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1

Multi-direction digital moving mask method for fabricating continuous microstructures

Zhang Z, Gao Y, Luo N, Zhong K, Liu Z

Optica Applicata

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2015

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Vol. 45, nr 1

79--88

EN

The multi-direction digital moving mask method, employing the superposition of the exposure along various moving directions, is developed for fabricating continuous microstructures. The mask pattern corresponding to each moving direction is determined by projecting the target dose profile in the corresponding moving direction. All the mask patterns are dynamically exposed on the same substrate layer by layer so as to form a 3D profile of the exposure dose. The selection criterion of a quantization number and moving-direction number is discussed. For verification of the multi-direction moving method, experiments are performed to fabricate a square pyramid array and square-based microlens array by moving along two orthogonal directions, and round-based microlens array by moving along six directions.

2

Observability and controllability analysis for sandwich systems with backlash

Luo N., Tan Y., Dong R.

International Journal of Applied Mathematics and Computer Science

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2015

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Vol. 25, no. 4

803--814

EN

In this paper, an approach to analyze the observability and controllability of sandwich systems with backlash is proposed. In this method, a non-smooth state-space function is used to describe the sandwich systems with backlash which are also non-smooth non-linear systems. Then, a linearization method based on non-smooth optimization is proposed to derive a linearized state-space function to approximate the non-smooth sandwich systems within a bounded region around the equilibrium point that we are interested in. Afterwards, both observability and controllability matrices are constructed and the methods to analyze the observability as well as controllability of sandwich system with backlash are derived. Finally, numerical examples are presented to validate the proposed method.

3

Three-dimensional microstructures of photoresist formed by gradual gray-scale lithography approach

Luo N, Gao Y, Zhimin Z, Mengchao X, Huaming W

Optica Applicata

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2012

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Vol. 42, nr 4

853--864

EN

We describe a simple and reliable approach, by employing a gradual gray-scale lithography process, which is developed for the fabrication of continuous 3D microstructure. A matrix equation has been built to quantitatively calculate the pattern gray and exposure time by combining the digital micromirror device (DMD) modulation characteristics. To avoid DMD pixel error induced by sampling, we also propose a new quantifying method in accordance with DMD pixel dimension to further improve the fabrication precision of the 3D photoresist profile. Finally, different photoresist microstructures with continuous profile, including axicon array and microlens array, have been successfully fabricated.

4

Real-time mask-division technique based on DMD digital lithography

Luo N., Gao Y., Chen M., Yu L., Ye Q.

Optica Applicata

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2010

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Vol. 40, nr 1

239--248

EN

Digital lithography technique is a promising tool for the fabrication of binary optical element. In this paper, we present the mask-division technique to improve the lithography quality. A piece of high-frequency mask is divided into several pieces of low-frequency binary masks. Then they are imaged on the photoresist successively by using the DMD-based lithography system. Based on the theory of partial coherent light, the intensity distribution in image plane has been simulated. The grating masks with period of 4 žm have been fabricated by using the mask-division technique. Experimental results demonstrate the feasibility of the proposed method as an effective technique for advancing the edge sharpness.

5

Composite adaptive SMC of nonlinear base isolated buildings with actuator dynamics

Luo N., De La Sen M., Rodellar J.

Applied Mathematics and Computer Science

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1998

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Vol. 8, no 1

183-197

EN

This paper addresses the problem of designing a robust active controller for nonlinear base isolated building structures in the presence of unknown seismic excitations, parametric uncertainties and actuator dynamics. A simple adaptation law is introduced to get available upper bounds for the unknown seismically excited nonlinearities. Adaptive composite output feedback sliding mode control schemes are proposed to drive the displacements of the base and structure to their zero equilibrium positions. A numerical simulation example is presented to illustrate the effectiveness of the proposed strategies to a ten-storey base isolated structure under the El Centro earthquake.