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The aim of this study is to develop a systematic method to suppress residual vibration in overhead cranes that lowers operating performance and prevents automation of the system. In the previous paper, we proposed a control method which is based on the fact that residual vibration is completely suppressed in a linear undamped system excited by an external force that does not contain the natural frequency component of the system. The proposed method introduces the concept of the apparent external force which includes the influence of nonlinearity and damping, making it applicable to nonlinear damped systems as well as linear undamped ones. One possible drawback is that it needs the value of the natural frequency of a cargo whose on-site high-precision estimation is generally difficult. Therefore, this paper investigates the influence of the estimation error on the residual vibration, which reveals that the residual vibration increases with the estimation error. To improve the robustness against the estimation error, we employ two types of ways. One is to increase the number of frequency components eliminated from the apparent external force and the other is to make the derivatives of the frequency component zero at the estimated natural frequency. Numerical simulations demonstrate the effectiveness of these approaches, showing that they exhibit similar performance in robustness except in that the latter is easier to use since it does not need additional parameters to be determined.

In this paper, a new formulation for computing ΔJ using the three-dimensional equivalent domain integral method for finite deformation elastic-plastic problem is presented. It is known that J-integral represents the energy release rate per unit crack extension and is useful for the fracture mechanics analysis of elastic-plastic materials. However, J-integral is only valid under the proportional loading condition in elastic-plastic problem. As a method applicable to the cyclic loading problem, ΔJ was proposed and shown that it is valid for evaluating low-cycle fatigue. ΔJ was initially proposed in experimental studies. Later, a contour integral approach for the evaluation of ΔJ was proposed and many numerical analyses have been conducted by engineers and researchers. However, path-independence of ΔJ was shown under the many assumptions and therefore is valid only for limited problems. In addition, the contour integral for ΔJ evaluation was proposed with assuming small deformation formulation, and it was not clear how it could be extended to the finite deformation problem. In this paper, we present a new formulation for the computation of ΔJ using the three-dimensional equivalent domain integral method. This formulation is based on the three-dimensional J-integral formulation for arbitrary load history and finite deformation that was proposed by the authors. It is shown in this paper that proposed ΔJ evaluation method for finite deformation elastic-plastic problems holds the path-independent property in small/finite deformation under any load histories. Finally, small and finite deformation cyclic elastic-plastic analyses using the finite element method are presented. They show that the present method always holds the path-independent property and can be applied to cyclic elastic-plastic fracture problems.

This paper provides a hybrid simulation (HS) system for pantograph/catenary systems based upon the dynamically substructured system (DSS) method. HS consists of a physical pantograph, an actuator to excite the pantograph head and a real-time simulator for the catenary model. The real-time simulator calculates the displacement of the contact wire using the contact force between the pantograph head and the actuator. Since the actuator is driven by the calculated displacement of the contact wire at the contact point of pantograph and contact wire, HS provides a pseudo dynamical testing method for pantograph/catenary systems. In this paper a multi degree-of-freedom (MDOF) catenary model is adopted, in order to realise wave propagation of the vertical displacement along the wires. To compensate for the dynamic characteristics of the actuator, the DSS method is adopted, which uses both state feedback and output feedback control. A key finding in this work is that the DSS-based HS system is more accurate than the commonly-used inverse transfer function method. Furthermore, in order to realise real-time simulation of the MDOF catenary model, this study uses a modal analysis technique to reduce the dimension of the catenary model. Additionally, the long catenary model is reduced to a 4-span model, and, by copying the state of the wires and contact point, long distance travelling of the pantograph is realised. The proposed method has been validated by simulated HS testing and by HS testing using an actual pantograph at the Railway Technical Research Institute.

As products become large-scale and complex, manufacturing industry faces problems in communication between workers. Among the information to be communicated, design rationale, such as reasons for decided design and the process of consideration leading to the decisions, is rarely expressed in shared design data. This paper proposes a information extraction method of design rationale. While design are conducted, conversations are recorded. Recorded sounds are transcribed using the voice input functions in Google Docs. The transcribed data is analyzed by TF/IDF, which evaluates importance of each word in the script by its frequency and rarity. By extracting sentences that contains important words, it is assumed that most design rationales can be depicted. The proposed method was applied to the design of scissors. The case shows that the proposed method has potential for extracting design rationale.

