Using LabVIEW, PXI, DAQ, and DIAdem to Build a Sonar Dome Monitoring System

challenge:

Verification of the design and integration of different components inside the sonar dome of the Italian Navy's multi-purpose frigates (FREMM).

Solution:

Develop a sonar dome monitoring system (SDMS) based on LabVIEW and NI PXI data acquisition (DAQ) hardware to collect and process all relevant onboard data, and build a post-processing system based on NI DIAdem.

Figure 1: Sonar dome monitoring system architecture

We need an SDMS that can accomplish the following functions:

· Collect data to analyze the structural and vibration behavior of the sonar fairing, as well as the elastic response of the hydrodynamic components during normal ship operation. The system must be able to provide preliminary real-time details (DIAdem performs further details and cross-correlation analysis with recorded data sets)

Calculate the noise of the platform itself

· Evaluate the propagation of mechanical noise on the shroud and its impact through recorded data and analysis.

A key advantage of the NI software and hardware system architecture is the Technical Data Management Stream (TDMS) file format, which automatically associates raw or processed data with the vessel’s attitude and speed, as well as propulsion attitude, RPM, and propeller pitch, in real time and post-processing.

SDMS Application

SDMS was developed according to the specifications of Orizzonte Sistemi Navali (OSN), the main contractor for the multi-purpose frigate. CETENA built and integrated the entire system, and SITEM developed the LabVIEW application.

The DAQ system is based on the PXI/SCXI platform and includes an NI PXI-8110 controller, an NI PXI-1050 chassis, an NI PXI-6251 multifunction data acquisition module, four NI PXI-4462 IEPE accelerometer DAQ modules, and two NI SCXI-1520 strain gauge input modules.

Even non-professional operators can use SDMS to record all sonar fairing-related structural and acoustic parameters. During ship operation, SDMS can be used to record all sonar fairing-related structural and acoustic parameters, and the integration of the internal components of the fairing can be verified without generating too much data.

SDMS contains two operating modes. In non-assisted mode, SDMS software checks for important incoming signals and detects start/stop recording triggers based on set thresholds. In assisted mode, real-time threshold estimation for triggers is not available. The user can choose whether to manually start or stop a recording and manage the recorded data. The operating mode can be controlled in the operating options in the main window interface.

SDMS manages data acquisition in three main ways. In DAQ analog input data acquisition, the signals output from the DAQ module will be directly acquired, analyzed and stored by the application. In OPC data acquisition, OPC signals are acquired through a TCP/IP connection and Ethernet connection to the Ship Management System (SMS). These signals are related to some ship machinery, such as DGs RPM, propeller pitch, or other equipment status. In UDP data acquisition, signal acquisition can be completed through the Ethernet network of the navigation system.

All recorded data is stored in TDMS file format. Because it is an open architecture, users can choose data analysis software (such as DIAdem) to view the data. TDMS files can contain raw data, OPC, UDP, accelerometer Fast Fourier Transform (FFT) waveforms, and channel calculations (also known as integrated channels). [page]

SDMS Software HMI

The SDMS Human Machine Interface (HMI) provides an easy-to-use graphical interface to manage the acquisition and processing tasks generated by the foreseen needs. The HMI consists of a series of views for a given task and is grouped according to the identity of the function. The operator opens the SDMS project and enters the home page (main interface). From here, it is possible to enter SDMS and use different functions, such as continuous data acquisition, comprehensive calculations, or spectral analysis, data logging, data acquisition, all managed by different software modules.

Figure 2: SDMS HMI main interface

The SDMS HMI has a fixed header at the top of the screen that displays the real-time values ​​of a fixed OPC and UDP signal from the navigation system (NAVS) and the ship's machinery. In the center of the screen are displayed dynamic subpanels called up by the user. The default home subpanel, also called the main interface, allows the user to access other subpanels. SDMS can also calculate some other integrated channels. These channels may include inputs from strain gauges, pressure, hydrophones or accelerometers.

SDMS channel grouping

All channels acquired by the NI acquisition system are grouped together so that when a combined signal of the channels in the group exceeds a threshold, the system can still record the raw data of the channels in the selected group.

Data storage specifications, recording start event

When the vessel speed (UDP signal) exceeds the threshold, the main recording event is detected. When the main trigger event starts, the system stores all OPC, UDP and comprehensive calculation channels. After that, the main recording event is detected and the thresholds of other groups continue to be evaluated. The system also has a pre-trigger buffer feature. The entire recording process stores all data related to the time window before the trigger event is detected. The SDMS software also provides automatic hard disk saturation control tools.

Stop recording, trigger hysteresis

The system will stop all recording processes when the following situations occur:

1. The main speed return value is lower than the threshold. This event will also stop the raw data recording of other groups. When the relevant integrated channel return value is lower than the threshold, the group raw data recording stops.

2. The user presses the stop recording button (main interface sub-panel)

SDMS Processing

SDMS can perform FFT analysis on hydrophone and accelerometer raw data. For hydrophone signals, the raw data is analyzed with applied spectrum analysis to complete real-time self-noise calculation, a waterfall plot, and a 1/3 octave graphical display of the time-frequency spectrum relationship. Similarly, the system continuously performs FFT calculations on each sensor for the accelerometer.

SDMS data retrieval and SDMS warning records

Through the history sub-panel, users can browse through the previous test process to find the recorded TDMS files. Through the visual record sub-panel, users can see the historical list of all warning events and system events. The filter options can be used to filter by date, start time and end time, and event type.

in conclusion

The combination of NI hardware and LabVIEW software enabled our team to develop applications in a short period of time, even when faced with complex customer requirements. In total, we spent five months manually designing, developing, and testing the software application. Especially in the initial stage, we also used graphical programming to test the program and easily debug it.

Figure 3: Hydrophone subpanel and waterfall visualization