15 Fakultätsübergreifend / Sonstige Einrichtung

Permanent URI for this collectionhttps://elib.uni-stuttgart.de/handle/11682/16

Browse

Filters

1986 - 198912010 - 20152

Settings

Subject: search.filters.subject.500

Search Results

Now showing 1 - 3 of 3
  • Thumbnail Image
    ItemOpen Access
    Comparative sensitivity analysis of muscle activation dynamics
    (2015) Rockenfeller, Robert; Günther, Michael; Schmitt, Syn; Götz, Thomas
    We mathematically compared two models of mammalian striated muscle activation dynamics proposed by Hatze and Zajac. Both models are representative for a broad variety of biomechanical models formulated as ordinary differential equations (ODEs). These models incorporate parameters that directly represent known physiological properties. Other parameters have been introduced to reproduce empirical observations. We used sensitivity analysis to investigate the influence of model parameters on the ODE solutions. In addition, we expanded an existing approach to treating initial conditions as parameters and to calculating second- order sensitivities. Furthermore, we used a global sensitivity analysis approach to include finite ranges of parameter values. Hence, a theoretician striving for model reduction could use the method for identifying particularly low sensitivities to detect superfluous parameters. An experimenter could use it for identifying particularly high sensitivities to improve parameter estimation. Hatze’s nonlinear model incorporates some parameters to which activation dynamics is clearly more sensitive than to any parameter in Zajac’s linear model. Other than Zajac’s model, Hatze’s model can, however, reproduce measured shifts in optimal muscle length with varied muscle activity. Accordingly we extracted a specific parameter set for Hatze’s model that combines best with a particular muscle force-length relation.
  • Thumbnail Image
    ItemOpen Access
    News of the strictly decimal initiative
    (1986) Ludewig, Jochen
    Year after year, the U.S. will lose millions of dollars to useless arithmetic, convening yards into miles and vice versa. The problem is serious enough to threaten the leading role of the U.S. economy. Therefore, the President has decided to stop arithmetic fatalism and pessimism, and has launched a new movement, called the Strictly Decimal Initiative, aimed at introducing a revolutionary law in mathematics stating that 2 10 = 1000.
  • Thumbnail Image
    ItemOpen Access
    Theoretical hill-type muscle and stability : numerical model and application
    (2013) Schmitt, Syn; Günther, Michael; Rupp, Tille; Bayer, Alexandra; Häufle, Daniel F. B.
    The construction of artificial muscles is one of the most challenging developments in today's biomedical science. The application of artificial muscles is focused both on the construction of orthotics and prosthetics for rehabilitation and prevention purposes and on building humanoid walking machines for robotics research. Research in biomechanics tries to explain the functioning and design of real biological muscles and therefore lays the fundament for the development of functional artificial muscles. Recently, the hyperbolic Hill-type force-velocity relation was derived from simple mechanical components. In this contribution, this theoretical yet biomechanical model is transferred to a numerical model and applied for presenting a proof-of-concept of a functional artificial muscle. Additionally, this validated theoretical model is used to determine force-velocity relations of different animal species that are based on the literature data from biological experiments. Moreover, it is shown that an antagonistic muscle actuator can help in stabilising a single inverted pendulum model in favour of a control approach using a linear torque generator.