514 research outputs found
Life cycle monitoring of composite aircraft components with structural health monitoring technologies
Life cycle monitoring could considerably improve the economy and sustainability of composite aircraft components. Knowledge about the quality of a component and its structural health allows thorough exploitation of it’s useful life and offers opportunity for optimization.
Current life cycle monitoring efforts can be split in two main fields 1) process monitoring and 2) structural
health monitoring with little overlap between them. This work aims to propose an integral monitoring approach,
enabling entire life monitoring with the same sensor. First, the state of the art of both composite
manufacturing as well as structural health monitoring technologies is presented. Piezoelectric sensors have
been ruled out for further investigation due their brittleness.
Fiber optical sensors and electrical property-based methods are further investigated. Distributed fiber optic
sensors have been successfully used in composite manufacturing trials. Two processes were demonstrated:
vacuum assisted resin transfer molding and resin infusion under flexible tooling. Due to their flexibility,
optical fibers can survive the loads occurring during manufacturing and deliver valuable insights. It is shown
for the first time numerically and experimentally, that fiber bed compaction levels and volume fractions can
be calculated from the optical frequency shift measured by the optical fiber sensors. The same sensor was
used for subsequent structural health monitoring. This proves that the gap between process monitoring and
structural health monitoring can be closed with mutual benefits in both areas.
The final chapter presents a novel electrical property-based sensing technique. The sensors are highly flexible
and manufactured with a robot-based 3D-printing method. They are shown to reliably work as strain sensors and crack detectors.
This work presents a thorough investigation of available and novel sensing technologies for process monitoring
and structural health monitoring settings. The results obtained could pave the way to more efficient
aircraft structures.Open Acces
Applied Mathematics to Mechanisms and Machines
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
Dual Loop Rider Control of a Dynamic Motorcycle Riding Simulator
Compared to the automotive industry, the use of simulators in the motorcycle domain is negligible as for their lack of usability and accessibility. According to the state-of-the-art, it is e.g. not possible for motorcyclists to intuitively control a high-fidelity dynamic motorcycle riding simulator when getting in contact with it for the first time. There are four main reasons for the insufficient simulation quality of dynamic motorcycle riding simulators:
â–Ş The instability of single-track vehicles at low speed,
â–Ş The steering force-feedback with highly velocity-dependent behavior,
â–Ş Motion-simulation (high dynamics, roll angle, direct contact to the environment),
â–Ş The specific influence of the rider to vehicle dynamics (incl. rider motion).
The last bullet point is peculiar for motorcycles and dynamic motorcycle riding simulators in comparison with other vehicle simulators, as motorcycles are significantly affected in their dynamics by the rider’s body motion. However, up until today, almost no special emphasis has been put on the consideration of rider motion on dynamic motorcycle riding simulators.
In this thesis, a motorcycle riding simulator is designed, constructed and put into operation. The focus here is attaching a real rider to a virtual motorcycle. Based on a commercially available multi-body-simulation model, a simulator architecture is designed, that allows to control the virtual motorcycle not only by steering, but by rider leaning as well. This is realized by determining the so-called rider induced roll torque, that allows a holistic measurement of the apparent coupling forces between rider and simulator mockup.
Performance measures and study concepts are developed that allow to rate the system. In expert and participant studies, the influence of the system on the riding behavior of the simulator is investigated. It is shown that the rider motion determination allows realistic control inputs and has a positive effect on the stabilization at various velocities. The feedback of the rider induced roll torque to the virtual dynamics model allows study participants to control the virtual motorcycle more intuitively. The vehicle states during cornering are affected as expected from real riding. First results indicate that it becomes easier for naĂŻve study participants to access the simulator in first-contact scenarios. The achieved improvements regarding the rideability of the simulator however do not suffice to overcome the abovementioned challenges to a degree that allows for a completely intuitive interaction with the simulator throughout the whole dynamic range
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Soft actuator and agile soft robot
Robots play an important part in many aspects of our society by doing repetitive, dangerous, or precision tasks. Most existing robots are made of rigid components, which lack passive compliance and pose a challenge in adapting to the environment and safe human-robot interaction. Rigid robots may be equipped with sensors and programmed with proprioceptive feedback control to achieve active compliance, but this may fail in the event of unforeseen situations or sensor failure.
