PLC for Elevator Control

[RickL]

Hi!

Has anyone here coded a PLC for an elevator?  (commercial, 3 floors, hydraulic)

I'd love to see the logic tree for such an application!

...... would certainly be a challenging project!

[Joe Tauser]

I wouldn't touch an elevator application in the United States with a 100 foot pole.  My liability insurance isn't big enough.  You can kill someone just as easily in a manufacturing environment, but what happens in a factory generally stays in the factory.   If  the local news or some idiot with a cell phone gets wind of an elevator malfunctioning in a public building resulting in injury you are not only out of business but possibly in jail with our "Zero Tolerance for Error" society.

 

Joe T.

[Flex727]

Didn't Unitronics get their start by developing automated parking garages? They had an elevator, of sorts, to move the cars around. I can't find that information on their website anymore, so perhaps I'm misremembering.

[Joe Tauser]

They spun it off as a separate company - 

https://www.utron-parking.com/#

Joe T.

[RickL]

41 minutes ago, Joe Tauser said:

I wouldn't touch an elevator application in the United States with a 100 foot pole.  My liability insurance isn't big enough.  You can kill someone just as easily in a manufacturing environment, but what happens in a factory generally stays in the factory.   If  the local news or some idiot with a cell phone gets wind of an elevator malfunctioning in a public building resulting in injury you are not only out of business but possibly in jail with our "Zero Tolerance for Error" society.

 

Joe T.

WOW!  ......... your making this irresistible now!  :  )

All my life I've been the one who jumps in where others fear to tread!  

We have two elevators (3 floor + basement  hydraulic) that needs to be repaired and up-graded.  The quotes came in at  $80,000 for the one and $47,000 for the other!  At another location, I was called in to effect repair on a similar elevator they quoted $60,000 ........   I made the needed repairs for $4,000! 

Back to our elevators,  I've opened up and entered the ceiling escape hatch and rode the elevator up and down (there are test/maintenance operating controls atop the car).   I  was able to get a good feel for the "nature of the beast".

All the safety and limit switches tested fine, the high pressure pump and lift pistons working fine with no seal leakage ....... the problem is in the controller CPU board on both elevators. 

I'm confident I could write the functioning elevator "tree" code and car call queuing ..... including its 'fail- safe" protocols now having seeing it in action.  

Basically,   remove their proprietary CPU board controller, and install our own PLC.  

 

 

 

[John_R]

20 hours ago, RickL said:

Basically,   remove their proprietary CPU board controller, and install our own PLC.  

And as Joe is pointing out, you are removing the liability from that proprietary CPU manufacturer and putting on your shoulders...

Can it be done? Sure... But the old saying is;

Just because you can, doesn't mean you should.

[Ausman]

23 hours ago, RickL said:

All my life I've been the one who jumps in where others fear to tread!

In this case it could be jumping into prison, and that's something to fear. 

That was the point Joe was making.  He has the ability to write such a program very quickly, but careful consideration quells any desire.

By all means jump into your project, but be ready to extract yourself from the quagmire it will eventually turn into when a non-standard controller is discovered.   No doubt you'll take this as a challenge, when it is actually practical advice to not do so.

[RickL]

2 minutes ago, Ausman said:

In this case it could be jumping into prison, and that's something to fear. 

That was the point Joe was making.  He has the ability to write such a program very quickly, but careful consideration quells any desire.

By all means jump into your project, but be ready to extract yourself from the quagmire it will eventually turn into when a non-standard controller is discovered.   No doubt you'll take this as a challenge, when it is actually practical advice to not do so.

..........  your thoughts are well taken!   Thank-you!   :  )

[RickL]

23 hours ago, RickL said:

..........  your thoughts are well taken!   Thank-you!   :  )

I have in "request for standards modification/exemption" for an "invisible" morphing ADA wheelchair platform elevator design already (the ICC welcomes new challenging design paradigm).  I am aware of the codes requirements/compliance for human lift platforms and elevators.

Its a completely "invisible" design  ..... even as it morphs under you!  Basically, it "eats" the first stair step in front of you and at the same time replaces that step behind you as the platform rises.  There is no horizontal transport/movement  of the wheelchair during the lift.  

With my new interest in these multi-floor hydraulic elevators, posted earlier, for  repair/upgrade, It occurred to me after looking at the totality of this existing "elevator system" ........   that a PLC could  be coded (software solution) to replace 75 to 85% of the costly physical switching/control hardware (approach speed step-down, car level at floor, car door open/close, etc).

