# Newbie question on multi axis synchronization

Hi, I need some information about multi axis synchronization. What it really mean? It is simply to assure that 2 or more motor *start* at
the same time or it involve more than that?
I have a fairly simple example, an X-Y plotter (I never own one, so I don't know the answer yet). If I want to draw for example a long sinus wave : sin(t). This motion involve that the X goes in a straight line and that Y will oscillate up and down. X and Y axis is synchronize. If, during the motion I stop with my hand the motion of the X axis motor, do the Y axis motor will continue to oscillate, or it will stop?
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On 16 Jan., 20:53, snipped-for-privacy@gmail.com wrote:

Hi
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.
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On Jan 16, 3:22 pm, snipped-for-privacy@gmail.com wrote:

Thanks a lot
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On Jan 16, 12:22�pm, snipped-for-privacy@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
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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.

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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