Learn effective troubleshooting techniques for erratic behavior in PID-controlled systems within control engineering.

As a first step, I suggest controlling the system with a pure proportional controller by setting both the integral and derivative components to zero. Ensure that the system can be controlled with this setup. Then, gradually increase the integral gain and only use the derivative component if it is essential. If you use a PI or PID controller and the actuators become saturated due to high gains, it is advisable to implement anti-windup in your PID controller.

Last updated on Jul 10, 2024

You're facing erratic behavior in a PID-controlled system. How can you effectively troubleshoot it?

When your PID (Proportional, Integral, Derivative) controlled system starts acting up, it's a signal that something within the loop requires attention. Erratic behavior can manifest as overshooting, oscillation, or sluggish response, which can compromise the efficiency and safety of your operations. Troubleshooting this requires a methodical approach, where you'll need to examine each component of the PID loop, understand the nature of the disturbance, and apply corrective measures. With some patience and technical know-how, you can restore stability and precision to your control system.

1 Check Inputs

Begin your troubleshooting by checking the system inputs . Ensure that sensors are functioning correctly and providing accurate data. Erroneous input can cause the controller to make inappropriate adjustments. Look for signs of wear, damage, or calibration drift in sensors. Also, verify that the wiring and connections are intact and free from interference. Correct input data is crucial for the PID controller to make accurate decisions; without it, the system cannot maintain the desired setpoint.

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Kamyar Nikzadfar

Assistant Professor in Automotive Electrification and Control at the University of Warwick, WMG (PhD, CEng, MIMechE, SFHEA)
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As a first step, I suggest controlling the system with a pure proportional controller by setting both the integral and derivative components to zero. Ensure that the system can be controlled with this setup. Then, gradually increase the integral gain and only use the derivative component if it is essential. If you use a PI or PID controller and the actuators become saturated due to high gains, it is advisable to implement anti-windup in your PID controller.

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Ali Salavati-Zadeh
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Without exception and always, the problem I found when checking the inputs was interference in wirings and connections. I am not considering myself as an expert but I always bring this into consideration.

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Manoj Dabir, MBA

Sales Enabler | Passionate about creating strategic partnerships that drive market share and revenue growth.
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Reliable sensor measurement is critical in a PID driven control loop system . If the sensor reading is inaccurate or drifting the process efficiency and performance will be compromised leading to wastage, downtime and additional costs. Keep sensors maintained and calibrated to stay on top of potential issues .

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2 Review Settings

Next, review the PID settings . The proportional, integral, and derivative parameters must be tuned to match the dynamics of your process. If these settings are incorrect, the controller may react too aggressively or too sluggishly. Use a systematic tuning method , such as the Ziegler-Nichols technique , to find the optimal values. Remember that changes in the process or equipment might necessitate re-tuning to maintain optimal performance.

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3 Analyze Output

Analyzing the control output can provide insights into erratic behavior. Look for patterns such as cycling or random fluctuations in the actuator or control element. Ensure that the output device is capable of responding appropriately to the controller's commands. If the output device is too slow or too fast, it can cause instability. Mechanical wear or electrical issues with actuators can also lead to erratic control.

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4 Inspect Feedback

Inspecting the feedback loop is essential for diagnosing issues. Ensure that the feedback signal accurately reflects the system's response to the control actions. Any delay or noise in the feedback can cause the controller to overcompensate, leading to oscillations. Check for proper sensor placement and that the feedback mechanism is free from disturbances that could corrupt the signal.

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5 Evaluate Dynamics

Understanding the dynamics of your system is vital. Some processes have characteristics such as dead time , where there's a delay between the control action and the observed effect. If your PID controller isn't accounting for these dynamics, it will struggle to control the process effectively. Evaluate whether your system has changed in ways that might require a different control strategy or additional tuning.

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6 Address Noise

Finally, address any noise in the system. Electrical noise can interfere with signal transmission, causing erratic readings and unpredictable behavior. Ensure that cabling is properly shielded and grounded. Also, consider external factors that may introduce noise or disturbances into the system, such as nearby equipment or environmental conditions. Minimizing noise will help ensure that your PID controller can operate smoothly.

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7 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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You're facing erratic behavior in a PID-controlled system. How can you effectively troubleshoot it?

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1 Check Inputs

2 Review Settings

3 Analyze Output

4 Inspect Feedback

5 Evaluate Dynamics

6 Address Noise

7 Here’s what else to consider

Control Engineering

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