This is a question that one of our customers at a Water District recently had for us. He was having throttling issues with the S800 panel and wanted to know more about the PID settings. He contacted one of our engineers for help with the theory and operation of the PID settings. Once explained, a small change got his engine running exactly how he wanted. He was thrilled.

The customer uses our standard S800 engine controller. The S800 controller interfaces (via their SCADA system) to remotely start and stop the engines to deliver water to the District’s residents. 

They started using the S800 around 2018, and have been in the process of converting all their pump houses to the S800. This explanation is more specific to the S800, but the concept of PID numbers is common. Our goal was to give the reader a simple but thorough explanation that wouldn't without too much math involved.

Here’s our answer:

P.I.D. stands for proportional, integral, and derivative control. These three values are used by the software routine to provide accurate control of a constantly fluctuating system or process; for example, controlling and maintaining the RPM of your vehicle while it is in cruise control. Original PID theory was developed while observing helmsmen keeping their ships on course through the wind and waves of the ocean. 

In the S800 we use PID to control the RPM of the engine at different stages, while the engine starts, runs, and goes off line autonomously. 

Here is how it works:

Proportional (P): The proportional component is based on the current error between the setpoint and the measured value, and it produces a control output that is proportional to the error. The larger the error, the larger the control output.

Integral (I): The integral component sums up the error over time and produces a control output that is proportional to the integral of the error. The purpose of the integral component is to eliminate any steady-state error that may exist in the system.

Derivative (D): The derivative component predicts the future trend of the error based on its rate of change, and produces a control output that is proportional to the derivative of the error. The derivative component helps to stabilize the system and reduce overshooting and oscillation.

The proportional, integral, and derivative components are combined to create a control output that is used to adjust the system in real-time, and bring the process variable closer to the desired setpoint. The PID algorithm can be tuned by adjusting the parameters of each component to optimize the performance of the system.

To tune the PID settings for throttling in the S800 you will want to run the engine with the S800, and observe its behavior. Take notice of the speed at which the engine RPMs reach the desired set point. The engine should gracefully throttle up or down to its set point RPM and maintain itself as close to the set point RPM as best it can. If it is not there you can tune the one of the PID numbers based on the behavior you notice.

+ Engine tries to catch the RPM set point too fast and tends to overshoot the target?

- Try setting the Proportional number lower.

+ Engine can't catch the RPM set point in time?

- Try setting the Proportional number higher.

+ Engine loses its ability to track the setpoint after running for some time?

- try to adjust the integral set point higher, or lower.

+ Engine RPMs under over/under shoot and never settle in range of the correct RPM?

- try adjusting the Derivative higher or lower.

The default settings in the S800 should work great for most engines, but some engines will need to have the Throttle PID settings be tuned to get the best performance out of the engine. For example a customer installed a new S800 on a station with an engine that they know works. After running the engine they notice a few things that don't seem right. They see the engine approaching the RPM set point very quickly and even overshooting the target by a large amount, sometimes triggering the overspeed alarm causing a shutdown to occur. After looking at the PID set points we noticed that the throttle PID's Proportional set point was 25. After lowering this to 5 the customer saw the engine throttle up gradually at an acceptable speed and no longer overshot the target. One small change to the PID numbers can dramatically change the way the engine is going to run, so keep a record of the changes you are going to make to these settings so you can always return them to the last configuration that worked best.

-------------------

Click Here to see our selection of S800 panels. Many Municipalities use these S800 Panels for their pump/flood/lift Stations. The 800 Series is a Full Featured Municipal Pump Control Panel, designed to work with a multi-engine system. The Series 800 is an all-purpose, highly configurable engine controller, designed to meet the needs of nearly every municipality. The controller is designed to be a municipal-specific control platform and incorporates the necessary hardware to efficiently execute these projects.

-------------------

Don't Miss a Thing!!! 🤩 

Subscribe to our newsletter, follow us on Instagram, LinkedIn, Twitter, and Facebook to keep up to date with our latest News, Sales, Trends and more! Don't forget to check out our Blog archives for more expert informational content.