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Connecting Robots, LBs and the PLC

Siemens Creator Siemens Creator
Siemens Creator



I have a simple question about connecting LBs, robots and signal types in PLC mode.


I want to create a VC setup containing 2 robots, a gripper (on one robot), a screwer (on the other robot) a conveyor and so on. This study is controlled by a PLC program which is running in PLCSim Adv.


The communication between the robot and the gripper is done using wordwise copy operations in the PLC program. Thus it is necessary to create input and output signals of type WORD in PS that are mapped to the PLC tags. Unfortunately Robot Signals in PS are bits which means that I need to create an LB in PS that "translates" the bits of the robot outputs into word values that are then sent to the PLC. (I cannot use modules since modules are not executed in PLC mode).


To summarize, the communication between the robot in the PS study and the gripper mounted to it goes like:


( Robot --> Converter LB 1 -)-> PLC(Sim Advanced) -(-> Converter LB 2 --> Gripper )


And backwards of course for answers of the gripper Smiley Happy


The question is: What kind of signal do I use to connect e.g. the Exits of Converter LB 2 and the Entries of the gripper? There's no PLC involved here, so deciding to use (PLC) input or (PLC) output signals doesn't seem to make sense. Is is a use case for Display Signals?


For the robot interface, the decision which types of signals to use is limited already from the start. There I can only use Input and Output signals which seems to suggest that robots (in PS) are always connected "directly" to a PLC. But in principle my question also holds for the connection between the robot and Converter LB 1.


best regards



Re: Connecting Robots, LBs and the PLC

Siemens Phenom Siemens Phenom
Siemens Phenom

not sure I understood the question...

First: PS can deal with robot-signals of type WORD.


To mimic the behavior, there are several ways.

- key-signal

- I/Q/DisplaySignal and use forcing

- use an LB, e.g. with boolean Key-signal, and an expression for your exit-gripper-command-WORD-exit

   like >> entryOPEN * 555 + entryCLOSE *666

Re: Connecting Robots, LBs and the PLC

Siemens Creator Siemens Creator
Siemens Creator
Hi Guido,

thanks for your quick answer. My question was not about how to mimic the conversion. I've already solved this by using the LB-way you have also suggested.

The core of my question is: What kind of signal to use best to link the robot with the LB1 and the gripper with the LB2.

Re: Connecting Robots, LBs and the PLC

Siemens Legend Siemens Legend
Siemens Legend



I am not sure about your converters since as Guido mentioend, you can define a Robot Signal (input or output) which is a WORD and can be sent directly to PLCSIM Advanced, but you seem to have this part resoveld already, so lets waive it.


Regarding signals: there is some duplication between Resource Input Signals and Key signals (and the same for Display Signals and Resource Output Signals) in PS (aside from the Key Signal bevhaior in the Simulation panel).


While keeping completely internal in PS Input and Output signals have no difference aside from their look and feel in some applications (Panel), except for Robot Signals. A robot will only be able to set an Input Signal and read an Output signal.

Is there a reason you mind keeping this standard? Is there an upside to using them in reverse? If you even do want to connect them to the PLC - it will simply not work (PS only sends Input signals to PLCSIM Advanced and only reads output) which will cause you some rework best avoided I think. 


For Robot there's really no way to create Key or Display Signals.

Kind regards,
Gal Snir

Re: Connecting Robots, LBs and the PLC

Siemens Creator Siemens Creator
Siemens Creator



let me give an explanation for the converters:


The WORD-copy-method is the way how the PLC program accesses the hardware. This doesn't mean that the hardware exposes such an interface. For instance, the robot exposes an interface consisting of multiple independent bits. I can see this when I take a look at the real robot-code. The same is true for the gripper. Its inteface consists of multiple indendent bits according to the electro plan. So the PLC "sees" these hardware components WORD-wise. The "conversion" in the real plant is "done" by the wiring. That's why I've implemented the logical behaviors which allow to PLC code to go unmodified.


Of course, I could have implemented this conversion inside the LB of the gripper and robot, but then their interface in the PS study would have been different from their real one.


Regarding the types of signals:


I am trying to model the virtual commissioning scenario "correctly". By "correctly" I mean the following: I am dividing the VC scenario into a "controller" - the PLC-program - and a "controlled system" (in a control theoretical sense). The conversion mentioned above is part of the "controlled system". Thus, the connection between the LBs implementing the conversion and the components are also part of the "controlled system".


To model this connection I didn't want to use signals (input or output) that imply a connection to a PLC (if not technically then anyhow semantically). Unfortunately for the robot I will have to do this because there I can only use PLC input or output signals. For the gripper I will use display signals as Guido explained in a subsequent telephone call.


best regards