Analytical structural optimization and experimental verifications for traveling wave generation in self-assembling swimming smart boxes

Abstract

This paper presents vibration analysis and structural optimization of a swimming–morphing structure. The swimming of the structure is achieved by utilization of piezoelectric patches to generate traveling waves. The third mode shape of the structure in the longitudinal direction resembles the body waveform of a swimming eel. After swimming to its destination, the morphing structure changes shape from an open box to a cube using shape memory alloys (SMAs). The SMAs used for the configuration change of the box robot cannot be used for swimming since they fail to operate at high frequencies. Piezoelectric patches are actuated at the third natural frequency of the structure. We optimize the thickness of the panels and the stiffness of the springs at the joints to generate swimming waveforms that most closely resemble the body waveform of an eel. The traveling wave is generated using two piezoelectric sets of patches bonded to the first and last segments of the beams in the longitudinal direction. Excitation of the piezoelectric results in coupled system dynamics equations that can be translated into the generation of waves. Theoretical analysis based on the distributed parameter model is conducted in this paper. A scalar measure of the traveling to standing wave ratio is introduced using a 2-dimensional Fourier transform (2D-FFT) of the body deformation waveform. An optimization algorithm based on tuning the flexural transverse wave is established to obtain a higher traveling to standing wave ratio. The results are then compared to common methods in the literature for assessment of standing to traveling wave ratios. The analytical models are verified by the close agreement between the traveling waves predicted by the model and those measured in the experiments.

Reducing flow separation of an inclined plate via travelling waves

“…As a final note, low-amplitude travelling waves, which are recently generated by piezoelectric actuators (Bani-Hani & Karami 2015), are used in this investigation. It is expected that such low-amplitude travelling waves reduce flow separation on an inclined plate for angles of attack lower than because separation is known to decrease with the decrease of angle of attack for flat inclined plates (Pelletier & Mueller 2000).…”

“…The reduced frequency is , , is the angle of attack and is the non-dimensional time, where is the dimensional time. The maximum amplitude is chosen to be small because travelling waves generated by smart structures have small amplitudes (Bani-Hani & Karami 2015). Herein, symbol denotes non-dimensional parameters, including length, time, velocity and vorticity.…”

“…To investigate if low-amplitude travelling waves, which can be generated experimentally using piezoelectric actuators (Bani-Hani & Karami 2015), can reduce flow separation, the flow separation and aerodynamic performance of 3-D undulating thin inclined plates are numerically investigated. The effect of different wavelengths ( ) and frequencies is discussed and compared with the scaling of vorticity and thrust derived by EBT.…”

“…DeMauro et al (2015) and Jones et al (2018) improved aerodynamic performance by producing a standing-wave oscillation on the suction side of an airfoil. Recently, travelling waves have been created experimentally on flexible structures using multiple piezoelectric actuators (Bani-Hani & Karami 2015). The amplitudes of such travelling waves are low, which has motivated us to numerically investigate the effects of low-amplitude travelling waves on flow separation and aerodynamic performance of a thin inclined plate.…”

Finite element analysis of electroactive and magnetoactive coupled behaviors in multi-field origami structures

“…The concept of origami folding has been drawing intense interest and has inspired novel applications in many different fields, such as biomedical devices, (Hanks et al, 2016, 2017; Mousavi-Khattat et al, 2015), deformable solar cells (Tang et al, 2014; Zirbel et al, 2013), robotics (Cheng et al, 2017; Mu et al, 2015; Onal et al, 2015), stackable paper batteries (Lee and Choi, 2015), and adaptive manufacturing (Yuan et al, 2017). A number of research studies have focused on applications of self-folding structures (Bani-Hani and Karami, 2015; Del Grosso and Basso, 2010; Neville et al, 2017; Silverberg et al, 2015; Wilcox et al, 2015; Yan et al, 2016), where multiple mechanisms are applied to actuate active folding structures, among which are light-responsive polymers (Liu et al, 2012; Ryu et al, 2012), electroactive polymers (EAPs) (Ahmed and Ounaies, 2016a; Ahmed et al, 2015), magnetoactive elastomers (MAEs) (Bowen et al, 2015, 2016, 2017; Crivaro et al, 2016), and shape memory materials (Firouzeh et al, 2017; Hernandez et al, 2017; Zhakypov et al, 2016).…”