YASKAWA CIMR-ZU A Series Programming Manual page 38

1 2 b Application
b PI Control
The drive has a built-in Proportional + Integral (PI) controller that uses the difference between the target value and the feedback
value to adjust the drive output frequency to minimize deviation and provide accurate closed loop control of system variables
such as pressure or temperature.
P Control
The output of P control is the product of the deviation and the P gain so that it follows the deviation directly and linearly. With
P control, only an offset between the target and feedback remains.
I Control
The output of I control is the integral of the deviation. It minimizes the offset between target and feedback value that typically
remains when pure P control is used. The integral time (I time) constant determines how fast the offset is eliminated.
PI Operation
To better demonstrate PI functionality, the diagram below illustrates how the PI output changes when the PI input (deviation)
jumps from 0 to a constant level.
Usin PI Control
Applications for PI control are listed in the following table.
Application
Machinery speed is fed back and adjusted to meet the target value. Synchronous control is
Speed Control
performed using speed data from other machinery as the target value
Pressure Maintains constant pressure using pressure feedback.
Fluid Control Keeps flow at a constant level by feeding back flow data.
Temperature
Maintains a constant temperature by controlling a fan with a thermostat.
Control
PI Setpoint Input Met ods
The PI setpoint input depends on the PI function setting in parameter b5-01.
If parameter b5-01 is set to 1 or 2, the frequency reference in b1-01 or one of the inputs listed in
setpoint.
If b5-01 is set to 3 or 4, then the PI setpoint can be input from one of the sources listed in
PI Setpoint Source
Analog Input A1
Analog Input A2
MEMOBUS/Modbus Register 0006 H
Parameter b5-19
A duplicate allocation of the PI setpoint input will cause an oPE alarm.
Note:
8
PI input
PI Output
Fi ure 1 1 PI Operation
Description
able 1 8 PI Setpoint Sources
Set H3-02 = C
Set H3-10 = C
Set bit 1 in register 000F H to 1 and input the setpoint to register 0006 H
Set parameter b5-18 = 1 and input the PI setpoint to b5-19
Time
PI output
I control
P control
Time
Tachometer
Pressure sensor
Flow rate sensor
Thermocoupler,
Thermistor
Table 1.8
Table 1.8.
Settin s
Sensors Used
becomes the PI