Wu Huadeng - Earthquake Administration of Guangdong Province
Ye Chunming - Earthquake Administration of Guangdong Province
Developing a seismic data acquisition system presents many challenges for engineers, such as realizing GPS synchronization, digital down sampling, multiplex control for signal calibration, and a variety of complicated triggering policies on a field-programmable gate array (FPGA); achieving communication between the MiniSEED seismic data package and the NetSeisIP seismic data flow in data interfaces; and conducting the required time domain index analysis, frequency analysis, and joint time-frequency analysis (JTFA). Also, we have to construct macroseismic alarms.
Using CompactRIO, we developed a highly reliable, low-cost seismic data acquisition system in a short period of time. The system has a powerful professional data triggering and storing function that supports the standard file formats used in the earthquake monitoring industry and satisfies the professional demand for seismic signal processing and analysis. This multichannel macroseismic monitoring and alarm system based on CompactRIO has been used successfully in the dedicated seismic response array in the Humen Pearl River Bridge in Guangdong, China.
The Makeup of the Macroseismic Monitoring and Alarm System
We designed the multichannel macroseismic monitoring and alarm system based on CompactRIO to remotely monitor and analyze the structural health and the macroseismic status of key projects, lifeline projects, high-rise buildings, and special structures in real time for long test periods. We can operate it as a distributed system or a single monitoring system.
The system is made up of three parts: the seismic observation station, dedicated line network, and data center (Figure 1).
We set up the data collector in the seismic observation station by adopting the CompactRIO data acquisition module, the GPS module, and the power supply module. The CompactRIO system includes the NI cRIO-9014 embedded real-time controller, the NI cRIO-9104 embedded chassis, the NI 9205 analog input module, the NI 9263 analog output module, and the NI 9401 high-speed digital I/O (HSDIO) module (Figure 2).
The Design of the System Software Framework
The software framework of the system is displayed through the data acquisition terminal and the control and analysis terminal of the upper computer. All the software at the data acquisition terminal is made up of two parts: data acquisition and communication. Data acquisition is realized on the FPGA and a real-time controller, thereby integrating very challenging functions such as GPS synchronization, digital down sampling, multiplex control for signal calibration, and various complicated triggering actions. In the communication interface, the data collector directly compresses the real-time data flow, packs the data in the MiniSEED format, and sends it to the remote seismic flow server or the control and analysis software in the upper computer according to the communication protocol for NetSeisIP seismic data flow (Figure 3).
The Communication Control and Analysis Software
The communication control and analysis software in the upper computer is composed of four main modules: the recorder configuration, real-time monitoring, data management, and data analysis modules. The recorder configuration module includes regular, data acquisition, channel, and event record information settings. The real-time monitoring module includes real-time display; channel representation; local record configuration; remote record; calibration signal; site information; system, connection, GPS capture, and second pulse locking status; macroseismic alarm; and key parameter real-time computing and display. The data management module includes reclamation and cancellation of data in the data collector and the updating and cancellation of local data. The data analysis module can analyze the time domain information, including maximum, minimum, peak value, RMS value, and mean value, of signals in real time or offline and carry out frequency analysis or JTFA of the waveform to calculate key parameters such as system health diagnostics and alarm status.
Using the powerful, efficient, and user-friendly LabVIEW graphical programming software with the advanced CompactRIO hardware platform, we designed a multichannel macroseismic monitoring and alarm platform that can perform sophisticated functions such as seismic signal tuning, data acquisition, clock synchronization, data compression and transmission, real-time data analysis, offline analysis, system health diagnostics, unexpected destructive seismic event alarming, network communication, and instrument control, which greatly reduced the new product development cycle time.
The multichannel macroseismic monitoring and alarm system based on CompactRIO met the design requirements for a high dynamic scope, high timing accuracy, high spectral purity, and multichannel and realized data compression. The innovative system uses the NI platform and transmission based on the NetSeisIP protocol. In the future, we plan to use NI products for similar research and development projects in the earthquake monitoring industry.
For more information on this case study, contact:
Earthquake Administration of Guangdong Province
Bldg 181 Xianlie Zhong Lu
Guangzhou, China 510070