Vibration Transport of Lunar Regolith for In Situ Resource Utilization Using Piezoelectric Actuators with Displacement-Amplifying Mechanism

Abstract

In situ resource utilization on the Moon increases mission capability in lunar exploration and colonization. Lunar regolith is the most promising substance that can be used as a building material; its chemical composition includes metals, oxygen, helium-3, and water. Because the transportation of regolith is an essential and intricate part of its utilization, the author investigates a vibration transport system that uses a piezoelectric actuator combined with a displacement-amplifying mechanism. Although the load capacity of the piezoelectric actuator is substantially high, its movable displacement is low. Therefore, the displacement of the piezoelectric actuator was amplified approximately five times in the direction normal to the extending direction of the piezoelectric actuator to generate a high magnitude of vibration. A vibrational acceleration of approximately 7 g of the conveyor was achieved by optimizing the structure of the displacement-amplifying mechanism. The system has no frictional parts and does not require complicated controls or a significant amount of power; thus, it is compatible with space applications. We demonstrated both a flat and an inclined transport path through a small conveyor tube with a 26-mm inner diameter and 300-mm length. The results indicated a mass flow rate of approximately 7 g/s of the lunar regolith simulant at a reasonable speed (150 mm/s) through the tube on the horizontal conveyance and a maximum conveyance tilt angle of 24° in Earth conditions. In addition to the regolith transport, large particles in the regolith were observed to be susceptible to a downward fall in the tube, given the Brazil nut effect, and this feature was proposed to be used as a beneficiation system.