Development and Preliminary Evaluation of a Variable Rate Spraying System

Abstract

A variable rate chemical application system based on prescription maps from an ccompanying expert decision system was developed to accommodate in-field spatial variability of paddy fields in Taiwan. A flow-based spraying system using a TASC 6200 console by Mid-Tech®, Inc. was used as the main frame to perform the general automated spraying functions. Preliminary evaluation of the variable rate spraying system was performed by testing Differential Global Positioning Systems (DGPS) receiver static and dynamic signal responses, sprayer flow, and nozzle flow/boom patterns. Main conclusions drawn from this study were stated as follows. With an average static error of approximately 1.6 meters and an average 2-Distance RMS of approximately 2.3 meters, the used RX-400p receiver is accurate enough for navigation, but not sufficient for field work. The trend obtained from dynamic accuracy test does not coincide with that from other researchers. However, the velocity data from the DGPS receiver may be used for providing speed information of the sprayer. The re-verification experiments showed that the tested DGPS receiver moving with a traveling speed varied from 0.2 to 1 m/s behaved almost the same in both longitude and latitude with an average dynamic position error of 2.23 m. The averaged offset time for the tested DGPS receiver moving with a traveling speed varied from 0.4 to 1 m/s was found to be 3.48 seconds. The higher the application rate and traveling speed, the larger the sprayer flow error. Both calibration numbers, 153.1 and 155, with minimal sprayer flow error can be used for calibrating the used flow meter without significant difference. The nozzle flow/boom patterns of four nozzle types with CVs less than 5% were very uniform. The data collected provided valuable information for improving and implementing variable rate application suitable for Taiwan's situations. 一組以專家決策系統事先編製地圖為基礎之變率施噴系統被研發以適應台灣稻田之空間變異，使用Mid-Tech公司TASC 6200主控器之流量控制噴霧系統當主要架構，以執行一般的自動噴霧功能。變率施噴系統之初期評估測試了差分全球定位系統(DGPS)接收器之靜態與動態訊號反應、噴藥機施噴流量及噴嘴流量／噴桿樣式。本研究主要結果如下：具有平均靜態誤差大約1.6m與平均2DRMS值大約2.3m，此差分全球定位系統RX-400p接收器之準確度足以用於導航，但尚不足以適用於田間工作。動態準確度測試所得之趨勢與其他的研究者獲致之結果有差異，不過差分全球定位系統的速率資料可用以提供噴霧機速度資訊。此差分全球定位接收器在行進速度0.2至1m/s時，於經緯度方向表現一致而具有平均動態位置誤差2.23m，而在行進速度0.4至1m/s時其平均偏差時間為3.48秒。較高的施噴率及行進速度會導致較高的噴霧機流量誤差，校正係數153.1及155可用以校正流量計而無明顯之差異。四種噴嘴型式之噴嘴流量／噴桿樣式由於變異係數值皆小於5%顯然相當一致，本研究所收集之資料對改良及運用適於台灣情況之變率施噴機具提供極有價值的資訊。