Since abnormal posture of the trunk due to aging decreases walking ability, the use of a trunk device is required to maintain and improve posture. Wearable assistive devices for the purpose of extending healthy life expectancy must be lightweight, have a simple mechanism, and have a drive system that cooperates with human movements. In our previous study, we developed an adjustable stiffness mechanism to correct the posture of the trunk. In this study, we propose a rotation mechanism that can support trunk rotation during walking and posture correction. The mechanism is a simple structure consisting of a bearing mechanism to reduce rotational resistance and a plastic block connected to pneumatic soft actuator bellows. Using a pneumatic soft actuator provides high adaptability to sudden human movements. This paper explains the outline of the proposed mechanism and the mathematical model of the actuator, followed by a description of the rotational stiffness adjustment method to support trunk rotation movements. Finally, the validity of the proposed mechanism and the effectiveness of the stiffness adjustment method are described based on the results of evaluation experiments.

Marman clamp band separation mechanism is often used to separate a satellite from a launch vehicle. During the separation, the Marman clamp band releases its clamped force and to expose the satellite to a harsh environment of high-magnitude acceleration with high-frequency in a short period of time, which is named by shock environment in spacecraft developments. Estimation of the shock environment is necessary to specify the equipment design condition which is used to design the equipment’s capability to endure shock environment. Empirical methods based on past development shock test data, due to their convenience and simplicity, are often used to estimate the shock environment. However, the accuracy of empirical methods derived by the past shock test data may be affected by the different structural characteristic of the satellite which was not involved in the methods. There are two typical empirical methods, named by conventional empirical methods in this paper, which are widely used in space development. However, there are no discussions and comments regarding the uncertainty of the estimation and this unknown uncertainty will lead to over conservation safety margin assigned when applying the estimated results to specify the design condition of equipment. To answer the questions as mentioned about the conventional empirical methods, first, we investigate the applicability of conventional empirical methods by two different structural characteristics of JAXA satellites, and second, we propose the improved empirical methods for the two different types of structural characteristics based on shock test data during Marman clamp band separation test. Furthermore, a margin used to envelope the uncertainty of individual test data is statistically derived and its applicability is demonstrated from the test data.

This study unveils the effect of ion beam (IB) irradiation on mechanical properties and adhesion of titanium nitraide (TiN) thin films on ultrafine-grained WC-Co cemented carbide substrates. TiN thin films are used for improving wear resistance and lubricity of molds and cutting tools consisted of WC-Co cemented carbides. It is known that the ion beam assisted deposition (IBAD) improve the adhesion strength between the coatings and substrates. In this paper, TiN coatings were deposited on the ultrafine-grained WC-Co cemented carbide substrates by IBAD method that titanium was evaporated by an electron beam (EB) and nitrogen gas was introduced with/without IB. The chemical composition of TiN coatings deposited by IB were investigated by EPMA, XRD and XPS. The nitrogen ratio of TiN increased by IB irradiation in deposition process. The mechanical properties of TiN coatings with/without IB were evaluated by nanoindentation tests and ball-on-disc tests. Dynamic hardness and Young's modulus of TiN deposited by IBAD was 100% and 50% higher than that by conventional vapor deposition (VD), respectively. Friction coefficient of TiN deposited by IBAD was lower than that by VD. The adhesion of TiN coatings was measured by scratch tests. The adhesion strength of TiN deposited by IBAD was 21% higher than that by VD.

The purpose of this paper is to examine which coating material on tool edges is best for cutting spheroidal graphite cast iron containing 35% Nickel (Ni) and to understand the relation between friction properties of the coatings and cutting ability. Heat-resistant alloy materials, such as Ni-based alloy steels and Ni-based alloy cast irons containing a large amount of Ni, are known as difficult-to-cut materials due to high high-temperature strength, low thermal conductivity, and work hardening. In this study, austenitic spheroidal graphite cast iron containing 35% Nickel (FCDA-Ni35) was used as a work material, and shaper machining tests were performed for evaluating cutting abilities of TiN and CrN-coated tools. Furthermore, the friction properties of each coating were compared and evaluated by a ball-on-plate test. It was found that the ploughing force component of the CrN-coat was smaller, and the chip thickness was thinner than that of the TiN-coat, so the cutting ability was good. As a result, the CrN-coated tool has smaller cutting resistance and ploughing force component than the TiN-coated tool, and the friction coefficient of the rake face is smaller. Furthermore, the CrN-coated tool has stable chip formation, thin chip thickness, and good cutting ability on cutting for FCDA-Ni35.

