Mr. Sahand Sadeghi Profile

Sahand Sadeghi

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Proceedings Article | 22 April 2020 Presentation

Dynamic morphing of a bi-stable water-bomb base origami using an active control strategy (Conference Presentation)

Sahand Sadeghi, Suyi Li

Proceedings Volume 11377, 1137706 (2020) https://doi.org/10.1117/12.2558160

KEYWORDS: Nonlinear dynamics, Manufacturing, Numerical simulations, Feedback control

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Shape morphing is one of the most appealing applications of adaptive structures. Among the various means of achieving shape morphing, origami-inspired folding is particularly advantageous, because folding is a powerful approach to induce three-dimensional and sophisticated shape changes. However, attaining large-amplitude folding is still a challenge in origami engineering. While promising, the use of active materials as a folding activation strategy is limited due to the constant voltage supply that is required to maintain the desired configuration of the structure. One possible solution is to embed bi-stability into the structure. Bi-stability can play two significant roles here: first, it can significantly reduce the actuation requirement to induce shape morphing, and second, it can maintain the shape change without demanding sustained energy supply. In a previous study by the authors, a unique shape morphing (or self-folding) method using harmonic excitation has been proposed for a bi-stable water-bomb base. However, this approach has some drawbacks because the nonlinear dynamic behaviors of origami are quite sensitive to different design parameters, such as initial conditions, excitation parameters, and inaccuracies in manufacturing. In this study, via numerical simulations, we show that by harnessing the intra-well resonance of the water-bomb structure and incorporating a relatively simple feedback control strategy, one can achieve a rapid and robust morphing using relatively low actuation magnitude. The results of this study can lay the foundation of a new category of morphing origami mechanisms with efficient and reliable embedded actuation.

Proceedings Article | 29 March 2019 Presentation + Paper

Analyzing the bi-directional dynamic morphing of a bi-stable water-bomb base origami

Sahand Sadeghi, Suyi Li

Proceedings Volume 10968, 109680S (2019) https://doi.org/10.1117/12.2512301

KEYWORDS: Numerical simulations, Nonlinear dynamics

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Morphing structures have been a subject of much research recently because of their promising potentials in aerospace, wind turbine, and many other applications. There exists many different approaches to achieve shape morphing, among which the origami-inspired folding is particularly interesting in that folding is fundamentally three-dimensional, scalable, and customizable. However, activating and attaining large amplitude folding autonomously are challenging. Active materials, such as shape memory alloys, have been used to activate folding, but they are limited due to the power supply requirement to maintain the folded configurations. One possible solution is to embed bi-stability into the origami structure. Bi-stability can play two significant roles: First, it can significantly reduce the actuation requirement to induce shape morning; and second, it can maintain the shape change without demanding sustained energy supply. In this study, we demonstrate the feasibility of using dynamic excitation to induce shape morphing (or folding) between the two stable states of water-bomb base. For the first time, we derive the dynamic equation of motion for a water-bomb base origami and use it extensively to analyze its time responses under harmonic excitation. Via numerical simulations, we show that by harnessing the intra-well resonance of the water-bomb structure, we can achieve rapid bi-directional morphing using relatively low actuation magnitudes in comparison with quasi-static loading.

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