M580 Derive function

[Anonymous user]

Hello community, 

I'm looking for a function that can derive in the M580. Last week a client of us had big accident in one of their machines. This failure occured because of a component that was too old, the machine did trip because of another failure signal that appeared a seconds later. I don't want to anticipate the failure because it will be impossible, I want to trip the machine when the failure occurs. For example, of all the variable of the machine we saw to critics change, the pressure of the circulating water of the machine drops 1.3 bar in 4 seconds which is dangerous, the speed of this change in such a short time is the one I want to evaluate, so I can make a new trip. Any ideas people? I thought of a derivating function. Thank you very much. 

[Oncom]

If I'm not wrong, your point is:

If the pressure of the circulating water of the machine drops 1.3 bar in 4 seconds, you want to shut off this machine

I think we can just simply use LE (less equal)/LT (less than) and TON (Timer ON/ delay ON) to make a Machine Trip?

[Anonymous user]

Hello Mr.

If you take a look at the graph, you will see that the speed of the change of the variable is fast. There is a simple LT shutdown but it is at 1.5bar. If a change of 1 bar or more in just a short period of time it tells me that something else is going on, like a damage of the cylinder. Want I want to do is minimize that impact of that failure. 

[Oncom]

hi @Anonymous user ,

noted. you can use AVGMV for fixed size of time window or AVGMV_K (if you want correction factor K) 

AVGMV Description:

  OR 

VariableDescription

Y(new)	Y Value in current program cycle
Y (old)	Y Value from the last program cycle
N	Window size (number of values in the buffer)
X(N-1)	oldest X value in the buffer

VariableDescription

Y(new)	Y Value in current program cycle
Y (old)	Y Value from the last program cycle
N	Window size (number of values in the buffer)
X(N-1)	oldest X value in the buffer

Input Value or X is your real value.

and manipulated variable is V or Average

[Oncom]

Sorry @Anonymous user , 

after re-read your post. I think I was misunderstood again.

so you want to detect accidentally 1 Bar increment.

let me try to test it first

[Oncom]

@Anonymous user Hi, is it the function do you need?

[Eric_Coudurier]

 You could use the AALARM function block from the General Purpose Library (GPL) downloadable from this site. The function embed a deviation alarm which is I think what you need.

[Oncom]

@Eric_Coudurier great to know that 👍 GPL would be proper to used than my DFB.

if I'm not wrong, it (deviation) should be configured in SPD parameter? @Eric_Coudurier 

[Eric_Coudurier]

Yes SPD is the deviation setpoint. but there are other parameters to fill: HYSTSP, TONSP, TOFFSP and SP.

Here the functional schema :

 

To enable the alarm you also need to set: AALARM_CFG.CFGW.2 and DWATCH 

[Anonymous user]

Thank you all for your suggestions, I will take a look to the blocks. For your knowledge there is a derive block that I found it's called "deriv"

[Anonymous user]

I think this one is great.