The purpose of this study is to develop a human-robot cooperative system that comes in contact with external environment without the contact stability problem. The system is composed of a force-and-displacement detection interface, a shock absorber mechanism to detect contact conditions, a force sensor and a robot. The motions of the system are controlled according to impedance control strategy. In this study, the mechanical device to detect the contact conditions between the robot and the external environment is developed, and a robot motion control method with the proposed device is proposed. The proposed device is composed of following two components: (i) three shock absorbers to absorb contact force arisen from an interaction between a device tip and an external environment; (ii) three laser sensors to detect the displacement of the shock absorbers. The magnitude of the detected displacement is used as control input of the motion of the robot. Stability analyses of the proposed system were carried out to identify impedance parameters applied to the motion of the interface and the robot. Human-robot cooperative contact tracing experiments were carried out to confirm the effectiveness of the system. The experimental results show that (i) the proposed mechanical device and the proposed control method make the control system stable and that (ii) the robot comes in contact with the external environment without the contact stability problem.

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Since a visual navigation system using smart-phones show information on small screens, users attention is likely to be distracted. Therefore, we are considering a portable navigation system by using Audio Augmented Reality. However, if such equipment is used outdoors, very loud wind noise is recorded with the environmental sound. Thus, to reduce this wind noise, we use wind screen and applied signal processing for wind noise reduction. In this paper, we compared noise control earphone and bone conduction headphone. It was shown that Iterative Wiener filtering improves the speech intelligibility score dramatically.

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An application method of Independent Component Analysis (ICA) on vibration of an automobile considering dynamical properties is introduced and its performance is examined through a numerical simulation using a half car model. ICA is categorized in blind source separation method, and originally invented to separate significant signals buried in mixed signals. The proposed method separates road irregularity profile from mixed signals; data set of measured accelerations and calculated double integral of accelerations (displacements), integral of accelerations (velocities), differential accelerations (jerk) and double differential of accelerations. The advantage of proposed method is considering dynamical properties, while original ICA assumes a static mixture. So, it is effective on analysis of source separation in mechanical system including springs and dampers. Also, methods for fixing order of independent components and amplitude are proposed for the estimation of road irregularity. By applying the proposed method, road irregularity with information of amplitude is estimated without knowing parameters such as mass and spring constant.

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This paper describes the development of the analytical procedure of the flexible beam in the absolute nodal coordinate formulation (ANCF) by using the canonical theory. The elastic force in the ANCF has the complicated expression when the strain energy is defined by the coordinates in the element coordinate system. In this paper, we introduce the artificial algebraic constraints into the analytical procedure and make the constrained system on purpose to simplify the derivation of the elastic force. Those constraints lead to the redundant degree of freedom and the primary constraints caused by the definition of momentum. In order to formulate this system, the Dirac's approach with the Poisson bracket is introduced. As a result, the equations of motion are obtained in the form including the expanded degrees of freedom. Moreover, the reduced form of the equations of motion shows that the elastic force of this system is expressed as the right-hand side of the evolutionary equation for the momentum in the canonical equation. The elastic force obtained by this approach is the general expression for the two dimensional problem of the flexible beam defined in the ANCF. The proposed method is applied to the two dimensional beam element with the assumption of the Bernoulli and Euler. Then, the derived elastic force is compared with the previous research. The equivalence of these formulation is shown by the linear strain model.

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This paper shows the implementation of the numerical simulation for the two-dimensional beam in the assumption of Euler-Bernoulli beam formulated by the absolute nodal coordinate formulation (ANCF). The proposed formulation is based on the canonical theory in the constraint system. The artificial algebraic constraints are introduced to simplify the derivation procedure of elastic forces with the nonlinear strain models. In this formulation, the Green-Lagrange strain model can be introduced to derive the elastic forces without the symbolic computer algebra program. This formulation gives two equations of motions, one has the expanded degrees of freedom caused by introducing the intentional algebraic constraints, the other has the reduced form, which can be identified as the equation in the previous researches. The accuracy and efficiency of these equations are examined in the numerical examples. Moreover, this study demonstrates the numerical examples focused on the effect of the strain models on the longitudinal and bending deflections. A linear strain model and two nonlinear strain models are introduced in order to discuss the effect. As the result, it is shown the significant difference between the linear and the nonlinear strain models in the large longitudinal and bending deflection problem.

