Newbie question on multi axis synchronization

On 16 Jan., 20:53, reginald.lo...@gmail.com wrote:

Two motors are synchronised if one folow other one . It means one
motor is master and other one slave.
Normaly, first at all, you make gearing between two motors and you
define curve X-Y (X is position of master motor and Y is position of
slave motors).
If you stop X axis (master), slave stops automaticaly (because gearing
is activated). If you want to run only X-motor, you need to turn off
gearing.

Best regards,

Leo

P.S.
If you need solution for multi axis synchronisation, I have solution
with PLC.

On Jan 16, 3:22 pm, e1e120032...@gmail.com wrote:

Thanks a lot

On Jan 16, 12:22 pm, e1e120032...@gmail.com wrote:

That is gearing.  The problem with gearing is that the slave usually
lags the master by s signficant amount.  The slave can use feed
forwards but if the master encoder is not very fine then calculating
accurate slave velocities and accelerations will be difficult.
Synchronizing is when you have the ability to synchronize the target
position, velocity, acceleration and jerk of multiple axes as a
function of time or as a function of a virtual master axis that is
used to 'speed up or slow down time'.  The functions can be
arbitrary.  In most cases they are identical moves as a function time
from one point to another.  I was just working on a problem last night
that did figure 8s for mixing.  The x axis would generate a sine wave
and start where the two circles of the figure 8 intersect.  The y axis
used a cosine and the cosine would alternate between the upper circle
and the lower circle by flipping some sign flags that were 1 or -1.
Both axis are geared to a virtual master's target position.

There are some examples of synchronized motion here
ftp://ftp.deltacompsys.com/public/movies/

Peter Nachtwey

I do a lot of systems with gearing. For example one master axis with
3000 mm/sec.
You don't have problems with speed,acceleration etc. Motion cards
today are very good and
you don't need to think about velocity,encoder,acceleration...
What you wrote is similar.

If the motion controller is truly gearing then it only knows what the
master is doing by the master position feedback,  This feedback
becomes the position set point or target for the slave.   The slave
will have a following error because a PID doesn't generate control
output without an error.  A more sophisticated system will use feed
forwards but this means that the masters positon feedback must be
differentiated once to get the master velocity and a second time to
get the master accelerations so that velocity and accleration feed
forwards can be applied.   Calculating the velocity accurately is
difficult because the time period between master positions updates is
short and the quantizing causes the velocity to be quantized.  The
acceleration is even worse.  When synchronizing ,the controller knows
the master target position, velocity and acceleration exactly so the
slave has an exact velocity and acceleration for its feed forwards.
This provides better control.

If the motion controller doesn't have control of the master then it is
gearing.  If the controlling has control of the master and slave it is
synchronizing.

Peter Nachtwey