Browsing by Author "Dunne, Lucy"
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Item Comparative Assessment of Wearable Surface EMG Electrode Configurations for Biomechanical Applications(49th International Conference on Environmental Systems, 2019-07-07) Lee, J. Walter; Golgouneh, Alireza; Dunne, LucyObtaining accurate biomechanical information within rigid, constrained compartments such as spacesuits can be challenging and labor-intensive, due to the obstacles of bulk and mass involved with sensor placements. Inspired by the current challenges in measuring astronaut biomechanics and in designing mobility-assistive robotics, this study investigates the feasibility of using soft, flexible wearable surface electromyography (EMG) sensors. In this study, anti-slip arm bands with textile-friendly metal-snap electrodes were used to collect EMG signals from biceps brachii and triceps brachii muscle activities, with conventional adhesive disposable solid-gel electrodes measuring the same muscle activities simultaneously. To compare the quality of signals obtained from the wearable EMG electrode configuration to the signals obtained from the conventional EMG electrodes, 40 trials that were collected with two subjects were analyzed by extracting 11 time-domain EMG features. These EMG features from two distinct signal sources were compared by using the non-segmentation method, the overlapping segmentation method, and the disjoint segmentation method. Results showed that comparisons were non-significant in most feature comparisons using non-segmentation method, and all comparisons were non-significant in both EMG signal segmentation methods, validating the feasibility of reliable and accurate signal collection with the dry metal-snap wearable electrodes and the promise in real-time application of the wearable EMG electrode configuration. Implications and limitations of the current study results are also discussed.Item Development and Characterization of a Mannequin-Based Method for Fit Measurement of Wearable Systems(48th International Conference on Environmental Systems, 2018-07-08) Compton, Crystal; Berglund, Mary Ellen; Chen, Jin; Brubaker, Derek; Bunyard, Clayton; Dunne, LucyMeasuring fit of a wearable system on a body is a perennial challenge in the development of all kinds of on-body systems including clothing and everyday products. For human spaceflight applications, aspects of fit that relate to contact between the body and the garment are especially important. Wearable sensors and electrodes are the most common approach to sensing this kind of functional fit, however, they also present challenges in the form of reduced accuracy when applied to soft, unpredictable body surfaces and observer effects as the sensor structure alters the distribution of force and contact over the skin. Augmented mannequins offer an alternative to human-based evaluation. While mannequins are more limited in anthropometric variability, they can provide a controlled testing environment in which fit variables can be better isolated prior to human testing. In previous work we have established an electrical method for measuring contact between the body and a worn garment. Here, we extend that concept through implementation using an augmented mannequin, which improves the efficiency of testing and allows body/garment contact to be more specifically characterized. Importantly, our approach maintains the continuous mechanical properties of the mannequin, designed to be similar to human tissue. This study presents the development and validation process for mannequin- and garment-integrated electrodes, as well as results of an initial pilot test measuring body contact over repeated donning/doffing of two garment and garment-electrode structures on the augmented mannequin.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 Anthropometric Variability and Dimensional Change Due to Posture on Orthostatic Intolerance Garments(47th International Conference on Environmental Systems, 2017-07-16) Granberry, Rachael; Dunne, Lucy; Holschuh, BradleyOrthostatic intolerance garments (OIG) (e.g., the anti-gravity suit (AGS) worn by astronauts during earth reentry) produce therapeutic pressures on the body through inflation or through pattern reduction (i.e., undersized knit garments that stretch when donned). While pneumatic garments (AGS) are currently employed by NASA, skin-tight OIGs allow for increased mobility and could improve astronaut safety in the event of an off-nominal event. Undersized OIGs have been explored as alternatives to inflatable systems; however, they are static and designed from a series of limb circumferences taken from the standing position. Lower body radii are not fixed dimensions - but rather dynamic dimensions dependent on body posture, composition, and topography; therefore, functional pressures exerted on the body in a seated posture (i.e. during earth reentry) are unpredictable and could produce unanticipated blood pooling if radii increase. This paper serves as an investigation of the variability and dynamics of the human body in relation to OIGs. To quantify body variability due to posture change, anthropometrics from 1264 North American women were gathered from the Civilian American & European Surface Anthropometry Resource (CAESAR) database. Four circumferential measurements were collected from a sample of the CAESAR population (n=80) at the ankle, calf, knee, and thigh. A paired t-test was conducted to determine the difference between standing and sitting mean circumferences for each region of the leg. Descriptive statistics were calculated to determine the range of percentage change within the sample statistics. The study concludes that leg radii are complex and fluctuate non-uniformly from the thigh to the ankle between body postures (i.e. standing to sitting). Future OIG design will require an incorporation of anthropometric analysis to account for dimensional variability to maintain effective and predictable medically therapeutic pressure on the body.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 Pilot Investigation of a Novel Technique for Measuring Dynamic Body-Garment Contact(46th International Conference on Environmental Systems, 2016-07-10) Compton, Crystal; Dunne, LucyLiquid cooled garments are a fundamental aspect of regulating astronaut’s core body temperature during launch and entry and EVAs. They manage the thermal energy created by the body, to ultimately regulate the body’s core temperature and maintain a comfortable and safe working environment for the astronaut. Liquid cooled garments astronauts wear rely on conduction to transfer body heat. Heat from the body is conducted to a garment that contains cold flowing water. It is crucially important to have contact between the garment and body at all times and in all locations in order for the garment to work most efficiently using conduction. To effectively re-design a liquid cooling garment to promote good contact, it is important to first be able to diagnose where the problem areas exist. Therefore, a method to measure where the garment touches the body or not during movement could provide answers to not only improving the thermal regulation, but also the fit, comfort, and mobility of liquid cooled garments for future space exploration and human spaceflight. Existing methods of measuring the relationship between the body and garment rely on static imaging and are not able to measure contact while the body (and garment) is in motion. Here we present a novel method based on a ‘switch’-like principle, in which contact with the grounded body completes a circuit to close a switch attached to the digital input of a microcontroller. Working principle and early results of this method are discussed.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.