Aerial insects demonstrate fast and precise heading control when they perform body saccades and rapid escape maneuvers. While insect-scale micro-aerial-vehicles (IMAVs) have demonstrated early results on heading control, their flight endurance and heading angle tracking accuracy remain far inferior to that of natural fliers. In this work, we present a long endurance sub-gram aerial robot that can demonstrate effective heading control during hovering flight. Through using a tilted wing stroke-plane design, our robot demonstrates a 10-second flight where it tracks a desired yaw trajectory with maximum and root-mean-square (RMS) error of$\boldsymbol{14.2^{\circ}}$and$\boldsymbol{5.8}^{\mathrm{o}}$. The new robot design requires 7% higher lift forces for enabling heading angle control, which creates higher stress on wing hinges and adversely influences robot endurance. To address this challenge, we developed novel 3-layered wing hinges that exhibit 1.82 times improvement of lifetime. With the new wing hinges, our robot demonstrates a 40-second hovering flight - the longest among existing sub-gram IMAVs. These results represent substantial improvement of flight capabilities in soft-actuated IMAVs, showing the potential of operating these insect-like fliers in cluttered natural environments.

Flight is an energetically expensive task. While aerial insects can effortlessly fly through natural environments, achieving power autonomous flights in insect-scale robots remains a major challenge. In prior works, we developed soft-actuated insect-scale aerial robots that demonstrated unique capabilities such as in-flight collision recovery and somersaults. However, the soft dielectric elastomer actuators (DEAs) have low efficiency (600 V). These properties represent formidable obstacles for soft aerial robots to achieve power autonomous flights. In this work, we developed a 127 mg boost circuit that can convert a 7.7 V DC input into a 600 V and 400 Hz output for driving a 120 mg DEA. It has an equivalent capacitance and resistance of 20 nF and 5$\mathbf{k}\Omega$, respectively. The DEA is assembled into a 158 mg aerial robot, which can demonstrate liftoff while carrying the boost circuit as a payload. Although the robot remains tethered to an off-board power supply, this result represents a first step towards achieving power autonomy in soft aerial robots.

Simulating the swimming of soft underwater robot remains challenging due to the absence of an efficient numerical framework that can effectively capture the geometrically nonlinear deformation of soft materials and structures when interacting with a liquid environment. Here, we address this by introducing a discrete differential geometry-based model that incorporates an implicit treatment of the elasticity of soft limbs and a fluid model with three different components: hydrodynamic drag, jetting, and virtual added mass. The physical engine can run faster than real-time on a single thread desktop processor. We experimentally validate this numerical simulation tool by performing tests using an untethered omni-directional star-shaped swimming soft robot that is capable of moving with multiple swimming gaits. Quantitative agreement between experiment and simulation indicates the potential application of such a numerical framework for robot design and for model-based control schemes.

Flying insects are remarkably agile and robust. As they fly through cluttered natural environments, they can demonstrate aggressive acrobatic maneuvers such as backflip, rapid escape, and in-flight collision recovery. Current state-of-the-art subgram microaerial-vehicles (MAVs) are predominately powered by rigid actuators such as piezoelectric ceramics, but they have low fracture strength (120 MPa) and failure strain (0.3%). Although these existing systems can achieve a high lift-to-weight ratio, they have not demonstrated insect-like maneuvers such as somersault or rapid collision recovery. In this article, we present a 665 mg aerial robot that is powered by novel dielectric elastomer actuators (DEA). The new DEA achieves high power density (1.2 kW/kg) and relatively high transduction efficiency (37%). We further incorporate this soft actuator into an aerial robot to demonstrate novel flight capabilities. This insect-scale aerial robot has a large lift-to-weight ratio (>2.2:1) and it achieves an ascending speed of 70 cm/s. In addition to demonstrating controlled hovering flight, it can recover from an in-flight collision and perform a somersault within 0.16 s. This work demonstrates that soft aerial robots can achieve insect-like flight capabilities absent in rigid-powered MAVs, thus showing the potential of a new class of hybrid soft-rigid robots.