Ajay Sharda

Real-Time Pressure and Flow Dynamics Due to Boom Section and Individual Nozzle Control on Agricultural Sprayers

Most modern spray controllers when coupled with a differential global positioning system (DGPS) receiver can provide automatic section or swath (boom section or nozzle) control capabilities that minimize overlap and application into undesirable areas. This technology can improve application accuracy of pesticides and fertilizers, thereby reducing the number of inputs while promoting environmental stewardship. However, dynamic system response for sprayer boom operation, which includes cycling or using auto-swath technology, has not been investigated. Therefore, a study was conducted to develop a methodology and subsequently perform experiments to evaluate tip pressure and system flow variations on a typical agricultural sprayer equipped with a controller that provided both boom section and nozzle control. To quantify flow dynamics during boom section or nozzle control, a testing protocol was established that included three simulation patterns under both flow compensation and no-compensation modes achieved via the spray controller. Overall system flow rate and nozzle tip pressure at ten boom locations were recorded and analyzed to quantify pressure and flow variations. Results indicated that the test methodology generated sufficient data to analyze nozzle tip pressure and system flow rate changes. The tip pressure for the compensated section control tests varied between 6.7% and 20.0%, which equated to an increase of 3.7% to 10.6% in tip flow rate. The pressure stabilization time when turning boom sections and nozzles off approached 25.2 s but only approached 15.6 s when turning them back on for the flow compensation tests. Although extended periods were required for the tip pressure to stabilize, the system flow rate typically stabilized in less than 7 s. The tip flow rate was consistently higher (up to 10.6%) than the target flow rate, indicating that system flow did not truly represent tip flow during section control. The no-compensation tests exhibited tip pressure increases up to 35.7% during boom and nozzle control, which equated to an 18.2% increase in tip flow. Therefore, flow compensation over no-compensation had better control of tip flow rate. A consistent difference existed in dynamic pressure response between boom section and nozzle control. Increased tip pressure and delayed pressure stabilization times indicated that application variability can occur when manually turning sections on and off or implementing auto-swath technology, but further testing is needed to better understand the effect on application accuracy of agricultural sprayers.

Development and evaluation of thermal infrared imaging system for high spatial and temporal resolution crop water stress monitoring of corn within a greenhouse

The greenhouse thermal imaging system had a ?0.62?C (α=0.05) measurement accuracy.Unstressed canopy temperatures followed closely to characteristic crop water use.Canopy temperature is a viable water stress indicator throughout growth stages.Spatial and temporal canopy temperature provide accurate crop health assessment.82% of soil moisture variation was explained by CWSI values above 0.6. Inadequate water application often decreases yield and grain quality. Existing methods using single, localized soil moisture or canopy temperature measurements do not account for crop water stress on both a high spatial and temporal resolution for precision irrigation water management decisions and scheduling. Therefore, this study was conducted to understand the feasibility of thermal cameras in order to quantify high resolution spatial canopy temperatures in relation to soil moisture. The objectives of this study were to deploy a thermal infrared imaging system (TIRIS) for high spatial and temporal monitoring of corn canopy temperature in greenhouse, test camera durability and measurement accuracy during full-season crop development, remove background temperatures with image segmentation, and sample individual plants to investigate full-season crop water stress versus soil moisture content. A TIRIS was developed using a lightweight uncooled thermal camera. Corn plants were divided into well-watered and water-stressed irrigation zones to observe stress from water deficits. Canopy temperatures were used to develop empirical canopy and air temperature deficit versus vapor pressure deficit linear regressions. Results showed that the TIRIS system maintained measurement accuracy of ?0.62?C (α=0.05) while compensating for changing ambient greenhouse conditions. Canopy and air temperature deficit versus vapor pressure deficit regression equations revealed that the predicted canopy temperature was closely related to characteristic water use. Results of the 80-day study demonstrated that 82% of soil moisture variation was explained by the crop water stress index (CWSI) values between 0.6 and 1.0. Results indicated that the CWSI derived by remotely measuring canopy temperature using TIRIS can be used as an alternate irrigation scheduling method in order to quantify spatial and temporal soil moisture variability.

Effect of emitter type and mounting configuration on spray coverage for solid set canopy delivery system

