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Proceedings Papers
David Gonzalez Rodriguez, Jose Garcia, Benjamin Ducharne, Richard Voyles, Robert A. Nawrocki, Brittany Newell
Proc. ASME. SMASIS2020, ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T01A004, September 15, 2020
Paper No: SMASIS2020-2239
Abstract
3D printed flexible sensors have demonstrated great potential for utilization in a variety of different applications including healthcare, environmental sensing, and industrial applications. In recent years, research on this topic has increased to meet low-cost sensing needs due to the development of innovative materials and printing techniques that reduce cost, production time, and enhance the electrical and mechanical properties of the sensors. This paper presents computational simulations of 3D printed flexible sensors, capable of producing an output signal based on the deformation caused by external forces. Two different sensors were designed and tested, working based on a capacitance and resistance change produced by structural deformation. The capacitance sensor was designed maximizing the area of the electrodes and distributing the electrodes over a flexible membrane taking advantage of the produced deformation to reduce the distance between the electrodes. The reduction in the distance between the electrodes increases the capacitance value of the structure. The capacitance sensor was able to almost triple its baseline capacitance when 30 kPa of pressure was applied. The resistance sensor was designed with one continuous flexible conductive element attached to a flexible membrane, taking advantage of the distortion induced in the conductive element. The deformation in the conductive element increases the length of the resistor and causes the resistance value of the structure to increase. The resistance sensor was able to increase its resistance by 1200 ω with 30 kPa of applied pressure. Finally, preliminary results of 3D printed sensors were demonstrated.
Proceedings Papers
Proc. ASME. SMASIS2020, ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T04A011, September 15, 2020
Paper No: SMASIS2020-2254
Abstract
This work presents the design, optimization and testing of a novel lattice-structure based morphing wing. The lattice-structure concept spans a large design space, including the possibility to vary among others material, number, distribution and the orientation of the lattice rods. The used parametrization scheme considers both the positioning of the Carbon Fiber Reinforced Polymer (CFRP) rods and their orientation in spherical coordinates within the wing, thus allowing to appropriately cover the design space, while reducing the set of variables during the design optimization procedure. The morphing deformations are relying on electromechanical servomotors. Design objectives include weight minimization and structural requirements, while achieving sufficient roll control. The local deformation induced by the electromechanical actuators is distributed by an internal skeleton structure across the rear section of the wing. An extensible skin is ensuring a smooth cambering and minimizes the required actuation energy. The in-house developed and validated simulation environment couples the aerodynamic pressure and the structural deformations, to accurately predict the aeroelastic response of the wing to aerodynamic and actuation forces, considering large deformations. In addition to the lattice structure, the aeroelastic optimization also considers the actuation layout, and the layup-thickness of the wing skin. Planform and airfoil shape are fixed to a NACA0012 airfoil with 80 cm span, and 30 cm chord. The structural and morphing behavior was evaluated on a technology demonstrator. The demonstrator provides large continuous shape changes, improving the aerodynamic performance and achieving large deflections and high rolling moment coefficients. This is mainly achieved by exploiting the interaction of the tailored internal structure and the actuation system. Since the deformation is distributed over a large portion of the wing, local stress concentrations are minimized, and actuation forces are reduced. Wing-up bending tests have been carried out, confirming the simulation results, respectively the load-carrying capability of the presented concept. Furthermore, actuation tests resulted in peak-to-peak trailing edge deflections of 31mm, respectively a rolling moment coefficient of 0.062, which are consistent with the simulation results and guarantee sufficient roll control.