An Excel program that uses tri-diagonal matrix algorithm (TDMA) is proposed to calculate one dimensional steady heat conduction. The program gives analytical exact solutions to calculate multi-layered symmetric flat plate, solid cylinder, sphere, double-sided flat plate, hollow cylinder, and spherical shell geometries. Three different boundary conditions and arbitrary heat generation rates can be applied. Most existing numerical analysis methods use the finite difference approximation. When the thickness and physical properties of adjacent layers are extremely different in the vicinity layers, accurate values cannot be obtained without a very large number of calculation meshes. A large number of meshes increases calculation time, even for simple geometries. However, the analytical method described in this paper does not affect the accuracy of the analysis even if the adjacent media have extremely different thicknesses, because an exact solution is obtained. The effectiveness of the program is demonstrated by solving an example using this Excel program. Furthermore, the method is applied various engineering problems to show how to make simplified heat transfer models to the realistic engineering problems. By using this program to perform heat transfer calculation examples described in JIS, laws and regulations, it was easy to confirm the validity of the regulations and standard settings. The excel program is open to the public for engineering design.

In the construction work, flat plates for building materials are transported by a suspension mechanism using wires in air flow. Then, a flutter could be caused to the suspended plates due to the interaction between plate motion and fluid flow. The violent vibration due to flutter loses the efficiency and safety of the operation. To improve the efficiency and safety of the operation, a detailed understanding of the flutter characteristics is crucial. In this paper, the flutter analysis and experiments of a flat plate suspended by wires in air flow are carried out. In the flutter analysis, the Doublet-point method based on the unsteady lifting surface theory is used to calculate the unsteady fluid force acting on the plate surface. The equation of motion of the plate suspended by wires considering restoring force due to gravity is derived based on the Lagrange equation. The flat plate is modeled as a rigid body. The flutter velocity and frequency are examined through the root locus of the characteristic equation of the system with changing the flow velocity. Moreover, wind - tunnel experiments are conducted to verify the analytical results. The influence of a suspending angle on the flutter velocity, frequency and mode are investigated in detail. Finally, the work done by the fluid force acting on the plate surface is examined.

With the recent spread of 3D printing, its application has been widely discussed from automotive industries to small-scale and individual manufacturing. In general, additive manufacturing is used as a 3D printing process. Using this process, defects in one layer can easily spread to the next layer, deteriorating the overall quality of the final product. Therefore, to ensure the quality of 3D printers while maintaining a large workspace, it is important to monitor the process online. In this paper, a coarse-to-fine strategy is implemented for Fused Deposition Modeling via the dynamic compensation module attached to an industrial robot arm, and the 3D printer-specific multi-ROIs image processing method is proposed for printing monitoring and compensation. The dynamic compensation module consists of two high-speed cameras, an extruder, and a 2-axis actuator that can monitor previously printed material to compensate for the movement of the main system as a high-frequency sub-system. For evaluation of the developed system, a defection detecting test using the multi-ROIs method and dynamic compensation tool path planning test was made. Consequently, it was shown that the dynamic compensation system can be applied by dynamic compensation of the developed 3D printer system, and the prediction and inspection can be made simultaneously by using the multi-ROIs method.

Overhead crane is a product used to transport heavy objects in a factory, and advanced operating skill is required to operate safely and with less equipment failure. However, the shortage of skilled operators has been pointed out in recent years. The purpose of this paper is to develop a method for estimating tense state of rope and weight of suspended load at the same time with the aim of improving the safety of overhead cranes without relying on operator skills. When estimating multiple states using independent estimation models, the issue is the lack of computer storage space and calculation speed due to the increase of the parameters. Therefore, the authors adopted a method that simultaneously estimates several states in a single model. To estimate the tense state of rope and weight of suspended load from the driving signals of the induction motor mounted on the overhead crane, a multi-task neural network that can express the nonlinearity of motor characteristic was used. The teaching data used for learning network parameters was created by using object detection technology to quantify the transportation of markers attached on load block and suspended load. As a result, it was clarified that the rope tension state and the load can be estimated simultaneously by inputting the driving signals of the motor to the multi-task neural network. Moreover, it was shown that the rope tension probability and the estimated load increased synchronously as the motor signals change, and the tension detection was output.

