Research

New research projects and directions at ASU

Background:

Shape morphing structures that spontaneously transition from planar to 3D shapes are transformative technologies with broad applications in soft robotics and deployable systems. ​ Can we design soft structures and robots of target mechanical properties using planar fabrication technologies? This task is challenging, typically requiring complex local fabrication and actuation processes and a computationally intensive high-dimensional search to obtain desired mechanical properties.

Our unique contribution:

For the first time, we demonstrate the capability of planar fabrication in designing arbitrary target shapes using around 100 iterations. This reduces the computational cost from years to a few hours. The designed structures are applied for building grippers and bio-inspired robots.

Background:

Vortex-induced vibration (VIV) of long flexible cylinders involves a large number of physical variables, such as Strouhal number, Reynolds number, and damping. Due to the nonlinearity and high-dimensionality of the problem, current VIV prediction models have large error bounds, and require selection of input parameters without knowing which ones are most important. How can we leverage the development of machine learning and AI to improve the prediction accuracy and our understanding towards the nonlinear VIV problems? 

Our unique contribution:

A prior-knowledge-based, trend-constrained, machine learning technique is developed for the purpose of identifying those physical parameters which are most useful in the prediction of the VIV of flexible cylinders. We build on top of the prior knowledge obtained from physics-based modeling. For the first time, we reveal the important structural vibration features for flexible cylinder vibration and fatigue damage under fluid flows, such as the importance of traveling wave and multi-mode participation.

Background:

Soft and flexible structures have infinite degrees of freedom and mechanical nonlinearities. Even a slight change in tension may dramatically vary its interactions with fluid flows. You may wonder "Does more tension reduce flow-induced vibration?" "Why does adding damping not always helpful in reducing the peak vibration amplitude?"

Our unique contribution:

Based on power-flow analysis of elastic waves, our study reveals how damping shapes the global vortex-induced vibration (VIV) response of flexible cylinders. Global behavior may vary from full-length standing waves to traveling waves on infinite cylinders. Structural damping rules the standing wave case whereas radiation damping regulates VIV response on very long cylinders. A single scalar equation expresses the balance of power flowing through the structure. Our research answers decades year of mystry in observations from field experiments. 

Background:

Because of the increasing demand for food and the limited supply from land-based food sources, aquaculture is gradually moving from nearshore locations to more exposed open-water locations. The harsh environment in the open ocean places greater stresses on the fish cages used in aquaculture. Fish-farming structures exhibit hydroelastic behavior when subjected to waves and currents. Therefore, accurate predictions of the hydroelastic response of fish cages are of critical importance. However, because of scale effects and inappropriate hydrodynamic models, the nonlinear hydroelastic response of net cages used for fish-farming cannot be analyzed precisely with traditional model testing or combinations of finite element methods (FEMs) and load models.  

Our unique contribution:

In this study, an innovative hybrid method is proposed to determine the hydroelastic response of full-scale floater-and-net systems more accurately. In this method, the net for the fish cage was vertically and peripherally divided into similar interconnected sections with different hydrodynamic parameters. A model of a typical section was subjected to various towing velocities, oscillation periods, and amplitudes in a towing tank to simulate the potential motions of all sections in the net under various currents, waves, and floater movements. By analyzing the measured hydrodynamic force from this test section, a hydrodynamic force database for a typical net section under various currents, waves, and floater motions was built. Finally, based on an FEM, the modified Morison equation and the hydrodynamic force database, the hydroelastic behavior of the full-scale fish cage was calculated with an iterative scheme. It is demonstrated that this hybrid method is able to produce correct hydroelastic response for both steady and oscillatory flows.