Engineering topics

Lewandowski, Beth

Publications and source records attributed to Lewandowski, Beth.

18 records

NASA NTRS2019

Human Factors Applications of Biomechanical Modeling

Biomechanical data collection and modeling has applications to the field of human factors. Specifically, motion data can be used to determine the operational volume necessary for performing a task. The operational volume assessment can be performed in order to determine how much volume is needed to perform the task or if task performance can be contained and adequately performed within an allocated volume. Motion and external force data, along with computational modeling techniques, can be used to estimate the internal loading produced during performance of a task. Internal loading estimates can be used to determine if an adequate stimulus is generated for maintenance of musculoskeletal health and also for comparison to injury thresholds to determine injury risk during task performance.

Lewandowski, Beth↗

NASA NTRS2017

Sensitivity Analysis of the Bone Fracture Risk Model

Introduction: The probability of bone fracture during and after spaceflight is quantified to aid in mission planning, to determine required astronaut fitness standards and training requirements and to inform countermeasure research and design. Probability is quantified with a probabilistic modeling approach where distributions of model parameter values, instead of single deterministic values, capture the parameter variability within the astronaut population and fracture predictions are probability distributions with a mean value and an associated uncertainty. Because of this uncertainty, the model in its current state cannot discern an effect of countermeasures on fracture probability, for example between use and non-use of bisphosphonates or between spaceflight exercise performed with the Advanced Resistive Exercise Device (ARED) or on devices prior to installation of ARED on the International Space Station. This is thought to be due to the inability to measure key contributors to bone strength, for example, geometry and volumetric distributions of bone mass, with areal bone mineral density (BMD) measurement techniques. To further the applicability of model, we performed a parameter sensitivity study aimed at identifying those parameter uncertainties that most effect the model forecasts in order to determine what areas of the model needed enhancements for reducing uncertainty. Methods: The bone fracture risk model (BFxRM), originally published in (Nelson et al) is a probabilistic model that can assess the risk of astronaut bone fracture. This is accomplished by utilizing biomechanical models to assess the applied loads; utilizing models of spaceflight BMD loss in at-risk skeletal locations; quantifying bone strength through a relationship between areal BMD and bone failure load; and relating fracture risk index (FRI), the ratio of applied load to bone strength, to fracture probability. There are many factors associated with these calculations including environmental factors, factors associated with the fall event, mass and anthropometric values of the astronaut, BMD characteristics, characteristics of the relationship between BMD and bone strength and bone fracture characteristics. The uncertainty in these factors is captured through the use of parameter distributions and the fracture predictions are probability distributions with a mean value and an associated uncertainty. To determine parameter sensitivity, a correlation coefficient is found between the sample set of each model parameter and the calculated fracture probabilities. Each parameters contribution to the variance is found by squaring the correlation coefficients, dividing by the sum of the squared correlation coefficients, and multiplying by 100. Results: Sensitivity analyses of BFxRM simulations of preflight, 0 days post-flight and 365 days post-flight falls onto the hip revealed a subset of the twelve factors within the model which cause the most variation in the fracture predictions. These factors include the spring constant used in the hip biomechanical model, the midpoint FRI parameter within the equation used to convert FRI to fracture probability and preflight BMD values. Future work: Plans are underway to update the BFxRM by incorporating bone strength information from finite element models (FEM) into the bone strength portion of the BFxRM. Also, FEM bone strength information along with fracture outcome data will be incorporated into the FRI to fracture probability.

