About close loop control

[fourteen]

I am doing a close loop control to control the velocity of a motor and the position of a plate which is droved by the motor. i do not have a motion controller card. what i have is a tachometer to read the velocity of the motor and a linear position of the plate, and i want to do a close loop control to set a target velocity so that the motor will fellow and the target that position i want this plate to move to.

I have been trying to find an example in the forum, but i can not get the answer.  

The main problem is that i do not know how to use a close loop.

can i use the advanced functions in the labview, like the PID controller and Set target position VIs when i do not have the motion controller card?

and how to use a while loop or a for loop to get the target velocity being implanted into the motor?

[Jochen]

Hi fourteen,

before we go more into detail, could you please provide a bit more information about your system? Please provide the following information:

• What type of I/O hardware are you using?
• What's your LabVIEW version?
• Are you running your application in a real-time envrionment (strongly recommended) or on Windows (not recommended)?
• What type of motor and drive are you using and what's the interface to your drive?

Thanks and kind regards,

Jochen Klier

National Instruments

[fourteen]

i am right using the NI PCI 6221 card. 

the motor is a normal rotary motor, 

Labview version is 8.5. and the motion and version module haven't been installed. 

what do you mean by interface?

i am using the NI card AO output an signal to the amplifier and the send the voltage to the rotary motor. A tachometer is used to read the velocity of the techometer?

is there any possible that i can do a close loop control or even specify a velocity profile that the motor can fellow, what if i have the motion and version part installed?

one thing to mention is that i do not have a motion controller. 

[Jochen]

Thank you for the answers. You haven't answered my question about the operating system, but I guess you are using Windows. As already said, this is not a recommended setup and with the non-deterministic timing of Windows there is a high chance to run in serious trouble with closed loop control applications.

To avoid problems with instable control loop behavior and for ease of use I strongly recommend to use a motion control board instead of a DAQ device. Besides the risks that come with closed loop control applications under Windows, you also will have to implement all other aspects of a motion control system by yourself (trajectory generation, limit switch checking, monitoring following errors,...) if you stick with your current approach.

There are many similar threads in this forum. Please refer to these discussions for more information. In some cases closed loop control under Windows might be acceptable, but in most scenarios it's not.

Kind regards,

Jochen

[KateB]

Basically, you'd need PID toolkit, http://sine.ni.com/nips/cds/view/p/lang/en/nid/1394 .

Use 6221 to read tacho frequency, and translate it into speed.

Feed it back as process variable and output as AO.

But as Jochen said, performance will not be impressive.