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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 l.jpg

Navigation Team

Indy Robotics Racing


Mission l.jpg
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


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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


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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


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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


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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


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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


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  • Sensors:

    • GPS (Lat/Long/error): Navcom

    • Heading (magnetic course): Garmin – AHRS

    • Speed: TBD

    • Time: Internal clock

    • Distance: Odometer or other


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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


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External Reference

  • GPS

  • Visual ID of waypoint

  • Visual ID of surface features

  • Visual or other ID of structures like towers.

    • Cellphone

    • Power grid


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GPS

  • Best accuracy in motion: assume 1 foot

  • Update cycle: 1 second

  • Messaging method:



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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


Odometer l.jpg
Odometer

  • Trailing or wheel based

  • Other


Speed l.jpg
Speed

  • GPS speed input

  • Direct speed input from the vehicle


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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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