10 Replies Latest reply on Jan 31, 2012 1:28 AM by Ahmad Fattahi

    Using PI for control?

    Lonnie Bowling

      I have a customer that is considering using PI for some simple control.  This would involve writing values to a PLC to turn things on and off.  They have a sharepoint site with PI Webparts and would like to see the controls there vs. a local HMI or full SCADA system.  My first reaction is; no way, really bad idea, PI is not designed to do this.  But the more I think about it the more I find myself asking why not?  Any opinions about this?  As anyone tried it?  Now I'm not taking about mission critical stuff.  This is more like building automation, adjusting temperatures, turning on and off fans etc...

       

       

       

      Lonnie

        • Re: Using PI for control?

          Hey Lonnie,  So no reason from a functional standpoint why you couldn't do this.  It is just a matter of having an interface that allows values to flow from the PI Server to the PLC.  However, the biggest consideration with this would be security, typically from a network topology perspective.  i.e. You would only ever want this capability from within a process control domain and not on the office/corporate domain.  I would be nervous about putting this in PI Webparts on a Sharepoint site on their office domain, you should at a minimum move this to a PCD.

           

          I have seen a PI System used for control and doing that right now on projects.  You have to pay attention to the resolution of data, and consider a mechanism to perform calculations at such a high frequency.  Anyway, you just apply your clients DCS/Control engineering standards to the PI System and half the job is defined already.

            • Re: Using PI for control?
              wpurrer

              We are also using PI to send some of  the setpoints and processvalue to the DCS systems. (Majority are controllers which directly using labratory data as the processvalue.)

               

              Usally every company has remote access to the hmi of the dcs, and there are I hope procedures in place to ensure security.
              if it done through a dcs hmi or a sharepoint webparts is only a technial difference.
              (importan are the security procedures arround)

               

              Typically in a DCS the following things are important:

               

              * Realtime  ( the user makes an action and expected immidiate reaction ... with a pi system this reaction can take minutes, or even hours ...
              * Build in controls to change the values (often with validation)
              * some kind of audit to see who changed what.
              ....

               

               

               

               

              • Re: Using PI for control?
                Lonnie Bowling

                Thanks for the response Rhys.  Yes, I think security is a big factor and something to really consider.  I found out more details and it appears that the system they want to control may actually be larger and more complex than I initially thought.  I'm a bit concerned about all the moving parts and points of failure.  Having a control system pass through IIS and Sharepoint in addition to the PI stack is a lot of layers.  I feel like having a local HMI is a good idea even if they decide to use PI for control.  Has anyone done a larger system with control (like >5000 points of monitoring and control), I'm interested in hearing your experiences.  Was there a backup system in case PI went off line?

                 

                Lonnie

                  • Re: Using PI for control?
                    Lonnie Bowling

                    Thanks for the reply Wolfgang, those are good points.  The real time factor could be an issue.  I would be using high scan rates for these points,  but I think there would be a few seconds delay best case, which is not the normal response people expect.

                     

                    I don't remember off of the top of my head, does PI Web Parts support writing values?  Is there any button controls or would that have to be custom?

                      • Re: Using PI for control?
                        wpurrer

                        i think the scan rate is not the issue .. but i had a couple of issues where the output tag doesn't behave as expected .. and it even took a long time.. (but this could had to do something in connection with a odbc interface bug.)

                          • Re: Using PI for control?
                            andreas

                            PI Webparts don't support data input. It seems to be ages ago that I wrote this blog vcampus.osisoft.com/.../manual-input-in-microsoft-sharepoint.aspx

                             

                            Hope it helps.

                             

                            IMHO the main issues with control from PI are security and confirmation that the value actually was written.

                              • Re: Using PI for control?
                                hanyong

                                Another option would be to use Infopath to create a form that writes data to PI via PI Web Services. The PI Web Services manual have example on how to use PI Web Services with Infopath form. After the form is created, you can publish the form in SharePoint using the Infopath form webpart. 

                                 

                                p.s. I know Infopath form webpart is available with SharePoint 2010 Enterprise, not so sure about SharePoint 2007 or MOSS.

                                  • Re: Using PI for control?
                                    mhamel

                                    I don't want to break your illusion but there are not just technical issues to use the PI System for control, there is a legal side of it. If you read closely the Software License Agreement (SLA) that each customer must sign before buying our products, you will discover that OSIsoft doesn't authorize to use them to control any safety related system or in any safety related application. Consequently, OSIsoft won't be responsible of any damages or losses related with a misuse of their products.

                                     

                                    In other word, the PI System was not put to be used as a replacement for a SCADA, DCS or smart PLCs solutions. Many customers use it to complement the information sent to control systems, by having suggested control specifications but at no time this should be involved in a closed loop to control.

                                     

                                    The key here is to use the products for its primary use, an infrastructure for management of real-time data and events.

                                      • Re: Using PI for control?
                                        Lonnie Bowling

                                        I was pretty much settled on not recommending do what they are asking, and based on the last three posts I am convinced that we would be using the wrong tool for the job, not a good way to start off a project.  I think PI has it's place, but not for this use case.  Thanks for all the feedback, this has been a good conversation.

                                         

                                        Lonnie

                                          • Re: Using PI for control?
                                            Ahmad Fattahi

                                            The biggest advantage PI System may have in these cases is to stay one layer higher than everyone else on the floor, collect data from everyone, do -fairly heavy- analysis and occasionally write back something not too time-sensitive to the controllers and production devices. In most control cases, PI System would be too big (and powerful) that causes the problems expressed by folks in this thread; the customers would likely be better off with something simpler and more focused on the given task, such as a DCS.