Variable stiffness and recruitment using nylon actuators arranged in a pennate configuration

Soheil Kianzad; Milind Pandit; Johnathan D. Lewis; Alexander R. Berlingeri; Karl J. Haebler; John D. W. Madden

doi:10.1117/12.2086799

29 April 2015 Variable stiffness and recruitment using nylon actuators arranged in a pennate configuration

Soheil Kianzad, Milind Pandit, Johnathan D. Lewis, Alexander R. Berlingeri, Karl J. Haebler, John D. W. Madden

Proceedings Volume 9430, Electroactive Polymer Actuators and Devices (EAPAD) 2015; 94301Z (2015) https://doi.org/10.1117/12.2086799
Event: SPIE Smart Structures and Materials + Nondestructive Evaluation and Health Monitoring, 2015, San Diego, California, United States

Abstract

In muscle variable impedance and ability to recruit fibers as needed helps enable actions such as walking and catching. A new biomimetic structure of nylon actuator is presented that imitates the human pennate muscle in structure, ability to vary stiffness and the ability to increase force by recruiting additional fibers. The actuator consists of 16 silver coated nylon coiled fibers attached to a central tendon at an angle of 20°. Each nylon coil produces 20 MPa of stress at constant length and nearly 20% strain at fixed load. Fibers are individually switched ON and OFF using transistors so that each element can be recruited, and the stiffness varied. The amount of input power is controlled with pulse width modulation (PWM) techniques. It is observed that the spring constant of the pennate structure varies from that of its passive state, 503 N/m and a resonance frequency of 1.4 Hz, to 1480 N/m with resonance frequency of 3.1 Hz in the active state where all the fibers are switched on under a 25 N load. Stiffness can be varied by a factor of 9.

Citation Download Citation

Soheil Kianzad, Milind Pandit, Johnathan D. Lewis, Alexander R. Berlingeri, Karl J. Haebler, and John D. W. Madden "Variable stiffness and recruitment using nylon actuators arranged in a pennate configuration", Proc. SPIE 9430, Electroactive Polymer Actuators and Devices (EAPAD) 2015, 94301Z (29 April 2015); https://doi.org/10.1117/12.2086799

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