Proceedings Papers
Proc. ASME. SMASIS2020, ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T06A001, September 15, 2020
Paper No: SMASIS2020-2273
Abstract
Due to the high cost of equipment and lack of trained personnel, manual palpation is a preferred alternative breast examination technique over mammography. The process involves a thorough search pattern using trained fingers and applying adequate pressure, with the objective of identifying solid masses from the surrounding breast tissue. However, palpation requires skills that must be obtained through adequate training in order to ensure proper diagnosis. Consequently, palpation performance and reporting techniques have been inconsistent. Automating the palpation technique would optimize the performance of self-breast examination, optimize clinical breast examinations (CBE), and enable the visualization of breast abnormalities as well as assessing their mechanical properties. Various methods of reconstructing the internal mechanical properties of breast tissue abnormalities have been explored. However, all systems that have been reported are bulky and rely on complex electronic systems. Hence, they are both expensive and require trained medical professionals. The methods also do not involve palpation, a key element in CBE. This research aims in developing a portable and inexpensive automated palpable system that mimics CBE to quantitatively image breast lumps. The method uses a piezoresistive sensor equipped probe consisting of an electronic circuit for collecting deformation-induced electrical signals. The piezoresistive sensor is made by spraying microwave exfoliated graphite/latex blend on a latex sheet. Lumps can be detected by monitoring a change in electrical resistance caused by the deformation of the sensor which is induced by abnormalities in the breast tissue. The electrical signals are collected using a microcontroller and a pixelated image of the breast can be reconstructed. The research is still in progress, and this report serves as proof of concept testing by pressing the probe with hand pressure and reconstructing the electrical signals using Microsoft Excel. Four maps were created for qualitatively analyzing the result. The pressure maps clearly display areas where pressure was applied, indicating the potential of the probe in detecting breast tissue abnormalities. The pressure maps show the feasibility for using such a sensor for the application in CBE. Furthermore, a sensor such as this is also possible of detecting the depth and size of masses within breast tissue, which, may lead to a more accurate diagnosis. Better manufacturing, accuracy, precision, and realtime data feeds are areas of future consideration for this project. This project involves knowledge and applications from mechanical, electrical, computational, and materials engineering.
Proceedings Papers
Proc. ASME. SMASIS2020, ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T04A013, September 15, 2020
Paper No: SMASIS2020-2256
Abstract
The demand of affordable, renewable electric energy is still increasing. Wind energy is seen as one of the most promising resources for future electric energy supply. To reduce the cost of wind energy the dimensions of wind energy turbines are still increasing. This leads to higher power output due to the larger rotor diameters, but also due to the higher wind speeds above the boundary layer. This increase in rotor diameter is achieved at the expense of much higher structural loads especially in the rotor blade root. These loads consist of bending moments, that are mainly caused by gravity, wind shear, gusts and the tower influence to the blade. A reduction of these root bending moments would allow a further increase of the rotor diameter, a longer lifetime or a lighter design and therefore be advantageous for the turbine. Load reduction can be achieved by using a trailing edge flap at the outer region of the blade, comparable to control surfaces of aircraft. This trailing edge is capable of moving several times per blade revolution and allows the manipulation of the flow to alleviate changes in the aerodynamic loading. In contrast to aircraft, sealing against environmental media, such as rain, dust, insects and so on is much more important to allow a high lifetime and low maintenance effort. Therefore, a flexible and gapless morphing trailing edge has been designed within the SmartBlades projects at the German Aerospace Center (DLR) for the mentioned purpose. Based on this design, a demonstrator was built, which was tested in a wind tunnel and on a rotational test site for its performance. The paper will present the approach beginning with some design and modeling considerations of the flexible trailing edge and the demonstrator, which was used for testing. Main focus of the paper is the presentation of results obtained from a wind tunnel experiment at Oldenburg University and the rotational experiment at the field research site of the Technical University in Denmark (DTU). In these experiments, the effectiveness of the trailing edge flap could be demonstrated in the wind tunnel as well as in free field. Based on pressure taps and force sensors, the change in the lift of the airfoil due to the deflection of the flexible trailing edge was measured and the resulting polars are shown in this paper. Furthermore, the result of different simple control strategies for the trailing edge in terms of load reduction at the rotating test rig will be presented.
Proceedings Papers
Proc. ASME. SMASIS2020, ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T04A004, September 15, 2020
Paper No: SMASIS2020-2210
Abstract
A slotted natural-laminar-flow airfoil design is a two-element airfoil design that employs a slot between the fore and aft elements. This slot alters the pressure recovery condition on the suction surface of the fore element, minimizing skin-friction and inhibiting the laminar to turbulent transition. These benefits reduce overall aircraft drag and increase wing lift. This allows smaller planforms, in turn, reducing fuel burn. This paper investigates the proposal that by help of piezocomposite surface actuation the aft element can be moved, rotated, and morphed to be used as a high-lift effector for take-off and landing conditions. A theoretical analysis is performed using a coupled fluid-structure interaction method assuming static aero-elastic behavior. During analysis the fore-element of the multi-element airfoil is assumed rigid. Thus, shape optimization is limited exclusively to the aft element. Airfoil morphing is achieved by way of piezocomposite actuating elements applied to the pressure and suction sides of the aft element. A genetic algorithm is used to independently optimize substrate thicknesses for each piezocomposite actuator as well as voltage, chord position and piezocomposite length. The nominal and leading edge substrate thicknesses of the airfoil are also varied. The optimized geometry for the high lift configuration is presented.
