Feedback and Control Systems

A feedback and control system is a mechanism that uses a combination of sensing, computation, and actuation.

A sensor is something that measures or detects something. It can measure a digital or analog signal and acts as an input for the mechanism. Computation takes data from the sensor and does something with it. Actuators are things that move (mechanically or electrically), like a piston or a light going on.

For this assignment, we were tasked with identifying and analyzing four feedback and control systems. They are described below.

System #1:

The first feedback and control system I analyzed was the swipe locks on the outside of all of the college buildings. They look like this:

When you swipe your one-card, the door will either unlock or not, depending on your specific access. The sensor of this mechanism receives a signal by reading the magnetic strip on the one card. This is likely a digital signal because it will either open the lock or not. Certain people's one cards will either be coded with access or not for a specific door lock.

The computation piece of this feedback and control system will take the reading from the magnetic strip and either unlock the door or leave the door locked.

The actuators of this system is the lock itself. When the system receives the digital signal for unlock, the lock will open and the green led light will turn on. If the system receives the digital signal for don't unlock, the red led will turn on and the lock will not be opened. When the system receives no signal, the yellow led light will show.

System #2:

The second feedback and control system I analyzed was the water dispenser. These water dispensers are all over the sports center and in the science center. They look like this:

The sensor for this system is a digital sensor. The sensor is either on or off- there is either something in front of sensor and it is turned on, or it is off if there isn't anything in front of the sensor.

The computation part of this system tells the water to turn on when there is an object in front of the sensor or to keep it turned off.

The actuator part of this system turns the water on when it gets the signal for "on"or it leaves the water off when the signal is "off".

System #3:

The third feedback and control system I analyzed was the fire alarm and sprinkler. These are in all of the dorm rooms and they look like this:

The sensor on this system is an analog sensor because it takes readings on the air in a room. It measures the amount of smoke in the room and once it measures a certain amount of smoke the actuator will activate.

The computation part of this system is the system that determines if the sensor is detecting high amounts of smoke or not, and then telling the sprinkler to turn on or stay off.

The actuator part of this system is the sprinkler turning on or off depending on the signal that the sensor is getting.

System #4:

The fourth feedback and control system I analyzed was the motion sensing lights in the observatory. When the lights are on in the "project room," a specific room in the observatory, the lights will turn off automatically after a specific time if no motion is detected. They will also turn back on if they detect motion.

The sensors for this system are quite obviously the motion sensors. These are digital signals-- either they detect motion or they do not. These motion sensors, in this room particularly, are located in the front by the door and in the back.

The computation part of this system is what the system does with the signal. If it detects motion, it tells the lights to turn on, if it doesn't sense motion for a while, it tells the lights to turn off.

The actuator part of this system are the lights turning on or turning off. Depending on the signal and the computation piece, the lights will turn on or turn off.