伺服的基本概念是准确、精确、快速定位。变频是伺服控制的一个必须的内部环节，伺服驱动器中同样存在变频（要进行无级调速）-The basic concept of the servo is accurate, precise and rapid positioning. A servo-controlled inverter is necessary internal links, there are also servo drive frequency (to variable speed)