Body Lift and Drag for a Legged Millirobot in Compliant Beam Environment

Much current study of legged locomotion has rightly focused on foot traction forces, including on granular media. Future legged millirobots will need to go through terrain, such as brush or other vegetation, where the body contact forces significantly affect locomotion. In this work, a (previously developed) low-cost 6-axis force/torque sensing shell is used to measure the interaction forces between a hexapedal millirobot and a set of compliant beams, which act as a surrogate for a densely cluttered environment. Experiments with a VelociRoACH robotic platform are used to measure lift and drag forces on the tactile shell, where negative lift forces can increase traction, even while drag forces increase. The drag energy and specific resistance required to pass through dense terrains can be measured. Furthermore, some contact between the robot and the compliant beams can lower specific resistance of locomotion. For small, light-weight legged robots in the beam environment, the body motion depends on both leg-ground and body-beam forces. A shell-shape which reduces drag but increases negative lift, such as the half-ellipsoid used, is suggested to be advantageous for robot locomotion in this type of environment.Comment: First three authors contributed equally. Accepted to ICRA 201

바퀴벌레 모사 소형 등반 플랫폼의 설계 및 제작

학위논문 (석사)-- 서울대학교 대학원 : 기계항공공학부, 2016. 2. 조규진.Small mobile robots are required in rescue missions and military task. Milli-scale robots can pass a narrow gap within a collapsed building and carry out the reconnaissance mission without being detected by enemies. The issue of a small robot is that it might get stuck in obstacles that are bigger than itself. The ability to overcome obstacles is important to small robot. Climbing can make it overcome tens of times larger than itself. In this research, three principles of cockroach climbing are defined and integrated with planar mechanism. Small cockroach can rapidly climb vertical walls with a rough surface. First principle inspired by a cockroach is stable walking with an alternating tripod gait. This gait makes stable locomotion possible thanks to the support of at least three feet. Planar transmission using a single actuator is designed for alternating tripod gait. Second principle is reducing the impact during the attachment process. Cockroach use compliant foot called tarsus structure. This can reduce the amount of normal reaction force during the interaction between spines and surface. Compliant foot are modelled based on Pseudo-rigid-body model (PRBM). Hind leg is designed to reduce the pitch-back moment at the front limb without tail. Third principle is the phase overlap. Phase overlap is an overlapping of the set of feet on the ground. Cockroaches have the phase overlap during climbing at 5body-lengths/sec. Planar quick-return leg is designed to have the phase overlap during alternating tripod gait. In this research, three key principles are extracted and integrated with planar fabrication for a small climbing robot. A new method using laminating film and fabric is developed for fast prototyping as well as for high structural strength. Fabricated robot is 8.5cm long and 6g in weight. This robot can climb on three different kinds of surfaces at around 0.1body-lengths/sec. The research suggest the possibility that a new approach based on biomimetics and planar design can solve the scale issue of small mobile robots thanks to a novel and simple mechanism.Chapter 1 Introduction 1 Chapter 2 The Principles of Cockroach Climbing 4 2.1 Alternating Tripod Gait 4 2.2 Reducing the Impact of Attachment 6 2.3 Phase Overlap 7 Chapter 3 Bio-inspired Design 8 3.1 Transmission using a Single Actuator 8 3.2 Compliant Foot and Hind Leg 9 3.3 Quick-return Leg 14 Chapter 4 Results 21 4.1 Planar Fabrication 21 4.2 Experimental Results 24 Chapter 5 Conclusion 26 Bibliography 28 국문 초록 33Maste

Slippery paints:Eco-friendly coatings that cause ants to slip

Many insects are considered to be pests and can be serious threats to buildings. Insecticides represent an effective way to control pest insects but are harmful to the environment. As an eco-friendlier alternative, we have formulated waterborne, organic paints which provided a slippery physical barrier for leafcutter ants (Atta cephalotes) on vertical surfaces. Different paints were produced by varying the Pigment Volume Concentration (PVC) and amount of TiO2 and CaCO3 particles, and characterised in terms of contact angles, surface roughness and scrub resistance. The paints' slipperiness for A. cephalotes ants was evaluated in climbing tests on vertical paint panels (by recording the percentage of fallen ants). Two main factors reduced the insects' attachment to vertical paint surfaces: (1) the PVC: in paints above a critical PVC, more loose particles detach from the coating and thereby reduce insect attachment; and (2) the type, dimensions and shape of solid particles: CaCO3 particles detach more easily from the paint than TiO2, probably due to their larger size and platelet shape. Paints formulated at PVC 70 and containing 20 wt% CaCO3 showed the best performance in terms of slipperiness, as well as providing good scrub resistance

