Dual encoder feedback on single axis implementation

I have reel-to-reel transport system connected to a NI 9516 module in one axis. It has two servo motors and two encoders. One encoder is on the motor, while the other is on the linear portion of the reel. Both encoders and the feeder motor are connected to the 9516. The Take-up motor is just set to contant torque. Since I want the ribbon to travel at a constant linear velocity, I have set the primary feedback to the encoder on linear portion, with dual encoder feedback enabled. Is this a proper utilization of the dual feedback mode, with one encoder monitoring linear velocity, while the other is monitoring rotational velocity?
Linus

Hello Linus,
I think the setup that you've shown would work, generally the secondary feedback is used for backlash but you should be able to use the secondary encoder to monitor rotational velocity.
Dual Loop Feedback Information and Configuration
Regards,
Isaac S.
Applications Engineer
National Instruments

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http://zone.ni.com/devzone/conceptd.nsf/webmain/E7ABA6F4D569010A86256F5A005B64F3/
Switch Feedback on the Fly
Consider a heat-sink assembly application where a position sensor is the feedback device for the initial positioning along the Z axis. However, when the heat sink is pressed on to the PCB, a force sensor must be the feedback device for precise motion control in the latter part of the process. With NI motion controllers, you can switch feedback devices on the fly without reinitializing the controller. The new feedback device might require the system to have a new set of PID gains loaded immediately after the axis is reconfigured. To minimize the delay, you can configure an additional set of PID gains with the motion controllers.
anyone can give me some detailed materials about "switch Feedback on the Fly", for example, some programme,some words to explain it.
another question is that if i don't use the torque sensor, can i directly use the DAC to control the voltage to come true the torque control?
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anyone can give me more suggestion about the Dual loop feedback?
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Greetings,
I am having problems with switching feedback sources in my Labview App. I am using a 7344 board. I initialize the board in encoder feedback as primary. Then I am able to switch to analog feedback, but then the problem is when I switch back to encoder feedback it acts like it is still using analog feeback as a Primary. I can only get it back to encoder feedback only if I reinitialize the controller. I am disabling the axis before I am making config changes and then re enabling axis to run axis on both accounts. However it doesn't seem to be getting back to encoder feedback. Any Ideas?
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Hey wade,
As mentioned in this Forum Thread, you should be able to switch back and forth between feedback sources on the 733X motion controller by disabling/enabling the axis. However, this is what you say you are doing. Perhaps changing the order in which you make the feedback switch. What happens if you make the feedback change and then simple disable/enable the axis? Are you seeing this same behavior on all of your axis? What version of the NI Motion driver are you using?
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I'm using the NI-7344 motion-controller (for the control of 2 servo-motors) in combination with an E-series DAQ-card.
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I am reading encoder feedback using Visual Basic and an E-Series Board. My problem is as follows: when the motor is moving in the negative direction and the encoder is counting down towards zero counts what is the best way to start displaying the counts as negative when it passes zero?

Since the STC is a 24-bit counter, it's a bit awkward to display the counts as negative. The least complicated solution would be to simply have a case statement that divides the counter values such that half are positive and half are negative.
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Hi !
I have UMI-4A ( Universal Motion Interfaces) and one steppermotor.
I have trouble finding a encoder to use with UMI-4A.
The UMI-4A user guide page 9 :
The Index puls must occur when both Phase A and Phase B signals are logic
low.
Please help me to find a suitable encoder.
Geir Kåre Refstie
Scanmar AS
http:\www.scanmar.no
[email protected]

Hi, no worries cheers for the reply!
I've managed to get movement to my desired location using NI motion, but my lecturer has requested that I use an incremental optical encoder for feedback, so that for every 2 steps a pulse would be registered or else the program would cease.
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Attachments:
Stepper motor Vi built for feedback no encoder.vi ‏31 KB

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I would like to be able to supply an analog feedback into the primary feedback axis and thus drive to this given analog feedback position. My problem is controlling the velocity at this time. The system runs off at a velocity controlled by (initially) the P of the pid loop. This can be any velocity and is usually quite large.
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Dual encoder feedback on single axis implementation

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