22,044 research outputs found
Investigation and development of a flexible gripper with adaptable finger geometry
Das zuverlÀssige und schonende Greifen ist ein Hauptanliegen bei der
Entwicklung von neuartigen Greifvorrichtungen. Je gröĂer die KontaktflĂ€che
zwischen dem Greifer und dem Greifobjekt ist, desto schonender und
zuverlÀssiger ist der Greifvorgang. Um dieses Ziel zu erreichen wurden in den
letzten Jahrzehnten zahlreiche Untersuchungen zu adaptiven passiven Greifern
durchgefĂŒhrt. Ein neuer Forschungszweig im Bereich selbstadaptiver Greifer sind
Greifer mit nachgiebigen blattfederartigen Greifelementen (Greiferfinger) Die
Funktionsweise basiert auf dem elastischen Ausknicken der Greifelemente
infolge einer translatorische Antriebsbewegung
Die vorliegende Arbeit konzentriert sich auf die Verbesserung des Greifvorgangs,
indem die KontaktlÀnge zwischen den blattfederartigen Greiferfingern und dem
zu greifenden Objekt deutlich erhöht wird. Um diese Aufgabenstellung zu lösen,
muss eine geeignete Greifergeometrie fĂŒr ein gegebenes Greifobjekt berechnet
werden.
Die gezielte Berechnung der erfoderlichen Greifergeometrie fĂŒr ein bekanntes
Greifobjekt ist nicht möglich. Daher wurde als Lösungsansatz die umkehrte
Richtung gewĂ€hlt. FĂŒr eine definierte Greifgeometrie wird die Gestalt des dazu
passenden âidealenâ Greifobjektes ermittelt und anschlieĂend mit der Gestalt zu
greifenden Objektes verglichen. Bei Gestaltabweichungen wird die
Greifergeometrie iterative verÀndert, bis seine geeignete Greifergeometrie
gefunden wurde. Im Rahmen der vorliegenden Arbeit wird zunÀchst die
Ermittlung des âidealenâ Greifobjektes behandelt. Es wurde ein Algorithmus
entwickelt, der fĂŒr eine vorgegebene Greifergeometrie die Gestalt eines runden
bzw. elliptischen Objektes ermittelt. Der Algorithmus verwendet als Eingabedaten
die Biegelinien der elastisch ausgeknickten Greiffinger unter BerĂŒcksichtigung
unterschiedlicher Randbedingungen. Als Ausgabedaten liefert der Algorithmus
die Gestalt des passenden Greifobjektes zurĂŒck. FĂŒr quadratische bzw.
rechteckige sowie fĂŒr dreieckige Objekte wurden unterschiedliche
Greifgeometrien untersucht. AuĂerdem wird fĂŒr quadratische und rechteckige
Objekte das Lösungskonzept fĂŒr die Entwicklung eines weiteren Algorithmus
beschrieben.
In Kapitel 1 wird eine Klassifizierung von Greifern basierend auf der
AnpassungsfÀhigkeit vorgestellt. In Kapitel 2 werden Lösungskonzepte, Modelle
und Theorien vorgestellt. In Kapitel 3 werden Ablaufdiagramme der Algorithmen
dargestellt. In Kapitel 4 wird die Entwicklung des Algorithmus fĂŒr elliptische
Objekte und deren Betriebsmodi beschrieben. In Kapitel 5 werden
Greifgeometrien fĂŒr quadratische bzw. Rechteckige sowie fĂŒr dreieckige Objekte
analysiert und die Ideen eines Algorithmus fĂŒr quadratisch bzw. rechteckige
Objekte beschrieben. In Kapitel 6 wird ein kurzer Ăberblick ĂŒber die zukĂŒnftige
Arbeiten.Reliable and gentle gripping is a major concern in the development of new
gripping devices. The larger contact surface between the gripper and the gripping
object, the gentler and more reliable the gripping process. In order to achieve this
goal, further investigations on adaptive passive grippers have been carried out in
the recent decades. A new branch of research in the field of self-adaptive grippers
are compliant leaf-spring-like gripping elements (gripper fingers). Its mode of
operation is based on the elastic buckling of the gripping elements as a result of
a translatory drive movement.
