57 Robotics: Measuring 3 or 6DOF position part2
Description
This article is from the Robotics FAQ, by Kevin Dowling nivek@cs.cmu.edu with numerous contributions by others.
57 Robotics: Measuring 3 or 6DOF position part2
"Polhemus Inc."
Burlington, VT
tel: 802.655.3139
fax: 802.655.1439
3Space, Isotrak, FasTrak: Electromagnetic devices for sensing xyz
and rotations remotely. Limited to 1m or so radius. Sensitive to
metallic objects in vicinity. Approx $3k
"Ascension Technology Corporation "
PO Box 527
Burlington VT 05402 USA
tel: 802.860.6440
fax: 802.860.6439
net: ascen@world.std.com
Sales: Jack Scully Technical Support: Steven Work Product is called
Flock of Birds. A 6d0f measuring device. Ftp site is
[55]ftp://ftp.std.com/ftp/vendors/Ascension/
gen_lit.txt
Contains general literature on 6D motion tracking system.
Accuracy Specifications, comments from prominent users, list of
3rd party software vendors, FAQ on tracking system, etc. Ascii
text.
tecpaper.wp6
Technical Description of Flock of Birds (TM) 6D tracking
system. In Binary WordPerfect 6.0 format.
userware.zip
Latest version of our User Software, including source code.
Enjoy. pkzipped binary file.
manual.wp6
Latest version of our User Manual. In Binary WordPerfect 6.0
format.
readme.txt
more info on files located in Ascension's FTP directory. Ascii
text.
Sensitivity to metal is claimed to be on the order 5 to 10 times
less than Polhemus tracker. Range and specifications are much better
as well.
The Ascension Flock of Birds tracker is DC pulsed, where the
Polhemus is AC magnetic field. The AC field set up standing waves in
metal (conduction and ferrous) which magnify the distortion effect.
Charts provided by Acension:
KEY PERFORMANCE PARAMETERS OF ASCENSION & POLHEMUS TRACKING DEVICES
Parameter Ascension Polhemus Polhemus
Flock of Birds Isotrak II Fastrak
Measurement Rate
(Measurements/sec)
1 Receiver 144 60 120
2 Receivers 144 30 60
@ Max Number of Rcvrs 144 30 30
Maximum Number of Receivers 30 2 32
Number of Transmitters to 1 1 4
Support Max Number of Receivers
Maximum Data Output Rate 312K 115K 115K
(Baud or Bytes)
Lag Increase with Multiple No Yes Yes
Receivers**
Range - Standard Transmitter 3' 5'* 10'*
- Extended Transmitter 8' N/A N/A
Accuracy Degradation Due to:
Conductive Metals Low High High
Stainless Steel None High High
(300 series)
CRT Interference Rejection Yes No Yes
LCD Noise Susceptability No Yes Yes
Unit Cost (1 Receiver) $2,695 $2,875 $5,750
* Note 1: Polhemus specifies range at maximum transmitter-sensor
separation distances. At these ranges, outputs will contain
significant amounts of noise, which may render their measurements
worthless. We will provide you with a number of references who have
independently assessed actual range performance of both Ascension
and Polhemus trackers.
** Note 2: For a complete discussion of latency in competitive
motion trackers, contact Ascension.
Specifications:
Technical
Translation range: plus or minus 3'(8' optional) in any direction
Angular range: plus of minuw 180 degrees Azimuth & Roll
plus or minus 90 degrees Elevation
Translation accuracy: 0.1" RMS
Translation resolution: 0.03"
Angular accuracy 0.5 degrees RMS
Angular resolution 0.1 degrees RMS @ 12"
Update rate: Up to 144 measurements/second
Outputs: X,Y,Z positional coordinates and orientation
angles or rotation matrix
Interface: RS-232C with selectable baud rates to 115,200; or
RS-422/485 with selectable baud rates to 310,000
Format: Binary
Modes: Point or stream
Physical
Transmitter: 3.75-inch cube (internally mounted in Enclosure or
externally mounted with 10' cable) or extended range
transmitter option: 12-inch cube externally mounte with
20' cable
Receiver: 1.0" x 1.0" x 0.8" cube (or optional 3-button mouse)
with 10' or 25' cable
Enclosure: 9.5" x 11.5" x 2.6"
Power: User provided or optional external plug-in: US/European
version
Environment: Large metallic objects in operating volume may degrade
performance
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