J. B. Wilkerson

MULTI-SPECTRAL SENSOR FOR DETECTION OF NITROGEN STATUS IN COTTON

Based on the spectral characteristics of cotton canopies, a plant nitrogen sensor was designed and fabricated for detection of nitrogen status in cotton plants. The sensor is an active optical multi-spectral sensing unit. It measures spectral reflectance from a cotton canopy in blue, green, red, and near infrared wavebands with a modulated illumination to the cotton canopy. The sensor was tested in the laboratory and field, and promising results were obtained. This article describes the design, implementation, and testing of the sensor.

A microcomputer-based morphometer for bush-type plants☆

Abstract A microcomputer-based measurement system was developed to allow in-situ, non-destructive measurement of the morphological characteristics of bush-type plants. Seven ultrasonic ranging modules were used to scan the plant row for distance-to-plant measurements at three different positions on each side of the row and one position above the row. An optical incremental shaft encoder was used as a position sensor to measure the forward travel distance of the instrument. The selected horizontal interval between successive scans was 31 mm. An interface was designed to connect a single-board computer (SBC) with the ultrasonic sensor system for data acquisition. Storage capacity of this measurement system was 7000 data values (1000 scans of seven sensors). A key pad was interfaced with the SBC to permit input of the operating commands. A liquid crystal display (LCD) unit displayed all results, including cumulative plant volume, maximum and average plant widths at three vertical positions, and maximum and average plant heights. In both laboratory and field tests, the device produced results which were consistent and in close agreement with physical measurements taken in other ways.

Detecting Insect Flight Sounds in the Field: Implications for Acoustical Counting of Mosquitoes

A prototype field-deployable acoustic insect flight detector was constructed from a noise-canceling microphone coupled to an off-the-shelf digital sound recorder capable of 10 h recordings. The system was placed in an urban forest setting 25 times over the course of the summer of 2004, collecting 250 h of ambient sound recordings that were downloaded to a personal computer and used to develop detection routines. These detection routines operated on short segments of sound (0.093 s, corresponding to 4096 samples at 44100 Hz). A variety of approaches were implemented to detect insect flight tones. Simple approaches, involving sensing the fundamental frequency (1st harmonic) and 2nd harmonic, were capable of detecting insects, but generated large numbers of false positives because of other ambient sounds including human voices, birds, frogs, automobiles, aircraft, sirens, and trains. In contrast, combining information from the first four harmonics, from the interharmonic regions, and from the sound envelope, reduced false positives greatly. Specifically, in the 250 h of recordings, 726 clear insect buzzes were detected by the final algorithm, with only 52 false positives (6.5%). Running the final algorithm with all criteria liberalized by 20% increased the number of clear insect buzzes by 8%, to 784, but increased false positives to 471 (28% of total detections). The potential of using this approach for detecting mosquito activity using low-cost sensors is discussed.

Comparison of Tractor Ground Speed Measurement Techniques

ABSTRACT PERFORMANCES of fifth wheel, front wheel, and single-beam radar vehicle ground speed sensors were evaluated on an agricultural tractor at operating speeds of 4, 7 and 10 km/h. Surface conditions included a smooth, non-deformable surface, soils subjected to various levels of tillage, and a range of vegetative covers. Based upon calibration values obtained for each sensor during tractor operation over the smooth, non-deformable surface, radar generally produced more accurate indications of true ground speeds than sensors with ground-contacting wheels. Coefficients of variation in indicated ground speed over time were also generally less for the radar unit than for either fifth wheel or front wheel units. The magnitude of the slip between the ground-contacting wheels and the tractive surface varied inversely with surface firmness. Thus, speed sensors having ground-contacting wheels should be calibrated for the specific surface conditions over which vehicle velocity measurement is to be obtained.

