Damping

It is a characteristic of vibrations that the amplitude gradually decreases with time. However, although simple vibrations are movements that in theory would keep moving forever, when experiments are actually carried out, they are restricted by air resistance and frictional force, which gradually stops them. Such actions are referred to as damping, or damped oscillation.

Dynamic damping is an important technique in controlling the speed and position of a motor. For example (in the upper graph), when starting and accelerating a stationary motor and bringing it to a constant speed, undesirable oscillations are generated naturally. The lower graph shows a situation where the oscillations can be suppressed by a method called differential compensation.