DC motors are inherently an open feedback system—you give them juice, and they spin. How much they spin is not always known, at least not without additional mechanical and electronic parts.
Servo motors, on the other hand, are a closed feedback system. This means the output of the motor is coupled to a control circuit. As the motor turns, the control circuit monitors the position. The circuit won’t stop the motor until the motor reaches its proper point. All without your having to do anything extra.
Servo motors have earned an important place in robotics. And fortunately for robot builders, another hobby—model radio control—has made these motors plentiful, easy to use, and quite inexpensive.
In this chapter you will ...