Manual

Appendix E 15-1
15 Appendix E Speed Considerations
System Elements
A motion control system consists of several elements: the host computer, the RS-232C
interface, the Automove System's internal processors, and the physical motor/load system
itself. In general, the act of moving the carriage at a controlled acceleration and slew speed
takes so much time that the speed of the other system elements is not a concern.
For example, at 386000 microsteps/second/second acceleration and 10000 steps/second slew
speed, assuming 1000 microsteps per inch, a 0.5-inch move takes approximately 76
milliseconds (0.076 second) to execute. This is broken into 26 milliseconds of acceleration,
24 milliseconds of slewing at 10000 steps per second, and 26 milliseconds of deceleration.
With these same parameters, a 0.1-inch move never reaches slew speed; it takes a total of
approximately 32 milliseconds to execute, evenly divided into acceleration and deceleration.
Longer moves, of course, take longer to execute.
At 9600 baud with a parity bit and one stop bit per character, it takes approximately 13
milliseconds to transmit the sequence MA12000,11000; over the RS-232C interface.
Because of its input buffer, the Automove System can receive these characters while still
processing previous commands. Delay within the input buffer itself is negligible.
If your application uses lots of medium-to-long vectors and arcs (say, one-inch and up) its
speed is probably limited by the physical motion. If you can, try increasing the acceleration
and slew rate via the AC and SR commands. If you need a few fast vectors mixed in with a
lot of lower-speed vectors, use the VM command to flag the fast ones.
Arrange your program so that moves are not wasted; keep the total travel distance as low as
possible.
On the other hand, if your application uses a lot of short vectors, its speed may be limited by
the other system elements. Read on!
Precomputation and Overlap
The Automove System typically requires about 13 milliseconds of precomputation time for
each true-speed MA vector, and a little more for MR vectors. (Arcs take considerably more.)
Add about 5 milliseconds if the XY Linearity Correction mechanism is enabled, and several
more if the pattern rotation angle is nonzero. This time begins when the System fetches the
last parameter's delimiter (usually a semicolon ";") from the buffer; it ends when the carriage
actually begins to move.
All but 3 milliseconds of the precomputation can be time-overlapped with the immediately
preceding vector or other physical motion command. This overlap is possible because the
Automove System contains two internal microprocessors: one for receiving and pre-
processing data from the host, the other for controlling "physical" things such as the motors,
the Digital Outputs, and the front panel.