Derivative Operation (D Operation) - Mitsubishi Electric MELSEC-Q series Programming Manual

Derivative operation (D operation)

The control method for derivative operation is described below.
Derivative operation
• In derivative operation, an MV (manipulated value) proportional to the deviation change rate is added to the system value to
zero deviation when it occurs. This operation prevents significant fluctuation at the control objective due to external
disturbances.
• The time required for the MV in the derivative operation to reach the MV for the proportional operation after the generation
of deviation is called the derivative time. Derivative time is expressed as T
Condition
When derivative time T is shorter
D
When derivative time T is longer
D
• The derivative operation when the deviation is a constant value stepped response is shown below.
• Derivative operation is always used in combination with proportional operation (PD operation) or with proportional and
integral operations (PID operation). Derivative operation cannot be used independently.
.
D
Derivative Operation
Differentiating effect decreases.
Differentiating effect increases. However, hunting of short cycle is more likely
to occur.
4 FUNCTIONS OF PID CONTROL
4.2 Functions of PID Control
4
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