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This paper describes the formulation of the two-dimensional Euler-Bernoulli beam in the absolute nodal coordinate formulation (ANCF) by using the canonical theory. The elastic force in the ANCF has the complicated expression when the element coordinate system is introduced to derive the strain energy. In this paper, we introduce the different coordinates to express the kinetic and the strain energies. In particular, the kinetic energy is expressed by the absolute nodal coordinates. On the other hand, the element coordinates are introduced to derive the strain energy with Cauchy and Green-Lagrange strain models. The problems caused by introducing the different coordinate systems at once are solved by the canonical theory with the Poisson's bracket formalism. As a result, it is found that the strain energy of this system can be expressed as the simpler forms than the conventional formulation. The calculation results of the dynamic behavior are completely agree with the previous study. Moreover, the calculation times are significantly decreased by this formulation.

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This paper deals with an active acoustic enclosure for high precision measurement apparatuses such as Atomic Force Microscope; AFM, etc. Usually these apparatuses are installed in heavy enclosure boxes in order to prevent the vibration due to surrounding noises. But the weight of the enclosure may limit the installation site because the heavy enclosure needs strong floor. By applying active sound transmission control method to the panels of the enclosure, high-performance and lightweight can be realized simultaneously. We have proposed the active control method of transmitted sound power through a panel using four point force actuators and have both theoretically and experimentally demonstrated the high performance of this method. In this study, the proposed active control method is applied to the five panels of an enclosure and its performance is verified experimentally. The positions of the point force actuators are carefully considered to excite vibration on the panels so that the transmitted sound is effectively suppressed. Furthermore, one quadratically shaped PVDF film stripe is used as an error sensor to suppress the sound pressure inside the enclosure globally. The experimental results in the case that the PVDF film sensors are used are compared to those that a conventional microphone is used.

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In human gait motion analysis, which is one useful method for efficient physical rehabilitation, ground reaction forces, kinetic and kinematic parameters are measured. Recently, it is thought that trans-femoral amputees must regain moving pattern by refined rehabilitation program using loads applied on a prosthetic limb and understanding them is indispensable for gait analysis based on the biomechanical consideration of trans-femoral amputees. For obtaining these data as the unrestrained gait measurement, a novel gait motion analysis system using mobile force plate and attitude sensor has been developed. However, it has been used at only specially-cleaned experimental laboratory. In this study, ground reaction forces and joint moments applied on the lower limb of healthy subjects and trans-femoral amputee are measured and energy consumption is calculated under a wide range of environmental conditions including slope and stairs by the developed system. As a result of the experiments, the patterns of joint moments in the sagittal plane and energy consumption by them are obtained as the remarkably different feature quantities in addition to braking and propulsive forces among the five activities. Finally, the effectiveness of the developed system to analyze human biomechanics during gait and its quantitative evaluation based on those data is validated.

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This study proposes a method of generating the optimized trajectory, which determines change of the displacement of a robot with respect to time, to reduce electrical energy or the peak current value occurred in motors. Previously, a lot of studies tried to optimize the trajectory of a robot, needing its kinetic model to obtain the input torque or energy as the evaluation value. However, the construction of the kinetic model is considerably difficult, because it needs to identify or to measure a lot of specifications of a robot. Thus, the present study proposes the method that obtains the evaluation value by measuring the currents, powers and so on of an actual robot in operation. Therefore, it does not need the analysis of the motion of a robot with the kinetic model. The proposed method optimizes the trajectories with a heuristic procedure by evaluating the measured values. In this study, we addressed the optimization method for continuous path controlled robots and applied it to a commercially available industrial manipulator, confirming that the generated trajectory can reduce electrical energy and the peak current value in a short time.

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This paper describes simulation and experimental results of disturbance responses under a no-backlash drive control, which two motors, as one is for a plus direction and another is for a minus direction, drive a load axis. At first, the plus direction motor and the minus one generate equal offset torque to the load and hold the load axis. When driving the load to the plus direction, the torque of the plus direction motor is made to increase. At this time, the minus one keeps the fixed torque in the reverse direction, forces a cog on the load axis, and cancels the backlash. No-backlash drive was carried out against the disturbance torque of both directions in the simulation and experiments, because a driving motor and a driven motor changed automatically and smoothly. And the vibration of the 1st natural frequency of the mechanical structure should be careful to keep the no-backlash driving.

