Sensors For Mobile Robots
FIGURE 16. Parallax
laser range finder.
many small robot platforms. Figure 15 shows a
sketch of the triangulation method this and most IR
range finders use. Very complete information can be
found at “Demystifying the Sharp IR Rangers” on the
Parallax Laser Range Finder
Many of us have longingly looked at the Hokuyo and
SICK laser range finders and wish that we could shovel out
$1,200 to over $5,000 for one of these quality units.
They’ve adorned the fronts of DARPA Grand Challenge
vehicles, as well as top-of-the-line industrial robots. Some
builders have taken the laser range finders that hunters or
golfers use and have converted them for robot use.
However, Parallax — in conjunction with Grand Idea Studio
— has produced an affordable $129.99 laser range finder
that is made to use on robots. Shown in Figure 16, the
3.95” x 1.55” x 0.67” module operates off of 5.0V 150
mA. Communication is by an asynchronous serial 300-
115,200 baud output.
The Arima laser on the right in Figure 16 is tiny
enough, but the tiny object with the red dot on the left
is a full VGA camera that detects the projected red 635
nm (visible) red laser dot’s position angle to determine
distance by triangulation. Note in Figure 15 how the dot’s
position appears at a greater angle at a closer range for the
Sharp linear array. The difference here is that the camera
and laser are 78 mm apart, and the detector is a VGA
camera rather than a linear array (as in the Sharp sensor).
Figure 17 shows the inner structure of the tiny 1/13”
camera with two filters and two lenses. Check out the
Parallax, Grand Idea Studio, and OmniVision sites for some
very interesting information, and also the October and
November ‘ 11 issues of SERVO in which Joe Grand
(President of Grand Idea Studio) wrote a complete
description of the board.
I will cover compass, location, and robot positional sensors
in next month’s column. I would like to thank my friend
Bart Everett, Technical Director for Robotics at the SPAWAR
Systems Center, for help with my intro about him and his
friendship. Personnel at Parallax, MaxBotix, the RobotShop,
and Acroname have been most helpful in assisting me with
their products and specific information. It is companies like
these (and others) that allow us to build the robots of our
with every prototype order
EAGLE order button
on your first order
Call Tyler: 1 707 447 7744
I have covered only a small portion of the many sensors
used just for object detection and range finding for robots.
Tom Carroll can be reached at TWCarroll@aol.com.
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SERVO 05.2012 79