Adaptive role assignment for self-organized flocking of a real robotic swarm

Self-organized flocking of robotic swarms has been investigated for approximately 20 years. Most studies are based on a computer animation model named Boid. This model reproduces flocking motion by three simple behavioral rules: collision avoidance, velocity matching, and flock centering. However, flocking performance depends on how these rules are configured and no guideline for the configuration exists. This paper investigates real robot flocking where individuals can switch their roles depending on the situations. Robots can move as leaders or followers, and the roles are dynamically allocated using stochastic learning automata. The flocking performance is evaluated, and swarming behavior is analyzed in a scenario where robots consecutively travel between two landmarks.     

Motion Control of Caster-Type Passive Mobile Robot with Servo Brakes

In this paper, we introduce a passive mobile robot called prototype Caster-Type Passive Robot Porter (C-PRP), which is developed on the basis of a concept of passive robotics. This mobile robot consists of two casters with servo brakes and one passive rigid wheel. Prototype C-PRP has passive dynamics with respect to the force applied by a human and controls its appropriate motion with the servo brakes. We derive the feasible braking force/moment applied to the robot on the basis of the characteristics of the servo brakes. This paper especially focuses on a fundamental motion control algorithm based on the feasible braking force/moment. We realize the path tracking function and the collision avoidance function as examples by applying the proposed algorithm to prototype C-PRP. These functions are implemented to prototype C-PRP actually, and experimental results confirm its validity.     

A real-time super-resolution robot audition system that improves the robustness of simultaneous speech recognition

This study addresses a framework for a robot audition system, including sound source localization (SSL) and sound source separation (SSS), that can robustly recognize simultaneous speeches in a real environment. Because SSL estimates not only the location of speakers but also the number of speakers, such a robust framework is essential for simultaneous speech recognition. Moreover, improvement in the performance of SSS is crucial for simultaneous speech recognition because the robot has to recognize the individual source of speeches. For simultaneous speech recognition, current robot audition systems mainly require noise-robustness, high resolution, and real-time implementation. Multiple signal classification (MUSIC) based on standard Eigenvalue decomposition (SEVD) and Geometric-constrained high-order decorrelation-based source separation (GHDSS) are techniques utilizing microphone array processing, which are used for SSL and SSS, respectively. To enhance SSL robustness against noise while detecting simultaneous speeches, we improved SEVD-MUSIC by incorporating generalized Eigenvalue decomposition (GEVD). However, GEVD-based MUSIC (GEVD-MUSIC) and GHDSS mainly have two issues: (1) the resolution of pre-measured transfer functions (TFs) determines the resolution of SSL and SSS and (2) their computational cost is expensive for real-time processing. For the first issue, we propose a TF-interpolation method integrating time-domain-based and frequency-domain-based interpolation. The interpolation achieves super-resolution robot audition, which has a higher resolution than that of the pre-measured TFs. For the second issue, we propose two methods for SSL: MUSIC based on generalized singular value decomposition (GSVD-MUSIC) and hierarchical SSL (H-SSL). GSVD-MUSIC drastically reduces the computational cost while maintaining noise-robustness for localization. In addition, H-SSL reduces the computational cost by introducing a hierarchical search algorithm instead of using a greedy search for localization. These techniques are integrated into a robot audition system using a robot-embedded microphone array. The preliminary experiments for each technique showed the following: (1) The proposed interpolation achieved approximately 1-degree resolution although the TFs are only at 30-degree intervals in both SSL and SSS; (2) GSVD-MUSIC attained 46.4 and 40.6% of the computational cost compared to that of SEVD-MUSIC and GEVD-MUSIC, respectively; (3) H-SSL reduced 71.7% of the computational cost to localize a single speaker. Finally, the robot audition system, including super-resolution SSL and SSS, is applied to robustly recognize four sources of speech occurring simultaneously in a real environment. The proposed system showed considerable performance improvements of up to 7% for the average word correct rate during simultaneous speech recognition, especially when the TFs were at more than 30-degree intervals.     

A shape-based similarity measure for time series data with ensemble learning

This paper introduces a shape-based similarity measure, called the angular metric for shape similarity (AMSS), for time series data. Unlike most similarity or dissimilarity measures, AMSS is based not on individual data points of a time series but on vectors equivalently representing it. AMSS treats a time series as a vector sequence to focus on the shape of the data and compares data shapes by employing a variant of cosine similarity. AMSS is, by design, expected to be robust to time and amplitude shifting and scaling, but sensitive to short-term oscillations. To deal with the potential drawback, ensemble learning is adopted, which integrates data smoothing when AMSS is used for classification. Evaluative experiments reveal distinct properties of AMSS and its effectiveness when applied in the ensemble framework as compared to existing measures.     

