Design and dynamic modeling of electrorheological fluid-based variable-stiffness fin for robotic fish

Abstract

Fish actively control their stiffness in different swimming conditions. Inspired by such an adaptive behavior, in this paper we study the design, prototyping, and dynamic modeling of compact, tunable-stiffness fins for robotic fish, where electrorheological (ER) fluid serves as the enabling element. A multi-layer composite fin with an ER fluid core is prototyped and utilized to investigate the influence of electrical field on its performance. Hamilton's principle is used to derive the dynamic equations of motion of the flexible fin, and Lighthill's large-amplitude elongated-body theory is adopted to estimate the hydrodynamic force when the fin undergoes base-actuated rotation. The dynamic equations are then discretized using the finite element method, to obtain an approximate numerical solution. Experiments are conducted on the prototyped flexible ER fluid-filled beam for parameter identification and validation of the proposed model, and for examining the effectiveness of electrically controlled stiffness tuning. In particular, it is found that the natural frequency is increased by almost 40% when the applied electric field changes from 0 to .

Intelligent Soft Surgical Robots for Next‐Generation Minimally Invasive Surgery

“…A detailed description of the internal conversion mechanism can be found in various studies (ERF [141][142][143] and MRF [144,145] ). ERF/MRF has been demonstrated in some robotic applications, e.g., rehabilitation robotics, [146] robotic joints, [147] and robotic fish, [148] as well as some medical applications, e.g., catheters and prosthesis penile. [44] MRF usually shows greater stiffness changes than ERF, [149] whereas ERF has lower energy consumption.…”

Mechanically transformative electronics, sensors, and implantable devices

“…Among many phase change materials (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), including shape memory polymers (7)(8)(9)20), phase change metals (e.g., low-melting point alloys) (10)(11)(12)(13), and magnetorheological (14,15) and electrorheological fluids (16), gallium is one of the most attractive options for the transformative platform involving biological applications because of its biocompatibility, high elastic modulus (9.8 GPa), and ideal melting temperature (29.8°C) (21,22), which makes it solid at room temperature (22° to 25°C) and liquid at the temperature of biological tissue (32° to 37°C). By being embedded in a soft polymer, similar to what have been reported by recent studies on variable stiffness devices (10,12,23), the meltable and freezable features of gallium en-able large rigidity tuning (between a few tens of kPa and ~10 GPa) when applied to or detached from tissue.…”

Modular multi-motor exercise system for space exploration

“…MRF, on the other hand, operates with magnetic fields. The use of magnetic fields can not only reduce power consumption but also make the system feasible to work in space, reason why we have decided to explore it [4,18,20,24,28].…”