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A utonomous H elicopter N avigation S ystem 2010

A detailed overview of the communication protocols (WiFi and Wireless Router Network) and sensor architecture (Kalman Filter) implemented in an autonomous helicopter navigation system. The system includes state estimation, altitude sensing, camera capabilities, and localisation techniques. Progress, future work, and system demonstration are discussed.

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A utonomous H elicopter N avigation S ystem 2010

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  1. Autonomous Helicopter Navigation System 2010

  2. Communication Liam O’Sullivan - 06308627

  3. Previous Years Communications • Control was off board (on the GCS) • Used XBeeZigBee RF modules for telemetry • Point to point communication • Successful communication link • Disadvantages • Serial interface • Closed architecture • User implemented synchronisation • No interface standard

  4. Communications

  5. WiFi Communication Protocol • Server to client architecture • Main server onboard (devices connect to it) • Multiple device/client connections • Standard networking protocol (UDP and TCP) • Utilises ‘Heliconnect’ • Common network interface • Ability to communicate with other projects

  6. WiFi Architecture • Wireless adhoc network (point to point) • Unstable (particularly for non-Apple products) • Incompatible • Wireless router network • Centralised router • Uses Linksys WRT45GL • Devices communicate through the router • Internet gateway

  7. Wireless Router Network

  8. Communications Summary • WiFi architecture implemented • Stable and reliable connection between platform server and clients

  9. State Estimation Liam O’Sullivan - 06308627

  10. State Estimation

  11. Platform States • 17 States to be measured

  12. IMU • Sensor Dynamics 6 DOF IMU • 3 gyroscopes and 3 accelerometers • Measures • Angular rates • Accelerations • Indirectly measures • Angles • Velocities • Displacement • 75Hz update rate • SPI connection (with Overo Fire) • Inherited from AHNS09

  13. Vicon System • External motion capture system • Tracks reflective spheres with 5 IR cameras • Can measure all required states (except the camera tracking states) with sub mm accuracy • 200Hz update rate • Not used for low level control (latency) • Verification and Validation tool • Ethernet connection (via GCS) • Located at the ARCAA building

  14. Altitude Sensor • Maxbotix ultrasonic sensor • Measures vertical displacement • Sonar range finder (not IR based) • Replaced by Vicon System • Still incorporated for redundancy • UART connection (with Overo Fire) • Inherited from 3rd year project

  15. Surveyor SRV-1Blackfin Camera • Blackfin camera with Analog Devices processor • Embedded image processing (IP) • Interface and IP library • Get camera frame • Edge detection • Colour segmentation • Blob detection and others • WiFi connection (camera feed) • SPI connection (IP tracking states) • Recommended by Supervisor

  16. Sensor Architecture

  17. Kalman Filter and Sensor Fusion • IMU measurements are noisy and will drift • Require attitude estimator to correct for this • Will be based on the attitude estimator from AHNS2009 • Basic Kalman filter

  18. Subsystem Progress and Future Work • All sensors are operational • Software interface libraries completed for • IMU • Blackfin Camera • Future work • Altitude sensor software interface • Vicon system client • Attitude estimator implementation

  19. Localisation Liam O’Sullivan - 06308627

  20. Localisation

  21. Original Purpose • Blackfin Camera mounted underneath platform • Search for cross “blob” to localise itself (via IP) • Dead reckoning navigation from blob centroid (x and y displacement)

  22. Updated Design • Newly integrated Vicon system eliminates need for dead reckoning • Will now perform a path tracking function for autonomous navigation (xt and yt displacement)

  23. Localisation Summary • Success of this subsystem is dependent on all other subsystems • Re-evaluation of subsystem may need to occur if project progress stalls

  24. System DEMONSTRATION AND QUESTIONS

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