Design,fabrication and vacuum operation characteristics of two-dimensional comb-drive micro-scanner

We present design, fabrication, and characteristics of two-dimensional micro-machined comb-drive scanner to operate in vacuum. The scanner can be actuated in two orthogonal axes using the slanted electrostatic comb-drive and silicon conductive V-shaped torsion hinges fabricated from a silicon-on-insulator wafer. The resonant frequencies of the inner mirror and the gimbal frame are 40 kHz and 162 Hz, respectively. The resonant frequency ratio is 247. The optical scanning angles for the inner mirror and the gimbal frame are 11.5° and 14° at the operation voltages of 12 and 10 V in 1 Pa vacuum, respectively. These driving voltages are smaller by the factors of about 21 and 3 than those in atmosphere, respectively. The dependence of quality factor on pressure for the inner mirror and the gimbal frame is also experimentally investigated and compared with the theoretical calculation based on air-friction models.     

Interaction of newly defined stress intensity factors for angular corners in a row of diamond-shaped inclusions

This paper deals with a row of equally spaced equal diamond-shaped inclusions with angular corners under various loading conditions. The problem is formulated as a system of singular integral equations with Cauchy-type singularities, where the unknown functions are the densities of body forces distributed in infinite plates having the same elastic constants of the matrix and inclusions. In order to analyze the problems accurately, the unknown functions of the body force densities are expressed as a linear combination of two types of fundamental density functions and power series, where the fundamental density functions are chosen to represent the symmetric stress singularity of $1/r^{1 - \lambda _1 } $ and the skew-symmetric stress singularity of $1/r^{1 - \lambda _2 } $ . Then, newly defined stress intensity factors for angular corners are systematically calculated for various shapes, spacings, elastic constants and numbers of the diamond-shaped inclusions in a plate subjected to uniaxial tension, biaxial tension and in-plane shear. For all types of diamond-shaped inclusions, the stress intensity factor is shown to be linearly related to the reciprocal of the number of diamond-shaped inclusions.     

Color‐tuning projection system for adaptive combination of high brightness and wide color gamut

Abstract— The demand for projectors with high brightness and wide color gamut has been increasing; however, UHP lamp projectors cannot deliver those two qualities efficiently and simultaneously because of its color‐separation system. The newly developed projection system — “Color‐Tuning Projection System” — realizes the adaptive combination of high brightness and wide color gamut with one projector. This projector features a fourth liquid‐crystal panel — “Color Tuner” — with a 3LCD optical engine, which controls yellow light separately from the RGB light of a UHP lamp. This color‐tuner‐based optical engine — “Color‐Tuning Optical Engine” — and a new color‐conversion signal‐processing algorithm — “Adaptive Color Conversion Algorithm” — controls the yellow‐light volume and corrects color‐shifted pixels according to the brightness and chromaticity analysis of the input image, key technologies of the Color‐Tuning Projection System. This additional panel system enables the projector to ach ieve up to 115% higher brightness and 120% wider color gamut according to the input image. This paper presents an innovative design concept, a novel technology regarding brightness and a color‐gamut conversion projection system, and the characteristics of the prototype.     

A topology optimization method based on the level set method incorporating a fictitious interface energy

This paper proposes a new topology optimization method, which can adjust the geometrical complexity of optimal configurations, using the level set method and incorporating a fictitious interface energy derived from the phase field method. First, a topology optimization problem is formulated based on the level set method, and the method of regularizing the optimization problem by introducing fictitious interface energy is explained. Next, the reaction–diffusion equation that updates the level set function is derived and an optimization algorithm is then constructed, which uses the finite element method to solve the equilibrium equations and the reaction–diffusion equation when updating the level set function. Finally, several optimum design examples are shown to confirm the validity and utility of the proposed topology optimization method.     

WOZ experiments for understanding mutual adaptation

A robot that is easy to teach not only has to be able to adapt to humans but also has to be easily adaptable to. In order to develop a robot with mutual adaptation ability, we believe that it will be beneficial to first observe the mutual adaptation behaviors that occur in human–human communication. In this paper, we propose a human–human WOZ (Wizard-of-Oz) experiment setting that can help us to observe and understand how the mutual adaptation procedure occurs between human beings in nonverbal communication. By analyzing the experimental results, we obtained three important findings: alignment-based action, symbol-emergent learning, and environmental learning.