The system shown in Figure 3 is that of a closed loop, with sensors feeding the control system that drive changes in the environment.

图3所示的系统是一个封闭循环，传感器负责为控制系统提供数据，而控制系统则驱动着环境中因素的变化。

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A kind of the pulse control mode, the drive and motor closed loop, but not to the numerical control system, the feedback device, in a sense, can open loop control called the servo control.

一种采用脉冲控制方式，此种驱动器与电机闭环，但不反馈到数控系统，这种驱动器在某种程度上可称为开环控制的伺服控制。

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Adopting ac servo motor as a drive device, can and dc servo motor as a high precision, high performance and a half closed loop or closed loop control system.

采用交流伺服电机作为驱动器件，可以和直流伺服电机一样构成高精度，高性能的半闭环或闭环控制系统。

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