Imperial College London

ProfessorMirkoKovac

Faculty of EngineeringDepartment of Aeronautics

Professor in Aerial Robotics
 
 
 
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Contact

 

+44 (0)20 7594 5063m.kovac Website

 
 
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Location

 

326City and Guilds BuildingSouth Kensington Campus

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Summary

 

Publications

Publication Type
Year
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66 results found

Kovac M, Sequeira Guedes Tristany Farinha A, di Tria J, Zufferey R, Armanini Set 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.

Conference paper

Wiesemuller F, Winston C, Poulin A, Aeby X, Miriyev A, Geiger T, Nystrom G, Kovac Met al., 2021, Self-sensing cellulose structures with design-controlled stiffness, IEEE Robotics and Automation Letters, Vol: 6, Pages: 4017-4024, ISSN: 2377-3766

Robots are often used for sensing and sampling in natural environments. Within this area, soft robots have become increasingly popular for these tasks because their mechanical compliance makes them safer to interact with. Unfortunately, if these robots break while working in vulnerable environments, they create potentially hazardous waste. Consequently, the development of compliant, biodegradable structures for soft, eco-robots is a relevant research area that we explore here. Cellulose is one of the most abundant biodegradable materials on earth, but it is naturally very stiff, which makes it difficult to use in soft robots. Here, we look at both biologically and kirigami inspired structures that can be used to reduce the stiffness of cellulose based parts for soft robots up to a factor of 19 000. To demonstrate this, we build a compliant force and displacement sensing structure from microfibrillated cellulose. We also describe a novel manufacturing technique for these structures, provide mechanical models that allow designers to specify their stiffness, and conclude with a description of our structure's performance.

Journal article

Kocer B, Hady A, Kandath H, Pratama M, Kovac Met al., 2021, Deep neuromorphic controller with dynamic topology for aerial robots, ICRA 2021, Publisher: IEEE

Current aerial robots are increasingly adaptive; they can morph to enable operation in changing conditions to complete diverse missions. Each mission may require the robot to conduct a different task. A conventional learning approach can handle these variations when the system is trained for similar tasks in a representative environment. However, it may result in overfitting to the new data stream or the failure to adapt, leading to degradation or a potential crash. These problems can be mitigated with an excessive amount of data and embedded model, but the computational power and the memory of the aerial robots are limited. In order to address the variations in the model, environment as well as the tasks within onboard computation limitations, we propose a deep neuromorphic controller approach with variable topologies to handle each different condition and the data stream with a feasible computation and memory allocation. The proposed approach is based on a deep neuromorphic (multi and variable layered neural network) controller with dynamic depth and progressive layer adaptation for each new data stream. This adaptive structure is combined with a switching function to form a sliding mode controller. The network parameter update rule guarantees the stability of the closed loop system by the convergence of the error dynamics to the sliding surface. Being the first implementation on an aerial robot in this context, the results illustrate the adaptation capability, stability, computational efficiency as well as the real-time validation.

Conference paper

Xiao F, Zheng P, Di Tria J, Kocer BB, Kovac Met al., 2021, Optic flow based reactive collision prevention for MAVs using the fictitious obstacle hypothesis, IEEE Robotics and Automation Letters, Vol: 6, Pages: 3144-3151, ISSN: 2377-3766

Optical flow sensors and optical flow divergence (OFD) have offered partial solutions for obstacle avoidance, landing, and perching with micro aerial vehicles. Theoretically, OFD can indicate the risk of collision, providing that the sensors’ field of view is bounded within a single flat surface on the obstacle. However, in the real world, directly measuring the risk of collision with OFD generates false alarms due to rapidly changing speeds and irregular surroundings. In this letter, we present a new obstacle detection strategy based on an extended Kalman filter (EKF) combining the OFD with inertial sensing. The introduction of a fictitious obstacle hypothesis and the use of the EKF estimates enable us to differentiate the surrounding-generated OFD from the OFD caused by the actual obstacle. An embedded constant zero-OFD controller is then used for post-detection emergency deceleration. The ultra-light OFD estimation and control system, with a mass of 20 g , estimates OFD at 160 Hz . The system was validated on a 158 g mini quadrotor in both laboratory and field tests. Experimental results illustrate that the presented system can achieve accurate obstacle detection, near-obstacle distance estimation, and controlled deceleration to prevent collisions. 1 1Video attachment: https://youtu.be/yIyYHYN0jOw.

