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ItemDamped Oscillator under Stokesian Realm and Added-Mass Effects( 2015)This article presents the modeling and simulations of a sphere that oscillates vertically in a high-viscosity liquid. The sphere is connected to a linear spring and given an initial displacement from the equilibrium position to allow free vibration and the sphere undergoes the inertia force, the spring force, the drag force, the buoyancy force, the gravity force, and the added-mass force. In general, the added-mass force is not considered in modeling an oscillator. In this article, the added-mass force is included in the modeling to reflect the reality and the effect of the added-mass force is investigated and discussed. The main contribution of this article is to model and simulate the system and to show that i) the natural frequency of oscillation is reduced by the added mass; ii) the damping ratio is also reduced by the added mass; iii) the return time to the original equilibrium is increased by the added mass; iv) furthermore, the difference on the densities between the liquid’s density and the sphere’s density dictates the degree of the added-mass effect; i.e., the effect due to the added mass is small if the difference on the densities is large.
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ItemTracking of High-speed, Non-smooth and Microscale-amplitude Wave Trajectories( 2016)In this article, an inversion-based control approach is proposed and presented for tracking desired trajectories with high-speed (100Hz), non-smooth (triangle and sawtooth waves), and microscale-amplitude (10 micron) wave forms. The interesting challenge is that the tracking involves the trajectories that possess a high frequency, a microscale amplitude, sharp turnarounds at the corners. Two different types of wave trajectories, which are triangle and sawtooth waves, are investigated. The model, or the transfer function of a piezoactuator is obtained experimentally from the frequency response by using a dynamic signal analyzer. Under the inversion-based control scheme and the model obtained, the tracking is simulated in MATLAB. The main contributions of this work are to show that (1) the model and the controller achieve a good tracking performance measured by the root mean square error (RMSE) and the maximum error (Emax), (2) the maximum error occurs at the sharp corner of the trajectories, (3) tracking the sawtooth wave yields larger RMSE and Emax values,compared to tracking the triangle wave, and (4) in terms of robustness to modeling error or unmodeled dynamics, Emax is still less than 10% of the peak to peak amplitude of 20 micron if the increases in the natural frequency and the damping ratio are less than 5% for the triangle trajectory and Emax is still less than 10% of the peak to peak amplitude of 20 micron if the increases in the natural frequency and the damping ratio are less than 3.2 % for the sawtooth trajectory.
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ItemConceptual Framework of Super Resolution Reconstruction Based on Frequency Domain From Aliased Multi-Low Resolution Images: Theory Part( 2016)Typically, a spatial resolution (Pixel per Area) is an important factor used to define the image quality. Due to the dramatically advance of digital image processing in this decade, high resolution (HR) images are in demand because HR images give more detail and information that directly impact their application performance. Today, there are several techniques that can capture high resolution images such as resolution increment by reducing pixel side. Consequently this high resolution sensor is so expensive and do not proper for general applications. Moreover, due to reducing pixel side, the SNR of sensors decrease. From the signal processing theory, the alternative algorithm for increasing resolution of captured image is called “Super Resolution Reconstruction or SRR” that can solve this problem. Hence, the SRR refers that the process of increasing resolution and improving the quality of image to be higher resolution and better quality. This paper aim to review the ideal and concept of the SRR technique and its SRR observation model but this paper don’t review all SRR frameworks because there are so many proposed SRR techniques. Author hopes that the SRR ideal and concept framework reviewed in this paper will motivate the reader to conduct in this research areas.
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ItemA Conceptual Framework of Super Resolution Reconstruction (SRR) Techniques( 2016)Typically, a spatial resolution (Pixel per Area) is an important factor used to define the image quality. Due to the dramatically advance of digital image processing in this decade, high resolution (HR) images are in demand because HR images give more detail and information that directly impact their application performance. Today, there are several techniques that can capture high resolution images such as resolution increment by reducing pixel side. Consequently this high resolution sensor is so expensive and do not proper for general applications. Moreover, due to reducing pixel side, the SNR of sensors decrease. From the signal processing theory, the alternative algorithm for increasing resolution of captured image is called “Super Resolution Reconstruction or SRR” that can solve this problem. Hence, the SRR refers that the process of increasing resolution and improving the quality of image to be higher resolution and better quality. This paper aim to review the ideal and concept of the SRR technique and its SRR observation model but this paper don’t review all SRR frameworks because there are so many proposed SRR techniques. Author hopes that the SRR ideal and concept framework reviewed in this paper will motivate the reader to conduct in this research areas.