Imperial College London

DrMirkoKovac

Faculty of EngineeringDepartment of Aeronautics

Senior Lecturer
 
 
 
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Contact

 

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

 
 
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Location

 

E 457ACE ExtensionSouth Kensington Campus

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Summary

 

Publications

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24 results found

Siddall RJD, Kovac M, Bioinspired Aerial-Aquatic Mobility for Miniature Robots, 2015 International Symposium on Adaptive Motion of Animals and Machines

CONFERENCE PAPER

Siddall RJD, Kovac M, Kennedy G, High Power Propulsion Strategies for Aquatic Take-off in Robotics, International Symposium on Robotics Research 2015, Publisher: Springer, ISSN: 1610-7438

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

Ancel AO, Eastwood R, Vogt D, Ithier C, Smith M, Wood R, Kovac M, Ortega Ancel A, Eastwood R, Vogt D, Ithier C, Smith M, Wood R, Kovač M, Ancel AO, Eastwood R, Vogt D, Ithier C, Smith M, Wood R, Kovač M, Ortega Ancel A, Eastwood R, Vogt D, Ithier C, Smith M, Wood R, Kovač M, Ortega Ancel A, Eastwood R, Vogt D, Ithier C, Smith M, Wood R, Kovač Met al., 2017, Aerodynamic evaluation of wing shape and wing orientation in four butterfly species using numerical simulations and a low-speed wind tunnel, and its implications for the design of flying micro-robots, INTERFACE FOCUS, Vol: 7, Pages: 20160087-20160087, ISSN: 2042-8898

Many insects are well adapted to long-distance migration despite the larger energetic costs of flight for small body sizes. To optimize wing design for next-generation flying micro-robots, we analyse butterfly wing shapes and wing orientations at full scale using numerical simulations and in a low-speed wind tunnel at 2, 3.5 and 5 m s(-1). The results indicate that wing orientations which maximize wing span lead to the highest glide performance, with lift to drag ratios up to 6.28, while spreading the fore-wings forward can increase the maximum lift produced and thus improve versatility. We discuss the implications for flying micro-robots and how the results assist in understanding the behaviour of the butterfly species tested.

JOURNAL ARTICLE

Floreano D, Zufferey J-C, Klaptocz A, Germann J, Kovac M, Floreano D, Zufferey JC, Klaptocz A, Germann J, Kovac Met al., 2017, Aerial Locomotion in Cluttered Environments, 15th International Symposium of Robotics Research (ISRR), Publisher: SPRINGER-VERLAG BERLIN, Pages: 21-39, ISSN: 1610-7438

© Springer International Publishing Switzerland 2017. Many environments where robots are expected to operate are cluttered with objects, walls, debris, and different horizontal and vertical structures. In this chapter, we present four design features that allow small robots to rapidly and safely move in 3 dimensions through cluttered environments: a perceptual system capable of detecting obstacles in the robot’s surroundings, including the ground, with minimal computation, mass, and energy requirements; a flexible and protective framework capable of withstanding collisions and even using collisions to learn about the properties of the surroundings when light is not available; a mechanism for temporarily perching to vertical structures in order to monitor the environment or communicate with other robots before taking off again; and a self-deployment mechanism for getting in the air and perform repetitive jumps or glided flight. We conclude the chapter by suggesting future avenues for integration of multiple features within the same robotic platform.

CONFERENCE PAPER

Sareh S, Siddall R, Alhinai T, Kovac Met al., 2017, Bio-inspired Soft Aerial Robots: Adaptive Morphology for High-Performance Flight, Soft Robotics Week - Trends, Applications and Challenges, Publisher: SPRINGER INT PUBLISHING AG, Pages: 65-74, ISSN: 2195-3562

CONFERENCE PAPER

Siddall R, Kovac M, Siddall R, Kovac M, Siddall R, Kovac M, Siddall R, Kovacet al., 2017, Fast Aquatic Escape With a Jet Thruster, IEEE-ASME TRANSACTIONS ON MECHATRONICS, Vol: 22, Pages: 217-226, ISSN: 1083-4435

