Browsing by Author "Miller, W. M."
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Item Evaluation of a variable rate controller for aldicarb application around buffer zones in citrus groves(2007-01-25) Tumbo, S. D.; Miller, W. M.; Salyani, M.; Sweeb, R.; Buchanon, S.Advances in precision farming technologies have facilitated controlled application of agrochemicals and documentation procedures to follow environmental regulations. This paper details evaluation of a commercial variable rate (VR) controller for preventing aldicarb applications in the buffer zones around potablewater wells of citrus groves. The controllerwas coupled to two common drive mechanisms, a ground-driven electric clutch-engaged (GDEC) and pulse-width-modulation motor-driven (PWMM). The evaluation involved determination of dynamic performance of the VR application system through quantification of reaction times and rate transition distances and determination of appropriate “look-ahead” times for each of the drive mechanisms. Without a look-ahead (zero) setting, the mean midpoint reaction distances were about 1.8 and 3.6m for the GDEC and PWMM mechanisms, respectively, at 7.0-km/h ground speed. For the GDEC, a look-ahead time of 1 s gave the mean midpoint reaction distances of −0.06 and 0.04m during step-up and step-down of the rate, respectively. For PWMM, the best look-ahead times were 1 and 2 s during step-up and step-down of the rate, respectively.However, since the prototype unit could not accommodate two look-ahead times, the compromise look-ahead time for both step-up and -down was 2 s. Validation in the actual buffer zone showed that, at 95% confidence level, the buffer zone should be increased by 2.5 or 3.3m in commercial applications using GDEC or PWMM systems, respectively.Item Investigation of laser and ultrasonic ranging sensors for measurements of citrus canopy volume(American Society of Agricultural Engineers, 2002) Tumbo, S. D.; Salyani, M.; Whitney, J. D.; Wheaton, T. A.; Miller, W. M.This study compared ultrasonic and laser measurements of citrus canopy volume with manual measurement methods. Fifteen trees with different canopy heights and volumes were used. Manual and ultrasonic measurements provided dimensions for computing the canopy volume whereas laser measurements gave information that could be used to compute a ‘laser canopy volume index.’ Ultrasonic and laser methods agreed with manual methods (R2 > 0.85, RMSE < 2.15 m3). Laser showed better prediction of canopy volume than the ultrasonic system because of the higher resolution. Ultrasonic or laser sensors can be used for automatic mapping and quantification of the canopy volumes of citrus trees.