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Orchard tree structure digital test system and its application
Mathematical and Computer Modelling 54 (2011) 1145–1150
Contents lists available at ScienceDirect
Mathematical and Computer Modelling journal homepage: www.elsevier.com/locate/mcm
Orchard tree structure digital test system and its application Changyuan Zhai a,b , Xiu Wang a,∗ , Chunjiang Zhao a,b , Wei Zou a , Dayin Liu a , Yijin Mao a a
China National Engineering Research Centre for Information Technology in Agriculture, Beijing, 100097, PR China
b
College of Mechanical and Electronic Engineering, Northwest Agriculture and Forestry University, Yangling, 712100, PR China
article
info
Article history: Received 20 August 2010 Accepted 4 November 2010 Keywords: Digital test system Tree structure Ultrasonic sensor Serial communication
abstract Tree structure probing is a significant basic part of target precision spraying. Orchard tree structure digital test system, which consists of three components, is designed by using the ultrasonic sensors. The conveying platform is for fixing and precisely moving the sensor which is used for probing the tree profile. The lower computer can process the test data and communicate with upper computer. The upper computer can record data into Access database and show the results to the users at the same time. Utilizing the orchard tree structure digital test system, a Hawthorn tree structure is calculated. The experiment shows that probing accuracy is not less than 87%. © 2011 Published by Elsevier Ltd
1. Introduction Precision spraying plays an important role in precision agriculture. For orchard trees, target spraying is the base of precision spraying [1–3]. The existence of trees can be determined by image recognition, laser detection or infrared technologies. On the basis of tree’s position, pesticide is sprayed to the tree rather than to the gap of trees, thus reducing the environmental pollution [4,5]. But its limit in probing trees’ structure on-line leads to its shortage in accurately calculating the amount of pesticides required in different parts of the tree. Ultrasonic sensing is a technology that has the potential for non-destructive crop canopy characterization [6–8]. In fact, this technology has been introduced in the past in agricultural applications because of its advantage in high accuracy of distance measurement. In theory, the sensor, which will transmit a burst of high-frequency sound, can compute the distance based upon the speed of the sound and the elapsed time between sound transmission and echo return [9]. The objective of this research was to develop an orchard tree structure digital test system under ultrasonic sensing technology. This new system was also applied to test Hawthorn tree structure. 2. Materials and methods 2.1. Digital test system An orchard tree structure digital test system, which includes a conveying platform, lower computer and upper computer, is developed mainly by applying an ultrasonic sensor (Fig. 1). The conveying platform contains a guide, a slider and an aluminum bar. In the guide there is a step motor which can precisely move the slider along the guide. The bar is vertical to the ground, which is used to fix the sensor. The lower computer consists of a circuit board, motor driver and current voltage converter. As the core unit of the lower computer, the circuit board can not only read sensor data, process the data, and send the result to the upper computer, but
∗
Corresponding author. Tel.: +86 10 51503686; fax: +86 10 51503686. E-mail address: [email protected] (X. Wang).
0895-7177/$ – see front matter © 2011 Published by Elsevier Ltd doi:10.1016/j.mcm.2010.11.047
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C. Zhai et al. / Mathematical and Computer Modelling 54 (2011) 1145–1150
Fig. 1. Structure diagram of digital test system.
