Automating Manufacturing Systems - Process Control and ...

plc pid - 25.22
4.
Assume the values:
update
N7:0 = Analog input value
N7:1 = Analog output value
N7:2 = Setpoint
MOV
Source F8:4
Dest F8:5
MOV
Source F8:3
Dest F8:4
SUB
Source A N7:2
Source B N7:0
Dest F8:3
F8:0 = Kp
F8:1 = Kd
F8:2 = Ki
F8:3 = ei
F8:4 = ei-1
F8:5 = ei-2
F8:6 = T (Scan Time)
CPT
Dest F8:10
Expression
CPT
Dest F8:11
Expression
CPT
Dest F8:12
Expression
"F8:0 + F8:2 * F8:6 + F8:1 | F8:6"
"-F8:0-2*F8:1|F8:6"
"F8:1 | F8:6"
CPT
Dest N7:1
Expression
"N7:1+F8:3*F8:10+F8:4*F8:11+F8:5*F8:12"
5. Logical control is more popular because the system is more controllable. This means either
happen, or they don’t happen. If a system requires a continuous control system then it will tend
to be unstable, and even when controlled a precise values can be hard to obtain. The need for
control also implies that the system requires some accuracy, thus the process will tend to vary,
and be a source of quality control problems.