Honeywell 900 User Manual page 164

Loops
Loop Setup
Item
Accutune III Type
Switch Tune Set
PV Adaptive Tuning
Tuning Criteria
152
DISABLE - Disables ACCUTUNE III.
CYCLE TUNING - Tuning parameter values are derived from the process response
to the resultant action of causing the PV to oscillate about the Setpoint value. This
tuning method uses the measured ultimate gain and period to produce tuning
parameter values. Cycle tuning does not distinguish between process lags and
always results in gain based on PV amplitude and calculates values of Reset and
Rate based on time of the SP crossings (The Reset value is always 4x the Rate
value.) This method does not require a stable process initially and the process may
be moving.
SP TUNING – Setpoint Tuning based on the process response to a Setpoint change.
When initiated, the control loop is put into an initial temporary manual state until the
process characteristics are identified. This period may last up to a minute. During
this time the Tune status shows Not Ready, and then an initial output step is made
using the preconfigured size and direction parameters along with the preset output
value. The resultant process action is used to determine the tuning parameters and
once the process identification has completed, the loop is returned to automatic
control.
Tune Set 1 uses Gain #1, Rate #1, and Reset #1.
Tune Set 2 uses Gain #2, Rate #2, and Reset #2.
Tuning method that continuously learns the process as PV deviations are observed
and adapts the tuning parameters to the process response.
DISABLE - Disables PV Adaptive tune.
ENABLE - This method adapts a tuned process to changing system characteristics
over time, when the PV deviates from the Setpoint by a certain amount for any
reason. This method adapts a tuned process to changing system characteristics
over time. It operates by observing a previously tuned process for changes in the
system such as changes in deadtime or other process characteristics that can make
a tuned process become unstable, unresponsive or over responsive. When the PV
deviates from the SP by a certain amount for any reason, the adaptive tuning
algorithm becomes active and begins to observe the resulting PV action. If the
process becomes unstable and oscillates, PV Adaptive Tuning eventually brings the
process into control by retuning parameter values (as needed) using a systematic
approach defined by an expert based method of tuning rules. Should the process not
oscillate but be observed as too fast or sluggish, a different expert rules set is
applied to result in the slowing down or speeding up of the process by adjusting
certain tuning parameter values. This method continuously learns the process as PV
deviations are observed and adapts the tuning parameters to the process response.
NORMAL - Very conservative tuning designed to calculate critically damped tuning
parameter values that produce no overshoot.
FAST - More aggressive tuning than Normal. Designed to calculate under damped
parameter values providing faster control to the setpoint but may have some
overshoot.
900 Control Station User Guide
Description
Revision 9
May 2014