Understanding Closed-Loop Control Systems

A control system manages or regulates the behavior of many devices you use every day — from lightbulbs or thermostats to the engine in your car or industrial generators. Control systems operate in two ways: as open-loop control systems or closed-loop control systems.

An open-loop control system is a one-way signal flow system, meaning that an input is given to a controller which begins a process, leading to a final output. An example of an open-loop control system is a timed, electric clothes dryer. The input is the amount of time the dryer is set to run. An input of 30 minutes controls the heating elements for the duration of the process, at which point the output is clothes that are more dry.

The challenge with an open-loop system is that it does not send feedback to adjust or regulate the output. With a timed dryer, if the clothes are still somewhat damp after 30 minutes, there is no feedback signal returning to the controller to tell the timer to run longer.

In this case, a closed-loop control system is ideal because a closed-loop system sends signals back to the controller and regulates the processing system to achieve a desired output.

What is a Closed-Loop Control System?

A closed-loop control system is a system in which the control action is dependent on the feedback from the output.

In a closed-loop control system, sensors are used to measure the system’s output. An error detector then compares the quantity of the actual output, called the feedback signal, to an input reference (or the desired output). If the feedback signal does not match the input reference, an error signal will be sent to the controller with the difference between the two signals. The controller then makes the necessary adjustment to the system.

By monitoring the output and using feedback to control the processing system, a closed-loop control system can more accurately produce the system’s desired output, while reducing error and accounting for external changes.

Using feedback to reduce errors within a system is critical for engines that need to be regulated regardless of external disturbances, like spark ignition (SI) engines.

Advantages of a Closed-Loop System on Gaseous Generators

Prior to using closed-loop control systems in gaseous generators, SI engines fed fuel through a carburetor to mix with air. In this open-loop system, no measurements are taken to gauge the mixture of fuel to air, leading to poor fuel management and increased emissions from insufficiently burnt fuel.

Today, the majority of SI engines in gaseous generators use closed-loop control systems. Whether a gaseous generator is fueled by natural gas or liquid petroleum gas, the feedback sent along the system flow offers closed-loop system advantages because it effectively regulates the engine’s output.

A closed-loop control system in an engine can adjust and regulate inputs to produce the desired combustion output — even if there are variations in ambient temperature, load, altitude, or humidity. With sensors that read engine speed, fuel content, oxygen in the exhaust, cylinder pressure, and other variables, the fuel throttle can be controlled to provide exactly the correct mixture of fuel and air for the power required.

This results in greater power strokes, improved fuel efficiency, and reduced emissions from SI engines in gaseous generators.

Maintaining a Closed-Loop Control System

Properly maintaining a closed-loop control system helps the system achieve maximum efficiency, but it also ensures your generator meets operational standards and emission regulations for stationary and mobile generators.

Understanding the components of your closed-loop systems and the applicable sensor functions will help you keep SI engines for gaseous generators running at their desired output levels. You can also follow our generator maintenance checklist to confirm your facility is taking the appropriate steps to maintain optimum performance.

As an authorized distributor of gaseous generators in Ohio, Illinois, and Indiana, Buckeye Power Sales offers planned maintenance programs for SI engines with closed-loop control systems. During regularly scheduled maintenance, certified technicians will verify that the ignition system is operating to its original OEM specifications to keep the engine operating at maximum efficiency.

Download the Info Sheet

Buckeye Power Sales has resources available to help you learn more about gaseous generators and their components. Download our information sheet to read more about the key sensors that can regulate SI engines via their closed-loop control systems.