The controller in the automatic control system plays an important role in the entire system, playing the role of system management and organizational core. The advantages and disadvantages of system performance depends largely on the quality of the controller. We can recognize the role of the controller by comparing the working principle of the artificial control system and the automatic control system. First we introduce the manual control system, Figure 1 is a structural diagram of the manual control system of the thermostat. The temperature in the incubator is required to remain constant. In order to measure the temperature in the incubator, install a thermometer to indicate the temperature in the incubator, this temperature is the output of the system, or is controlled. The operator always observes the temperature of the thermometer, when less than the constant temperature box is given, increase the current of the heating device; the current is reduced when it is greater than the constant temperature box is given. This allows the thermostat to maintain a given temperature. People have the following roles in this system: 1. Observe the temperature in the thermostat. 2. Compare the difference between temperature and given temperature in the incubator. 3. Adjust the size of the heating current. Figure 1 Configuring the artificial control system diagram understands the principle of manual control system, we can turn it into an automatic control system as long as we use some devices to imitate and replace people's intelligence. First, the thermometer is used to measure the temperature of the temperature, and then use the comparative amplifying circuit instead of the comparison of the temperature, replace the human hand with the motor to rotate the current adjustment device of the incubator. As long as the polarity of the amplification circuit and the direction of rotation of the motor are reasonably selected, the automatic control of the temperature of the thermostat temperature can be completed. The structural diagram of the automatic control system is shown in Figure 2. Figure 3 Control System General Structure Diagram From Figure 3, it can be seen that the controller actually replaces the human brain in the manual control system, which determines the control signal based on the input signal and the feedback signal. When the design of the control system, the controlled object is often unable to be changed. To meet the performance requirements, the key is to see how the controller is designed. A good controller can make the system work well, and the system cannot meet the requirements. This is not as good as a smart person who is more stupid. The controller has various forms, according to the nature of the signal, can be divided into two types of analog controllers and digital controllers. The former signal is mainly analog form; the latter mainly uses digital forms, and there are D / A and A / D converters in the input and output. The structure of the controller is complicated and relatively simple. The comparative amplification circuit in the above thermostat control is a relatively simple controller. The controller of complex systems is often complicated, and some controllers are even a computer.
