Industry Automation and Drive Technologies - SCE
subsequent transition of an active step automatically sets an operator prompt (O = Operator).
–Switching Mode T or O: The sequence control is running process controlled or operator controlled. The transition is enabled either through an operator command or a step enabling condition that was met.
–Switching Mode T and O: The sequence control is running process controlled and operator controlled. The transition is enabled only based on an operator command and if the step enabling condition is met.
–Switching Mode T/T and O: In this switching mode we can specify for each step individually whether the sequence is controlled by the process or the operator. In the test mode, this allows for defining stop points in the sequence control (T/T = Test Transactions)
In the operating mode Auto, only the switching modes T and T/T and O can be selected. The operating mode of the sequence control indicates the current state in the sequence and the resulting performance. A corresponding operating mode logic defines the possible modes, the permissible transitions between the modes as well as the transitional conditions for a mode change. PCS7 defines a separate operating mode logic for sequence controls and for step sequences respectively. It is possible to run step sequences depending on the mode of the sequence control.
Sequence Options
By using sequence options, it is possible to control the execution time performance of sequence controls. For example, we can specify whether a sequence control is processed once or cyclically (option cyclical mode) or whether the actions of the active step are actually performed (option command output). In addition, time monitoring for the individual steps of a step sequence can be activated which signals a step error if there is a timeout (option time monitoring).
Interaction Performance
In the PCS7, CFCs and SFCs interact by means of process values and control values. These values are linked by means of the desired signals either from the global symbol table or by entering the absolute signal address. Controlling the processing of the control signals is possible by means of the SFC characteristics. In the SFC Library, the PCS7 makes available preassembled step sequences for different standard scenarios. These templates can be used and adapted to current projects.
LITERATURE
[1]Seitz, M. (2008): Speicherprogrammierbare Steuerungen. Hanser Fachbuchverlag
(Programmable Logic Controllers. Hanser Technical Publications)
[2]Wellenreuther, G. and Zastrow, D. (2002): Automatisieren mit SPS: Theorie und Praxis. Vieweg+Teubner (Automating with PLC. Theory and Practice. Vieweg+Teubner Publishers)
[3]Uhlig, R. (2005): SPS - Modellbasierter Steuerungsentwurf für die Praxis: Modellierungsmethoden aus der Informatik in der Automatisierungstechnik. Oldenbourg Industrieverlag (Model Based Control Design in Practice: Modeling Methods from Computer Science in Automation Engineering. Oldenbourg Industrial Publishers)
[4]Siemens (2009): Process Control System PCS 7: SFC for SIMATIC S7.
TIA Training Manual | Page 7 of 41 | Module P01_07 |
Status: 12/2010 |
| PCS 7 for Universities |