farjamit@eecs.cs.pdx.edu (Tom Farjami) (04/11/91)
Greetings :
I got couple of emails regarding the use of motion
detection for Speech recognition. The question that was
asked was," would this circuit arrangement be speaker
independent ?". I have expanded on this aspect.
I am a Graduate student in the EE department here in
Portland State University. Currently the title of my thesis
is "a biologically motivated model for motion detection
implemented in VLSI". I have gone through one round of
fabrication of this IC and the preliminary results seem
promising.
Here is a description of the project. I am working on
design and fabrication of a CMOS motion detector IC that I
have classified as being fuzzy. It has 10 digital inputs and
an analog output. A strong voltage on the output ( near VDD)
means that majority of the inputs were fired in the pre-
ferred direction, otherwise output is silent. There is no
feedbacks and therefor no neural-net like back props in this
circuit. It detects motion in real time; as long as input
signal's frequency is within few hundred to few kilo hertz.
Circuit is biologically motivated and operates in subthres-
hold.
During my graduate studies, I have been trying to
answer the following question,"Basically what are some of
the applications of this circuit in real life ?". I thought
of waveform detection in scopes, pattern recognition and
even speech recognition myself. You might ask,"How would
that be?". Consider the following. If inputs of the motion
detector came from a set of comparators such that all of the
comparators were comparing the same analog input signal (
say a speech signal) against constant (programmable) vol-
tages. That is each comparator has a different reference
voltage but takes in the same analog signal as other com-
parators do. Now if the analog waveform matched the wright
pattern in the preferred direction, which is also our time
domain, motion detector will turn on and we have pattern
detection. Of-course for this I need more that 10 inputs,
perhaps hundreds to give me high resolution and a state
machine plus a A/D converter to program my reference vol-
tages with; but this can be done. The power of this circuit
arrangement is that it doesn't do an exact fitting match of
the input waveform with the reference voltages. But rather
it does a shape fitting match. Even more power-full is the
fact that notion of time is removed from the reference vol-
tages; that is input waveforms of different frequencies and
phases can be matched against the reference pattern as long
as input waveforms have the same shape and a frequency range
of few 100Hz to a few 10 KHz . I believe this characteristic
is important if we are doing speech recognition and we want
speaker independent matching.
I believe Motion Detector project is very interesting;
an extension of it could be an even more interesting project
capable of performing a very complex task at a striking
ease.
All comments will be appreciated.
Regards,
Tom Farjami
farjamit@eecs.ee.pdx.edu
April 10, 1991