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Factors in traffic accident include three elements “road traffic environments, vehicle and driver”. Therefore, it is important to analyze the accident on the basis of combination of those three elements. However, the conventional road safety measures have been carried out on the basis of the independently element. In this paper, we make clear the risk of accident that occurred by acting those three elements synergistically. In addition, we propose the visual measures, and verify its effect. As a result, the risk of accident taking into consideration the driver's factor in addition to changing conditions of vehicle and environment was clarified. In the verification of measures effect, the gaze point instruction line had measures effect for the vehicle of drift behavior. Moreover, it was suggested that the cat's-eye have effect for subjects that start steering behavior late.

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Athletes' motor skills are generally improved by various sports training systems using skilled athletes' various activities. Here, we propose a new training system that the use of optimized muscle activation signals, hereinafter called OPTIMAS, as a tool for improving the overall sport performance of engaged subjects. The focus of this study is on an underhand throw of a softball player to verify the validity of the proposed training system. At first, we calculate the OPTIMAS for the underhand throw of a softball based on the subject's physical characteristics using a musculoskeletal model of the upper limb. Then, the subject practices to improve his skills by comparing his electromyogram measured in real time with that of the OPTIMAS waveform produced by optimization. Here, the subject aims to approach the OPTIMAS waveform. The results of the proposed training system show that the subject was much improved the pitching performance in the early stage of the training term.

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Piezoelectric actuators are feasible for vibration control of a flexible rotor because they can provide high forces despite their compact size, and their operating frequency range is quite large. When moderate damping is insufficient for a rotor-bearing system, near critical speeds, excessive vibrations may occur in trial runs of a balancing procedure or the phase angles of rotor displacement may vary considerably with rotational speed, making it impossible to measure their precise values. To overcome these issues, we developed a control system using multilayer piezoelectric actuators in order to suppress the vibration of a flexible rotor and to estimate its modal unbalances simultaneously. The H-infinity controller was designed to achieve robust performance for an uncertainty of the system, and its damping ability was examined in simulation. Large reductions were observed in the response near resonance. Then, steady-state responses of the system excited by sinusoidal forces were calculated to investigate the estimation accuracy of sinusoidal external forces, and good agreement was observed between the estimated and the theoretical results. Furthermore, it was demonstrated that feedforward plus feedback control using the estimated modal force significantly improved the performance of suppression of flexible rotor vibrations compared with simple feedback control.

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As for social infrastructures such as a lot of bridges and tunnels that have been constructed in various places since the high economic growth age of postwar days, deterioration is serious. Taking action to the deterioration of infrastructures is desirable. In this study, we aim to develop the robot that can inspect cracks and corrosion in steel bridge substructures. A four-wheel driving robot for trial purposes has been created with the aid of analysis using software DYMOLA. The robot can climb vertically on a steel wall. Strong permanent magnets are installed on the edge parts in the wheels. This robot does not fall by gravitation when it climbs a steel wall or runs along the ceiling upside down. The running performance of the robot is examined by the experiment.

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The pneumatic driving system, since it resorts the regulation of pressure limited for ensuring safety to the reliability of the regulator, has two problems: one is that it is not virtually interlocked with a stop (power shutoff) function against dangerous errors, and the other is that it is not relieved of risks due to dangerous errors if the pressure monitoring is omitted. This paper shows a configuration example of the pneumatic driving system. The paper implemented FMEA on each component, and, as a result of FMEA, identifies a component that may cause a pressure rise error (dangerous error). Based on this, the paper proposes “monitoring through a window” to be provided at the point where the power regulating unit is decoupled from the driving unit so that pressure rise/fall errors of the power regulating pressure can be monitored. Thereby, the paper deduces that an interlock to avoid dangerous errors can be realized by shutting off the power supply. Furthermore, the paper logically reviews four different interlock systems as to the output shutoff characteristics (unite logical relationship) against dangerous errors, and describes the characteristics and effects of the pneumatically-driven system having an interlock by means of “monitoring through a window.” Lastly, the paper proposes the procedure detailed herein as one of the design guidelines related to the interlock of the pneumatic driving system.

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As the size of electronic mobile devices decreases, the size reduction of cooling components becomes valuable. Because of rotation radius, conventional rotary fans occupy columnar space with some thickness. This occupation is an issue for size reduction of electronic devices. This paper proposes a fan that uses the generation principle of travelling space between two resonantly-driven plates. As the profile of this fan is parallelepiped and thin, the fan can be efficiently inserted in small and thin space of parallelepiped devices. This paper also addresses a realization method of the proposed fan principle. The principle needs two plates and excitation of a sine-shaped mode on each plate. Therefore desired excitation conditions and relative position of the two plates were clarified. Then the principle was realized by an experimental apparatus, and consequently airflow with pulsation was confirmed.

