Feedback Systems
Feedback Systems
Feedback involves the system using information about its output to make adjustments. For example, a car’s cruise control system constantly monitors the car’s speed and adjusts the throttle to maintain the desired speed.
In Systems Engineering, we use forms of feedback to show that a process is complete, a speed has been reached, a limit is met, or any other parameter has been measured.
We can use transducers and other sensors and logic to monitor the system, and make it respond appropriately. There is no exhaustive list as to how we can implement feedback into our projects, as it all depends on your system as to how it knows what it is doing, and responding appropriately.
You could use a microswitch to tell if a door was completely shut.
You could use an ultrasonic sensor to check if an object was in the way or in the correct position.
You could use an ammeter to determine if a DC motor is under load or has stalled.
You could use a potentiometer or rotary encoder to measure position or angle of a moving part.
You could use a limit switch to detect when a mechanism has reached its maximum or minimum travel.
You could use a light sensor (LDR or photodiode) to detect changes in ambient light or confirm a visual indicator is on.
You could use a temperature sensor to detect overheating or confirm a system is operating within safe limits.
Negative Feedback
Negative feedback reduces change in the system. Most of the time we use negative feedback as the feedback loops in our systems to slow or stop a system. Essentially, if the system deviates from set parameters, the system counteracts the deviation.
Positive Feedback
Positive feedback is the opposite, and accelerates or amplifies change. We generally do not use positive feedback in systems. Unchecked positive feedback can have avalanche effects, or create systems that get out of control.
You can think of the different types of feedback as:
Positive: The system runs if a condition is met, then keeps running.
Negative: The system runs unless a condition is met, then it slows or stops.