spedd control of DC motor using cRIO & NI 9505 ?

[SKant]

Hello,

I used some example codes from LabView and created my own progamming to control the speed of dc motor. I am using NI cRIO 9073 and NI 9505  to control the throttle position .I am able to vary the speed in both direction clockwise and anticlockwise but I am not able to tune perfectly.  I am using  PID tunning but I am not able to do sharp tunning.  When I am chenging the value from 0 to directly 60 deg its moving upto abot 60 deg angle but when I am decreasing from 60 to 50 or 40 deg. its not rotating. So please let me know if u have any idea about it or any method u using?

[Nate.H]

Hi,

I would recommend graphing the output of your system, similar to what is shown in the Reference Design for Model Based PID Tuning Dev Zone article. Then when you command a step function in position, you can see how the system responds based on your tuning. You will want to look at the following on a graph as you run the system:

commanded position: this is the value you want the system to arrive at. In your case, position (of the rotor angle in degrees)

acutal position: measured with a feedback device, typically a quadrature encoder, on the motor or shaft. 

PID output: this is the value that the PID controller is spitting out trying to get the actual position to match the commanded position based on your proportional, integral, and derivative gain. 

See what happens to the PID output as you change your commanded position from 60 deg to 50 or 40 deg. Does it keep getting larger in the negative direction, but the system doesn't respond? If so, you want to look at why the physical system is not responding to the commands from the PID control algorithm. If the PID output levels out or exhibits other "funny" behavior, than you want to go back an re-examine your tuning. See if you can see the same behavior with both underdamped and overdamped tuning conditions.

Once you are able to graph your system behavior, and if you still can't figure out what's causing the problem, post back here and I'm sure members of the forum can chime in once they have more data to look at. 

Resources if you have not already seen them:

Manual PID Tuning Using the Ziegler & Nichols Method

https://decibel.ni.com/content/docs/DOC-12607

A Simple Method for Servo Motor Tuning

http://digital.ni.com/public.nsf/allkb/806F6F0B775FAF32862572FA0052F2AB

If you have different dynamics moving forwards and backwards, this may also explain the behavior you are seeing. The following would have to be implmeneted on cRIO with the 9505 instead of with a plug-in controller. 

Tuning a Motion Controller for Different Dynamics Forward and Backward

http://digital.ni.com/public.nsf/allkb/8108FBCAF15FDEE0862572DE0071AE6B

Best Regards,

Nate

[SKant]

I also have a same question . I am using NI PXI-6511 DI module and SCB-100 TB but not able to get the digital input signal from my control penal. In control panal I am using 30 switch to send digital signal . I am using DAQmx create and read channel. So please help me here to resolve this issue.

[SKant]

Hi,

I am using NI PXI 1052 with 8 slot SCXI combo chassis. Here I am using pxi-6259 DAQ module with SCXI 1503 RTD module & SCXI-1102 Thermocouple module. I am not able to use both PXI-6259 DAQ and scxi module for data logging. When I make PXI in SCXI mode by pressing scxi selector switch, not able to use DAQ channel . At a time only one mode is working. So please suggest that how to use both in parallel. Its possible or not? From where i can find the solutions?

[sunny17]

hello 

i  am doing the same for a robotic arm for some surgical application.So can you please help me out with your VI's which u made.

Regards

Sunny