Motion Control

Central to the task of controlling motion is the concept of negative feedback. As an example of negative feedback, consider what happens when you are hungry. Hopefully, you will be able to get something to eat. As you eat, you become less and less hungry until you eventually stop eating. This is the idea of negative feedback. Imagine if the opposite were true and eating made you hungrier.

Negative feedback in a motion control system proceeds in a similar fashion. There is a desired position for the motor and a feedback sensor that tells the motor it is not at the correct position. In effect, it is "hungry" to get to that position and begins turning towards it. As the motor gets closer to the desired position, the feedback device tells the motor that it is becoming "less hungry" and the motor responds by turning more slowly. In a perfect control system, the motor will get to exactly the right position and then will turn no more until it is commanded to a new desired position.