real time implementation PID and fuzzy controller of DC motor using DAQ devices

[Illa]

Sir,

     I am implementing PID control of DC motor using Labview which is an ieee paper,there they have used NI USB DAQ 6008,in which it generates one analog output channel  to driver circuit which drives the DC motor and one analog input channel from D/A converter which converts the speed of DC motor.

but in our college we have the following USB DAQs      NI USB 6259,       NI USB 6221.can i use these any of these DAQ in the place of DAQ6008,

actually in the specifications DAQ6008 measurement type is voltage where as 6259 and 6221 are quadrature encoder voltage.what is the difference,can i use them.

                                                                                                                                                                Karteek

                        MIT,Manipal,India

[LV_Pro]

Both of the DAQ cards you list can make the measurements you require. They can, apparently, be used for making quadrature encoder measurements, but both are data acquisition devices capable of doing what the 6008 does, but with a higher sampling rate and more bits of resolution.

[Coq_Rouge]

But if you use standard Labview. Your loop speed will still be limited by software timing to 1KHz

[LV_Pro]

No, it won't be realtime, nor was the one mentioned in the IEEE article I suspect, running on the 6008.

[Illa]

yes, its a real time, they have implemented the hardware with the hep of DC motor and sensor to measure speed, which is fed back to DAQ from there to PC which Labview PID controller is written.

i have one doubt here when  i am using labview  PID control  to control DC motor with the help of ni usb DAQ 6221,if the motor needs to run at above 10 volts(eg 12v) where DAQ maximum analog output voltage is fixed to 10 volts.how we should do ,is it possible?

what exactly is happening with the analog output terminals of DAQ? 

[LV_Pro]

Understand the definition for real time, unless you are running all of this on a computer with a "real time" operating system, which WIndows is not, you won't be running "realtime". This doesn't mean that you won't have a system that reponds (most of the time) in a fairly quick manner, adjusting the motor speed, just understand that real time usually means "deterministic", rather than instantaneous. If a "realtime operating system" implementation is properly designed it can get both the determinism (where an event, like motor speed updates, occur reliably at a known interval) and speed, but with Windows, while you may get speed, within the limits of Windows time slices mentioned previously, you won't get the determinism. Have someone wiggle the mouse rapidly and your motor control may run away, as Windows preempted your task to control the motor to handle the mouse task and now your feedback error signal has gotten much larger than expected.

The DAQ cards generally won't drive a moter directly, 10V, 12V, whatever, as they do not have sufficient drive current. You wil need to put a buffer, posibly as simple as a power transistor, between the DAQ output and the motor. It is also a bad idea to directly hook DAQ outputs to motors, solenoids, etc., they produce very high back emf spikes and can damage the output circuitry of your expensive DAQ unit. The DAQ output should be thought of as a control signal level to control a power amplifier that is then connected to your "load" device, motor, relay, etc.

[Illa]

I am Using NI USB 6221  DAQ  device,i need to do PID control of DC motor,what kind of drivers circuits  are compatable with DAQ devices,please post me some driver circuits if any for control of  DC motors. 

[jchal]

Hello Illa,

Could you please give me the reference for this Journal, as I am doing something similar.

Kind Regards

Jason