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. Have MTIG and works with PC and gumstix. Need to build boom and get some sort of display capability to visualize while capturing (webcam)	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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