Nature as an engineer: one simple concept of a bio-inspired functional artificial muscle

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.

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“…The functional artificial muscle prototype exhibits contraction dynamics similar to Hill's model characteristics (Figure 3(a) [13, 15]).…”

Section: Resultsmentioning

confidence: 99%

Theoretical Hill-Type Muscle and Stability: Numerical Model and Application

Schmitt

Günther

Rupp

et al. 2013

Computational and Mathematical Methods in Medicine

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“…The dependence of force generation from contraction velocity is so universally accepted that models explaining the mechanisms of skeletal muscle are specifically tested for their ability to predict the shape of experimentally determined F-V curves (Huxley, 1957; Piazzesi et al, 2007). Moreover, a better understanding of the F-V relationship and the underlying contraction mechanism might help elucidate the pathogenesis of several hereditary sarcomere myopathies and the effects of different drugs with effects on muscle contraction (Ferrantini et al, 2009; Malik et al, 2011; Mansson, 2014; Spudich, 2014), and ultimately benefit the development of robotic and prosthetic applications that rely on bio-inspired actuators that exhibit natural (muscle-like) features in order to mimic the performance of biological systems (Paluska and Herr, 2006; Schmitt et al, 2012; Xiong et al, 2014; Chen et al, 2016; Hyun et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

On the Shape of the Force-Velocity Relationship in Skeletal Muscles: The Linear, the Hyperbolic, and the Double-Hyperbolic

Csapo²,

et al. 2019

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The shape of the force-velocity (F-V) relationship has important implications for different aspects of muscle physiology, such as muscle efficiency and fatigue, the understanding of the pathophysiology of several myopathies or the mechanisms of muscle contraction per se , and may be of relevance for other fields, such as the development of robotics and prosthetic applications featuring natural muscle-like properties. However, different opinions regarding the shape of the F-V relationship and the underlying mechanisms exist in the literature. In this review, we summarize relevant evidence on the shape of the F-V relationship obtained over the last century. Studies performed at multiple scales ranging from the sarcomere to the organism level have described the concentric F-V relationship as linear, hyperbolic or double-hyperbolic. While the F-V relationship has most frequently been described as a rectangular hyperbola, a large number of studies have found deviations from the hyperbolic function at both ends of the F-V relation. Indeed, current evidence suggests that the F-V relation in skeletal muscles follows a double-hyperbolic pattern, with a breakpoint located at very high forces/low velocities, which may be a direct consequence of the kinetic properties of myofilament cross-bridge formation. Deviations at low forces/high velocities, by contrast, may be related to a recently discovered, calcium-independent regulatory mechanism of muscle contraction, which may also explain the low metabolic cost of very fast muscle shortening contractions. Controversial results have also been reported regarding the eccentric F-V relationship, with studies in prepared muscle specimens suggesting that maximum eccentric force is substantially greater than isometric force, whereas in vivo studies in humans show only a modest increase, no change, or even a decrease in force in lengthening contractions. This review discusses possible reasons reported in the literature for these discrepant findings, including the testing procedures (familiarization, pre-load condition, and temperature) and a potential neural inhibition at higher lengthening velocities. Finally, some unresolved questions and recommendations for F-V testing in humans are reported at the end of this document.

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“…Biomechanical models of muscle contraction dynamics support and emphasize that unique feature [7,17,21,23,53,60,66]. Interestingly, it has been suggested that these very nonlinearities of biological structures could reduce control effort and simplify control of biology-like movements [2,15,18,20,40,45,48,51,61,64].…”

Section: Introductionmentioning

confidence: 99%

Quantifying control effort of biological and technical movements: An information-entropy-based approach

et al. 2014

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In biomechanics and biorobotics, muscles are often associated with reduced movement control effort and simplified control compared to technical actuators. This is based on evidence that the nonlinear muscle properties positively influence movement control. It is, however, open how to quantify the simplicity aspect of control effort and compare it between systems. Physical measures, such as energy consumption, stability, or jerk, have already been applied to compare biological and technical systems. Here a physical measure of control effort based on information entropy is presented. The idea is that control is simpler if a specific movement is generated with less processed sensor information, depending on the control scheme and the physical properties of the systems being compared. By calculating the Shannon information entropy of all sensor signals required for control, an information cost function can be formulated allowing the comparison of models of biological and technical control systems. Exemplarily applied to (bio-)mechanical models of hopping, the method reveals that the required information for generating hopping with a muscle driven by a simple reflex control scheme is only I=32 bits versus I=660 bits with a DC motor and a proportional differential controller. This approach to quantifying control effort captures the simplicity of a control scheme and can be used to compare completely different actuators and control approaches.

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Nature as an engineer: one simple concept of a bio-inspired functional artificial muscle

Cited by 21 publications

References 52 publications

Theoretical Hill-Type Muscle and Stability: Numerical Model and Application

Theoretical Hill-Type Muscle and Stability: Numerical Model and Application

On the Shape of the Force-Velocity Relationship in Skeletal Muscles: The Linear, the Hyperbolic, and the Double-Hyperbolic

Quantifying control effort of biological and technical movements: An information-entropy-based approach

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