Advances in Bio-Inspired Robots

This book covers three major topics, specifically Biomimetic Robot Design, Mechanical System Design from Bio-Inspiration, and Bio-Inspired Analysis on A Mechanical System. The Biomimetic Robot Design part introduces research on flexible jumping robots, snake robots, and small flying robots, while the Mechanical System Design from Bio-Inspiration part introduces Bioinspired Divide-and-Conquer Design Methodology, Modular Cable-Driven Human-Like Robotic Arm andWall-Climbing Robot. Finally, in the Bio-Inspired Analysis on A Mechanical System part, research contents on the control strategy of Surgical Assistant Robot, modeling of Underwater Thruster, and optimization of Humanoid Robot are introduced

Slippery paints: Eco-friendly coatings that cause ants to slip

Many insects are considered to be pests and can be serious threats to buildings. Insecticides represent an effective way to control pest insects but are harmful to the environment. As an eco-friendlier alternative, we have formulated waterborne, organic paints which provided a slippery physical barrier for leafcutter ants (Atta cephalotes) on vertical surfaces. Different paints were produced by varying the Pigment Volume Concentration (PVC) and amount of TiO2 and CaCO3 particles, and characterised in terms of contact angles, surface roughness and scrub resistance. The paints’ slipperiness for A. cephalotes ants was evaluated in climbing tests on vertical paint panels (by recording the percentage of fallen ants). Two main factors reduced the insects’ attachment to vertical paint surfaces: (1) the PVC: in paints above a critical PVC, more loose particles detach from the coating and thereby reduce insect attachment; and (2) the type, dimensions and shape of solid particles: CaCO3 particles detach more easily from the paint than TiO2, probably due to their larger size and platelet shape. Paints formulated at PVC 70 and containing 20 wt% CaCO3 showed the best performance in terms of slipperiness, as well as providing good scrub resistance.</p

Biological adhesion in wet environments: adaptations and mechanisms

Physiochemical conditions in water are fundamentally different to those in air; hence, organisms require special adaptations to adhere in wet environments. In my thesis, I have investigated three study systems to elucidate mechanisms for adhesion under wet conditions. In Chapters 2 and 3, I explore an aquatic insect (Diptera: Blephariceridae) that uses suction organs to attach to rocks in raging alpine torrents. Suction-based attachment is driven by physical processes requiring a pressure difference and a seal to maintain it. Through my investigations, I have identified several key principles for biological suction attachments to wet and rough surfaces. Using three-dimensional reconstructions of blepharicerid suction organs and in vivo visualisation of the adhesive contact zone, I found several internal and external morphological adaptations that are important for strong adhesion under water. Moreover, I characterised a mechanism for rapid detachment which is the first detailed account of an actively controlled detachment system in biological suction organs. In Chapter 4, I investigate the contribution of physical and chemical mechanisms to the powerful attachment of common limpets (Patella vulgata) to rocks in the intertidal zone. I demonstrate that suction is not the primary contributor to their attachment forces; rather, it is their adhesive pedal mucus that is responsible. This adhesive mucus comprises of a complex mixture of glycans and proteins, many of which share homology with adhesive secretions from other marine invertebrates, such as sea stars, sea anemones, and flatworms. In Chapters 5 and 6, I study the physical and chemical properties of sticky secretions from carnivorous pitcher plants (Nepenthes) that help to capture, retain, and digest insects. I show that the viscoelastic pitcher fluid readily adheres to but not easily dewets from insect cuticle, and forms stable filaments as the insect attempts to escape that require significant work to overcome. In addition, the surface tension is reduced in pitcher fluid compared to water, making insects sink more easily into the former and facilitating further wetting of the cuticle. Chemical characterisation of the pitcher fluid revealed that its sticky filamentous property is caused by a polysaccharide with a glucurono-mannan backbone structure, which is chemically stable and contains carboxylic groups for strong interactions. Glucurono-mannan are an understudied group of plant polysaccharides that are present in mucilaginous secretions from across the plant kingdom, including sticky capture fluids from other carnivorous plants. My findings show that pitcher plant fluid can be used as a study system for future investigations into the origins and functional role of glucurono-mannan in carnivorous plants. In summary, my thesis has identified novel adaptations and principles for biological adhesion under wet conditions using three selected study systems, hence expanding our understanding of the underlying physical and chemical mechanisms and providing inspiration for biomimetic adhesives with improved performance in wet environments.EU Horizon 2020 under Marie Skłodowska-Curie grant agreement No. 64286

