# Fault Detection in Active Magnetic Bearings Using Digital Twin Technology
## 5 Modeling of Digital Twin for AMB  
The position signals, control signals, and current signals from sensors, controllers, and actuators, respectively, are used in this paper. Figure 6 shows the description of available electrical signals. Based on the AMB working states, the physical and virtual models have been established. The physical entity's state's position, control, and current data are collected in the physical model to update the digital twin model and combined with the sensors, controllers, and actuators to synchronize with the virtual model. The sensor, controller, and actuator failures will be predicted using the synchronization data, preventing the AMB system from fault using the digital twin. The efficiency of the suggested digital twin model is validated by simulation and experimentation utilizing an AMB system. Figure 7 shows the experimental setup. In order to achieve stable levitation with four degrees of freedom (4-DOF), a pair of radial magnetic bearings are positioned at either end of the rotor. The rotor is mechanically linked to a 1.2-kilowatt motor through a flexible connection. The AMB control system utilizes a digital control modeled on the quick-control prototype dSPACE DS1007. To monitor the position of the rotor in the x and y axes, four eddy current position sensors are fixed adjacent to two radial bearings. The amplifier supports the AMB at 50 v, while the switching frequency is set at 20 kHz. The Tektronix A622 current probe is used to acquire the coil current signal. The AMB configuration utilized in the simulation and experiments' physical and control parameters are shown in Table 2.  
Figure 6: AMB fault types in the sensors and actuators. Figure 7: Experimental setup. The Matlab-Simulink software(V.R2022b) was implemented to represent the virtual model. The mathematical model was built to accurately represent the magnetic bearing system, including the essential equations and parameters. The selection of MATLAB as the simulation platform was based on its flexibility and comprehensive range of tools for numerical calculations and system modeling. As stated in Section 2.2, a mathematical model based on electromagnetic force theory and control theory was used to represent the active magnetic bearing system. The model was designed to include pertinent variables, such as position, control, and current signals, to effectively describe the system's dynamic behavior. The parameters listed in Table 2 were used to configure the MATLAB simulation. The data used in the MATLAB simulation was obtained from the actual active magnetic bearing system being investigated. The system's installed sensors' position, control, and current signals were captured immediately throughout the data-collecting procedure. The raw data obtained from the physical system may potentially include many sources of noise and artifacts. In order to tackle this issue, signal processing methodologies were used, including the implementation of filtering methods and algorithms for noise reduction. The purpose of these preprocessing operations was to enhance the quality and reliability of the input signals, hence improving the accuracy of the MATLAB simulation outputs. The MATLAB simulation was enhanced by using actual input data obtained from the physical system, resulting in a more precise simulation of the behavior of the active magnetic bearing. This methodology facilitated the evaluation of the digital twin's ability to identify failures in a manner that closely corresponds to the actual operating circumstances in the real system. The data collection process included the identification of various sensors used in the physical system, such as position sensors, control signal sensors, and current sensors. The suitable dSPACE (DS1007) hardware platform was chosen for integrating sensors with the simulation model as show in Figure 5. The hardware was set up for sensor signal collecting using dSPACE software tools, namely ControlDesk (V. 7.6.1.1).