25 research outputs found

    CROMSCI - A CLIMBING ROBOT WITH MULTIPLE SUCKING CHAMBERS FOR INSPECTION TASKS

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    Design and Fabrication of Soft 3D Printed Actuators: Expanding Soft Robotics Applications

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    Soft pneumatic actuators are ideal for soft robotic applications due to their innate compliance and high power-weight ratios. Presently, the majority of soft pneumatic actuators are used to create bending motions, with very few able to produce significant linear movements. Fewer can actively produce strains in multiple directions. The further development of these actuators is limited by their fabrication methods, specifically the lack of suitable stretchable materials for 3D printing. In this thesis, a new highly elastic resin for digital light projection 3D printers, designated ElastAMBER, is developed and evaluated, which shows improvements over previously synthesised elastic resins. It is prepared from a di-functional polyether urethane acrylate oligomer and a blend of two different diluent monomers. ElastAMBER exhibits a viscosity of 1000 mPa.s at 40 °C, allowing easy printing at near room temperatures. The 3D-printed components present an elastomeric behaviour with a maximum extension ratio of 4.02 ± 0.06, an ultimate tensile strength of (1.23 ± 0.09) MPa, low hysteresis, and negligible viscoelastic relaxation

    Dynamic modeling and bioinspired control of a walking piezoelectric motor

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    Szufnarowski F. Dynamic modeling and bioinspired control of a walking piezoelectric motor. Bielefeld: Universität Bielefeld; 2013.Piezoelectric motors have increasingly extended their field of applications during recent years. Improved material properties and manufacturing techniques have led to a variety of designs which can achieve theoretically unlimited displacements for moderate voltage levels while retaining a relatively high stiffness. In practical terms, this leads to stronger and faster motors which become a viable alternative to electromagnetic drives, especially if compact size and small weight are important. The piezoelectric motor considered in this work consists of four piezoelectric bender elements which can forward a ceramic bar by means of a frictional interaction. The drive elements can be compared to "legs" walking on a movable plane. The walking motor offers outstanding force generation capabilities for a motor of its size. Despite this fact, this motor has not been used in a force control scenario before and no motor models exist in the literature which can reproduce the effect of load on its performance. In this work, two dynamic motor models are developed to address the latter issue. Both of them faithfully reproduce the non-linear motor velocity decrease under load. The first model is based on an analytic approach and describes the low-level frictional interactions between the legs and the ceramic bar by means of several physically meaningful assumptions. This analytic model explains several non-linear phenomena in the operation of the walking motor within the full bandwidth of its rated operation. Non-linear influences due to the impact dynamics of the legs, ferroelectric hysteresis and friction are identified in the motor and new insights for an improved motor design as well as an improved motor-drive strategy gained. Moreover, the analytic model finds its application in a theoretical investigation of an alternative motor-drive strategy which is based on findings in insect walking. Specifically, it is shown that the performance of the motor can be improved by a half in terms of its force generation and doubled in terms of its maximal velocity, as compared to classical drive approaches, if the bioinspired drive strategy as proposed in this work is used. The second model is based on an experimental approach and system identification. Although less general, the second model is well-suited for a practical application in a force-control scenario. In particular, the experimental model is used in this work for the development of a load compensation strategy based on force feedback which restores the linearity of motor operation for moderate levels of loading. Based on the linearized motor model, a force controller is developed whose performance is evaluated both theoretically and experimentally. The developed force controller is also used in a bioinspired control scenario. Specifically, two walking motors together with their force controllers are employed in a 1-DOF antagonistic joint as force generators. The motors are supposed to partially mimic the functionality of a muscle based on the non-linear force-length relation as derived by Hill. A simple positioning task shows the feasibility of this kind of non-standard application of a piezoelectric motor. Beside the development of motor models and bioinspired control approaches, this work addresses the issue of drive-signal generation for the walking motor. Specifically, the development of motor-drive electronics is presented which supersedes the commercially available products due to its compactness and the possibility of waveform generation at much higher drive frequencies, above 50 kHz, as compared to the nominal limit of 3 kHz and commercial products. In this context, the possibility of motor operation at ultrasonic frequencies is discussed which would benefit the motor in terms of its speed and the absence of audible noises

    Using MapReduce Streaming for Distributed Life Simulation on the Cloud

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    Distributed software simulations are indispensable in the study of large-scale life models but often require the use of technically complex lower-level distributed computing frameworks, such as MPI. We propose to overcome the complexity challenge by applying the emerging MapReduce (MR) model to distributed life simulations and by running such simulations on the cloud. Technically, we design optimized MR streaming algorithms for discrete and continuous versions of Conway’s life according to a general MR streaming pattern. We chose life because it is simple enough as a testbed for MR’s applicability to a-life simulations and general enough to make our results applicable to various lattice-based a-life models. We implement and empirically evaluate our algorithms’ performance on Amazon’s Elastic MR cloud. Our experiments demonstrate that a single MR optimization technique called strip partitioning can reduce the execution time of continuous life simulations by 64%. To the best of our knowledge, we are the first to propose and evaluate MR streaming algorithms for lattice-based simulations. Our algorithms can serve as prototypes in the development of novel MR simulation algorithms for large-scale lattice-based a-life models.https://digitalcommons.chapman.edu/scs_books/1014/thumbnail.jp

    Design optimisation of shape memory alloy linear actuator applications

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    Shape memory alloy (SMA) actuators have drawn much attention and interest in recent decades due to their unique properties; and, are expected to be increasingly integrated within commercial automotive applications. Key advantages of SMA actuators include: potentially simplified construction, whereby the SMA can act as both sensor and actuator simultaneously; compatibility with Joule heating and convective ambient cooling; and, potential mass advantages over competing actuation technologies. These attributes potentially allow for the development of simpler, more reliable and cost effective actuation systems with significant reduction in mechanical complexity and size. SMA is readily available in commercial quantities and exhibits high wear resistance and durability, which make it an ideal candidate for application in automotive grade applications. Despite these identified advantages, SMA actuators are subject to a series of technical challenges associated with:  - Relatively small strain (displacement or stroke)  - Achievable frequency (actuation speed)  - Controllability (and stability)  - Positional accuracy  - Energy efficiency These technical challenges contribute to a relatively low success rate of commercial SMA actuator applications; and, provide motivation for this program to generate relevant research outcomes that enhance the commercialisation of SMA actuators. An extensive literature review of over 500 journal and patent documents was conducted to provide a clear roadmap for the commercial imperatives for SMA design. The formulated research methodology identifies milestones required for achieving the research objectives, which were addressed as research themes. Based on this literature review, the following research themes were identified:  - Design methods to resolve SMA actuator limitations  - Development of simple and practical numerical models for SMA actuator response  - Data for SMA linear actuator design Specific research contributions within these themes are presented within the thesis, with the objective of enhancing the commercial application of shape memory alloy (SMA) linear actuators, and include:  - A comprehensive analysis of SMAs: history, commercial applications, strength and limitations, design challenges and         opportunities.  - A novel investigation of transient heat transfer scenarios for cylindrical systems associated with their crossover and critical radii.  - Development of novel latent heat models for analytical and numerical applications, and proposal of readily applied activation and deactivation charts compatible with the requirements of SMA actuator designers.  - A novel investigation of the morphological effects of SMA-pulley systems (i.e. pulley diameter, SMA and lagging diameter) on structural and functional fatigue
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