# MOIRA-UNIMORE Bearing Data Set for Independent Cart Systems
## 5 Experimental Data Acquisition
### Bearing Defects  
Bearing defects can be classified into four categories: inner race fault of the top bearing (IR-Top), outer race fault of the top bearing (OR-Top), inner race fault of the bottom bearing (IR-Bottom), and outer race fault of the bottom bearing (OR-Bottom). Each of these fault categories is further divided into specific fault severities. For example, IR-Top faults include severities with widths of 0.25 mm, 0.5 mm, 1.0 mm, and 1.5 mm, while OR-Top faults have severities of 0.25 mm, 0.5 mm, and 2.0 mm. Similarly, IR-Bottom faults have severities of 0.25 mm, 0.5 mm, and 1.0 mm, and OR-Bottom faults include severities of 0.25 mm, 0.5 mm, and 1.0 mm. It is important to note that the IR-Top and IR-Bottom fault categories are further classified based on the orientation of the fault with respect to the radial axis. For IR-Top, the fault orientations are categorized as 0\({}^{\circ}\), 180\({}^{\circ}\), and 270\({}^{\circ}\). Similarly, for the IR-Bottom, the orientations are classified as 0\({}^{\circ}\), 90\({}^{\circ}\), and 270\({}^{\circ}\). The fault signature analysis indicates that for IR-Top, the 270\({}^{\circ}\) orientation exhibits the strongest vibration signature, highlighting that this section of the inner race is subjected to greater stress and is therefore more prone to damage and wear. Likewise, for the IR-Bottom, the fault signature is strongest in the 90\({}^{\circ}\) orientation, indicating that this region experiences the highest stress levels and is the most vulnerable to damage. These observations emphasize the importance of fault orientation in determining the stress distribution and potential failure points within bearings. The difference in fault behavior between the top IR and bottom IR based on the fault orientation is probably influenced by the spring-like preload mechanism incorporated into the cart design. This mechanism applies radial forces that pull the top bearings downward and push the bottom bearings upward against the V-shaped edges of the guide rail upon which the bearings glide. This force distribution ensures a stable connection between the bearings and the rail but also creates varying stress concentrations at different orientations. As a result, the top bearing experiences increases stress at the 270\({}^{\circ}\) position, while the bottom bearing is more stressed at the 90\({}^{\circ}\) position. Understanding these dynamics is crucial for accurately diagnosing and predicting faults based on the vibration signatures associated with these orientations. Note that fault orientation is not applicable for the outer race (OR) faults of the top and bottom bearings. This is because the outer race rotates according to the operational speed profile and cannot be fixed in a stationary position. It is important to note that the data set contains folder names with IR fault orientation labels such as 3-O'Clock, 6-O'Clock, 9-O'Clock, and 12-O'Clock. Here, 3-O'Clock denotes the 0\({}^{\circ}\) orientation, 12-O'Clock denotes 90\({}^{\circ}\), 9-O'Clock represents 180\({}^{\circ}\), and 6-O'Clock denotes 270\({}^{\circ}\). In the case of three-cart experiments, the middle cart, referred to as Mover M2, is always designated as the faulty one. Regardless of the type of experiment, whether in single-cart or three-cart configurations, only one of the three bearings on the faulty cart contains a defect at a time, which can be either an inner race (IR) or an outer race (OR) fault. A generalized overview of the experimental configuration, including fault types, sizes, fault orientations, and speed profiles, is presented in Figures 8 and 9. Table 5 provides a comprehensive overview of the experimental configurations, detailing the fault types, sizes, orientations, and corresponding speed profiles across various experiment classes. Thistable also highlights the experiment types conducted under different conditions, facilitating a clear understanding of the data set structure and experimental conditions.