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Section 3: Mobile Robot Positioning
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Key features of the
High-accuracy Dead-reckoning System (HADRS)

  • Works on any wheeled or tracked ground vehicle.

  • Works on any terrain, including rugged, steeply inclined terrain.

  • Requires only a power connection and wheel/track encoder data from the host vehicle.
    Optionally, system can use encoder data from our retrofittable add-on encoders, making it independent of host vehicle encoders.

  • Works without GPS, computer vision, beacons, or any other external references but can accommodated and integrate optional external GPS.

  • Is indifferent to environment: indoors, outdoors, urban, or rural.

  • Is small-sized and fits into 1/3 Packbot payload bay (rev.2, under development, is even smaller: 6.23x2.87x3.25 inches).

  • Is designed for minimal power consumption.

  • Outputs JAUS compatible, time-stamped X, Y, Z, and heading data stream at 10 Hz.

  • Outputs data via Ethernet, WiFi, RF, or long-range RF data modem.

  • Is unaffected by extreme operating temperatures or sudden changes in operating temperatures.

HADRS installed on a Packbot. HADRS fits neatly into 1/3 of the payload bay of a Packbot, but can be mounted on any wheeled or tracked ground vehicle.


For missions of up to 30 minutes duration:

  • Average position error: 0.5% of distance traveled even on rugged terrain;

  • Maximum position error: 1% of distance traveled

  • Average heading error: 1 deg

    Errors may be larger on deformable terrain (sand, mud) or any other terrain that promotes excessive track slippage.

  • For longer missions, position errors increase at ~1% for every 30 minutes of operation.


Typical trajectory of  a HADRS-recorded Packbot run over rugged, steeply inclined terrain.

Typical Experimental Results

Red curve (in figure on the right): trajectory recorded by the HADR system  
Note: Packbot started and stopped at the same point (0,0)
Total travel distance:   676 m
Total travel time:   28.5 min
Return Position Error:   1.04 m  (=0.15% of total distance traveled)
Largest position error anywhere during this run: ~2 m (=0.3% of total distance traveled)
Steepest slope traversed: 10 - 15 deg on grass
Challenges in this experiment: partially sloping terrain, traverse of several curbs


System components

Controlled by a Gumstix computer-on-module.
Sensor modalities:
- NavChip inertial measurement unit (IMU)
- KVH single-axis fiber optic gyro (FOG)
- Host's odometry OR our add-on encoder system.
- Active temperature stabilization for FOG and IMU.
- Integration with external GPS receiver.
- Operator console unit with
>Option 1: Text only
>Option 2: trajectory plotter to support tele-operation

Total cost of the off-the-shelf system components: ~$7,000



Block diagram of the main hardware components of the HADR System.


HADRS rev. 2 dimensions