1 April 2014 Variable modulus cellular structures using pneumatic artificial muscles
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This paper presents a novel variable modulus cellular structure based on a hexagonal unit cell with pneumatic artificial muscle (PAM) inclusions. The cell considered is pin-jointed, loaded in the horizontal direction, with three PAMs (one vertical PAM and two horizontal PAMs) oriented in an “H” configuration between the vertices of the cell. A method for calculation of the hexagonal cell modulus is introduced, as is an expression for the balance of tensile forces between the horizontal and vertical PAMs. An aluminum hexagonal unit cell is fabricated and simulation of the hexagonal cell with PAM inclusions is then compared to experimental measurement of the unit cell modulus in the horizontal direction with all three muscles pressurized to the same value over a pressure range up to 758 kPa. A change in cell modulus by a factor of 1.33 and a corresponding change in cell angle of 0.41° are demonstrated experimentally. A design study via simulation predicts that differential pressurization of the PAMs up to 2068 kPa can change the cell modulus in the horizontal direction by a factor of 6.83 with a change in cell angle of only 2.75°. Both experiment and simulation show that this concept provides a way to decouple the length change of a PAM from the change in modulus to create a structural unit cell whose in-plane modulus in a given direction can be tuned based on the orientation of PAMs within the cell and the pressure supplied to the individual muscles.
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Michael E. Pontecorvo, Michael E. Pontecorvo, Robert J. Niemiec, Robert J. Niemiec, Farhan S. Gandhi, Farhan S. Gandhi, "Variable modulus cellular structures using pneumatic artificial muscles", Proc. SPIE 9057, Active and Passive Smart Structures and Integrated Systems 2014, 905717 (1 April 2014); doi: 10.1117/12.2048872; https://doi.org/10.1117/12.2048872

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