Driver
An electronic device that converts the control signals to the correct
format and power needed to drive the motors.
Motion Device
An electro-mechanical device that can move a load with the necessary
specifications.
Cables
Needed to interconnect the other motion control components.
If the user is like most motion control users, they started by selecting
a motion device that matches certain specifications needed for an
application. Next, the user should choose a controller that can satisfy
the motion characteristics required. The changes are that the user is
less interested in how the components look or what their individual
specs are, but want to be sure that together they perform reliably
according to their needs.
We mentioned this to make a point. A component is only as good as
the system lets (or helps) it to be.
For this reason, when discussing a particular system performance
specification, we will also mention which components affect
performance the most and, if appropriate, which components improve it.
5.2 Specification Definitions
People mean different things when referring to the same parameter
name. To establish some common ground for motion control
terminology, here are some general guidelines for the interpretation of
motion control terms and specifications.
• As mentioned earlier, most motion control performance
specifications should be considered system specifications.
• When not otherwise specified, all error-related specifications refer
to the position error.
• The servo loop feedback is position-based. All other velocity,
acceleration, error, etc. parameters are derived from the position
feedback and the internal clock.
• To measure the absolute position, we need a reference, a
measuring device, that is significantly more accurate than the
device tested. In our case, dealing with fractions of microns (0.1
µm and less), even a standard laser interferometer becomes
unsatisfactory.
5-2 Section 5 – Motion Control Tutorial
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