PID Settings

PID is a control algorithm used to maintain a system at its desired setpoint by continuously adjusting the output to react to real-time conditions (image 1.1). When controlling motors via VFDs, PID enables smooth and precise regulation of pump speed based on parameters such as pressure, flow, or level.

This control method minimizes fluctuations, improves stability, and ensures consistent system performance by automatically compensating for variable changes and disturbances, resulting in efficient and reliable operation.

1.1 PID button

PID Gain and Integration

When tuning the PID control in the PID settings screen, two primary parameters are adjusted to achieve smooth and stable motor operation (image 1.2):

Gain:
Determines how aggressively the system responds to errors. Higher gain results in a faster response but may cause overshoot or oscillations, while lower gain provides a smoother response but may be slower to react.

Integration:
Controls how the PID responds to accumulated errors over time. Proper adjustment helps eliminate steady-state errors and improves stability. Too much integral action can cause overshoot, while too little may lead to persistent offset.

All motors configured with a VFD will be displayed on this screen, allowing operators to fine-tune their control parameters for optimal performance. Additional setpoints and parameters will be discussed below to ensure comprehensive tuning and system stability.

1.2 PID screen

Gain

The gain parameter (image 1.3) directly influences how the control system responds to the difference between the current process variable (e.g., pressure) and the setpoint. It determines the proportional response of the output:

Lower Gain:
Produces a more gradual response, reducing overshoot and undershoot, and allows the PLC to target a value closer to the setpoint. While this results in a slower approach to the target, it minimizes oscillations and provides stability.

Higher Gain:
Increases the system's responsiveness, allowing the process variable to reach the setpoint more quickly. However, excessive gain can cause the VFD to ramp up and down rapidly, leading to oscillation and instability, making the control less smooth.

Optimal gain settings balance speed and stability, ensuring responsive yet stable control without causing excessive oscillation or sluggish behavior.

1.3 Gain

Integration

The integration parameter, often called the I time, determines how quickly the control system responds to accumulated errors or offsets from the setpoint (image 1.4). When the system is stable but shows a slight offset, increasing the I time causes the controller to apply corrections more rapidly, helping the process variable move closer to the target value.

However, setting the I time too high can lead to overshoot and oscillations, while setting it too low results in slower correction and may leave the process offset for longer periods. Adjusting the I time allows fine-tuning of how quickly the control system reacts to persistent errors, balancing responsiveness with stability for optimal process regulation.

1.4 I time

Derivative

The derivative component (image 1.5) predicts future process behavior by reacting to the rate of change of the process variable. When external disturbances cause rapid fluctuations, increasing the derivative value enhances the system’s ability to respond quickly, helping it recover to the setpoint more rapidly. Conversely, decreasing the derivative value results in a more gradual response, reducing potential overshoot and oscillations caused by sudden changes. Proper adjustment of the derivative helps stabilize the control loop during abrupt process variations, ensuring smooth and responsive operation.

1.5 Derivative.

PV Setpoint Deviation (min and max)

The PV (Process Variable) (image 1.6) setpoint deviation setting allows the user to adjust how sensitive the control system is to deviations from the target setpoint. Lower values restrict the system to respond more precisely when the PV is very close to the setpoint, making it highly reactive to small fluctuations. Higher values widen the acceptable range and reduce the system’s reaction to minor changes, resulting in a more gradual and stable response.

Since each station may have different configurations and operational characteristics, adjusting this setting provides a customizable way to calibrate the control loop. It ensures the station operates smoothly and efficiently, tailored to its specific build and process requirements.

1.6 Setpoint deviation