John A. Shaw is a process control engineer and president of Process Control Solutions. An engineering graduate of N. C. State University, he previously worked for Duke Power Company in Charlotte, N. C. and for Taylor Instrument Company (now part of ABB, Inc.) in, N. Y. Rochester He is the author of over 20 articles and papers and continues to live in Rochester.
Servo compensation usually implies that some type of ﬁlter network such as lead/lag circuits or proportional, integral, or differential (PID) algorithms will be used to stabilize the servo drive. However, there are other types of compensation that can be used external to the servo drive to compensate for other things in the servo plant (machine) that can, for example, be structural resonances or nonlinearities such as lost motion or stiction. These machine compensation techniques are shown in Figure 1 and are valid for either hydraulic or electric servo drives.
Despite the great technological advancement experienced in recent years,
Programmable Logic Controllers (PLC) are still used in many applications from the real
world and still play a central role in infrastructure of industrial automation. PLC operate in
the factory-floor level and are responsible typically for implementing logical control,
regulatory control strategies, such as PID and fuzzy-based algorithms, and safety logics.
Usually PLC are interconnected with the supervision level through communication
network, such as Ethernet networks, in order to work in an integrated form....