Key Engineering Materials Vol. 625

Abstract: A depth sensor or depth camera is available at a reasonable cost in recent years. Due to the excessive dispersion of depth values outputted from the depth camera, however, changes in the pose cannot be directly employed for complicated hand pose estimation. The authors therefore propose a visual-servoing controlled robotic hand with RGB high-speed cameras. Two cameras have their own database in the system. Each data set has proportional information of each hand image and image features for matching, and joint angle data for output as estimated results. Once sequential hand images are recorded with two high-speed RGB cameras, the system first selects one database with bigger size of hand region in each recorded image. Second, a coarse screening is carried out according to the proportional information on the hand image which roughly corresponds to wrist rotation, or thumb or finger extension. Third, a detailed search is performed for similarity among the selected candidates. The estimated results are transmitted to a robot hand so that the same motions of an operator is reconstructed in the robot without time delay.

Abstract: Ginkgo is one of the oldest extant seed plants through hundreds of millions of years of evolution. Ginkgo biloba has many unique properties and applications such as drug development and drinking tea. In recent years hydrophobic surfaces with bionic structures have attracted increasing interest for fundamental research and practical applications. As we all know, the Ginkgo leaf has remarkable texturing surface. In this manuscript, wettability of the bionic surface replicated from Ginkgo leaves was explored. The Ginkgo leaves were used as the original mold, from which microstructures were replicated into the surface of polydimethylsiloxane (PDMS). Compared with the topography of Ginkgo leaves, the topographical surface of PDMS was investigated by optical microscopy and scanning electron microscopy. By measuring the contact angle of polymeric bionic surfaces, there is the increase of ~20 degree than flat PDMS surfaces. Mechanical compression was applied on the polymeric bionic surfaces in one dimension, with the real-time measurement of the contact angle. The experimental results reveal that the wetting behavior of the surface can be reversibly tuned by applied mechanical stress, which induces the change in micro-scale topography. This research provides a guide for fabricating and tuning hydrophobic surfaces for various surface engineering applications.

Abstract: This paper presents a study of cutting strategies on the surface generation in single-point diamond turning of micro V-groove patterns on precision roller drums. An aluminium precision roller drum with a diameter 250mm and 100 long was diamond turned with a V-groove pattern. A series of cutting experiments were designed to study the effect of the variation of various cutting parameters and cutting tool paths on the surface quality in diamond turning of the precision roller drum. The parameters under investigation included the depth of cut, number of steps and the depth for each cut when diamond turning V-grooves on the cylindrical surface of a workpiece. The measurement result indicates that the surface quality of V-grooves machined on the precision roller drums is affected by cutting strategies. The optimal cutting strategy for machining a V-groove pattern on a precision drum with 5µm depth was obtained.

Abstract: In this paper a 6-DOF(Degree of Freedom) vibration isolation platform with structural configuration of 3CPS (3 Cylindrical-Prismatic-Spherical)-1UPS (1 Universal-Prismatic-Spherical) parallel mechanism is proposed. Firstly, the dynamic model is developed through virtual work principle. The transfer function and the complex frequency response function were obtained from the dynamical equation. Then, 36 amplitude frequency diagrams are obtained from the frequency response function. By analyzing the 36 amplitude frequency diagrams, 10 vibration coupling terms were chosen. The range of the spring stiffness coefficient and the range of the damping coefficient of the magneto-rheological damper are determined by analyzing the acceleration transmissibility of the 10 vibration coupling terms. At last, an integrated optimization combining structural and controller optimization is developed. The optimal parameters of the parallel mechanism are obtained through Genetic Algorithm (GA). This work is significant for the prototype design and verification of the vibration isolator.

Abstract: In this paper, we investigated a high lateral resolution common-path Fourier domain OCT system with the use of a chemically etched single mode fiber. In our experiments, single mode optical fiber for 840nm was used for preparing the tapered tips. Our system used a conical microlens that was chemically etched by selective chemical etching technique using an etching solution of buffered hydrofluoric acid (BHF). From experimental results, we verified that our proposed optical coherence tomography system could operate as a common-path Fourier domain OCT (FD-OCT) system. Furthermore, we experimentally investigated the chemical etching process of silica-based optical fiber probes by controlling the etching time when applying chemical etching techniques using hydrofluoric acid. We evaluated the beam profile from fiber probe. From these investigations, it was found that etching time was important parameter for sensor probe of optical coherence tomography.