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Navigation Team

Navigation Team. Indy Robotics Racing. Mission. Inputs from sensors GPS, heading, distance, speed, time Compute position using multiple methods DR (primary) GPS (secondary – primary for correction) Visual (secondary – secondary for correction)

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Navigation Team

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Presentation Transcript

  1. Navigation Team Indy Robotics Racing

  2. Mission • Inputs from sensors • GPS, heading, distance, speed, time • Compute position using multiple methods • DR (primary) • GPS (secondary – primary for correction) • Visual (secondary – secondary for correction) • Determine when DR position correction is appropriate • Output • Current position • Vector to next waypoint • CDI (course deviation indication) • Distance traveled, distance remaining • Time elapsed, time remaining • ETE (est time enroute), ETA at projected speed • Avg speed, +/- from planned speed, avg speed to complete, +/- from planned

  3. Definitions • CDI=Course Deviation Indication=lateral distance off centerline course • ETA=Estimated Time of Arrival at the finish line • ETE=Estimated Time Enroute to the finish=sum of remaining leg times • ATE=Actual Time Enroute for the course traversed to date • Expected time=sum of reference leg times traversed to date

  4. What questions does the navigator answer? • Where are we? • Lat/long/error estimate • CDI (course deviation indicator = lateral distance offset from current vector) • Where do we go next? • Direct course from current position to next waypoint • Next vector: Heading, distance, reference speed from nxt wpt to nxt wpt+1 • Second vector: Heading, distance, reference speed from nxt wpt+1 to nxt wpt+2 • How are we doing? • Elapsed time, elapsed time expected, delta • Average speed, expected average speed, delta • Distance traveled, distance to go • Time remaining to deadline, estimated travel time remaining, delta • ETA, delta to deadline • Average speed required, projected avg speed, delta

  5. Position definition • Primary method: Dead Reckoning (internal reference calculations) • Computes position 4 times per second • Heading-speed or heading-distance as input • Error correction: Progressive error of DR is corrected from GPS, inertial navigation, other • No time delay if external reference systems are lost or delayed

  6. Data Flow Current Position/error Wpt DB Dead Reckoning Calculator CDI Next Wpt Vector Second Wpt vector ETE/ETA Avg/Required speed Past Position DB Correct position Current position Heading, distance, speed, time Position and error comparator Current position GPS Position

  7. Error Correction Process • Error calculator reports that at time t-x the position determined was in error. • In the past position database, the position at time t-x is corrected • All subsequent DR vectors and end positions are recalculated and updated in the past position database • DR calculator re-computes the output series

  8. Sensors: • GPS (Lat/Long/error): Navcom • Heading (magnetic course): Garmin – AHRS • Speed: TBD • Time: Internal clock • Distance: Odometer or other

  9. Polling and Compute cycles • GPS: 1 second (or device standard) • Heading: 1 second intervals • Speed: 1 second intervals • Time: na • Distance: 1 second • DR Position computation: 4 Hz • Error comparator: 1 minute

  10. External Reference • GPS • Visual ID of waypoint • Visual ID of surface features • Visual or other ID of structures like towers. • Cellphone • Power grid

  11. GPS • Best accuracy in motion: assume 1 foot • Update cycle: 1 second • Messaging method:

  12. Internal Position Reference

  13. Heading Reference • Garmin AHRS (primary) • Inertial reference for both heading and attitude (pitch and roll) • Aircraft gyrocompass (secondary) • Slaved w/ magnetic correction for precession • Open Issues • Initial reference setting prior to the race

  14. Odometer • Trailing or wheel based • Other

  15. Speed • GPS speed input • Direct speed input from the vehicle

  16. Data Management • Waypoint database and Past Position database • Telemetry database during testing • Ancelus v1.3/Linux • Totally memory resident • Fast • Lookups @ 5 mil TPS, insert/delete @ 360,000 tps. • Minimum footprint • About 20kb + dataspace • Dataspace compression of about 5:1 vs typical relational. • The price is right

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