mathematical models↗

NASA NTRS2017

Implicit Formulation of Muscle Dynamics in OpenSim

Astronauts lose bone and muscle mass during spaceflight. Exercise countermeasure is the primary method for counteracting bone and muscle mass loss in space. New spacecraft exercise device concepts are currently being developed for the NASAs new crew exploration vehicle. The NASA Digital Astronaut Project (DAP) uses computational modeling to help determine if the new exercise devices will be effective as countermeasures. The NASA Digital Astronaut Project is developing the ability to utilize predictive simulation to provide insight into the change in kinematics and kinetics with a change in device and gravitational environment (1-g versus 0-g). For example, in space exercise the subject's body weight is applied in addition to the loads prescribed for musculoskeletal maintenance. How and where these loads are applied obviously directly impacts bone and tissue loads. Additionally, due to space vehicle structural requirements, exercise devices are often placed on vibration isolation systems. This changes the apparent impedance or stiffness of the device as seen by the user. Data collection under these conditions is often impractical and limited. Predictive modeling provides a means to have a virtual subject to test hypotheses. Predictive simulation provides a virtual subject for which we are able to perform studies such as sensitivity to device loading and vibration isolation without the need for laboratory kinematic or kinetic test data.Direct Collocation optimization provides an efficient means to perform task based optimization and predictive modeling. It is relatively straight forward to structure a physical exercise task in a Direct Collocation mathematical formulation: perform a motion such that you start at an initial pose, achieve a given amount of deflection i.e a squat, return to the initial pose, and minimize muscle activation cost. Direct Collocation is advantageous in that it does not require numerical integration to evaluate the objective function. Instead, the system dynamics are transformed to discrete time and the optimizer is constrained such that the solution is not considered to be a valid unless the dynamic equations are satisfied at all time points. The simulation and optimization are effectively done simultaneously. Due to the implicit integration, time steps can be more coarse than in a differential equation solver. In a gait scenario this means that that the model constraints and cost function are evaluated at 100 nodes in the gait cycle versus 10,000 integration steps in a variable-step forward dynamic simulation. Furthermore, no time is wasted on accurate simulations of movements that are far from the optimum. Constrained optimization algorithms require a Jacobian matrix that contains the partial derivatives of each of the dynamic constraints with respect to of each of the state and control variables at all time points. This is a large but sparse matrix. An implicit dynamics formulation requires computation of the dynamic residuals f as a function of the states x and their derivatives, and controls u:f(x, dxdt, u) 0If the dynamics of musculoskeletal system are formulated implicitly, the Jacobian elements are often available analytically, eliminating the need for numerical differentiation; this is obviously computationally advantageous. Additionally, implicit formulation of musculoskeletal dynamics do not suffer from singularities from low mass bodies, zero muscle activation, or other stiff system or

physical exercise↗

NASA NTRS2016

A Flexible Method for Producing F.E.M. Analysis of Bone Using Open-Source Software

Individuals who experience decreases in load-bearing bone densities can be subject to a higher risk of bone fracture during daily activity. Astronauts may lose up to nine percent of their load-bearing bone density for every month they spend in space [1]. Because of this, specialized countermeasures reduce percent loss in bone density and reduce fracture risk upon returning to Earth. Astronauts will typically not be at risk for fracture during spaceflight, because of the lesser loads experienced in microgravity conditions. However, once back on Earth, astronauts have an increased risk for bone fracture as a result of weakened bone and return to 1G conditions [2]. It is therefore important to understand the significance of any bone density loss in addition to developing exercises in an attempt to limit losses in bone strength. NASA seeks to develop a deeper understanding of fracture risk through the development of a computational bone strength model to assess the bone fracture risk of astronauts pre-flight and post-flight. This study addresses the several key processes needed to develop such strength analyses using medical image processing and finite element modeling.

biomechanics↗

NASA NTRS2016

OpenSim Model Improvements to Support High Joint Angle Resistive Exercising

Bioengineering↗

NASA NTRS2016

Utilizing Commercial Hardware and Open Source Computer Vision Software to Perform Motion Capture for Reduced Gravity Flight