In this paper, the mechanical properties of two-dimensional linked zig-zag structure subjected to in-plane compressive load was investigated. This structure has two counterphase layers consisted of inclined plate. The stiffness and the stored strain energy during the deformation were solved analytically based on the flexible bar theory proposed by Frisch-Fay(1962). In particular, the effects of micro-architecture of the zig-zag model on these mecahnical properties were discussed. The obtained theoretical results agree fairly with FE results. In addition, three cases of the compressive response of a connected zig-zag structure were examined in order to clarify the effective parameters on the equivalent elastic modulus and strain energy stored under certain constraining conditions.

To evaluate stresses including stress concentration at weld toes for fatigue evaluation of complex shape welded structures such as railway bogie frames, previous studies proposed the stress assessment procedure through measuring strains of actual structures by attaching strain gauges with its edges to be at weld toes. This paper evaluates design fatigue strength in terms of the measured stress from published fatigue data and re-analysis of those fatigue tests. The obtained fatigue strength fell into danger side by 12-29% if compared to the fatigue strength estimated based on the current version of JIS. The result also showed that fatigue strength at 2×106 cycles with 0.13% failure probability had a similar value with that at 1×107 cycles with 2.3% failure probability. The fatigue strength in terms of the aforementioned strain measuring system was comparable with those in terms of structural hot-spot stress approach.

Virtual sensor, which is one of the applications of the digital twin, is effective for estimating physical quantities that are difficult to measure. This paper deals with estimation of real-time tool edge temperature by virtual sensor. The tool edge temperature is estimated by inputting the temperature data of the endmill shank obtained from the pyrometer installed in the machine tool to the simulation model created in cyber space. The simulation performed in cyberspace is an unsteady heat transfer analysis, and a state space model with a reduced order of the finite element model using Krylov subspace method is adopted as the simulation model in order to allow real-time simulation. In addition, unknown heat input to the cutting edge was calculated by state feedback control using the temperature data obtained from the pyrometer and the simulation model. The tool edge temperature during cutting was estimated in real time using the developed virtual sensor with the heat transfer analysis block and the input estimation block. The estimated tool edge temperature changed significantly in response to changes such as chipping of the tool edge. The estimated temperature and the measured temperature by the thermocouple method generally matched.

This paper describes computational study to investigate the aero-acoustic mechanism observed in Hartmann generator when under-expanded supersonic jet is blown from a convergent nozzle. The Hartmann generator, composed of a nozzle and a resonance tube with small distance, is known to radiate much higher amplitude of tonal sound than a free jet without any interaction. Aiming at establishing compact and efficient fluidic actuators, the authors tried to clarify the fluid-dynamic and acoustic behaviors of this special device by use of computational tool, i.e., UPACS-LES of Japan aerospace exploration agency（JAXA）. The computational results suggested existence of the JRG mode, an alternative flow motion between the nozzle and the resonance tube. This flow motion drives strong pressure fluctuation and forms sound field in the far field. The computational results complied with the fundamental acoustic characteristics in the former studies, such as far-field sound directivity and radiated acoustic power. Based on the results, it was confirmed that some parameters such as nozzle pressure ratio are predominant to intensify the acoustic power in the far field. Especially, the open-end location of the resonance tube governs the acoustic power when it is between Mach disk and shock cell end in the under-expanded supersonic jet.

In recent years, automobile manufacturing requires both weight reduction for environmental measures and high strength for safety. For this reason, the use of ultra-high tensile strength steel sheets for frame components is increasing. For the application of ultra-high tensile strength steel sheets, it is necessary to pay attention to measures to ensure dimensional accuracy for press forming. Among them, wall curvature countermeasures are very important technologies. In this study, a novel forming method without generating wall curvature was developed using a simple hat model, and then a prototype mold was produced and confirmed. This novel forming method is a combination of the advantages for draw forming and cam bending forming. To form a shape so as not to fracture or wrinkle in a process similar to drawing, and to prevent wall curvature of a vertical wall part of a hat section in a process similar to cam bending. The forming motion consists of downward descent and multi-step sliding while holding the specimen in one forming process. In the FEM analysis before the production of the prototype mold, the conventional forming method and the novel forming method were evaluated from the viewpoint of the wall curvature, and the novel forming method gave the best results with the minimum wall curvature. The evaluation of the formed panel using the prototype mold also gave the same results as the FEM analysis. This paper shows that the developed forming method hardly generates the wall curvature even when the ultra-high tensile steel sheet is used.

