Browsing by Author "Holschuh, Brad"
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Item Design and Control of Reduced Power Actuation for Active-Contracting Orthostatic Intolerance Garments(49th International Conference on Environmental Systems, 2019-07-07) Granberry, Rachael; Padula, Santo; Eschen, Kevin; Abel, Julianna; Holschuh, BradActive-contracting fabrics are a developing innovation that could revolutionize compression garment technology, notably aerospace orthostatic intolerance garments (OIG), by contracting on demand. Traditional fabric structures exhibit surface-wide distributed and/or functionally graded contractile actuation through the integration of materials with shape memory (SM) properties. Prior research has found that active-contracting fabrics, specifically weft knit garter fabric architectures constructed with shape memory alloy (SMA) filaments, can apply 8-30 mmHg on the body (single-layer construction) or 15-65 mmHg (double layer construction), depending on body radius (i.e. average ankle girth, SizeUSA women; average torso girth, SizeUSA men). Prior garment prototyping and performance validation efforts have been conducted with commercially available Flexinol wire with an actuation finish temperature of 90°C, a temperature that is not appropriate proximal to the human body. While other chemistries of SMA having lower actuation temperatures commonly used for medical devices inside the human body (T ≈ 37°C) are available, SMA material is currently not designed specifically for actuation control against the human skin (T ≈ 31°C). This research characterizes and validates a novel SMA material designed in collaboration with Fort Wayne Metals specifically for actuation adjacent to the surface of the body. Through traditional SMA material testing paired with experimental temperature-force-displacement testing, we present data validating material functionality in the design of a future OIG. The manuscript presents evidence for a future OIG that is donned in an oversized and compliant state, heated momentarily above ambient skin temperature to initiate actuation, and remains actuated post-applied heat indefinitely. The result is an OIG that requires almost no operating power that could be doffed through zipper releases and placed in a sub-zero chamber to return to the “off” state before reuse. Preliminary findings will be presented to characterize the performance of the material in future aerospace compression systems.Item Development and Characterization of Modular Elastic Switches for Sensing and Control of Active Compression Garments(48th International Conference on Environmental Systems, 2018-07-08) Schleif, Nicholas; Pettys-Baker, Robert; Lee, J. Walter; Berglund, Mary; Ozbek, Simon; Utset-Ward, Sophia; Dunne, Lucy; Holschuh, BradAstronauts frequently suffer from orthostatic intolerance (OI) when returning to earth. Conventional wearable interventions for treating or preventing OI exhibit limited controllability (in elastic stockings) or limited mobility (in pneumatically inflatable garments). A new promising method to replace inflatable and elastic stockings for OI treatment is to implement dynamically controllable, conformal OI garments using integrated active materials such as shape memory alloys (SMAs). These garments constrict when thermally (or electrically) stimulated, resulting in a compressive force on the body when worn. This investigation builds on previous work in active compression garment development, introducing a novel feedback control system to provide constant garment tension without the need for precise, real-time pressure sensing or power control. This is accomplished using in-line tension switch mechanisms—switches that break the local actuator control circuit above a prescribed circumferential tension (which we define as the “critical tension”)—enabling passive feedback control of garment tension/pressure during use. A study was conducted to compare the functional performance (critical tension, hysteresis, reliability) of three switch architectures (referred to in this study as copper plate, spring, and reed switches). Critical tension was measured over multiple loading/displacement cycles (50 cycles at 5s per cycle, and 100 cycles at 35s per cycle), and three prototypes of each architecture were manufactured and tested. Two architectures—the copper plate and spring switch samples—showed promise in their performance (as measured by the reliability and repeatability of the measured critical tension over repeated loading cycles), though the switch behavior varied significantly between architectures and between samples. This approach to passively managing SMA-based contractile forces holds promise for any system that requires active tension control, including OI garments, as well as for advanced compression systems such as Mechanical Counter-Pressure (MCP) spacesuits.Item Development of Elastomer-Strain Gauge Composite for On-Body Dynamic Force Measurement(47th International Conference on Environmental Systems, 2017-07-16) Berglund, Mary Ellen; Foo, Esther; Dunne, Lucy; Holschuh, BradSensing force on the body is useful for a variety of aerospace applications. In extravehicular activity (EVA) suits, sensing force on the body is important to determine when and where a rigid suit structure comes into contact with the astronaut. In intravehicular activity (IVA) compression garments, real-time force sensing could help improve current garment performance, or even enable new forms of compression therapy. In this paper we describe the development of a novel elastomer-strain gauge composite designed to unobtrusively measure contact force on the body. The sensor, which combines a strain-sensitive conductive cover-stitched trace with a compliant elastomer matrix, is engineered to respond to normal force by inducing repeatable and predictable strain in the conductive trace. Consequently, the electrical resistance of the trace changes with applied force, leading to useful sensing capability. A parametric design study of two manufacturing methods and elastomer material stiffnesses (Shore value) was performed to assess the effects of these parameters on the elastomer-strain gauge composite performance. The two manufacturing methods differ in terms of ease