Manual 35018V1
505XT Digital Control System for Steam Turbines
Woodward
188
Figure 5-35. Optimization Routine Overview Trend
Analysis Mode
During the Analysis Mode, the optimizer begins by making small actuator movements which progressively
increase until the measured process signal movement can be differentiated from signal noise. The initial
movement direction (up or down) depends on system conditions. Once there is enough process signal
movement, the optimizer begins moving the actuator up and down until the process signal moves beyond
the +/- the threshold values (calculated from signal noise) and performs the system analysis to calculate
gains.
On the front panel, the status will progress through the following steps during the Analysis Mode:
OPID
Enabled/Settling
Analysis
Movement
Movement to Thresholds
Calculating
Gains
Setpoint Step Mode
Once new gains have been calculated for P, I, and D the PID will control at the setpoint using the newly
calculated gains. The routine then performs setpoint step tests to validate the system response.
During the Setpoint Step Mode there are 4 setpoint step tests:
1) Step the setpoint up or down (amount depends on system noise, but less than the
Process Limit
configured). Whether it moves up or down depends on the sign of the
Process Limit
.
2) Step the setpoint back to the initial setpoint
3) Step the setpoint by a higher amount than the first setpoint step test
4) Step the setpoint back to the initial setpoint
At any stage in this mode, if a fault occurs, the optimizer will abort and change the PID gains from the
calculated values back to the initial values.
On the front panel, the status will progress through the following steps during the Setpoint Test Mode:
Settling at Setpoint
Step Tests with OPTI Gains
System
Settling
Complete – Using New Gains