This paper presents a conceptual design approach for planar link mechanisms by utilizing continuum topology optimization based on micropolar continuum theory. To effectively simulate the behavior of link mechanisms as continuum elasticity, we introduce a mathematical model utilizing micropolar elasticity. Although topology optimization is commonly used for single mechanical components, extending it to mechanisms with multiple interconnected parts presents inherent challenges. To address these challenges, we model the link mechanism using micropolar elasticity, leveraging its bendiness-related material property, which can apply to topology optimization. Subsequently, we formulate a topology optimization problem to generate link mechanisms using our proposed model. The optimized structure achieves the desired motion and deformation characteristics like traditional linkages with proper degrees of freedom while minimizing the objective function that considers both output motion error and link compliance. The design variables of the topology optimization problem are defined using the Solid Isotropic Material with Penalization (SIMP) method, which is further updated using a gradient-based optimizer. The governing equations of linear micropolar elasticity are solved using the Finite Element Method (FEM). The effectiveness and validity of our proposed method are evaluated through numerical examples, which conclusively demonstrate its ability to synthesize the number, dimensions, and structure of link mechanisms.

This paper presents numerical solution to shape design problems of viscous flow field for unsteady fluid-structure-interactive (FSI) fields. In the FSI analysis, a strong coupled analysis is used to analyze the governing equation of the flow domain and the structural domain considering nonlinearity of strain. A minimization problem for total dissipation energy is formulated for the shape optimization of viscous flow domain in the FSI fields. Also, a shape design problem is formulated to control the flow velocity distribution in the sub-domains of the flow domain. This latter problem can be treated as an inverse problem for minimizing the square error integration between the actual flow velocity distribution and the target flow velocity distribution in the sub-domains. Shape gradient of these shape design problems are derived theoretically using the Lagrange multiplier method, adjoint variable method, and the formulae of the material derivative. Reshaping is carried out by the H1 gradient method proposed as an approach to solving shape optimization problems. Numerical analysis programs for these shape optimization problems are developed by using FreeFEM, and the validity of proposed method is confirmed by results of 2D numerical analyses.

In recent years, condition monitoring methods have been widely developed. Any failure of the overhead catenary system or pantographs will raise the long downtime of railway operation. Therefore, condition monitoring methods of pantograph failure is required with the overhead catenary system. Furthermore, wear mechanism of contact wire has not been clarified yet due to its complex kinematics between contact wire and pantographs. For preventing these failure efficiently and finding out the wear mechanism of contact wire, the authors have developed a method to measure contact forces of all pantographs during trains passing on sections with sensors installed on the catenary. In the developed method, the contact forces are measured from the sum of dropper forces, inertia force of the contact wire and vertical components of the tensile force of contact wire in measurement section. However, some difficult issues have been left in the method measuring the inertial force from contact wire acceleration at some measurement points. This paper proposes a method selecting effective measurement points of contact wire acceleration. LASSO regression, which is known as one of the sparse modelling technique, is applied to the proposed method so that suitable acceleration measuring points are selected to measure inertia force. The results obtained by the proposed method are shown using dynamic simulation data. It also reports that the proposed method is effective even when the measurement frequency is changed.

The axle spring vibration isolator rubber installed on the axle box that encloses the axle bearings is subjected to loads corresponding to the wheel weight and vibration of the axle box during running. It is thought that the running condition of the bogie can be monitored by utilizing the axle spring vibration isolator rubber as a sensor to grasp the load and vibration. Therefore, we investigated a method of monitoring the running condition of the bogie by incorporating a piezoelectric element, which generates electric signals in response to applied loads and vibrations, in the axle spring vibration isolator rubber. In this paper, we made the rubber isolator with a built-in piezoelectric element (RIBP). As a result of running tests with the RIBP installed on a bogie, we found that the running condition of the bogie can be monitored by the time waveform of the electrical signal obtained from the piezoelectric element, and that the condition of the axle bearing can be monitored by the result of frequency analysis. In addition, as a result of examining the actual method of monitoring the running condition of a bogie using a RIBP, it was found that the condition could be monitored even if the number of RIBP installed on the bogie was reduced.

