Help Start LabView Code for Hydraulic System

[rocksolidsr]

its to my understanding that you can't wire timestamps to booleans, i'm not sure i know what you mean

[lmtis]

Connect a case structure to your button.  In the true case output a time stamp.

[rocksolidsr]

gotcha thanks

[rocksolidsr]

can anyone help me out with the PID control, I'm trying to control the velocity using the current linear measurement divided by the elapsed time, and then the PID would output to a servo valve, but I can't get it to output anything right now

any help would be much appreciated, thanks

[rocksolidsr]

anyone with any help
does it even look like i'm going about this the right way

[rocksolidsr]

any PID experts out there want to try and give me some help, for some reason I'm getting a NaN for the output of my PID, my inputs look good though so I'm really lost here.  The velocity is what I want to control and I want a sustained velocity of 10mm/s and I want to control that with a servo hydraulic valve which accepts analog inputs from 0-10V, but like I said I can't get any output from the PID.  I have attached the picture and the vi, if someone could give me any advice I would really appreciate it



Message Edited by rocksolidsr on 03-12-2008 10:03 AM

[rocksolidsr]

so I was finally able to get an output although not the right output I finally got something (its only outputting like .03 when the process variable is 2) , I had to lower my proportional gain to less than 1 and set the others to zero.  for some reason when I have any kind of value for intregral time I get a NaN, does anyone know the reason for this. any thoughts

[Vivek_N]

Hello rocksolidsr,

What input values enter the 'PID % to EGU.vi'? You can place a probe or indicator on the '% span' input  wire in order to obtain this value.What is the 'setpoint' value that you have connected to the 'PID.vi'? The output value that you get should only be determined by these factors. Did you make any changes to your VI in order to view an output value other than NaN?

As I do not have a setup similar to yours over here, I cannot run the VI itself. Let me know if you still face the same issue.

[rocksolidsr]

actually to get those values I also am not using the % to EGU and EGU to % vi's anymore, not sure if this matters
i have attached my current vi and a picture of the block diagram

the process variable is speed (mm/s) and the setpoint I have set at 10mm/s and the output should be from 0-10  because the valve I'm using accepts analog voltages from 0-10V, 0 being closed and 10 being fully open.

thanks for the help


Message Edited by rocksolidsr on 03-13-2008 06:46 AM

[rocksolidsr]

I just remembered my valve works a little differently then I initially described, its a two way valve so it can flow in both directions (ie 0V fully open in reverse direction, 5V closed center position, and 10V fully open in forward direction.

any ideas how to acheive this in my vi