Auto Tuning; Auto Tuning Procedure - Honeywell SmartLine RMA800 User Manual

Auto tuning

Cycle tuning
The PID block supports the Cycle tuning algorithm. In Cycle tuning, the tuning parameter values are
derived from the process response to the resultant action of causing the PV to oscillate about a SP
value. The tuning method uses the measured ultimate gain and period to produce tuning parameter
values, by using the relationship developed by Ziegles Nichols equations. Cycle tuning does not
distinguish between process lags and always results in gain based on PV amplitude, and calculates
the values of Reset and Rate based on time of the SP crossings using a fixed ratio of 4 to 1. Initially,
this method does not require a stable process. Cycle tuning is applicable to Three Position Step
control, and is used for integrating process.

Auto tuning procedure

There are nine parameters applicable for auto tuning: AT_TYPE, TUNING_CRITERIA,
TUNE_REQ, ATI, AT_MODE, AT_ERR, AT_GAIN, AT_RESET, and AT_RATE.
AT_Type
There are two types of selections, namely Disable and Cycle Tune. When Disable is selected,
AT_MODE becomes inactive. When Cycle Tune is selected, AT_MODE becomes AT Ready.
TUNING_CRITERIA
There are two types of tuning criteria available for selection: Normal and Fast.
•
NORMAL - Conservative tuning designed to reduce overshoot as compared to FAST.
•
FAST - Aggressive tuning designed to provide quarter-dampened response.
TUNE_REQ
TUNE_REQ can be turned ON only in the following modes, namely AUTO, CAS, RCAS, and
ROUT. The ATI value becomes 1, and AT_ERROR shows the status as Run, this shows that auto
tuning is in progress.
If AT_ERROR shows OK, auto tuning is successful. AT_GAIN, AT_REST, AT_RATE gets
updated automatically and same values are copied to GAIN, RESET and RATE respectively.
Page 58 Foundation Fieldbus RMA803 Remote Indicator User's Guide Revision 4