This paper illustrates the development of active self-melting bolt aiming at self-healing tendon-driven robot with high-load endurance. Recent pioneering research has explored several methods for applying self-healing principles for robotics. For example, exploiting reversible crosslinking bonds are a major approach. They enable conventional robots to gain selfrepairing capability from micro damages such as stubs and so on. However, providing a healing module with large load endurance and autonomous healing capability is yet a challenging task. Then, we categorized design challenges to construct such a module. In addition, we introduced some alternatives to overcome the problems. First, we formulated fracture and healing energy ratio to select proper material for active healing structure. The measure leads the authors to the statement that a low melting point alloy is a powerful alternative. Next, the authors insist that bolted joint structure is a candidate for self-healing module with high-load endurance. Finally, we validated the feasibility of the module with tensile tests using motor-driven tendon unit that has been developed by our group. The result showed that proposed structure had healing capability in spite of its low healing ratio. In summary, the paper presents design, manufacturing method and validation for active self-melting bolt.

This paper proposes a novel structure of an axial gap self-bearing motor. The axial gap self-bearing motor controls both axial force and motor torque by using a similar structure to a disc motor, thus simplifying its structure and control system. In this paper, for further simplifying the structure, the number of stator coils is reduced to four for the side stators in a 4-pole disc rotor. Because one of the side stators produces only a 4-pole magnetic flux, all of the stator coils can be connected in series and driven by the single amplifier. Two stators are required to produce continuous motor torque and the bidirectional axial force; therefore, the drive system is composed of eight concentrated coils and two power amplifiers. To obtain continuous motor torque, the permanent magnets are attached to the rotor with a phase difference of 45 degrees between the two sides of the disc. In this study, the axial force and motor torque of the proposed structure are analyzed theoretically, and a control method for the axial force and motor torque is derived. Experimental results show that the proposed motor can control the axial position and the rotation speed simultaneously.

This paper proposes a methodology for estimating airborne noise from a mechanical system under the operational conditions by component tests of a certain active subsystem which is a part of the mechanical system and includes all of vibration sources in the mechanical system. The mechanical system consists of the active and passive subsystems, and supporting structure of the active subsystem is different from that under the component test conditions. Hence airborne noise from the active system under these two conditions are different from each other. Therefore the in-situ blocked force approach is expected to estimate airborne noise under the operational conditions by the component tests, because blocked force is a specific characteristic of the active subsystem and independent from its supporting structure. However it is reported that the in-situ blocked force approach is suitable for estimating structure borne noise and cannot be applied to airborne noise, it has been found that the in-situ blocked force approach can be approximately applied to airborne noise in resonant frequency of the mechanical system. This paper describes theoretical derivation of the approximation error caused by applying the in-situ blocked force approach to airborne noise. Furthermore, the error is evaluated by means of a 3-DOF simple model.

In magnetic hard disk drives, it is important to secure the stability and durability of head–disk interface in relation to a submonolayer lubricant film because the spacing between a head and lubricant surface has to be reduced to ~0.5 nm to achieve a high density recording far beyond 2 Tb/in2. As a succeeding paper of the newly proposed diffusion equation for a submonolayer liquid film, this paper presents a rigorous derivation of the disjoining pressure (DP) from the Lennard–Jones potential (LJP) and formulated the rigorous diffusion equation incorporating the DP. The flow equation for a submonolayer film and viscosity model are the same as in the previous paper. The difference of the rigorous DP and diffusion equation from the previous ones are not significant except in a small thickness regime less than the van der Walls (vdW) distance. Theoretical relationship between the vdW distance in DP and the molecular force equilibrium distance in LJP is elucidated. Rigorous expressions of the conventional DP and diffusion equation for multilayer film are shown. Superiority of the submonolayer diffusion theories to the conventional theory are demonstrated by comparing their theoretical diffusion coefficients with Waltman’s experimental data.

This paper proposes a novel controlled charge source circuit for synthetic admittance of piezoelectric shunt damping system. A design method for the proposed charge source circuit is also proposed. By analyzing the stability of the charge source circuit itself in consideration of the dynamics of the operational amplifier, this paper shows the conventional simple charge source circuit can be unstable because its minimum phase margin is extremely small. Moreover, we show that the minimum phase margin of the charge source circuit itself is greatly improved by the proposed method. In the case of the parameters of the experimental apparatus in this paper, the minimum phase margin is improved from less than 5 degrees to more than 75 degrees. Finally, we carry out the characterization of the developed circuit and shunt damping experiment in order to confirm the effectiveness of the proposed charge source circuit used as the synthetic admittance.

