Re: [CAD_CAM_EDM_DRO] Servo to go card's, RUTEX

Carol & Jerry Jankura wrote:

> Jon:
>
> Let's say that I'd like to move from location (0, 0, 0) to location (1, 1,
> 1) using interpolation (G01, for example). I've calculate that X must move
> 500 steps, Y must move 1500 steps, and Z must move 2300 steps. In addition,
> the Feed rate should be 1400 steps/second. I assume that I'd need two of
> your 2-channel boards.

There is no 2-channel board. The universal stepper controller will control up
to 4 axes, unless you use the encoder counters for other purposes, like a jog
dial. So, one board will do 3 axes.

> How would these be synchronized?

By your computer. The board knows noting of position, except that it counts
step pulses (or encoder counts) and reports them to the CPU. It works like
a servo system. You compute a desired acceleration profile, and figure out
what velocity each axis needs to run at to be at the right place at the end of the
next servo update cycle. You program those rates into the velocity registers.
At the end of the cycle, you read the current positions, and compute new
velocities, taking into account the acceleration, and the error from where you
wanted the axis to be at that time. You repeat this every servo cycle (1 mS
works out well in most cases) computing the desired position (the trajectory)
and then computing a new velocity based on the trajectory and the actual
position (the servo loop).

> What information would I send to your board?

You would read position, and send velocity. Velocity is a 24-bit unsigned counter value
for each axis, plus a direction bit. You also have to read current position, which
is a 24-bit signed value for each axis. All this information is handshaked across
the bidirectional parallel port using the IEEE-1284 protocol, which all Pentium-class
motherboards now support.

Jon