DAQ Selection for Implementing Fuzzy Logic Control On Inverted Pendulum using LabVIEW

[Adil Ayub]

I want to use NI DAQ card for a control engineering application in my MS and PhD Thesis. I want to implement Inverted pendulum using Fuzzy Logic Tool Box on LabVIEW. I used your simplest USB NI DAQ Card but its response was slow (lagging) so it didn't controlled the inverted pendulum. It is requested to please suggest me exact model DAQ card that will perfectly control my application area.

[TimmTheEnchanter]

Adil,

We would need a lot more information on your setup to know how to approach finding you the correct device.

How are you going to control your device?  Are you using analog outputs or digital outputs?  Will you be using PWM?  

What will be your feedback or your inputs to the device?  Encoders, potentiometers, etc?

In general, I would point you toward a device capable of hardware timing with a couple of counters available on it.  This can be controlled through the DAQmx API, and processing could be done on your computer.  Update rates will probably suffice through USB, but there are plenty of online examples (search ni.com for "PWM") which will help you get started.

Regards,

[Adil Ayub]

Thanks for the reply. Sir i will use analog output to control the DC motor position to get my pendulum to the reference zero position (i.e vertically erect). For the feedback i will use free turn potentiometer.

[Adil Ayub]

Sir will USB 6009 DAQ card will control my application?

[TimmTheEnchanter]

The 6009 has 2 analog outputs.  However, the current drive on these outputs will not drive a motor, since it is only 5mA each.  You can see these specifications here, on the 6009 product page.

http://sine.ni.com/nips/cds/view/p/lang/en/nid/201987

5mA alone won't be enough to drive any sort of motor, and analog outputs connected straight to a motor usually only controls the RPMs of the motor, not the position.

If you are looking into controlling position of a motor, you may want to look into a stepper motor (although I'm not sure how this works into your controls theory).  Stepper motors require a different sort of output--it requires a pulsed train output instead of an analog output.  For more information on stepper motors and NI devices which can control stepper motors, you can search for "stepper motors" on the ni.com site:

http://zone.ni.com/devzone/cda/tut/p/id/4167

An analog input like what is available from the 6009 will work for reading a potentiometer signal, but keep in mind potentiometer signals can be very noisy.  Rotary encoder signals typically work better, but you should use counters to do this.  The 6009 only has one counter, and typically applications using encoders require two counters.

You also need to ask how important speed is.  If you can process your system in software, then software timing will be OK.  If you need something faster and more deterministic, I'd recommend you use some sort of DAQ device that can do hardware timing--for instance, an E-series or M-series device.

You can navigate through some of these options on ni.com (sort by using the left-hand columns to guide your search for 2 counters, 1 analog output, 1 analog input, E series, etc.)

http://www.ni.com/dataacquisition/

Hope this helps,

Andrew

[Adil Ayub]

Respected Sir,

Thanks for the reply. Sir is it possibble that i use the same 6009 USB DAQ and at the motor end i use the motor drive circuit ( using darlington pair of high current gain transistor as a power amplifier)?

kind Regards,

Adil Ayub.

[TimmTheEnchanter]

Yes, you can use any sort of power amplifier to drive a motor.  However, you'll need to make sure you are providing protection for your motor, not just driving the circuitry.  If you use search engines to search for terms like "back emf" and "motor circuit protection"  You'll find some valuable information.

Also, this series may help.  It explains more about calculations with motors.

http://zone.ni.com/devzone/cda/ph/p/id/46

-Andrew

[TimmTheEnchanter]

Also, the latency of USB communication for a 6009 is pretty bad.  For a control system, the determinism of timing would probably be very important for you.  You may want to look into a PCI device.

[Adil Ayub]

Thanks sir for the reply. Please suggest me exactly which economical PCI Device will control my application perfectly. Please indicate the device details (i.e model number and specs in detail) . Thanking you in anticipation.

Kind Regards,

Adil Ayub. 

[TimmTheEnchanter]

Adil,

I can give you a recommendation, but I cannot guarantee it will work properly without knowing more specifications about your system.  Below I've given some general information about signal levels of analog inputs and analog outputs that you may find helpful.

Any of NI's cards that have analog output are typically within range of +10v to -10v.  However you use this signal to control your motor through the power amplifier is completely dependent upon your system.

Also, any of NI's cards which have an analog input can typically read within the range of +10v to -10v (or in a smaller range if you choose--this allows you to get better accuracy if you need it).  Again, this means you would have to condition a signal (from a potentiometer, for instance) to provide a voltage that is within the range of what you set your DAQ card to expect.

One of our standard M-series PCI cards is the NI PCI-6251.  You can find product page and specifications for it by typing in "6251" into ni.com.

Also, if you'd like a comparison of latency between PCI and USB, you can find it in this post.  Also, you may want to look into this DevZone as an overview.

-Andrew