Publications
53 results found
Hammad A, Armanini SF, 2024, Landing and take-off capabilities of bioinspired aerial vehicles: a review., Bioinspir Biomim, Vol: 19
Bioinspired flapping-wing micro aerial vehicles (FWMAVs) have emerged over the last two decades as a promising new type of robot. Their high thrust-to-weight ratio, versatility, safety, and maneuverability, especially at small scales, could make them more suitable than fixed-wing and multi-rotor vehicles for various applications, especially in cluttered, confined environments and in close proximity to humans, flora, and fauna. Unlike natural flyers, however, most FWMAVs currently have limited take-off and landing capabilities. Natural flyers are able to take off and land effortlessly from a wide variety of surfaces and in complex environments. Mimicking such capabilities on flapping-wing robots would considerably enhance their practical usage. This review presents an overview of take-off and landing techniques for FWMAVs, covering different approaches and mechanism designs, as well as dynamics and control aspects. The special case of perching is also included. As well as discussing solutions investigated for FWMAVs specifically, we also present solutions that have been developed for different types of robots but may be applicable to flapping-wing ones. Different approaches are compared and their suitability for different applications and types of robots is assessed. Moreover, research and technology gaps are identified, and promising future work directions are identified.
Giordano A, Achenbach L, Lenggenhager D, et al., 2024, A Soft Robotic Morphing Wing for Unmanned Underwater Vehicles, Advanced Intelligent Systems
Actuators based on soft elastomers offer significant advantages to the field of robotics, providing greater adaptability, improving collision resilience, and enabling shape-morphing. Thus, soft fluidic actuators have seen an expansion in their fields of application. Closed-cycle hydraulic systems are pressure agnostic, enabling their deployment in extremely high-pressure conditions, such as deep-sea environments. However, soft actuators have not been widely adopted on unmanned underwater vehicle control surfaces for deep-sea exploration due to their unpredictable hydrodynamic behavior when camber-morphing is applied. This study presents the design and characterization of a soft wing and investigates its feasibility for integration into an underwater glider. It is found that the morphing wing enables the glider to adjust the lift-to-drag ratio to adapt to different flow conditions. At the operational angle of attack of 12.5°, the lift-to-drag ratio ranges from −70% to +10% compared to a rigid version. Furthermore, it reduces the need for internal moving parts and increases maneuverability. The findings lay the groundwork for the real-world deployment of soft robotic principles capable of outperforming existing rigid systems. With the herein-described methods, soft morphing capabilities can be enabled on other vehicles.
Siddall R, Zufferey R, Armanini S, et al., 2023, The Natural Robotics Contest: crowdsourced biomimetic design, BIOINSPIRATION & BIOMIMETICS, Vol: 18, ISSN: 1748-3182
Helmchen F, Armanini SF, Hupfer A, 2023, A Framework to Elaborate on the Requirements for Electrified Commuter and Regional Aircraft, Aerospace, Vol: 10
With increasing capabilities of electric motors and energy storage, aircraft designs for electrified commuter and regional aircraft become more relevant than ever. Design concepts are often derived and optimised according to existing, conventional reference aircraft; however, their characteristics differ and the underlying trade-offs are divergent. This work aims to derive and describe major external requirements for the design of proposed commuter and regional aircraft system. Therefore, a travel time benefit analysis was conducted that considered the European NUTS-3 regions, as well as the concentration of population. Total travel times for individual road, high-speed rail, commuter air services, and traditional airline services were compared. Travel time calculations were based mostly on third-party road and railway APIs, whereas airline services were based on air traffic management data. The data show a concentration of potential commuter connections on distances between 200 and 950 km. The majority of these connections are currently operated on airline flights, which involve extraordinarily long first/last mile transportation. The majority of regions are already well covered with airfields offering sufficient runway length; however, air traffic capacities and apron space could become major bottlenecks when considering a possible shift from airline to decentral commuter air services.