© 2016 IEEE. The ability to collect water samples rapidly with aerial-aquatic robots would increase the safety and efficiency of water health monitoring and allow water sample collection from dangerous or inaccessible areas. An aquatic micro air vehicle (AquaMAV) able to dive into the water offers a low cost and robust means of collecting samples. However, small-scale flying vehicles generally do not have sufficient power for transition to flight from water. In this paper, we present a novel jet propelled AquaMAV able to perform jumpgliding leaps from water and a planar trajectory model that is able to accurately predict aquatic escape trajectories. Using this model, we are able to offer insights into the stability of aquatic takeoff to perturbations from surface waves and demonstrate that an impulsive leap is a robust method of flight transition. The AquaMAV uses a CO 2 powered water jet to escape the water, actuated by a custom shape memory alloy gas release. The 100 g robot leaps from beneath the surface, where it can deploy wings and glide over the water, achieving speeds above 11 m/s.

JOURNAL ARTICLE

Kovac M, Kovac M, Kovac M, Kovac M, Kovac Met al., 2016, ROBOTICS. Learning from nature how to land aerial robots., Science, Vol: 352, Pages: 895-896, ISSN: 0036-8075

One of the main challenges for aerial robots is the high-energy consumption of powered flight, which limits flight times to typically only tens of minutes for systems below 2 kg in weight (1). This limitation greatly reduces their utility for sensing and inspection tasks, where longer hovering times would be beneficial. Perching onto structures can save energy and maintain a high, stable observation or resting position, but it requires a coordination of flight dynamics and some means of attaching to the structure. Birds and insects have mastered the ability to perch successfully and have inspired perching robots at various sizes. On page 978 of this issue, Graule et al. (2) describe a perching robotic insect that represents the smallest flying robot platform that can autonomously attach to surfaces. At a mass of only 100 mg, it combines advanced flight control with adaptive mechanical dampers and electro-adhesion to perch on a variety of natural and artificial structures.

JOURNAL ARTICLE

Low KH, Hu T, Mohammed S, Tangorra J, Kovac M, Low KH, Hu T, Mohammed S, Tangorra J, Kovac M, Low KH, Hu T, Mohammed S, Tangorra J, Kovac M, Low KH, Hu T, Mohammed S, Tangorra J, Kovac M, Low KH, Hu T, Mohammed S, Tangorra J, Kovac Met al., 2015, Perspectives on biologically inspired hybrid and multi-modal locomotion PREFACE, BIOINSPIRATION & BIOMIMETICS, Vol: 10, Pages: 020301-020301, ISSN: 1748-3182

JOURNAL ARTICLE

Siddall R, Kovac M, Siddall R, Kovač Met al., 2015, A Water Jet Thruster for an Aquatic Micro Air Vehicle, IEEE International Conference on Robotics and Automation (ICRA), Publisher: IEEE COMPUTER SOC, Pages: 3979-3985, ISSN: 1050-4729

© 2015 IEEE. Water sampling with autonomous aerial vehicles has major applications in water monitoring and chemical accident response. Currently, no robot exists that is capable of both underwater locomotion and flight. This is principally because of the major design tradeoffs for operation in both water and air. A major challenge for such an aerial-aquatic mission is the transition to flight from the water. The use of high power density jet propulsion would allow short, impulsive take-offs by Micro Air Vehicles (MAVs). In this paper, we present a high power water jet propulsion system capable of launching a 70 gram vehicle to speeds of 11m/s in 0.3s, designed to allow waterborne take off for an Aquatic Micro Air Vehicle (AquaMAV). Jumps propelled by the jet are predicted to have a range of over 20m without gliding. Propulsion is driven by a miniaturised 57 bar gas release system, with many other applications in pneumatically actuated robots. We will show the development of a theoretical model to allow designs to be tailored to specific missions, and free flying operation of the jet.

CONFERENCE PAPER

Vidyasagar A, Zufferey J-C, Floreano D, Kovac M, Vidyasagar A, Zufferey J-C, Floreano D, Kovač M, Vidyasagar A, Zufferey JC, Floreano D, Kovač M, Vidyasagar A, Zufferey JC, Floreano D, Kovač M, Vidyasagar A, Zufferey J-C, Floreano D, Kovač M, Vidyasagar A, Zufferey J-C, Floreano D, Kovač Met al., 2015, Performance analysis of jump-gliding locomotion for miniature robotics, BIOINSPIRATION & BIOMIMETICS, Vol: 10, Pages: 025006-12, ISSN: 1748-3182