In this paper, we present motion analysis and prototype design of a new omni-directional wheel mechanism "ACROBAT-S". The authors group has proposed a special kind of transmission with a dual-ball configuration for transmit drive powers to wheel shaft and steering shaft of an active-caster mechanism (ACROBAT). In the transmission design, two balls are required where one ball is used for combining the two motor powers to rotate the ball in 2D way while another ball is for distributing the combined power to the wheel and steering. The transmission design enables an omnidirectional robot with three active casters for controls 3D motion of a robot by three motors with no redundancy. To reduce the number of friction drive between balls and rollers in the first design, a new type of ACROBAT with a single ball transmission (ACROBAT-S) is proposed in this paper. The proposed new design with single ball configuration contributes to reduce the number of friction drives between balls and rollers for enhancing an energy efficiency and accuracy of robot movement. To design a proposed mechanism, a kinematics of a ball, a roller and active-caster motions are analyzed to derive a mechanical condition for the prototype design. In this paper, we design and build a prototype of a single wheel and conduct experiments. From the results, it was confirmed that an expected motion can be realized.

This paper studies the feasibility of a hopper for planetary exploration rovers. The proposed hopper is designed based on shape memory alloy(SMA) actuators, because SMA actuators are light in mass compared with traditional electric motors. This paper discusses a design strategy for the proposed hopper to achieve sufficient locomotion capability on planetary surface. Firstly, this paper presents a basic hopper mechanism and its design strategy with SMA physical model. Secondly, semi-optimized design parameters of the hopper are determined based on brute-force searching. Finally, the experimental results show the effectiveness of the proposed hopper for lunar or planetary exploration.

This paper proposes the online learning controller for PID gain tuning to regulate the speed of robot on parallel two-wheeled electric scooter. We define this speed regulation as “speed governing behavior”. The proposed system based on Iterative Feedback Tuning (IFT) contributes the online continuity during learning control not to interrupt and reset/restart the controller. PID gain update during control has the problem that the integral gain change affects the divergence of control input. To this problem, we propose the digital integrator which modifies the previous integrated value of control error. This proposed integrator solves the impulsive control input without any anti-windup or reference shaping. In conclusion, this paper shows the experimental results based on the online learning control and demonstrates the speed governing behavior by life-sized humanoid robot. We finally aim the driving of parallel two-wheeled electric scooter by speed control of humanoid robot.

A semi-active vibration control technique using piezoelectric actuators with switched inductance shunts has been studied. This technique can be used for not only vibration suppression but also energy harvesting. In order to design semi-active vibration control systems and energy harvesters using this technique efficiently, it is necessary to analyze and understand the effects of design parameters on the performance of these systems. Responses of these systems to harmonic disturbance forces can be used for performance evaluation and previous studies analyze periodic responses of semi-active vibration control systems by assuming sinusoidal displacement responses and using method of harmonic balance. However, this control technique induces rectangular control forces and the displacement responses are distorted. Enhancing the control forces leads to stronger distortion of the responses and the validity of the assumption of the previous studies becomes lost. In order to overcome this problem, the authors have proposed to use shooting method which is a numerical method to calculate periodic solutions of non-linear systems without assuming certain forms of responses. This paper presents periodic responses obtained by shooting method with an improved non-dimensional model and the periodic responses are compared with ones obtained by method of harmonic balance. Furthermore, this paper considers not only the periodic responses but also non-periodic chaotic responses obtained by long term simulations with the non-dimensional model.

In this paper, it is confirmed that natural frequency of isolated table is operated and that degeneration, which means that some natural frequencies have the same value, has a bad influence. Pneumatic anti vibration apparatuses (AVAs) support that loaded devices, i.e., XY stages, operate accurately. However, many strict design conditions are imposed on AVAs with six degrees-of-freedom (DOF) which are used on manufacturing floor. There is a risk that the natural frequency of each motion mode approaches, in other words, that isolated table falls into degeneration. This disturbs accurate operations of XY stages. In this paper, AVA with two DOF is used to simplify motion instead of six DOF. First, it is stated that mode control is used to pressure control. Next, position differential feedback (PFB) is proposed. PFB, which is used to the natural frequency control, is applied for each mode. This means that air spring stiffness is considered as each motion mode, and these are deleted or given. It is shown that the natural frequency of each mode can be controlled individually, by calculation, simulation, and experiment. Finally, the degeneration is reproduced to AVA with two DOF by PFB. At this moment, acceleration control which effects to nearby the natural frequency interferes with each other mode. From these results, conclusions are the following: degeneration should be avoided, and mode PFB is effective to control natural frequency of each motion mode. In addition, mode PFB accomplishes not only avoiding degeneration, but also lowering the natural frequency.

