[DB600] General instruction manual
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6-6-3
D control
D control is used to make output at a level proportional to the variation of deviation. It determines the
response performance to disturbance.
Dead time or phase lag caused by lag element is compensated. The output level is limited, however,
because the gain increases in the high frequency area.
Setting "0" is equivalent to OFF.
Generally, D value is set to 1/6 to 1/4 of I value.
Prompt response to disturbance but overshoot or vibration is
likely when derivative time is too large.
Slow response to disturbance when derivative time is too
small.
Derivative time means the time required for the output variation by P
control to become equal to that by D control when the deviation is
given with a constant slope in PD control.
Setting a larger derivative time improves response to disturbance, but
it degrades control performance against vibration or overshoot.
Time
Increase
Output
Decrease
Derivative
time small
Derivative
time large
Output variation by P control
Output variation by D control
Derivative time
Time
