Pid is a digital TV controller. PID = port ID. In STP (Spanning Tree Protocol), if the BID in the BPDU received by the port is the same as the path cost, the PID is compared to select the blocked port. The term PID (packet identifier) in digital TV multiplexing system is like the file name of a file, which can be called "identification code transmission packet".

PID (Proportional Integral Differential) in engineering control and mathematical physics is a mathematical physics term. PID is composed of 8-bit port priority plus port number, the port number is low, and the default port number priority is 128.

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Parameter tuning of PID controller is the core content of control system design. According to the characteristics of the controlled process, the proportional coefficient, integral time and differential time of PID controller are determined.

There are many methods for tuning PID controller parameters, which can be summarized into two categories:

The first is the theoretical calculation setting method. It mainly determines the controller parameters through theoretical calculation according to the mathematical model of the system. The calculated data obtained by this method cannot be used directly, and must be adjusted and corrected through engineering practice.

The second is the engineering setting method, which mainly relies on engineering experience and is directly carried out in the test of control system. This method is simple and easy to master, and is widely used in engineering practice. The engineering tuning methods of PID controller parameters mainly include critical proportion method, response curve method and attenuation method.

The two methods have their own characteristics, and the similarities are through experiments, and then the parameters of the controller are adjusted according to the engineering experience formula. But no matter which method is adopted, the parameters of the controller need to be finally adjusted and improved in actual operation.