Document
Results of NASA/DARPA Automatic Probe and Drogue
Refueling Flight Test
Keith Schweikhard NASA Dryden Flight Research Center 661-276-3411 keith.a.schweikhard@nasa.gov
Program Objective
Phase I Objectives: (1 May 2005 - 30 August 2006)
To make one demonstration fully automatic
engagement (probe plugging the drogue) between
the F-18 and the Omega Air B707 tanker using the
Autonomous Airborne Refueling System.
Phase II Objectives: (October 2006 - April 2007)
● Optimal Tuning of AARD Controller
● Evaluate plug performance in a turn
● Autonomous Rendezvous with the tanker
● Improve Video Tracker Performance
Technical Background
➢ High Risk Technology
➢ Technology Demonstration not Development Program
➢ Low Cost
➢ Compressed Development Schedule
➢ Reduced number of test conditions
➢ Reduced redundancy/ error correction in the system.
Project Timeline
➢ March 05 Proposal Kickoff Meeting @ DFRC
➢ 05-05-05 and 05-18-05 Kickoff Meetings
➢ 07-12-05 System Requirements Review
➢ 08-30-05 Preliminary Design Review
➢ 10-19-05 Critical Design Review
➢ 10-24-06 Risk Reduction Flight
➢ 03-02-06 Hardware Arrives at Dryden
➢ 04-04-06 Flight Readiness Review
➢ 05-18-06 Airworthiness and Flight Safety Review Board
➢ 06-12-06 Tech Brief (Surrogate Tanker)
➢ 06-16-06 through 06-29-06 Surrogate Tanker Flights
➢ 07-06-06 Tech Brief (Omega Tanker)
➢ 07-11-06 through 08-30-06 Omega Tanker Flights
➢ 10-1-06 Start of Phase II Flight Program
➢ 11-17-06 through May 2007 Phase II Flight Tests
System Architecture
Production Support Flight Video Input Control Computers Push Button Display Command/ Pitch Stick Status Roll Stick Rudder = 0 Information Delta Throttle Data Link Tanker Pallet Receiver System
Refueling Geometry
Precontact 1&2 Position 20' Closure Capt Hold 100' Position Trail Position
AARD Modes and States
Trail Ready Closure Retreat Init Precont Precont Miss Standby Capture Hold Relative GPS Relative GPS + Tracker Unplug
Accuracy Design Targets
➢ Station Keeping Mode.
➔ ± 6.5' longitudinal position
➔ ± 6.5' vertical position
➔ ±10' lateral position
➢ Capture Mode
➔ System must be able to reliably guide/control receiver aircraft
within ± 11 ” of desired location, in the conditions intended for
demonstration, 95% of the time
➔ Requirement driven by basket dimensions: 32 ” outside diameter
➔ Project pilot estimates plug success rate at 95% if the probe is
positioned inside 4 ” from outside edge of drogue
Omega Tanker Risk Reduction
➢ Approach to plug on left and right drogues using the cockpit and
pylon camera
➢ Tanker pitch/ roll/ yaw maneuvers
➢ Varying approach rates/ trajectories
➢ Survey of capture and miss locations on the drogue
➢ Varying plug attempts at different diameters from the center of the
drogue
Ground Test Activities
Cart Testing
Evaluated Tanker/ Receiver subsystems and communications Performed Prior to hardware delivery to Dryden
Simulation Lab testing
Performed formal Verification and Validation testing of G&C algorithms Performed failure modes and effects testing
Hanger Radiation Testing
First Integrated systems testing with a stationary aircraft First evaluation of tracker performance
Combined Systems Testing
Plugs out evaluation of the integrated system Evaluation of tracker performance during taxi.
Combined Systems Taxi Test
Surrogate Tanker Flights
Surrogate tanker was used to increase test efficiency
➔ Lower cost per hour to fly
➔ Easier to schedule.
Tested engage/ disengage/ reversion modes.
Commanded Autonomous modes through Precontact 1
Gathered system performance data using sine and step inputs
Gathered system performance data for a variety of gains
Tracked Surrogate tanker through a turn in Trail and Precontact 1
Omega Tanker Flights
Tested engage/ disengage/ reversion modes.
Commanded mode transitions through unplug
Gathered/ tuned the video tracking algorithm.
First Plug Attempt
Second Plug Attempt
Success
Control Position Comparison
Phase II Flights
➢ Demonstrated Autonomous Rendezvous to Trail Position
➔ 2000 ft trail, 1000 ft low, 500 ft lateral offset ➔ 15 to 20 kt closure rate
➢ Demonstrated Autonomous Plug in a turn
➔ 20 Deg Bank turn ➔ Achieved a stable hold position in turn ➔ Unplug in turn
➢ Controller and Tracker evaluation/ tuning
➔ Have shown improvement in both controller and tracker performance.
➔ Demonstrated successful plug in mild turbulence
Phase II Plug Performance
Phase II Plug in a Turn
Summary
➢ Designed, developed and successfully tested a prototype
system to autonomously perform probe to drogue
refueling .
➢ Demonstrated acquisition and tracking capability of the
video tracking subsystem.
➢ Demonstrated autonomous rendezvous capability
➢ Demonstrated the ability to plug in a turn
➢ Demonstrated the ability to plug in mild turbulence
Questions?
System Architecture
Discrete Surface Input Data Actuator GPS Recorder Output Ant IMU Analog Input Actuator Control Signal Interface Signal Signal A/D Laws Selected Management Management D/A Fader logic Data Nav I/O Data Dual Port Ram Link Processes Link Ant Processes Analog Disengage Replication Inputs NASA Logic CLAW Instrumentation Control Operating System System Positions (AIMS) Executive Data Tanker Pallet Camera Recorder (2) Flight Control Computers Bus 1 Data 1553 1553 Link Input Output Simulation Ant Video Interface Analog Processes RS 422 Processes Multiplex Operating System I/O Card Push Button Display Data Executive Process Discrete GNC Link D/A IMU Output Processes Cockpit Processes Analog SLIC Inputs Pilot Light Display AARD Panel Ethernet Ethernet Nav PVI GPS Handler Handler I/O I/O Processes Processes Ant Instrumentation Handler Operating System Pilot Vehicle Interface AARD Controller