DESIGN AND EVALUATION OF AN IMPROVED FLOW DIVIDER FOR SAMPLING RUNOFF PLOTS

An improved flow divider was designed to simplify and lower the cost of collecting runoff data from research plots. The system was designed around commercially available and inexpensive 5-gal (19-L) plastic buckets with screw top lids. A precision cut sheet-metal divider “crown” is fastened to the lid, allowing it to be easily transferred between buckets. The divider crown can be configured to handle various flow rates by specifying the number of flow divisions. Laboratory evaluation of the design indicated that the system divides runoff with accuracies within .5% over most of the flow range and within .15% at very low and very high flows. These results are similar to those found for the more traditional flow divider designs. Adding sediment to the inflow at three different flow rates yielded sediment division accuracies within 7%. Five field research projects have used the divider system with few problems. The average cost of this system is approximately US

SPRAYER BOOM INSTRUMENTATION FOR FIELD USE

500 per plot, in comparison to the US

DESIGN AND EVALUATION OF A COTTON FLOW RATE SENSOR

3000 to

SOILWATER SENSOR PERFORMANCE

5000 it often costs to instrument a plot using standard equipment.

Evaluating Planter Performance--Cotton Seed Placement Accuracy

Sprayer on-board instrumentation was developed to measure vibration inputs to the boom, boom acceleration response, boom end height response, and sprayer position along a field track with an aim of relating boom dynamics to field spray deposits. Vibration responses included tires, chassis suspension, boom suspension, and any flexure in components (including boom). Twelve accelerometers measured responses in longitudinal (x), vertical (y), and transverse (z) directions at the chassis center rear, boom center, and at each boom end. Accelerometer rating of ±10 g with a manufacturer-rated accuracy of 1% produced satisfactory system responses. An ultrasonic distance sensor operated satisfactorily as a boom height sensor over mown grass with an accuracy of ±0.03 m. A photoelectric-based position-along-track sensor operated satisfactorily with a 23 cm wide target to block the beam with an accuracy of ±6 cm. This position sensor was developed to assist in locating the sprayer and boom dynamics relative to spray deposit samplers in a follow-on study. A PC-based data acquisition system polled sensors at 2.5 kHz. Signal noise was reduced using bandpass (0.1 to 15 Hz) software filtering. Y-accelerations at the boom center ranged from 1.5 to -0.8 g. Response frequencies of the sprayer vehicle and boom ranged from 4 to 7 Hz in x, y, and z directions on a smooth track. A 20 cm track bump resulted in sprayer and boom response frequencies of 1 to 2 Hz in the y direction and 5 to 6 Hz in x and z directions. The bump increased the peak acceleration power up to a factor of 19 for the y direction at both boom ends compared with a smooth track. A 20 cm dip and an opposing 20 cm bump in the sprayer track had an insignificant effect in shifting primary response frequencies in the y direction. However, the dip/bump reduced the response frequency (<5 Hz) in the x and z directions at the boom center. A one-half sprayer tank load of water (1514 L) dampened vehicle vibration so that the water load changed the main response frequency (<4.5 Hz) and reduced power levels (~55%) in the y direction at the boom center. The developed instrumentation system may be useful in the design of future sprayers and spray booms and assist decisions on sprayer suspensions and operating speeds, boom design length, and use of active boom suspensions.

Implementation and Field Evaluation of a Cotton Yield Monitor

An optically–based system for measuring cotton flow rate was designed and tested in both field and laboratory environments. Accuracy was documented by comparing actual and predicted load weights. When field–tested on a cotton harvester, results were positive, with an average absolute error of 4.7%. A laboratory test was subsequently designed and conducted to gather data describing relationships between system performance and variables such as cotton flow rate, cotton moisture content, and cotton variety. The accuracy results of the laboratory test confirmed those generated in the field, with an average absolute error of 3.4%. Additionally, laboratory test results indicated a moderate correlation between average flow rate and absolute error. Variety also affected system performance, with an average absolute error of 2.4% for one variety, versus 4.9% for another. Moisture content had no detectable effect on accuracy in the laboratory test. The technology described herein has been patented and licensed to industry for application on mobile equipment.