Scaling Settings Analog Feedback for 7354

[taletale]

Hello,

I would like to use a Torque sensor as an analog feedback in 7354. The sensor range is +/- 100 Nm, The output is 10 VDC for 100 Nm and 0 VDC for -100 Nm so Zero Nm is 5 VDC.

How should I scale torque values as counts ? When I program with Labview, What should i do ?

Thanks

TallTale

[T-Route]

Hello TallTale,

Thank you for using National Instruments discussion forums.  Some more information might help in understanding what type of motion control system you have such as: Is your Torque related linearly to the position of the motor or are you changing the velocity due to the torque value?  You can set the ADC range in Measurement and Automation Explorer for each axis analog inputs under "ADC Settings".  The difficulty comes in understanding the "paradigm shift" in the standard NI-Motion API terms; specifically target position, velocity, acceleration, and deceleration.  I have attached a really good document that discusses how to setup your motion control system for analog feedback.  I hope this information helps.  Thanks and have a great day.

Regards,
Mark T
Applications Engineer
National Instruments

[taletale]

Hello,

Thank you for the support.

First of all, our target is to move servo motor with constant torque. There is a control mode option in Parker servo driver so If I set control mode as torque control instead of velocity, Will I need any force/torque feedback ? Because Our tolerance is about + - %5 so maybe we don't need to monitor torque sensor.

The second issue is another force feedback. The servo cylinder must compress the linear system with constant force. (system is moving). We have a load cell in the link to monitor force and get a feedback. I need to get  to the cylinder move a target position (about 300 mm) with constant force. If you have any Labview example could you please share with me  or show me a way how to do this.

Thanks

TallTale

Message Edited by taletale on 02-03-2007 10:07 AM

[VuD]

Hello TallTale,

To help clarify Mark’s post, torque mode is essentially a voltage command written out of the motion controller's signal port.  By definition, a servo motor will turn at a constant torque proportional to the voltage supplied to it.  Hence, you would use the Load DAC.flx command to supply the desired voltage to the motor.  This method uses no feedback, and consequently the system will be software-timed.  If you want to provide feedback, another option would be to alternatively set up the system as a servo motor in velocity mode.  Though you will get feedback from the load cell, since the load cell response is nonlinear you may run into some small tuning issues; however, your output will change depending on your feedback.  The document Mark has attached above provides very useful information regarding the various options of feedback conversion you have with our motion controllers.

Best Regards,

Vu D