Modeling the dynamic characteristics of pneumatic muscle.
A pneumatic muscle (PM) system was studied to determine whether a three-element model could describe its dynamics. As far as the authors are aware, this model has not been used to describe the dynamics of PM. A new phenomenological model consists of a contractile (force-generating) element, spring element, and damping element in parallel. The PM system was investigated using an apparatus that allowed precise and accurate actuation pressure (P) control by a linear servo-valve. Length change of the PM was measured by a linear potentiometer. Spring and damping element functions of P were determined by a static perturbation method at several constant P values. These results indicate that at constant P, PM behaves as a spring and damper in parallel. The contractile element function of P was determined by the response to a step input in P, using values of spring and damping elements from the perturbation study. The study showed that the resulting coefficient functions of the three-element model describe the dynamic response to the step input of P accurately, indicating that the static perturbation results can be applied to the dynamic case. This model is further validated by accurately predicting the contraction response to a triangular P waveform. All three elements have pressure-dependent coefficients for pressure P in the range 207 < or = P < or = 621 kPa (30 < or = P < or = 90 psi). Studies with a step decrease in P (relaxation of the PM) indicate that the damping element coefficient is smaller during relaxation than contraction.
Reynolds
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Department of Biomedical, Industrial and Human Factors Engineering, Wright State University, Dayton, OH 45435, USA. david.reynolds@wright.edu
Repperger
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Phillips
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CA
Bandry
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D000399:Air Pressure; D000818:Animals; D001187:Artificial Organs; D040761:Biomimetic Materials; D032701:Biomimetics / Q000295:instrumentation / Q000379:methods*; D003198:Computer Simulation; D004548:Elasticity; D006801:Humans; D008954:Models, Biological; D008962:Models, Theoretical; D009038:Motion; D009119:Muscle Contraction / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D012212:Rheology / Q000295:instrumentation / Q000379:methods*; D012371:Robotics / Q000295:instrumentation / Q000379:methods; D013314:Stress, Mechanical; D014783:Viscosity