Proceedings Papers
Proc. ASME. SMASIS2020, ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T06A010, September 15, 2020
Paper No: SMASIS2020-2397
Abstract
This paper proposes a novel pneumatic valve adapter that decreases the size and quantity of pneumatic tubes and valves necessary for soft robotics by mimicking cardiovascular systems. Some cardiovascular systems, evolved to be powered by a single reservoir, the heart, which in turn powers the rest of the body by systematically opening and closing valves as needed. The presented valve adapter consists of a set of concentric tube, where both tubes have strategically patterned holes. The inner tube can be moved translationally and rotationally to align with designated hole positions in the outer tube, thus opening and closing pathways to chambers for pressure flow. The two-tube system can be used to either pressurize a chamber or depressurize a chamber or multiple chambers simultaneously.
Proceedings Papers
Proc. ASME. SMASIS2020, ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T06A011, September 15, 2020
Paper No: SMASIS2020-2399
Abstract
Variable stiffness structures lie at the nexus of soft robots and traditional robots as they enable the execution of both high-force tasks and delicate manipulations. Laminar jamming structures, which consist of thin flexible sheets encased in a sealed chamber, can alternate between a rigid state when a vacuum is applied and a flexible state when the layers are allowed to slide in the absence of a pressure gradient. In this work, an additional mode of controllability is added by clamping and unclamping the ends of a simple laminar jamming beam structure. Previous works have focused on the translational degree of freedom that may be controlled via vacuum pressure; here we introduce a rotational degree of freedom that may be independently controlled with a clamping mechanism. Preliminary results demonstrate the ability to switch between three states: high stiffness (under vacuum), translational freedom (with clamped ends, no vacuum), and rotational freedom (with ends free to slide, no vacuum).
Proceedings Papers
Proc. ASME. SMASIS2020, ASME 2020 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T08A001, September 15, 2020
Paper No: SMASIS2020-2219
Abstract
Soft pneumatic actuators have found many applications in robotics and adaptive structures. Traditionally, these actuators are constructed by wrapping layers of reinforcing helical fibers around an elastomeric tube. This approach is versatile and robust, but it suffers from a critical disadvantage: cumbersome fabrication procedures. Wrapping long helical filaments around a cylindrical tube requires expensive equipment or excessive manual labor. To address this issue, we propose a new approach towards designing and constructing pneumatic actuators by exploiting the principle of kirigami, the ancient art of paper cutting. More specifically, we use “kirigami skins” — plastic sleeves with carefully arranged slit cuts — to replace the reinforcing helical fibers. This paper presents an initial investigation on a set of linear extension actuators featuring kirigami skins with a uniform array of cross-shaped, orthogonal cuts. When under internal pressurization, the rectangular-shaped facets defined by these cuts can rotate and induce the desired extension motion. Through extensive experiments, we analyze the elastic and plastic deformations of these kirigami skins alone under tension. The results show strongly nonlinear behaviors involving both in-plane facet rotation the out-of-plane buckling. Such a deformation pattern offers valuable insights into the actuator’s performance under pressure. Moreover, both the deformation characteristics and actuation performance are “programmable” by tailoring the cut geometry. This study lays down the foundation for constructing more capable Kirigami-skinned soft actuators that can achieve sophisticated motions.
