1. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB, An Improved Line-of- Sight Guidance Law for UAVs R. Curry, M. Lizarraga, B. Mairs, and G.H. Elkaim University of California, Santa Cruz

2. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Accelerating UAV Demand Military Civilian Forestry Marine Fisheries Photography Border surveilance New Missions  New Autopilot Designs

3. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB SLUGS GABE INSERT YOUR SLIDE HERE

4. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Talk Outline Review of a simple but effective UAV guidance law Examine the impact of roll dynamics Extend the concept to Improve stability All operational situations Compare the two in 6 DOF simulations

5. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Line-of-Sight Guidance Originally proposed by Amidi (1991) for robots Park, Deyst, How (2007) made significant contributions Theory Linear Analysis Asymptotic stability Flight demonstrations A form of pursuit guidance originally used in air- to-air missiles, but range doesn’t change

6. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Line-of-Sight Guidance

7. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Commanded Acceleration Geometry Kinematics Combined constant UAV Bank angle

8. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB L1 Stability We noticed that L1 became less stable in downwind conditions Simulations Flight experiments Also mentioned by Niculescu (2001) L1 ignores roll dynamics We used the Park/Deyst/How linear model to explore this

9. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Linear Model (Park, Deyst, How)

10. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Linear Model (cont) System Response where Note: Let

11. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Linear Model with Roll Dynamics

12. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Root Locus with Roll Dynamics

13. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Summary of Guidance Asymptotically stable assuming instantaneous acceleration response (Park/Deyst/How) Accurate tracking for circles (Park/Deyst/How) Reduced stability with increasing ground speed due to roll dynamics not defined in some operational situations

14. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Potential Improvements to Sensitivity to groundspeed

15. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Guidance Look ahead distance not constant is constant Now system poles independent of ground speed Accel command ALWAYS define an aim point by Limited intercept angle (reduce overshoot) Limited down track aim point distance Large errors and track acquisition

16. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Guidance

17. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Simulations 6 DOF rigid body nonlinear model of Rascal UAV Hobby aircraft, wing span of 1.2m Inputs: throttle, elevator, aileron, rudder Outputs: 12 state variables Dryden model winds Constant wind Gust levels depend on height above ground and mean wind

18. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB and on Waypoints

19. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB and Circle Tracking

20. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Homing Mode What if there is a destination but no path? Steer the ground track to the line of sight toward objective Same as ATC command “direct to” uses one guidance law in all conditions “Return To Base” if a comm or GPS failure

21. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Homing Mode—Return To Base

22. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Moving “Base” The homing mode only requires a line of sight to the objective There is no requirement that the objective be stationary On a whim, we tried tracking a moving objective We used the homing mode without any modification Results were very encouraging

23. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB RTB with Moving “Base”

24. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Summary Amidi/Park/Deyst/How is a very simple and efficient pursuit guidance law But roll dynamics and increased groundspeed lead to more instability scales look-ahead distance with ground speed System response time determined by System poles independent of groundspeed

25. UC SANTA CRUZ, AUTONOMOUS SYSTEMS LAB Summary (cont) Extended the operational envelope by always having an aim point Large path errors Path acquisition Homing mode 6 DOF simulations show Improved response, no impact of groundspeed Extended operational envelope RTB works with a moving base