More than 8 axis of motion

We have had a couple of good motion control post the last couple of weeks. I have not been much help but I have enjoyed reading them.



So here is my question. What do you do when you need more than 8 axis? I am using a Delta RMC100 controller that has a max of 8 axis. I can use two controllers but if I want to gear an axis on one to an axis on the other what is the best solution?



Solution 1:

From the PLC start the moves at the same time at the same rate.



Solution 2:

Feed both controllers with a position reference from the master axis. This could be done with an analog feedback easy but I am using SSI. To stay with SSI I would have to use two position sensors.



Solution 3:

Get Peter to make a controller with more than 8 axis.



Any other solutions?

How bout the Deltas communicating with eachother over Ethernet? Blindingly fast, but would it be fast/reliable enough to sync axises????

Ethernet could work but the PLC would have to read the position (do some math) then send that position as a command to the other controller. It could work but I don't know how smooth it would be.

What is routinely done is to run a encoder signal to both RMCs and then use a digital input to both RMCs.

We also have a special SSI board that takes a SSI signal in and it relays that to another SSI input card. This way both RMC can operate off the same SSI encoder. We don't advertise this and we have only a couple of customers that really need this.

What is the application? We have synchronized 11 axes for an animated Dinosaur but it wasn't really required.

Call tomorrow.

What math?

How many is enough? Would 256 axes be sufficient (plus up to 16 virtual ones)?

On the other hand, if you prefer to stay with Delta, Peter's advice is what you need.

In the Ethernet example you would have to cal the amount to move from one axis to the other. Unless they were moving the same distance and were scaled together.

We have been working on (thinking mostly) using multiple punches on a press. Im fine on axis until I start making them position and pressure then I am 1-2 axis short. Sounds like you have a good solution with the SSI splitter. I had thought about using analog this way but I wanted more resolution.

My follow up question. If I am running an event step program using 2 axis. Can I still send a command to an axis that is not being used in the event step? I have an event step program running and I want the operator to select at what event step another axis moves. I do this with bang bang valves in my PLC program by looking at what step the RMC is at. When the current step is > selected step valve on then off the same way. I have been wanting to try it but I just have not found the time.

CharlesM said:

If I am running an event step program using 2 axis. Can I still send a command to an axis that is not being used in the event step?

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Yes. You should also know that each axis can be executing its own step sequence. The RMC is multitasking. We may be able to make use of that. We also have commands that allow you to move relative to another axis. This is important because you don't know exactly where the other axis may be because it is moving and there are delays over the ethernet.

CharlesM said:

I have an event step program running and I want the operator to select at what event step another axis moves. I do this with bang bang valves in my PLC program by looking at what step the RMC is at. When the current step is > selected step valve on then off the same way. I have been wanting to try it but I just have not found the time.

Click to expand...

It isn't clear whether you are or want to check the step number. Call.

The RMC is multitasking

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I did not know this or maybe I forgot. I'll open up RMCwin this morning and work with it a little. This could open a new door for me.

How many is enough? Would 256 axes be sufficient (plus up to 16 virtual ones)?

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Thats like asking how much memory do you need on your computer. Everytime I think I have enough they come up with something else we need to do. I think 10-12 would be all I would need but you never know.

if you prefer to stay with Delta, Peter's advice is what you need

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I would like to stay with Delta. I think for hydraulic motion control it is the best.