24 research outputs found

    Freehand three dimensional ultrasound for imaging components of the musculoskeletal system

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    There have been reports on the use of Ultrasound (US) for monitoring fracture repair and for measuring muscle volume. Change in muscle mass is a useful bio-marker for monitoring the use and disuse of muscle, and the affects of age, disease and injury. The main modality for imaging bone is X-ray and for muscle volume Magnetic Resonance (MR). Previous studies have shown US to have advantages over X-ray and MR. US can image all stages of the fracture repair process and can detect signs of healing 4-6 weeks before X-ray allowing earlier detection of possible complications. Compared to MR, US is less resource intensive, easier to access and also has fewer exclusion criteria for patients. Despite these advantages, the limited field of view that US can provide results in high operator dependency for scan interpretation and also for length and volume measurements. Three-dimensional Ultrasound (3D US) has been developed to overcome these limitations and has been used to provide extended field of view images of the foetus and the heart and to obtain accurate volume measurements for organs. In this thesis it is hypothesized that 3D US can provide a more comprehensive method of imaging fracture repair than X-ray and is also a viable alternative to MR for determining muscle volumes in vivo. Initially, an electromagnetically (EM) tracked 3D US system was evaluated for clinical use using phantom-based experiments. It was found that the presence of metal objects in or near the EM field caused distortion and resulted in errors in the volume measurements of phantoms of up to ±20%. An optically tracked system was also evaluated and it was found that length measurements of a phantom could be made to within ±1.3%. Fracture repair was monitored in five patients with lower limb fractures. Signs of healing were visible earlier on 3D US with a notable, although variable, lag between callus development on X-ray compared to 3D US. 3D US provided a clearer view of callus formation and the changes in density of the callus as it matured. Additional information gained by applying image processing methods to the 3D US data was used to develop a measure of callus density and to identify the frequency dependent appearance of the callus. Volume measurements of the rectus femoris quadricep muscle were obtained using 3DUS from eleven healthy volunteers and were validated against volume measurements derived using MR. The mean difference between muscle volume measurements obtained using 3D US and MR was 0.53 cm3 with a standard deviation of 1.09 cm3 and 95% confidence intervals of 0.20 - 1.27 cm3 In conclusion, 3D US demonstrates great potential as a tool for imaging components of the musculoskeletal system and as means of measuring callus density

    Reviewing high-level control techniques on robot-assisted upper-limb rehabilitation

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    This paper presents a comprehensive review of high-level control techniques for upper-limb robotic training. It aims to compare and discuss the potentials of these different control algorithms, and specify future research direction. Included studies mainly come from selected papers in four review articles. To make selected studies complete and comprehensive, especially some recently-developed upper-limb robotic devices, a search was further conducted in IEEE Xplore, Google Scholar, Scopus and Web of Science using keywords (‘upper limb*’ or ‘upper body*’) and (‘rehabilitation*’ or ‘treatment*’) and (‘robot*’ or ‘device*’ or ‘exoskeleton*’). The search is limited to English-language articles published between January 2013 and December 2017. Valuable references in related publications were also screened. Comparative analysis shows that high-level interaction control strategies can be implemented in a range of methods, mainly including impedance/admittance based strategies, adaptive control techniques, and physiological signal control. Even though the potentials of existing interactive control strategies have been demonstrated, it is hard to identify the one leading to maximum encouragement from human users. However, it is reasonable to suggest that future studies should combine different control strategies to be application specific, and deliver appropriate robotic assistance based on physical disability levels of human users

    Human-Robot Collaborations in Industrial Automation

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    Technology is changing the manufacturing world. For example, sensors are being used to track inventories from the manufacturing floor up to a retail shelf or a customer’s door. These types of interconnected systems have been called the fourth industrial revolution, also known as Industry 4.0, and are projected to lower manufacturing costs. As industry moves toward these integrated technologies and lower costs, engineers will need to connect these systems via the Internet of Things (IoT). These engineers will also need to design how these connected systems interact with humans. The focus of this Special Issue is the smart sensors used in these human–robot collaborations

    Acta Polytechnica Hungarica 2020

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    Model Based Control of Soft Robots: A Survey of the State of the Art and Open Challenges

