16.01.2023

Open source PLC emulator for SAP EWM MFS in action

The article Free, open source PLC emulator for SAP EWM MFS has introduced the PLC Sim project. It is available on GitHub in the repository mfs-plc-sim.

Now, let’s see how the emulator can be used to automate a stock placement process with two different PLCs: a conveyor and a stacker.

SAP EWM MFS initial setup has been implemented with the /SCWM/MFS BC set. Despite a warning from the 2464460 – Restricted usage of BC sets in embedded EWM in S/4HANA and in de-central EWM note:

BC sets for SAP-internal test purposes in EWM

In de-central EWM and in embedded EWM in S/4HANA, the following BC sets contain customizing entries used for SAP-internal test purposes only:

/SCWM/MFS
/SCWM/MFS_ACTIONS_DEF
/SCWM/MFS_ACTIONS_DET
/SCWM/MFS_ACTIVITIES

the BC set can be activated in S/4HANA embedded EWM and works very nicely as a jumping point of a MFS demo configuration.

I have enhanced a bit the storage process to implement the following scenario with two automated legs:

The storage process is composed of 4 points:

A – unloading zone
B – conveyor entry
C – conveyor exit
B – final destination zone

and of 3 legs:

1 – manual movement from the unloading zone and placement on the conveyor
2 – transportation by the conveyor to the automated warehouse stacker
3 – placement into the final bin by the automated stacker

The process is modelled with the following setup of layout-oriented storage control:

The demo uses the following telegram styling:

LIFE, handshake request – red, bold
LIFE, handshake acknowledgement – red, italic
WT, handshake request – black, bold
WT, handshake acknowledgment – black, italic
WTCO, handshake request – green, bold
WTCO, handshake acknowledgment – green, italic

The is setup with the properties in the Sim application configuration file:

Style.LIFE-R.=255,0,0,B
Style.LIFE-A.=255,0,0,I
Style.WT..-R.=0,0,0,B
Style.WT..-A.=0,0,0,I
Style.WTCO-R.=0,255,0,B
Style.WTCO-A.=0,255,0,I

Two instances of Sim application are started:

one for the conveyor and
one for the stacker.

The conveyor communicates on the TCP/IP port 7000, the stacker on the port 6969. TCP/IP servers are stopped for now in the Sim applications. That is indicated by input ready TCP/IP field with white background.

Both channels are stopped in SAP EWM MFS too:

I am starting the TCP/IP servers in the Sim applications. The TCP/IP field gets read-only with yellow background, that indicates running TCP/IP server but without TCP/IP client connection yet.

The channels are started in /SCWM/MON

The TCP/IP port field in the Sim application turns green indicating the connection of TCP/IP client, which is SAP EWM MFS. LIFE telegrams start flowing:

The process in EWM begins with an inbound delivery with one handling unit

The handling unit number is 112345671000000286

Warehouse task is created for the handling unit:

Notice that the system actually creates two warehouse tasks:

to the storage bin 0280 028-02-08, which is our final destination bin
to the storage bin 0285 I-POINT, which is poin B of the placement process, i.e. the beginning of the conveyor segment

The same is visible in /SCM/MON in the Warehouse Task node:

The warehouse task 1576 to the 0280 0280-02-08 bin, which is the final bin of the placement hast the B “waiting” status. The warehouse task cannot be currently executed as it waits for layout oriented process to finish.

The warehouse task 1577 confirmation:

Upon the warehouse task 1577 confirmation, SAP EWM automatically creates the task 1578, from 0285 I-POINT, to 0285 C-POINT, that is for the second leg of the placement process. This leg is integrated with the conveyor. So a telegram is sent to the corresponding PLC:

Notice that automatic handshake mode is activated in the emulator. 
Therefore the handshake confirmation is automatically to SAP EWM MFS.

The telegram content can be analyzed in the structured display popup by double clicking the corresponding line number

The conveyor leg is confirmed now with WTCO telegram. The telegram can be either entered directly in the “Outgoing Telegram” text field or edited more conveniently in the structured edit popup

Receipt of the WTCO telegram is confirmed by SAP EWM MFS with the handshake acknowledgement telegram

Notice the styling of the telegrams.

The WTCO telegram processing the warehouse task 1577 and unblocks the first 1576 task. At the same time the source location of the warehouse task 1576 is changed to 0285 C-POINT

Activation of the warehouse task 1576 generates its WT telegram, that is sent to the stacker PLC. Again the communication is automatically confirmed with the handshake acknowledgment