Structural Motion Monitoring Using 9-Axis Sensing Modules with Wireless Communication Capability

Dynamic motion monitoring is useful for many applications such as modal testing, mechanical design, vibration control, structural coupling and theoretical model modifications. New sensing systems and sensing techniques for both translational and rotational motion are always in great need. This paper present two compact and portable motion sensing systems to monitor the dynamic behavior of complicated structures. Each system consists of a 9-axis sensing module and a control computer. As the sensing modules implement signal filtering, analogue to digital conversion and motion analysis on chip, no additional signal amplifiers are necessary. The modules get their power supply from the USB (Universal Serial Bus) port of the computer without involvement of extra power unit. The same cable for the sensor power supply serves to transfer the measured data from the module to the computer thus no oscilloscope is needed. The elimination of sensor power unit, amplifiers and oscilloscope greatly simplifies the measurement system and makes on-site motion monitoring much more convenient, especially when the accessible space is limited. The inertial loading and local stiffening effects introduced by conventional sensors are also reduced. In addition, for cases where the cable connection between the module and the computer is difficult or even impossible, wireless transmission modules can be incorporated into the system to form a wireless measurement system. Through experiments, it is found that the wireless data maintain their quality even after passing through a few concrete walls when wireless transmission distance is more than 60 meters.