General steps for building component and system mathematical models
In order to quantitatively describe the functional relationship between the input and output of the system, it is necessary to list the differential equations of the system. The general steps for establishing a system differential equation are given below.
(1) Determine the input and output signals of the system. On this basis, the system is divided into several links (or components), and the input and output signals of each link are determined, and the output of the previous link is taken as the input of the latter link.
(2) According to the physical and chemical laws followed by the link (or component), the differential equations of each link are listed. In order to contact the relevant variables in the various links in the system, it is often necessary to introduce intermediate variables.
(3) Eliminate the intermediate variables and obtain the same-order differential equations with the system input output as the variable.
note. After simplification, the established differential equations only contain the input and output signals of the system (not the link). This gives the mathematical model of the component or system to be built.