I have a AB-SLC500/03 processor. I need to read in a DCV proportional to a speed, and output a DCV signal to a control valve. So in other words run a speed Vs. valve position profile. As the speed changes, the valve (oil flow control) must follow based on a predetermined map. The valve output is not linear, so it sounds like a table may be required. I looked at the instruction set, but saw nothing obvious such as a lookup table function. Any ideas?
Speed vs. Position
- Thread starter hamdep
- Start date
OkiePC
Lifetime Supporting Member
A lookup table does sound like the way to go, but you should not need anything special (aside from good understanding of indirect addressing) to set this up in a data table of your choosing in the 5/03.
I would expect that your table would consist of a data file set to the type floating point, and each entry would be a value from 0.0 to 1.0 that would be applied to the value in the SLC which is being sent to the valve.
If your table needs more than 256 entries, then more than one data file will be required along with a selection mechanism.
If you are new to RSLogix500 or how to use indirect addressing with a/b PLCs, there are many threads on the subject or just ask questions here.
I would expect that your table would consist of a data file set to the type floating point, and each entry would be a value from 0.0 to 1.0 that would be applied to the value in the SLC which is being sent to the valve.
If your table needs more than 256 entries, then more than one data file will be required along with a selection mechanism.
If you are new to RSLogix500 or how to use indirect addressing with a/b PLCs, there are many threads on the subject or just ask questions here.
Mickey
Lifetime Supporting Member
If you can plot the non-linear response you could then develop a polynomial equation to control your output.
http://download.cnet.com/CurveExpert-Basic/3000-20417_4-10920865.html
http://download.cnet.com/CurveExpert-Basic/3000-20417_4-10920865.html
Last edited:
Peter Nachtwey
Member
Does the 503 have a compute block?
Mickey
Lifetime Supporting Member
Peter Nachtwey
Member
Good!
Micky, can you put this equation in a compute block?
v(x)=v0*sqrt((x1-x)/(x1-x0)) is the velocity as a function of position
v0 is the initial velocity
x1 is the position at where v(x) = 0
x0 is the initial position
x is the current position
This equation is for a second order ( constant deceleration ) ramp
Third order ramps are MUCH more complicated.
Micky, can you put this equation in a compute block?
Code:
v0*sqrt((x1-x)/(x1-x0))v0 is the initial velocity
x1 is the position at where v(x) = 0
x0 is the initial position
x is the current position
This equation is for a second order ( constant deceleration ) ramp
Third order ramps are MUCH more complicated.
Mickey
Lifetime Supporting Member
Yes
Peter Nachtwey
Member
Good Mickey we are done
Hamdep has only to enter in the code.
Hamdep has only to enter in the code.
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