Equivalent discrete system mathematical model, and then analyze the whole closed-loop system in the category of discrete system. In the traditional analog control system, the control law or function of the controller is completed by the hardware circuit of the instrument or electronic device, while in the computer control system, besides the computer device, it is mainly embodied in the software algorithm, that is, the design of the digital controller.

Discretization method is the basic means to solve the problem of continuous mechanics. It is used to solve the mechanical problems of continuous media by computer. The laws of continuum mechanics are generally described by differential equations or integral equations, and the discretization method turns them into algebraic equations with finite parameters to approximate the original problem. The usual finite difference method, finite element method and weighted residual method are all effective discretization methods.