Sampling time pulse generator
The sampling time pulse generator must agree with the time tact of the cyclic interrupt OB
being called. The duration of the created impulse is always a whole number factor of this
value. For an adequately precise manipulated value resolution, the following relationship
should apply:
CYCLE_P ≤ PER_TM/50
Minimum impulse/break duration
Through the minimum impulse/break duration, short on or off times on the actuator are
avoided. An impulse smaller than P_B_TM is suppressed.
Recommended are values P_B_TM ≤ 0.1 × PER_TM.
Period duration
The period duration should not exceed 20% of the determined integration time of the
controller (TI):
PER_TM ≤ TI/5
Example for the effect of the parameter CYCLE_P, CYCLE and PER_TM:
Period duration PER_TM = 10 s
Sampling time PID-algorithm CYCLE = 1 s
Sampling time pulse generator CYCLE_P = 100 ms.
Every second, a new manipulated value, every 100 ms the comparison of the manipulated
value occurs with the previously emitted impulse length and break length.
● If an impulse is emitted, there are 2 possibilities:
– The calculated manipulated value is larger than the previous impulse length/PER_TM.
– The calculated manipulated value is less than or equal to the previous impulse
● If no impulse is emitted, there are also 2 possibilities:
– The value (100 % - calculated manipulated value) is greater than the previous break
– The value (100 % - calculated manipulated value) is less than or equal to the previous
See also
Mode of operation TCONT_CP (Page 472)
Operating principle of the pulse generator (Page 481)
PID control
Function Manual, 03/2017, A5E35300227-AC
Then the impulse is extended.
length/PER_TM. Then no impulse signal will be emitted.
length / PER_TM. Then the break is extended.
break length / PER_TM. Then an impulse signal will be emitted.
Using PID basic functions
7.3 TCONT_CP
221