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    Continuum soft robots are mechanical systems entirely made of continuously deformable elements. This design solution aims to bring robots closer to invertebrate animals and soft appendices of vertebrate animals (e.g., an elephant's trunk, a monkey's tail). This work aims to introduce the control theorist perspective to this novel development in robotics. We aim to remove the barriers to entry into this field by presenting existing results and future challenges using a unified language and within a coherent framework. Indeed, the main difficulty in entering this field is the wide variability of terminology and scientific backgrounds, making it quite hard to acquire a comprehensive view on the topic. Another limiting factor is that it is not obvious where to draw a clear line between the limitations imposed by the technology not being mature yet and the challenges intrinsic to this class of robots. In this work, we argue that the intrinsic effects are the continuum or multi-body dynamics, the presence of a non-negligible elastic potential field, and the variability in sensing and actuation strategies.Comment: 69 pages, 13 figure

    Industrial Applications: New Solutions for the New Era

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    This book reprints articles from the Special Issue "Industrial Applications: New Solutions for the New Age" published online in the open-access journal Machines (ISSN 2075-1702). This book consists of twelve published articles. This special edition belongs to the "Mechatronic and Intelligent Machines" section

    Multi-Finger Haptic Devices Integrating Miniature Short-Stroke Actuators

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    The omnipresence of electronic devices in our everyday life goes together with a trend that makes us always more immersed during their utilization. By immersion, we mean that during the development of a new product, it is more and more required to stimulate several senses of the user so as to make the product more attractive. The sense of touch does not escape the rule and is more and more considered. Definitely democratized by its integration in smart phones with touchscreens, the haptic feedback allows enhancing the human-machine interactions in many ways. For instance by improving the comfort of use of a button through the modification of its force feedback. It can also offer an interactive experience during the manipulation of digital information and even improve the communication, particularly through the internet and for blind people, with the introduction of non-verbal signals. For these reasons, the present thesis focuses on the conception of multi-finger haptic devices, a new kind of peripherals integrating multiple actuators and capable of providing a fully programmable force feedback to the user's fingers. A global methodology is presented, outlining the different constituents necessary for their conception: actuator, sensor, control, communication and software user interface. Then, generic tools corresponding to the two first elements are presented. An accurate modeling of miniature electromagnetic short-stroke actuators is made possible thanks to the combination of 3D finite element modeling (FEM) and design of experiments (DOE). The non-usual behavior of magnetic flux lines in miniature actuators with relatively large airgaps imposes to avoid simplified analytical models and to use the reliable results of finite elements. The long computation times required by 3D FEM are balanced by the use of selective DOE making the modeling methodology easily adaptable, rapid and accurate. The parametrical model of the force provided by the modeling methodology is then integrated in a full parametrical setup allowing for the optimization of the actuator force using a conventional algorithm. The advantage of the parametrical optimization is that complementary non-linear constraints such as weight and temperature can be added, making the model multi-physic. Then, several original position measurement techniques using existing sensors are developed including a low-cost custom single-photointerrupter sensor allowing for direction discrimination for fast-prototyping and a hybrid sensing method using tiny Hall sensors and taking advantage of the leaks of the main actuator magnet. Two innovative self-sensing methods are then presented, allowing for the measurement of the mover position of linear short-stroke actuators. The first solution estimates the position of the coil by measuring the acceleration through the back emf. However in this case, a constant acceleration is required, which strongly restrains the application scope. The second solution allows for a real-time measurement of the position thanks to a passive oscillating RLC circuit influenced by the variation of the coil impedance. All the solutions presented are low-cost, compact and require few computation resources. Finally, in order to illustrate the methodology proposed along the thesis, several prototypes are fabricated, giving an overview of the possibilities offered by multi-finger haptic devices. A haptic numeric pad is notably used in an experiment made in collaboration with the University Service of Child and Adolescent Psychiatry in Lausanne with the aim of improving the impaired emotional processing of psychotic adolescents. Moreover, the successful identification of several touch sensations on the same haptic pad lays the first stones of a new tactile language

