Artificial Muscle Actuators for a Robotic Fish

Abstract

Biology is a source of inspiration for many functional aspects of engineered systems. Fish can provide guidance for the design of animal-like robots, which have soft elastic bodies that are a continuum of actuator, sensor, and information processor. Fish respond to minute pressure changes in water, generating thrust and gaining lift from obstacles in the current, altering the shape of body and fins and using sensory nerves in their muscles to control them. Dielectric Elastomer (DE) artificial muscles offer a mechanism for a fish muscle actuator. DE devices have already been shown to outperform natural muscle in terms of active stress, strain, and speed[1-3]. DE's also have multi-functional capabilities that include actuation, sensing, logic and even energy harvesting, all achievable through appropriate control of charge [4,5]. But DE actuators must be designed so that they provide enough torque to drive the tail and develop useful forward thrust.In this study bench-top measurements of maximum torque and deflection data for DE actuators have been collected and compared with active torques measured using an instrumented stepper motor driven robotic fish based on the New Zealand Snapper (Pagrus auratus). The rear half of the robot was driven at the mid-section by a stepper motor and a torque sensor interposed between motor and robot body measured swimming torque for a range of speeds and tail amplitudes. The candidate DE actuators were based on a double cone device first described by Choi and co workers [6], consisting of two convex conical membrane actuators held apart by a stiff central pin. Actuation on one side resulted in rotation of the robotic segment as depicted in figure 1.Two actuator designs were evaluated: Model 1 supported 6 actuators, three each side (figure 1). For the second design we substituted a long tent-shaped actuator in the place of the trio of conical actuators. Instead of pins, rectangular pieces of acrylic (Model 2) held the membrane tents on opposing faces apart. A double thickness muscle for the Model 2 actuator was also tested. 3M 4905 VHB acrylic tape (St. Paul, USA) was used f 500 µm the tape was stretch carbon powder (XC72 GPface electrodes. Each actua tive and protective layer on electrodes to a power suppl Of the two designs, Mod also doubled the blocked to also had a much greater ran segments.The robotic fish tail was realistic tail amplitudes of torque per cycle was 0.08 N ±22° of angle. Out of the w showed that friction could a These results suggest th magnitude required to drive and under evaluation. In pa sensing: an important step o

Fast-moving soft electronic fish

“…DEs stand out among various soft actuators for their exceptionally fast response and large actuation (26,(45)(46)(47)(48)(49)(50). However, the requirements for high voltages and rigid support frames prohibit their use in designing untethered SARs.…”

A motion control approach for a robotic fish with iterative feedback tuning

“…Prior robotic fish studies mainly focus on the issues of propulsion mechanism [1], actuators [2] and mechanical structures [3]. In this paper, our work differs from these studies in one main respect: we focus on the issue of motion control.…”

Untethered soft robotic jellyfish

“…Different types of smart materials have been utilized to fabricate actuators for soft robotics such as ionic polymer metal composites, DE, shape memory alloys, and gels [12][13][14][15][18][19][20][21][22][23][24][25]. DE are a popular selection, and they have the advantages of quick actuation speed, considerable deformation strain, relatively low cost, lightweight [26,27], and, most importantly, fewer limitations that arise from temperature and environmental issues [28][29][30][31][32]. In this letter, DE is the primary material for the robotic jellyfish fabrication.…”