What is the difference between noise and disturbance

Noise, on the other hand, makes the process variable appear to deviate from the setpoint whether any real disturbance is at work or not. Noise is generally a result of the technology used to sense or measure the process variable. With electrical signals, measurement noise is often due to interference from other electrical sources.

Noise can also be caused by wear and tear on the sensor or some physical obstruction that causes the sensor to send an inaccurate reading to the controller. Errors between the setpoint and the process variable also occur when the setpoint changes.

It is the random nature of disturbances and the fictitious effects of noise that make feedback controllers work so hard. Consider a large truck being driven down the highway through a crosswind. Such setpoint changes are relatively easy for him to make, assuming he knows how the truck will react when he turns the steering wheel. However, a strong wind can blow the truck off the course the driver has chosen to follow. To compensate for such disturbances, the driver must adjust his steering to correct his position errors.

Now suppose the wind is accompanied by snow. The driver may not be able to see the white lines very well, so he may end up changing his course to compensate for a nonexistent position error. In a more typical process control situation, a PID controller is responsible for applying a corrective effort in proportion to the error between the process variable and the setpoint plus the integral and derivative of that difference.

It is the derivative action that is most affected by noise and disturbances. On the plus side, a PID controller tuned to provide aggressive derivative action can react quickly to an error and start the control effort moving in the right direction immediately after a disturbance begins. This can shorten the time required to compensate for a disturbance compared to a controller that uses only proportional and integral action.

However, the derivative action will amplify any noise embedded in the measurement, since the derivative of a fluctuating signal also fluctuates.

This can lead to unnecessary and potentially counter-productive control efforts. Most PID controllers are equipped with noise filters to suppress extraneous fluctuations that the derivative action would otherwise generate.

VanDoren, Ph. An everyday example Consider a large truck being driven down the highway through a crosswind. PID control In a more typical process control situation, a PID controller is responsible for applying a corrective effort in proportion to the error between the process variable and the setpoint plus the integral and derivative of that difference.

Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It only takes a minute to sign up. Connect and share knowledge within a single location that is structured and easy to search. According to your image, disturbance acts on a controller output, while noise acts on a process output. Take a moving vehicle for example - obstacle on the road would be a noise, and some unexpected event in the engine, gas tank etc.

MrYouMath's answer is the most accurate. In a Control System, Disturbance is what you make the control system for in the first place, it can be anything that alters the functionality of whatever you are working with.

If it's a car, you could say that a disturbance is an obstacle in the road, or if it's a washing machine, it could be a weight overload. Noise here refers to electrical noise, it's an alteration in the output which in that particular control system that your image shows, is mitigated with a feedback loop.

Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. What is difference between noise and disturbance in control system? Ask Question. Asked 4 years, 8 months ago. Active 4 years, 5 months ago.

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