Journal article

Miriyev A, Kovac M, 2020, Skills for physical artificial intelligence, Nature Machine Intelligence, Vol: 2, Pages: 658-660, ISSN: 2522-5839

Synthesizing robots via physical artificial intelligence is a multidisciplinary challenge for future robotics research. An education methodology is needed for researchers to develop a combination of skills in physical artificial intelligence.

Journal article

Farinha A, Zufferey R, Zheng P, Armanini SF, Kovac Met 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].

Journal article

Hamaza S, Kovac M, 2020, Omni-drone: on the design of a novel aerial manipulator with omni-directional workspace, 17th International Conference on Ubiquitous Robots (UR), Publisher: IEEE, Pages: 153-158, ISSN: 2325-033X

Aerial manipulation is a nascent research area that offers major impact for infrastructure monitoring and repair. While several design and control methods have been presented, there is still a need for new mechatronic solutions that are structurally optimised for aerial manipulation tasks. In this paper we present a novel design for a manipulator tailored for aerial applications with a high level of morphological integration with the robot frame. A hybrid system is presented that comprises a 5-bar linkage parallel robot with an additional active joint for the swirling motion about a pivotal point. The design offers an omnidirectional workspace about the aerial vehicle, enhancing the versatility of the aerial system and the tasks that can be accomplished. The mechanical design of the proposed robot, the analysis of the kinematics and the study of the workspace are presented. The novel manipulator represents the first of its kind, enabling aerial interaction with ceilings, curved surfaces and side interaction with facades.

Conference paper

Zheng P, Tan X, Kocer BB, Yang E, Kovac Met al., 2020, TiltDrone: a fully-actuated tilting quadrotor platform, IEEE Robotics and Automation Letters, Vol: 5, Pages: 6845-6852, ISSN: 2377-3766

Multi-directional aerial platforms can fly in almost any orientation and direction, often maneuvering in ways their under-actuated counterparts cannot match. A subset of multi-directional platforms are fully-actuated multirotors, where all six degrees of freedom are independently controlled without redundancies. Fully-actuated multirotors possess much greater freedom of movement than conventional multirotor drones, allowing them to perform complex sensing and manipulation tasks. While there has been comprehensive research on multi-directional multirotor control systems, the spectrum of hardware designs remain fragmented. This paper sets out the hardware design architecture of a fully-actuated quadrotor and its associated control framework. Following the novel platform design, a prototype was built to validate the control scheme and characterize the flight performance. The resulting quadrotor was shown in operation to be capable of holding a stationary hover at 30° incline, and track position commands by thrust vectoring.

Journal article

Debruyn D, Zufferey R, Armanini SF, Winston C, Farinha A, Jin Y, Kovac Met 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.

Journal article

Dams B, Sareh S, Zhang K, Shepherd P, Kovac M, Ball RJet al., 2020, Aerial additive building manufacturing: three-dimensional printing of polymer structures using drones, Proceedings of the Institution of Civil Engineers: Construction Materials, Vol: 173, Pages: 3-14, ISSN: 1747-650X

