Chi-Yi Tsai

Heterogeneity-Projection Hard-Decision Color Interpolation Using Spectral-Spatial Correlation

This paper presents a novel heterogeneity-projection hard-decision (HPHD) color interpolation procedure for reproduction of Bayer mosaic images. The proposed algorithm aims to estimate the optimal interpolation direction and perform hard-decision interpolation, in which each pixel only needs to be interpolated once. A new heterogeneity-projection scheme based on a novel spectral-spatial correlation concept is proposed to estimate the best interpolation direction directly from the original mosaic image. Using the proposed heterogeneity-projection scheme, a hard-decision rule can be decided before performing the interpolation. The advantage of this scheme is that it provides an efficient way for decision-based algorithms to generate improved results using fewer computations. Compared with three recently reported demosaicing techniques, Gunturks, Lus, and Lis methods, the proposed HPHD outperforms all of them in both PSNR values and S-CIELAB DeltaEab * measures by utilizing 25 natural images from Kodak PhotoCD

Fast parking control of mobile robots: a motion planning approach with experimental validation

This paper presents a solution to the general parking problem of nonholonomic mobile robots based on motion planning and tracking controller design. A new global tracking controller is first proposed to achieve global uniformly asymptotic stability and local exponential convergence. The parking problem is then transformed into a tracking one by adding a redesigned virtual trajectory to the original trajectory, thus guaranteeing practical stability with exponential convergence. Further improvement in parking performance is obtained through linearization and pole-placement methods. One feature of our approach is that fast convergence in parking and tracking can be treated at the same time without switching between two controllers. Moreover, a tuning function is used to enhance parking performance. With the proposed framework, various tracking controllers given in the literature can be adopted to handle parking problems. The effectiveness of the proposed methods is verified by several interesting experiments including parallel parking and back-into-garage parking.

The characterization of boron-doped carbon nanotube arrays

Abstract In this study, we directly synthesized boron-doped carbon nanotubes (CNTs) by using trimethylborate (B(OCH 3 ) 3 ) as doping sources in a microwave plasma chemical vapor deposition system (MPCVD). Doping boron causes the growth rate of CNTs to decrease. This might be due to the high oxygen content contained in the doping source that induces oxidation of graphite. The bamboo-like nanostructure of the carbon tubes disappeared with boron doping. Raman spectrum shows the higher I D / I G ratio in boron-doped CNTs. This implies the decrease of graphitization in boron-doped CNTs. In addition, doping boron could enhance the field emission property by increasing the current density by more than 30% (from 350 to 470 mA/cm 2 at 2.2 V/μm).

Visual Tracking Control of a Wheeled Mobile Robot With System Model and Velocity Quantization Robustness

This paper presents a visual tracking control design of a nonholonomic mobile robot equipped with a tilt camera. The proposed design enhances various image-tracking applications using an on-board monocular camera, such as human-robot interaction and surveillance. Based on Lyapunov theory, the proposed control scheme not only possesses some degree of robustness against parametric uncertainty, but also overcomes the external uncertainty caused by velocity quantization noise. Moreover, the proposed controller fully works in the image space; hence, the computational complexity and the effects of sensor/camera modeling errors can be greatly reduced. Experimental results validate the effectiveness of the proposed control scheme, in terms of tracking performance, system convergence, and robustness.

Robust visual tracking control system of a mobile robot based on a dual-Jacobian visual interaction model

This paper presents a novel design of a robust visual tracking control system, which consists of a visual tracking controller and a visual state estimator. This system facilitates human-robot interaction of a unicycle-modeled mobile robot equipped with a tilt camera. Based on a novel dual-Jacobian visual interaction model, a robust visual tracking controller is proposed to track a dynamic moving target. The proposed controller not only possesses some degree of robustness against the system model uncertainties, but also tracks the target without its 3D velocity information. The visual state estimator aims to estimate the optimal system state and target image velocity, which is used by the visual tracking controller. To achieve this, a self-tuning Kalman filter is proposed to estimate interesting parameters and to overcome the temporary occlusion problem. Furthermore, because the proposed method is fully working in the image space, the computational complexity and the sensor/camera modeling errors can be reduced. Experimental results validate the effectiveness of the proposed method, in terms of tracking performance, system convergence, and robustness.