Long duration space travel to Mars or to an asteroid will expose astronauts to extended periods of reduced gravity. Since gravity is not present to aid loading, astronauts will use resistive and aerobic exercise regimes for the duration of the space flight to minimize the loss of bone density, muscle mass and aerobic capacity that occurs during exposure to a reduced gravity environment. Unlike the International Space Station (ISS), the area available for an exercise device in the next generation of spacecraft is limited. Therefore, compact resistance exercise device prototypes are being developed. The NASA Digital Astronaut Project (DAP) is supporting the Advanced Exercise Concepts (AEC) Project, Exercise Physiology and Countermeasures (ExPC) project and the National Space Biomedical Research Institute (NSBRI) funded researchers by developing computational models of exercising with these new advanced exercise device concepts. To perform validation of these models and to support the Advanced Exercise Concepts Project, several candidate devices have been flown onboard NASAs Reduced Gravity Aircraft. In terrestrial laboratories, researchers typically have available to them motion capture systems for the measurement of subject kinematics. Onboard the parabolic flight aircraft it is not practical to utilize the traditional motion capture systems due to the large working volume they require and their relatively high replacement cost if damaged. To support measuring kinematics on board parabolic aircraft, a motion capture system is being developed utilizing open source computer vision code with commercial off the shelf (COTS) video camera hardware. While the systems accuracy is lower than lab setups, it provides a means to produce quantitative comparison motion capture kinematic data. Additionally, data such as required exercise volume for small spaces such as the Orion capsule can be determined. METHODS: OpenCV is an open source computer vision library that provides the ability to perform multi-camera 3 dimensional reconstruction. Utilizing OpenCV, via the Python programming language, a set of tools has been developed to perform motion capture in confined spaces using commercial cameras. Four Sony Video Cameras were intrinsically calibrated prior to flight. Intrinsic calibration provides a set of camera specific parameters to remove geometric distortion of the lens and sensor (specific to each individual camera). A set of high contrast markers were placed on the exercising subject (safety also necessitated that they be soft in case they become detached during parabolic flight); small yarn balls were used. Extrinsic calibration, the determination of camera location and orientation parameters, is performed using fixed landmark markers shared by the camera scenes. Additionally a wand calibration, the sweeping of the camera scenes simultaneously, was also performed. Techniques have been developed to perform intrinsic calibration, extrinsic calibration, isolation of the markers in the scene, calculation of marker 2D centroids, and 3D reconstruction from multiple cameras. These methods have been tested in the laboratory side-by-side comparison to a traditional motion capture system and also on a parabolic flight.

Biodynamics↗

NASA NTRS2016

Supplementing biomechanical modeling with EMG analysis

It is well established that astronauts experience musculoskeletal deconditioning when exposed to microgravity environments for long periods of time. Spaceflight exercise is used to counteract these effects, and the Advanced Resistive Exercise Device (ARED) on the International Space Station (ISS) has been effective in minimizing musculoskeletal losses. However, the exercise devices of the new exploration vehicles will have requirements of limited mass, power and volume. Because of these limitations, there is a concern that the exercise devices will not be as effective as ARED in maintaining astronaut performance. Therefore, biomechanical modeling is being performed to provide insight on whether the small Multi-Purpose Crew Vehicle (MPCV) device, which utilizes a single-strap design, will provide sufficient physiological loading to maintain musculoskeletal performance. Electromyography (EMG) data are used to supplement the biomechanical model results and to explore differences in muscle activation patterns during exercises using different loading configurations.

electromyography↗

NASA NTRS2015

Human Research Program Advanced Exercise Concepts (AEC) Overview

Exercise countermeasures provide benefits that are crucial for successful human spaceflight, to mitigate the spaceflight physiological deconditioning which occurs during exposure to microgravity. The NASA Human Research Program (HRP) within the Human Exploration and Operations Mission Directorate (HEOMD) is managing next generation Advanced Exercise Concepts (AEC) requirements development and candidate technology maturation to Technology Readiness Level (TRL) 7 (ground prototyping and flight demonstration) for all exploration mission profiles from Multi Purpose Crew Vehicle (MPCV) Exploration Missions (up to 21 day duration) to Mars Transit (up to 1000 day duration) missions. These validated and optimized exercise countermeasures systems will be provided to the ISS Program and MPCV Program for subsequent flight development and operations. The International Space Station (ISS) currently has three major pieces of operational exercise countermeasures hardware: the Advanced Resistive Exercise Device (ARED), the second-generation (T2) treadmill, and the cycle ergometer with vibration isolation system (CEVIS). This suite of exercise countermeasures hardware serves as a benchmark and is a vast improvement over previous generations of countermeasures hardware, providing both aerobic and resistive exercise for the crew. However, vehicle and resource constraints for future exploration missions beyond low Earth orbit will require that the exercise countermeasures hardware mass, volume, and power be minimized, while preserving the current ISS capabilities or even enhancing these exercise capabilities directed at mission specific physiological functional performance and medical standards requirements. Further, mission-specific considerations such as preservation of sensorimotor function, autonomous and adaptable operation, integration with medical data systems, rehabilitation, and in-flight monitoring and feedback are being developed for integration with the exercise countermeasures systems. Numerous technologies have been considered and evaluated against HRP-approved functional device requirements for these extreme mission profiles, and include wearable sensors, exoskeletons, flywheel, pneumatic, and closed-loop microprocessor controlled motor driven systems. Each technology has unique advantages and disadvantages. The Advanced Exercise Concepts project oversees development of candidate next generation exercise countermeasures hardware, performs trade studies of current and state of the art exercise technologies, manages and supports candidate systems physiological evaluations with human test subjects on the ground, in flight analogs and flight. The near term goal is evaluation of candidate systems in flight, culminating in an integrated candidate next generation exercise countermeasures suite on the ISS which coalesces research findings from HRP disciplines in the areas of exercise performance for muscle, bone, cardiovascular, sensorimotor, behavioral health, and nutrition for optimal benefit to the crew.

