Automating Manufacturing Systems - Process Control and ...

plc pid - 25.5
(degrees presumably). The temperature will be read and stored in N7:0, and the output to
turn the heater on is connected to O:000/0.
GRT
SourceA N7:0
SourceB 74
U
O:000/0
LES
SourceA N7:0
SourceB 72
L
O:000/0
Figure 25.4
A Ladder Logic Controller for a Logical Actuator
25.3 CONTROL OF CONTINUOUS ACTUATOR SYSTEMS
25.3.1 Block Diagrams
Figure 25.5 shows a simple block diagram for controlling arm position. The system
setpoint, or input, is the desired position for the arm. The arm position is expressed
with the joint angles. The input enters a summation block, shown as a circle, where the
actual joint angles are subtracted from the desired joint angles. The resulting difference is
called the error. Theerror is transformed to joint torques by the first block labeled neural
system and muscles. The next block, arm structure and dynamics, converts the torques to
new arm positions. The new arm positions are converted back to joint angles by the eyes.