This paper describes the first aerial additive building manufacturing system developed to create and repair civil engineering structures remotely using polymers extruded from unmanned aerial robots (drones). The structural potential of three commercially available expanding polyurethane foams of varying density (LD40, Reprocell 300 and Reprocell 500), and their feasibility for deposition using an autonomous flying dual-syringe device is described. Test specimens consisting of one and two layers, with horizontal and vertical interfaces, were mechanically tested both parallel and perpendicular to the direction of expansion. LD40 specimens exhibited ductile failure in flexural tests and provided evidence that the interfaces between layers were not necessarily regions of weaknesses. Hand-mixed specimens of Reprocell 500 possessed compressive strengths comparable to those of concrete and flexural strengths similar to those of the lower range of timber, though they exhibited brittle failure. There are challenges to be faced with matching the performance of hand-mixed specimens using an autonomous dual-syringe deposition device, primarily concerning the rheological properties of the material following extrusion. However, the device successfully imported and deposited two liquid components, of varying viscosity, and maintained correct mixing ratios. This work has demonstrated the structural and operational feasibility of polyurethane foam as a viable structural material for remote three-dimensional printing using drones.

Journal article

Zufferey R, Ancel AO, Farinha A, Siddall R, Armanini SF, Nasr M, Brahmal R, Kennedy G, Kovac Met 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.

Journal article

Zufferey R, Ancel AO, Raposo C, Armanini SF, Farinha A, Siddall R, Berasaluce I, Zhu H, Kovac Met al., 2019, SailMAV: Design and Implementation of a Novel Multi-Modal Flying Sailing Robot, IEEE Robotics and Automation Letters, Vol: 4, Pages: 2894-2901, ISSN: 2377-3766

Despite significant research progress on small-scale aerial-aquatic robots, most existing prototypes are still constrained by short operation times and limited performance in different fluids. The main challenge is to design a vehicle that satisfies the partially conflicting design requirements for aerial and aquatic operations. In this letter we present a new class of aerial-aquatic robot, the sailing micro air vehicle, 'SailMAV.' Thanks to a three-part folding wing design, the SailMAV is capable of both flying and sailing. The robot design permits long and targeted missions at the water interface by leveraging the wind as movement vector. It simultaneously offers the flexibility of flight for rapidly reaching a designated area, overcoming obstacles, and moving from one body of water to another, which can be very useful for water sampling in areas with many obstacles. With a total wingspan of 0.96 m, the SailMAV employs the same wing and actuation surfaces for sailing as for flying. It is capable of water surface locomotion as well as takeoff and flight at a cruising speed of 10.8 mcdots-1. The main contributions of this letter are new solutions to the challenges of combined aerial and aquatic locomotions, the design of a novel hybrid concept, the development of the required control laws, and the demonstration of the vehicle successfully sailing and taking off from the water. This letter can inform the design of hybrid vehicles that adapt their morphology to move effectively.

Journal article

Armanini SF, Siddall R, Kovac M, 2019, Modelling and simulation of a bioinspired aquatic micro aerial vehicle, AIAA Aviation 2019 Forum, Publisher: American Institute of Aeronautics and Astronautics, Pages: 1-18

Conference paper

Hai-Nguyen N, Siddall R, Stephens B, Navarro-Rubio A, Kovac Met al., 2019, A passively adaptive microspine grapple for robust, controllable perching, 2nd IEEE International Conference on Soft Robotics (RoboSoft), Publisher: IEEE, Pages: 80-87

The application of flying systems to practical tasks is consistently limited by the poor endurance of hovering robots. The ability to perch to fixed surfaces allows a robot to gather data and inspect structures in a low power state, while retaining the access and manoeuvrability that flight offers. In this paper we present a passively adaptive perching mechanism which allows an aerial vehicle to stably attach to a variety of surfaces including tree branches and pipelines. This is enabled by a compliant grapple module, which passively conforms to the surface of convex perching targets, ensuring reliable traction and a very high load capacity (tension tested to > 60 kg in some instances) whilst still releasing effortlessly. This is due to the mechanics of the grapple, which is designed to passively tighten and attach to a variety of branch diameters and shapes. The grapple is paired with a hybrid force-motion controller which allows the cable tension to be regulated as the vehicle achieves the desired attitude. The hybrid control approach exploits the mechanical compliance of the system to ensure reliable, stable attachment to irregular natural structures, and the addition of a winch allows the robot to stably orient itself in any position or orientation relative to the branch. This approach demonstrates tensile perching using adaptive anchors. The presented subsystems can be applied to other robots where high force authority is required.