Proceedings Papers
Proc. ASME. SMASIS2019, ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T03A012, September 9–11, 2019
Paper No: SMASIS2019-5708
Abstract
Current wearable technologies strive to incorporate more medical functionalities in wearable devices for tracking health conditions and providing information for timely medical treatments. Beyond tracking of a wearer’s physical activities and basic vital signs, the advancement of wearable healthcare devices aspires to continuously monitor health parameters, such as cardiovascular indicators. To properly monitor cardiovascular health, the wearables should accurately measure blood pressure in real-time. However, current devices on the market are not validated for continuous monitoring of blood pressure at a clinical level. To develop wearable healthcare devices such applications, they must be validated by considering various parameters, such as the effects of varying skin properties. Being located between the blood vessel and the wearable device, the skin can affect the sensor readings of the device. The primary goal of this study is to investigate the effect of skin property on the radial pulse measurements. To this end, a range of artificial vein-inserted skin samples with varying properties is fabricated using Magneto-Rheological Elastomers (MRE), materials whose mechanical properties can be altered by external magnetic fields. The samples include layers to simulate the structure of skin and a silicone vein for the pulse to pass through. Note that they are not intended to represent real human skin-vein properties but created to vary a range of stiffness properties to carry out the study. Experiments are performed using a cam system capable of generating realistic human pulse waveforms to pass through the samples. During the indentation testing, the sample is compressed using a dynamic mechanical analyzer (DMA) to record experienced surface pressure, allowing the pulse patterns to be studied. Various samples are used to probe the effects of base resin hardness, iron content, and magnetic field. A pressure sensor incorporated in the cam simulator is used to benchmark the internal pulse pressure of the vein while the DMA indents the sample in order to note the pulse pressures being passed through the sample. Test results show that the properties of the skin influence the resulting pulse behaviors, particularly the ratio of the recorded pulse pressures from the sensor and the DMA.
Proceedings Papers
Proc. ASME. SMASIS2019, ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T04A012, September 9–11, 2019
Paper No: SMASIS2019-5604
Abstract
A continuous-surface morphing airfoil is desirable for commercial aircraft in order to improve fuel efficiency, and due to the potential to morph the wing into a high-lift configuration for take-off and landing. Piezocomposite actuators have shown to be a feasible strategy for camber morphing in small unmanned fixed-wing aircraft with a Reynold’s number in the range of 50,000 to 250,000. As an extension, this paper presents a theoretical framework and results for morphing in single and multi-segment natural laminar flow airfoils with a maximum Reynold’s number of 825,000. The airfoils presented employ a continuous inextensible surface. To achieve morphing, piezocomposite actuating elements are applied on the suction and pressure surfaces of the airfoils. The geometric properties of the airfoils are determined using a genetic algorithm optimization method with a migration strategy in order to maintain population diversity. The algorithm optimizes independently the substrate thicknesses for the nominal airfoil, the leading edge, and the piezocomposite bonded surfaces. In addition, positions and voltages for each piezocomposite actuators are optimized. The genetic algorithm uses an objective function to maximize the change in coefficient of lift to morph the airfoil from its baseline (i.e. cruise) state to the high-lift state. Analysis is performed using a coupled fluid-structure interaction method assuming static aero-elastic behavior. Optimization is followed by a parametric analysis to examine lift, drag, and lift-to-drag ratio of the airfoils over their full operational range. The optimization is performed on a symmetric, asymmetric, and the aft element of a slotted multi-segment airfoil to examine the capabilities of induced-strain actuation at high dynamic pressures.
Proceedings Papers
Proc. ASME. SMASIS2019, ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T06A014, September 9–11, 2019
Paper No: SMASIS2019-5696
Abstract
Diabetics often have neuropathy that prevents them from noticing developing foot ulcers. Pressure sensors can detect areas with abnormally high pressure, allowing earlier detection, prevention, and treatment of developing ulcers. Accurate pressure sensors are often limited to bulky or stationary systems, or have other limitations such as lack of accuracy, slow response times, and cost. This paper explains the fabrication of a prototype system using a bilayer flexible sensor for better accuracy in measuring pressure. The sensor is made of an exfoliated graphite film on a latex substrate and is layered with rubber padding to allow deformation. It is connected to an electronic system that reads changing resistance due to pressure and maps the applied pressure. This system might be a low cost, accurate, and durable alternative to current systems.
Proceedings Papers
Proc. ASME. SMASIS2019, ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T03A009, September 9–11, 2019
Paper No: SMASIS2019-5614
Abstract
We propose a planar hydrogel-based micro-valve design which is modeled as a library element for Matlab Simulink. For this test case, a pressure pump (voltage source) in series with a micro-valve model (variable fluidic resistance) is built up. The micro-valve subsystem is separated in four main parts. Based on the applied temperature stimulus, the equilibrium length is determined according to an experimentally verified fit function. Furthermore, the equilibrium length considers a static hysteresis effect which is modeled in analogy to the saturation of magnetization in electric transformers. In a second step, the transient behavior follows a first order differential equation, but the cooperate diffusion coefficient is size dependent affecting the rise time of the system. This causes a faster swelling than deswelling of the hydrogel. In the third section, the stiffness property is implemented to calculate the maximum sealing pressure and the resulting gap between the hydrogel and the wall. The fluidic resistance of the micro-valve considers a three-dimensional geometry and is calculated based on a look-up table, extracted from a fluid-structure-interaction (FSI) model generated from a finite element structure. The proposed model allows a full description of the fluidic hydrogel-based micro-valve and is part of an upcoming microfluidic toolbox for Matlab Simulink containing passive elements and optional chemical reactions like mixing fluids and enzyme reactions for future applications.
