Load Capacity; Maximum Velocity; Minimum Velocity; Figure 6.2-12 - Position, Velocity, And Average Velocity - Newport ESP6000 User Manual

Section 6 — Motion Control Tutorial
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6.2.11 Load Capacity

There are two types of loads that are of interest for motion control applica-
tions: static and dynamic loads.
The static Load Capacity represents the amount of load that can be placed
on a stage without damaging or excessively deforming it. Determining the
Load Capacity of a stage for a particular application is more complicated
than it may first appear. The stage orientation and the distance from the
load to the carriage play a significant role. For a detailed description on
how to calculate the static Load Capacity, please consult the motion
control catalog tutorial section.
The dynamic Load Capacity refers to the motor's effort to move the load.
The first parameter to determine is how much load the stage can push or
pull. In some cases the two values could be different due to internal me-
chanical construction.
The second type of dynamic Load Capacity refers to the maximum load
that the stage could move with the nominal acceleration. This parameter is
more difficult to specify because it involves defining an acceptable follow-
ing error during acceleration.

6.2.12 Maximum Velocity

The Maximum Velocity that could be used in a motion control system is
determined by both stage and driver. Usually it represents a lower value
than the motor or driver are capable of. In most cases and in particular for
the ESP6000 controller card, the default Maximum Velocity should not be
increased. The hardware and firmware are tuned for a particular maximum
velocity that cannot be exceeded.

6.2.13 Minimum Velocity

The Minimum Velocity usable with a motion device depends on the motion
control system but also on the acceptable velocity regulation. First, the
controller sets the slowest rate of motion increments it can make. The
encoder resolution determines the motion increment size and then, the
application sets a limit on the velocity ripple.
To illustrate this, take the example of a linear stage with a resolution of 0.1µm.
If we set the velocity to 0.5µm/s, the stage will move 5 encoder counts in
one second. But a properly tuned servo loop could move the stage 0.1µm in
about 20ms. The position and velocity plots are illustrated in Figure 6.2-12.
average
velocity
Figure 6.2-12 — Position, Velocity, and Average Velocity
position
velocity
1s
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