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1436 cPos
Integral-actioncomponent(Icomponent)Ki:
The I component Ki changes the controller regulation ratio
continuously until the actual value reaches the set value.
The regulation ratio will be integrated upwards or downwards
as long as a system deviation exists. The inuence of the I
component will become larger the longer a system deviation
exists. The shorter the reset time Tn and the larger the system
deviation, the stronger (faster) the eect of the I component.
The I component hinders a constant system deviation.
Reset time Tn:
The reset time Tn determines the duration how long a system
deviation is adjusted.
If a high value is preset for the reset time T
n this means a small
inuence of the I component and vice-versa.
During the reset time T
n the controlled variable change caused
by the P component is added again.
Thus there is a xed relationship between the P component
and the I component. If the P component is thus changed, the
time response changes too if the Tn value remains constant.
Ki=1/Tn
16.4 Adaptation of the controller to the controlled
system
Optimisation of the controller:
In order to achieve good behaviour of the control circuit it is
necessary to adapt the controller to the process.
Good valve behaviour, for instance, can be quick adjustment
of maximum power for pre-shooting or non-overshooting-free
adjustment of maximum power if the adjustment of power takes
longer.
The optimum adjustment parameters must be determined
"manually" by trial and error through experimentation or rule of
thumb.
Explanation of parameters of GEMÜ 1436 cPos:
Proc P: K
P
Proc I: Tn
Proc D: KD
Proc T: Tv
Interpretation of the controller parameters according to
Ziegler-Nichols:
The following process is intended to help to adapt the
controller to the controlled system (however this process can
only be implemented on controlled systems where it is possible
to let the controlled variable oscillate of its own accord).
● Set the values for K
p (ProcP) and Tv(ProcT) to their
minimum and the T
n(ProcI) value to 0 (this leads to the
smallest possible eect of the controller).
● Enter the desired set value manually in manual mode.
● Slowly increase K
p(ProcP) (decrease Xp), until the
controlled variable starts to oscillate harmoniously. Ideally
the control circuit should be stimulated to oscillate by erratic
set value changes during the K
p adjustment.
● Note the K
p value thus obtained as a critical proportional
action factor Kp,krit.
● Following this, determine the duration of an oscillation
as T
krit. If possible, use a stopwatch to measure several
oscillations and use the arithmetic mean as Tkrit.
● Use the values thus determined for K
p,krit and Tkrit to
calculate the missing Kp, Tn and Tv parameters according to
the following table.
Kp = Proc P Tn = Proc I Proc D Tv = Proc T
P 0.50 x K
p,krit 0 0 0
PI 0.45 x K
p,krit 0.85 x Tkrit 0 0
PID 0.59 x K
p,krit 0.50 x Tkrit 0.59 x Kp,krit 0.12 x Tkrit
● If necessary, re-adjust the Kp and Tn values a little until the
control system shows satisfactory behaviour
16.5 DierentialequationfortheGEMÜ1436cPos
−+
+∗=
∫
dt
dy
*ProcTv
dt
dx
*ProcDdt x*
ProcI
1
xProcPy
d
dd
16.6 Eectsofthecontrolparametersonthe
control system
Proc P:
Larger:
The controller controls faster, however it tends
to oscillate and controls less accurately. The set
value is achieved in larger steps by increasing the
manipulated variable
Smaller:
The controller controls more slowly as the set
value is achieved in smaller steps by decreasing
the manipulated variable. Control is more precise.
Proc I:
Larger:
The controller reacts more slowly to actual value
changes. Proc I should be increased for actual
value sensors with relatively slow output signals.
Smaller:
The controller reacts faster to actual value
changes.
Proc D:
Larger:
Slows down the manipulated variable y when
moving to the set value. Control is slower.
Smaller: Set value is achieved faster.
Proc T:
Larger:
The system deviation has a longer effect although
set value = actual value
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