Proceedings Papers
Proc. ASME. SMASIS2019, ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T06A015, September 9–11, 2019
Paper No: SMASIS2019-5698
Abstract
Electronic skins, or e-skins, are electronic devices capable of sensing physical interactions such as strain, temperature, or pressure. These e-skins are of interest in a variety of fields including robotics, structural health monitoring, and medicine. E-skins should measure strains over a larger range of elongation than traditional strain sensors could. This paper explores the synthesis of a flexible biaxial strain sensor for large surface strain measurement. The sensor is made by spraying an exfoliated graphite and latex mixture onto a latex substrate to form a 4 × 4 grid of electrically conductive strips. Electrodes are connected to each sensor to collect data on deformation induced voltage difference. Two setup geometries were characterized, the behavior of a single strip in each direction in a one by one configuration as well as the behavior of a four by four setup that can measure a two-dimensional strain field. The characteristics of the sensor is studied by attaching it on a tensile testing specimen. When the sensor is subjected to strain along one or both of the two measurement axes, the voltage difference can be recorded using Arduino. The voltage drop was normalized and used to construct a strain distribution plot in MATLAB to determine the highly strained location. In addition to characterizing the behavior of the sensor, the dispersion of the exfoliated graphite in the latex is also studied using optical microscopy. The sensor is made from inexpensive materials and was able to measure large strain that cannot be achieved with commercially available strain gauges.
Proceedings Papers
Proc. ASME. SMASIS2019, ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T02A014, September 9–11, 2019
Paper No: SMASIS2019-5747
Abstract
Dielectric elastomers (DE) are regarded as a potential alternative to conventional actuator technologies. They feature low weight, high strains and low material costs. Their scope of application ranges from sensors, energy generators, smart textiles to biomimetic robots and much more. A few concepts of loudspeakers using DE have been demonstrated by the research community. One of the disadvantages of previously concepts was the need for mechanical bias (e.g. by air pressure). This work proposes a new concept of loudspeaker, which does not need prestretch or other means of mechanical bias. Buckling dielectric elastomer transducers (BDET) use the area expansion of actuated DE to buckle up. This mechanism is used to construct a millimeter-scale loudspeaker with good frequency response in the upper frequency range. The concept is implemented using automatically fabricated multi-layer membranes. The multilayer structure allows to generate more force and has higher flexural rigidity than a single-layer setup. Samples with different amount of layers are fabricated and an analytical model is derived. Measurements of the static deflection, the frequency response and the total harmonic distortion validate the model. The small scale of the speaker allows it to be installed in large arrays and thus might offer a hardware platform for high-resolution beam forming or wave field synthesis.
