View Full Version : Handwriting & Walking Birds

Herman J. Woltring
03-07-1991, 07:20 AM
Dear Biomch-L readers,

>From the present guest account (UGDIST refers to the Department of Informatics
at the Universita di Genova, Italy, with Prof. Piero Morasso as the main party
involved, and HNYKUN53 to the Subfaculty of Psychology at Nijmegen University,
The Netherlands), I'd like to mention a paper that I came across today:

R. Plamondon, L. Yu, G. Stelmach & Bernard Clement, On the Automatic
Extraction of Biomechanical Information from Handwriting Signals, IEEE
Transactions on Systems, Man, and Cybernetics, 21(Jan/Feb 1991)1, 90-101.

In the references, a substantial number of papers from colleagues at the
Nijmegen Subfaculty of Psychology are quoted. Recalling a recent, Scottish
claim on this list that Psychologists sometimes come first, I think that this
paper merits attention.

>From a measurement point of view, my posting last year on electromagnetic
measurement of body segment and joint movement can be updated, also in view
of Mike Whittle's recent list of manufacturers. Today, I received a note
from Ascension Technologies, P.O. Box 527, Colchester, Burlington, Vermont
05402, U.S.A., Tel. +1.802.655-7879, FAX +1.802.655-5904, just after I had
finalised a report under the CAMARC contract. [The report describes, a.o.,
experiences with Ascension's competing system 3SPACE ISOTRACK for real-time
position and attitude measurement in 3-D from Polhemus Inc., also of Col-
chester.] I think that it might be fair to all parties concerned to quote
the STOP PRESS item added to the relevant chapter:

... a New Product Announcement (February 20, 1991, For Immediate
Release) was received from Ascension, mentioning, among others, the
`Flock of Birds', allowing "simultaneous tracking of up to six tiny
receivers by as many transmitters". Each of these systems operates
at a sampling frequency of 100 Hz, and spatial resolution is 12 bits
per co-ordinate. "In the `Walking Bird mode', a user straps on one
to six receivers and is then free to walk about a room. Transmitters
geometrically positioned throughout the walking area are activated
and deactivated as the user moves from the operating volume of one
transmitter to another. This occurs under host-computer control with
no loss in update rate of any given receiver." A special `Fast Bird
Bus' (FBS), an RS-422/485 compatible, serial bus has been designed to
accomodate data transmission rates between 345 and 625 kBaud.

While this system may become a serious competitor for opto-electronic
systems, it is a w i r e d system, thus entailing well-known problems
in biomechanical movement analysis. However, the direct availability of
6 d.o.f. data for each receiver in r e a l - t i m e might affect the
balance of choice in this area, especially since only receiving equipment
is worn by the subject. Thus, power requirements in a telemetric configu-
ration not requiring trailing cables would be modest.

However, there is a potential problem. Systems such as the 3SPACE
ISOTRACK and Tracker, and its newly announced competitor are sensitive
to metallic structures close to the path between transmitter and recei-
ver. In an open-air environment, metallic effects may be easily avoided,
but many existing movement analysis facilities contain metallic compo-
nents. It should be interesting to compare the `Flock of Birds' from
this point of view with opto-electronic systems for multi-channel move-
ment measurement.

Pricing details will be announced next month, I understand.

Herman J. Woltring, Eindhoven/NL.