Digital servo controller

Digital servo controllers are devices (usually computer based) that provide motion control by processing digital signals. Typically a controller has inputs connected to sensors on the device they control, which measure the feedback, its current state (for example the current position), and process this signal to provide a output to a hydraulical, electrical or other type of servo control of the controlled device, with the aim of matching a control signal.

A good example is an elevator. The control signal is the button selects the floor the passenger wants to go. The controller of the elevator looks at which floor the elevator currently is (current position), at the floor selected (by the button) and by comparing them to each other derives a signal to control a servo (either hydraulic or electric) that makes the elevator move until the right floor is reached.

In the older days servo controllers where usually analog, but with the rapid developments in digital signal processing and computer technology, servo controllers are almost exclusively digital devices. This offers many advantages, because it allows the user to execute all kind of additional operations on the digital signals, in addition to the standard PID controller.