Proceedings Papers
Proc. ASME. SMASIS2019, ASME 2019 Conference on Smart Materials, Adaptive Structures and Intelligent Systems, V001T03A011, September 9–11, 2019
Paper No: SMASIS2019-5674
Abstract
Tall and slender buildings often endure disturbances resulting from winds composed of various mean and fluctuating velocities. These disturbances result in discomfort for the occupants as well as accelerated fatigue life cycles and premature fatigue failures in the building. This work presents the development of a smart morphing façade (Smorphaçade) system that dynamically alters a buildings’ external shape or texture to minimize the effect of wind-induced vibrations on the building. The Smorphacade system is represented in this work by a series of plates that vary their orientation by means of a central controller module. To validate the simulation, a simple NACA0012 airfoil is simulated in a stream of air at a Reynolds number (RE) of 2 million. The pressure and viscous force profiles are captured to plot the variation of the lift force for different angles of attack that are then validated using published experimental airfoil data. After validation, the airfoil is attached to a linear spring-damper combination and is allowed to translate vertically without rotation according to the force profile captured from the surrounding air stream. A PID controller is developed to equilibrate the vertical position of the airfoil by altering its angle of attack. The model and its utility functions are implemented as an OpenFOAM ® module (MSLSolid). Thereafter, the model is expanded to handle a planar case of a building floor carrying 4 controllable plates. The forces on the building profile are summed at the centroid of the building and the windward rigid body motion of the floor is estimated by reflecting the horizontal force component on a Finite Element (FE) model of the building. The time series information of the force acting on the building and the resulting oscillations are captured for exhaustive combinations of the plate angles. This data is used to build a lookup table that gives the best plate configuration for a given wind condition. A controller operates in real-time by searching the lookup table using readings of the wind condition. Preliminary results show a 94% reduction in the amplitudes of wind-induced vibrations.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 2: Mechanics and Behavior of Active Materials; Structural Health Monitoring; Bioinspired Smart Materials and Systems; Energy Harvesting; Emerging Technologies, V002T06A008, September 10–12, 2018
Paper No: SMASIS2018-8078
Abstract
Computational modeling, instrumented linkages, optical technologies, MRI, and radiographic techniques have been widely used to study knee motion after total knee replacement (TKR) surgery. Information provided by these methods has helped designers to develop implants with better clinical performance and surgeons to obtain an improved understanding of the stability and mobility of the joint. Correspondingly, overall patient satisfaction with respect to the reduction in pain and recovery of normal functioning of the joint has been improving. However, about 20% of patients are still not fully satisfied with their surgical outcomes. The main obstacle in the current state-of-the-art is that a comprehensive post-operative understanding of knee balance is still unavailable, mostly due to a lack of in vivo data collected from the joint after surgery. This work presents an attempt to develop a self-powered instrumented knee implant for in vivo data acquisition. The knee sensory system in this study utilizes several embedded piezoelectric transducers in the tibial bearing of the knee replacement in order to provide sensing and energy harvesting capabilities. Through a series of analytical modeling, finite element simulation, and experimental testing, the performance of the suggested system is evaluated and a dimensionally optimized design of an instrumented TKR is achieved. More specifically, a comprehensive platform is established in order to combine the knowledge of embedded piezoelectric sensors and energy harvesters, musculoskeletal modeling of the knee joint, multiphysics finite element modeling, additive manufacturing techniques, image processing, and experimental knee loading simulation in order to achieve the experimentally validated and optimized instrumented knee implant design. The cumulative work presented in this article encompasses three main studies performed on the sensing performance of the proposed design: first, preliminary parametric studies of the effect of local dimensional and material parameters on the electromechanical behavior of the embedded sensory system; second, investigation of the ability to sense total force and center of pressure location; and third, evaluation of an enhanced system with the ability to sense compartmental forces and contact locations. Additionally, the energy harvesting capacity of the system is investigated to ensure the achievement of a fully self-powered sensory system. Results obtained from the experimental analysis of the system demonstrate the successful sensing and energy harvesting performance of the designs achieved in this study.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation, and Control of Adaptive Systems; Integrated System Design and Implementation, V001T04A002, September 10–12, 2018
Paper No: SMASIS2018-7920
Abstract
Self-fitting is the ability of a wearable, garment or body-mounted object to recover the exact shape and size of the human body. Self-fitting is highly desirable for wearable applications, ranging from medical and recreational health monitoring to wearable robotics and haptic feedback, because it enables complex devices to achieve accurate body proximity, which is often required for functionality. While garments designed with compliant fabrics can easily accomplish accurate fit for a range of body shapes and sizes, integrated actuators and sensors require fabric stiffness to prevent drift and deflection from the body surface. This paper merges smart materials and structures research with anthropometric analysis and functional apparel methodologies to present a novel, functionally gradient self-fitting garment designed to address the challenge of achieving accurate individual and population fit. This fully functional garment, constructed with contractile SMA knitted actuator fabrics, exhibits tunable %-actuation contractions between 4–50%, exerts minimal on-body pressure (≤ 1333Pa or 10 mmHg), and can be designed to actuate fully self-powered with body heat. The primary challenge in the development of the proposed garment is to design a functionally gradient system that does not exert significant pressure on part of the leg and/or remain oversized in others. Our research presents a new methodology for the design of contractile SMA knitted actuator garments, describes the manufacture of such self-fitting garments, and concludes with an experimental analysis of the garment performance evaluated through three-dimensional marker tracking.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation, and Control of Adaptive Systems; Integrated System Design and Implementation, V001T04A010, September 10–12, 2018