Conference paper

Zhang K, Zhu Y, Lou C, Zheng P, Kovac Met al., 2019, A design and fabrication approach for pneumatic soft robotic arms using 3D printed origami skeletons, 2nd IEEE International Conference on Soft Robotics (RoboSoft), Publisher: IEEE, Pages: 821-827

Soft robots which employ materials with inherent compliance have demonstrated great potential in a variety of applications such as manipulators, medical tools and wearable devices. This paper presents an origami-folding inspired design and fabrication approach for developing semi-soft robotic arms. The approach starts from a conceptual design by identifying foldable origami structures. This is followed by the kinematic modelling of the selected origami skeleton with base folds of thick panels and flexible hinges. The final step realizes the design by 3D printing the skeleton and laminating the skeleton to flexible membranes on a heated vacuum table. Following the proposed approach, a foldable origami tube structure is designed, modelled and used as the exoskeleton for a pneumatic semi-soft robotic arm. Prototypes are developed by laminating a pair of 3D printed thermoplastic polyurethane (TPU) origami skeleton structures with TPU fabric film. The soft arm is actuated by a vacuum pump and its performances is evaluated through quasi-static tests. Experimental results show that the soft robotic arm achieves a maximum contraction ratio of 47.53% providing 23.463 N axial tension force when applying a regulated negative pressure of -1 bar. Two extensible and foldable pneumatic arms are integrated on a micro aerial vehicle (MAV) to obtain a platform with the potential of aerial manipulation capabilities in confined and hard to reach areas.

Conference paper

Petersen KH, Napp N, Stuart-Smith R, Rus D, Kovac Met al., 2019, A review of collective robotic construction, Science Robotics, Vol: 4, Pages: 1-10, ISSN: 2470-9476

The increasing need for safe, inexpensive, and sustainable construction, combined with novel technological enablers, has made large-scale construction by robot teams an active research area. Collective robotic construction (CRC) specifically concerns embodied, autonomous, multirobot systems that modify a shared environment according to high-level user-specified goals. CRC tightly integrates architectural design, the construction process, mechanisms, and control to achieve scalability and adaptability. This review gives a comprehensive overview of research trends, open questions, and performance metrics.

Journal article

Chermprayong P, Zhang K, Xiao F, Kovac Met al., 2019, An integrated delta manipulator for aerial repair a new aerial robotic system, IEEE Robotics and Automation magazine, Vol: 26, Pages: 54-66, ISSN: 1070-9932

Unmanned aerial vehicles (UAVs) are capable of entering hazardous areas and accessing hardto-reach locations at high altitudes. However, small-scale UAVs are inherently unstable when exposed to challenging environments. Additionally, their ability to accurately interact with infrastructure is limited by the need to stabilize the vehicle precisely in flight.

Journal article

Tzoumanikas D, Li W, Grimm M, Zhang K, Kovac M, Leutenegger Set al., 2019, Fully autonomous micro air vehicle flight and landing on a moving target using visual–inertial estimation and model-predictive control, Journal of Field Robotics, Vol: 36, Pages: 49-77, ISSN: 1556-4959

The Mohamed Bin Zayed International Robotics Challenge (MBZIRC) held in spring 2017 was a very successful competition well attended by teams from all over the world. One of the challenges (Challenge 1) required an aerial robot to detect, follow, and land on a moving target in a fully autonomous fashion. In this paper, we present the hardware components of the micro air vehicle (MAV) we built with off the self components alongside the designed algorithms that were developed for the purposes of the competition. We tackle the challenge of landing on a moving target by adopting a generic approach, rather than following one that is tailored to the MBZIRC Challenge 1 setup, enabling easy adaptation to a wider range of applications and targets, even indoors, since we do not rely on availability of global positioning system. We evaluate our system in an uncontrolled outdoor environment where our MAV successfully and consistently lands on a target moving at a speed of up to 5.0 m/s.

