Hi,

I have an application where I have two belts, one behind the other, which run at the same speed and at the same time, for a set distance. (Relative movement).   

On the first belt, I have to stop the belt at a certain variable point and continue the movement when the second belt has ran for 150mm. Once the second belt has ran for 150mm then I continue the first belt.

My velocity is quite high at 800 mm/s, and the accel/deccel/velocity/jerk are matched with one another for both belts.

The problem I have is that the two servos are on separate PLCS, and I am just mapping the technology object encoder value of the S210 across to the slave PLC, once the slave PLC reads this value then I continue the first belt. However when the second belt stops I have to immediately stop the first belt, because the second belt comes to a halt to a relative position it starts to decelerate slowly towards that position, whereas the first belt does not know when to stop, and just stops immediately when the second belt stops, so when the second belt is decelerating to position the first belt is continuing at its normal velocity!

Is there a way of getting the servos to talk to eachother so that the second belt can tell the first belt that it's about to decelerate and they can ramp down together at the same time??

They are on separate PLCs too but I can map signals between the PLCs.

Any help appreciated!!

Hopefully you are using S7-1500 PLC with IRT / ISOchronous Profinet communications, SYNC_PI and SYNC_PO for communicating between the 2 S210 drives to keep things all synchronized.

Otherwise, you are likely to have problems forever.

That said, in some situations, remote I/O can be shared across multiple PLCs for READING if you have 2 PLCs that need to coordinate using 1 or more input signals.

Crank up the Profinet comms, configure for IRT / ISO, set the network topology as it's currently connected, and do the work with a cyclic interrupt OB to read synchronous process image input data from the drives, process the new position / speed feedback from both drives, generate new outputs for both drive, and write synchronous process image output data.

That OB3x should call at the same rate as the profinet clock, with an offset a short period of time _after_ the PN data update completes.  You can either experiment, or use the profinet calculated communications parameters to set the offset value for the OB3x that handles the synchronized data I/O.

You need to do the same thing in both PLCs, and they should ideally be the same model so the SYNC_PO outputs happen at about the same time.

If I have said _anything_ you don't know anything about, search this support site for ISO IRT Synchronous communications and control, and hit F1-Help in portal for cyclic interrupt parameters, profinet ISO parameters, and SYNC_PI/PO instructions.

Ideally, you download a sample ISOchronous enabled application from this support site to have a view of the programming and hardware configuration architecture. Otherwise, it's going to be a few days / weeks (possibly) months before you can get it working perfectly on your own.

If you have access to a regional Siemens Applications Engineer or your local Siemens distributor has a drives engineer with ISO experience on s7-1500's, please reach out to them for help.

I have just one system using ISO communications for drives / remote I/O, and it took a lot of learning to make it work flawlessly.

The strange thing about that process is the less code I had, the more flawless the outcome.  By that I mean by optimizing when things gets done - removing code from the OB3x everywhere possible and still get proper performance on things that didn't really need nor could update at the super fast ISO profinet comms rates really pays off in performance of the things that really matter and needed updates at those fast rates.  (I know that's a run-on sentence but hopefully you can make it through it ok after a few read-throughs...)

JackE94

Hi,

I have an application where I have two belts, one behind the other, which run at the same speed and at the same time, for a set distance. (Relative movement).   

On the first belt, I have to stop the belt at a certain variable point and continue the movement when the second belt has ran for 150mm. Once the second belt has ran for 150mm then I continue the first belt.

My velocity is quite high at 800 mm/s, and the accel/deccel/velocity/jerk are matched with one another for both belts.

The problem I have is that the two servos are on separate PLCS, and I am just mapping the technology object encoder value of the S210 across to the slave PLC, once the slave PLC reads this value then I continue the first belt. However when the second belt stops I have to immediately stop the first belt, because the second belt comes to a halt to a relative position it starts to decelerate slowly towards that position, whereas the first belt does not know when to stop, and just stops immediately when the second belt stops, so when the second belt is decelerating to position the first belt is continuing at its normal velocity!

Is there a way of getting the servos to talk to eachother so that the second belt can tell the first belt that it's about to decelerate and they can ramp down together at the same time??

They are on separate PLCs too but I can map signals between the PLCs.

Any help appreciated!!

 Hi,

Thank you so much for the detailed response, I understand everything you said.

Do you know if there is a way within the technology object for the second servo to give an accurate signal when it will begin to deccelerate?

I need an accurate way of getting the first servo to begin its deceleration to 0 velocity at the same time as the second servo.

So basically when the second servo is close to its target and begins to deccelerate towards its final position, if it could give a signal to the first servo and then the first servo will match speed all the way down to 0.

