Navigation Team

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

• CDICourse Deviation Indicationlateral distance
  off centerline course
• ETAEstimated Time of Arrival at the finish line
• ETEEstimated Time Enroute to the finishsum of
  remaining leg times
• ATEActual Time Enroute for the course traversed
  to date
• Expected timesum 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 wpt1
• Second vector Heading, distance, reference speed
  from nxt wpt1 to nxt wpt2
• 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
Dead Reckoning Calculator
Wpt DB
CDI Next Wpt Vector Second Wpt vector ETE/ETA Avg/
Required speed
Past Position DB
Current position
Correct 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 _at_ 5 mil TPS, insert/delete _at_ 360,000 tps.
• Minimum footprint
• About 20kb dataspace
• Dataspace compression of about 51 vs typical
  relational.
• The price is right?