# Replacement of Fault Sensor of Cutter Suction Dredger Mud Pump Based on MCNN Transformer
## 3 The Model Framework and Data Preprocessing
### Feature Selection  
As presented in Table 1, CSD generates an extensive array of monitoring datasets. Therefore, feature selection is a critical step before model application. Traditional data-driven techniques like maximum information coefficient (MIC) and F-tests, while effective, are susceptible to the fluctuating and complex operating conditions of CSDs, particularly when dealing with numerous sensor datasets. In response, this study proposes to combine the MPWSS key index selection method with the stacked feature selection algorithm model based on RF and XGBoost. Initially, this paper introduces the MPWSS key index selection method for initial data dimensionality reduction. This approach is based on comprehensive expert experience and prior knowledge of CSD underwater pump mechanics. It establishes a set of standards for the selection of key indices related to shaft seal water pressure. The chosen key indices prioritize real-time responsiveness, functional significance, and high  
Figure 6: Normalization of observation points. data quality. Therefore, based on the construction technology of CSD, the operational principles of the MPWSS, and the most relevant key indicators during CSD construction, the following standards were established:  
1. As shown in Figure 7, the cutting system of a cutter suction dredger comprises a front-end device, a cutter, a cutter shaft, a cutter bearing box, a gearbox, a motor, an underwater pump, and a dredger pipe. This system controls cutter movement, and the mixture of mud and water produced by cutting the soil is collected through the suction inlet and dredger pipe. Therefore, based on expert experience, it can be concluded that cutter speed, cutter bearing flushing pressure, motor indicators (power, voltage, current), and traverse speeds are correlated with mud flow rate and concentration, influencing shaft seal water pressure. In summary, these parameters collectively constitute \"cutter-related indices\" that significantly impact shaft seal water pressure. 2. The mud pump is the core device of the dredger operation. To prevent sediment from entering the pump shaft and causing damage during operation, the seal water pump, as depicted in Figure 1, injects water into the shaft and suction end of the mud pump. Water is injected into the pump shaft seal with specific pressure to ensure that the seal pressure exceeds the pump chamber pressure. Consequently, the seal water entering the mud pump from the pump shaft seal flows along the impeller clearance into the pump chamber, preventing mud from entering the impeller clearance and pump shaft seal. Additionally, a CSD typically includes at least one underwater pump, with larger CSDs featuring 1-2 additional pumps for pressurization. Therefore, the most relevant indices related to the mud pump are those generated by the pump itself. Finally, this study introduces \"pump-related indices\", including suction vacuum, rotation speed, pump power, pump torque, shaft drive power, suction end seal water pressure, 1# pump and 2# pump shaft seal water pressure, and pump discharge pressure. 3. As shown in Figure 8, during the dredging process of the CSD, the cutter cuts through the underwater silt rock layer, and the mud is extracted through the vacuum created by the underwater pump. Subsequently, it is transported to the filling area via the mud suction and discharge pipeline. Due to the considerable length of the pipeline, two additional centrifugal pumps (1# pump and 2# pump) are necessary for pressurization to ensure the transportation of all the mud to the mud outlet. Consequently, certain indicators directly pertain to the mud flow rate and pressure of the underwater pump, while others exhibit indirect relationships, subsequently influencing the water pressure at the shaft end of the underwater pump. As a result, this paper proposes the introduction of \"mud transportation-related indices\", including suction vacuum level, mud flow rate, mud concentration, outlet flow rate, and productivity. Figure 7: Cutter system.