This study introduces an agile robotic penguin featuring a pair of 2-degrees of freedom (DoF) wing mechanisms. Each wing can independently control flapping and feathering motions with two in-house submersible geared servomotors through a differential gear mechanism. Notably, our mechanism allows unrestricted feathering beyond 360°. Since feathering directly changes the wing’s angle of attack (AoA), the hydrodynamic forces can be significantly adjusted to achieve agile maneuvers. This paper demonstrates various maneuvers, including rapid acceleration, hard braking, rolling, pitching, and yawing, achieved solely by changing the feathering motion of both wings. Our robotic penguin reached a maximum forward speed of 1.8 m/s, comparable to the foraging speed of real penguins. The average roll, pitch, and yaw rates were 363°/s, 75°/s, and 92°/s, respectively. This robot serves as a model for the biological study of maneuverability in real penguins and the engineering exploration of bioinspired agile underwater robots.

Hovering hummingbirds have inspired small flapping-wing aerial robots. Natural flyers, including hummingbirds and bats, undergo torsional wing deformation during flapping flight owing to complex wing structure, while previous artificial wings were relatively simple and difficult to design the torsional flexibility. In this paper, we proposed a hummingbird-bat hybrid (HBH) wing in which torsional flexibility was implemented by an available fabrication technology. The HBH wing had a torsional arm at the leading edge inspired by a torsional wrist of a hummingbird. A bat-like stretchable wing membrane was also employed not to constrain the wing torsion. The membrane was supported by wing shafts of which bending stiffness was designed based on that of the feather shaft of a hummingbird. The three-dimensional (3-D) shape of the torsional arm and wing shafts was created by 3-D printing. The effect of the torsional arm and stretchable membrane on lift generation and deformation was evaluated using an electric flapping mechanism. It was confirmed that the torsional arm actually enhanced the passive wing torsion. The stretchable wing membrane further promoted the torsion effect of the torsional arm. Consequently, the HBH wing did not increase lift, but efficacy, defined as lift per input power, was greatly improved by 14% at most compared with the wing without a torsional arm.

This paper proposes a haptic assistance system that provides momentary steering wheel torque to help the driver choose the steering direction for avoiding collision with a pedestrian. The results of an experiment with a driving simulator showed that reaction time was reduced significantly when using haptic assistance and that the system was effective in enhancing appropriate selection of a steering direction in many cases. However, there were cases in which the drivers' choice was opposite to the system's proposal. In order for the system to be acceptable to drivers, the drivers' natural choice of direction should be taken into account.

Hummingbirds are promising reference for small flying robots in terms of their excellent ability to hover. Wing kinematics and shape of a hovering hummingbird were measured with four high-speed video cameras. Four types of wing models consisting of carbon fiber rods and polymer membranes with the same planform as the hummingbird wing were fabricated. 1-degree-of-freedom (DOF) flapping experiments with the wing models were performed, where the wing deformation and vertical force (hereafter called `lift') were measured. The model wings demonstrated similar feathering deformation as that of the hummingbird in the upstroke. In addition, the model wing with a loosened membrane which caused larger feathering deformation produced lift enough to support the weight of the hummingbird. The results suggest that hovering hummingbirds could be modeled as a pair of 1-DOF flapping wings with a thin membrane which passively feathers.

This paper discusses an assistance system that add tiny torque to the steering wheel momentarily to help the driver choose the direction for avoiding collision with a pedestrian. In order to investigate the effectiveness of the system, we conducted an experiment with a medium fidelity driving simulator. The results of the experiment showed that there existed situations where the system was effective to enhance driver's appropriate selection of steering direction. In addition, the system reduced the driver reaction time significantly. However, there were cases in which the drivers completely disagreed with the system's proposal. In order to make such a system be acceptable to drivers, drivers' way of choosing a direction should be taken into account.

Three types of artificial butterfly wings were fabricated for investigating the morphological function of actual butterfly wings. They consist of a thin polymer membrane and micromolded polyurethane veins. The planar shape and venation of one type were the same as those of a swallowtail butterfly, and those of the other two were different. The effect of the distribution of stiffness over the wings by the veins on flight characteristics during free forward flight was investigated using an ornithopter and the three different types of wing. The overall aerodynamic coefficients were the highest for the wings with veins the same as those of a swallowtail butterfly, indicating that the veins enable slow forward flight.

We developed a very small and light butterfly-type ornithopter (BTO) to investigate butterfly flight. Its weight is 0.4 g, wing span is 140 mm and flapping frequency is 10 Hz. It flies forward passively. The flights were recorded with a highspeed video camera and the longitudinal motion of the BTO was analyzed. When the center of gravity was appropriate, the angle of attack of the body varied cyclically. We found that the cyclical change of the angle of attack produced total upward aerodynamic force. Then we visualized air flow around the BTO both in tethered flight and in free flight. We revealed that free body motion caused a stable attachment of leading edge vortex. We also found that the free body motion helped the wings' smooth upstroke, which was not found in tethered flight.