One example:  Incorporate a simple retractable steel cable/absolute digital encoder to know where the elevator is anywhere in its travels. The PLC would be coded for all speed profiles (ramping up and down, etc) and floor alignment with elevator car. This would eliminate all the many and very costly mechanical switch units. 

 

[kratmel]

Please try to find and read documents

https://www.asme.org/codes-standards/find-codes-standards/a18-1-safety-standard-platform-lifts-stairway-chairlifts

Even a brief description of this document makes the reader think about what he wants to do. This especially applies to moving drives and handling situations where the drive fails when it is loaded by a person.

I had the opportunity to examine the electric patient lift. In addition to the technically complex drive, there are brakes and a centrifugal emergency descent system at low speed. Certification of all this, especially software, is a separate problem. Otherwise, it is impossible to use such devices for transporting people.

[RickL]

6 minutes ago, kratmel said:

Please try to find and read documents

https://www.asme.org/codes-standards/find-codes-standards/a18-1-safety-standard-platform-lifts-stairway-chairlifts

Even a brief description of this document makes the reader think about what he wants to do. This especially applies to moving drives and handling situations where the drive fails when it is loaded by a person.

I had the opportunity to examine the electric patient lift. In addition to the technically complex drive, there are brakes and a centrifugal emergency descent system at low speed. Certification of all this, especially software, is a separate problem. Otherwise, it is impossible to use such devices for transporting people.

.........  Thank-you for your concerns!     Well taken!   :  )

 I've read much of this before!

But, If you were to read the incredibly long list of the possible dangers and complications to human life of just ordinary "aspirin"  ...... most wouldn't even get out of bed in the morning! 

I guess what I'm trying to convey about myself, is that I normally function "out on the edge"  of design, thinking, etc.  ....... only after do I address the necessary mandates of codes and compliance. 

Its the accumulated knowledge base in so many fields that drives me.  :  )

[John_R]

59 minutes ago, RickL said:

guess what I'm trying to convey about myself, is that I normally function "out on the edge"  of design, thinking, etc.

Back in my youth,  I had that "if you're not out on the edge, then you're just in the middle taking up space" mentality...

And that was all well and good back in the day, we all did a lot of designs that seemed perfectly acceptable at the time.

But "The times they are a changin'",  I look back at stuff I did 30 years ago that was very acceptable then, that would never meet the safety standards of the present.

And it's my "accumulated knowledge base" that drives me not to take on foolish challenges. 

Just sayin'....

[RickL]

44 minutes ago, John_R said:

Back in my youth,  I had that "if you're not out on the edge, then you're just in the middle taking up space" mentality...

And that was all well and good back in the day, we all did a lot of designs that seemed perfectly acceptable at the time.

But "The times they are a changin'",  I look back at stuff I did 30 years ago that was very acceptable then, that would never meet the safety standards of the present.

And it's my "accumulated knowledge base" that drives me not to take on foolish challenges. 

Just sayin'....

I hear ya!    Thank-you!   :  )

OK! .......... well, lets say we not beat this dead horse anymore in of its regulatory aspects!       :  )

...... instead,  to explore PLC "software code replacement"  for possible retro-fits for the ageing and  high maintenance cost equipment out there.

 

[Fernando Castro]

I have NO experience on elevators.

having said that I don't think it is challenging application by the technical aspects of it.

Maybe I am wrong, I assume that it requires specific safety components and of course there should be some specific compliance related to that, and that is why usually the price is high.

Usually, safetey related components needs to meet some test criteria and, sure you can do safety circuits without safety components, but you need to design redundancies and know all the MTTF values... 

I think this is the kind of projects that any experienced controls engineer will not take if it is not under his area of expertise also for the liability...

once a more experienced collage told me. "The company the quotes the higher, with the longest delivery time, and that seems that they don't even want to take the project is the one that actually knows how to do the job".

Not always the case, but I bet you this time it is.

 

[General Elevator Solutions]

On 3/9/2023 at 2:04 AM, RickL said:

Hi!

Has anyone here coded a PLC for an elevator?  (commercial, 3 floors, hydraulic)

I'd love to see the logic tree for such an application!

...... would certainly be a challenging project!

PLCs are programmed to implement the control logic of the elevator system. This includes managing the start, stop, acceleration, deceleration, and positioning of the elevator car. The control logic ensures that the elevator moves smoothly between floors and responds appropriately to user inputs.