<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<meta content="text/html;charset=ISO-8859-1" http-equiv="Content-Type">
<title></title>
</head>
<body bgcolor="#ffffff" text="#000000">
Krishna,<br>
My apologies for the delay in getting back to you about this
question. I needed to check with the master of PID controllers in
TRNSYS (Michael Kummert) before replying coherently. There are two ways
that you can use Type23 in a cooling mode application. If you have a
cooling case in which (for example) you are using a PID as a flow
controller to keep a temperature below some desired set point then you
can set Type23's proportional gain constant to a negative value in
which case the PID will increase flow as the monitored temperature gets
higher and higher. In this case minimum control signal (parameter 4)
should be zero and the maximum control signal should be a positive
value. <br>
<br>
In another case, you might want your PID to provide both heating and
cooling. In this situation, the control signal's magnitide should
increase as you get farther and farther from the setpoint but the sign
of the control signal should change depending on whether you are above
or below the setpoint. In this case, you set the proportional gain to a
positive value but you allow the Type23 calculated control signal to
vary between a negative and a positive number. I will send you an
example that Michael was kind enough to generate. I do not want to clog
up everyone's InBox so I will send it in a seperate email.<br>
Kind regards,<br>
David<br>
<br>
Krishna wrote:
<blockquote cite="mid002201c59900$00b24520$1900000a@Sim" type="cite">
<meta http-equiv="Content-Type" content="text/html; ">
<meta content="MSHTML 6.00.2900.2668" name="GENERATOR">
<style></style>
<div><font face="Arial" size="2">I am having to reverse the control
signal (1-control signal) for controlling the chilled water flow with a
PID controller.</font></div>
<div><font face="Arial" size="2">Could any one please let me know if
this is the right way to do it.</font></div>
<div><font face="Arial" size="2">thankyou, </font></div>
<div><font face="Arial" size="2">Krishna</font></div>
<pre wrap="">
<hr size="4" width="90%">
_______________________________________________
TRNSYS-users mailing list
<a class="moz-txt-link-abbreviated" href="mailto:TRNSYS-users@engr.wisc.edu">TRNSYS-users@engr.wisc.edu</a>
<a class="moz-txt-link-freetext" href="https://www.cae.wisc.edu/mailman/listinfo/trnsys-users">https://www.cae.wisc.edu/mailman/listinfo/trnsys-users</a>
</pre>
</blockquote>
<br>
<pre class="moz-signature" cols="72">--
**
David BRADLEY
Solar Energy Laboratory
University of Wisconsin - Madison
1500 Engineering Drive
Madison, WI 53706
United States
Ph: +1 608 263 1589
Fax: +1 608 262 8464
Email: <a class="moz-txt-link-abbreviated" href="mailto:dbradley@engr.wisc.edu">dbradley@engr.wisc.edu</a></pre>
</body>
</html>