also can receive the upper computer’s command to control the motor driver. The current voltage converter is responsible for converting the current signal of ultrasonic sensor to voltage in order to be available for MCU (Micro Control Unit). The motor driver can help MCU control the step motor more easily and stably. The upper computer communicates with the lower computer through RS232 serial port. It can record data into Access database and show the results to the users at the same time. When the slider moves along the guide, the sensor can obtain the distances between the tree canopy and the sensor. The ultrasonic sensor can be fixed at different positions (Fig. 1). A series of distances from different height can be processed into Access database. According to those distances, the volume of the tree canopy can be obtained by operating the following computational process. Si =
M −
(D − dij ) · ∆l
(1)
j =1
vi = S i · h =
M − (D − dij ) · h · ∆l
(2)
j =1
V =
N − i =1
vi =
N − M − (D − dij ) · h · ∆l
(3)
i=1 j=1
where: D is the distance between the center of tree trunk and sound emitting surface of sensor in m; ∆l is sampling interval in m; M is the number of sampling to scan entire canopy; N is the number of sensor position; dij is the distance between canopy and sound emitting surface of sensor when the sensor is at position i and at sampling interval j in m; h is the distance between adjacent sensor positions in m; Si is the probing area of cross-section when the sensor is at position i in m2 ; vi is the scanning volume of canopy when the sensor is at position i in m3 ; V is the entire volume of the tree canopy in m3 . 2.2. Lower computer of test system The MCU (STC12C5A60AD) servers as the core unit of lower computer of this test system (Fig. 2). MCU1 is in charge of communication with upper computer and acquisition information. MCU2 is used to control motor driver and to move slider precisely. The ultrasonic sensor acquires distance information and exports 4–20 mA current signal. Then, the current is converted to voltage by the current voltage converter. Finally, the information is transmitted to the upper computer through the serial communication module. A battery supplies DC 24 V power for both current voltage converter and motor driver. A power circuit (Fig. 2) is designed to transform DC 24 V to DC 5 V in order to supply power for both MCUs. There are three parts in lower computer circuit (Fig. 3). A serial communication module, which serves as a converter between RS232 voltage level and TTL voltage level, is designed by a MAX232 chip. The power circuit built by LM2576 can provide a precise and stable power for the system. MCUs, namely STC12C5A60AD, which have 8 built-in AD converters, are responsible for data processing for the system. The pins of MCU2 P2.0, P2.1 and P2.2 are connected to the motor driver. The program flow charts of MCU1 and MCU2 are shown in Fig. 4. When the system’s power is switched on, MCU1 initializes system immediately, namely AD converter, serial port and CPU interrupt initialization. Then MCU1 waits for start signal from upper computer’s serial port. MCU1 will send start signal to MCU2 through pins P2.6 and P2.7 once it receives start signal from upper computer’s serial port. Then MCU1 goes into waiting status again. If there is acquisition command from MCU2’s pins P3.5 and P3.6, MCU1 will acquire sensor signal and convert it to digital signal by AD converter consequently. After computing the distance from the tree to the sensor, MCU1
C. Zhai et al. / Mathematical and Computer Modelling 54 (2011) 1145–1150
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Fig. 2. Block diagram of lower computer.
Power Circuit
Fig. 3. Circuit schematic diagram of lower computer.
sends the data to upper computer. It will continue this operation until the stop signal is received. If there is stop signal from upper computer, MCU1 will send the signal to MCU2 though pins P2.6 and P2.7. In addition, when the lower computer is on, MCU2 firstly initialize its system as well. Then it will keep waiting for start signal from MCU1. After that, MCU2 moves the sensor smoothly by driving the motor and sends acquisition command to MCU1 after moving each step (0.02 m) until the reception of stop signal from MCU1. 2.3. Upper computer of test system A software of upper computer is developed using C# language based on.Net platform. The software contains two modules to real-time record and display data respectively (Fig. 5). 2.4. Ultrasonic sensor calibration The ultrasonic sensor used in the research is Honeywell 946-A4V-2D-2C0-175E. Specifications of the ultrasonic sensor are as follows: standard detection range 2000 mm, dead zone 80 mm, beam angle ±5°, standard beam width is ±200 mm, carrier frequency 175 kHz. The sensor was calibrated with the objects of known distance. Six set of objects were selected and average of 3 readings for each set were taken with software interface of upper computer. Linear regression showed highly
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Fig. 4. Program flow chart of MCU.
