Ineco is an engineering company with extensive experience in the transportation sector. To study the influence of harmonics on the railway infrastructure, we designed and developed a data acquisition system that integrates all the required characteristics.
Teams usually collect railway data on a mobile traction unit. For this project, we chose an NI PXIe-1062Q 8-slot chassis to minimize the effects of vibrations.
Using the PXI platform with the NI 6120 and NI 6123 modules, we captured the various voltage and current signals simultaneously and at high frequency (50 kHz), which gave us the ability to record an entire bandwidth of audio frequencies. To connect the modules, we used NI TB-2708, TB-2709, and TB-2705 terminal blocks to provide the first two SMB connections and the last direct signal cable connection.
We needed to use an MVB communication card to capture different signals on different traction units. The PXI platform and LabVIEW fully integrate inside the chassis and transfer the data between the card and application quickly and easily with the use of DLL-specific LabVIEW VIs.
One of the main requirements for our design was accurate synchronization of multiple computers from a distance and in motion.
To achieve the needed synchronization, we decided to use the NI PXI-6682 timing and synchronization module to synchronize with GPS. This module perfectly suited our system integration because it is modular, is easily incorporated into the application, and more accurately synchronizes equipment.
GPS User Interface
To visualize the point-of-action location within the railway infrastructure, we transferred the GPS position coordinates obtained by the antenna connected to the PXI-6682 to a user interface associated with Google Earth. We connect to Google Earth using 3G, or if there is no coverage, we use a cache of previously stored software maps of the area of study.
We developed our application using LabVIEW because it easily integrates our various hardware modules, has a powerful graphical development environment, and offers a visual programming environment.
The application is designed to operate in two distinct environments: first for data acquisition, monitoring, and real-time processing; and second for data acquisition for a long period of time, fully automatically (without human intervention of any kind), and with the support of an uninterruptible power supply (UPS).
We structured the system in three main blocks.
For the initial setup, our basic parameters were the number of probes used, MVB communication parameters, type and model of train, and various indicators such as communication with the drive unit and state verification.
Voltage, Current, and GPS
This block is responsible for configuring and performing the data acquisition system from different sensors connected to the computer and GPS signal. If the application is operating in real-time mode, this block also performs signal processing tasks such as filters, RMS, impedance, speed calculation, and displaying.
This block is responsible for establishing MVB communication through DLLs developed using ANSI C and LabVIEW call functions. These variables are also responsible for data logging and displaying.
These blocks are synchronized using timed loops. Synchronization with other computers is through the GPS time provided by the NI 6682 module.
For the logging process automation, we send an analog signal to the UPS through the NI-6120 module. This signal is a disconnection command for the UPS so it enters stand-by mode. Then the PXI is shut down safely, preventing data loss.
Management and Data Processing
We needed a solution to quickly manage large amounts of data by applying filters, analyzing the time domain data and frequency, and generating automated scripts. We used NI DIAdem data management software to meet these requirements.
Using the NI PXI platform, we developed a modular, compact, and reliable data acquisition system for a mobile traction unit. We chose LabVIEW as the development environment due to its intuitive visual programming nature, flexibility, and ease of integration and maintenance through the MVB protocol. The DIAdem data management software reduced our processing time and effort by automating reports using scripts.
The synergy between NI hardware and software offers continuous development and improvement so we can easily update the system-based changes that may occur in the railway sector.
Daniel Parra Ramos