WEG CFW300 V1.3X, Руководство по программированию

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SoftPLC
CFW300 | 18-5
18
Table 18.3: Suggestions for the PID controller gain settings
Quantity Sampling Time P934
Gains
Proportional P931 Integral P932 Derivative P933
Pressure in pneumatic system 0.10 s 1.00 5.00 0.00
Flow in pneumatic system 0.10 s 1.00 5.00 0.00
Pressure in hydraulic system 0.10 s 1.00 5.00 0.00
Flow in hydraulic system 0.10 s 1.00 5.00 0.00
Temperature 0.50 s 2.00 0.50 0.10
Putting into Operation
Check the state of the PID controller application in parameter P900. Value equal to 4 indicates the application is
already in operation. Value equal to 3 indicates the application is stopped; therefore, it is necessary to change the
command value for the SoftPLC in parameter P901 to 1 (execute application). Value different from 3 or 4 indicates
the application cannot go into operation. For further details, refer to the CFW300 SoftPLC manual.
1. Manual Operation (DI2 open): keeping DI2 open (Manual), check the indication of the process variable on
the HMI (P916) based on an external measurement of the sensor signal (transducer) in analog input AI1.
Then, changes the manual setpoint value of the PID controller (P918) until reaching the desired process variable
value. Check if the control setpoint value (P911) is set to this value, and then put the PID controller into the automatic
mode.
NOTE!
The PID controller only begins the speed regulation when the motor reaches the minimum speed
programmed in P133, as it was configured to operate from 0.0 to 100.0%, where 0.0% corresponds
to the minimum speed programmed in P133, and 100.0% corresponds to the maximum speed
programmed in P134.
2. Automatic Operation (DI2 closed): close DI2 and make the dynamic adjustment of the PID controller, that
is, of the proportional (P931), integral (P932) and derivative (P933) gains, checking if the regulation is being
done correctly. In order to do so, just compare the control setpoint and the process variable and check if the
values are close. Also check how fast the motor responds to the oscillations of the process variable.
It is important to point out that the setting of the PID controller gains is a step that requires some attempt and
error procedure to reach the desired response time. If the system responds quickly and oscillates close to the
control setpoint, then the proportional gain is too high. If the system responds slowly and it takes a long time to
reach the control setpoint, the proportional gain is too low and must be increased. In case the process variable
does not reach the required value (control setpoint), the integral gain must be set then.
18.2.2 Academic PID Controller
The PID controller implemented on the CFW300 is academic. See below the equations that characterize the
Academic PID controller, which is the base of this function algorithm.
The transfer function in the frequency domain of the Academic PID controller is:
y(s) = Kp x e(s) x 1 + 1
sTi
+ sTd
Replacing the integrator by a sum and the derivative by the incremental quotient, we obtain the approximation for
the discrete (recursive) transfer equation presented below:
y(k) = i(k-1) + Kp[(1 + Ki.Ta + Kd/Ta).e(k) – (Kd/Ta).e(k-1)] x 10