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Vertical Take-Off and Landing (VTOL) Unmanned Aerial Vehicles (UAVs) provide a versatile platform well-suited to applications requiring the efficiency of fixed-wing flight with the maneuverability of a multicopter. Prior work has introduced the concept of using solar energy harvesting using photovoltaic cells embedded in the wings of the vehicle to perform self-recharge in the field when landed and at rest. This work demonstrates a further extension of this concept by optimizing the VTOL aircraft for maximum input-to-output power ratio, such that continuous flight is possible for the majority of a typical day with good sunlight. By also adding amphibious design elements, a transoceanic flight cycle is proposed. The candidate aircraft design is shown with estimated and actual behavioral and performance data for hovering and forward flight. Artwork for design elements such as the tiltrotor nacelle design and interchangeable avionics pod are shown. 

This works deals with the problem of long-term autonomy in the context of multi-day field deployments of Micro Aerial Vehicle (MAV) systems. To truly depart from the necessity for human intervention for the crucial task of providing battery recharging, and to liberate from the need to operate in a confined range around specially installed infrastructure such as recharging pods, the MAV robot is required to harvest power on its own, but equally importantly also sustain prolonged periods of ambient power scarcity. This implies being able to sustain the battery charge overnight when using solar recharging, or even during multiple days of illumination inadequacy (e.g., due to degraded atmospheric lucidity and heavy overcast). We address this by presenting a Self-Sustainable Autonomous System architecture for MAVs centered around a specially tailored Power Management Stack, which is capable of achieving deep system hibernation, a feature that facilitates the aforementioned functionalities. We present a) continuous, b) multi-day successive, and c) externally-powered recharging that uses a legged robot-mounted Mobile Recharging Station. We conclude by demonstrating a challenging zero-intervention multi-day field deployment mission in the N.Nevada region. 

In this work we address the flexible physical docking-and-release as well as recharging needs for a marsupial system comprising an autonomous tiltrotor hybrid Micro Aerial Vehicle and a high-end legged locomotion robot. Within persistent monitoring and emergency response situations, such aerial / ground robot teams can offer rapid situational awareness by taking off from the mobile ground robot and scouting a wide area from the sky. For this type of operational profile to retain its long-term effectiveness, regrouping via landing and docking of the aerial robot onboard the ground one is a key requirement. Moreover, onboard recharging is a necessity in order to perform systematic missions. We present a framework comprising: a novel landing mechanism with recharging capabilities embedded into its design, an external battery-based recharging extension for our previously developed power-harvesting Micro Aerial Vehicle module, as well as a strategy for the reliable landing and the docking-and-release between the two robots. We specifically address the need for this system to be ferried by a quadruped ground system while remaining reliable during aggressive legged locomotion when traversing harsh terrain. We present conclusive experimental validation studies by deploying our solution on a marsupial system comprising the MiniHawk micro tiltrotor and the Boston Dynamics Spot legged robot. 

This paper presents a novel strategy for the autonomous deployment of Micro Aerial Vehicle scouts through constricted aperture-like ingress points, by narrowly fitting and launching them with a high-precision Mobile Manipulation robot. A significant problem during exploration and reconnaissance into highly unstructured environments, such as indoor collapsed ones, is the encountering of impassable areas due to their constricted and rigid nature. We propose that a heterogeneous robotic system-of-systems armed with manipulation capabilities while also ferrying a fleet of micro-sized aerial agents, can deploy the latter through constricted apertures that marginally fit them in size, thus allowing them to act as scouts and resume the reconnaissance mission. This work's contribution is twofold: first, it proposes active-vision based aperture detection to locate candidate ingress points and a hierarchical search-based aperture profile analysis to position a MAV's body through them, and secondly it presents and experimentally demonstrates the novelty of a system-of-systems approach which leverages mobile manipulation to deploy other robots which are otherwise incapable of entering through extremely narrow openings. 

This work presents the design and autonomous navigation policy of the Resilient Micro Flyer, a new type of collision-tolerant robot tailored to fly through extremely confined environments and manhole-sized tubes. The robot maintains a low weight (<500g) and implements a combined rigid-compliant design through the integration of elastic flaps around its stiff collision-tolerant frame. These passive flaps ensure compliant collisions, contact sensing and smooth navigation in contact with the environment. Focusing on resilient autonomy, capable of running on resource-constrained hardware, we demonstrate the beneficial role of compliant collisions for the reliability of the onboard visual-inertial odometry and propose a safe navigation policy that exploits both collision-avoidance using lightweight time-of-flight sensing and adaptive control in response to collisions. The robot further realizes an explicit manhole navigation mode that exploits the direct mechanical feedback provided by the flaps and a special navigation strategy to self-align inside manholes with non-straight geometry. Comprehensive experimental studies are presented to evaluate, both individually and as a whole, how resilience is achieved based on the robot design and its navigation scheme. 

This work addresses the rapidly-prototyped design of a small Tricopter/Fixed-Wing Vertical Take-Off and Landing UAS with solar-recharge-capability, capable of repeatedly landing, recharging, and taking off, without need for physical intervention or externally placed maintenance devices or platforms. The design uses Fused Deposition Modeling 3D printing to rapidly prototype and fabricate the majority of the aircraft structures and parts. Provisions are made for carrying high-level single board computing solutions, or other similar payloads. Details are provided for mechanisms, aerodynamic geometry, solar cell integration and manufacturability. The design is analyzed to estimate inertial moments, aerodynamic performance, and static and dynamic stability. Simulation models for the Gazebo and RealFlight environments are provided, targeting Software-In-The-Loop architectures that run the ArduPilot and PX4 flight stacks. A flight testing methodology is developed, and results are presented with multiple prototype vehicles constructed. We finally contribute all production definitions, files, and models as open-access resources, with the goal of supporting and promoting migratory/swarming behavior and autonomy research.