Thermal Behavior of BaTiO3 Particles Synthesized by Plasma Chemical Vapor Deposition

The thermal behavior of nanoparticles BaTiO₃, prepared by a radio-frequency plasma chemical vapor deposition (RF-plasma CVD) method, was characterized by various analysis methods. The BaCO₃ phase was included in the powder as byproducts, which is also observed in hydrothermal BaTiO₃ powder. The BaCO₃ phase decomposed and disappeared by annealing at 873 K for 30 min. H₂O, N₂, CO₂ and H₂, were detected by a thermal desorption spectra measurement from BaTiO₃ powder. The annealed powder became well-crystallized particles without grain growth, although as-prepared powder included polycrystalline particles. We successfully observed in-situ grain growth for BaTiO₃ nanoparticles by thermal transmission electron microscope. At the initial step of normal grain growth, very fine particles with 40–60 nm diameters started to merge into the larger grains around 1083 K. The migration rate was measured by video images and a grain boundary diffusion coefficient D_gb was calculated.     

Surface Chemistry of Lead Titanate and Its Impact on Binder Removal

Carbon residue after binder burnout was characterized for several nonstoichiometric lead titanate powders. Thermal decomposition of the poly(methyl methacrylate) (PMMA) binder was performed in nitrogen at 600°C. A drastic decrease in carbon retention was obtained in the case of the titanium-rich samples. The amount of carbon retention varies from 0.2 mg/m² to 1.2 mg/m² by changing the Pb/Ti molar ratio from 0.92 to 1.08. The surface reaction between PMMA and lead titanate particles was studied by diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS). Surface hydroxyls reacted with ester groups in the PMMA or the methylmethacrylate monomer produced upon pyrolysis. The DRIFTS results showed that titaniumrich samples are less reactive and produce less surfacebound organic groups. Interestingly, titanium-rich samples contained more surface hydroxyls. Isoelectric point measurements, however, show that titanium-rich samples are more acidic. Thus, the reactivity of the surface hydroxyls is determined primarily by their acid-base characteristics rather than their concentration. Lead titanate powder was exposed to MMA vapor in a tube furnace at the indicated temperatures using nitrogen carrier gas as a model experiment. DRIFTS difference spectroscopy and Raman spectroscopy were performed on these samples after the exposure. MMA reacts with lead titanate powder in manner similar to PMMA. Analysis for sp ² and sp ³ absorbance of Raman spectra of these exposed powders at 400°–600°C showed pyrolysis behavior of surface-reacted species. The relative amount of sp ² bonded carbon decreases with increasing exposure temperature.     

Stick-slip motion control based on cutter location data for an orthogonal-type robot

In this article, a new desktop orthogonal-type robot, which has the capacity of stick-slip motion control based on cutter location data, is presented for lapping small metallic molds with a curved surface. The robot consists of three single-axis devices with a high position resolution of 1 μm. A thin wooden stick tool with a ball-end shape is attached to the tip of the z-axis. In order to improve the lapping performance, a novel stick-slip motion control method is developed in the control system. The small stick-slip motion is orthogonally generated in the direction of the tool’s movement. The effectiveness of stick-slip motion control is examined through an actual lapping test of an LED lens cavity.     

iOS application for quadrotor remote control

With the progress of electronics technology, the development of civilian UAV (unmanned aerial vehicle) applications becomes possible. In addition, smartphones have rapidly gained popularity and become very important due to the simple operability and mobility. Hence, there is a need to have an easy and flexible way to control a UAV using such technology. In this study, a remote controller using an iOS device is developed for a quadrotor to enable remote control with easy operations. Four basic programs for obtaining compass information, controlling a gimbal, autopilot function for return, and video preview function are developed and implemented for an iOS device. The basic functionalities of the programs are evaluated and confirmed through experiments using a quadrotor and an iOS device.     

Control of three-link underactuated manipulators using a switching method of fuzzy energy regions

In general, manipulators used for industry and in academic laboratories have actuators to drive each joint. On the other hand, underactuated manipulators handled by our research have some passive or free joints without actuators and brakes. We recently developed a switching method of fuzzy energy regions to control such manipulators. In such a method, it is necessary to design parameters related to energy regions and the gains of some partly stable controllers based on the computed torque method. Here, the switching method is applied for a three-link underactuated manipulator. We optimize such design parameters related to fuzzy energy regions by a genetic algorithm. The effectiveness of the present method is illustrated with some simulations. This work was presented in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007     

Evolutionary Learning of a Fuzzy Behavior Based Controller for a Nonholonomic Mobile Robot in a Class of Dynamic Environments

This paper presents an approach for evolving optimum behaviors for a nonholonomic mobile robot in a class of dynamic environments. A new evolutionary algorithm reflecting some powerful features in the natural evolutionary process to have flexibility to deal with changes in the environment is used to evolve optimum behaviors. Furthermore, a fuzzy set based multi-objective fitness evaluation function is adopted in the evolutionary algorithm. The multi-objective evaluation function is designed so that it allows incorporating complex linguistic features that a human observer would desire in the behaviors of the mobile robot movements. To illustrate the effectiveness of the proposed method, simulation results are compared using a conventional evolutionary algorithm.     

Preparation and dielectric properties of polycrystalline films with dense nano-structured BaTiO3 by chemical vapor deposition using inductively coupled plasma

To clarify the dielectric properties of BaTiO₃ with nanometer size region, it is necessary to fabricate the dense structure composed of BaTiO₃ nanoparticles. In the present study, BaTiO₃ nanoparticles were directly deposited on Pt/Al₂O₃/SiO₂/Si substrate by introducing Ba(DPM)₂ and Ti(OiPr)₄ into an inductively coupled plasma (ICP). The optimal condition for preparing dense structure of BaTiO₃ nanoparticles was investigated by changing the substrate temperature. Single phase BaTiO₃ of perovskite structure was obtained at the substrate temperatures between 773 and 1173 K. The dense structure of BaTiO₃ nanoparticles with particle sizes of about 30 nm was successfully obtained at the substrate temperature of 773 K. At the substrate temperature>873 K, the deposited nanoparticles sintered to be the columnar structure. The ε_r and tan δ of the BaTiO₃ nanoparticles were estimated to be 285 and 6.6%, respectively (1 kHz and 100 mV). The phase of the BaTiO₃ nanoparticles were found to be paraelectric by the measurement of C-V curves. The breakdown field of the dense structure of BaTiO₃ nanoparticles was estimated to be 649 kV/cm according to I-V curves. These features are favorable for applying the structure to the dielectric layer of multilayer capacitors.     

Modular fuzzy-neuro controller driven by spoken language commands.

We present a methodology of controlling machines using spoken language commands. The two major problems relating to the speech interfaces for machines, namely, the interpretation of words with fuzzy implications and the out-of-vocabulary (OOV) words in natural conversation, are investigated. The system proposed in this paper is designed to overcome the above two problems in controlling machines using spoken language commands. The present system consists of a hidden Markov model (HMM) based automatic speech recognizer (ASR), with a keyword spotting system to capture the machine sensitive words from the running utterances and a fuzzy-neural network (FNN) based controller to represent the words with fuzzy implications in spoken language commands. Significance of the words, i.e., the contextual meaning of the words according to the machine's current state, is introduced to the system to obtain more realistic output equivalent to users' desire. Modularity of the system is also considered to provide a generalization of the methodology for systems having heterogeneous functions without diminishing the performance of the system. The proposed system is experimentally tested by navigating a mobile robot in real time using spoken language commands.