## 3 Fault Classification for CPSs  
The authors found that engineers have analyzed and summarized the fault manifestations and troubleshooting methods of different types of CPSs used in different projects and different industries [32; 33; 34; 35; 36], which has a certain reference significance for similar system troubleshooting. However, there are many types of faults in CPSs, and there are no clear classification standards. This section discusses the division of the main faults of a CPS into the four categories of material conveying system faults, batch metering system faults, pneumatic system faults, and mixer faults, depending on the fault location. According to the specific manifestation of various faults, the mechanical structure characteristics and operational characteristics are comprehensively considered and the CPS faults are further subdivided into 22 sub-categories. The detailed classification is shown in Table 1.  
Class A: Material handling system faults  
The transportation of materials in the CPS mainly includes the transportation of aggregates and powders. In the construction of concrete dams, belt conveyors are often used for the transportation of aggregates. The transportation of cement and admixtures is often carried out with screw conveyors and pneumatic conveying. The basic structure of the material conveying system is shown in Figure 2. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Fault Category** & **Category Number** & **Fault Manifestation** & **Corresponding Number** \\ \hline \multirow{6}{*}{Material handling system fault} & \multirow{6}{*}{A} & Belt conveyor bearing damage & A1 \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \hline \multirow{6}{*}{Batch metering system fault} & \multirow{6}{*}{B} & \multirow{6}{*}{C} & \multicolumn{1}{c}{} \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \hline \multirow{6}{*}{Pneumatic system fault} & \multirow{6}{*}{C} & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \hline \multirow{6}{*}{Stirring system fault} & \multirow{6}{*}{D} & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \cline{3-3}  & & \multicolumn{1}{c}{} & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Main fault classification of CPS. Class B: Batch metering system faults  
The metering system includes aggregate metering and powder (cement and admixture) metering, as well as water and liquid admixture metering. The metering system is one of the most critical parts of the CPS. The batching electronic scale is the main component of the concrete batching metering system. The electronic scale of each ingredient is composed of a batching bin (body), load cell, junction box, digital weighing instrument, and connecting line. In the aggregate metering system, after the aggregate is transported into position, the material is distributed by the motor vibrating feeder, and the arc door feeder is installed in the lower part of each aggregate silo. The arc gate controls the cylinder through a micro-computer system to complete the opening and closing of the aggregate silo to complete the precise dosing task.