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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
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