Fig. 5. Software interface of upper computer.
significant relationship between actual distance and sensor A/D result (R2 = 1) (Fig. 6). The maximum of beam radius measured (Fig. 6) is 127 mm. The results indicated that ultrasonic sensors could be used for distance measurements. 2.5. Hawthorn tree experiment In order to investigate the accuracy of this digital test system, a Hawthorn tree experiment was taken by using the system. Parameters of the experiment are as follows: tree height 2.28 m, canopy bottom height 0.83 m, the distance between sensor and the center of the tree 1.724 m, guide length 2.5 m. From 0.63 to 2.43 m, sensor position was set each 0.1 m on the vertical bar of conveying platform (Fig. 1). Put the sensor at each position, the digital test system move the slider for three times. While the slider is running, the distance between the tree canopy and sensor was obtained and recorded in the Access database. The sampling interval is 0.02 m. After the probing, put a laser at each sensor position. Then move the slider 0.1 m and sleep for a while. At the sleep interval, the distance between laser spot on the tree and laser is measured manually.
C. Zhai et al. / Mathematical and Computer Modelling 54 (2011) 1145–1150
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Fig. 6. Calibration curve for the ultrasonic sensor.
Fig. 7. Probing and measurement cross-section of tree canopy (*: probing shape; o: measurement shape).
3. Results and discussion The probing and measurement cross-section of tree canopy at different heights are obtained (Fig. 7). In Fig. 7, the canopy thickness error between the probing and measurement is small. The main error positions are apparent in the beginning and end of the tree canopy, where the probing value is far greater than the measurement value. The inevitable width of beam of the ultrasonic sensor may explain this phenomenon. According to formula (1), the probing area and the measurement area of cross-section in different heights of tree canopy are calculated (Fig. 8). Fig. 8 shows that the probing area is always bigger than the measurement area, and the error between them is not large. According to formulae (2) and (3), the probing and measurement volumes of the tree canopy are calculated. The probing volume is 2.28 m3 , while the measurement volume is 2.01 m3 . The error of them is 13%, which can be accepted in target spraying according to orchard tree structure.
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Fig. 8. Probing area and measurement area of cross-section in different heights of tree canopy.
4. Conclusions (1) The orchard tree structure digital test system with high accuracy is designed reasonably, and is easy to use. (2) The experiment shows that probing accuracy is not less than 87%, which can be accepted in target spraying according to orchard tree structure. (3) The probing volume of tree canopy is larger than the actual volume, which could be corrected appropriately. Acknowledgements The study is supported by Beijing Agricultural Technology Project and China National 863 Project (2010AA10A301). References [1] Xiongkui He, Kerong Yan, Jingyu Chu, et al., Design and testing of the automatic target detecting, electrostatic, air assisted, orchard sprayer, Transactions of the CSAE 19 (6) (2003) 78–80 (in Chinese with English abstract). [2] D.L. Browna, D.K. Gilesb, M.N. Oliver, et al., Targeted spray technology to reduce pesticide in runoff from dormant orchards, Crop Protection 27 (2008) 545–552. [3] Jianjun Zou, Aijun Zeng, Xiongkui He, et al., Research and development of infrared detection system for automatic target sprayer used in orchard, Transactions of the CSAE 23 (1) (2007) 129–132 (in Chinese with English abstract). [4] Zetian Fu, Lijun Qi, Junhong. Wang, Developmental tendency and strategies of precision pesticide application techniques, Transactions of the Chinese Society for Agricultural Machinery 38 (1) (2007) 189–192 (in Chinese with English abstract). [5] Wei DENG, Xiong-kui HE, Lu-da ZHANG, et al., Target infrared detection in target spray, Spectroscopy and Spectral Analysis 28 (10) (2008) 2285–2289 (in Chinese with English abstract). [6] F. Solanelles, S. Planas, A. Escola, et al., Spray application efficiency of an electronic control system for proportional application to the canopy volume, Aspects of Applied Biology 66 (2002) 139–146. [7] Q.U. Zaman, M. Salyani, Effects of foliage density and ground speed on ultrasonic measurement of citrus tree volume, Applied Engineering in Agriculture 20 (2) (2004) 173–178. [8] A.W. Schumann, Q.U. Zaman, Software development for real-time ultrasonic mapping of tree canopy size, Computers and Electronics in Agriculture 47 (2005) 25–40. [9] S. Ciarcia, An ultrasonic ranging system, BYTE 9 (11) (1984) 112–123.