Journal article

Zhang K, Chermprayong P, Tzoumanikas D, Li W, Grimm M, Smentoch M, Leutenegger S, Kovac Met al., 2019, Bioinspired design of a landing system with soft shock absorbers for autonomous aerial robots, Journal of Field Robotics, Vol: 36, Pages: 230-251, ISSN: 1556-4959

One of the main challenges for autonomous aerial robots is to land safely on a target position on varied surface structures in real‐world applications. Most of current aerial robots (especially multirotors) use only rigid landing gears, which limit the adaptability to environments and can cause damage to the sensitive cameras and other electronics onboard. This paper presents a bioinpsired landing system for autonomous aerial robots, built on the inspire–abstract–implement design paradigm and an additive manufacturing process for soft thermoplastic materials. This novel landing system consists of 3D printable Sarrus shock absorbers and soft landing pads which are integrated with an one‐degree‐of‐freedom actuation mechanism. Both designs of the Sarrus shock absorber and the soft landing pad are analyzed via finite element analysis, and are characterized with dynamic mechanical measurements. The landing system with 3D printed soft components is characterized by completing landing tests on flat, convex, and concave steel structures and grassy field in a total of 60 times at different speeds between 1 and 2 m/s. The adaptability and shock absorption capacity of the proposed landing system is then evaluated and benchmarked against rigid legs. It reveals that the system is able to adapt to varied surface structures and reduce impact force by 540N at maximum. The bioinspired landing strategy presented in this paper opens a promising avenue in Aerial Biorobotics, where a cross‐disciplinary approach in vehicle control and navigation is combined with soft technologies, enabled with adaptive morphology.

Journal article

Sareh P, Chermprayong P, Emmanuelli M, Nadeem H, Kovac Met al., 2018, Rotorigami: A rotary origami protective system for robotic rotorcraft, Science Robotics, Vol: 3, ISSN: 2470-9476

Applications of aerial robots are progressively expanding into complex urban and natural environments. Despite remarkable advancements in the field, robotic rotorcraft is still drastically limited by the environment in which they operate. Obstacle detection and avoidance systems have functionality limitations and substantially add to the computational complexity of the onboard equipment of flying vehicles. Furthermore, they often cannot identify difficult-to-detect obstacles such as windows and wires. Robustness to physical contact with the environment is essential to mitigate these limitations and continue mission completion. However, many current mechanical impact protection concepts are either not sufficiently effective or too heavy and cumbersome, severely limiting the flight time and the capability of flying in constrained and narrow spaces. Therefore, novel impact protection systems are needed to enable flying robots to navigate in confined or heavily cluttered environments easily, safely, and efficiently while minimizing the performance penalty caused by the protection method. Here, we report the development of a protection system for robotic rotorcraft consisting of a free-to-spin circular protector that is able to decouple impact yawing moments from the vehicle, combined with a cyclic origami impact cushion capable of reducing the peak impact force experienced by the vehicle. Experimental results using a sensor-equipped miniature quadrotor demonstrated the impact resilience effectiveness of the Rotary Origami Protective System (Rotorigami) for a variety of collision scenarios. We anticipate this work to be a starting point for the exploitation of origami structures in the passive or active impact protection of robotic vehicles.

