In general, it refers to imitating the shape of a physical object or structure in a design, and its size can be divided into miniaturization, physical type, and enlargement. Some models even have identical details to the actual object, while others imitate the main features of the object. The significance of a model lies in understanding the image of an object visually. In addition to its artistic appreciation value, it also plays a significant role in education, scientific research, industrial construction, civil engineering, and military affairs. With the progress of science and technology, people view the research object as a system and conduct research from the perspective of overall behavior. Systematic research is not about listing all facts and details, but identifying factors and interrelationships that have significant impacts in order to grasp essential laws. Establish through analogies, abstractions, and other methods. This is called modeling. The model can take various forms without a unified classification principle. It can be divided into physical models, mathematical models, and structural models.

物理模型：又稱實體模型，又可分為實物模型和類比模型。①物理模型：根據(jù)相似性理論制造的實物，如飛機模型、水力系統(tǒng)實驗模型、建筑模型、船舶模型等。②類比模型：在不同的物理領域(機械、電學、熱學、流體力學等)。)，每個系統(tǒng)的變量有時遵循相同的規(guī)律。根據(jù)這個共同的規(guī)律，可以制作出具有完全不同物理意義的比較和類推模型。例如，在一定條件下，由節(jié)流閥和氣容組成的氣動系統(tǒng)的壓力響應與由電阻和電容組成的電路的輸出電壓特性有相似的規(guī)律，因此可以使用更容易實驗的電路來模擬氣動系統(tǒng)。

Physical model: also known as physical model, it can be divided into physical model and analog model Physical model: physical objects manufactured according to similarity theory, such as Model aircraft, hydraulic system experimental model, building model, ship model, etc Analogy model: in different physical fields (mechanics, electricity, heat, Fluid mechanics, etc.), The variables of each system sometimes follow the same pattern. Based on this common law, comparative and analogical models with completely different physical meanings can be created. For example, under certain conditions, the pressure response of a pneumatic system composed of a throttle valve and a gas capacity has a similar pattern to the output voltage characteristics of a circuit composed of resistors and capacitors. Therefore, a circuit that is easier to experiment with can be used to simulate the pneumatic system.

數(shù)學模型：一種用數(shù)學語言描述的模型。數(shù)學模型可以是一組或一組代數(shù)方程、微分方程、差分方程、積分方程或統(tǒng)計方程，也可以是它們的適當組合，通過這些方程定量或定性地描述系統(tǒng)變量之間的關系或因果關系。除了用方程描述的數(shù)學模型外，還有用代數(shù)、幾何、拓撲、數(shù)理邏輯等其他數(shù)學工具描述的模型。需要指出的是，數(shù)學模型描述的是系統(tǒng)的行為和特征，而不是系統(tǒng)的實際結構。

Mathematical model: A model described in mathematical language. Mathematical models can be a group or a group of Algebraic equation, differential equations, difference equations, Integral equation or statistical equations, or an appropriate combination of them. These equations can quantitatively or qualitatively describe the relationship or causal relationship between system variables. In addition to mathematical models described by equations, there are models described by algebra, geometry, topology, Mathematical logic and other mathematical tools. It should be pointed out that the mathematical model describes the behavior and characteristics of the system, rather than the actual structure of the system.

結構模型：主要反映系統(tǒng)結構特征和因果關系的模型。結構模型中的一個重要模型是圖形模型。此外，生物系統(tǒng)分析中常用的房間模型也屬于結構模型。結構模型是研究復雜系統(tǒng)的有效手段。

Structural model: A model that primarily reflects the structural characteristics and causal relationships of a system. An important model in structural models is the graphical model. In addition, room models commonly used in Biological system analysis are also structural models. Structural models are an effective means of studying complex systems.