Paper No: SMASIS2018-7949
Abstract
Early research on a new concept for a morphing system based on unit structures or cells containing pressurized fluid is presented in this article. The motivation stems from the desire to achieve 3D smooth variations with multiple degrees of freedom and variations in surface area. Such a cell is composed of a hybrid between elastomeric material and stiffening material, creating an orthotropic system. When connected in a network of cells, the morphing system is highly integrated in terms of the components of the skin, substructure and actuation means. Numerical predictions of small simple prismatic cells show a force and axial strain capability of above 200 N and 14% respectively for typical elastomeric and stiffening materials at 8 bar pressure. PolyJet™ additively-manufactured models of wings show how such actuators can be integrated into aircraft structures, including when 3D geometry is highly challenging. These additively-manufactured models were operated at low pressures in the order of 0.5 bar, and a number of open questions on the design, manufacture and operation of such structures are discussed along with intended future work towards higher grade materials and working pressures.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation, and Control of Adaptive Systems; Integrated System Design and Implementation, V001T01A018, September 10–12, 2018
Paper No: SMASIS2018-8097
Abstract
Additive manufacturing has emerged as an alternative to traditional manufacturing technologies. In particular, industries like fluid power, aviation and robotics have the potential to benefit greatly from this technology, due to the design flexibility, weight reduction and compact size that can be achieved. In this work, the design process and advantages of using 3D printing to make soft linear actuators were studied and highlighted. This work explored the limitations of current additive manufacturing tolerances to fabricate a typical piston-cylinder assembly, and how enclosed bellow actuators could be used to overcome high leakage and friction issues experienced with a piston-cylinder type actuator. To do that, different 3D printing technologies were studied and evaluated (stereolithorgraphy and fused deposition modeling) in the pursuit of high-fidelity, cost-effective 3D printing. The initial attempt consisted of printing the soft actuators directly using flexible materials in a stereolithography-type 3D printer. However, these actuators showed low durability and poor performance. The lack of a reliable resin resulted in the replacement of this material by EcoFlex ® 00-30 silicone and the use of a 3D printed mold to cast the actuators. These molds included a 3-D printed dissolvable core inside the cast actuator in order to finish the manufacturing process in one single step. An experimental setup to evaluate the capabilities of these actuators was developed. Results are shown to assess the steady-state and the dynamic characteristics of these actuators. These tests resulted into the stroke-pressure and stroke-time responses for a specific load given different proportional valve inputs.
Proceedings Papers
Proc. ASME. SMASIS2018, Volume 1: Development and Characterization of Multifunctional Materials; Modeling, Simulation, and Control of Adaptive Systems; Integrated System Design and Implementation, V001T04A004, September 10–12, 2018
Paper No: SMASIS2018-7939
Abstract
Researchers and engineers design modern aircraft wings to reach high levels of efficiency with the main outcome of weight saving and airplane lift-to-drag ratio increasing. Future commercial aircraft need to be mission-adaptive to improve their operational efficiency. Twistable trailing edge could be used to improve aircraft performances during climb and off-design cruise conditions in response to variations in speed, altitude, air temperature, and other flight parameters. Indeed, “continuous” span-wise twist of the wing trailing edge could provide significant reduction of the wing root bending moment through redistribution of the aerodynamic load leading to an increase of the payload/structural weight ratio. Within the framework of the Clean Sky 2 (CS2) European research project, the authors focused on the preliminary design of a full-scale composite multifunctional tab retrofitting the outboard morphing Fowler flap of a turboprop regional aircraft. The investigation domain of the novel device is equal to 5.15 meters in span-wise direction and 10% of the local wing chord. The structural and kinematic design process of the actuation system is completely addressed: two rotary electromechanical motors, placed in the root and tip flap sections, are required to activate the inner mechanisms enabling delta twist angles up to 10 degrees along the outboard region when the flap is stowed in the wing. The structural layout of the thin-walled closed-section composite tab represents a promising concept to balance the conflicting requirements between load-carrying capability and shape adaptivity in morphing lightweight structures. The main design parameters are optimized to minimize actuation torque required for twisting while providing proper flexural rigidity to withstand limit aerodynamic pressure distributions for large airplanes. Finally, the embedded system functionality of the actuation system coupled with the composite wing trailing edge is fully investigated by means of detailed finite element simulations. Results of actuation system performances, and aeroelastic deformations considering operative aerodynamic loads demonstrate the potential of the proposed structural concept to be energy efficient, and lightweight for real aircraft implementation.