Broers KC, Armanini SF, 2022, Design and Testing of a Bioinspired Lightweight Perching Mechanism for Flapping-Wing MAVs Using Soft Grippers, IEEE ROBOTICS AND AUTOMATION LETTERS, Vol: 7, Pages: 7526-7533, ISSN: 2377-3766
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Zufferey R, Siddall R, Armanini SF, et al., 2022, Diving from Flight, Biosystems and Biorobotics, Pages: 99-129
Having measured the longitudinal aerodynamics of the AquaMAV in wind tunnel tests (cf. Chap. 7 ), the data gathered can then be used to analyse the dive performance of the vehicle, as well as estimate and evaluate its dynamic properties. As in Sect. 6.4, we begin by considering a quasi-steady state model, where, furthermore, the aerial and aquatic phases are considered separately and transition phases are omitted. This model is used to obtain planar dive trajectories for both the purely aerial and the purely aquatic phase, providing a clear overview of the achievable performance of the robot. In the second part of the chapter, a more detailed model of the vehicle is developed that accounts for some dynamic effects and explicitly includes the air-to-water transition. The latter model is used to obtain more insight into the vehicle dynamics and into the impact phase. It also serves as a basis for simulations covering several envisaged mission stages.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Between Sea and Sky: Aerial Aquatic Locomotion in Miniature Robots, Biosystems and Biorobotics, Pages: 1-9
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Zufferey R, Siddall R, Armanini SF, et al., 2022, Aquatic Escape: Repeatable Escape with Combustion, Biosystems and Biorobotics, Pages: 131-153
Several systems have been developed with aerial-aquatic locomotion capabilities but without demonstrating consecutive transitions to flight from water. Moreover, while some multirotor vehicles possess the ability to operate in both air and water [108, 109], the transition to flight is typically constrained to very calm sea conditions. Fixed-wing robots able to transition dynamically between water and air through high-power thrust bursts represent a low-cost, versatile and more reliable solution. Compared to multirotor vehicles, this approach that would simultaneously result in an increased flight range and allow for aquatic escape in a wider variety of conditions.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Synthetic Aerial Aquatic Locomotion, Biosystems and Biorobotics, Pages: 33-41
A wealth of research exists into the broader question of how robotic mobility can be expanded beyond a single domain/terrain. A significant amount of recent research attention has been given to the implementation of aerial-terrestrial mobility into miniature robots [94], resulting in mobile robots with shared subsystems and additional mechanisms which are analogous to the AquaMAV robot presented in Chap. 7.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Breaking the Surface, Biosystems and Biorobotics, Pages: 3-11
Most animals use different forms of locomotion to move through a varied environment. This allows them to adapt to find food, escape threats or migrate, while minimising their energetic cost of locomotion. To do so, animals must use the same locomotor modules to perform specialised tasks that often have opposed requirements. For example, an animal diving into the water to hunt requires a structure that is as lightweight as possible for efficient flight, whilst still being structurally strong when impacting the water’s surface.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Preface, Biosystems and Biorobotics, Vol: 29, Pages: v-vii, ISSN: 2195-3562
Zufferey R, Siddall R, Armanini SF, et al., 2022, Practical Tips for Building Aerial-Aquatic Robots, Biosystems and Biorobotics, Pages: 213-228
This book would not be complete without a chapter on practical hardware and software elements used throughout the presented robots. We hope that this can serve as a rough toolbox for aerial-aquatic vehicle development, and cover some of the prototyping choices that are often under-reported in academic literature, but consume outsize research time.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Sailing and Flying with a Multimodal Robot, Biosystems and Biorobotics, Pages: 167-195
The field of aerial-aquatic robotics promises tremendous benefits in data collection as well as unmatched flexibility and remote access. However, the majority of existing aerial-aquatic robots are unable to perform scientific tasks at significant depth, limited by the weight penalty that any pressure resistant container would add. In addition, sealing of an actuated robot is difficult, again adding significant weight to small systems. Wireless communication is a major challenge for underwater robots and certainly poses great constraints to operation at distance. Lastly, underwater propulsion is often highly inefficient due to geometries optimised for flight [109]. Indeed, most aerial-aquatic vehicles either have severely limited water range and operation, stay in very shallow waters or function only in de-ionised water. Too often, the benefit of underwater locomotion is overshadowed by the weight, and complexity increases that are required for reliable operation. This negatively impacts flight performance.