Contents lists available at ScienceDirect
Mathematical and Computer Modelling journal homepage: www.elsevier.com/locate/mcm
Orchard tree structure digital test system and its application Changyuan Zhai a,b , Xiu Wang a,∗ , Chunjiang Zhao a,b , Wei Zou a , Dayin Liu a , Yijin Mao a a
China National Engineering Research Centre for Information Technology in Agriculture, Beijing, 100097, PR China
b
College of Mechanical and Electronic Engineering, Northwest Agriculture and Forestry University, Yangling, 712100, PR China
article
info
Article history: Received 20 August 2010 Accepted 4 November 2010 Keywords: Digital test system Tree structure Ultrasonic sensor Serial communication
abstract Tree structure probing is a significant basic part of target precision spraying. Orchard tree structure digital test system, which consists of three components, is designed by using the ultrasonic sensors. The conveying platform is for fixing and precisely moving the sensor which is used for probing the tree profile. The lower computer can process the test data and communicate with upper computer. The upper computer can record data into Access database and show the results to the users at the same time. Utilizing the orchard tree structure digital test system, a Hawthorn tree structure is calculated. The experiment shows that probing accuracy is not less than 87%. © 2011 Published by Elsevier Ltd
1. Introduction Precision spraying plays an important role in precision agriculture. For orchard trees, target spraying is the base of precision spraying [1–3]. The existence of trees can be determined by image recognition, laser detection or infrared technologies. On the basis of tree’s position, pesticide is sprayed to the tree rather than to the gap of trees, thus reducing the environmental pollution [4,5]. But its limit in probing trees’ structure on-line leads to its shortage in accurately calculating the amount of pesticides required in different parts of the tree. Ultrasonic sensing is a technology that has the potential for non-destructive crop canopy characterization [6–8]. In fact, this technology has been introduced in the past in agricultural applications because of its advantage in high accuracy of distance measurement. In theory, the sensor, which will transmit a burst of high-frequency sound, can compute the distance based upon the speed of the sound and the elapsed time between sound transmission and echo return [9]. The objective of this research was to develop an orchard tree structure digital test system under ultrasonic sensing technology. This new system was also applied to test Hawthorn tree structure. 2. Materials and methods 2.1. Digital test system An orchard tree structure digital test system, which includes a conveying platform, lower computer and upper computer, is developed mainly by applying an ultrasonic sensor (Fig. 1). The conveying platform contains a guide, a slider and an aluminum bar. In the guide there is a step motor which can precisely move the slider along the guide. The bar is vertical to the ground, which is used to fix the sensor. The lower computer consists of a circuit board, motor driver and current voltage converter. As the core unit of the lower computer, the circuit board can not only read sensor data, process the data, and send the result to the upper computer, but
∗
Corresponding author. Tel.: +86 10 51503686; fax: +86 10 51503686. E-mail address: [email protected] (X. Wang).
0895-7177/$ – see front matter © 2011 Published by Elsevier Ltd doi:10.1016/j.mcm.2010.11.047
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C. Zhai et al. / Mathematical and Computer Modelling 54 (2011) 1145–1150
Fig. 1. Structure diagram of digital test system.
