ABSTRACT
A miniaturized instrumented particle with an outer diameter of only 3 cm has been developed and calibrated. This particle has the capability of precisely and at a high frequency quantifying its inertial dynamics during motion, using microelectro-mechanical sensors (MEMS) fitted within it. The sensor consists of a triaxial accelerometer and gyroscope and a magnetometer as well as an internal digital motion processor, supporting up to 16g of measurable acceleration and up to 2000°/s of measurable rotational velocity. The MEMS sensor in use is commercially referred to as MPU9250, which is the world smallest 9-axis motion-tracking device. The sensor has the ability of continuous recording for at least one hour and storing the data in an internal memory unit at a rate of 200-1000Hz. The data can be easily transferred to a computer for further analysis using a USB connection at rate that is 10 times faster than the previous designs. In this work, sensor is calibrated using simple physical motions to validate the accelerometer, the gyroscope and the magnetometer readings. The uncertainties in the experiments and the sensors’ readings are quantified and noise values for the 3 sensors used in an appropriate filter for inertial sensor fusion are suggested. The instrumented particle provides a methodology for assessment of sediment entrainment by providing the exact flow conditions at which a grain is entrained from bed surface due to interactions with the near bed turbulent flow or other solid particles impinging on it during sediment transport in a non-intrusive and direct manner compared to traditional approaches. Therefore, the instrumented particle has a potential utility in providing an accurate geomorphic hazards monitoring for a range of applications spanning from riverbed destabilisation to scour of hydraulic infrastructure.