Recent work suggests that jumping locomotion in combination with a gliding phase can be used as an effective mobility principle in robotics. Compared to pure jumping without a gliding phase, the potential benefits of hybrid jump-gliding locomotion includes the ability to extend the distance travelled and reduce the potentially damaging impact forces upon landing. This publication evaluates the performance of jump-gliding locomotion and provides models for the analysis of the relevant dynamics of flight. It also defines a jump-gliding envelope that encompasses the range that can be achieved with jump-gliding robots and that can be used to evaluate the performance and improvement potential of jump-gliding robots. We present first a planar dynamic model and then a simplified closed form model, which allow for quantification of the distance travelled and the impact energy on landing. In order to validate the prediction of these models, we validate the model with experiments using a novel jump-gliding robot, named the 'EPFL jump-glider'. It has a mass of 16.5 g and is able to perform jumps from elevated positions, perform steered gliding flight, land safely and traverse on the ground by repetitive jumping. The experiments indicate that the developed jump-gliding model fits very well with the measured flight data using the EPFL jump-glider, confirming the benefits of jump-gliding locomotion to mobile robotics. The jump-glide envelope considerations indicate that the EPFL jump-glider, when traversing from a 2 m height, reaches 74.3% of optimal jump-gliding distance compared to pure jumping without a gliding phase which only reaches 33.4% of the optimal jump-gliding distance. Methods of further improving flight performance based on the models and inspiration from biological systems are presented providing mechanical design pathways to future jump-gliding robot designs.

JOURNAL ARTICLE

Hunt G, Mitzalis F, Alhinai T, Hooper PA, Kovac Met al., 2014, 3D Printing with Flying Robots, IEEE International Conference on Robotics and Automation (ICRA), Publisher: IEEE, Pages: 4493-4499, ISSN: 1050-4729

CONFERENCE PAPER

Kovac M, Kovač M, 2014, The Bioinspiration Design Paradigm: A Perspective for Soft Robotics, SOFT ROBOTICS, Vol: 1, Pages: 28-37, ISSN: 2169-5172

JOURNAL ARTICLE

Siddall R, Kovac M, Siddall R, Kovač M, Siddall R, Kovač M, Siddall R, Kovač Met al., 2014, Launching the AquaMAV: bioinspired design for aerial-aquatic robotic platforms, BIOINSPIRATION & BIOMIMETICS, Vol: 9, Pages: 031001-031001, ISSN: 1748-3182

Current Micro Aerial Vehicles (MAVs) are greatly limited by being able to operate in air only. Designing multimodal MAVs that can fly effectively, dive into the water and retake flight would enable applications of distributed water quality monitoring, search and rescue operations and underwater exploration. While some can land on water, no technologies are available that allow them to both dive and fly, due to dramatic design trade-offs that have to be solved for movement in both air and water and due to the absence of high-power propulsion systems that would allow a transition from underwater to air. In nature, several animals have evolved design solutions that enable them to successfully transition between water and air, and move in both media. Examples include flying fish, flying squid, diving birds and diving insects. In this paper, we review the biological literature on these multimodal animals and abstract their underlying design principles in the perspective of building a robotic equivalent, the Aquatic Micro Air Vehicle (AquaMAV). Building on the inspire-abstract-implement bioinspired design paradigm, we identify key adaptations from nature and designs from robotics. Based on this evaluation we propose key design principles for the design of successful aerial-aquatic robots, i.e. using a plunge diving strategy for water entry, folding wings for diving efficiency, water jet propulsion for water takeoff and hydrophobic surfaces for water shedding and dry flight. Further, we demonstrate the feasibility of the water jet propulsion by building a proof-of-concept water jet propulsion mechanism with a mass of 2.6 g that can propel itself up to 4.8 m high, corresponding to 72 times its size. This propulsion mechanism can be used for AquaMAV but also for other robotic applications where high-power density is of use, such as for jumping and swimming robots.

