[Eetu Pikkarainen 2018-03-26_10:09:46 UTC]
Sorry for too quickly written and sent message. There was such typos that I put it again here and continue a little:
Powers differentiates three systems: Z is causal stimulus-response system where output does not affect input; P and N are (respectively)
positive and negative feedback systems. Braitenberg 1 is not Z system because its output consistently affects its input. Whether it is N or P depends on whether the heat source happens to be in front or back of it. If the heat source is in the back side then
its output movement decreases the warmth input and thus it controls the warmth with the reference value where there is so cold that its motor stops. I would not say that it controls for distance but only for warmth (or rather for coldness). If the warmth source
happens to be in its front side then it is positive feedback system and does not control.
I agree that Braitenberg vehicles seem not to be designed with the idea of control in mind. That the variants of Braitenberg 2 are named
Coward and Aggressive hints that the designer has had rather a positive feedback in his mind. (The home link in the site does not work, the index of pages about different vehicles is
http://www.bcp.psych.ualberta.ca/~mike/Pearl_Street/Margin/Vehicles/ )
···
Eetu
From: Eetu Pikkarainen eetu.pikkarainen@oulu.fi
Sent: Monday, March 26, 2018 11:14 AM
To: csgnet@lists.illinois.edu
Subject: Re: More Lego ev3 demos
[Eetu Pikkarainen 2018 03 26]
Powers differentiates three systems: Z is causal stimulus-response system where output does not affect input; P and N are positive and negative feedback
systems. Braitenberg 1 is not Z because its output consistently affects its input. Whether it is N or Z depends on whether the heat source happens to be in front or back of it. If the heat source is in the back side then its output movement decreases its warmth
input and it controls the warmth with the zero value where there is so cold that its motor stops. I would not say say that it controls for distance but onlu for warmth (or rather coldness).
Eetu
Kohteesta: Rupert Young
Lähetetty: sunnuntai 25. maaliskuuta klo 19.39
Aihe: Re: More Lego ev3 demos
Vastaanottaja:
csgnet@lists.illinois.edu
[From Rupert Young (2018.03.25 17.40)]
(Rick Marken 2018-03-19_10:12:19]
RM: I’m sorry. I don;t remember which vehicle was which or where they were. But the vehicle is a control system if it controls. …
RY: The place to start is vehicle 1 as the conceptualisation of this permeates the remainder of the vehicles,
http://www.bcp.psych.ualberta.ca/~mike/Pearl_Street/Margin/Vehicles/Vehicle.1.html
RY: It is a one-dimensional system with a single motor and a single (temperature) sensor. The motor speed is a direct function of the temperature. So, it goes slowly in cold areas
and faster in hotter areas. What is this controlling, would you say?
RM: This vehicle NOT a control system but it is a closed loop system. It’s not a control system because the feedback effect of output on input is positive. So it is an example of
what Powers (1978) called a P-system.
Yes, it seems that way. (Is this reference, “Quantitative Analysis of Purposive Systems etc”?). I’d call it a continuous stimulus-response system. There
is no explicit reference and, hence, no apparent error to minimise or goal to achieve. I think the effect of the output on input is sometimes positive and sometimes negative (if the forward temperature gradient is downwards), it’s entirely dependent on the
environment.
Given that this system is the conceptual foundation for all other Braitenberg’s vehicles it is questionable whether any of them are control systems. Perhaps,
some are, but that is likely to be more by accident than design. It would be interesting if people could identify which systems within Braitenberg’s vehicles are controlling perceptions.
You could easily turn it into an N-system (a control system) by having motor speed be negatively related to sensed temperature. Then the car would control its distance from heat sources,
the distance being proportional to the temperature that produces 0 sensory signal and, hence, no movement toward or away from the heat source.
To do that you’d need to sense the temperature gradient wouldn’t you? Also to control distance it would need to perceive distance wouldn’t it? Isn’t the
only temperature that produces a sensory signal of 0 a temperature of 0? Did you mean error signal?
Regards,
Rupert