Significantly greater spray coverage on upper-side of leaves than on under-side of leaves when using SSCD system.Emitters with 80? spray cone angle provided greater coverage and penetration compared to other emitters.Configuration-4 provided uniform canopy coverage but in upper third 0.8m high canopy region.Uniform canopy coverage could be achieved by installing additional emitters in configuration-4. Timely and precise application of chemicals is critically important for improved pest control and reduced off-target movement of chemicals. A fixed or solid set canopy delivery (SSCD) system with emitters within a tree canopy has potential to reduce chemical loss and cost by applying right amount of spray at right time and location under favorable ambient conditions. The study was conducted to quantify spray coverage using various emitters mounted at different configurations within tree canopy using a SSCD system. Six different emitter (E) types with varying characteristics were selected for a field study. Each emitter was installed in four different mounting configurations. Water sensitive cards (WSCs) were mounted on upper- and under-side of leaves at 22-25 locations on each tree. After spray application, the WSCs were scanned and analyzed for percent coverage. The configuration with 80? hollow cone emitters (E6) attached to a Y-connector and mounted at height of 2.0m from the ground exhibited greater mean coverage on the WSCs placed on upper-side (58%) and under-side (21%) of leaves as compared to other emitter and configurations. It was found that coverage with this arrangement was nearly equal in upper (57.5%) and under-side (51.3%) of leaves in the high canopy region, which was the area where emitters were spraying directly. Therefore, configuration using E6 on Y-connector provided the desired uniform canopy coverage, however emitters at more locations would have to be installed to achieve similar coverage in the medium and low canopy regions.

A Case Study Concerning the Effects of Controller Response and Turning Movements on Application Rate Uniformity with a Self-Propelled Sprayer

The use of precision agriculture technologies such as automatic boom section control allows producers to reduce off-target application when applying herbicides. While automatic boom section control provides benefits, pressure differences across the spray boom resulting from boom section actuation may lead to off-rate application errors. Off-rate errors may also result from spray rate controller compensation for ground speed changes or velocity variation across the spray boom during turning movements. This project focused on characterizing application rate variation for three fields located in central Kentucky. GPS coordinates, boom control status, and nozzle pressure data (at 15 nozzle locations) were recorded as the sprayer traversed the study fields. Control section coverage areas and nozzle flow rates (calculated from the nozzle pressure with manufacturer calibration data) were used to estimate application rates. Results indicated the majority of each field received application rates at or below the target rate, as only 25% to 36% of the area in the study fields received application rates within the target rate ±10%. Spray rate controller lag time appeared to contribute to lower application rates as the sprayer accelerated and higher application rates as the sprayer decelerated as the controller attempted to compensate for changes in sprayer velocity. In addition, as boom control sections were turned off, pressure increases in the remaining sections resulted in higher application rates. Conversely, as boom sections were turned on, spray rate controller lag time may have contributed to lower application rates. Estimated application rate maps were also generated from the data to allow for a visual summary of the potential errors.

Farmers’ Adoption Path of Precision Agriculture Technology

Precision agriculture technologies have been adopted individually and in bundles. A sample of 348 Kansas Farm Management Association farm-level observations provides insight into technology adoption patterns of precision agriculture technologies. Estimated transition probabilities shed light on how adoption paths lead to bundling of technologies. Three information intensive technologies were assigned to one of eight possible bundles, and the sequence of adoption was examined using Markov transition processes. The probability that farms remain with the same bundle or transition to a different bundle by the next time period are reported. Farms with the complete bundle of all three technologies were likely to persist with their current technology.

Nozzle Uniformity for Agricultural Sprayers Operating Under Field Operation when Using Automatic Section Technology

The adoption of automatic section control technology is increasing since it reduces application overlap and application in unwanted areas leading to input savings and improved environmental stewardship. Spray controllers attempt to maintain the desired target application rate when implementing auto-section control but concerns exist about whether intended nozzle flow rates are sustained at all times. Therefore, a study was conducted to evaluate nozzle flow rate and control system response in maintaining target application rates during field operation. Specific objectives were to: 1) map real-time nozzle uniformity CV (%) during field operation and 2) quantify the difference between target and actual nozzle (% off-rate) flow rate. Field experiments were conducted using common self-propelled sprayers equipped with commercially available controller systems with automatic section control and guidance capabilities. High frequency pressure sensors were mounted across the spray boom to record nozzle pressure with data stamped with GPS locations. Nozzle pressure were converted to nozzle flow rate using manufacturers calibration curves and nozzle CV, off-rate and flow rate settling times were calculated. Results indicated that target application rate changed frequently with ASC engagement and ground speed changes on irregular field boundaries with no-spray zones. The nozzle off-rate beyond ±10% occurred for approximately 60% and nozzle uniformity CVs for 25% of the time when operating in irregular shaped fields using auto-nozzle control sprayer. Static experiments during ASC engagement and sprayer acceleration and deceleration demonstrated that nozzle off-rate can vary from -27.6% to 37.2%, thus complimenting the field results. Auto-boom and auto-nozzle control sprayers results indicated that ASC engagement plus sprayer acceleration will result in under-application whereas ASC engagement and deceleration will over-application. Nozzle flow stabilization time up to 20.0 s during ASC engagement and/or speed change was irrationally high and needs to be investigated further. Overall, irregular fields can amplify application errors though extent and magnitude may vary with selection of type of section control strategy selected (boom or nozzle control), control algorithms, and controller response.

