Ryosuke Yajima

Development and field testing of UAV-based sampling devices for obtaining volcanic products

When an active volcano erupts, a restricted area is typically imposed around the crater of the volcano to protect people from volcanic phenomena. On the other hand, it is important to make observations inside the restricted area, to initiate alarms and make evacuation plans. Therefore, research and development of unmanned volcano exploration robots have been carried out all over the world. However, although ash sampling in restricted areas is an urgent necessity, there is no quick sampling method. Therefore, in this study, we aim to realize a sample-return system that uses a multi-rotor unmanned aerial vehicle (UAV) for obtaining volcanic products. In this paper, we introduce two sampling devices that we developed, and report results of indoor sampling experiments and outdoor field tests.

Traveling performance estimation for planetary rovers over slope

One of the most important requirements imposed on planetary rovers is the ability to minimize slippage while climbing slopes covered with loose soil. Therefore, at the design stage of the rovers, it is necessary to evaluate the traveling performance of their locomotion mechanisms over a slope. However, to conduct traveling tests over slopes, the sandbox in which the tests are conducted must be tilted; it is difficult and even dangerous to make a steep slope because of the heavy weight of the sandbox. Therefore, in this paper, we propose a new method for estimating the traveling performance of a wheeled rover over a slope. In this method, we estimate the slip ratio for different slope angles on the basis of traction tests over a flat terrain. To verify the proposed method, we conducted slope-climbing tests and traction tests in a sandbox using a two-wheeled rover with various types of wheels. Furthermore, we compared the slip ratios estimated from the slope-climbing tests with those estimated from the traction tests. From these comparisons, we concluded that the proposed method can accurately estimate the traveling performance of a planetary rover over a slope.

Field Report: UAV-Based Volcano Observation System for Debris Flow Evacuation Alarm

Once a volcano erupts, molten rocks, ash, pyroclastic flow, and debris flow can cause disasters. Debris flows can cause enormous damage over large areas. Therefore, a debris-flow simulation is an effective means of determining whether to issue an evacuation call for area residents. However, for safety purposes, restricted areas are set up around a volcano when it erupts. In these restricted areas, it is difficult to gather information such as the amount and permeability of the ash; this information is necessary for precise debris-flow simulations. To address this problem, we have developed an unmanned observation system for use in restricted areas around volcanoes. Our system is based on a multirotor micro unmanned aerial vehicle (MUAV); this system can be used to perform field tests in actual volcanic areas. In this paper, we report the field tests conducted at Mt. Unzen-Fugen during November 2016. The field tests included a demonstration of an unmanned surface flow measurement device and the deployment and retrieval of a small ground vehicle and a drop-down-type ash-depth measurement scale using an MUAV. In addition, we discuss some of the lessons learned.