Bio-inspired aquatic robotics by untethered piezohydroelastic actuation

Abstract

This paper investigates fish-like aquatic robotics using flexible bimorphs made of macro-fiber composite (MFC) piezoelectric laminates for carangiform locomotion. In addition to noiseless and efficient actuation over a range of frequencies, geometric scalability, and simple design, bimorph propulsors made of MFCs offer a balance between the actuation force and velocity response for performance enhancement in bio-inspired swimming. The experimental component of the presented work focuses on the characterization of an elastically constrained MFC bimorph propulsor for thrust generation in quiescent water as well as the development of a robotic fish prototype combining a microcontroller and a printed-circuit-board amplifier to generate high actuation voltage for untethered locomotion. From the theoretical standpoint, a distributed-parameter electroelastic model including the hydrodynamic effects and actuator dynamics is coupled with the elongated-body theory for predicting the mean thrust in quiescent water. In-air and underwater experiments are performed to verify the incorporation of hydrodynamic effects in the linear actuation regime. For electroelastically nonlinear actuation levels, experimentally obtained underwater vibration response is coupled with the elongated-body theory to predict the thrust output. The measured mean thrust levels in quiescent water (on the order of ∼10 mN) compare favorably with thrust levels of biological fish. An untethered robotic fish prototype that employs a single bimorph fin (caudal fin) for straight swimming and turning motions is developed and tested in free locomotion. A swimming speed of 0.3 body-length/second (7.5 cm s⁻¹ swimming speed for 24.3 cm body length) is achieved at 5 Hz for a non-optimized main body-propulsor bimorph combination under a moderate actuation voltage level.

Design and characterization of a miniature free-swimming robotic fish based on multi-material 3D printing

“…(3), as C T SBT ¼ pd f max =4L t , tends to overestimate the thrust coefficient, in agreement with previous observations (Aureli et al 2010;Chen et al 2010). Our results are in good agreement with similar experimental studies on vibrating thin films (Aureli et al 2010;Cen and Erturk 2013;Chae et al 2015;Eastman et al 2012;Peterson et al 2009;Prince et al 2010), shown in Fig. 7.…”

“…7. These experimental studies include ionic polymer metal composites (Aureli et al 2010;Chae et al 2015;Peterson et al 2009;Prince et al 2010), with a highly comparable Reynolds numbers, and thin piezoelectric (Cen and Erturk 2013;Eastman et al 2012) and mylar films with a larger Reynold number range.…”

“…Existing designs have explored multi-linked tails actuated by several servomotors (Hu 2006;Phamduy et al 2015;Yu et al 2004), single servomotors with compliant caudal fins Kopman et al 2015;Wang and Tan 2013), smart materials (Aureli et al 2010;Cen and Erturk 2013;Chen et al 2010;Rossi et al 2011), and fluidic soft actuators (Marchese et al 2014). However, due to the utilization of commercially available microcontrollers, batteries, or actuators, these free-swimming robotic fish are often several tens of centimeters in length, ranging from 13 to 46 cm (Aureli et al 2010;Chen et al 2010;Hu 2006;Kopman et al 2015;Marchese et al 2014;Phamduy et al 2015;Yu et al 2004).…”

An Autonomous Charging System for a Robotic Fish

“…In the realm of biologically-inspired robotic fish that mimic complex locomotory patterns of live fish [16][17][18][19][20][21][22][23][24], the problem of autonomous charging is yet to be fully addressed [25][26][27][28][29]. Beyond laboratory [30][31][32] and field [33,34] applications requiring long-term deployment for animal behavior studies and environmental mapping, autonomous charging can greatly enhance informal science exhibits of robotic fish [26,29].…”

Aerodynamic damping of sidewall bounded oscillating cantilevers

“…One of the major hurdles associated with applications such as thrust generation (Aureli et al, 2010a;Cen and Erturk, 2013;Chung et al, 2008;Eastman et al, 2012) or convection enhancement (Acikalin et al, 2004(Acikalin et al, , 2007Kimber and Garimella, 2009) is designing an enclosure within which the vibrating beam is mounted, such that the performance is either unaffected or enhanced. Understanding the effect of the enclosure walls on the oscillatory behavior of the beam is an essential first step in generating guidelines for such designs.…”