Real-Time, Reactive Planner for Aggressive 3D Aircraft Maneuvers

1. Real-Time, Reactive Planner for Aggressive 3D Aircraft Maneuvers AIAA@Infotech 2012 Presented by: Dick Stottler stottler@StottlerHenke.com 650-931-2714

2. Overview Problem Addressed Motivation High Level Context PRM Planner Design • Maneuver Library • Hand-Off/Hand-Back Criteria • Milestone Selection Criteria Results/Scenarios Future/Current Work: Full-Scale Implementation Conclusions

3. Problem Addressed Close-in, unguided threats allow little reaction 60% Iraq/Afghanistan aircraft losses Hostile Fire Indicator detects RPG launches Other sensor systems detect other hostile fire But pilot only has a fraction of a second to react and reaction must be aggressive Often multiple simultaneous threats Other aircraft in formation; Popup obstacles Multiple simultaneous goals/objectives/priorities Future: manned/unmanned aircraft in formation

4. Motivation • Emergency situations call for extreme maneuvers • Hostile Enemy Fire • Collisions with other aircraft or objects • Maximum dynamic limits versus total lost • Pilot often otherwise engaged • Need short term path planner (PP) • Safe flight paths • But provide maximum deviation • A/C may automatically follow path or display for pilot • Future: increased hostile fire & fire detection systems • Automatic, aggressive maneuver PP natural complement • Also useful for UAV, including formation flying • Future attacking UAV, nap of earth flying, avoid detection

5. Prototype Path Planner (PP) Approach to Aggressive Aircraft PP Is Feasible 0.1 Seconds Returned Viable Plan < 2 feet error in predictions Maneuver Library required: aggressive/moderate Recorded from simulations with real pilots Can interpolate in between Can have variable time / constant attitude Readily applicable to different platforms PP Prototype solved every problem given to it

6. PP Prototype • Uses highly aggressive maneuvers • Produces Routes Several seconds Long • Always physically realizable • Avoid the static & (multiple) dynamic terrain • Respect aircraft structural & aerobatic limits • Stay within the allowed torque range • Maximize distance from likely multiple munition paths • Considers aircraft’s mission, role, environment • Large # simultaneous/sequential threats/issues

7. High Level PP Context

8. Probabilistic Road Map (PRM)

9. Maneuver Library • Stored with Each Maneuver: Applicability, Control Inputs over time, Resulting Attitude and Trajectory over time • Used to predict where the aircraft will be and when, if the maneuver is selected • Many maneuvers for diff. conditions • Effectively captures the expertise of the best pilots, with time to think, prepare, and do-over • Retrieves and instantly utilizes that expertise (the maneuver) in time-pressured emergency • Maneuvers can be semi-manually enhanced (edited)

10. Hand-Off / Hand-Back Criteria • PP takes over when a threat is sensed • Hands back control when: • No new threats • No remaining incoming objects • Helicopter is trim • No collision projected for at least 4 seconds • Typically controls for only a few seconds • Unless there is a series of separate shots

11. Unguided, Untracked Threats Helicopter’s Position, Velocity Vector, & Angle to Shot Define a Plane of likely trajectories for close in shots. (Longer shots tend to fall short) Side View From Behind From Above

12. Milestone (m) Selection Criteria Score(p,v) = WS∙min(mini(di(p), T) + WE∙ΔE(p,v,p-1,v-1)+Sjnj(p)∙wj p: The position of the aircraft at the milestone v: The velocity of the aircraft at the milestone p-1: The position of the aircraft at the previous milestone. v-1: The velocity of the aircraft at the previous milestone. Di(p): The distance from p to threat i T: Threshold distance at we are considered safe and consideration shifts to other priorities ΔE(p,v,p-1,v-1): The change in energy from the state at t-1 to the state at t, as a ratio to kinetic energy E(p,v)=Ep(p)+Ek(v) Ep (p)=32.174⋅altitude(p) Ek (v)= (1/2)v2 nj(p) = number of threats/goals of type j (LOS) visible from p

13. Prototype Testing Based on ART’s FlightLab High fidelity OH-58D Kiowa Warrior model Sim. cockpit instruments & out the window display Video capture the OTW display and instruments Plot/Video the helo’s trajectory & munitions in 3D API for aircraft state data & control inputs Variety of different types of terrain FlightLab model obeys the aircraft constraints

14. Demonstrations Simple Shot Avoidance Popup Obstacles Terrain Avoidance Build-Up Base: 2 shots, under then over (terrain) + 1 Wire: under then under (wire above) + 2 Wires, another wire is ahead & below, can’t sink so climb (just enough, not too much) + 3 Wires: third wire blocks best maneuver so turn flat. (Not great, but no choice) 5 Sequential Shots Grand Finale: 12 shots at 5 times

15. Overhead view of shots from right and ahead/below

16. Shot from front and below

17. Shot from front and below

18. Shot from front and below

19. Shot from the right

20. Shot from the right

21. Both Shots taken together

22. 2 Sequential Shots from the right: Drop then Climb

23. Drop then Climb, During Climb

24. Popup wire

25. Landing, Right to Left, No Obstacle

26. Landing, Until Obstacle Pops Up

27. 2 shots with terrain and popup wires

28. Built up example of shots and wires

29. 5 Sequential Shots

30. Grand Finale

31. Current Phase II System AH-64D Apache - Based on ART’s FlightLab (& TBD UAV) FlightLab model obeys the aircraft constraints Simulated cockpit instruments & out the window display – Desktop & Medium fidelity dome simulator Maneuver Library Building Software for pilots Video capture the OTW display and instruments Plot/Video the helicopter’s trajectory & munitions in 3D Plot control inputs and model outputs Automatically check important outputs (e.g. Gs and torque) Easily Adaptable to any Aircraft • Controls, Simulation Model, Maneuver Library • Interface to Perceptual System

32. Conclusions • PRM applicable to aircraft path planning • PRM PP can produce safe/aggressive paths within 0.1 second deadline • PRM PP always returned a valid route • (No matter how complex the scenario) • Easily adaptable to different aircraft