Help Needed Regarding GARIC Architecture (fwd)

From: Vijay Patil (vcpatil@me.iitb.ac.in)
Date: Mon Nov 05 2001 - 20:22:45 MET

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Hi,
I need little help, you would be in better position to answer my questions
if you have read following papers.

1.Berenji, Khedkar, "Learning and Tuning FLCs through reinforcements"
IEEE Tran. on NN, vol 3, No 5, Sept 1992.
2.Berenji, Khedkar, "Using FL for performance evaluation in RL"
IJAR, 1998.

I am planning to use GARIC for Traffic Signal Control Problem, where
{APP, QUE}------>[ASN]----->{EXT}

Action Selection Net(ASN) maps input vector of 'No of Approching
Vehicles(APP)' and 'Queue Lenght (QUE)' to 'Extension to Green Light
(EXT) in seconds'

ASN is represented as neuro-fuzzy system. Now I want to train ASN.
But unlike concept of avoiding *binary* failure signal in [1] what I need
to do is minimize a paramter(DELAY of vehicles in secs) associated with
the traffic system. I have NOT used AEN and SAM.
So in short, I do not have desired EXT, nor there is anything like binary
failure signal.Instead, for each action(EXT) taken by ASN, I have DELAY,
in seconds available.
Function, f(EXT,.,.,.) = DELAY
The function f is NOT known. So I tried to use "Approximate Derivative" in
the steepest descent algorithm, as follows:
-------------------------------------------
To minimize DELAY, calculate approx. der:
sgn{DELAY(t) - DELAY(t-1)} / {EXT(t) - EXT(t)}
backpropagation
wt./paramter update
end
------------------------------------
But this is not working simply because in cases where denominator is large
above formula gives wrong picture.

So finally, questions:
1.Should I go for AEN and SAM as proposed in [1],[2].?
2.Should I replace binary failure signal by DELAY.?
3.Did you face analogous problems?

Even if I decide to go for AEN, formula (2) on page 134 of [2],
Partial Derivative_of_v_w.r.t_F = sgn{v(t) - v(t-1)} / {F(t) - F(t)},
is *ambiguous* as v is dependent on both input and paramters, both of
which varies with time and with updates in paramters.

Best Regards....

________________________________________________Vijay Patil__________

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