Chapter 7. Usage of Various Functions
7-31
Examples of process control by forward and reverse actions
(14) PID Algorithm
In GM7U, two type of PID algorithm is available, The velocity form(Speed) and positioning form.
Velocity form(Speed) operates incremental manners. Namely, It calculates the change(∆ n) required from
previous manipulate value(MVn-1), But positioning form calculates an absolute manipulate value(MVn) every
sampling steps. Generally, The velocity form is suit for the system which’s load change is slow like temperature
control system, and positioning form is useful for system which’s load change is fast.
b) PID Auto Tuning Parameter settings
Scan time① (%MW4700)
Scan Time is the period of reading data (sampling), and 10 times scaled up for more precious operation.
The range of sampling time is 0.1 ~ 10 seconds, and actual input range is 0 ~ 100.
Time
Temperature
Time
Tem
erature
SV
SV
PV
PV
Reverse action (for cooling)
Forward action (for heating)
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