Shift Register Auto Sequencing

When step is done you can shift steps on condition

STEP_N      TRANSITION
----||---------------||---------------|SHIFT|

it will do one shift to a next step.

I use a step counter because this allows me to put steps in between and do jumps

if for example in some conditions particular steps are skipped.

Might I suggest using a UDT and / or combination of user defined constants to assign words to  your steps rather than numbers?

I use a very simple sequencing approach that is not really PLC family specific.

Sequencer FC:

---- some init code to initial the sequencer, like at startup, fault occurs, fault cleared and operator says let's start up again -----  It assigns proper value to sequencer if it is not already mid-sequence

-[==]- compare sequence tag against step.  Might be something like this:

"Process_DB".Step.Startup or Step[Startup] depending on whether Step is a UDT with a structure of individual bools with names that relate to the process, or, whether Step is an array of bools, and Startup is a user constant, say defined to values like 100,110, 120, 130, 200, 210, 220, 230, 300.., where the major number would indicate the type of sequencing is happening, like "initialize" where operator is changing from one recipe to another, maybe creating a new recipe for the 100 range, 200's would be for setup where physical world meets recipe and system is configured by manually manipulating things while the PLC monitors process values and saves them as needed for automatic mode.  300's might be manual operation where a single button may perform a complex but single "operation" or may manually control all devices with job speeds and such, and 400's is automated mode sequencing.

Just a thought.  Could be 1000, 2000, 3000, 4000, depending on the steps required.

Back to the logic.

compare sequencer tag against defined current step, perform logic for that step, and either wait for confirmation step is complete, or assign an interim next step where it waits for step completion, like:

step[ExtendSlideAForPhase1] which assigns Next Sequence value to "ExtendingSlideAForPhase1"

step[ExtendingSlideAForPhase1] waits for slide's position feedback or a simple blind "timer times out" and assigns next sequence value to whatever is next.

At the end of the sequencer, it then assigns the actual step[ index ] value to whatever the "next sequencer" value was set by one of the previous steps.  This gets around the race condition these types of sequencers have.

I posted something about this many years ago with screenshot examples.  A google search of these forums might yield that topic and post.

GuyBrows1983

Hi

I am using shift register sequencing for control of a machine. I am however finding this much more difficult than on Simatic Manager. The first issue I came across was that it was not possible to define a words worth of booleans and shift that word in my auto sequence with by shift left function. I like to do this so I can name each step. I got round this by mapping another word to my steps.

The next problem I am hoping someone may assist me with is that when I shift left to my next step and that steps rung is reading an input which is already true then I don't shift steps I have had to use a clock bit to get around this but I don't like it.

Can anyone advise me please on a better solution. Please see attached screen shot.

TIA Portal V13 SP1 Up 9 1214C CpU