Emerson PaCSystems VersaMax Series, Руководство пользователя

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User Manual Chapter 14
GFK-1503F Jan 2020
PID Built-in Function Block 268
Kp = 0.9/(R * Tp) = 0.9 * Tc/(K * Tp) Ki = 0.3 * Kp/Tp
For Proportional, Integral and Derivative control, use:
Kp = G/(R * Tp) where G is from 1.2 to 2.0
Ki = 0.5 * Kp/Tp
Kd = 0.5 * Kp * Tp
3. Check that the Sample Period is in the range
(Tp + Tc)/10 to (Tp + Tc)/1000
14.6.3 Ideal Tuning Method
The Ideal Tuning procedure provides the best response to SP changes that are delayed only
by the Tp process delay or dead time.
1. Determine the three process model parameters, K, Tp and Tc for use in estimating
initial PID loop gains.
2. Calculate Kp, Ki, and Kd as follows:
Kp = 2 * Tc/(3 * K * Tp)
Ki = Tc
Kd = Ki/4 if Derivative term is used
3. Once initial gains are determined, convert them to integers.
4. Calculate the Process gain, K, as a change in input PV Counts divided by the
resulting output step change in CV Counts. (Not in process PV or CV engineering
units.) Specify all times in seconds.
5. Once Kp, Ki and Kd are determined, Kp and Kd are multiplied by 100 while Ki is
multiplied by 1000. The resulting values are entered into the corresponding
reference array word locations.
14.6.4 Example
The following PID example has a sample period of 100 ms, a Kp gain of 4.00 and a Ki gain of
1.500. The set point is stored in %R0001, the control variable is output in % AQ0002, and the
process variable is returned in %AI0003. CV Upper and CV Lower Clamps must be set, in this
case to 20000 and 4000, and an optional small Dead Band of +5 and -5 is included. The 40-
word reference array starts in %R0100. Normally, user parameters are set in the reference
array, but %M0006 can be set to reinitialize the 14 words starting at %R0102 (word 3) from
constants stored in logic (a useful technique).
The block can be switched to Manual mode with %M1 so that the Manual Command, %R113,
can be adjusted. Bits %M4 or %M5 can be used to increase or decrease %R113 and the PID
CV by 1 every 100 ms solution. For faster manual operation, bits %M2 and %M3 can be used
to add or subtract the value in %R2 to/from %R113 every CPU sweep. The %T1 output is on
when the PID is OK.