Page 732 - Mechatronics with Experiments

718 MECHATRONICS

FIGURE 10.1: Components of an electric servo control system: motors (rotary and
translational) with built-in position sensors, drives (DC power supply and amplifier), and
controllers. Source: Baldor.

gear ratios between stations are defined in the application software. There are no physical
gears between axes. The same functionality is achieved by software control of the motion
of each axis. So, when a different product requires different gear ratios between axes, the
only change needed is to select a different software parameter set from the database. The
change-over time for different products is almost insignificant.
In a factory automation application, multiple PLCs and programmable motion con-
trollers may be used to control the whole process. PLCs handle the general purpose I/O
and act as the higher level supervisory controller relative to the lower level local controllers
(Figure 9.4). Programmable motion controllers handle the high performance coordinated
motion control aspects of individual stations and communicate to the PLCs. In small
automation applications, a stand alone programmable motion controller may have enough
I/O capability such that the machine control can be handled by it without the use of a PLC
(Figure 10.3).
Every programmable motion control system has the following components
(Figure 10.4):
1. controller,
2. actuators (motor, amplifier, power supply),
3. sensors (encoders, tachometers, tension sensors),
4. motion transmission mechanisms (gears, lead-screws),
5. operator interface devices.

Most of the technologies for the components of a PMCS have already been covered in this
text in various chapters. Here we will focus on the system level control software features
specific to automation applications of PMCS.