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Is this the smallest Robot Ever?- Amazing that someone made it...‏

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Is this the smallest Robot Ever?- Amazing that someone made it...‏

Mensagem  joseflor em Sab 27 Jun 2009 - 13:55

Hi there, I came across this webpage
a while ago when I was looking for information
on PID (Proportional Integral Differential) controllers.

http://elm-chan.org/works/ltc/report.html


PID by the way is an essential mathematical technique
which allows "real" control systems to work in the way
that you expect them to work!

Before PID was invented control systems would go wild
and oscillate because the operating electronics would
over or under compensate. Using the PID equations
allows the system to compensate by controlling and
measuring three parameters and it effectively creates
a smoothing filter optimized for motor control.

Three parameters are used:

  • Kp - proportional gain value.
  • Kd - Differential gain value.
  • Ki - Integral gain value.


A simple view of the PID method is:

1. Find the error i.e. the difference between where
the system should be and where it is now and multiply
by Kp.

2. Find the difference between the current error and the last
error and multiply by Kd - this is the difference or differential.

3. Calculate an average of previous errors and multiply by Ki
this is the integral or sum of previous errors (averaged).

These three parameters achieve three things:

1. Kp - moves the motor directly in response to a linear error.

2. Kd - measures the last error difference and will create a
larger compensation value i.e. it will accelerate the motor quickly
if there is a large error.

3. Ki - the running average smooths out the effect of step responses
so it acts as a dampening factor to control overshoot and ringing.

Add these three terms together and scale and the generate the
output motor control based on this value (hint use a PWM signal).


As you can see these equations are ideal for control and
measurement using a microcontroller.

The mini robot projects uses them to keep the robot
from going unstable and missing the track although it does
not use the Ki parameter.




Neat Huh?

Note: The videos are also at the bottom of the page
in the link http://elm-chan.org/works/ltc/report.html
and remember to check out the video that does not
have the microcontroller using Kd parameter - it
goes haywire!


It's also a clever use of those miniature motors that
you find in mobile phones or pagers (the ones that
vibrate the handset on silent alert).

If you're looking for a lot more detail on PID control
then this is a good place to look:

http://www.jashaw.com/pid/tutorial

Till next time.

_________________
Happy soldering!
José Flor - OzFlor
Venda de componentes de electrónica
Loja EBR (Eletrônica BRasil)
Fórum oficial de electrónica de José Flor - OzFlor

joseflor
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