DC master/slave commnications

[Concepts]

If I delay the speed reference 40ms from the master to the slave what will be the result? Will the slave droop from lack of a updated speed refrenece? Will it then try to catch up or slow down will it go into current limit? Please help with this one I need a answer if anyone can help me.
THanks

 

[nbucska]

A delay in a control loop can be modeled as multiple poles (the Taylor series of the exponential ). Generally it reduces the phase margin . E-mail me your circuit & FAX # <nbucska@pcperipherals.com>

 

[jbartos]

Suggestion: There are additional possibilities depending on the circuit design, e.g. the slave may time out and shutdown the controls depending what 40ms may impact, or the slave may or may not even notice it.

 

[rhatcher]

The effect on the slave due to a delay in speed reference with respect to the master will be determined by the connection between the two. For example, do these motors drive rolls for a machine processing a sheet product (aluminum, paper, plastic)? If so, such a delay would cause a mess. I have seen droop applications where the reference (torque or speed) to the slave is reduced with respect to the master but never one where it is time delayed. If you provide more info I am sure someone here can help.

 

[Concepts]

I understand what you mean rhatcher I have done paper machines any web app. can be very sensitive to speed reference. This is a crane application a very large crane it runs on tracks and one side is the master the other a slave. If they are not matched near perfect then the slave could be left behind as they move along the rails. I said 40ms because that was about as fast as I could get RS232. Does this help? I hope so, I would like to thank all for your help.

 

[dislhosur]

The time delay that can be provided between the master and the slave would depend on several factors:

1) The load profile that the slave and master are subjected to.
2) Whether the time delay can be absorbed by the system as a whole. It is all about doing settings and observing the final result. There may or may not be tolerences in the system to accomodate the delay.
3) If they are on rails there is still a stiff accuracy level that has to be maintained. How are the sections linked? If they have rigid links then the delay would strictly depend on the tolerences in the mechanical linkages.

As you can see the delay is a function of the process and not the otherway. For the purpose of dampening the responce of the system it can be adjusted then again with the limitations that are declared by the process.

 

[Concepts]

It is a bridge crane so they are linked by the steel structure.