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Full-Text Articles in Aerospace Engineering
Muscle Synergies Improve Estimation Of Knee Contact Forces During Walking, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd
Muscle Synergies Improve Estimation Of Knee Contact Forces During Walking, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd
Allison Kinney
This study investigates whether use of subject-specific muscle synergies can improve optimization predictions of muscle excitation patterns and knee contact forces during walking. Muscle synergies describe how a small number of neural commands generated by the nervous system can be linearly combined to produce the broad range of muscle electromyographic (EMG) signals measured experimentally. By quantifying the interdependence of individual EMG signals, muscle synergies provide dimensionality reduction for the neural control redundancy problem. Our hypothesis was that use of subjectspecific muscle synergies to limit muscle excitation patterns would improve prediction of muscle EMG patterns at the hip, knee, and ankle …
Muscle Synergy Constraints Improve Prediction Of Knee Contact Force During Gait, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd
Muscle Synergy Constraints Improve Prediction Of Knee Contact Force During Gait, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd
Allison Kinney
Knowledge of patient-specific muscle and joint contact forces during activities of daily living could improve the treatment of movement-related disorders (e.g., osteoarthritis, stroke, cerebral palsy, Parkinson’s disease). Unfortunately, it is currently impossible to measure these quantities directly under common clinical conditions, and calculation of these quantities using computer models is limited by the redundant nature of human neural control (i.e., more muscles than theoretically necessary to actuate the available degrees of freedom in the skeleton). Walking is a particularly important task to understand, since loss of mobility is associated with increased morbidity and decreased quality of life. Though numerous musculoskeletal …
Evaluation Of Different Optimal Control Problem Formulations For Solving The Muscle Redundancy Problem, Friedl De Groote, Allison Kinney, Anil Rao, Benjamin Fregly
Evaluation Of Different Optimal Control Problem Formulations For Solving The Muscle Redundancy Problem, Friedl De Groote, Allison Kinney, Anil Rao, Benjamin Fregly
Allison Kinney
This study evaluates several possible optimal control problem formulations for solving the muscle redundancy problem with the goal of identifying the most efficient and robust formulation. One novel formulation involves the introduction of additional controls that equal the time derivative of the states, resulting in very simple dynamic equations. The nonlinear equations describing muscle dynamics are then imposed as algebraic constraints in their implicit form, simplifying their evaluation. By comparing different problem formulations for computing muscle controls that can reproduce inverse dynamic joint torques during gait, we demonstrate the efficiency and robustness of the proposed novel formulation.
Synergies Controls Improve Prediction Of Knee Contact Forces And Muscle Excitations During Gait, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd
Synergies Controls Improve Prediction Of Knee Contact Forces And Muscle Excitations During Gait, Benjamin Fregly, Jonathan Walter, Allison Kinney, Scott Banks, Darryl D'Lima, Thor Besier, David Lloyd
Allison Kinney
This study investigates whether use of muscle excitation controls constructed from subjectspecific muscle synergy information can improve optimization prediction of knee contact forces and muscle excitations during walking. Muscle synergies quantify how a large number of experimental muscle electromyographic (EMG) signals can be reconstructed by linearly mixing a much smaller number of neural commands generated by the nervous system. Our hypothesis was that controlling all muscle excitations with a small set of experimentally calculated neural commands would improve prediction of knee contact forces and leg muscle excitations compared to using independently controlled muscle excitations.
