B5: Pid Control - YASKAWA GA700 Technical Manual

11.3 b: Application
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b5: PID Control

The drive is equipped with a PID control function. The user can control drive output so that the target value
matches the detected value by adjusting the proportional gain, integral time, and derivative time that affects the
bias between the target value and the feedback value. Use this function to adjust the drive output so that the flow,
pressure, and temperature in the application match the target value precisely.
Optimize performance by using a combination of the following controls.
• P control
P control affects the deviation proportionally. It outputs the product (the controlled output) proportional to the
deviation. The user cannot reach zero deviation by using only the offset from P control.
• I control
I control is the integral of the deviation. It outputs the product (the controlled output) using an integral value of
the deviation. I control is effective in getting the feedback value and the target value to match. Although using
only proportional control (P control) creates an offset, combining it with integral control eliminates the offset by
using a time constant.
• D control
D control is the derivative of the deviation. D control has a large affect on drive output for when there are
sudden, drastic changes in the output. It quickly restores drive output to what it was before the sudden change. It
multiples a time constant by a derivative value of the deviation (slope of the deviation), and by then adding that
result to PID input, D control calculates the deviation of the signal, and corrects the deviation.
Note:
D control has a tendency to cause less stable operation due to noise affecting the deviation signal. Use D control only when necessary.
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PID Control Operation
The following diagram demonstrates PID control operation. The modified output (output frequency) changes as
shown as the drive uses PID control to keep the deviation (the difference between the target value and the
feedback value) constant.
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PID Control Applications
The followings are applications for the PID control feature.
Application
Speed control
Pressure control
618
Figure 11.34 PID Control Operation
Table 11.23 PID Control Applications
Description
• The drive uses a feedback signal for the
machine speed, and adjusts that speed so
that it matches the target value.
• The drive performs synchronous control
by using speed data from other machinery
as the target value. The drive then
combines that target value with the
feedback from the machine it is operating
to match its speed with that other
machinery.
The drive maintains constant pressure by
using feedback from the actual pressure.
YASKAWA ELECTRIC SIEP C710617 01B YASKAWA AC Drive GA700 Technical Manual
Sensors Used
Tacho generator
Pressure sensor