Figure 4. The protocol stack of MOTIP
The implemented MMS services are as follows: virtual manufacturing device (VMD) service for the status acquisition of a networked machine, domain service for file transfer, program invocation (PI) service for the remote execution of a program, and miscellaneous services for reading and writing services of device status and operations. PI services includes creation, initialization, termination, and deletion of a remotely executed program. PI service can be carried out with other services. For example, the remote execution of specific program can be performed after downloading the status and segment service using VMD and Domain service. Fig. 5 shows the execution of the VMD, the Domain, and the PI services in the MOTIP program.
Figure 5. Screenshot of the MOTIP-based central control program
The implementations of the MMS-CS VRMs are based on the MMS services specification in -. Specifi- cally, the services of the implemented MMS-CS VRMS consist of: VMD, Domain, PI, and miscellaneous services. The implemented services are as follow:
VMD services (3): Status, Identify, and Unsolicited Status
Domain service (5): Initiate Download, Download Segment, Terminated Download, Initiated Upload Seg- ment, and Terminate Upload
PI services (4): Create, Start, Stop, and Delete Variable service (2): Read, and Write
Semaphore, Operator, Event, and Journal services have been implemented partially only.
The virtual factory communication system is operated by controlling each VRM with MOTIP based commu- nication programs. Fig. 6 to Fig. 9 show reference models of practical machines. Fig. 10 to Fig. 14 show virtual miniatures of the practical machines. The application program of Robot CS VRMs are modelled after a 6-axis