--===============1958804819==
Content-Type: text/plain; charset="gb2312"
Content-Transfer-Encoding: quoted-printable
X-MIME-Autoconverted: from 8bit to quoted-printable by pch.mit.edu id n1L0qnZW011129



  I started looking at
temperature control inside a thermal chamber.  That tank is actually a
first-order system with some possible disturbances from different input a=
nd
ambient temperatures. Also a temperature sensor can be considered to have=
 a
linear, very small time constant (or: high bandwidth). Thus, the system s=
hould
be stable by its nature. Since not much compensation might be needed, man=
y
people just use PID to tune up the time response of a temperature control=
 system.



   Recently I read a book
written by Robert Pease, called "analog circuits, world class
designs". The front chapters talked about how to realize feedback control
loops by using a series of opamps, caps and resistors. It makes so much s=
ense
so that I found some link between all the control courses I took to the r=
eal
world controls. =20



   As to the PID control, I
found some modern designs simply use A/D, D/A, and a microprocessor, and =
let
the software guys to do the math (which takes time since microprocessor c=
annot
do calculus that easy, also discrete control involves different math). Th=
ere is
also a more analog, or old-fashioned way, like Bob did in the book, was j=
ust to
use many discrete semiconductors. (Although I guess a micro is always nee=
ded
somewhere)



   I wonder which way might
be more appropriate? In an analog way, certainly a hardware guy can take
control of most things; he can also get an easier and more direct continu=
ous
system model. But a digital way seems like  easy-configurable and
adjustable, but the credit won't be mostly mine anymore :)

_________________________________________________________________
MSN=D0=C2=B0=E6=D4=DA=CF=DF=C9=E7=BD=BB=CD=F8=C2=E7=A3=AC=D3=EB=C4=FA=B5=C4=
MSN=BA=C3=D3=D1=B8=FC=C8=AB=C3=E6=BB=A5=B6=AF=A3=A1
http://im.live.cn/msn9/=20
--===============1958804819==
Content-Type: text/plain; charset="us-ascii"
MIME-Version: 1.0
Content-Disposition: inline
Content-Transfer-Encoding: 7bit

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist

--===============1958804819==--