PLC programming style??

[Tofo]

Dear all,

I was told by my new boss that I need to use state type programming style in the RSLogix5000. I was not have any experience with any big program. I have only done a few programs that within 100 Rungs a year ago. The new project is my 1st project in the new company. I need help.

What is really the "state type programming style"

Thanks

 

[Ken Roach]

Ask him exactly what he means, in more detail.

He might mean "statement list", which is a very low-level IEC-6-1131 type language. Or he might be "structured text", another IEC-6-1131 language that ControlLogix does support.

Or he might mean "finite state machine" programming, which is really just a style of making if/then decisions. Most of my programs have a State Machine as an operating principle.

 

[baldone]

Several possibilities depending on whether the boss means..
State machine logic
or
Statement programming(structured text).

State machine programming to me is building a series of rungs that latch in sequence as the machine cycle progresses and unlatches them all at the end of the cycle.

 

[Steve Bailey]

It models your process as a series of states with transitions from one state to the next. The process can only be in one state at a time, although from any given state it may be possible to transition to more than one different state.

 

[Paullys50]

Keep in mind that RSLogix5000 does have "Phase Manager" available for standard state routines and such. Granted you have to be properly licensed to have access but does you boss mean the concept or this specific tool within 5000??

 

[Tofo]

It models your process as a series of states with transitions from one state to the next. The process can only be in one state at a time, although from any given state it may be possible to transition to more than one different state.

This is kind of what he talked.
The machine has 5 sub-machines which each of them does one task. For this type of state programming style, does it 5 sub-machines have 5 state sets? In other words, state1 in sub-machines Z will never involve in state1 in sub-machine Y?

Please provide more information, like websites. Thanks

 

[Tofo]

Keep in mind that RSLogix5000 does have "Phase Manager" available for standard state routines and such. Granted you have to be properly licensed to have access but does you boss mean the concept or this specific tool within 5000??

Concept, NOT tool.

 

[baldone]

This is kind of what he talked.
The machine has 5 sub-machines which each of them does one task. For this type of state programming style, does it 5 sub-machines have 5 state sets? In other words, state1 in sub-machines Z will never involve in state1 in sub-machine Y?

Please provide more information, like websites. Thanks

On packaging machines that I program that has a master machine state routine that controls indexing and triggers all related sub programs(heat seal, fill, etc) after indexing and resetting itself after all necessary sub programs are complete. Then repeating the master cycle.

 

[Tofo]

On packaging machines that I program that has a master machine state routine that controls indexing and triggers all related sub programs(heat seal, fill, etc) after indexing and resetting itself after all necessary sub programs are complete. Then repeating the master cycle.

Assume your package machine has a conveyor, the first robot opens a box, the 2nd robot put stuff into the box (longest time), the 3rd robot close the box. How do you make them communicate between each other in state style ? For example, how you make your 1st robot to do something and wait in state style program? Thanks

 

[Matthew Modar]

"Engineer on a Disk" has a good introductory guide:

http://engineeronadisk.com/V2/book_PLC/engineeronadisk.html

Scroll down to chapter 11, State Based Design.

 

[TConnolly]

Ask him exactly what he means, in more detail.

I'll second this.

I use state machine logic on sequential processes, but it does not lend itself to many applications. A state machine would be suitable for say a pick and place robot, but not a great fit for cooling tower control or effluent treatment.

You boss could be making a sound recommendation. He could also be just passing on something he recently read in a trade rag.

Hugh Jack's book has a good section on state machine logic.
http://engineeronadisk.com/V2/book_PLC/engineeronadisk.html

If you prefer a PDF version you can get it at http://forums.mrplc.com/index.php?app=downloads&showfile=156

 

[James Mcquade]

here's my 2 cents worth.

in regards to logix 5000, you can program contacts, coils, copy, moves, contacts, outputs all in series. several pages worth in fact.

the problem with this is your first output may be turned off before the fourth output requirement is met.

in other words, if you can't wire it, you shouldn't program it. doesn't mean you can't.

just remember who is going to maintain the machine, maintenance. keep the programming straight forward so that they can understand the logic. ask them what they are used to and how they would do it.

REMEMBER!!!!!
if maintenance can't understand the logic, the machine won't get fixed, production suffers, your boss gets yelled at and you in turn not only get yelled at, but baby sit the machine 24/7 or until you rewrite the code so maintenance can fix the problems. by that time,,,, I think you get the picture.

regards,
james

 

[dwoodlock]

I would reccomend looking up grafcet on google. It may not be exactly what he's talking about, but I think its in the same ballpark.

They teach this method at my school for PLC programming, but you can really apply it to any process to analyze step by step whats going on, and all the variables that can take place in a process.

I think Michelin has this as part of their curriculum for Mechatronics.

anyway good luck!

 

[shooter]

grafcet is not a state programming
ask the boss if he wants it as a sequential chart or as a complex chart, or really as a state machine.

a state works with circle for a position the machine is in , and lines going all over the place when having contacts closed or events happened.

 

[shooter]

the state machine is ratjher easy to draw and make it on paper, in a PLC it is not that easy, standard it is done with jumps to routines