1. Also known as closed-loop feedback closed-loop control system. The system the system output of the given value of measured value and what to expect, resulting in a deviation signal and reuse signal deviation control, enables the output value to close to the expected value. Wuxi god rushed, for example, while driving, the first person in the brain of the car driving direction have a preliminary perception, in the process of driving the car, the man in the car driving direction with eyes to observe and compare the car driving direction and the direction of the desired, in the process, constantly adjust the direction, finally make the car driving direction constantly close to the target direction, forming a closed loop control. Closed-loop control is based on the machine tool operation and running, the parts with high precision and response speed. Because of the closed loop control system design elements is more, compared with open loop system, the system structure is more complex, the price is also higher. 2. Open loop open loop is compared with the closed loop, namely the open-loop control is out of the feedback current system control results. For example, throwing things. Things once was thrown out, people can't to control the thrown things. Once because of things left hand, and a man of things control will stop immediately.