Journal article

Sareh P, Chermprayong P, Emmanuelli M, Nadeem, Kovac Met al., 2018, The spinning cyclic ‘Miura-oRing’ for mechanical collision-resilience, The 7th International Meeting on Origami in Science, Mathematics and Education

Conference paper

Jarvis R, Farinha A, Kovac M, Cegla Fet al., 2018, NDE sensor delivery using unmanned aerial vehicles, Insight (Northampton): non-destructive testing and condition monitoring, Vol: 60, Pages: 463-467, ISSN: 1354-2575

The robotic deployment of NDE sensors has great cost-saving potential in cases where the measurement cost is high due to access restrictions or the need to temporarily decommission the test structure. Unmanned aerial vehicles (UAVs) are able to quickly reach inaccessible components to perform visual inspection and deploy NDE sensors. In this work, a mechanical sensor release mechanism is presented that has enabled electromagnetic acoustic transducers (EMATs) to be deployed onto a ferromagnetic pipe and a plate, after which the component wall thickness measurements can be transmitted wirelessly to a remote location. The reliability of the method and the most promising areas for future development are discussed.

Journal article

Goldberg B, Zufferey R, Doshi N, Helbling EF, Whittredge G, Kovac M, Wood RJet al., 2018, Power and Control Autonomy for High-Speed Locomotion With an Insect-Scale Legged Robot, IEEE ROBOTICS AND AUTOMATION LETTERS, Vol: 3, Pages: 987-993, ISSN: 2377-3766

Journal article

Zhang K, Chermprayong P, Alhinai TM, Siddall R, Kovac Met al., 2017, SpiderMAV: Perching and stabilizing micro aerial vehicles with bio-inspired tensile anchoring systems, 2017 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS), Publisher: IEEE, Pages: 6849-6854, ISSN: 2153-0858

Whilst Micro Aerial Vehicles (MAVs) possess a variety of promising capabilities, their high energy consumption severely limits applications where flight endurance is of high importance. Reducing energy usage is one of the main challenges in advancing aerial robot utility. To address this bottleneck in the development of unmanned aerial vehicle applications, this work proposes an bioinspired mechanical approach and develops an aerial robotic system for greater endurance enabled by low power station-keeping. The aerial robotic system consists of an multirotor MAV and anchoring modules capable of launching multiple tensile anchors to fixed structures in its operating envelope. The resulting tensile perch is capable of providing a mechanically stabilized mode for high accuracy operation in 3D workspace. We explore generalised geometric and static modelling of the stabilisation concept using screw theory. Following the analytical modelling of the integrated robotic system, the tensile anchoring modules employing high pressure gas actuation are designed, prototyped and then integrated to a quadrotor platform. The presented design is validated with experimental tests, demonstrating the stabilization capability even in a windy environment.

Conference paper

Sareh S, Althoefer K, Li M, Noh Y, Tramacere F, Sareh P, Mazzolai B, Kovac Met al., 2017, Anchoring like octopus: biologically inspired soft artificial sucker, Journal of the Royal Society Interface, Vol: 14, Pages: 1-9, ISSN: 1742-5662

This paper presents a robotic anchoring module, a sensorized mechanism for attachment to the environment that can be integrated into robots to enable or enhance various functions such as robot mobility, remaining on location or its ability to manipulate objects. The body of the anchoring module consists of two portions with a mechanical stiffness transition from hard to soft. The hard portion is capable of containing vacuum pressure used for actuation while the soft portion is highly conformable to create a seal to contact surfaces. The module is integrated with a single sensory unit which exploits a fibre-optic sensing principle to seamlessly measure proximity and tactile information for use in robot motion planning as well as measuring the state of firmness of its anchor. In an experiment, a variable set of physical loads representing the weights of potential robot bodies were attached to the module and its ability to maintain the anchor was quantified under constant and variable vacuum pressure signals. The experiment shows the effectiveness of the module in quantifying the state of firmness of the anchor and discriminating between different amounts of physical loads attached to it. The proposed anchoring module can enable many industrial and medical applications where attachment to environment is of crucial importance for robot control.

