High-Speed Input and
Pulse Output Features
3–39
High-Speed Input and Pulse Output Features
Velocity Profile Operation
The velocity profile is best suited for applications which involve motion but do not
require moves to specific points. Conveyor speed control is a typical example.
Velocity Profile
Time
Velocity
Start
Profile
Complete
Y0
SP104
The time line of signal traces below the profile indicates the order of events.
Assuming the velocity is set greater than zero, motion begins when the Start input
(Y0) energizes. Since there is no end position target, the profile is considered in
progress as long as the Start input remains active. The profile complete logical input
to ladder logic (X0) correlates directly to the Start input status when velocity profiles
are in use.
While the Start input is active, the ladder program can command a velocity change
by writing a new value to the velocity register (V2323 by default). The full speed
range of 40 Hz to 7 kHz is available. Notice from the drawing that there are no
acceleration or deceleration ramps between velocity updates. This is how velocity
profiling works with the HSIO. However, the ladder program can command more
gradual velocity changes by incrementing or decrementing the velocity value more
slowly. A counter or timer can be useful in creating your own
acceleration/deceleration ramps. Unless the load must do a very complex move, it is
easier to let the HSIO function generate the accel/decel ramps by selecting the
trapezoidal or registration profiles instead.
Unlike the trapezoidal and registration profiles, you must specify the desired
direction of travel with velocity profiles. Load the direction select register
(V2321/V2322 by default) with 8000 0000 hex for CCW direction, or 0 for CW
direction.
Velocity Profile
Applications
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