represents the theoretical seed mass. The actual seed mass increased trend and its fit equation both show in the Fig. 7.
Fig. 6. Discharged seed masses during a seed-metering shaft cycle. The results showed that the rotation speed of the seedmetering shaft was not a significant factor on mass of seeds discharged in per cycle. Thus, the average value q (12.61 g) of the discharged seed mass in per cycle was applied in the subsequent experiment. 3.2 Validating Experiment The actual seed masses versus the theoretical ones are shown in Table 3. There were 29 out of 30 of actual seed masses are less than their corresponding theoretical value. Combing with the simulation curve (Fig. 5), the control system would approach to the theoretical seed flow rate gradually after overshoot. Since the peak time, the actual seed flow rate was lower than the theoretical one. If the experiments continue 205
Fig. 7. Average of actual seed mass at each level and the fit equation between the actual masses and the theoretical ones.
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According to the Table 4, the actual seed mass does not have significant different with the theoretical values, as the value of sig. was more than 0.05. Thus, we can conclude the control system can control the seed-metering device to generate accurate seed flow rates. Table 4. Independent t-test result.
Value
F
t
df
Sig. (two sides)
0.025
-0.433
8
0.676
4. CONCLUSIONS This paper proposed a control system for a small-size seeding-performance test rig. Firstly, the hardware of the control system was designed and then the whole control model was built. Based on the mathematical model , the PID parameters were tuned by the Simulink software. Moreover, an experiment was performed to calibrate the mass of the seeds ejected in one seed-metering shaft cycle. Furthermore, a one-factor validating experiment was conducted to evaluate the accuracy of the developed control system. The results showed that the actual seed masses were slight less than the theoretical ones, but all accuracies were more than 82% and the average accuracy was 89.12%. Moreover, according to the linear regression result, it is obvious that the actual seed theoretical mass is linear as the theoretical seed flow rate went up. In addition, the fit equation illustrate that there was a strong linear relationship between the actual seed masses and the theoretical ones. Finally, an independent t-test was performed. The results showed that the significance was more than 0.05; therefore the actual seed masses were not significantly different with the theoretical ones. That is, the performance of the control system is acceptable and the small size seeding-performance test rig can be used for seed-metering device testing in laboratory. REFERENCES Deividson L.O. and Rosane F. (2014). Computers and electronics in Agriculture. Usage of the DFRobot RB-DFR49 Infrared Sensor to detect maize seed passage on a conveyor belt, 102, 106-111. Hao Jin and Huanwen Gao.(1999). Transactions of the Chinese Society for Agricultural Machinery. Virtual instrument technique and its applications in agriculture automatinon [J], 30(3), 108-112. Jian Z. Seeding-performance test rig control system and the design of its key components. Diss. 2014. Yanxia Guo, Weina Liu, Qiuxia Zhao, Na Li. (2008). Journal of Agricultural Mechanization Research. Research on microprocessing control system of precision seeding, 9, 81-83.
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