New York State Standards
MST 5.4  Key Idea

Technological systems are designed
to achieve specific results and produce outputs,
such as products, structures, services, energy or other systems.

Systems are a means of getting things done.

System Components

Input is the command we give a system, what we expect out of the system.
    Resource inputs are the resources that we need to operate the system.

Process is the action part of the system, this is where the work gets done.

Output is the actual result, what comes out of the system.  If the system is working correctly the output matches the input.

Kinds of Output

Monitor is to watch the system.

The comparator compares the output with the input.

To adjust means to make changes to the system.

Feedback is the information we get from a system.

The feedback loop includes monitor, comparator, adjust and feedback.  In the feedback loop, you look (monitor) at the information (feedback) that you are getting from a system, you compare the output with the input and make adjustments.

System Types

Open loop systems have just input, process and output.
Example: A math test.    The input is get 100 on a test!
                                    The process is using all your resources to put answers on the paper.
                                    The output is the grade that you get.  

Closed loop systems have input, process, output, monitor, feedback, compare and adjust.
Example: A math test.    The input is get 100 on a test!
                                    The process is using all your resources to put answers on the paper.
                                    The output is the grade that you get.
You have a really nice Math teacher who uses the feedback loop to determine the final grade!                     
                                    You look (monitor) at your grade on the test paper.
                                    The feedback is unacceptable.
                                    You compare the work to your notes and find your mistakes.
                                    You adjust (make corrections to) your work.
                                    You hand in the test and the output is an improved grade!
A super nice teacher might let you repeat the loop again and again until you got the 100.

A subsystem is a smaller system operating as part of a much larger system.

 

Systems Diagrams are a way of drawing how a system works.  There are many versions of  systems diagrams.  Below is one method of drawing an open loop and a closed loop system.

An Open Loop Systems Diagram

A Closed Loop Systems Diagram

 

Our Favorite Toys is a unit on control systems.  http://www.thirteen.org/edonline/lessons/toys/
It's designed as an internet activity for grades 9-12.