Laserhawk

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LaserHawk Project Description

Lidar UAV for traversability map generation

High-level Goals

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1. Autonomous flights of Multiplex Mentor UAV with onboard payload including:
   • Hokuyo UTM-30LX LIDAR sensor
   • OMAP3 Gumstix Overo
   • Xsens MTi and MTi-G IMU/AHRS
   • Paparazzi autopilot
2. Generate traversability map that can be transmitted to UGV
   • cartesian coordinates with traversability probabilities/confidence

Current Tasks and Priorities

TASK LIST

Num	Name	Notes	Priority	Status
1	Acquire Lidar/attitude data from rooftop	use PC then gumstix	x	Starting
2	start flying mentor airframe	x	x	Bertrand ready?
3		x	x	x
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Architecture

1. Communication
   • autopilot/groundstation - standard paparazzi Datalink/Telemetry serial modem-based com
   • gumstix/ground - wifi for debugging
   • UAV to UGV com : TBD

Hardware

Airborne

• Autopilot : paparazzi
• Hokuyo : UTM-30LX
• Xsens : MTi-G

Ground

• Who cares? laptops, modems, and antennae should suffice

Software

Version control : github

Airborne

• Overo
  • OS: openembedded-built linux (rt?)
  • Drivers: hokuyo/xsens stuff (robotpkg et genom )
  • apps:
    • mainloop for sensor data processing
    • coordination with ground
    • coordination with autopilot
• Autopilot
  • paparazzi LPC2148-based firmware

Ground

• Paparazzi ground package
• gdhe for data visualization (polyline representations of laser scan lines)

Projects:

1. hoku2gdhe - Demo application uses hokuyo and Xsens MTI sensor and generates polylines in GDHE
   

   hoku2gdhe

Geometry

Laserhawk geometry
Overview	Detail
Figure 1	Figure 2

• nominal UAV flight velocity : 20-30 m/s
• nominal UAV flight height AGL : 30 m
• Lidar sensor resolution : 1080 points over 270 deg visible (1440 points over 360 deg) @40Hz

• ground covered distance during one revolution of scanner:

$Dist_{per\_scan\_rev}=ground\_speed\times time_{per\_scan\_rev}=20~{\frac {m}{s}}\times {\frac {1}{40}}~s=0.5~m$

• For 90° interest zone :

• scan line advances down ground track :

$Dist_{x}={\frac {90}{360}}\times Dist_{per\_scan\_rev}={\frac {1}{4}}\times 0.5~m=12.5~cm$

• scan line proceeds along sensor rotation (for a 90 scan, this is twice the AGL height) :

$Dist_{y}=2\times AGL=2\times 30~m=60~m$

• Resolution :

${\frac {{\frac {90}{360}}\times 1440~pixels}{scan\_length}}={\frac {360~pixels}{\sqrt {{Dist_{x}}^{2}+{Dist_{y}}^{2}}}}\approx {\frac {360~pixels}{Dist_{y}}}=6~{\frac {pixels}{m}}=17~$cm between pixels

• Angle relative to track :

$Angle_{scan\_to\_track}=\tan ^{-1}{\frac {Dist_{x}}{Dist_{y}}}=\tan ^{-1}{\frac {0.125}{60}}=0.119^{\circ }$ (negligible relative to crab angle)

Scratchpad

MTI comand line application, for dumping attitude/GPS of MTIG to file : (PC and overo)

MTIHardTest /dev/ttyUSB0 -o 2 -d 6 -v >> MTIG.out

record laser scans to disk (PC and overo) hokuyomti /dev/ttyACM0

scan and display on gdge (PC only for now)

hoku2gdhe

Risks

Risks and unanswered questions

Num	Name	Notes	Priority	Status
1	Lidar performance	at 30m flight height, over row-reflectance surfaces (roads)	x
2	Crashing Lidar	Will build metal/foam box for protection	x	x
3	Radio interference at Elrob	need robust behaviors with lost com	x	x
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