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Title:   Author  item
                                            UPADHYAYA, SHRINI - University Of Californiaitem
                                            UDOMPETAIKUL, VASU - University Of Californiaitem
                                            SHAFII, MIR - University Of Californiaitem
                                            Browne, Greg
  Submitted to: Acta Horticulturae
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 3/1/2009
                                    Publication  Date: 4/1/2009
                                    Citation: Upadhyaya, S.S., Udompetaikul, V., Shafii, M.S., Browne, G.T. 2009. Design, development and evaluation of a tree planting-site-specific fumigant applicator. Acta Horticulturae. 824:281-288.Interpretive Summary: The goal of this research was to use recent advances in the global positioning system (GPS) and computer technology to apply just the right amount of fumigant where it is most needed (i.e., tree-planting-site-specific application) to decrease the incidence of replant disease, and achieve the environmental and economical benefits of reducing the application of these toxic chemicals. In the first year of this study, we retrofitted a chemical applicator with a high-performance GPS receiver (accuracy in the range of 10 to 20 cm), an embedded controller to read GPS data and control a
solenoid valve to implement tree-planting-site-specific fumigant application. Although the system worked well, the results of accuracy tests indicated that the RMS error in position location was 33.5 cm, which was greater than desired. To improve the
position location accuracy, a new system was developed during the second year of this study. In this system, the embedded controller which was slow to perform all the necessary computations in real-time was replaced with a higher speed controller. Moreover, a pulse width control module (PWM) and solenoid actuated nozzles were
also included to provide precise application rate on demand. Extensive testing indicated that the new system had a RMS error of less than 15 cm. The system was field tested in three almond orchards in California during Fall of 2007. The system performed well in all three locations.
                                Technical Abstract: The goal of this research was to use recent advances in the global positioning system (GPS) and computer technology to apply just the right amount of fumigant where it is most needed (i.e., tree-planting-site-specific application) to decrease the incidence of replant disease, and achieve the environmental and economical benefits of reducing the application of these toxic chemicals. In the first year of this study, we retrofitted a chemical applicator with a high-performance GPS receiver (accuracy in the range of 10 to 20 cm), an embedded controller to read GPS data and control a
solenoid valve to implement tree-planting-site-specific fumigant application. Although the system worked well, the results of accuracy tests indicated that the RMS error in position location was 33.5 cm, which was greater than desired. To improve the
position location accuracy, a new system was developed during the second year of this study. In this system, the embedded controller which was slow to perform all the necessary computations in real-time was replaced with a higher speed controller. Moreover, a pulse width control module (PWM) and solenoid actuated nozzles were
also included to provide precise application rate on demand. Extensive testing indicated that the new system had a RMS error of less than 15 cm. The system was field tested in three almond orchards in California during Fall of 2007. The system performed well in all three locations.


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