Zufferey R, Siddall R, Armanini SF, et al., 2022, The Physics of Aerial Aquatic Locomotion, Biosystems and Biorobotics, Pages: 43-53
This chapter presents an overview of some fundamental physical laws and concepts at play in generic, as clarified in Figs. 5.1 and 5.2. The vehicle-specific physics are then introduced in the following chapters and form the basis for locomotion derived for the different vehicles presented.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Efficient Water-Air Propulsion with a Single Propeller, Biosystems and Biorobotics, Pages: 155-166
In the previous chapters, aquatic launch and dives into water with small flying robots have been demonstrated. An AquaMAV prototype was presented which was capable of self propelled-flight in air and able to escape water, but this robot had no means of propelling itself beneath the surface. To add aquatic locomotion it is attractive to use the same propulsion system as is used for flight, as this reduces the weight and complexity of the system. However, the increase in load on the propeller in a denser fluid results in much slower rotation speeds, and means a significant loss of motor efficiency.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Aerial-Aquatic Locomotion in Nature, Biosystems and Biorobotics, Pages: 19-31
Water covers 363 million square km, or 72% of the earth’s surface. The vast majority of this water is saline (96%), frozen (2%) or groundwater (1%). The 10 5 km 3 of surface freshwater (0.008%) is in turn concentrated almost entirely in three large great lake systems (Fig. 3.1), with a vanishing small amount of surface freshwater forming lakes and rivers.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Aquatic Escape: Fast Escape with a Jet Thruster, Biosystems and Biorobotics, Pages: 57-76
In a previous chapter an idealised water jet thruster was analysed, and it was argued that the most effective system would use large pressures to drive a small volume of water. In this chapter a more detailed physical model of water jet propulsion will be introduced, and the key design features of a jet thruster prototype detailed. Consistent static thrust from the fabricated device is then demonstrated.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Why Swim and Fly?, Biosystems and Biorobotics, Pages: 13-18
We live on a water-covered planet that is facing rapid change, both globally and locally, due to a combination of human behaviour and natural phenomena [31]. Understanding these changes requires in-depth scientific understanding of our environment. Key to enabling this is the fast, accurate and repeated provision of extensive physical data. However, obtaining dependable geospatial data is itself frequently a challenge, requiring new sensing approaches or considerable adjustments to existing methods.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Airframe Design for Plunge Diving, Biosystems and Biorobotics, Pages: 77-98
In this chapter the design of a plunge diving AquaMAV is detailed. This enhanced AquaMAV prototype is capable of propelled flight, wing retraction for diving into water and jet propelled aquatic escape. The selection process for key components is detailed, as well as the specific attributes necessary for aerial-aquatic locomotion. The AquaMAV includes some limited automation, to allow the robot to self launch when in water, where radio communication is challenging.
Zufferey R, Siddall R, Armanini SF, et al., 2022, Multirotor Aircraft and the Aquatic Environment, Biosystems and Biorobotics, Pages: 197-211
The previous chapters presented hybrid robot concepts and prototypes relying on the use of fixed wings for lift generation. The higher flight efficiency of such devices makes them suitable for covering large distances and can even serve to extend their locomotion envelope (see Chap. 11 ).
Zufferey R, Siddall R, Armanini SF, et al., 2022, Conclusion, Biosystems and Biorobotics, Pages: 229-237
This book introduces the concept of small, unmanned aerial-aquatic robotics. This novel field of research aims to merge the benefits of flight and aquatic operation into one lightweight autonomous platform. As the reader will have seen in this book, wildly different robots can be envisioned as solutions to this formidable challenge.
