Tuning a PID controller can be daunting. The first step may be figuring out where to start. Fortunately, this article provides an accessible and comprehensive guide to setting up a PID controller from scratch.
It’s important to note that while many possible values may work on a given device, the goal is not to find the “ideal” deals but rather to find those that meet the requirements and provide the required control. With this article, you will be well on your way to mastering the complexities of PID controllers and efficiently using their potential.
Finding Initial PID Values
For best performance, ensure all mechanical components are in perfect working condition before attempting to find initial PID values. Trying to tune PID values to fix an underlying mechanical issue will likely lead to poor results. Instead, once all mechanical elements are verified, you can start programming for the optimal PID values.
Proportional
Proportional Gain Tuning
Start by setting both the Integral and Derivative values to 0. Then, increase the proportion gradually until the controller becomes unstable and displays oscillatory behavior. Monitor the system carefully and adjust the values accordingly to maintain optimal performance.
A controller is considered stable when its oscillations become smaller and eventually stabilize. On the other hand, when the fluctuations become more significant, the controller is deemed unstable. By using a stable controller, you can ensure that the system will remain in a predictable equilibrium.
Once you’ve identified the proportional value causing your controller to oscillate, divide this value in half to get the starting P value. This will help you to reduce the amount of oscillation in the controller and provide a more stable system.
Integral
Integral Gain Tuning
Once the proportional cost is identified, it is time to track the integral. Again, remember to take small steps when adjusting a PID controller and wait a few minutes between adjustments to observe the controller’s response. Doing this helps identify any unexpected issues and can prevent overshooting and oscillations.
Increase the integral gain in small, incremental steps, and adjust the set point with each adjustment. Doing this lets, you monitor how the controller responds to the changes.
Integral values are tuned to ensure a fast and accurate controller response or reaction time. By optimizing the integral value, the initial proportional response can be established quickly and efficiently, enabling a controller to react rapidly to any changes in the system. This helps improve the control system’s performance and stability and reduces the risk of unexpected events.
If the controller begins oscillating or becoming unstable, adjust the I value in the opposite direction until it is stable and responding as desired. Once the controller is stable and operating correctly, you have a working PI controller that functions optimally.
Derivative
Derivative Gain Tuning
If your application requires the dampening effects of a derivative, then you need to find the right PI controller. Many are available on the market, but the right one will depend on the specific application you need. Finding the correct value that works for your application can be tricky, but it’s worth the effort to ensure you get the most out of your system.
Having established a stable PI controller, start gradually increasing the derivative value. After that, adjust the set point and give the controller some time to stabilize. Remember that changing the set point too quickly can lead to poor control performance, so take your time and ensure that the controller is at peak efficiency.
The D value is used to monitor and regulate the rate of change of the process value, ensuring that it doesn’t exceed the set point. It works by continuously measuring the difference between the current process value and the set point and then adjusting the rate of change accordingly to prevent overshooting. By doing this, the D value helps to ensure that the process value stays within the desired range.
Adjust the set point and increase the derivative until the overshoot has been dampened to an acceptable level. If the controller exhibits negative behavior, reduce the D value until the controller is stable again. Monitoring the system’s response can help you identify the optimal settings to ensure reliable and accurate control.
Be mindful when tweaking the derivative value – it may be tempting to increase it for a smoother controller response. However, too high of a derivative can begin to have a detrimental effect on the output and potentially conflict with the desired outcomes of the P and I values.
The other issue with a high D value is that if there is noise or distortion in the process value feedback, the derivative may misinterpret this as a rapid change in the ramp rate and cause the output to be biased at an undesired time. This can be particularly problematic if the output is controlling a critical process. To minimize this risk, ensuring that the feedback loop is calibrated correctly and free from interference is essential.
Advanced Tuning of a PID Controller
Fine-tuning a PID controller to its optimal performance requires a deep understanding of how it works and the variables that affect it. Then, with the initial values established, you can experiment with different settings and simulations to see how it reacts.
By observing the controller’s response, you can gain insight into which values should be adjusted to make it perform better. There is no one-size-fits-all formula for advanced PID controller tuning, but with practice and a keen understanding of its functions, you can gain the necessary skills to get the most out of it.
If the PID controller’s initial response is fast, but the next seconds are slow to react, the integral value needs adjusting.
If the PID controller’s initial response is slow, try increasing the proportional value. Take note that when the proportional gain is increased, it is recommended to run tests to see if the derivative gain must also be improved to prevent overshooting.
PID controller is overshooting:
If you see an overshoot in your PID controller, the first step is to look at the initial response. If it’s too high, you can reduce the proportional or integral values to bring it back into line. If the reaction time is good, however, and the controller is stable, you may need to increase the derivative slightly, which should help dampen the overshoot.
PID controller is not stable or oscillating:
Troubleshooting an unstable or oscillating PID controller can take time and effort. Before adjusting any of the controls, double-check for any external or physical forces causing the issue. This could include things like vibrations, electrical interference, or mechanical issues. Taking the time to identify the source of the problem correctly will save you valuable time and energy in the long run.
If the oscillations you’re seeing are caused by the output spiking suddenly to 100%, then abruptly dropping back to 0%, it’s likely that the proportional gain is set too high. To improve the stability of your controller, start by decreasing the derivative gain to a low setting. Once that’s done, reduce the proportional gain until the controller becomes more stable.
If the output of your controller is spiking slowly but is overshooting or undershooting, then the integral gain is likely too high. To achieve stable production, decrease the necessary gain until it is steady. Doing this will help you get the most accurate results from your controller.
You can reset the PID values and set up the PID controller from scratch if everything fails. To do this, follow the steps outlined above. This will ensure the PID controller is configured correctly and can be used to its maximum potential.
BCST PID Controllers
BCST is a leading Chinese brand specializing in the research, development, and manufacturing of PID controllers with over 20 years of experience. BCST PID controllers are one of the most widely used tools in a variety of industries, engineering, manufacturing, and science, making them an invaluable resource for any application. If you would like to learn more about BCST PID controllers, then please visit our website at www.bcstvalve.com and take advantage of the expertise and knowledge that BCST has to offer.