Mirko Kovac

A miniature 7g jumping robot

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 5 cm, 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.

A miniature jumping robot with self-recovery capabilities

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°.

The EPFL jumpglider: A hybrid jumping and gliding robot with rigid or folding wings

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 compared1.

3D printing with flying robots

Extensive work has been devoted recently to the development of 3D printing or additive layer manufacturing technologies, as well as to the field of flying robots. However, to the best of the authors7 knowledge, no robotic prototype has been presented so far that combines additive layer manufacturing techniques with aerial robotics. In this paper, we examine the feasibility of such a hybrid approach and present the design and characterisation of an aerial 3D printer; a flying robot capable of depositing polyurethane expanding foam in mid-flight. We evaluate various printing materials and describe the design and integration of a lightweight printing module onto a quadcopter, as well as discuss the limitations and opportunities for aerial construction with flying robots using the developed technologies. Potential applications include ad-hoc construction of first response structures in search and rescue scenarios, printing structures to bridge gaps in discontinuous terrain, and repairing damaged surfaces in areas that are inaccessible by ground-based robots.

Towards a Self-Deploying and Gliding Robot

Strategies for hybrid locomotion such as jumping and gliding are used in nature by many different animals for traveling over rough terrain. This combination of locomotion modes also allows small robots to overcome relatively large obstacles at a minimal energetic cost compared to wheeled or flying robots. In this chapter we describe the development of a novel palm-sized robot of 10 g that is able to autonomously deploy itself from ground or walls, open its wings, recover in mid-air, and subsequently perform goal-directed gliding. In particular, we focus on the subsystems that will in the future be integrated such as a 1.5 g microglider that can perform phototaxis; a 4.5 g, bat-inspired, wing-folding mechanism that can unfold in only 50 ms; and a locust-inspired, 7 g robot that can jump more than 27 times its own height. We also review the relevance of jumping and gliding for living and robotic systems and we highlight future directions for the realization of a fully integrated robot.

A 1.5g SMA-actuated Microglider looking for the Light

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 lm 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.

Learning from nature how to land aerial robots

Smaller robots can use mechanical intelligence to simplify the task of perching on a target 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.

Wind and water tunnel testing of a morphing aquatic micro air vehicle

Aerial robots capable of locomotion in both air and water would enable novel mission profiles in complex environments, such as water sampling after floods or underwater structural inspections. The design of such a vehicle is challenging because it implies significant propulsive and structural design trade-offs for operation in both fluids. In this paper, we present a unique Aquatic Micro Air Vehicle (AquaMAV), which uses a reconfigurable wing to dive into the water from flight, inspired by the plunge diving strategy of water diving birds in the family Sulidae. The vehicles performance is investigated in wind and water tunnel experiments, from which we develop a planar trajectory model. This model is used to predict the dive behaviour of the AquaMAV, and investigate the efficacy of passive dives initiated by wing folding as a means of water entry. The paper also includes first field tests of the AquaMAV prototype where the folding wings are used to initiate a plunge dive.

Multi-stage micro rockets for robotic insects.

One of the main challenges for sustained flight of current aerial micro robots is the low energy density available from common power sources. In this paper we propose solid rocket fuel powered micro thrusters as a high energy density actuation method for aerial micro robots. In a multi stage configuration these thrusters can be used for intermittent flight which can decrease the energetic cost of locomotion. In particular we focus on the fabrication method and characterization of multistage micro thrusters with a diameter of 3mm and 6.4mm. We demonstrate a sustained and repeatable thrust force of up to 35mN for a duration of up to 42s and a multi-stage designs with a time delay of up to 4.7s between the propulsion phases. Furthermore, we present a take-off trajectory of a 10cm rocket glider with an integrated micro thruster as propulsion mechanism showing that the technologies developed can be used to successfully power micro robots in flight. Future work will focus on control and flight dynamics of micro thruster powered gliders. Wider applications of similar thrusters can include other robotic applications where low weight and high force is important such as for jumping or running robots.

A water jet thruster for an aquatic micro air vehicle

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.