Countermeasures↗

NASA NTRS2015

Development of Bone Remodeling Model for Spaceflight Bone Physiology Analysis

Current spaceflight exercise countermeasures do not eliminate bone loss. Astronauts lose bone mass at a rate of 1-2% a month (Lang et al. 2004, Buckey 2006, LeBlanc et al. 2007). This may lead to early onset osteoporosis and place the astronauts at greater risk of fracture later in their lives. NASA seeks to improve understanding of the mechanisms of bone remodeling and demineralization in 1g in order to appropriately quantify long term risks to astronauts and improve countermeasures. NASA's Digital Astronaut Project (DAP) is working with NASA's bone discipline to develop a validated computational model to augment research efforts aimed at achieving this goal.

Microgravity↗

NASA NTRS2015

Probabilistic Risk Assessment for Astronaut Post Flight Bone Fracture

Introduction: Space flight potentially reduces the loading that bone can resist before fracture. This reduction in bone integrity may result from a combination of factors, the most common reported as reduction in astronaut BMD. Although evaluating the condition of bones continues to be a critical aspect of understanding space flight fracture risk, defining the loading regime, whether on earth, in microgravity, or in reduced gravity on a planetary surface, remains a significant component of estimating the fracture risks to astronauts. This presentation summarizes the concepts, development, and application of NASA's Bone Fracture Risk Module (BFxRM) to understanding pre-, post, and in mission astronaut bone fracture risk. The overview includes an assessment of contributing factors utilized in the BFxRM and illustrates how new information, such as biomechanics of space suit design or better understanding of post flight activities may influence astronaut fracture risk. Opportunities for the bone mineral research community to contribute to future model development are also discussed. Methods: To investigate the conditions in which spaceflight induced changes to bone plays a critical role in post-flight fracture probability, we implement a modified version of the NASA Bone Fracture Risk Model (BFxRM). Modifications included incorporation of variations in physiological characteristics, post-flight recovery rate, and variations in lateral fall conditions within the probabilistic simulation parameter space. The modeled fracture probability estimates for different loading scenarios at preflight and at 0 and 365 days post-flight time periods are compared. Results: For simple lateral side falls, mean post-flight fracture probability is elevated over mean preflight fracture probability due to spaceflight induced BMD loss and is not fully recovered at 365 days post-flight. In the case of more energetic falls, such as from elevated heights or with the addition of lateral movement, the contribution of space flight quality changes is much less clear, indicating more granular assessments, such as Finite Element modeling, may be needed to further assess the risks in these scenarios.

Risk Analysis↗

NASA NTRS2013

Probabilistic Risk Assessment for Bone Fracture - Bone Fracture Risk Module (BFxRM)

This presentation summarizes the concepts, development, and application of NASA's Bone Fracture Risk Module (BFxRM). The overview includes an assessmnet of strenghts and limitations of the BFxRM and proposes a numebr of discussion questions to the panel regarding future development avenues for this simulation system.

Monte Carlo Method↗

NASA NTRS2012

Estimated Probability of Traumatic Chest Injury During an International Space Station Mission

No abstract available

Lewandowski, Beth↗

NASA NTRS2012

Development of a Traumatic Abdominal Injury Module for Estimation of Injury Probability During an International Space Station Mission

No abstract available

Lewandowski, Beth↗

NASA NTRS2011

The Value of Biomedical Simulation Environments to Future Human Space Flight Missions

Mars and NEO missions will expose astronaut to extended durations of reduced reduced gravity, isolation and higher radiation. These new operation conditions pose health risks that are not well understood and perhaps unanticipated. Advanced computational simulation environments can beneficially augment research to predict, assess and mitigate potential hazards to astronaut health. The NASA Digital Astronaut Project (DAP), within the NASA Human Research Program, strives to achieve this goal.