Spatio-temporal evaluation of plant height in corn via unmanned aerial systems

Abstract. Detailed spatial and temporal data on plant growth are critical to guide crop management. Conventional methods to determine field plant traits are intensive, time-consuming, expensive, and limited to small areas. The objective of this study was to examine the integration of data collected via unmanned aerial systems (UAS) at critical corn (Zea mays L.) developmental stages for plant height and its relation to plant biomass. The main steps followed in this research were (1) workflow development for an ultrahigh resolution crop surface model (CSM) with the goal of determining plant height (CSM-estimated plant height) using data gathered from the UAS missions; (2) validation of CSM-estimated plant height with ground-truthing plant height (measured plant height); and (3) final estimation of plant biomass via integration of CSM-estimated plant height with ground-truthing stem diameter data. Results indicated a correlation between CSM-estimated plant height and ground-truthing plant height data at two weeks prior to flowering and at flowering stage, but high predictability at the later growth stage. Log–log analysis on the temporal data confirmed that these relationships are stable, presenting equal slopes for both crop stages evaluated. Concluding, data collected from low-altitude and with a low-cost sensor could be useful in estimating plant height.

Invisible leash: Object-following robot

Citation: Frink, E., Flippo, D., & Sharda, A. (2016). Invisible leash: Object-following robot. Journal of Automation, Mobile Robotics and Intelligent Systems, 10(1), 3-7. doi:10.14313/JAMRIS_1-2016/1

Impact of response characteristics of an agricultural sprayer control system on nozzle flow stabilization under simulated field scenarios

Practice of programming one VCN would not provide optimum nozzle flow response.Greater application errors for scenarios involving sprayer acceleration and deceleration.Operator behavior impacted response and application errors during speed changes.Brake point digit exhibited greater impact in reducing stabilization time.Future controllers need robust control algorithms to auto-selection of VCN. Rate controllers with automatic section control (ASC) capabilities represent sprayer technology used to not only regulate application flow rate to compensate for variations ground speed and target rate but also change in spray width. Ideally, ASC should maintain precise control to ensure uniform application, but the precision of that control is limited by the speed at which the controller can respond to variations in those conditions. The response characteristic of the controller is normally a selectable feature using a value programmed by the user, often called a valve control number (VCN). The choice of a VCN for a given spray system is a compromise between selecting a high rate of response to rapidly varying conditions and potential oscillations in output flow rate that might be induced. Both types of errors result in off-rate application. The objective of this study was to investigate the magnitude of off-rate errors caused by a range of VCN choices for simulated field conditions. Nine valve calibration numbers (VCNs) were selected for five simulated but common field operating scenarios. Simulations were conducted using a LabVIEW program to send predetermined navigation (GPS NMEA strings) and control commands to specify ground speed and boom-section actuation status to the rate controller. Variations in flow rate during simulations were measured using nozzle pressure transducers mounted across the spray boom. Results indicated manufacturer-recommended selections for the VCN (743) were not optimal and using alternate values reduced flow stabilization times in response to simulated changes in ground speed by up to one third (VCN 313). Brake point reduced nozzle flow stabilization time to a higher degree than the valve speed. The largest errors were observed when the sprayer was undergoing simulated acceleration or deceleration plus experiencing a change in nozzle actuation, emphasizing the relationship between operator driving choices and overall application errors. These results suggested using a single VCN in all operating conditions would not be appropriate. Future control strategies should consider adding the capability to adjust the rate control system characteristics (e.g. VCN) to compensate for varying operator aptitudes and field conditions.

Real-Time Pressure and Flow Response for Swath Control Technology

Auto-swath technology is being readily adopted by producers across the US because it can improve in-field equipment efficiency and reduce input usage leading to economic savings. Spray controllers with swath control use GPS to track of areas where inputs have already been applied and areas identified to receive no inputs. However, concerns exist for liquid applicators equipped with auto-swath technology about the system response when shutting ON/OFF of boom-sections or nozzles possibly impacting the desired spray pattern and rate. Therefore, an investigation was conducted to evaluate real-time boom dynamics, pressure and flow, for a typical agricultural sprayer using auto-swath technology. An 18.3-m sprayer was outfitted with commercially available individual nozzle and boom-section control was used to determine if difference existed between these different methods of ON/OFF control. Ten high frequency response pressure sensors were randomly mounted across the boom to measure nozzle tip pressure with another sensor located at the boom manifold to record overall system pressure. A flow meter just before the boom manifold provided system flow response. Two point row scenarios having 20° and 70° angles were conducted at 43.2 l/min application rate and 9.7 km/h ground speed. Auto-boom scenarios were conducted with and with-out flow compensation while auto-nozzle scenarios were conducted without flow compensation. Results indicated that 1) pressure deviation between -28% and 29% during 20° and 70° point row auto-boom scenarios resulted in the spray tip flow rate varying from -19.2% to 12.4 % during auto-boom scenarios; 2) nozzle pressure stabilization time (PST) was up to 19.3 sec. while moving OUT and INTO point rows,; 3) 20° point row presented an example of a scenario where the controller was unable to control the application rate during auto-swath initiation; and 4) the sprayer system dynamics were different for moving INTO versus OUT of point rows for all tests. These results suggest different control algorithms and possible hardware improvements are needed for these operating conditions to minimize application errors.