Is this possible via technology object?

0_Einstein

Hopefully you are using S7-1500 PLC with IRT / ISOchronous Profinet communications, SYNC_PI and SYNC_PO for communicating between the 2 S210 drives to keep things all synchronized.

Otherwise, you are likely to have problems forever.

That said, in some situations, remote I/O can be shared across multiple PLCs for READING if you have 2 PLCs that need to coordinate using 1 or more input signals.

Crank up the Profinet comms, configure for IRT / ISO, set the network topology as it's currently connected, and do the work with a cyclic interrupt OB to read synchronous process image input data from the drives, process the new position / speed feedback from both drives, generate new outputs for both drive, and write synchronous process image output data.

That OB3x should call at the same rate as the profinet clock, with an offset a short period of time _after_ the PN data update completes.  You can either experiment, or use the profinet calculated communications parameters to set the offset value for the OB3x that handles the synchronized data I/O.

You need to do the same thing in both PLCs, and they should ideally be the same model so the SYNC_PO outputs happen at about the same time.

If I have said _anything_ you don't know anything about, search this support site for ISO IRT Synchronous communications and control, and hit F1-Help in portal for cyclic interrupt parameters, profinet ISO parameters, and SYNC_PI/PO instructions.

Ideally, you download a sample ISOchronous enabled application from this support site to have a view of the programming and hardware configuration architecture. Otherwise, it's going to be a few days / weeks (possibly) months before you can get it working perfectly on your own.

If you have access to a regional Siemens Applications Engineer or your local Siemens distributor has a drives engineer with ISO experience on s7-1500's, please reach out to them for help.

I have just one system using ISO communications for drives / remote I/O, and it took a lot of learning to make it work flawlessly.

The strange thing about that process is the less code I had, the more flawless the outcome.  By that I mean by optimizing when things gets done - removing code from the OB3x everywhere possible and still get proper performance on things that didn't really need nor could update at the super fast ISO profinet comms rates really pays off in performance of the things that really matter and needed updates at those fast rates.  (I know that's a run-on sentence but hopefully you can make it through it ok after a few read-throughs...)

JackE94

Hi,

I have an application where I have two belts, one behind the other, which run at the same speed and at the same time, for a set distance. (Relative movement).   

On the first belt, I have to stop the belt at a certain variable point and continue the movement when the second belt has ran for 150mm. Once the second belt has ran for 150mm then I continue the first belt.

My velocity is quite high at 800 mm/s, and the accel/deccel/velocity/jerk are matched with one another for both belts.

The problem I have is that the two servos are on separate PLCS, and I am just mapping the technology object encoder value of the S210 across to the slave PLC, once the slave PLC reads this value then I continue the first belt. However when the second belt stops I have to immediately stop the first belt, because the second belt comes to a halt to a relative position it starts to decelerate slowly towards that position, whereas the first belt does not know when to stop, and just stops immediately when the second belt stops, so when the second belt is decelerating to position the first belt is continuing at its normal velocity!

Is there a way of getting the servos to talk to eachother so that the second belt can tell the first belt that it's about to decelerate and they can ramp down together at the same time??

They are on separate PLCs too but I can map signals between the PLCs.

Any help appreciated!!

 

I'm not a Siemens motion control expert.  If I were to attempt such a feat as you describe, I would probably start with Sinumerik rather than Sinamics for coordinated motion control like you are describing.

That said, you may be able to simulate coordinated motion by GET/PUT between the 2 PLCs, also using ISO comms, also updated in the same OB3x as the S210 servos.

In that way, each PLC can be aware of the other servo's position, speed, direction, decision / inflection points reached, and so on as needed for your project to be successful.

If you know how to go bumpless from one motion profile to another motion profile, you can use data from both servos to accomplish that task (assuming you can configure the S210's as I-Devices and provide the same OUTPUT from the drive telegram to BOTH drives).  Or, pass data to their respective PLCs and then the PLCs retransmit it - a profinet clock tick later..

Each PLC would then be empowered with knowledge of both servos at all times, and then can make appropriate adjustments to servo motion control, adjusting motion profiles as required.

JackE94

 Hi,

Thank you so much for the detailed response, I understand everything you said.

Do you know if there is a way within the technology object for the second servo to give an accurate signal when it will begin to deccelerate?

I need an accurate way of getting the first servo to begin its deceleration to 0 velocity at the same time as the second servo.

So basically when the second servo is close to its target and begins to deccelerate towards its final position, if it could give a signal to the first servo and then the first servo will match speed all the way down to 0.

Is this possible via technology object?

...