Tilting Hokuyo

Author

Advait Jain (http://www.cc.gatech.edu/~advait)

What this does

Tilting the Hokuyo using a servo and reading back the servo encoder position while getting scans from the Hokuyo allows us to generate a 3D point cloud of the world in front of the robot. We have used this 3D point cloud for object segmentation, door handle detection etc.

We first used this sensor in this paper: EL-E: An Assistive Mobile Manipulator that Autonomously Fetches Objects from Flat Surfaces. Advait Jain and Charles C. Kemp. Autonomous Robots, 2009. This paper and others can be downloaded from the Heathcare Robotics Lab website (http://www.healthcare-robotics.com)

• Sample Point Clouds
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Pictures of the Setup

• Servo Tilting the UTM
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  Firefly Camera, UTM and Servo (left to right)

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• Alternate Configuration
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Hardware

Image of the solidworks part for the bracket to mount the UTM on to the servo.

This is the hardware setup that we use:

• Tilting servo: Robotis Servo (typically we use RX-28) http://www.crustcrawler.com/motors/RX28/index.php?prod=66
• This gives a serial interface to control the servo: http://www.crustcrawler.com/electronics/USB2Dynamixel/index.php?prod=65
• Hokuyo UTM. (http://www.acroname.com/robotics/parts/R314-HOKUYO-LASER4.html)
• Bracket to mount the Hokuyo on to the servo.
  • This is a custom part that we have designed.
  • The solidworks CAD file (utm-servo-bracket.sldprt). This requires Solidworks 2009.
  • We have taken two routes for making the bracket
    1. buy Aluminium channels from http://mcmastercarr.com and drill the appropriate holes.
    2. use http://www.mfg.com to get the part manufactured from the CAD file. Will take between a week to 10 days.
  • We thank Abhishek Bhatkhande for making the CAD model from the bracket design.
• Screws:
  • Four M2x4 (2mm diameter, 4mm length) to connect the servo to the bracket.
  • Two M3x6 or M3x8 to connect the UTM to the bracket.
  • Longer screws will require washers.

Code

• ROS (http://www.ros.org)
• You will need the following ROS packages from our public ROS repository (available at http://code.google.com/p/gt-ros-pkg/wiki/hrl_content_summary)
  1. robotis
  2. hrl_hokuyo
  3. hrl_tilting_hokuyo