JOURNAL ARTICLE

Crall JD, Kovac M, Cornwall M, Wood RJ, Pierce NE, Combes SAet al., 2013, Shaping up: Aerodynamics and evolution of butterfly wing planform, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E42-E42, ISSN: 1540-7063

CONFERENCE PAPER

Wen L, Lauder G, Weaver JC, Kovac M, Wood RJet al., 2013, Hydrodynamics of Self-propelling Flexible Synthetic Shark Skin Membranes, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E223-E223, ISSN: 1540-7063

CONFERENCE PAPER

Kovac M, Vogt D, Ithier D, Smith M, Wood R, Kovac M, Vogt D, Ithier D, Smith M, Wood Ret al., 2012, Aerodynamic evaluation of four butterfly species for the design of flapping-gliding robotic insects, 25th IEEE\RSJ International Conference on Intelligent Robots and Systems (IROS), Publisher: IEEE, Pages: 1102-1109, ISSN: 2153-0858

Alternating gliding and active propulsion is a potentially energy saving strategy for small-scale flight. With the goal of finding optimal wing shapes for flapping-gliding robots we evaluate the quasi-steady aerodynamic performance of four butterfly species (Monarch (Danaus plexippus), the Orange Aeroplane (Pantoporia consimilis), the Glasswing (Acraea andromacha) and the Four-barred Swordtail (Protographium Ieosthenes)). We fabricate at-scale wing models based on measured wing shapes and vary the forewing angle in nine steps to account for the ability of the butterfly to change the relative orientation of its forewing and hindwing during flight. For comparison we include twelve non-biological planforms as performance benchmarks for the butterfly wing shapes. We then test these 48 wing models at 2m/s, 3.5m/s and 5m/s (Reynolds number between 2597 and 12632) in a low speed wind tunnel which allows lift and drag force measurements of centimeter-size wings. The results indicate that the forewing orientation which maximizes the wing span offers the best gliding performance and that overall the gliding ratios are highest at 3.5m/s. The wing shapes with the best gliding ratio are found in the Glasswing butterfly with a maximum of 6.26 which is very high compared to the gliding performance of similarly sized flying robots. The results from this study are important for the development of novel biologically-inspired flying micro robots as well as for biomechanics studies in biology. © 2012 IEEE.

CONFERENCE PAPER

Kovac M, Vogt D, Ithier D, Smith MJ, Wood RJet al., 2012, Experimental flight performance evaluation of forewing orientation in butterflies, Annual Meeting of the Society-for-Integrative-and-Comparative-Biology (SICB), Publisher: OXFORD UNIV PRESS INC, Pages: E96-E96, ISSN: 1540-7063

CONFERENCE PAPER

Kovač M, Wassim-Hraiz, Fauria O, Zufferey JC, Floreano Det al., 2011, The locomotion capabilities of the EPFL jumpglider: A hybrid jumping and gliding robot, Pages: 2249-2250

Recent work suggests that wings can be used to prolong the jumps of miniature jumping robots. However, no functional miniature jumping robot has been presented so far that can successfully apply this hybrid locomotion principle. In this video publication, we present the locomotion capabilities of the 'EPFL jumpglider', a miniature robot that can prolong its jumps using steered hybrid jumping and gliding locomotion over varied terrain. For example, it can safely descend from elevated positions such as stairs and buildings and propagate on ground with small jumps. © 2011 IEEE.

CONFERENCE PAPER

Kovač M, Wassim-Hraiz, Fauria O, Zufferey JC, Floreano Det al., 2011, The EPFL jumpglider: A hybrid jumping and gliding robot with rigid or folding wings, Pages: 1503-1508

Recent work suggests that wings can be used to prolong the jumps of miniature jumping robots. However, no functional miniature jumping robot has been presented so far that can successfully apply this hybrid locomotion principle. In this publication, we present the development and characterization of the 'EPFL jumpglider', a miniature robot that can prolong its jumps using steered hybrid jumping and gliding locomotion over varied terrain. For example, it can safely descend from elevated positions such as stairs and buildings and propagate on ground with small jumps. The publication presents a systematic evaluation of three biologically inspired wing folding mechanisms and a rigid wing design. Based on this evaluation, two wing designs are implemented and compared 1 . © 2011 IEEE.

