INFICON IC6 Thin Film Deposition Controller - Manual (Page 321)

16 - 13
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IC6 Operating Manual
Figure 16-7 Response of process to an open loop step change
(At t=0 control signal is increased)
A controller model used extensively is the PID type, shown in Laplace form in
equation [9] .
[9]
Where
 M(s) = manipulated variable or power
 K
c
= controller gain (the proportional term)
 T
i
= integral time
 T
d
= derivative time
 E(s) = process error
Figure 16-8 represents the controller algorithm and a process with first order lag
plus a dead time. The process block implicitly includes the dynamics of the
measuring devices and the final control elements, in our case the evaporator power
supply. R(s) represents the rate setpoint. The feedback mechanism is the error
generated by the difference between the measured deposition rate, C(s), and the
rate set point, R(s).
T
1
= t
(0.632)
- L
K
p
= (Change in Output) / (Change in Control Signal)
Point of
Maximum
Slope
1.00 K
p
K
p
0
L
t
(0.632)
Time, t
0.632
M s   K
c
1
1
T
i
s
------- T
d
s + +
 
  Es
=