Mulugeta,Lealem↗

NASA NTRS2011

Sleep Disruption Medical Intervention Forecasting (SDMIF) Module for the Integrated Medical Model

The NASA Integrated Medical Model (IMM) assesses the risk, including likelihood and impact of occurrence, of all credible in-flight medical conditions. Fatigue due to sleep disruption is a condition that could lead to operational errors, potentially resulting in loss of mission or crew. Pharmacological consumables are mitigation strategies used to manage the risks associated with sleep deficits. The likelihood of medical intervention due to sleep disruption was estimated with a well validated sleep model and a Monte Carlo computer simulation in an effort to optimize the quantity of consumables. METHODS: The key components of the model are the mission parameter program, the calculation of sleep intensity and the diagnosis and decision module. The mission parameter program was used to create simulated daily sleep/wake schedules for an ISS increment. The hypothetical schedules included critical events such as dockings and extravehicular activities and included actual sleep time and sleep quality. The schedules were used as inputs to the Sleep, Activity, Fatigue and Task Effectiveness (SAFTE) Model (IBR Inc., Baltimore MD), which calculated sleep intensity. Sleep data from an ISS study was used to relate calculated sleep intensity to the probability of sleep medication use, using a generalized linear model for binomial regression. A human yes/no decision process using a binomial random number was also factored into sleep medication use probability. RESULTS: These probability calculations were repeated 5000 times resulting in an estimate of the most likely amount of sleep aids used during an ISS mission and a 95% confidence interval. CONCLUSIONS: These results were transferred to the parent IMM for further weighting and integration with other medical conditions, to help inform operational decisions. This model is a potential planning tool for ensuring adequate sleep during sleep disrupted periods of a mission.

Lewandowski, Beth↗

NASA NTRS2007

An Implanted, Stimulated Muscle Powered Piezoelectric Generator

A totally implantable piezoelectric generator system able to harness power from electrically activated muscle could be used to augment the power systems of implanted medical devices, such as neural prostheses, by reducing the number of battery replacement surgeries or by allowing periods of untethered functionality. The features of our generator design are no moving parts and the use of a portion of the generated power for system operation and regulation. A software model of the system has been developed and simulations have been performed to predict the output power as the system parameters were varied within their constraints. Mechanical forces that mimic muscle forces have been experimentally applied to a piezoelectric generator to verify the accuracy of the simulations and to explore losses due to mechanical coupling. Depending on the selection of system parameters, software simulations predict that this generator concept can generate up to approximately 700 W of power, which is greater than the power necessary to drive the generator, conservatively estimated to be 50 W. These results suggest that this concept has the potential to be an implantable, self-replenishing power source and further investigation is underway.

Lewandowski, Beth↗

NASA NTRS2005

Concept Developed for an Implanted Stimulated Muscle-Powered Piezoelectric Generator

Implanted electronic devices are typically powered by batteries or transcutaneous power transmission. Batteries must be replaced or recharged, and transcutaneous power sources burden the patient or subject with external equipment prone to failure. A completely self-sustaining implanted power source would alleviate these limitations. Skeletal muscle provides an available autologous power source containing native chemical energy that produces power in excess of the requirements for muscle activation by motor nerve stimulation. A concept has been developed to convert stimulated skeletal muscle power into electrical energy (see the preceding illustration). We propose to connect a piezoelectric generator between a muscle tendon and bone. Electrically stimulated muscle contractions would exert force on the piezoelectric generator, charging a storage circuit that would be used to power the stimulator and other devices.

Lewandowski, Beth↗

NASA NTRS2004

Generation of Electrical Power from Stimulated Muscle Contractions Evaluated

This project is a collaborative effort between NASA Glenn Research Center's Revolutionary Aeropropulsion Concepts (RAC) Project, part of the NASA Aerospace Propulsion and Power Program of the Aerospace Technology Enterprise, and Case Western Reserve University's Cleveland Functional Electrical Stimulation (FES) Center. The RAC Project foresees implantable power requirements for future applications such as organically based sensor platforms and robotics that can interface with the human senses. One of the goals of the FES Center is to develop a totally implantable neural prosthesis. This goal is based on feedback from patients who would prefer a system with an internal power source over the currently used system with an external power source. The conversion system under investigation would transform the energy produced from a stimulated muscle contraction into electrical energy. We hypothesize that the output power of the system will be greater than the input power necessary to initiate, sustain, and control the electrical conversion system because of the stored potential energy of the muscle. If the system can be made biocompatible, durable, and with the potential for sustained use, then the biological power source will be a viable solution.

Lewandowski, Beth↗