Development of Sensor Module for Seismic and Structural Monitoring With a Chip Scale Atomic Clock

Abstract eng:
In this paper, aiming for the application of seismic monitoring and structural monitoring, I discuss research and development regarding an autonomous time synchronization sensing system that maintains high-precision time information by a chip-scale atomic clock (CSAC). To realize next-generation seismic observation systems and maintenance management systems for building and civil structures, it is necessary to obtain measurement data in which time synchronization is achieved. For this purpose, it is desired that sensor modules themselves maintain accurate time information without depending on networks and GPS signals. Therefore, I developed a sensing system that maintains accurate time information autonomously, equipped with a CSAC, which is an ultrahigh-precision atomic clock that can be implemented in a substrate because of its ultralow power consumption and ultrasmall size. In this paper, the development of a practical sensor module that is an improvement of a previously developed prototype model is reported. First, the concepts of autonomous time synchronization and the CSAC are explained, and then a mechanism to append ultrahigh-precision time information to sensor data using a CSAC and the development of a prototype sensor module is described. In addition, improvement of the sensor module is explained in detail. The shaking table tests are performed on the improved sensor modules equipped with MEMS acceleration sensors, and the amplitude performance from a comparison with the measurement results of a servo-type acceleration sensor for controlling the shaking table is confirmed. In addition, from test results in which multiple improved sensor modules are placed on the shaking table while oscillation is added to those modules, it is confirmed that time synchronization within 0.001 seconds is realized for 100 Hz sampling. Furthermore, tests are performed in which the output from the displacement sensor in one module is branched to connect to eight improved sensor modules through the external analog sensor input interface in each module, and it is confirmed that the measurement results are in excellent agreement. From these results, it is confirmed that an autonomous time synchronization sensing system can be constructed, regardless of whether the built-in MEMS acceleration sensor or the external analog sensor input interface is used, which can be connected to various sensors. In conclusion, the developed autonomous time synchronization system enables the realization of high-density seismic observations in wide areas including underground and subsurface areas and structural health monitoring of building and civil structures.

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