Siemens Module B3 ユーザーズマニュアル
Automation and Drives - SCE
T I A Training Document
Page 32 of 64
Module
Structogram
A structogram shows the rough structure of a program plan. The structogram below shows the
possible structure of a program for a two position controller.
First, a scan is made whether the controller is switched on.
If it is switched off, only the program is executed in which the outputs and flags are reset.
From the program-engineering view, this is done most simply by means of jump instructions.
If the controller is switched on, the setpoint and actual value are entered, and the calculations for
switching hysteresis, differential and the lower operating point are made.
Then, another scan follows: whether the actual value is below the low operating point.
If this is the case, the controller output is switched on, and a jump is made to the end of the program.
If this is not the case, the high operating point is calculated, and a scan is made whether the actual
value is above the high operating point.
Then, again a jump is made to the end of the program.
A structogram shows the rough structure of a program plan. The structogram below shows the
possible structure of a program for a two position controller.
First, a scan is made whether the controller is switched on.
If it is switched off, only the program is executed in which the outputs and flags are reset.
From the program-engineering view, this is done most simply by means of jump instructions.
If the controller is switched on, the setpoint and actual value are entered, and the calculations for
switching hysteresis, differential and the lower operating point are made.
Then, another scan follows: whether the actual value is below the low operating point.
If this is the case, the controller output is switched on, and a jump is made to the end of the program.
If this is not the case, the high operating point is calculated, and a scan is made whether the actual
value is above the high operating point.
Then, again a jump is made to the end of the program.
Controller switched off?
YES NO
Outputs
and
Flags
Display: Switch on SH10
Enter actual value x and
setpoint w
Normalize
Clear
Calculation of the switching hysteresis Xs = w/10
or
Calculation of half the differential X1 = Xs/2
Reset
Calculation of the low operating point Xu = w - X1
Is the actual value less than the low operating point?
YES NO
Pump ON
Calculation of the high operating point Xo = w + X1
Actual value X larger than Xo?
YES
NO
Pump
OFF
Preface Fundamentals Discontinuous Action Controllerr Controller Block (S)FB41 Setting the System Appendix
B3
Issued: 02/2008 Control Engineering with STEP 7