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The relationship between the environment and the small-scaled behavior of marine animals is not fully understood. This is largely due to the difficulty in obtaining environmental datasets with a high spatiotemporal precision. The problem is particularly pertinent in assessing the influence of environmental factors in rapid high energy consuming behavior such as seabirds take-off. Here, to fill the gaps in existing database, we employed novel techniques using animal-borne sensors with motion records to estimate parameters on wind and ocean waves, and evaluated their influence on wandering albatrosses take-off. The measurement revealed that the wind speed and the wave height that the wandering albatrosses experienced during take-off ranged from 0.7 ∼ 15.4 m/s and 1.6 ∼ 6.4 m, respectively. The four indices that were measured (flapping number, frequency, running speed, and duration on the sea surface) also varied with the environmental conditions (i.e., flapping number varied from 0 to over 20). Importantly, taking-off was easier under higher wave condition in the constant wind speed, and take-off effort increased only when both wind and waves were gentle. Our data suggests that both ocean waves and winds play important roles in albatross take-off, and advances our current understanding of albatross flight mechanisms.Impact statementWinds and ocean waves condition experienced by albatrosses were estimated using animal-borne recorder and revealed that taking-off was easier under higher wave condition in the constant wind speed.

The way goal-oriented birds adjust their travel direction and route in response to the wind significantly affects their travel costs. This is expected to be particularly pronounced in albatrosses, which employ a wind-dependent flight style called dynamic soaring. Dynamic soaring birds in situations without a definite goal, e.g. searching for prey, are known to preferentially fly with tail-to-side winds to increase the speed and search area. However, little is known about their reaction to wind when heading to a definite goal, such as returning to their nest. For example, returning tracks of albatrosses vary from beelines to zigzags similar to that of sailboats; however, there is no empirical test of whether the wind causes this variation. Here, based on the similar wind-dependent speed between albatrosses and sailboats, we tested whether the time-minimizing strategies used by yacht racers can explain the locomotion patterns of wandering albatrosses. We predicted that when the goal is located upwind or downwind, albatrosses should (i) deviate their travel directions from the goal on the microscale and (ii) increase the number of turns on the macroscale. Both hypotheses were supported by track data from albatrosses and racing yachts in the Southern Ocean confirming that albatrosses qualitatively employ the same strategy as yacht racers. Nevertheless, albatrosses did not strictly minimize their travel time, likely making their flight robust against wind fluctuations. Our study provides the first empirical evidence of tacking in albatrosses and demonstrates that man-made movement strategies provide a new perspective on the laws underlying wildlife movement.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2021-03-10, 資料番号: PA2120030000

This paper addresses a system identification problem for multiple isolated systems whose parameters are partially identical. An approach to the problem is a centralized identification; a single estimator collects all the input-output data from all of the systems to estimate their parameters at once. However, the approach can be practically infeasible when it is applied to a large number of systems due to the limitation of computational and communication resources. To solve the issue, we propose a method of a networked identification composed of two stages: 1) Multiple estimators collect the data from their own target systems to independently derive temporary estimates of their parameters and a covariance matrix of the estimates. 2) Then, with communicating the temporary estimates and the covariance matrix, they update their estimates. We also show the optimality of the proposed networked identification method with respect to the modeling accuracy, which is equivalently achieved by the centralized identification. Finally, we show the effectiveness of the proposed method in a numerical simulation.

In this paper, a new system identification technique of flight characteristic of small unmanned aerial vehicles (UAVs) is proposed. The proposed method is characterized by the use of time-frequency information provided by wavelet transform. The use of wavelet transform enhances robustness against undesirable condition on small UAVs flight, such as wind gust. The effectiveness of the proposed method is validated using flight log obtained by special avionics in real flight of a small UAV. The target small UAV used for the validation and avionics are also introduced for completeness.

This paper will summarize recent research activities on small unmanned aerial vehicles at the University of Tokyo. The topics discussed are: fields of research, unmanned aerial vehicles currently used and under development, and avionics and ground control station software.

A new MEMS-based small, light, and cost-effective avionics is proposed in order to improve the current situation of system identification of small unmanned aerial vehicles (UAVs), which mostly depends on difficult wind tunnel tests. The avionics is capable of gathering navigation, wind, and control input data accurately. Flight tests with a small UAV are conducted, and its longitudinal stability derivatives are obtained accurately using flight data obtained by the avionics and system identification techniques.

A prototype tail-sitter mini unmanned aerial vehicle (SkyEyeV) was developed and tested in a wind tunnel and by remotely controlled flight. A tail-sitter is an aircraft that takes off and lands on its tail section with its fuselage pointing upward. The prototype is powered by twin electric motors, and has a 1.05 m wingspan and a takeoff weight of 2.4 kg. A key feature of the prototype is leading edge slats, which are designed to avoid stall during high angle of attack transitional flight. Through wind tunnel testing, the slats were confirmed to increase the stall angle of attack not only in a non-powered condition (without propeller) but also in a powered condition (wing in propeller slipstream). The remotely piloted flight tests verified the vehicle's designed flight capability, transition and hovering, and several useful insights were obtained.