West Control Solutions N8800 - Manual (Page 25)

3.7 Second PID parameter set
The process characteristic is frequently affected by various factors such as
process value, correcting variable and material differences.
To comply with these requirements, the 8800 process controller can be switched
over between two parameter sets.
Parameter sets PArA and PAr.2 are provided for heating and cooling.
Dependent of configuration ( ConF/LOG/Pid.2), switch-over to the second
parameter set ( ConF/LOG/Pid.2) is via one of digital inputs di1, di2, di3,
key è or interface (OPTION).
g
Self-tuning is always done using the active parameter set, i.e. the second
parameter set must be active for optimizing.
Operation
8800 process controller 25 Second PID parameter set
Formulas
K = Vmax * Tu controller behavior Pb1 [phy. units] td1 [s] ti1 [s]
With 2-point and
3-point controllers,
the cycle time must be
adjusted to
t1 / t2 ≤ 0,25 * Tu
PID 1,7 * K 2 * Tu 2 * Tu
PD 0,5 * K Tu OFF
PI 2,6 * K OFF 6 * Tu
P K OFF OFF
3-point-stepping 1,7 * K Tu 2 * Tu
Parameter adjustment effects
Parameter Control Line-out of disturbances Start-up behaviour
Pb1 highe
r
increased damping slower line-out slower reduction of duty cycle
lower reduced damping faster line-out faster reduction of duty cycle
td1 highe
r
reduced damping faster response to disturbances faster reduction of duty cycle
lower increased
damping
slower response to
disturbances
slower reduction of duty cycle