Martinez-Ponce J, Urban C, Armanini S, et al., 2022, Aerodynamic Analysis of V-Shaped Flight Formation of Flapping-Wing Drones: Analytical and Experimental Studies
This paper aims to simulate and design a V-shaped flight formation of flapping wing drones for the purpose of analyzing the induced drag experienced on each drone. Similar experiments have conducted analysis on V-shaped flight formations of drones. However, the distinct difference between this paper and other experiments is that this paper will utilize a flapping wing motion on the drones, while the other experiments utilized fixed-wing drones. The effects of flapping-wing drones may have a better correlation to the effects experienced on migrating birds when they form V-shaped flights, thus bringing further insight into how aerodynamical effects of V-shaped formation flights aid migrating birds. Furthermore, experimenting with flapping-wing drones in V-shaped flights may also bring insight into increasing the power efficiency of drones.
Devta A, Metz IC, Armanini SF, 2022, EVALUATION AND QUANTIFICATION OF THE POTENTIAL CONSEQUENCES OF BIRD STRIKES IN URBAN AIR MOBILITY, Pages: 6818-6834
The development of air taxis, driven by advances in electric propulsion, promises new opportunities for Urban Air Mobility. As the aviation industry directs increasingly more attention towards the development of such vehicles, however, new operational challenges and safety concerns are emerging. A major bottleneck for the aviation authorities will be the integration of Urban Air Mobility vehicles into the existing airspace. A successful integration is challenging and needs to consider several aspects. One of these is the hazard of bird strikes. While bird strike poses a risk to any type of aircraft, the risk is expected to be higher in the case of urban air vehicles due to several reasons. Flying at lower altitudes, future air taxis will be more likely to collide with birds. In addition, air taxis are expected to be smaller and have lower certification requirements than conventional aircraft, and will hence be more vulnerable to damaging collisions. In this paper, a detailed impact force analysis is conducted to evaluate and quantify the consequences of collisions between air taxis and birds in terms of impact force, and additionally a Graphical User Interface is developed to visualize the results. By considering both bird-related and aircraft-related parameters in the analysis, a comprehensive evaluation is obtained that provides improved insight into the bird strike problem in the context of Urban Air Mobility. Results are evaluated in the context of bird strike requirements for Vertical Take Off and Landing vehicle proposed by EASA. The conducted analysis implies that the current specifications could be further strengthened by considering additional factors such as bird speed, aircraft material density, angle of impact and depth of penetration.
Panchal I, Metz IC, Ribeiro M, et al., 2022, URBAN AIR TRAFFIC MANAGEMENT FOR COLLISION AVOIDANCE WITH NON-COOPERATIVE AIRSPACE USERS, Pages: 6801-6817
With the rise of new and innovative Urban Air Mobility solutions, there also arises a need to integrate these into the existing airspace. Current airspace users include conventional civil, commercial and general aviation, military air users, police and emergency services as well as a plethora of avian life. Planned additions to the airspace are electric vertical take-off and landing vehicles such as logistics drones and air taxis. The airspace for conventional users is stringently controlled. Urban Air Mobility operations are expected to mainly take place in individual corridors to be added to the currently uncontrolled low-level airspace. This airspace is also intended for various types of drone operations, out of which, small-scale drones can be non-co-operative. In addition, the operational altitudes of Urban Air Mobility aircraft will strongly expose them to birds. Due to abundance of these non-cooperating airspace users (like hobby-drones and birds), conflicts with Urban Air Mobility aircraft are expected to be inevitable. The aim of this paper is to develop a concept of Urban Air Mobility Collision Avoidance System to reduce the likelihood of collision between air taxis and non-cooperating airspace users. As such, this work proposes the introduction of an additional safety layer to prevent collisions during operations of strong exposure. The concept consists of a conflict detection and resolution method tailored for Urban Air Mobility operations. A three-dimensional safety envelope is designed using the geometric and performance values of the aircraft configurations currently available. Procedures to avoid conflicts prior to as well as during the flights are presented. Finally, the concept is visualized for the common use case of a shuttle service between an airport and a railway station. The results demonstrate the importance of incorporating individual aircraft configuration into conflict avoidance approach and report its effect to avoid collision.