Comparison Of Material Properties And Microstructure Of Specimens Built Using The 3d Systems Vanguard Hs And Vanguard Hiq+Hs Sls Systems, T.J. Silverman, Allison Kinney, W. Yong, J.H. Koo
Comparison Of Material Properties And Microstructure Of Specimens Built Using The 3d Systems Vanguard Hs And Vanguard Hiq+Hs Sls Systems, T.J. Silverman, Allison Kinney, W. Yong, J.H. Koo
Allison Kinney
The HiQ upgrade to the 3D Systems Vanguard selective laser sintering (SLS) machine incorporates a revised thermal calibration system and new control software. The paper compares the tensile modulus, tensile strength, elongation at break, flexural modulus, Izod impact resistance and microstructure of two batteries of standard specimens built from recycled Duraform PA (Nylon 12). The first set is built on a Vanguard HS system and the second on the same system with the HiQ upgrade installed. The upgrade reduces user intervention, decreases total build time and improves surface finish. However, using the default processing parameters, tensile, flexure and impact properties …
Construction Of Naca 66-415 Nlf Composite Wing For Acoustic Turbulence Testing, Scott Sawyer, Sean Stewart
Construction Of Naca 66-415 Nlf Composite Wing For Acoustic Turbulence Testing, Scott Sawyer, Sean Stewart
Dr. Scott Sawyer
A design is developed for a Natural Laminar Flow (NLF) wing, to be used at California Polytechnic State University for acoustic turbulence testing. Composite materials are used to produce high-quality surface finishes necessary for laminar flow. A design for the test apparatus is presented and justified. A manufacturing procedure is proposed for the carbon fiber skin, using Vacuum Resin Infusion (VRI). This procedure is tested on a scaled part with satisfactory results; lessons learned are discovered and integrated into the final manufacturing process. The test section has been fit to the Cal Poly wind tunnel, but full implementation has not …
Aeroelastic Energy Harvesting Using A Nonlinear Electromagnetic Oscillator, Katherine Bender, Ndungu Muturi, Alex Spies, Christopher Lee
Aeroelastic Energy Harvesting Using A Nonlinear Electromagnetic Oscillator, Katherine Bender, Ndungu Muturi, Alex Spies, Christopher Lee
Christopher Lee
Results are presented from the design, fabrication and testing of an electromagnetic-inductor device to convert aeroelastic-induced oscillations of an airfoil into electricity. The energy harvester consists of three magnets configured such that the force-displacement relationship can be described by a fifth-degree polynomial. the integration of the harvester into a two-degree-of-freedom, pitch/plunge airfoil system introduces nonlinear stiffness into the plunge direction. This nonlinearity gives rise to limit cycle oscillations which, in turn, are converted to electric power by the harvester. Experimental measurements from wind tunnel tests are compared to predictions of limit cycle response and resulting power generation using a two-degree-of-freedom …
Stall Flutter Measurements From A Two-Degree-Of-Freedom Airfoil With Nonlinear Stiffness, Ndungu Muturi, Alex Spies, Katherine Bender, Christopher Lee
Stall Flutter Measurements From A Two-Degree-Of-Freedom Airfoil With Nonlinear Stiffness, Ndungu Muturi, Alex Spies, Katherine Bender, Christopher Lee
Christopher Lee
Results are presented from an experimental study of stall flutter oscillations from a two-degree-of-freedom, pitch/plunge airfoil system with nonlinear structural stiffness in the plunge direction. With linear (only) structural stiffness, the airfoil system could exhibit a large-pitch-amplitude limit cycle response which is attributed to stall. With the addition of the nonlinear stiffness, the airfoil system could exhibit two classes of limit cycle response: one with low-pitch-amplitude attributed to the structural nonlinearity and one with high-pitch-amplitude attributed to stall. The amplitudes of the limit cycles for cases in which the structurals and aerodynamic nonlinearities co-exist are modulated and remain steady over …
Experimental Evaluation Of Turbine Blade With Potassium Evaporative Cooling, Jessica Townsend
Experimental Evaluation Of Turbine Blade With Potassium Evaporative Cooling, Jessica Townsend
Jessica Townsend
A new method of turbine blade cooling, the Return Flow Cascade, has been developed in which vaporization of a liquid metal such as potassium is used to maintain the blade surface at a nearly uniform temperature. Turbine blades cooled using this technology have lower blade temperature levels compared to that available with conventional air cooling, potentially resulting in higher firing temperatures or a choice of a wider range of materials for the hot gas path. The detailed operation of the Return Flow Cascade is described including fluid mechanic and heat transfer phenomena that occur at high heat flux and gravitational …