ABB CM30 User Manual page 45

ControlMaster CM30 and CM50
Universal process controllers,
...Control / ...Loop 1 (2) Control / ...Adaptive Control
Mode
Critical Gain 
Critical Period
Reset
Misc.
Loop Monitor
RSP Step Action
No P&D
P&D
IM/CM/ED–EN Rev. B
1 1
/ and / DIN
4 2
Turns adaptive control On or Off.
Normally set by the autotuner, but can be set manually if necessary. A valid setting must be
entered (either manually or using Autotune [see page 19) for the adaptive controller to
function.
Manual Calculation of Critical Gain and Critical Period
1 Put the controller into Manual control mode.
2 Set the integral and derivative terms to off.
3 Set the Proportional Band to 100 % – see page 20.
4 Adjust the controller's output signal manually until the process variable equals the
setpoint.
5 Read the current controller output value.
6 Set the controller's Manual Reset parameter to the value of the output – see page 20.
7 Put the unit into Auto control mode.
8 Change setpoint by a few percent (as the setpoint is changed in each iteration, keep the
value relatively constant by alternating increases with decreases).
9 Observe the process variable and the output signal to see if the system oscillates.
10 If the system oscillates with a decreasing amplitude, decrease the proportional band
and go to step 8.
11 If the system oscillates with a increasing amplitude, increase the proportional band and
go to step 8.
12 If the system oscillates with a constant amplitude, read the controller's oscillation period
time. This is the setting of the Critical Period parameter.
Read the proportional band (Pb) setting and calculate the Critical Gain (Kc) as follows:
Resets the adaptive controller's internal parameters and process model to their default
settings.
A control loop performance monitor can be enabled to monitor the control loop for abnormal
oscillations and creates a diagnostic warning if any occur. This function is automatic and
does not require any user set up after it is activated.
Remote setpoint step behavior. Determines how the PID (see page 20) algorithm responds
to a step change in the remote setpoint value.
During a step change in the remote setpoint value, the integral term only is applied.
During a step change in the remote setpoint value proportional, integral and derivative terms
are applied.
7 Advanced Level
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