also can receive the upper computer’s command to control the motor driver. The current voltage converter is responsible for converting the current signal of ultrasonic sensor to voltage in order to be available for MCU (Micro Control Unit). The motor driver can help MCU control the step motor more easily and stably. The upper computer communicates with the lower computer through RS232 serial port. It can record data into Access database and show the results to the users at the same time. When the slider moves along the guide, the sensor can obtain the distances between the tree canopy and the sensor. The ultrasonic sensor can be fixed at different positions (Fig. 1). A series of distances from different height can be processed into Access database. According to those distances, the volume of the tree canopy can be obtained by operating the following computational process. Si =
M −
(D − dij ) · ∆l
(1)
j =1
vi = S i · h =
M − (D − dij ) · h · ∆l
(2)
j =1
V =
N − i =1
vi =
N − M − (D − dij ) · h · ∆l
(3)
i=1 j=1
where: D is the distance between the center of tree trunk and sound emitting surface of sensor in m; ∆l is sampling interval in m; M is the number of sampling to scan entire canopy; N is the number of sensor position; dij is the distance between canopy and sound emitting surface of sensor when the sensor is at position i and at sampling interval j in m; h is the distance between adjacent sensor positions in m; Si is the probing area of cross-section when the sensor is at position i in m2 ; vi is the scanning volume of canopy when the sensor is at position i in m3 ; V is the entire volume of the tree canopy in m3 . 2.2. Lower computer of test system The MCU (STC12C5A60AD) servers as the core unit of lower computer of this test system (Fig. 2). MCU1 is in charge of communication with upper computer and acquisition information. MCU2 is used to control motor driver and to move slider precisely. The ultrasonic sensor acquires distance information and exports 4–20 mA current signal. Then, the current is converted to voltage by the current voltage converter. Finally, the information is transmitted to the upper computer through the serial communication module. A battery supplies DC 24 V power for both current voltage converter and motor driver. A power circuit (Fig. 2) is designed to transform DC 24 V to DC 5 V in order to supply power for both MCUs. There are three parts in lower computer circuit (Fig. 3). A serial communication module, which serves as a converter between RS232 voltage level and TTL voltage level, is designed by a MAX232 chip. The power circuit built by LM2576 can provide a precise and stable power for the system. MCUs, namely STC12C5A60AD, which have 8 built-in AD converters, are responsible for data processing for the system. The pins of MCU2 P2.0, P2.1 and P2.2 are connected to the motor driver. The program flow charts of MCU1 and MCU2 are shown in Fig. 4. When the system’s power is switched on, MCU1 initializes system immediately, namely AD converter, serial port and CPU interrupt initialization. Then MCU1 waits for start signal from upper computer’s serial port. MCU1 will send start signal to MCU2 through pins P2.6 and P2.7 once it receives start signal from upper computer’s serial port. Then MCU1 goes into waiting status again. If there is acquisition command from MCU2’s pins P3.5 and P3.6, MCU1 will acquire sensor signal and convert it to digital signal by AD converter consequently. After computing the distance from the tree to the sensor, MCU1
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Fig. 2. Block diagram of lower computer.
Power Circuit
Fig. 3. Circuit schematic diagram of lower computer.
sends the data to upper computer. It will continue this operation until the stop signal is received. If there is stop signal from upper computer, MCU1 will send the signal to MCU2 though pins P2.6 and P2.7. In addition, when the lower computer is on, MCU2 firstly initialize its system as well. Then it will keep waiting for start signal from MCU1. After that, MCU2 moves the sensor smoothly by driving the motor and sends acquisition command to MCU1 after moving each step (0.02 m) until the reception of stop signal from MCU1. 2.3. Upper computer of test system A software of upper computer is developed using C# language based on.Net platform. The software contains two modules to real-time record and display data respectively (Fig. 5). 2.4. Ultrasonic sensor calibration The ultrasonic sensor used in the research is Honeywell 946-A4V-2D-2C0-175E. Specifications of the ultrasonic sensor are as follows: standard detection range 2000 mm, dead zone 80 mm, beam angle ±5°, standard beam width is ±200 mm, carrier frequency 175 kHz. The sensor was calibrated with the objects of known distance. Six set of objects were selected and average of 3 readings for each set were taken with software interface of upper computer. Linear regression showed highly
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C. Zhai et al. / Mathematical and Computer Modelling 54 (2011) 1145–1150
Fig. 4. Program flow chart of MCU.
