Automating Manufacturing Systems - Process Control and ...

plc pid - 25.11
I:001/1 - START
B3/0
I:001/0 - ESTOP
B3/0 - ON
B3/0 - ON
B3/0 - ON
BT9:2/EN
BT9:1/DN
MOV
Source 0
Dest N9:60
SUB
SourceA N7:80
SourceB N7:42
Dest N7:81
MUL
SourceA N7:81
SourceB 2
Dest N9:60
Block Transfer Write
Module Type Generic Block Transfer
Rack 000
Group 1
Module 0
Control Block BT9:2
Data File N9:60
Length 13
Continuous No
Figure 25.12
Implementing a Proportional Controller with Ladder Logic
This controller may be able to update a few times per second. This is an important
design consideration - recall that the Nyquist Criterion requires that the actual system
response be much slower than the controller. This controller will only be suitable for systems
that don’t change faster than once per second. (Note: The speed limitation is a practical
limitation for a PLC-5 processor based upon the update times for analog inputs and
outputs.) This must also be considered if you choose to do a numerical analysis of the control
system.