The present work focuses on improving the gripping process by increasing
significantly the contact length between the compliant leaf-spring-like gripper
fingers and the object to be gripped. In order to solve this task, a suitable gripper
geometry for a given gripping object should be calculated
The specific calculation of the required gripper geometry for a known gripping
object is not possible; therefore, this work aims in the opposite direction. For a
defined gripping geometry, the shape of the matching âidealâ gripping object is
determined and then compared with the desired object to be gripped. In case of
a deviation in the size, the gripper geometry is iteratively changed until its suitable
gripper geometry has been found. In the present work, the determination of the
âidealâ gripping object is the first task to deal with. An algorithm has been
developed to determine the shape of a round-elliptical object for a given gripper
geometry. The algorithm uses as data input the bend lines of the compliant twogripper
finger under different boundary conditions. As data output, the algorithm
returns the shape of the matching gripping object. For square-rectangular and
triangular objects, different gripping geometries have been investigated.
Furthermore, for square-rectangular objects, solution concepts for the
development of an algorithm is described.
In chapter 1, a classification based on adaptability is presented. In chapter 2,
solution concepts, models and theories involved are introduced. In chapter 3,
process flow diagrams of the algorithms are presented. In chapter 4, the
development of the algorithm for elliptical objects and its operation modes are
described. In chapter 5, gripping geometries for square-rectangular and triangular
objects are analysed and the ideas of an algorithm for square-rectangular objects
are described. In chapter 6, a brief overview of the futur work is commented.Tesi
SCALER: Versatile Multi-Limbed Robot for Free-Climbing in Extreme Terrains
This paper presents SCALER, a versatile free-climbing multi-limbed robot that
is designed to achieve tightly coupled simultaneous locomotion and dexterous
grasping. Although existing quadruped-limbed robots have shown impressive
dexterous skills such as object manipulation, it is essential to balance
power-intensive locomotion and dexterous grasping capabilities. We design a
torso linkage and a parallel-serial limb to meet such conflicting skills that
pose unique challenges in the hardware designs. SCALER employs underactuated
two-fingered GOAT grippers that can mechanically adapt and offer 7 modes of
grasping, enabling SCALER to traverse extreme terrains with multi-modal
grasping strategies. We study the whole-body approach, where SCALER uses its
body and limbs to generate additional forces for stable grasping with
environments, further enhancing versatility. Furthermore, we improve the GOAT
gripper actuation speed to realize more dynamic climbing in a closed-loop
control fashion. With these proposed technologies, SCALER can traverse
vertical, overhang, upside-down, slippery terrains, and bouldering walls with
non-convex-shaped climbing holds under the Earth's gravity
Inertial Load Compensation by a Model Spinal Circuit During Single Joint Movement
Office of Naval Research (N00014-92-J-1309); CONACYT (Mexico) (63462
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A highly-underactuated robotic hand with force and joint angle sensors
This paper describes a novel underactuated robotic hand design. The hand is highly underactuated as it contains three fingers with three joints each controlled by a single motor. One of the fingers ("thumb") can also be rotated about the base of the hand, yielding a total of two controllable degrees-of-freedom. A key component of the design is the addition of position and tactile sensors which provide precise angle feedback and binary force feedback. Our mechanical design can be analyzed theoretically to predict contact forces as well as hand position given a particular object shape
Systematic object-invariant in-hand manipulation via reconfigurable underactuatuation: introducing the RUTH gripper
We introduce a reconfigurable underactuated robot hand able to perform systematic prehensile in-hand manipulations regardless of object size or shape. The hand utilises a two-degree-of-freedom five-bar linkage as the palm of the gripper, with three three-phalanx underactuated fingersâjointly controlled by a single actuatorâconnected to the mobile revolute joints of the palm. Three actuators are used in the robot hand system in total, one for controlling the force exerted on objects by the fingers through an underactuated tendon system, and two for changing the configuration of the palm and thus the positioning of the fingers. This novel layout allows decoupling grasping and manipulation, facilitating the planning and execution of in-hand manipulation operations. The reconfigurable palm provides the hand with a large grasping versatility, and allows easy computation of a map between task space and joint space for manipulation based on distance-based linkage kinematics. The motion of objects of different sizes and shapes from one pose to another is then straightforward and systematic, provided the objects are kept grasped.This is guaranteed independently and passively by the underactuated fingers using a custom tendon routing method, which allows no tendon length variation when the relative finger base positions change with palm reconfigurations. We analyse the theoretical grasping workspace and grasping and manipulation capability of the hand, present algorithms forcomputing the manipulation map and in-hand manipulation planning, and evaluate all these experimentally. Numericaland empirical results of several manipulation trajectories with objects of different size and shape clearly demonstrate the viability of the proposed concept
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Land re-use, complexity and actor-networks: a framework for research
