Delta C2000 Series User Manual page 536

Concept of PID control
 Proportional gain (P):
The output is proportional to input. With only proportional gain control, there is always a
steady-state error.
Adjustment: Turn off the Ti and Td, or remain Ti and Td in constant value, then adjust the
proportional gain (P).
Increase: Faster status feedback, but excessive adjustment will increase the overshoot.
Decrease: Smaller overshoot, but excessive adjustment will slow down the transient
response.
 Integral time (I):
The controller output is proportional to the integral of the controller input. To eliminate the
steady-state error, add an "integral part" to the controller. The integral time controls the
relation between integral part and the error. The integral part increases over time even if
the error is small. It gradually increases the controller output to eliminate the error until it is
zero. This stabilizes the system without a steady-state error by using proportional gain
control and integral time control.
Adjustment: The integral time (I) accumulates from the time difference, if the vibration cycle
is longer than the setting for integral time, the integration enhances. Increase
the integral time (I) to reduce the vibration.
Increase: Reduce the overshoot, excessive adjustment causes worse transient response.
Decrease: Faster transient response, but the transient time will be longer, and takes more
time to achieve the steady state. Excessive adjustment causes larger
overshoot.
 Differential control (D):
The controller output is proportional to the differential of the controller input. During
elimination of the error, oscillation or instability may occur. Use the differential control to
suppress these effects by acting before the error. That is, when the error is near zero, the
differential control should be zero. Use proportional gain (P) and differential control (D) to
improve the system state during PID adjustment.
Adjustment: When the vibration cycle is shorter and continuous, it means that the
differential time setting is too large, and causes excessive output. Decrease
the setting of D gain to reduce the vibration. If the D gain is set to 0, adjust the
PID control again.
Using PID control in a constant pressure pump feedback application:
Set the application's constant pressure value (bar) to be the set point of PID control. The
pressure sensor sends the actual value as the PID feedback value. After comparing the PID set
point and PID feedback, an error displays. The PID controller calculates the output by using
proportional gain (P), integral time (I) and differential time (D) to control the pump. It controls the
drive to use a different pump speed and achieves constant pressure control by using a 4–20mA
signal corresponding to 0–10 bar as feedback to the drive.
Chapter 12 Description of Parameter SettingsC2000
12.1-08-3