Devta A, Metz IC, Armanini SF, 2022, EVALUATION AND QUANTIFICATION OF THE POTENTIAL CONSEQUENCES OF BIRD STRIKES IN URBAN AIR MOBILITY, ISSN: 1025-9090
The development of air taxis, driven by advances in electric propulsion, promises new opportunities for Urban Air Mobility. As the aviation industry directs increasingly more attention towards the development of such vehicles, however, new operational challenges and safety concerns are emerging. A major bottleneck for the aviation authorities will be the integration of Urban Air Mobility vehicles into the existing airspace. A successful integration is challenging and needs to consider several aspects. One of these is the hazard of bird strikes. While bird strike poses a risk to any type of aircraft, the risk is expected to be higher in the case of urban air vehicles due to several reasons. Flying at lower altitudes, future air taxis will be more likely to collide with birds. In addition, air taxis are expected to be smaller and have lower certification requirements than conventional aircraft, and will hence be more vulnerable to damaging collisions. In this paper, a detailed impact force analysis is conducted to evaluate and quantify the consequences of collisions between air taxis and birds in terms of impact force, and additionally a Graphical User Interface is developed to visualize the results. By considering both bird-related and aircraft-related parameters in the analysis, a comprehensive evaluation is obtained that provides improved insight into the bird strike problem in the context of Urban Air Mobility. Results are evaluated in the context of bird strike requirements for Vertical Take Off and Landing vehicle proposed by EASA. The conducted analysis implies that the current specifications could be further strengthened by considering additional factors such as bird speed, aircraft material density, angle of impact and depth of penetration.
Kovac M, Sequeira Guedes Tristany Farinha A, di Tria J, et al., 2021, Challenges in control and autonomy of unmanned aerial-aquatic vehicles, 29th Mediterranean Conference on Control and Automation (MED), Publisher: IEEE, Pages: 937-942
Autonomous aquatic vehicles capable of flight can deploy more rapidly, access remote or constricted areas, overfly obstacles and transition easily between distinct bodies of water. This new class of vehicles can be referred as Unmanned Aerial-Aquatic Vehicles (UAAVs), and is capable of reaching distant locations rapidly, conducting measurements and returning to base. This greatly improves upon current solutions, which often involve integrating different types of vehicles (e.g. vessels releasing underwater vehicles), or rely on manpower (e.g. sensors dropped manually from ships). Thanks to recent research efforts, UAAVs are becoming more sophisticated and robust. Nonetheless numerous challenges remain to be addressed, and particularly dedicated control and sensing solutions are still scarce. This paper discusses challenges and opportunities in UAAV control, sensing and actuation. Following a brief overview of the state of the art, we elaborate on the requirements and challenges for the main types of robots and missions proposed in the literature to date, and highlight existing solutions where available. The concise but wide-ranging overview provided will constitute a useful starting point for researchers undertaking UAAV control work.
Farinha A, Zufferey R, Zheng P, et al., 2020, Unmanned aerial sensor placement for cluttered environments, IEEE Robotics and Automation Letters, Vol: 5, Pages: 6623-6630, ISSN: 2377-3766
Unmanned aerial vehicles (UAVs) have been shown to be useful for the installation of wireless sensor networks (WSNs). More notably, the accurate placement of sensor nodes using UAVs, opens opportunities for many industrial and scientific uses, in particular, in hazardous environments or inaccessible locations. This publication proposes and demonstrates a new aerial sensor placement method based on impulsive launching. Since direct physical interaction is not required, sensor deployment can be achieved in cluttered environments where the target location cannot be safely approached by the UAV, such as under the forest canopy. The proposed method is based on mechanical energy storage and an ultralight shape memory alloy (SMA) trigger. The developed aerial system weighs a total of 650 grams and can execute up to 17 deployments on a single battery charge. The system deploys sensors of 30 grams up to 4 meters from a target with an accuracy of ±10 cm. The aerial deployment method is validated through more than 80 successful deployments in indoor and outdoor environments. The proposed approach can be integrated in field operations and complement other robotic or manual sensor placement procedures. This would bring benefits for demanding industrial applications, scientific field work, smart cities and hazardous environments [Video attachment: https://youtu.be/duPRXCyo6cY].
