1. Progress on Field Evaluation of Aerial Variable- Rate Systems for Liquid Application Steven J. Thomson Steve.Thomson@ars.usda.gov Yanbo Huang Yanbo.huang@ars.usda.gov Research Agricultural Engineers USDA-ARS-MSA-CPSRU Stoneville, MS USA 38776

2. It takesto make it all workbriansbrains

3. Progress Flow control testing Flow control testing –L.A. Smith: 1997-2001 Tested the AutoCal I and II for its ability to keep a constant amount/acre Tested the AutoCal I and II for its ability to keep a constant amount/acre Variable-rate flow control Variable-rate flow control –Smith and Thomson: 2004-2005 Tested and refined the Satloc/AutoCal II combination for its variable-rate capabilities Tested and refined the Satloc/AutoCal II combination for its variable-rate capabilities –Thomson, Huang, Martin: 2007 - present Refined the flow controllers response to changing rates Refined the flow controllers response to changing rates

4. GPS-based guidance systems Assist pilot in locating areas to apply for manually operated flow control Assist pilot in locating areas to apply for manually operated flow control Are essential components of automatic (on-off or variable rate) flow control systems Are essential components of automatic (on-off or variable rate) flow control systems

5. GPS-based guidance systems Ag-Nav (Guía, FireNav, FlightMaster TM) Ag-Nav (Guía, FireNav, FlightMaster TM) Hemisphere GPS Hemisphere GPS –Satloc –Del Norte Adapco Wingman GX Adapco Wingman GX DynaNav Dynaflight DynaNav Dynaflight Trimble AgGPS ® Trimflight 3 Trimble AgGPS ® Trimflight 3

6. GPS-based guidance system Flow Turbine Meter Flow Controller Flow Adjustment consists of… Ground Speed Chemical Pump on Aircraft Pulse output 1.Electric servo on variable-pitch fan (prop) on spray pump or 2.Electrically operated servo valve and hydraulically operated pump or 3.Electrical in-line valve adjustment Spray Valve adjust Integrated Aerial Flow Control For VR, georeferencing

7. CPSRU Variable-Rate System Air Tractor 402B spray plane equipped with an engine-driven hydraulic power package (Kawak Aviation Technologies) Air Tractor 402B spray plane equipped with an engine-driven hydraulic power package (Kawak Aviation Technologies) Satloc M3 with WAAS DGPS and 5 Hz position updating. Uses AirTrac VR software (Hemisphere GPS) Satloc M3 with WAAS DGPS and 5 Hz position updating. Uses AirTrac VR software (Hemisphere GPS) AutoCal II automatic flow control (Houma Avionics, Houma, LA) AutoCal II automatic flow control (Houma Avionics, Houma, LA) Hydraulically powered chemical pump and boom valve Hydraulically powered chemical pump and boom valve

8. Hydraulically controlled pump

9. Houma Avionics AutoCal II Compatible with most guidance systems Compatible with most guidance systems Interfaces with hydraulic Interfaces with hydraulic (e.g. Kawak) flow control systems Interfaces with electric valve motors and variable-pitch pump props (with additional servo) Interfaces with electric valve motors and variable-pitch pump props (with additional servo) Has been tested by USDA-ARS-CPSRU (Stoneville) for application and placement accuracy Has been tested by USDA-ARS-CPSRU (Stoneville) for application and placement accuracy

10. Flow Control Evaluation How does the variable-rate system perform?

11. System was evaluated with respect to: –Position error of spray deposits relative to management zone boundaries –System response time –Application accuracy

12. Test Area 32 acre field (1660 x 900 ft) land formed and seeded to Bermuda grass 32 acre field (1660 x 900 ft) land formed and seeded to Bermuda grass Management zone boundaries were located using an RTK GPS system with centimeter level accuracy Management zone boundaries were located using an RTK GPS system with centimeter level accuracy

13. 0 gpa 4 gpa 3 gpa 5 gpa 6 gpa 265 ft 531 ft 354 ft Boundaries georeferenced with RTK GPS receiver

16. Used west lane of prescription test area Used west lane of prescription test area Captured data stream generated by AutoCal II Captured data stream generated by AutoCal II Captured flow meter data with a 0.1s monitor designed to read the flow meter at regular intervals Captured flow meter data with a 0.1s monitor designed to read the flow meter at regular intervals

18. First Tests for Variable-Rate (2005): Evaluate AutoCal II response to changing rates First needed to initiate flow 0.5 s early L. A Smith - Steve, your estimate is 0.05 seconds from optimal !

21. Results – Flow Control Error Pass Actual (gal) Required (gal) Average Error (%) 16.636.570.83 26.015.901.87 36.396.232.57 46.146.19-0.84 56.496.421.10 66.486.450.40 |Average|1.08

22. -- Spray Deposit -- No Spray W10W10 W9W9 W8W8 W7W7 W6W6 W5W5 W4W4 W3W3 W2W2 W1W1 RCBRCB E1E1 E2E2 E3E3 E4E4 E5E5 E6E6 E7E7 E8E8 E9E9 E10E10 Results - Spray Deposits 6 gpa 0 gpa

23. Flow controller response to rate changes resulted in average application volume error (not including sign) of 1.08% Flow controller response to rate changes resulted in average application volume error (not including sign) of 1.08% Spray deposit position error from ten runs over water sensitive cards, ranged from -6 m to 16 m and 80% of the error magnitudes were 6 m or less. Spray deposit position error from ten runs over water sensitive cards, ranged from -6 m to 16 m and 80% of the error magnitudes were 6 m or less. Summary of 2005 results:

24. For research purposes (2005), a high resolution (0.1s) flow monitor was used to read the flowmeter directly. Although it can be constructed, flow monitor is not readily available to users. So, we can look at response without flow monitor Thoughts on Further Testing: (2008-2009)

25. 2005 response with flow monitor to increase data resolution

26. 2005 response (raw)

27. In 2008, experiments were conducted and system was modified to further improve response to changing rates

28. 2008 response – before program modification

29. 2008 response – after program modification

30. New setup to test multiple guidance systems/flow controllers

31. Old Setup

33. Installed by Air Repair – Cleveland, MS

34. Autocal II flow control readout Satloc Ag-Nav Guia

35. Observation – what is necessary for aerial VR to be successful : Droplet spectra must maintain consistency at different flowrates and pressures still

36. Can use mixed nozzle tip sizes to extend operating range (CP) Can use mixed nozzle tip sizes to extend operating range (CP) Rotary atomizers – Do they maintain similar spectra at different working pressures? Rotary atomizers – Do they maintain similar spectra at different working pressures? Fixed nozzles – New designs are needed Fixed nozzles – New designs are needed

39. Thank you!