# A Novel Integrated Fault Diagnosis Method Based on Digital Twins
## 3 Proposed Methodology: DCBA Fault Diagnosis
### Digital Twin Model  
We provide a detailed description of the digital twin model used in this study. The model follows a hierarchical structure of \"component-module-subsystem\", which ensures clarity and independence at each level, enabling the coordinated operation and dynamic response of the entire system.  
The component layer serves as the fundamental unit for constructing the digital twin. It includes various independent physical elements such as components, actuators, and sensors. At the module layer, components are integrated based on mechanical and circuit principles to form modular components with specific functions. The subsystem layer further integrates modules to form more complex mechanical subsystems. These subsystems implement specific mechanical operational logic and numerical transmission. Finally, the integration layer integrates different subsystems to facilitate data interaction between systems, forming a comprehensive high-fidelity digital twin model. This hierarchical model comprehensively simulates and analyzes the performance and behavior of the spiral compressor. With this high-fidelity digital twin model, it is possible to understand in detail the operational states and efficiencies of the spiral compressor under various operating conditions, identify potential issues, and optimize performance adjustments.  
Figure 1: The framework of the integrated fault diagnosis method for electric screw press machines.  
Based on a detailed analysis of the components of the spiral compressor system, this paper simplifies the spiral compressor system into four key subsystems: mechanical system, hydraulic system, electrical system, and measurement and control system.  
1. Mechanical system: The mechanical subsystem is directly related to the motion of the compressor and is primarily responsible for compressing and shaping the workpiece. It includes various transmission mechanisms, guiding structures, and mechanical components to ensure the precise movement and force transmission of the compressor.
2. Hydraulic system: The hydraulic subsystem maintains the balance of the compressor, ensuring stability and controllability during operation. It consists of hydraulic cylinders, valves, pumps, and other hydraulic components that control hydraulic pressure and flow to stabilize and regulate the movement of the compressor during impacting processes.
3. Electrical system: The electrical subsystem involves the circuits and electronic controls of the compressor, enabling electrical signal control and impacting actions. It includes motors, sensors, controllers, and electrical circuits which ensure that mechanical components operate according to predefined logic and sequence.
4. Measurement and control system: The measurement and control subsystem is responsible for parameter measurement and logic control. Its main function is to detect the status of other subsystems, provide timely feedback on monitored status information, and make corresponding decisions and controls. It includes various sensors, data acquisition devices, and control algorithms to ensure the efficient operation and real-time monitoring of the entire compressor system.  
The specific structure of the digital twin model is illustrated in Figure 2, showing the relationships between these subsystems. This structured model enables the comprehensive simulation and analysis of the operational state of the spiral compressor, facilitating optimization of its performance and efficiency.