Siemens P01-07 User Manual
Industry Automation and Drive Technologies - SCE
TIA Training Manual
Page 1 of 41
Module P01_07
Status: 12/2010
PCS 7 for Universities
S
EQUENTIAL
F
UNCTION
C
HART
O
BJECTIVE
The students will be able to successfully implement sequential controls using step
sequences. The students understand the structure and effect of step sequences, and are
introduced to corresponding design methods. Knowledge about operating modes and
protective measures is expanded for sequential controls. The students understand the
interaction between the programs for basic automation and the sequential controls. They
know how to generate sequential controls in PCS7.
sequences. The students understand the structure and effect of step sequences, and are
introduced to corresponding design methods. Knowledge about operating modes and
protective measures is expanded for sequential controls. The students understand the
interaction between the programs for basic automation and the sequential controls. They
know how to generate sequential controls in PCS7.
T
HEORY IN
S
HORT
Sequential controls allow for processing sequential and parallel operations in a mode that
is discrete with respect to time or events. They are used to coordinate different continuous
functions as well as controlling complex process sequences. Depending on defined states
or events, operating and mode changes are generated in the existing logic control systems
and as a result, the desired sequential performance is implemented. They are implemented
through one or several step sequences (in English: sequential function charts).
is discrete with respect to time or events. They are used to coordinate different continuous
functions as well as controlling complex process sequences. Depending on defined states
or events, operating and mode changes are generated in the existing logic control systems
and as a result, the desired sequential performance is implemented. They are implemented
through one or several step sequences (in English: sequential function charts).
A step sequence is the alternating sequence of steps that trigger certain actions
respectively, and transitions that cause a step to change into another one as soon as the
corresponding step enabling condition is met. Each step sequence has exactly one start
step and one end step and in addition any number of intermediate steps that are
connected respectively through oriented edges by means of interposed transitions. The
diagrams may also generate feedback through loops within the step sequence. They also
can include parallel or alternative branches. However, in this case it has to be ensured
during the design that the sequence does not contain segments that are unsafe or
unavailable.
respectively, and transitions that cause a step to change into another one as soon as the
corresponding step enabling condition is met. Each step sequence has exactly one start
step and one end step and in addition any number of intermediate steps that are
connected respectively through oriented edges by means of interposed transitions. The
diagrams may also generate feedback through loops within the step sequence. They also
can include parallel or alternative branches. However, in this case it has to be ensured
during the design that the sequence does not contain segments that are unsafe or
unavailable.
To design sequential controls, particularly the formal design methods of state diagrams or
Petri’s networks are available. State diagrams are easily learned, make automatic error
diagnosis possible and can be converted without a problem into many existing
programming languages for sequence controls. However, designing parallel structures is
not possible, since state diagrams have only exactly one state.
Petri’s networks are available. State diagrams are easily learned, make automatic error
diagnosis possible and can be converted without a problem into many existing
programming languages for sequence controls. However, designing parallel structures is
not possible, since state diagrams have only exactly one state.
Petri’s networks are considerably more complex and more demanding mathematically. But
all structures that are permitted in sequential controls can be modeled and extensively
analyzed. Thus, required control properties can be proven formally. Likewise, Petri’s
networks allow for no-problem implementation in sequential controls.
all structures that are permitted in sequential controls can be modeled and extensively
analyzed. Thus, required control properties can be proven formally. Likewise, Petri’s
networks allow for no-problem implementation in sequential controls.
Sequential controls parameterize and activate lower level logical control systems by setting
corresponding global control signals. These control signals can have a brief or a lasting, a
direct or a delayed effect. Sequential controls as well as logical control systems have to
support different operating modes. Particularly manual control of the transitions and
temporary or permanent interruptions of the process sequences has to be possible In
addition, process specific protective functions are implemented with sequence controls.
corresponding global control signals. These control signals can have a brief or a lasting, a
direct or a delayed effect. Sequential controls as well as logical control systems have to
support different operating modes. Particularly manual control of the transitions and
temporary or permanent interruptions of the process sequences has to be possible In
addition, process specific protective functions are implemented with sequence controls.
In PCS7, sequence controls are implemented with Sequential Function Charts
(SFC). SFCs provide for efficient operating mode management, high controllability through
several switching modes as well as extensive parameterizability through different sequence
options. The SFCs and CFCs interact and are linked in PCS7 by means of process
variables and control variables. The interactive behavior can also be controlled in detail.
(SFC). SFCs provide for efficient operating mode management, high controllability through
several switching modes as well as extensive parameterizability through different sequence
options. The SFCs and CFCs interact and are linked in PCS7 by means of process
variables and control variables. The interactive behavior can also be controlled in detail.