    On the role of stability in animal morphology and neural control

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    Mechanical stability is vital for the fitness and survival of animals and is a crucial aspect of robot design and control. Stability depends on multiple factors, including the body\u27s intrinsic mechanical response and feedback control. But feedback control is more fragile than the body\u27s innate mechanical response or open-loop control strategies because of sensory noise and time-delays in feedback. This thesis examines the overarching hypothesis that stability demands have played a crucial role in how animal form and function arise through natural selection and motor learning. In two examples, finger contact and overall body stability, we investigated the relationship between morphology, open-loop control, and stability. By studying the stability of the internal degrees of freedom of a finger when pushing on a hard surface, we find that stability limits the force that we can produce and is a dominant aspect of the neural control of the finger\u27s muscles. In our study on whole body lateral stability during locomotion in terrestrial animals, we find that the overall body aspect ratio has evolved to ensure passive lateral stability on the uneven terrain of natural environments. Precisely gripping an object with the fingertips is a hallmark of human hand dexterity. In Chapter 2, we show how human fingers are intrinsically prone to a buckling-type postural instability and how humans use careful neural orchestration of our muscles so that the elastic response of our muscles can suppress the intrinsic instability. In Chapter 3, we extend these findings further to examine the nature of neuromuscular variability and how the nervous system deals with the need for muscle-induced stability. We find that there is structure to neuromuscular variability so that most of the variability lies within the subspace that does not affect stability. Inspired by the open-loop stable control of our index fingers, in Chapter 4, we derive open-loop stability conditions for a general mechanical linkage with arbitrary joint torques subjected to holonomic constraints. The solution that we derive is physically realizable as cable-driven active mechanical linkages. With a user-prescribed cable layout, we pose the problem of actuating the system to maintain stability while subject to goals like energy minimization as a convex optimization problem. We are thus able to use efficient optimization methods available for convex problems and demonstrate numerical solutions in examples inspired by the finger. Chapter 5 presents a general formulation of the stability criteria for active mechanical linkages subject to Pfaffian holonomic and non-holonomic constraints. Active mechanical linkages subject to multiple constraints represent the mechanics of systems spanning many domains and length scales, such as limbs and digits in animals and robots, and elastic networks like actin meshes in microscopic systems. We show that a constrained mechanical linkage with regular stiffness and damping, and circulation-free feedback, can only destabilize by static buckling when subject to holonomic constraints. In contrast, the same mechanical linkage, subject to a non-holonomic constraint, such as a skate contact, can exhibit either static buckling or flutter instability. Chapter 6 moves away from neural control and studies the shape of animal bodies and their relationship to stability in locomotion. We investigate why small land animals tend to have a crouched or sprawled posture, whereas larger animals are generally more upright. We propose a new hypothesis that the scaling of body aspect ratio with size is driven by the scale-dependent unevenness of natural terrain. We show that the scaling law arising from the need for stability on rough natural terrain correctly predicts the frontal aspect ratio scaling law across 335 terrestrial vertebrates and invertebrates, spanning eight orders of magnitude in mass so that smaller animals have a wider aspect ratio. We also carry out statistical analyses that consider the phylogenetic relationship among the species in our dataset to show that the scaling is not due to gradual changes of the traits over time. Thus, stability demands on natural terrain may have driven the macroevolution of body aspect ratio across terrestrial animals. Interrogating unstable and marginally stable behaviors has helped us identify the morphological and control features that allow animals to perform robustly in noisy environments where perfect sensory feedback cannot be assumed. Although the thesis identifies the `what\u27 and `why,\u27 further studies are needed to understand `how\u27 mechanics and development intertwine to give rise to control and form in growing and adapting biological organisms

    Applied Mathematics to Mechanisms and Machines

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    This book brings together all 16 articles published in the Special Issue "Applied Mathematics to Mechanisms and Machines" of the MDPI Mathematics journal, in the section “Engineering Mathematics”. The subject matter covered by these works is varied, but they all have mechanisms as the object of study and mathematics as the basis of the methodology used. In fact, the synthesis, design and optimization of mechanisms, robotics, automotives, maintenance 4.0, machine vibrations, control, biomechanics and medical devices are among the topics covered in this book. This volume may be of interest to all who work in the field of mechanism and machine science and we hope that it will contribute to the development of both mechanical engineering and applied mathematics
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