## 4 Multi-Level Evaluation Model Based on Cloud Theory
### Cloud Theory Evaluation Model of EPS Performance  
(1) Constructing a comment set cloud model  
A comment set cloud model is established to quantitatively transform and analyze the working state of the EPS, so a positive cloud generator is adopted. Firstly, by consulting expert opinions, the evaluation interval is divided and based on Equation (13), three characteristic numerical expectations, namely \(Ex^{V}\), \(En^{V}\), and \(He^{V}\), of the EPS working performance comment set are determined [19]. \[\left\{ \begin{array}{l}Ex_{i}^{V}=\frac{(x_{i}^{\max}+x_{i}^{\min})}{2}\\ En_{i}^{V}=\sqrt{\frac{\left(x_{i}^{\max}-x_{i}^{\min}\right)^{2}}{8\ln 2}}\\ H_{e}^{V}=k\end{array} \right. \tag{13}\]  
where \(x_{i}^{\max}\) and \(x_{i}^{\min}\) represent the upper and lower boundary values of EPS performance in the comment set, respectively; the performance of the working state is commonly used to determine the classification. \(Ex_{i}^{V}\) is the expectation of the comment set corresponding to the security level in the normal cloud model. \(En_{i}^{V}\) is the entropy of the comment set corresponding to the security level in the normal cloud model. \(k\) is a constant that is often determined by an empirical value. (2) Build an indicator cloud model  
Based on the scoring results provided by experts regarding the actual situation of the project, the influence weights of various factors in the multi-level system are obtained via  
Figure 3: Cloud generator. (**a**) Forward cloud generator; (**b**) Reverse cloud generator. the improved combinatorial weighting method of the AHP-entropy weight method. Then, the cloud parameters of each index are obtained by using the inverse cloud generator, and the specific calculation method is shown in Equation (14). \[\left\{ \begin{array}{l}Ex_{j}=\frac{1}{n}\times\sum\limits_{i=1}^{n}x_{ij}\\ En_{j}=\sqrt{\frac{\pi}{2}}\times\frac{1}{n}\times\sum\limits_{i=1}^{n}\left|x_ {ij}-Ex_{j}\right|\\ He_{j}=\sqrt{\frac{1}{n-1}}\times\sum\limits_{i=1}^{n}\left(x_{ij}-\overline{x }\right)^{2}-En_{j}^{2}\end{array} \right. \tag{14}\]  
(3) Building comprehensive cloud parameters of the system  
Based on the above-weighted processing index cloud parameters, the cloud parameters of the entire EPS working state are summarized [20], and the specific calculation method is shown in Equation (15). \[\left\{ \begin{array}{l}Ex=\sum\limits_{i=1}^{n}Ex_{j}W_{j}\\ En=\sqrt{\sum\limits_{j=1}^{n}\frac{W_{j}^{2}}{\sum\limits_{i=1}^{n}W_{j}^{2}} En_{j}}\\ He_{j}=\sqrt{\sum\limits_{i=1}^{n}\frac{W_{j}^{2}}{\sum\limits_{i=1}^{n}W_{j}^{2}} He_{j}}\end{array} \right. \tag{15}\]  
(4) Drawing and comparing cloud pictures. According to the above formula, the membership cloud model \(U\) (\(Ex^{V}\), \(En^{V}\), \(He^{V}\)) representing the working state of the EPS is calculated and sorted out. Then, using MATLAB R2023a software, a cloud map of the comment set and a cloud map of the evaluation of the EPS working state are drawn. Finally, the membership degree of the EPS working state is determined according to the maximum membership principle and comprehensive evaluation method. Here, the selection of the maximum membership principle is mainly based on the meaning of cloud parameters (\(Ex\), \(En\), \(He\)). Once the cloud parameters of the working performance of the target factor EPS are determined, they can be determined according to the values and meanings of \(Ex\), \(En\), and \(He\). That is, \(Ex\) represents the central location of the cloud droplet and the central value of the membership degree of the target factor. \(En\) represents the difference in expert scores. The smaller the difference, the more concentrated the score data, and the smaller the value of \(En\). \(He\) is used to describe the condensation of cloud droplets, reflecting the deviation between the factor value and the central value. Therefore, if most of the cloud droplets reflecting the working performance of the EPS are distributed in a certain interval, the working level of the EPS system can be directly determined.