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Impact pressures due to breaking wave sometimes caused serious damages on a ship or marine structures. Impact pressure exerted on the face of a flat plate by a breaking mass was studied experimentally and analytically. Experiments have been carried out with a free-falling water mass apparatus. Recorded time history of impact pressures can be categorized into two typical profiles. One is an impulsive peak with a damped oscillation and the other is without the oscillation. The damped oscillation can be explained by a well-known theory with a trapped air pocket between the breaking mass and the plate. And our analytical model with a curved water surface reveals that a change in momentum due to added mass on the plate yields impulsive force.

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The objective of this research is to analyze vibration mechanisms for developing a seat of high speed railway vehicles which provides good ride comfort to passengers in the sitting state. Therefore, this paper describes the modeling of dynamics model of the seat and the passenger in the sitting state and the vibration simulation using the model. First, seat excitation experiments are carried out to acquire high frequency vibration characteristic of the passenger and the seat. Then, a passenger-seat dynamics model is synthesized. Next, vibration simulations are conducted to clarify the relationship between seat model's parameters and passenger's vibration characteristics by using the synthesized passenger-seat dynamics model. Finally, the seat design guideline for ride comfort improvement of high speed railway vehicle was proposed.

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Several active suspension systems have been developed to improve the ride quality of high speed elevators. However, none of these systems consider suppressing multi modal vibrations when a car moves over the bumps of a guide rail. We propose a structural design of the car that considers controllability and maintains a high performance while reducing vibrations with minimum actuators. The stiffness of the roller guides is designed to minimize the difference of the two phases corresponding to translational and rotational modes: specifically, the lower guide should be twice as stiff as the upper one. Experimental results showed that the proposed system can suppress vibration much more effectively compared to the conventional method using the closed-loop transfer function. The results of time response analysis and experiments also showed that the proposed structure enables a much higher control performance than the conventional one.

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This paper proposes a time variant disturbance observer based on the LuGre friction model for friction compensation. The LuGre model is a dynamic friction model that can express nonlinear characteristics. In the proposed method, an ideal model of a controlled plant without friction is augmented by adding the LuGre model, and the augmented model is used to construct a disturbance observer to estimate friction. Observer gains are derived every sampling period by solving the discrete-time Ricatti equation after locally linearizing the nonlinear term as a function of velocity in the LuGre model. Thus, the observer gains are to be a function of velocity, and the observer becomes time variant. LuGre model parameters used in the controller design have been identified by preliminary experiments using a linear stage driven by a ball screw with an AC motor. In the identification process, a least square method is used so as to minimize the difference between the real friction and the friction generated by the LuGre model. To show the validity of the proposed method, the friction compensation performance of the proposed disturbance observer was compared with that of an existing the type-1 disturbance observer by experiment. The experimental results showed that the proposed disturbance observer can eliminate influence of the friction and is effective to improve positioning accuracy.

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There are a number of long-term scenarios toward envisioning a sustainable society, particularly a low-carbon society. While such scenarios often assume various low-carbon technologies with an aim to reduce greenhouse gas emissions, it is unclear whether the scenarios are feasible from the viewpoint of resource depletion. For example, copper is a critical base metal since introducing low-carbon technologies (e.g., electric vehicle and wind power generator) may induce copper consumption. This paper proposes a method for estimating long-term metal demand based on sustainability scenarios. Our method proposes an integrated model that evaluates world metal demand from two different perspectives - (1) economic development and (2) dissemination of new products, e.g., electric vehicles. As a case study, the feasibility of a long-term energy scenario is assessed from the viewpoint of copper depletion. Results illustrate that the cumulative copper consumption exceeds the copper reserved in the earth by around 2040. The increase in copper consumption results mainly from world economic growth led by developing countries, while the dissemination of electric vehicles has a minor impact on the consumption increase.