Robust Mobile Robot Visual Tracking Control System Using Self-Tuning Kalman Filter

This paper presents a novel design of a robust visual tracking control system, which consists of a visual tracking controller and a visual state estimator. This system facilitates human-robot interaction of a unicycle-modeled mobile robot equipped with a tilt camera. Based on a novel dual-Jacobian visual interaction model, a dynamic motion target can be tracked using a single visual tracking controller without targets 3D velocity information. The visual state estimator aims to estimate the optimal system state and target image velocity, which is used later by the visual tracking controller. To achieve this, a self-tuning Kalman filter is proposed to estimate interesting parameters online in real-time. Further, because the proposed method is fully working in image space, the computational complexity and the sensor/camera modeling errors can be reduced. Experimental results validate the effectiveness of the proposed method, in terms of tracking performance, system convergence, and robustness.

Characterization of bias-controlled carbon nanotubes

Abstract In this study, we focus on the immediately improving quality of growing carbon nanotubes without any pre- or post-treatment. The applied biases during the reaction can directly control the diameter and the quality of carbon nanotubes. This simple step skips additional treatments and is easily used in many deposition systems. The diameter of carbon nanotubes noticeably varies from 45 nm without any amorphous carbon (under +80 V) to 120 nm (under −120 V). Raman spectrums indicate that I D / I G ratio decreases with increasing positive bias. This implies applying positive bias could enhance the graphitization of carbon nanotubes. However, positive and negative bias effects slightly vary the field emission enhancement. In addition, carbon nanotubes grown under positive bias possess better field emission characterization. This results from the following reasons: (I) smaller diameter; (II) pure surface; (III) more graphitized structure; and (IV) higher field enhancement β .

Dynamic visual tracking control of a mobile robot with image noise and occlusion robustness

This paper presents a robust visual tracking control design for a nonholonomic mobile robot equipped with a tilt camera. This design aims to allow the mobile robot to keep track of a dynamic moving target in the cameras field-of-view; even though the target is temporarily fully occluded. To achieve this, a control system consisting of a visual tracking controller (VTC) and a visual state estimator (VSE) is proposed. A novel visual interaction model is derived to facilitate the design of VTC and VSE. The VSE is responsible for estimating the optimal target state and target image velocity in the image space. The VTC then calculates the corresponding command velocities for the mobile robot to work in the world coordinates. The proposed VSE not only possesses robustness against the image noise, but also overcomes the temporary occlusion problem. Computer simulations and practical experiments of a mobile robot to track a moving target have been carried out to validate the performance and robustness of the proposed system.

Speaker attention system for mobile robots using microphone array and face tracking

This paper presents a real-time human-robot interface system (HRIS), which processes both speech and vision information to improve the quality of communication between human and an autonomous mobile robot. The HRIS contains a real-time speech attention system and a real-time face tracking system. In the speech attention system, a microphone-array voice acquisition system has been developed to estimate the direction of speaker and purify the speakers speech signal in a noisy environment. The developed face tracking system aims to track the speakers face under illumination variation and react to the face motion. The proposed HRIS can provide a robot with the abilities of finding a speakers direction, tracking the speakers face, moving its body to the speaker, focusing its attention to the speaker who is talking to it, and purifying the speakers speech. The experimental results show that the HRIS not only purifies speech signal with a significant performance, but also tracks a face under illumination variation in real-time

Field emission from well-aligned carbon nanotips grown in a gated device structure

Vertically well-aligned, high-aspect-ratio carbon nanotips have been directly grown upward on the gated device structure with 4 μm gate aperture. The nanotips rapidly nucleate and grow without any catalyst. In addition, selected area deposition of nanotips is achieved by using a Pt layer as inhibitor in the bias-assisted microwave plasma chemical vapor deposition. The field emission current of nanotips on the gated structure is 154 μA (at a gate-to-cathode voltage of Vgc=50 V). This results from the following reasons: (i) short gate-tips spacing, (ii) small gate aperture, and (iii) the high-aspect ratio of nanotips.