Aerospace Technology Institute

Assessing particle-scale interactions and transport phenomena is essential yet complex within geophysical flows found in both natural and artificial settings. This research introduces the design, validation, and calibration of a spherical inertial sensor particle meticulously engineered to achieve full kinematic equivalence with a solid sphere. By employing Micro-Electro-Mechanical Systems Inertial Measurement Unit (MEMS-IMU) technology, this low cost 40 mm particle can measure triaxial acceleration up to ±16g and triaxial angular velocity up to ±2000°/s, operating at a high sampling rate of 1000 Hz over a duration of one hour. The sensor particle possesses a dual-layered spherical configuration deliberately crafted to ensure alignment in shape, density, center of mass, moment of inertia, and elastic modulus with that of a solid sphere. Its performance is rigorously assessed, validated, and calibrated through a series of physical experiments. Furthermore, a data enhancement technique grounded in lubrication theory is invented to mitigate technical challenges associated with accelerometer saturation and temporal resolution. This method enables our sensor particle to accurately capture particle collision processes within liquid environment, which proves challenging with conventional approaches. This investigation offers a foundational instrument for large-scale particle motion studies, such as those related to debris flows, facilitating, for the first time, the precise measurement of the dynamic behavior of individual particles within a substantial ensemble.

In this paper, the real-time cooperative guidance strategy for the aircraft trying to evade an incoming attacking missile was developed. The aircraft performs evasive maneuvers, launching a defender missile to divert the missile. Instead of classical strategies, which are based on optimal control or differential game, the engagement was formulated as a multi-agent game. The problem was solved by using the deep reinforcement learning method. To address the sparse reward problem, a general reward design method was presented utilizing the shaping technique. Guidance law, reward function, and training approach were demonstrated through the learning process and simulations. The application of the non-sparse reward function accelerated the model convergence. Considering a standard optimal guidance law as a benchmark, the effectiveness and advantages (guarantees of the aircraft's escape and win rates in multi-agent game) of the proposed guidance strategy were validated by the simulation results. Compared to the standard optimal guidance law, the proposed guidance strategy performed better with less prior knowledge.

The long-endurance station-keeping capability makes the autonomous airship a desirable platform to provide communication and surveillance services. An adaptive pursuit guidance law is proposed to realize the station-keeping of the airship under the influence of the unknown wind. The wind speed is estimated by an adaptive mechanism which is incorporated with the pursuit guidance law to guarantee the convergence to the mission site and realize station-keeping flight with the airspeed equal to the wind speed. The information required by the guidance law is easy to obtain. The results of the simulation show the effectiveness of the adaptive pursuit guidance law.