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This paper presents a level set-based structural optimization method for electrostatic actuator problems. Electrostatic actuators are electromechanical systems that are actuated by electrostatic forces. The development of MEMS (Micro Electro Mechanical Systems) device production techniques has spurred widespread deployment of small-sized electrostatic actuators. This paper proposes a level set-based structural optimization method for electrostatic actuators that provides optimal configurations with clear boundaries. The main difficulty when applying a level set-based structural optimization method to electrostatic actuator design problems is the calculation of actuation forces, because these appear on structural boundaries that move during the optimization. Thus, the nodes of the finite element mesh may be displaced from the level set boundaries, causing inaccuracies. To accurately calculate the actuation forces on these surfaces, we develop an adaptive meshing scheme so that the nodes closest to the structural boundaries snap to the boundaries after each update of level set function. In our study, the electrostatic and elastic displacement fields are coupled. The sensitivity is derived using the adjoint variable method, and Maxwell's stress tensor is used to calculate actuation forces. We provide two numerical examples to verify the effectiveness of our proposed method.

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Multi-objective optimization that can support agile and flexible decision-making has been highly required to deal with complex and global decision environment. We have proposed, in this paper, a general idea for solving many-objective optimization problem using MOON²/MOON^2R. Those are multi-objective optimization methods relying on a prior articulation in tradeoff analysis among conflicting objectives. To overcome stiffness and shortcomings of the conventional interactive and prior methods, it is developed by the virtue of simple subjective judgment and neural networks for identifying value function. As a great advantage, thus identified value function is amenable to a variety of conventional and recent simulation-based optimization methods. In spite of requiring simple and relative responses, DM's tradeoff analysis becomes pretty difficult for many-objective optimization problem. To overcome this difficulty, we present a stage-wise process that is popular in AHP (Analytic Hierarchy Process). Eventually, the proposed idea makes those methods more general and practical toward recent qualified decision making. After showing a general procedure, a few illustrative applications are provided to verify effectiveness of the proposed method. Finally, total discussion is presented to make the points definitely.

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In the 21st century, as it is important to produce the products with high accuracy, high quality and eco-friendly, the most of manufacturers need several daring plans, unique ideas and new technologies. For example, in machine tool technology, restraint of vibration on the machine tool was required for high accuracy and quality, and several countermeasures using costly equipment and large quantity of electrical energy were used for the restraint, however those countermeasures are not enough. Therefore a countermeasure of vibration for machine tool using alkaline water with polymer was developed and evaluated. Polyethylene oxide was used for the polymer because of the low cost and the safety for health. Relationship between the mixed polymer in the alkaline water and the damping ratio were firstly investigated. And the optimum percentage of the polymer was decided for restraint of vibration on a machine tool. Then the damper structures using alkaline water with polymer were development, and the three dampers were setted for restraint of vibration in the small machine tool; those are the support units, the vise1 and the head stock. Each damper were evaluated regarding noise and vibration on the machine tool and surface roughness on a work piece in the experiment. It is concluded from the results that; (1) the optimum percentage of the polymer for the damper was 6 wt%, (2) the damper structures using alkaline water with polymer were very effective for restraint of both noise and vibration on the machine tool and smoothly surface on the work piece.

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Room-temperature ionic liquids (RTILs) have properties such as high thermal stability, low volatility, non-flammability, low melting point, and broad liquid range, which are applicable to superior lubricants and additives. Previous researches on RTILs as a lubricant have mainly focused on the characterization of various types of RTILs and synthesizing novel functionalized RTILs. Tetrafluoro-borate (BF₄) and hexafluoro-phosphate (PF₆) are the two of the most commonly used anions and RTILs based on the 1-n-alkyl-3-methylimidazolium cation with either the BF₄ or PF₆ anion are known to be effective lubricants. However, both BF₄ and PF₆ have been found to undergo complex tribo-chemical reactions and to produce corrosive acid in the presence of water, which is inevitably present in practical use . To understand lubrication mechanism and design RTILs suited for lubricants, it is important to clarify the molecular behavior of water which mixed into RTILs under lubricating condition.

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Sapphire wafer with pre-groove is cleaved by the irradiation of continuous CO₂ laser. The width of groove is 5 μm and the depth is 15 μm. The groove is made by the irradiation of third harmonic wave of Nd:YAG laser whose wavelength is 322 μm. The pre-groove plays the initial crack which is conventionally introduced by pressing the diamond indenter in laser cleaving. The crack is induced from the pre-groove by the irradiation of laser beam and propagates along the pre-groove and as a result the wafer is divided. The surface roughness of the cleaved surface is very smooth and the surface roughness is smaller than 0.1 μm. Using the pre-groove makes possible to propagate the crack cross the cleaved surface of the wafer.

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