Journal article

Chen Y, Wang H, Helbling EF, Jafferis NT, Zufferey R, Ong A, Ma K, Gravish N, Chirarattananon P, Kovac M, Wood RJet al., 2017, A biologically inspired, flapping-wing, hybrid aerial-aquatic microrobot, Science Robotics, Vol: 2, ISSN: 2470-9476

From millimeter-scale insects to meter-scale vertebrates, several animal species exhibit multimodal locomotive capabilities in aerial and aquatic environments. To develop robots capable of hybrid aerial and aquatic locomotion, we require versatile propulsive strategies that reconcile the different physical constraints of airborne and aquatic environments. Furthermore, transitioning between aerial and aquatic environments poses substantial challenges at the scale of microrobots, where interfacial surface tension can be substantial relative to the weight and forces produced by the animal/robot. We report the design and operation of an insect-scale robot capable of flying, swimming, and transitioning between air and water. This 175-milligram robot uses a multimodal flapping strategy to efficiently locomote in both fluids. Once the robot swims to the water surface, lightweight electrolytic plates produce oxyhydrogen from the surrounding water that is collected by a buoyancy chamber. Increased buoyancy force from this electrochemical reaction gradually pushes the wings out of the water while the robot maintains upright stability by exploiting surface tension. A sparker ignites the oxyhydrogen, and the robot impulsively takes off from the water surface. This work analyzes the dynamics of flapping locomotion in an aquatic environment, identifies the challenges and benefits of surface tension effects on microrobots, and further develops a suite of new mesoscale devices that culminate in a hybrid, aerial-aquatic microrobot.

Journal article

Siddall R, Kennedy G, Kovac M, 2017, High-Power Propulsion Strategies for Aquatic Take-off in Robotics, Robotics Research

Book chapter

Siddall RJD, Kovac M, Kennedy G, 2017, High power propulsion strategies for aquatic take-off in robotics, International Symposium on Robotics Research 2015, Publisher: Springer

The ability to move between air and water with miniature robots would allow distributedwater sampling and monitoring of a variety of unstructured marine environments,such as coral reefs and coastal areas. To enable such applications, we are developing anew class of aerial-aquatic robots, called Aquatic Micro Aerial Vehicles (AquaMAVs),capable of diving into the water and returning to flight. One of the main challenges inthe development of an AquaMAV is the provision of sufficient power density for take-offfrom the water. In this paper, we present a novel system for powerful, repeatable aquaticescape using acetylene explosions in a 34 gram water jet thruster, which expels watercollected from its environment as propellant. We overcome the miniaturisation problemsof combustible fuel control and storage by generating acetylene gas from solid calciumcarbide, which is reacted with enviromental water. The produced gas is then combusted inair in a valveless combustion chamber to produce over 20N of thrust, sufficient to propelsmall robots into the air from water. The system for producing combustible gases fromsolid fuels is a very compact means of gas storage, and can be applied to other forms ofpneumatic actuation and inflatable structure deployment.

Conference paper

Braithwaite A, Alhinai T, Haas-Heger M, McFarlane E, Kovac Met al., 2017, Spider inspired construction and perching with a swarm of nano aerial vehicles, Robotics Research, Editors: Bicchi, Burgard, Publisher: Springer, Pages: 71-88

Autonomous construction with aerial vehicles has great potential for in-situ repair and construction in hard-to-access areas. In this paper, we present and demonstrate a mechanism by which a team of autonomous nano aerial vehicles construct a multi-element tensile structure between anchor points in an irregular environment, such as a natural woodland. Furthermore, we demonstrate potential applications of such a structure to enable long-term position holding of aerial vehicles that are otherwise extremely limited in terms of available flight time due to energy constraints. To demonstrate the effectiveness of this mechanism, we develop the mechanical and electronic designs of two payload packages for attachment to nano quadrotor robots with a total integrated mass of only 26 g per robot, and we present the trajectory planning and control algorithms required to enable robust execution of the construction scheme.

Book chapter

Goldberg B, Doshi N, Wood RJ, 2017, High speed trajectory control using an experimental maneuverability model for an insect-scale legged robot, 2017 IEEE International Conference on Robotics and Automation (ICRA), Publisher: IEEE

Conference paper

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