of manufacturing. The results of this study indicated that the ‘direct-stitched’ manufacturing method with a lower Shore value had greater performance than the ‘layered-assembly’ manufacturing method in terms of sensor characteristics, evaluated based on polynomial model fitting and long term-repeatability. This type of novel elastomer-strain gauge composite enables unobtrusive on-body normal force sensing, which can benefit astronauts during IVA/EVA, as well as additional applications where on body force sensing is valuable.Item Effects of E-Textile Circuit Components on Signal Quality for Wearable Sensing Applications(51st International Conference on Environmental Systems, 7/10/2022) Golgouneh, Alireza; Holschuh, Brad; Dunne, Lucy; Eshima, SamuelWearable sensors are an emerging area of interest for next-generation spacesuits. Wearable sensors can be used to measure things like physiological signals or forces experienced by the body to obtain information about crew members� wellness, mobility, and body position. Obtaining this information within rigid, constrained environments such as spacesuits can be challenging and labor-intensive. Requirements of comfort and conformability are often at odds with both functional and durability requirements involved with wearing a sensing layer underneath a stiff suit. Using E-textile components such as conductive threads and rubbers instead of typical electrical components can help manage the comfort/durability requirements of a sensing baselayer for space suit applications. However, flexible e-textile components may influence circuit integrity and sensor signal quality, and lead to inaccurate measurement. This study seeks to quantify the effects of various approaches to integrating soft textile-based electrical connections (such as threads and rubbers) on the responses of soft strain sensors. Changes in Signal to Noise Ratio (SNR) for textile-based piezoresistive and capacitive strain sensors were measured under wearability conditions including three e-textile lead configurations, a body curvature condition, and a skin proximity condition. Effects were most significant for the capacitive sensor. All lead types maintained strong SNR for the piezoresistive sensor, and body curvature did not induce significant changes. Skin proximity (and particularly motion artifacts) affected the capacitive sensor response, but effects were smallest when using conductive rubber leads.Item Preliminary Investigation of the Design of a Mechanically Antagonistic, Actuating Countermeasure Garment(2020 International Conference on Environmental Systems, 2020-07-31) Granberry, Rachael; Abel, Julianna; Holschuh, BradCountermeasure garments are worn by all NASA crew during Earth reentry, landing, and egress in accordance with NASA-STD-3001. These lower-body compression garments are designed to mitigate lower body blood pooling, which can impair a crew member’s ability to complete critical landing tasks. The likelihood of cardiovascular deconditioning increases with mission duration; therefore, countermeasure garments are a critical safeguard to astronaut health as we push the bounds of space exploration into 3+ year missions (e.g. Journey to Mars). Current on-body compression technologies are either a mobility hazard, such as tethered inflatable compression systems, or uncomfortable and cumbersome due to their static design, such as undersized, elastane garments. Shapeshifting fabrics enable an alternative solution – compression garments that can be donned in a loose, relaxed configuration and contract and stiffen in response to small changes in temperature. Prior work has found that knitted actuator fabrics have actuation pull forces capable of providing suitable cardiovascular protection during astronaut landing activities. Additionally, prior work has presented and validated the use of custom SMA chemistries that can actuate below 40℃, the NASA-STD-3001 maximum allowable touch temperature. This work presents a preliminary investigation of the design of an actuating orthostatic intolerance garment using these high-force, low-temperature actuator fabrics in parallel with passive elastane fabrics to form a mechanically antagonistic wearable system. This mechanically antagonistic wearable system will be conceptually defined and built in the form of a prototype calf sleeve with two goals in mind. First, we present the first implementation of a new design methodology and use operation to observe the functional challenges of this mechanically antagonistic actuating countermeasure system. Secondly, we present system performance data, covering 2D mechanical performance testing and on-body user compression testing. The resulting trial run documentation and feedback paves the way for future, full garment actuating countermeasure garment prototypes.Item Towards Large-area On-body Force Sensing Using Soft, Flexible Materials: Challenges of Textile-Based Array Sensing(2020 International Conference on Environmental Systems, 2020-07-31) Compton, Crystal; Golgouneh, Alireza; Holschuh, Brad; Dunne, LucyOn-body force-sensing presents important opportunities for understanding of how the human body moves and interfaces with wearable systems such as space suits. Measuring these body-space suit interactions has been a continuous challenge due to the enclosed nature of the suit as well as limitations of common sensor technology. Textile-based wearable sensors offer the possibility of comfortable, unobtrusive monitoring inside the suit. Further, most typical force sensors only provide information for a single point, while for wearable applications, it is useful to be able to measure multiple points over a larger area to obtain a distribution of force measurements. Here, we investigate the challenges of textile-based sensing arrays through the assessment of two force-sensing array architectures: (1) isolated-cell, and (2) connected-cell. Controlled calibration and force-sensing tests have illuminated challenges stemming from crosstalk and mechanical deformation of the sensing array that influence sensor response repeatability and accuracy. We present an assessment of these challenges including implementation of mitigation approaches, and discuss their implications for on-body textile-based sensing.