Principal Aim To assess the strength changes, and associated change in fracture risk, due to structural alterations in the proximal femora of astronauts experiencing long- term weightlessness 3-D FEA has not yet applied to bone loss in astronauts Greatly increased risk of fracture upon return to Earth and possibly even under strenuous loading in space or on the moon or Mars Calculate change in factor of risk() op= actual load / predicted failure load hypothesis:Φpe<Φpot relationship between g and duration of weightlessness
Principal Aim To assess the strength changes, and associated change in fracture risk, due to structural alterations in the proximal femora of astronauts experiencing longterm weightlessness. • 3-D FEA has not yet applied to bone loss in astronauts – Greatly increased risk of fracture upon return to Earth and possibly even under strenuous loading in space or on the moon or Mars. • Calculate change in factor of risk (Φ) – Φ = actual load / predicted failure load – hypothesis: Φpre < Φpost – relationship between Φ and duration of weightlessness
Research Plan 36y.0 Space Flight△ 3-segment models Male Incr. endost diam locomotion (3 dof) CT Red trabec. mass fall impact (5 dof) DXA Red. musc. strength Gender Adjustable Equations of Motion Finite Lagrangian Element Gravity Level Kane's method Model Earth(g), Mars(3/8g) Fracture Risk Failure load F Applied Load F
Research Plan Adjustable Finite Element Model 3-segment models: • locomotion (3 dof) • fall impact (5 dof) Gender 36 y.o. Male • CT • DXA Space Flight ∆: Incr. endost. diam. Red. trabec. mass Red. musc. strength Gravity Level Earth (g), Mars (3/8g) Equations of Motion: • Lagrangian • Kane’s method Failure Load Applied Load Fracture Risk Φ = Fapplied Ffail
Aim 1: Hip Loading During Locomotion 3-segment model for locomotion Lagrangian formulation P2, t
Aim 1: 3-segment model for locomotion • Lagrangian formulation p1, τ1 p2, τ2 p3, τ3 m1, I1 m2, I2 m3, I3 vc3 g y x Hip Loading During Locomotion
Solution of Equations for Locomotion Initial joint velocity from hip/seg. 3 Calc joint acceleration at each time step Integrate to get velocity and position values Hip force from cm acceleration via Jacobian
Solution of Equations for Locomotion Initial joint velocity from hip/seg. 3 Calc. joint acceleration at each time step Integrate to get velocity and position values Hip force from c.m. acceleration via Jacobian
Control Scheme(locomotion) Hip torque PPD control F Ankle knee torque Y Impedance control F
Control Scheme (locomotion) Hip torque: PPD control Ankle & knee torque: Impedance control γ FF x F y Y X