4D Printing Dielectric Elastomer Actuator Based Soft Robots

4D printing is an emerging technology that prints 3D structural smart materials that can respond to external stimuli and change shape over time. 4D printing represents a major manufacturing paradigm shift from single-function static structures to dynamic structures with highly integrated functionalities. Direct printing of dynamic structures can provide great benefits (e.g., design freedom, low material cost) to a wide variety of applications, such as sensors and actuators, and robotics. Soft robotics is a new direction of robotics in which hard and rigid components are replaced by soft and flexible materials to mimic mechanisms that works in living creatures, which are crucial for dealing with uncertain and dynamic tasks. However, little research on direct printing of soft robotics has been reported. Due to the short history of 4D printing, only a few smart materials have been successfully 4D printed, such as shape memory and thermo-responsive polymers, which have relatively small actuation strains (up to ~8%). In order to produce the large motion, dielectric elastomer actuator (DEA), a sheet of elastomer sandwiched between two compliant electrodes and known as artificial muscle for its high elastic energy density and capability of producing large strains (~200%), is chosen as the actuator for soft robotics. Little research on 3D printing silicone DEA soft robotics has been done in the literature. Thus, this thesis is motivated by applying the advantages in 3D printing fabrication methods to develop DEA soft robotics. The ultimate research goal is to demonstrate fully printed DEA soft robots with large actuation. In Chapter 1, the research background of soft robotics and DEAs are introduced, as well as 3D printing technologies. Chapter 2 reports the rules of selecting potentially good silicone candidates and the printing process with printed material characterizations. Chapter 3 studies the effects of pre-strain condition on silicone material properties and the performance of DEA configurations, in order to obtain large actuation strain. In Chapter 4, two facial soft robots are designed to achieve facial expressions as judged by a smiling lip and expanding pupils based on DEA actuation. Conclusions and future developments are given in chapter 5 and 6, respectively

Biomimetic Based Applications

The interaction between cells, tissues and biomaterial surfaces are the highlights of the book "Biomimetic Based Applications". In this regard the effect of nanostructures and nanotopographies and their effect on the development of a new generation of biomaterials including advanced multifunctional scaffolds for tissue engineering are discussed. The 2 volumes contain articles that cover a wide spectrum of subject matter such as different aspects of the development of scaffolds and coatings with enhanced performance and bioactivity, including investigations of material surface-cell interactions

Design of novel adaptive magnetic adhesion mechanism for climbing robots in ferric structures

The work presented in this thesis proposes a novel adaptive magnetic adhesion mechanism that can be implemented in most locomotion mechanisms employed in climbing robots for ferric structures. This novel mechanism has the capability to switch OFF and ON its magnetic adhesion with minimal power consumption, and remain at either state after the excitation is removed. Furthermore, the proposed adhesion mechanism has the ability to adapt the strength of the adhesive force to a desired magnitude. These capabilities make the proposed adhesion mechanism a potential solution in the field of wall climbing robots. The novel contributions of the proposed mechanism include the switching of the adhesive force, selectivity of the adhesive force magnitude; determination of the parameters that have an impact in the final adhesive force. Finally, a final prototype is constructed with customised components and it is subject to a set of simulations and experiments to validate its performance