Using Servo motor for position control connection?

[myo]

Hi all,

I am quite new to control engineering. My project is to control position and torque of servo motors. With NI PCI-7350 motion control card with an NI UMI-7764 box, I am using Labview to program. I use Servo dynamics Servo motor(IG23CS-22-IE2000-C) with incremental encoder and amplifier (815BL). I did connected the encoder output (Enable A+/-, Enable B+/-, Index+/-) to the respective port in UMI axis.

I am supposed to control motor position with PID control first. Therefore, I used the servo tune function in (MAX) software to obtain optimal PID gain of my motor but I failed.

Everytime I auto tune the motor, the alarm "Surge/Ground Fault" appeared in amplifier. I doubt if my connection is not correct.

I am confused with the connection from amplifier to UMI 7764 box. I connected only Command +/-  to Analog out and Analog out ground of UMI to get the signals from controller to motor. My question is "Do I still need to connect Inhibit/Reset of amplifer to Inhibit out of UMI for reseting purpose and anymore connection required?"

Anybody can help me please?

Thank you in advance.

Regards,

Myo

[risheeb]

Hi Myo,

To set up your servo system, the only connections that are required are the Command +/- from the drive to the analog outputs on the PCI-7350, and the encoder signals to the PCI-7350.  We do recommend that you use the Forward Limit, Reverse Limit, Inhibit, and Shutdown signals for safety reasons, but these are not required.

Page 21 of the user manual for the 815-BR indicates that this "Surge/Ground Fault" error is usually due to faulty wiring between the drive and the motor, so I would double-check these connections.  In addition, could you describe exactly what signals you have wired to each pin on the UMI-7764, including signals from the PCI-7350, the drive, and the encoder?  This will help us confirm that everything is wired correctly.  Thanks.


Rishee B.
Applications Engineer
National Instruments

[myo]

Hi Rishee,

Thanks for your reply. I am so sorry that I mentioned wrongly the alarm which is actually "RMS/Over Temp" alarm while auto-tunning. But I did checked wiring to confirm again. The followings are the wiring between the drive and UMI:

In the amplifier/Driver Terminals of UMI, I connected Command + & Command - of drive to Analog Output and Analog Output Ground of UMI respectively. I connected the inhibit/reset of drive to Inhibit Output(-) of UMI for safety.

In encoder terminals of UMI, all the encoder phase A & Bs and indexs connects the signals from encoder accordingly.

I confirm that the connections between the motor and drive are correct. I could tune the PID manually but not with auto tunning. The 'RMS alarm' keeps on appearing while I auto tune.

Thanks again.

Myo 

[risheeb]

Hi Myo,

So it sounds like the motor is drawing too much current from the drive when the auto tuning algorithm is run.  When you are tuning the motor, do you have it connected to the load?  If there is no load connected, this may explain why too much current is being drawn.

Also, are you running the auto tuning algorithm because you are having difficulty tuning the motor?  If that is the case, there is a good Knowledge Base article on our website about tuning.  Here is a link:

http://ae.natinst.com/operations/ae/public.nsf/webPreview/806F6F0B775FAF32862572FA0052F2AB?OpenDocument

I hope this helps.


Rishee B.
Applications Engineer
National Instruments

[myo]

Hi Rishee

Yes, you are right, I can't fine tune manually for my application until the requirement. I did without load during autotuning.

Thank you for the advice and link. It helps me alot.

Myo

[guxiangian]

Hi Risheeb,

I have a question: I am using analog feedback from a displacement transducer, I don't think I can connect that to the encoder terminals on the axis for the servo tuning, and it's supposed to be connected to the analog input instead.  Can I tune the PID parameters this way, or what else shall I try?

Many thanks!

best,

Ian