Debruyn D, Zufferey R, Armanini SF, et al., 2020, MEDUSA: a multi-environment dual-robot for underwater sample acquisition, IEEE Robotics and Automation Letters, Vol: 5, Pages: 4564-4571, ISSN: 2377-3766
Aerial-aquatic robots possess the unique ability of operating in both air and water. However, this capability comes with tremendous challenges, such as communication incompatibility, increased airborne mass, potentially inefficient operation in each of the environments and manufacturing difficulties. Such robots, therefore, typically have small payloads and a limited operational envelope, often making their field usage impractical. We propose a novel robotic water sampling approach that combines the robust technologies of multirotors and underwater micro-vehicles into a single integrated tool usable for field operations. The proposed solution encompasses a multirotor capable of landing and floating on the water, and a tethered mobile underwater pod that can be deployed to depths of several meters. The pod is controlled remotely in three dimensions and transmits video feed and sensor data via the floating multirotor back to the user. The ‚dual-robot‛ approach considerably simplifies robotic underwater monitoring, while also taking advantage of the fact that multirotors can travel long distances, fly over obstacles, carry payloads and manoeuvre through difficult terrain, while submersible robots are ideal for underwater sampling or manipulation. The presented system can perform challenging tasks which would otherwise require boats or submarines. The ability to collect aquatic images, samples and metrics will be invaluable for ecology and aquatic research, supporting our understanding of local climate in difficult-to-access environments.
Nijboer JBW, Armanini SF, Karásek M, et al., 2020, Longitudinal grey-box model identification of a tailless flapping wing mav based on free-flight data
Tailless flapping wing micro aerial vehicles (FMWAVs) are known for their light weight and agility. However, given the fact that these FWMAVs have been developed only recently, their flight dynamics have not yet been fully explained. In this paper we develop grey-box models for the time-averaged longitudinal dynamics of a tailless FWMAV (DelFly Nimble) from free-flight data using closed-loop system identification techniques. The consequence of the tailless configuration is inherent instability, therefore tailless FWMAVs are generally more complex than their tailed counterparts and require an active feedback control system. The control system introduces additional challenges to the system identification process as it counteracts the perturbations required to excite the system. Based on this approach, grey-box models were estimated and validated for airspeeds ranging from hover conditions, 0 m/s, to 1.0 m/s forward flight. Despite the complexity of the system, we were able to obtain low-order local models that are both efficient and accurate (R2 values up to 0.92) and can therefore be used for stability analysis, simulation and control design. With these models we can also take the first steps towards fully understanding the flight dynamics of tailless FWMAVs.
Zufferey R, Ancel AO, Farinha A, et al., 2019, Consecutive aquatic jump-gliding with water-reactive fuel, Science Robotics, Vol: 4, Pages: 1-11, ISSN: 2470-9476
Robotic vehicles that are capable of autonomously transitioning between various terrains and fluids have received notable attention in the past decade due to their potential to navigate previously unexplored and/or unpredictable environments. Specifically, aerial-aquatic mobility will enable robots to operate in cluttered aquatic environments and carry out a variety of sensing tasks. One of the principal challenges in the development of such vehicles is that the transition from water to flight is a power-intensive process. At a small scale, this is made more difficult by the limitations of electromechanical actuation and the unfavorable scaling of the physics involved. This paper investigates the use of solid reactants as a combustion gas source for consecutive aquatic jump-gliding sequences. We present an untethered robot that is capable of multiple launches from the water surface and of transitioning from jetting to a glide. The power required for aquatic jump-gliding is obtained by reacting calcium carbide powder with the available environmental water to produce combustible acetylene gas, allowing the robot to rapidly reach flight speed from water. The 160-gram robot could achieve a flight distance of 26 meters using 0.2 gram of calcium carbide. Here, the combustion process, jetting phase, and glide were modeled numerically and compared with experimental results. Combustion pressure and inertial measurements were collected on board during flight, and the vehicle trajectory and speed were analyzed using external tracking data. The proposed propulsion approach offers a promising solution for future high-power density aerial-aquatic propulsion in robotics.
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