Change velocity in a very short constant time!

[yoan]

Dear All,

  In my applications, I have a sensor to detect some physical quantity, and base on the  measurement to change motor's velocity in a very short constant time.

change vleocty------>measurment--------->change vleocty           (LOOP)

But there are two problems bother me for long time.

1.  I use pci7342,  there is no timer like DAQ card on it, cause that I can't get constant sample rate by ADC on 7342.

2. In velocity control mode, How can I change the velocity very fast? Does it alway should set the acc/decelation in every single loop?

Thank you very much.

Yoan

[Savageaggie]

Yoan,

Thanks for your post.  To measure at a deterministic rate on the ADC, you may need to use a seperate DAQ card from your 7342 if it is being tasked to much from other processes.  The only way to update and set velocity and acceleration modes on the board is to use the Load Velocity.flx and Load Accel.flx motion VIs in LabVIEW.  If you require those to change every iteration of the loop, you will have to set them each time.  On non-deterministic operating systems, you may not see the same performace on each iteration of the loops as Windows may task your processor to work on other threads during the same process.

Thanks,

Scott Savage
National Instruments
Applications Engineering
www.ni.com/support

[Jochen]

Just as an addition: There is a significantly faster way to change the velocity on the fly. Use "Load Velocity override.flx" to vary the velocity between 0 and 100% of the maximum velocity that you have set with Load Velocity.flx.

Best regards,

Jochen Klier
National Instruments Germany