Browsing by Author "Lee, J. Walter"
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
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 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.