## 2 Data Collection and Preprocessing
### Data Collection
The maximum measurements sampling frequency was 50 Hz, due to the limitations of the measurement system in terms of data transmission capabilities, but this value is similar to those used in the literature. In addition, based on an analysis of the cabin door control software, 11 of the diagnostic quantities available in the module were selected, which could have a significant impact on the ability to identify faults. In the normal operation of a passenger elevator, data from individual modules (such as the main module, cabin door controller, and cabin and floor modules) are transmitted via an internal CAN bus, the speed of which is 125 kbps due to length limitations (the bus connects multiple modules located throughout the whole elevator shaft). The elevator's internal bus is the place where all information on the functioning of the elevator and its  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Type of Fault** & **Severity** & **Description** & **Percentage** & **Chart** \\ \hline  & \begin{tabular}{c} High \\ Damage to any transistor in \\ the drive controller results in \\ operation without one of the \\ motor phases, causing \\ significant torque oscillations. \\ lower branch of \\ the control bridge \\ (dt) \\ \end{tabular}  & 49,519 & 1.26\% & 1.26\% \\  & \begin{tabular}{c} Higher \\ motor cannot generate \\ sufficient torque to overcome \\ the mechanism’s resistance. \\ Consequently, the doors will \\ not lock despite being closed. \\ \end{tabular}  & 49,519 & 1.26\% & 1.26\% \\  & \begin{tabular}{c} Higher \\ As above \\ \end{tabular}  & 54,311 & 1.38\% & 1.26\% \\  & \ \begin{tabular}{c} Higher \\ As above \\ \end{tabular}  & 54,311 & 1.26\% & 1.26\% \\  & \begin{tabular}{c} Higher \\ As above \\ \end{tabular}  & 54,311 & 1.  
most important components is exchanged, so its operation must not be disturbed by an excessive amount of transmitted diagnostic data, as this could lead to delays or errors in the transmission of data crucial to the proper operation of the entire system. Transmission of the selected diagnostic data via the internal elevator bus would require transmission of 32 kb per second (11 4-byte variables plus overhead due to the CAN frame structure, every 20 ms), which is more than 25% of the throughput of the internal CAN bus. Obviously, such a high load on the bus by only one function of a single module is unacceptable and could overload the transmission. The collection of the device's operational data at high frequency leads to the need for frequent uploads and the collection of significant amounts of information on the main server, which contains a constantly updated fault database. Taking into account the above values, it can be determined that transferring data from such an elevator to the central server would require about 10 GB of transfer per month over the GPRS network for just one device. In addition to the required transfer, it would be necessary to provide adequate disk space necessary for data storage. For one elevator, this would be about 124 GB per year, which, with an estimated production of 700 units, results in about 87 TB of memory to be filled. Given the ever-increasing number of devices being produced, the number of resources needed to store this data would be enormous and very expensive. Therefore, there is a need to reduce the amount of diagnostic data sent via the elevator bus and stored on a central server. This task became the basis for the study of methods for preprocessing information from the cabin door drive system of an elevator.