In contrast, animals have evolved flexible or soft body parts to help them adapt to changing environments. Soft robotics is an emerging field in robotics, drawing inspiration from nature by integrating soft material into the actuator and mechanical design. With the inclusion of soft material, soft actuators and robots can deform actively/passively, making it possible to sense, absorb impact, and adapt to its environment with deformation. However, while soft actuators/robots have superior properties to rigid ones, they are often challenging to manufacture and control precisely. In addition, they may suffer from slow speed and material degradation. Thus, in this thesis, we aim to address the issues in developing high-performance soft actuators and soft robots.
The thesis is divided into two parts. In the first part, we focus on improving the manufacturability and performance of a self-contained soft actuator originated in the Creative Machines Lab. The soft actuator is composed of a cured silicone-ethanol mixture embedded with heating coils. When the coils are electrically actuated, ethanol trapped inside undergoes liquid-vapor transitions, and thus the actuator undergoes extreme volume change. While this actuator exhibits high strain and high stress, it is very slow to actuate, has limited life cycles, and requires molds to manufacture.
The first part of the thesis will address these issues. Specifically, in chapter 2, we discuss using multi-material 3D printing to automate the manufacturing of silicone-ethanol composite. In chapter 3, we discuss using laser-cut flexible Kirigami patterns to improve the manufacturability of its heating element. Chapter 4 characterizes its actuation profile and addresses improvements to the thermal conductivity by infusing thermally conductive fillers.
Soft actuation is an actively researched area; however, many high-performance soft actuators are challenging to manufacture and thus are less accessible to the general robotics community. Conventional actuators such as electric motors are widely available but lack flexibility. Therefore, the second part of the thesis aims at combining rigid motors with soft materials to design and control high-performance hybrid soft robots. Simulation is a good way to evaluate and optimize robot design and control. However, existing simulators that support motor-driven soft robots have limited features. Chapter 5 discusses this issue and presents a physically based real-time soft robot simulator capable of simulating motor-driven soft robots. In addition, chapter 5 presents the design and control of a 3D printed hybrid soft quadruped robot. Chapter 6 presents the design and control of a 3D printed hybrid soft humanoid robot.
The two parts of the thesis aim to improve aspects in soft actuators and soft robots. In conclusion, we summarize the lessons learned in developing soft actuators/robots and new possibilities and challenges for advancing soft robotics research
Agricultural Structures and Mechanization
In our globalized world, the need to produce quality and safe food has increased exponentially in recent decades to meet the growing demands of the world population. This expectation is being met by acting at multiple levels, but mainly through the introduction of new technologies in the agricultural and agri-food sectors. In this context, agricultural, livestock, agro-industrial buildings, and agrarian infrastructure are being built on the basis of a sophisticated design that integrates environmental, landscape, and occupational safety, new construction materials, new facilities, and mechanization with state-of-the-art automatic systems, using calculation models and computer programs. It is necessary to promote research and dissemination of results in the field of mechanization and agricultural structures, specifically with regard to farm building and rural landscape, land and water use and environment, power and machinery, information systems and precision farming, processing and post-harvest technology and logistics, energy and non-food production technology, systems engineering and management, and fruit and vegetable cultivation systems. This Special Issue focuses on the role that mechanization and agricultural structures play in the production of high-quality food and continuously over time. For this reason, it publishes highly interdisciplinary quality studies from disparate research fields including agriculture, engineering design, calculation and modeling, landscaping, environmentalism, and even ergonomics and occupational risk prevention
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