Fig. 5. Software interface of upper computer.
significant relationship between actual distance and sensor A/D result (R2 = 1) (Fig. 6). The maximum of beam radius measured (Fig. 6) is 127 mm. The results indicated that ultrasonic sensors could be used for distance measurements. 2.5. Hawthorn tree experiment In order to investigate the accuracy of this digital test system, a Hawthorn tree experiment was taken by using the system. Parameters of the experiment are as follows: tree height 2.28 m, canopy bottom height 0.83 m, the distance between sensor and the center of the tree 1.724 m, guide length 2.5 m. From 0.63 to 2.43 m, sensor position was set each 0.1 m on the vertical bar of conveying platform (Fig. 1). Put the sensor at each position, the digital test system move the slider for three times. While the slider is running, the distance between the tree canopy and sensor was obtained and recorded in the Access database. The sampling interval is 0.02 m. After the probing, put a laser at each sensor position. Then move the slider 0.1 m and sleep for a while. At the sleep interval, the distance between laser spot on the tree and laser is measured manually.
C. Zhai et al. / Mathematical and Computer Modelling 54 (2011) 1145–1150
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Fig. 6. Calibration curve for the ultrasonic sensor.
Fig. 7. Probing and measurement cross-section of tree canopy (*: probing shape; o: measurement shape).
3. Results and discussion The probing and measurement cross-section of tree canopy at different heights are obtained (Fig. 7). In Fig. 7, the canopy thickness error between the probing and measurement is small. The main error positions are apparent in the beginning and end of the tree canopy, where the probing value is far greater than the measurement value. The inevitable width of beam of the ultrasonic sensor may explain this phenomenon. According to formula (1), the probing area and the measurement area of cross-section in different heights of tree canopy are calculated (Fig. 8). Fig. 8 shows that the probing area is always bigger than the measurement area, and the error between them is not large. According to formulae (2) and (3), the probing and measurement volumes of the tree canopy are calculated. The probing volume is 2.28 m3 , while the measurement volume is 2.01 m3 . The error of them is 13%, which can be accepted in target spraying according to orchard tree structure.
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C. Zhai et al. / Mathematical and Computer Modelling 54 (2011) 1145–1150
Fig. 8. Probing area and measurement area of cross-section in different heights of tree canopy.
4. Conclusions (1) The orchard tree structure digital test system with high accuracy is designed reasonably, and is easy to use. (2) The experiment shows that probing accuracy is not less than 87%, which can be accepted in target spraying according to orchard tree structure. (3) The probing volume of tree canopy is larger than the actual volume, which could be corrected appropriately. Acknowledgements The study is supported by Beijing Agricultural Technology Project and China National 863 Project (2010AA10A301). References [1] Xiongkui He, Kerong Yan, Jingyu Chu, et al., Design and testing of the automatic target detecting, electrostatic, air assisted, orchard sprayer, Transactions of the CSAE 19 (6) (2003) 78–80 (in Chinese with English abstract). [2] D.L. Browna, D.K. Gilesb, M.N. Oliver, et al., Targeted spray technology to reduce pesticide in runoff from dormant orchards, Crop Protection 27 (2008) 545–552. [3] Jianjun Zou, Aijun Zeng, Xiongkui He, et al., Research and development of infrared detection system for automatic target sprayer used in orchard, Transactions of the CSAE 23 (1) (2007) 129–132 (in Chinese with English abstract). [4] Zetian Fu, Lijun Qi, Junhong. Wang, Developmental tendency and strategies of precision pesticide application techniques, Transactions of the Chinese Society for Agricultural Machinery 38 (1) (2007) 189–192 (in Chinese with English abstract). [5] Wei DENG, Xiong-kui HE, Lu-da ZHANG, et al., Target infrared detection in target spray, Spectroscopy and Spectral Analysis 28 (10) (2008) 2285–2289 (in Chinese with English abstract). [6] F. Solanelles, S. Planas, A. Escola, et al., Spray application efficiency of an electronic control system for proportional application to the canopy volume, Aspects of Applied Biology 66 (2002) 139–146. [7] Q.U. Zaman, M. Salyani, Effects of foliage density and ground speed on ultrasonic measurement of citrus tree volume, Applied Engineering in Agriculture 20 (2) (2004) 173–178. [8] A.W. Schumann, Q.U. Zaman, Software development for real-time ultrasonic mapping of tree canopy size, Computers and Electronics in Agriculture 47 (2005) 25–40. [9] S. Ciarcia, An ultrasonic ranging system, BYTE 9 (11) (1984) 112–123.