CONFERENCE PAPER

Kovac M, Schlegel M, Zufferey J-C, Floreano D, Kovač M, Schlegel M, Zufferey JC, Floreano D, Kovač M, Schlegel M, Zufferey J-C, Floreano D, Kovac M, Schlegel M, Zufferey J-C, Floreano Det al., 2010, Steerable miniature jumping robot, AUTONOMOUS ROBOTS, Vol: 28, Pages: 295-306, ISSN: 0929-5593

Jumping is used in nature by many small animals to locomote in cluttered environments or in rough terrain. It offers small systems the benefit of overcoming relatively large obstacles at a low energetic cost. In order to be able to perform repetitive jumps in a given direction, it is important to be able to upright after landing, steer and jump again. In this article, we review and evaluate the uprighting and steering principles of existing jumping robots and present a novel spherical robot with a mass of 14 g and a size of 18 cm that can jump up to 62 cm at a take-off angle of 75°, recover passively after landing, orient itself, and jump again. We describe its design details and fabrication methods, characterize its jumping performance, and demonstrate the remote controlled prototype repetitively moving over an obstacle course where it has to climb stairs and go through a window. (See videos 1-4 in the electronic supplementary material.) © 2009 Springer Science+Business Media, LLC.

JOURNAL ARTICLE

Kovac M, Schlegel M, Zufferey J-C, Floreano D, Kovač M, Schlegel M, Zufferey JC, Floreano Det al., 2009, A Miniature Jumping Robot with Self-Recovery Capabilities, IEEE RSJ International Conference on Intelligent Robots and Systems, Publisher: IEEE, Pages: 583-588

In nature, many animals are able to jump, upright themselves after landing and jump again. This allows them to move in unstructured and rough terrain. As a further development of our previously presented 7g jumping robot, we consider various mechanisms enabling it to recover and upright after landing and jump again. After a weighted evaluation of these different solutions, we present a spherical system with a mass of 9.8g and a diameter of 12cm that is able to jump, upright itself after landing and jump again. In order to do so autonomously, it has a control unit and sensors to detect its orientation and spring charging state. With its current configuration it can overcome obstacles of 76cm at a take-off angle of 75°. © 2009 IEEE.

CONFERENCE PAPER

Kovač M, Germann J, Hürzeler C, Siegwart RY, Floreano Det al., 2009, A perching mechanism for micro aerial vehicles, Journal of Micro-Nano Mechatronics, Vol: 5, Pages: 77-91, ISSN: 1865-3928

JOURNAL ARTICLE

Kovac M, Fuchs M, Guignard A, Zufferey J-C, Floreano D, Kovač M, Fuchs M, Guignard A, Zufferey JC, Floreano Det al., 2008, A miniature 7g jumping robot, IEEE International Conference on Robotics and Automation, Publisher: IEEE, Pages: 373-378, ISSN: 1050-4729

Jumping can be a very efficient mode of locomotion for small robots to overcome large obstacles and travel in natural, rough terrain. In this paper we present the development and characterization of a novel 5cm, 7g jumping robot. It can jump obstacles more than 27 times its own size and outperforms existing jumping robots by one order of magnitude with respect to jump height per weight and jump height per size. It employs elastic elements in a four bar linkage leg system to allow for very powerful jumps and adjustment of the jumping force, take-off angle and force profile during the acceleration phase. ©2008 IEEE.

CONFERENCE PAPER

Kovac M, Guignard A, Nicoud J-D, Zufferey J-C, Floreano D, Kovač M, Guignard A, Nicoud JD, Zufferey JC, Floreano D, Kovac M, Guignard A, Nicoud J-D, Zufferey J-C, Floreano Det al., 2007, A 1.5g SMA-actuated microglider looking for the light, IEEE International Conference on Robotics and Automation, Publisher: IEEE, Pages: 367-372, ISSN: 1050-4729

Unpowered flight can be used in microrobotics to overcome ground obstacles and to increase the traveling distance per energy unit. In order to explore the potential of goal-directed gliding in the domain of miniature robotics, we developed a 22cm microglider weighing a mere 1.5g and flying at around 1.5m/s. It is equipped with sensors and electronics to achieve phototaxis, which can be seen as a minimal level of control autonomy. A novel 0.2g Shape Memory Alloy (SMA) actuator for steering control has been specifically designed and integrated to keep the overall weight as low as possible. In order to characterize autonomous operation of this robot, we developed an experimental setup consisting of a launching device and a light source positioned Im below and 4m away with varying angles with respect to the launching direction. Statistical analysis of 36 autonomous flights demonstrate its flight and phototaxis efficiency. © 2007 IEEE.

CONFERENCE PAPER

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