A Variable Stiffness Joint With Electrospun P(VDF-TrFE-CTFE) Variable Stiffness Springs

• Published in: IEEE robotics and automation letters Vol. 3; no. 2; pp. 973 - 978
• Main Authors: Carloni, Raffaella, Lapp, Valerie I., Cremonese, Andrea, Belcari, Juri, Zucchelli, Andrea
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.04.2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Actuators; Aluminum; Cameras; Chlorotrifluoroethylene; compliant joint/mechanism; Deflection; Electric fields; Electrodes; Electrospinning; Leaf springs; Microscopy; Nanofibers; Soft material robotics; Springs; Stiffness; Strain; Viability; Vinylidene; Vinylidene fluoride; Voltage measurement
• ISSN: 2377-3766; 2377-3766
• DOI: 10.1109/LRA.2018.2793348

This letter presents a novel rotational variable stiffness joint that relies on one motor and a set of variable stiffness springs. The variable stiffness springs are leaf springs with a layered design, i.e., an electro-active layer of electrospun aligned nanofibers of poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] surrounded by two electrodes of aluminum and held together by inactive material. To achieve a variable stiffness, different voltages and, therefore, different electric fields, are applied to the springs. The variable stiffness springs are electromechanically analyzed to highlight the voltage-deflection and force-deflection characteristics. Finally, the springs are used in the design of a proof-of-concept variable stiffness joint prototype. Experimental results on the variable stiffness joint confirm the viability of the proposed solution.