59 research outputs found

    Pneumatic variable stiffness soft robot end effectors

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    Traditionally, robots have been formed from heavy rigid materials and have used stiff actuator technologies. This means they are not well suited to operation near humans due to the associated high risk of injury, should a collision occur. Additionally, rigid robots are not well suited to operation in an unstructured environment where they may come into contact with obstacles. Furthermore, traditional stiff robots can struggle to grasp delicate objects as high localised forces can damage the item being held. The relatively new field of soft robotics is inspired by nature, particularly animals which do not have skeletons but which still have the ability to move and grasp in a skilful manner. Soft robotics seeks to replicate this ability through the use of new actuation technologies and materials. This research presents the design of a variable stiffness, soft, three-fingered dexterous gripper. The gripper uses contractor pneumatic muscles to control the motion of soft fingers. The soft nature of the gripper means it can deform if it collides with obstacles, and because grasping forces are spread over a larger area the chance of damaging the object being held is reduced. The gripper has the ability to vary its stiffness depending upon how it is to be used, and in this regard two methods of varying the stiffness are explored. In the first method, the finger is formed from an extensor muscle which acts antagonistically against the contractor muscles. Increasing the total pressure in the system increases the stiffness of the fingers. The second approach uses granular jamming to vary the stiffness of the actual finger structure. This thesis explores the behaviour of both extensor and contractor pneumatic muscles and develops a new simplified mathematical model of the actuator’s behaviour. The two methods of stiffness variation are then assessed experimentally. A number of multi-fingered grippers are then designed and their kinematics determined before prototypes are presented. Control of the grippers was then explored, along with the ability to adjust the stiffness of the grasp

    DEVELOPMENT OF A ROBOTIC EXOSKELETON SYSTEM FOR GAIT REHABILITATION

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    Ph.DDOCTOR OF PHILOSOPH

    Shape memory polymers as direct contact dry adhesives for transfer printing and general use

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    For most diminutive life on Earth, control over external adhesive forces is crucial for survival. As humans, we pay little notice because at our scale inertial forces typically overwhelm adhesive forces by a wide margin. Nonetheless, the study and development of dry adhesives, which rely on ubiquitous intermolecular attractions to repeatedly form and break attachment to their adherends, have garnered substantial interest in recent decades. High performance artificial dry adhesives may unlock the door for many exciting new technologies from nanoscale manufacturing to wall climbing robots, but thus far the challenges have proven substantial and few successful commercial applications have come to fruition. This dissertation represents an initial investigation into the benefits and potential limitations of developing shape memory polymer (SMP)-based dry adhesives. Prior to the presentation of experimental results, a review of the current state of dry adhesive knowledge including both theory, observations of the natural world, and lessons learned by other researchers in their attempts to develop a wide variety of synthetic dry adhesives is provided. It is concluded that dry adhesives fundamentally function through careful control of elastic energy, an idea that is very well suited to explore using SMPs which offer a large change in compliance across their thermal transition temperature. Thermoset epoxy SMPs are identified as an ideal choice for the investigation due to their mechanical strength, chemical resistance, manufacturability and convenient glass transitions among other features. The dry adhesive performance of a selected SMP is first evaluated for the purpose of microscale transfer printing, wherein micro-objects are assembled through precise control of adhesive surface forces. Significant benefits over existing solutions in terms of maximum adhesive strength during loading (~7 MPa), minimum strength for release (~0 MPa), and process versatility are confirmed, culminating in demonstrations of several challenging assemblies. The increase in adhesive strength is explained by invoking arguments from linear fracture mechanics and considering the dramatic compliance change experienced by the SMP between bond and load events. Advanced methods of heating and meaningful steps towards commercial-scale parallel printing processes are demonstrated. The suitability of SMP for larger-scale applications is considered next. Strength rivaling or exceeding known alternatives is demonstrated, showing adhesion exceeding 2 MPa for 6 mm diameter adhesives while retaining excellent releasability through the use of microstructuring. A method of internally heating the SMP by adding conductive carbon nanoparticles is explored, including quantitative analyses of conductivity and the SMP composite's storage and loss moduli. The resulting flexible and conductive bi-layer SMP adhesive supports load while attached to surfaces of varied curvature. Variations on the SMP formula have their adhesive and mechanical properties tested, and are used to produce a self-contained SMP prototype wall-hanging adhesive

    The Architecture of Soft Machines

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    This thesis speculates about the possibility of softening architecture through machines. In deviating from traditional mechanical conceptions of machines based on autonomous, functional and purely operational notions, the thesis proposes to conceive of machines as corporeal media in co-constituting relationships with human bodies. As machines become corporeal (robots) and human bodies take on qualities of machines (cyborgs) the thesis investigates their relations to architecture through readings of William S. Burroughs’ proto-cyborgian novel The Soft Machine (1961) and Georges Teyssot’s essay ‘Hybrid Architecture: An Environment for the Prosthetic Body’ (2005) arguing for a revision of architecture’s anthropocentric mandate in favour of technologically co-constituting body ideas. The conceptual shift in man-machine relations is also demonstrated by discussion of two installations shown at the Venice Biennale, Daniel Libeskind’s mechanical Three Lessons in Architecture (1985) and Philip Beesely’s responsive Hylozoic Ground (2010). As the purely mechanical model has been superseded by a model that incorporates digital sensing and embedded actuation, as well as soft and compliant materiality, the promise of softer, more sensitive and corporeal conceptions of technology shines onto architecture. Following Nicholas Negroponte’s ambition for a ‘humanism through machines,’ stated in his groundbreaking work, Soft Architecture Machines (1975), and inspired by recent developments in the emerging field of soft robotics, I have developed a series of practical design experiments, ranging from soft mechanical hybrids to soft machines made entirely from silicone and actuated by embedded pneumatics, to speculate about architectural environments capable of interacting with humans. In a radical departure from traditional mechanical conceptions based on modalities of assembly, the design of these types of soft machines is derived from soft organisms such as molluscs (octopi, snails, jellyfish) in order to infuse them with notions of flexibility, compliance, sensitivity, passive dynamics and spatial variability. Challenging architecture’s alliance with notions of permanence and monumentality, the thesis finally formulates a critique of static typologisation of space with walls, floors, columns or windows. In proposing an embodied architecture the thesis concludes by speculating about architecture as a capacitated, sensitive and sensual body informed by reciprocal conditioning of constituent systems, materials, morphologies and behaviours
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