This paper will present a conceptual framework for the examination of land redevelopment based on a complex systems/networks approach. As Alvin Toffler insightfully noted, modern scientific enquiry has become exceptionally good at splitting problems into pieces but has forgotten how to put the pieces back together. Twenty-five years after his remarks, governments and corporations faced with the requirements of sustainability are struggling to promote an âintegratedâ or âholisticâ approach to tackling problems. Despite the talk, both practice and research provide few platforms that allow for âjoined upâ thinking and action. With socio-economic phenomena, such as land redevelopment, promising prospects open up when we assume that their constituents can make up complex systems whose emergent properties are more than the sum of the parts and whose behaviour is inherently difficult to predict. A review of previous research shows that it has mainly focused on idealised, âmechanicalâ views of property development processes that fail to recognise in full the relationships between actors, the structures created and their emergent qualities. When reality failed to live up to the expectations of these theoretical constructs then somebody had to be blamed for it: planners, developers, politicians. However, from a âsyntheticâ point of view the agents and networks involved in property development can be seen as constituents of structures that perform complex processes. These structures interact, forming new more complex structures and networks. Redevelopment then can be conceptualised as a process of transformation: a complex system, a âdissipativeâ structure involving developers, planners, landowners, state agencies etc., unlocks the potential of previously used sites, transforms space towards a higher order of complexity and âconsumesâ but also âcreatesâ different forms of capital in the process. Analysis of network relations point toward the âdualismâ of structure and agency in these processes of system transformation and change. Insights from actor network theory can be conjoined with notions of complexity and chaos to build an understanding of the ways in which actors actively seek to shape these structures and systems, whilst at the same time are recursively shaped by them in their strategies and actions.
This approach transcends the blame game and allows for inter-disciplinary inputs to be placed within a broader explanatory framework that does away with many past dichotomies. Better understanding of the interactions between actors and the emergent qualities of the networks they form can improve our comprehension of the complex socio-spatial phenomena that redevelopment comprises. The insights that this framework provides when applied in UK institutional investment into redevelopment are considered to be significant
Magnetorheological Variable Stiffness Robot Legs for Improved Locomotion Performance
In an increasingly automated world, interest in the field of robotics is surging, with an exciting branch of this area being legged robotics. These biologically inspired robots have leg-like limbs which enable locomotion, suited to challenging terrains which wheels struggle to conquer. While it has been quite some time since the idea of a legged machine was first made a reality, this technology has been modernised with compliant legs to improve locomotion performance. Recently, developments in biological science have uncovered that humans and animals alike control their leg stiffness, adapting to different locomotion conditions. Furthermore, as these studies highlighted potential to improve upon the existing compliant-legged robots, modern robot designs have seen implementation of variable stiffness into their legs. As this is quite a new concept, few works have been published which document such designs, and hence much potential exists for research in this area. As a promising technology which can achieve variable stiffness, magnetorheological (MR) smart materials may be ideal for use in robot legs. In particular, recent advances have enabled the use of MR fluid (MRF) to facilitate variable stiffness in a robust manner, in contrast to MR elastomer (MRE).
Developed in this thesis is what was at the time the first rotary MR damper variable stiffness mechanism. This is proposed by the author for use within a robot leg to enable rapid stiffness control during locomotion. Based its mechanics and actuation, the leg is termed the magnetorheological variable stiffness actuator leg mark-I (MRVSAL-I). The leg, with a C-shaped morphology suited to torque actuation is first characterised through linear compression testing, demonstrating a wide range of stiffness variation. This variation is in response to an increase in electric current supplied to the internal electromagnetic coils of the MR damper. A limited degrees-of-freedom (DOF) bipedal locomotion platform is designed and manufactured to study the locomotion performance resulting from the variable stiffness leg. It is established that optimal stiffness tuning of the leg could achieve reduced mechanical cost of transport (MCOT), thereby improving locomotion performance. Despite the advancements to locomotion demonstrated, some design issues with the leg required further optimisation and a new leg morphology
Bioinspired design of a landing system with soft shock absorbers for autonomous aerial robots
One of the main challenges for autonomous aerial robots is to land safely on a target position on varied surface structures in realâworld 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 inspireâabstractâimplement 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 oneâdegreeâofâfreedom 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 2âm/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 crossâdisciplinary approach in vehicle control and navigation is combined with soft technologies, enabled with adaptive morphology
Bioinspired design of a landing system with soft shock absorbers for autonomous aerial robots
© 2018 Wiley Periodicals Inc. 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 inspireâabstractâimplement 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
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