Analog feedback from a displacement transducer for PID tuning in MAX (VCM, NI7344 controller and UMI7764)

[guxiangian]

    I hope this question can find quick answers..

    I am using the analog feedback from a displacement transducer for PID tuning in MAX (Voice coil actuator, NI7344 controller, and UMI7764).  There’s no encoder attached on the actuator, and I don't think I can connect the analog signal (via two wires) to the UMI encoder terminals for servo tuning? Instead, can I tune the PID parameters in MAX by connecting the displacement transducer readout to the analog input terminals on UMI? 

Thanks in advance!

Ian

[smithd · Accepted solution]

Hi Ian,

From your description, you shouldn't have any problem using the analog inputs. However, this KB may also be of assistance, if it is in line with what you are looking to do:

http://digital.ni.com/public.nsf/allkb/AB3CCA7FBFAD749A8625713B001D8581?OpenDocument

Thanks

[guxiangian]

Hello David,

Thanks for the solution, I think that'll work!

Currently, we exported a MAX configuration file from a laptop to another desktop to control the same controller, and the desktop is able to execute LabView code; however, we can't program in MAX Configuration for any of the axises, since all the selection bullets are frozen. 

Could you advise agian please?

Many thanks.

best,

Ian

[smithd]

Hey guxiangian,

Can you please clarify your set-up? You said you had a 7344 controller, but you say that you had been using that in a laptop. Was this a PXI chassis? What controller are you using (RT or windows)? What do you mean by "the selection bullets are frozen"? Are you able to remove the controller and add it manually?

Thanks

[guxiangian]

Thanks for your help.  The controller is 4 axis FW-7344 and it was connected to a laptop before, right now we use a desktop since it's faster.  Because the controller is obsolete, we encountered some version conflict problems and they are solved, we are able to do the PID tuning using analog feedback from displacement transducer.  As I may have mentioned before, the motor is voice coil (VC) actuator, and the drive is PWM servo drive.

I have the two following questions:

1. If the working measurable range of the displacement sensor is only 1/10 of the stroke of the motor, is the PID tuning still doable in MAX? It sounds like a problem.

2. Is open-loop control of VCM cyclic slow motions (displacement) possible?

Thanks a lot!

[smithd]

Hey guiangian,

That resolution will be tough or impossible with PID tuning. I suppose it is possible, in theory, but I doubt that it will work too well. It might be better, since you have such a limited resolution, to manually program in something that resembles PID, using those 10 known locations as checkpoints. This, as well as the suggestion in your question #2 would require a lot of testing. I'm sure it is possible, but you will probably need to test quite a bit to figure out what control values lead to what you would consider a smooth, slow, cycle.

Thanks,