Chapter 4
Functional Overview
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National Instruments Corporation
4-3
generator calculates an instantaneous position each PID update period.
While simple point-to-point moves require only one trajectory generator,
two simultaneous generators are required for blended moves and infinite
trajectory control processing.
The following sections describe the five primary trajectory types supported
by the 7344 controller.
Trapezoidal Point-to-Point Position Control
Like virtually all motion controllers, the 7344 controller implements
trapezoidal profile control for point-to-point moves. The 7344 controller
has enhanced the trapezoidal profile to offer independent acceleration and
deceleration value programming and S-curve smoothing (jerk control) of
the acceleration/deceleration inflection points.
Motion occurs first with a programmable acceleration (smoothed by the
S-curve value), then for a period at a constant velocity (if required) and then
with a programmed deceleration, stopping at the desired target position.
You can interrupt motion by executing a stop or kill motion function.
Motion is automatically halt-stopped if an enabled limit or home input
signal becomes active during the move.
Note
Refer to the FlexMotion Software Reference Manual for more information on the
programming of trapezoidal trajectory control parameters.
Velocity Control
Velocity control is a simple variation of trapezoidal position control. The
same trajectory generator implements a continuous velocity control mode.
If you select this mode, the target position is effectively set to infinity and
the axis moves at the programmed constant velocity. You can change
velocity on the fly and all existing acceleration, deceleration, and S-curve
limits are in effect during the velocity transition. You can interrupt motion
by executing a stop or kill function. Motion is automatically halt-stopped if
an enabled limit or home input signal becomes active. This mode is useful
for jogging moves, simple speed control, and continuous contouring
motion applications.
Move Blending
You can use the 7344 controller to blend moves together with a
programmable blend factor. Using the user-defined blend factor, the
7344 controller DSP chip starts a second trajectory generator with the
second move on an axis while the first trajectory generator is still
