Air Pollution as a Feedback Control Loop

Andrew McCarthy

IntroductionAir Pollution Feedback ControlPurpose and Components of FeedbackExamples of FeedbackComponents of Air Pollution Feedback

Control

Air Pollution Feedback Control

Air pollution is monitored and managed by a feedback control system

Air Pollution Feedback Control

Economic growth has benefits, but with those benefits come risks, such as those caused by air pollution. As a result, the growth must be controlled.

Purpose of Feedback

The primary reason for feedback control is to measure and compensate for the effect of disturbances.

4 Elements of Feedback

SensorReference Input ComparatorControl Mechanism

www.oz.net/~coilgun/levitation/feedbackloop.htm

Sensor

The sensor measures the variable that we seek to control, also known as the control variable.

Reference Input

This specifies the value the controlled variable should have.

Comparator

Compares the sensed value with the reference value. It also specifies the direction in which the correction needs to be made.

Control Mechanism

Takes the output of the comparator and corrects the sensed value in the direction of the reference input.

Practical Examples

Temperature Control-No 2nd Loop

Thermostat sensor, user inputs, thermostat compares, furnace and AC control

Practical ExamplesPitch Control of an Airplane

Pitch sensor, pilot inputs, computer compares, elevator controls

http://www.engin.umich.edu/group/ctm/examples/examples.html

Air Pollution Context It is possible, in the context of economic

growth, to have two loops, one which works to reinforce growth, and the other which mitigates against further growth.

Air Pollution Context

The second loop is not an intrinsic property of feedback control. It is possible for feedback control to contain only one loop.

How is pollution sensed?Monitoring agencies use EPA approved

equipment. PM and lead are measured over a 24 hour period, whereas gaseous pollutants are measured hourly. Collected data is then compared to the Clean Air Act standards (NAAQS) for each pollutant.

http://www.epa.gov/region08/air/monitoring/monitoring.html

Pollution Reference Value

The EPA creates Clean Air Act standards (NAAQS) for each pollutant.

http://www.epa.gov/region08/air/monitoring/monitoring.html

Pollution Reference Value

NAAQS:

Carbon Monoxide (9 ppm, 8 hour)

PM10 (150ug/cubic meter, 24 hour)

PM2.5 (65ug/cubic meter, 24 hour)

Ozone (.08 ppm, 8 hour)

Sulfur Oxides (.14 ppm, 24 hour)

http://www.epa.gov/air/criteria.html

Air Pollution Comparator

The EPA compares the data collected by monitoring sites to the Clean Air Act Standard.

http://www.epa.gov/region08/air/monitoring/monitoring.html

Air Pollution Control Mechanism

If pollution levels are above the NAAQS and present a risk, the monitoring agency in the state must develop and implement a plan to reduce the air pollution.

http://www.epa.gov/region08/air/monitoring/monitoring.html

ConclusionAir Pollution Feedback ControlPurpose and Components of FeedbackExamples of FeedbackComponents of Air Pollution Feedback

Control

Referenceshttp://www.oz.net/~coilgun/levitation/feedbackloop.htm

http://www.acfr.usyd.edu.au/teaching/3rd-year/mech3800-SystemsControl/material/lectures/block%20diagrams.pdf

http://www.engin.umich.edu/group/ctm/examples/examples.html

http://www.epa.gov/region08/air/monitoring/monitoring.html

http://www.epa.gov/air/criteria.html