A Collision Resilient Flying Robot

Flying robots that can locomote efficiently in GPS-denied cluttered environments have many applications, such as in search and rescue scenarios. However, dealing with the high amount of obstacles inherent to such environments is a major challenge for flying vehicles. Conventional flying platforms cannot afford to collide with obstacles, as the disturbance from the impact may provoke a crash to the ground, especially when friction forces generate torques affecting the attitude of the platform. We propose a concept of resilient flying robots capable of colliding into obstacles without compromising their flight stability. Such platforms present great advantages over existing robots as they are capable of robust flight in cluttered environments without the need for complex sense and avoid strategies or 3D mapping of the environment. We propose a design comprising an inner frame equipped with conventional propulsion and stabilization systems enclosed in a protective cage that can rotate passively thanks to a 3-axis gimbal system, which reduces the impact of friction forces on the attitude of the inner frame. After addressing important design considerations thanks to a collision model and validation experiments, we present a proof-of-concept platform, named GimBall, capable of flying in various cluttered environments. Field experiments demonstrate the robot's ability to fly fully autonomously through a forest while experiencing multiple collisions

SKOOTR: A SKating, Omni-Oriented, Tripedal Robot

In both animals and robots, locomotion capabilities are determined by the physical structure of the system. The majority of legged animals and robots are bilaterally symmetric, which facilitates locomotion with consistent headings and obstacle traversal, but leads to constraints in their turning ability. On the other hand, radially symmetric animals have demonstrated rapid turning abilities enabled by their omni-directional body plans. Radially symmetric tripedal robots are able to turn instantaneously, but are commonly constrained by needing to change direction with every step, resulting in inefficient and less stable locomotion. We address these challenges by introducing a novel design for a tripedal robot that has both frictional and rolling contacts. Additionally, a freely rotating central sphere provides an added contact point so the robot can retain a stable tripod base of support while lifting and pushing with any one of its legs. The SKating, Omni-Oriented, Tripedal Robot (SKOOTR) is more versatile and stable than other existing tripedal robots. It is capable of multiple forward gaits, multiple turning maneuvers, obstacle traversal, and stair climbing. SKOOTR has been designed to facilitate customization for diverse applications: it is fully open-source, is constructed with 3D printed or off-the-shelf parts, and costs approximately $500 USD to build

Aerial Field Robotics

Aerial field robotics research represents the domain of study that aims to equip unmanned aerial vehicles - and as it pertains to this chapter, specifically Micro Aerial Vehicles (MAVs)- with the ability to operate in real-life environments that present challenges to safe navigation. We present the key elements of autonomy for MAVs that are resilient to collisions and sensing degradation, while operating under constrained computational resources. We overview aspects of the state of the art, outline bottlenecks to resilient navigation autonomy, and overview the field-readiness of MAVs. We conclude with notable contributions and discuss considerations for future research that are essential for resilience in aerial robotics.Comment: Accepted in the Encyclopedia of Robotics, Springe

When Being Soft Makes You Tough: A Collision Resilient Quadcopter Inspired by Arthropod Exoskeletons

Flying robots are usually rather delicate, and require protective enclosures when facing the risk of collision. High complexity and reduced payload are recurrent problems with collision-tolerant flying robots. Inspired by arthropods' exoskeletons, we design a simple, easily manufactured, semi-rigid structure with flexible joints that can withstand high-velocity impacts. With an exoskeleton, the protective shell becomes part of the main robot structure, thereby minimizing its loss in payload capacity. Our design is simple to build and customize using cheap components and consumer-grade 3D printers. Our results show we can build a sub-250g, autonomous quadcopter with visual navigation that can survive multiple collisions at speeds up to 7m/s that is also suitable for automated battery swapping, and with enough computing power to run deep neural network models. This structure makes for an ideal platform for high-risk activities (such as flying in a cluttered environment or reinforcement learning training) without damage to the hardware or the environment

Design and control of a collision-resilient aerial vehicle with an icosahedron tensegrity structure

We present the tensegrity aerial vehicle, a design of collision-resilient rotor robots with icosahedron tensegrity structures. The tensegrity aerial vehicles can withstand high-speed impacts and resume operation after collisions. To guide the design process of these aerial vehicles, we propose a model-based methodology that predicts the stresses in the structure with a dynamics simulation and selects components that can withstand the predicted stresses. Meanwhile, an autonomous re-orientation controller is created to help the tensegrity aerial vehicles resume flight after collisions. The re-orientation controller can rotate the vehicles from arbitrary orientations on the ground to ones easy for takeoff. With collision resilience and re-orientation ability, the tensegrity aerial vehicles can operate in cluttered environments without complex collision-avoidance strategies. Moreover, by adopting an inertial navigation strategy of replacing flight with short hops to mitigate the growth of state estimation error, the tensegrity aerial vehicles can conduct short-range operations without external sensors. These capabilities are validated by a test of an experimental tensegrity aerial vehicle operating with only onboard inertial sensors in a previously-unknown forest.Comment: 12 pages, 16 figure

A Pocket Sized Foldable Quadcopter for Situational Awareness and Reconnaissance

Flying robots are rapidly becoming an essential tool in search and rescue missions because they can rapidly gather information from inaccessible or unsafe locations, thus increasing safety and rapidity of interventions. With this aim, we present a pocket sized foldable quadcopter equipped with a camera. The drone is a portable and rugged “flying-eye” that aims to extend or move the field of view of the rescuer for situational awareness and safe reconnaissance. The quadcopter can be packaged for transportation by folding its arms and it self-deploys in a glimpse before usage. Its compliant foldable arms make it rugged, reducing the risk of failure after collisions. The drone is remotely operated and it can stream sound, thermal and visual images in real time to rescuers. The prototype of the foldable quadcopter is experimentally characterized and assessed in preliminary field tests

Wall-contact sliding control strategy for a 2D caged quadrotor

This paper addresses the trajectory tracking problem of a 2D caged flying robot in contact with a wall. To simplify the contact problem, the models are constructed on a vertical two-dimensional plane, and our objective is to let the quadrotor hover or move along the wall with arbitrary velocity and attitude. The control law is derived using the Lyapunov stability theory, applying backstepping techniques to achieve exponential stability under mild assumptions. To overcome the unknown friction force between robot and wall, we design estimators for the friction coefficient, which include a projection operator that provides an upper bound for the obtained estimates. Realistic simulation results are provided to validate the proposed methodology

A multi-modal hovering and terrestrial robot with adaptive morphology

Most current drones are designed with a static morphology aimed at exploiting a single locomotion mode. This results in limited versatility and adaptability to multi-domain environments, such as those encountered in rescue missions, agriculture and inspection, where multiple locomotion capabilities could be more effective. For example, hovering and terrestrial locomotion are complementary and can increase versatility by allowing the robot achieve speed and ease of obstacle negotiation during flight, or low power consumption and reduced noise signature while moving on the ground. With this aim, the paper presents the design and characterization of a multi-modal quadcopter with adaptive morphology by means of foldable arms. After landing, the quadcopter folds the frontal arms and uses whegs and tracks to move on the ground. The foldable arms allow to decrease the size of the robot in order to achieve more mobility in confined ground environments; to perform a self-righting maneuver if the drone falls upside down; and to negotiate large gaps by strategically unfolding them during terrestrial locomotion