closed loop 3 axis control questions

This is the first time I have ever used any of delta’s motion controllers so I am still a little confused about some of it. Anyway, I am building a linear setworks for the carriage we are running in our mill. We are using an rmc150. I have most of my programming finished, but I have a few questions. We are planning on installing this the week of july 4th and there are a few things I just simply cannot check on the mock up carriage I have built, and I dont want to run into any trouble on the 3rd 4th or 5th of july and not be able to get ahold of much help on any issues I may have. Like I said it is a true closed loop system. It uses a relief valve for cushion in the event of a heavy blow to one of the headblocks or if one hangs for some reason. My question is, in closed loop is the ( move relative) the best command to make sets with. So that the headblocks stop in exactly the same position and move exactly the same distance. Keeping them at the same speed etc isn’t as big of a priority as them moving the same distance and ending up in the exact same position, and if a cylinder does for some reason hang, or get pushed back by a log will it return to my targeted set position on its own or will that have to be written into the program. will it be necessary to turn of some of the auto stop commands. Also what is the best approach to keep all 3 synced in the same position. I know I can get this figured out on my own. I guess im just looking for a little peace of mind, and advice from someone who does this for a living. Thanks for any help and comments!

If the cylinders all need to be at identical positions, then I recommend using the Move Absolute command. Send the same Move Absolute command simultaneously to all the axes. This will take care of the synchronization. Once the axes have reached position, the controller will continue to maintain that position, even if a cylinders gets bumped. If the axes need to be at different positions, but move the same distance, then you would use the Move Relative.

One additional consideration is halts. If one axis halts due to some error, do you want the others to halt also? If so, you can put the axes in the same halt group. The Halt Group axis parameter is in the Axis Parameters, on the All tab, in the Halts section. If the Halt Group is zero, it means the axis is not in a group. Set the Halt Group to the same value for each axis. When one axis halts, the others in the same group will also halt.

Thanks for the response. I believe that I have everything workin properly other than 1 issue. Say my negative position limit is 2 inches. I can make relative a sequence of relative commands or use the absolute command to move right to 2 inches. And the system will stop there. But if I hit the commands again the system is swapping to open loop and my cylinders are running away from the target position . I guess what I’m asking is how is this avoidable or is there a way to keep the program from ever goin into open loop?

The default settings are that any error will cause the axis to halt with the harshest level of halt, which indeed puts the axis in open loop. You can change this in the AutoStops.

I assume that sending the commands again causes a Command Modified error such as Requested Position Truncated At Limit. You can see the errors in the Event Log. To prevent the error from halting the axis, set the corresponding AutoStop to Status Only or to a Closed Loop Halt.

On the setup I workin on I am still having trouble with some of the fine tuning. I will go ahead and say that my 3 hydraulic cylinders. Are not currently moving a load other than a clevis on the end if the rod. It seems that the more programs I write into the rmc the more inaccurate it gets. I have disabled all of the expression and command loging. And still am not having much luck. I have adjusted the requested jerk down so far it makes it sluggish. All of my tolerances are set very close also. I’m needing it to accurate within .003". I’m needing to move the axis in say 1.375 increments mostly. And I am getting anywhere from .003-.020 overset each time. Is there a way to remedy this. I’m currently using the absolute move command with the posistion to move set as axis[0].actpos-set distance -saw kerf. So it would be something like 30-1.125-.250 would yield me a 1.325" move and I should end up at a position of 28.625. Will it do better when it is set up and moving a load? Or is it just a tuning issue? Also what is the best way to command the axis to move like I have explained and stop at a given point. Say I’m at 30" and I want to move to 12 in 1" increments . And stop exactly at 12. Thanks again

The best way to get help on this is to email Attach the plot files and the RMCTools project. Also, include a description of your system: cylinder size, feedback type, valve type.

ill do my best to get all the information together and get it emailed sometime tomorrow. I going to check one more thing tomorrow. and see if the hydraulic oil temp is having an effect on anything. its in a small space right now. I believe I checked my oil temp and it got up to about 145 this afternoon when I started having some trouble. It usually runs in between 100-130 range, but Ill check it and see