West Control Solutions N8800 - Manual (Page 18)

The controller attempts to calculate the optimum control parameters from the
process response. If this is done successfully, the optimized parameters are taken
over and used for line-out to the set-point.
With a 3-point controller, this is followed by “cooling”.
After completing the 1st step as described, a correcting variable of -100% (100%
cooling energy) is output from the set-point. After successfull determination of
the “cooling parameters”, line-out to the set-point is using the optimized
parameters.
Pulse attempt after start-up
Condition: - tunE = 1 and sufficient set-point reserve provided.
The controller outputs 0% correcting variable or Y.Lo and waits, until the process
is at rest (see start conditions page 16)
Subsequently, a short pulse of 100% is output (Y=100%) and reset.
The controller attempts to determine the optimum control parameters from the
process response. If this is completed successfully, these optimized parameters
are taken over and used for line-out to the set-point.
With a 3-point controller, this is followed by “cooling”.
After completing the 1st step as described and line-out to the set-point, correcting
variable "heating" remains unchanged and a cooling pulse (100% cooling energy)
is output additionally. After successful determination of the “cooling
parameters”, the optimized parameters are used for line-out to the set-point.
Optimization at the set-point
Conditions:
w A sufficient set-point reserve is not provided at self-tuning start (see page 17).
w tunE is 0 or 1
w With Strt = 1 configured and detection of a process value oscillation by
more than ± 0,5% of (rnG.H - rnG.L) by the controller, the control
parameters are preset for process stabilization and the controller realizes an
optimization at the set-point (see figure “Optimization at the set-point”).
w when the step attempt after power-on has failed
w with active gradient function ( PArA/ SETP/ r.SP≠ OFF), the set-point
gradient is started from the process value and there isn't a sufficient set-point
reserve.
Operation
Self-tuning 18 8800 process controller