Abstract
Smart materials and soft robotics have been seen to be particularly well-suited for developing biomimetic devices and are active fields of research. In this study, the design and modeling of a new biomimetic soft robot is described. Initial work was made in the modeling of a biomimetic robot based on the locomotion and kinematics of jellyfish. Modifications were made to the governing equations for jellyfish locomotion that accounted for geometric differences between biology and the robotic design. In particular, the capability of the model to account for the mass and geometry of the robot design has been added for better flexibility in the model setup. A simple geometrically defined model is developed and used to show the feasibility of a proposed biomimetic robot under a prescribed geometric deformation to the robot structure. A more robust mechanics model is then developed which uses linear beam theory is coupled to an equivalent circuit model to simulate actuation of the robot with ionic polymer-metal composite (IPMC) actuators. The mechanics model of the soft robot is compared to that of the geometric model as well as biological jellyfish swimming to highlight its improved efficiency. The design models are characterized against a biological jellyfish model in terms of propulsive efficiency. Using the mechanics model, the locomotive energetics as modeled in literature on biological jellyfish are explored. Locomotive efficiency and cost as a function of swimming cycles are examined for various swimming modes developed, followed by an analysis of the initial transient and steady-state swimming velocities. Applications for fluid pumping or thrust vectoring utilizing the same basic robot design are also proposed. The new design shows a clear advantage over its purely biological counterpart for a soft-robot, with the newly proposed biomimetic swimming mode offering enhanced swimming efficiency and steady-state velocities for a given size and volume exchange.
Highlights
Electroactive polymers (EAPs) have emerged and grown into a vast and diverse field of research, with numerous potential applications in soft robotics and smart materials
For the geometric model the three half-axis dimensions a, b, c defining the median surface of the ellipsoid body have an initial dimension of 31.75 mm, and a rate of change in the z-axis dimension of 40 mm/s during the contraction phase was chosen, with the relaxation phase being complementary such that the volume at the end of each swimming cycle returned to its initial state as discussed in section Kinematics of swimming jellyfish
The material properties of the ionic polymer-metal composite (IPMC) were chosen from literature and use a Young’s modulus value of 249 MPa (Trabia et al, 2017), while the shell was assumed to be made of castable silicon with an approximate modulus of 125 kPa
Summary
Electroactive polymers (EAPs) have emerged and grown into a vast and diverse field of research, with numerous potential applications in soft robotics and smart materials. IPMCs have are capable of exhibiting large mechanical deformations in response to a relatively low voltage (Shahinpoor and Kim, 2001; Bar-Cohen, 2002; Wallmersperger et al, 2007; Jo et al, 2013; Shahinpoor, 2015), making them attractive for compact, low power soft robotics. Their ability to actuate in water (Kim et al, 2007; Yim et al, 2007; Brunetto et al, 2008; Abdelnour et al, 2009) has focused the soft robotics development heavily on aquatic animals. The biomimetic applications of IPMCs range from small scale biological structures such as cilia (Sareh et al, 2012) all the way up to full size robots (Shen et al, 2015b)
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