High speed D input Rslogix 5000

[Moro9797]

Hi all
I am going to read gaps between product by millmeter to accept or reject product, with RsLogix 5000,
The problem is : when the speed become nearly above 150 p/min
Cpu is L1765-L2, input module 1756-IB32/B, requested Speed of product is 600p/minutes, length of the product is 125 mm , the gap is 50mm
Requested packet interval(RPI) = 0.2 ms and I active enable change of state off-on and on-off , off sensor out put
The process: sensor see the start and end gap and read the actual position of servo drive encoder (96768 pulse/revolution) after Subtract and DIV I have the result, I mention to there are a lot of math rung to have the result, this result compared with stander gap distance to reject product

see attacment
https://files.fm/u/z5fzm6f3c

B.R

 

[pturmel]

Your RPI of 0.2 ms won't actually help you run that fast unless the logix is also evaluated at 0.2ms. You probably need a counter module with the sensor connected to Z in a latch/continue mode.

 

[drbitboy]

You say Speed of product is "150p/min" and "600p/min" - is that [products per minute], or [pulses per minute]?

How many pulses per mm, or mm per pulse? What is an acceptable gap e.g. "50mm +/- Xmm" or "100pulses +/- Ypulses?"

What is reading the servo drive encoder values?

What are typical PLC scan times?

The math should not be complicated; can you post a PDF of your code?

 

[drbitboy]

Assuming the -IB32 is detecting the edges, perhaps the -IB32 could be set up to generate (timestamped?) events or interrupts on change-of-state (COS) events, then the PLC could have a nominally microsecond-accurate difference for time from the part-detected event to the next part-not-detected event, which is 125mm, and so the next part-detected event is expected at 40% (of 125mm i.e. 50mm) of that difference hence.

This assumes

• symmetrical delays of the timestamps of rising and falling edges
• minimal other noise sources

This is a hail mary though; the basic problem seems to be that the PLC is trying to model sub-millisecond data with discrete hardware designed to operate at tens or hundreds of millisecond timescales.