Automatic Control of Chemical Application Rate With Soil Organic Matter and Travel Speed as Inputs (Microprocessor, Digital Control)
Han, Young Jo
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Permalink
https://hdl.handle.net/2142/70959
Description
Title
Automatic Control of Chemical Application Rate With Soil Organic Matter and Travel Speed as Inputs (Microprocessor, Digital Control)
Author(s)
Han, Young Jo
Issue Date
1986
Department of Study
Agricultural Engineering
Discipline
Agricultural Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Agricultural
Abstract
Effective and efficient control of agricultural chemical application rate will allow a reduction in the use of pesticides for proper pest control with less environmental contamination. A microprocessor based sprayer control system was developed to regulate chemical application rate according to the soil organic matter content and sprayer ground speed. Bypass nozzles were used to maintain uniform spray characteristics over a wide range of flow rates. The application rate was controlled by regulating the pressure of the bypass line with a pressure relief valve controlled by a step motor. The major functions of the controller were to monitor the soil organic matter content and sprayer ground speed, to determine the desired application rate, and to regulate the pressure relief valve to control the nozzle flow rate. The control system also recognized abnormal operating parameters and gave appropriate warning signals.
Two types of control systems, a flow sensing system and a pressure sensing system were designed and evaluated. The flow sensing system constantly monitored the actual nozzle flow rate, thus virtually eliminating the steady-state error due to non-ideal characteristics of the system. The pressure sensing system was designed to eliminate the need of flow meters in the control system. It monitored the bypass pressure instead of the actual nozzle flow rate, and estimated the nozzle flow rate using a relationship between bypass pressure and nozzle flow rate.
The steady-state and transient responses to various excitation signals were obtained to evaluate the system stability and performance. The control system was stable with less than 5 percent of steady-state error while achieving a turn down ratio of 5:1 with the bypass nozzles used. The numerical simulation results showed that the performance of the control system was dependent on the quantization characteristics of the nozzle flow rate due to the step motor used.
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