Manual

3-4 Detailed Descriptions of ACL Commands
Antibacklash vectors are temporarily disabled during Continuous Path motion; see the BC
command.
AC [<accel>] Acceleration
The value <accel> becomes the acceleration (in thousands of microsteps per second per
second) used for subsequent AA, AR, MA, MR, and MT commands, as well as Continuous
Path motion, the GO TO ORIGIN vector, and the FH backoff vectors. Usable values are in
the range 10 through 65530. If a microstep is 0.001 inch, these correspond to accelerations
in the range 0.026 G (Gravities) through 169.8 G. (One Gravity is 386.04
inches/second/second.)
If <accel> is omitted, and also at power up and at IN, acceleration defaults to 193 thousand
inches/second/second, corresponding to 0.5 G at 0.001 inch per microstep. The default
value 193 itself can be changed via the PE command, so that the System "wakes up" with
the desired acceleration at power up.
Acceleration is applied to vectors as follows:
The carriage speed increases smoothly (i.e. linearly) from zero to the step rate specified in
the SR command. The carriage travels at this "slew" step rate for a while, then decelerates
smoothly to zero velocity at the commanded endpoint. If the vector is diagonal the specified
<accel> is the diagonal acceleration along the vector. Some vectors may be too short to
reach the slew phase before they must begin to decelerate.
Acceleration is applied to arcs as follows:
The carriage accelerates smoothly until it reaches the specified step rate along the arc (i.e.
tangent to the arc). It slews for a while, then decelerates.
Circular motion has two components of acceleration: radial (or centripetal) acceleration
which is directed towards the center of the arc, and tangential acceleration which is directed
along the path of motion. The Automove System budgets 0.707 of the <accel> value to
each of these two components of acceleration. Since they are always at right angles to each
other, the total peak acceleration of the load in any direction will never exceed the specified
<accel> value. It follows that neither motor will be required to deliver more than this value
of peak acceleration to the load.
Radial acceleration depends upon speed and radius. At small radii the Automove System
automatically decreases the slew velocity to prevent the radial acceleration from exceeding
its budgeted amount. For example, if AC 386; SR 10000; has been executed, slew rate
will begin to be limited at a radius of 366 microsteps (or 0.366 inch on a typical Automove
X-Y table). But if AC 39; SR 10000; is executed, the slew rate will begin to decrease at a
radius of 3.66 inches. The crucial radius is the square of the step rate divided by the
budgeted radial acceleration.
Acceleration is applied to a Continuous Path move as follows: The carriage accelerates,
slews, and decelerates once for the entire Continuous Path move. In order to control radial
acceleration, the slew rate is limited according to the smallest arc radius of the entire
BC...EC sequence. If there are no arcs, the slew rate is as specified by the SR command.
See the BC command.