This study aims to realize fast disturbance estimation with a Kalman filter (KF). This paper presents a methodology of fast estimation and rejection for some types disturbances. This methodology attempts to estimate the state of mechatronics systems that rejected the influences of disturbance and noise by using KF. Most of known disturbance estimation method is the disturbance observer (DOB). However, the conventional DOB can not estimate the disturbance that is contaminated of noises. Generally, KF is known as state estimation algorithm that can consider influences of various noise. In addition, we had done some previous studies to design a linear KF with disturbance estimation. We obtained a fact that the disturbance estimation speed by the KF is slow from these studies results. Therefore, this paper proposes a new design method of KF with disturbance estimation which includes a design parameter to speed up disturbance estimation, where we have never concerned in this paper with KF design method except linear systems. Finally, we show the design method on the proposed method and usefulness via the simulation results relative to the position control for an simple cart system.

An infrasound sometimes occurs in an industrial field like a paper factory and it becomes a cause of complaints from neighborhood resident of the factory. The infrasound has acoustic features of a long wave length and little effects of conventional countermeasures such as an acoustic absorbent and sound insulator. Therefore once it happens, it has been difficult to do countermeasure. This paper describes that the rotating stall occurred in a fan (IDF: Induced Fan) becomes the cause of the infrasound generated from the EP (Electric dust collector) set in the factory. This is a very scarce and interesting phenomenon. So it is considered of value to describe the event. A lot of measurements were carried out to clarify the cause of this event. As a result, the cause of the infrasound is the resonance of the EP and the cause of the resonance is the rotating stall of the fan. Therefore the countermeasure is to exchange a new fan with P-Q characteristics of a large gradient (∂p/∂Q). As a result, the infrasound disappeared.

This paper proposes an algorithm to generate the augmented reference position trajectory for the realtime 3D robotic phantom system which is used in the quality assurance of the radiation therapy. Quality assuarance is the important clinical part of the radiation therapy which ensures the delivery of the prescribed dose to the tumor of the patient. High precision quality assurance can be a difficult task if the tumor exhibits respiratory induced motion inside the body of the patient, as the motion fluctuates along with time and it suffers large inter-patient difference. This paper presents several algorithms to modify and/or correct the reference tumor trajectory of the patient and generate the augmented reference trajectory sequence for the already existing and tuned control system of the robot manipulator to yield high precision tracking to the original tumor motion trajectory. Experimental validation has been carried out for four lung tumor trajectories in the clinical environment using equipments used in the radiotherapy treatment and it has been shown that the clinical demand on the precision of tumor motion tracking has been satisfied for all the four cases.

This paper proposes a transfer function of rotating shaft system considering both an open crack and anisotropy in bearing support stiffness, which are both fundamental characteristics often observed in the rotating machinery. Due to the interaction of anisotropy in bearing support and rotor crack, vibration component is generated without limitation. In this paper, the order of generated component is evaluated and a transfer function focusing on five vibration components is derived. Each transfer function is analyzed and characteristics of all resonances are explained theoretically. Then, the validity of this derived transfer function is confirmed by comparing with numerical simulation result. Furthermore, the experimental system of the rotating shaft supported by the bearing with anisotropic support stiffness is developed, and the harmonic excitation was added to this system by the active magnetic bearing. Several harmonic excitation experiments were carried out, and the resonances due to anisotropy in bearing support, rotor crack, and the interaction of anisotropy in bearing support and rotor crack were examined. The vibration characteristics of observed resonances showed quantitatively almost agreed results to the expected theoretical results. These theoretical and experimental results clarified the usefulness of the derived transfer function.

Page turning technology is widely used in many applications, such as Automated Teller Machines (ATM) to deal with passbooks, automated book scanning machines to convert paper books to electronic books, and so on. Among them, ATM especially requires high reliability because ATM is used in unmanned operation. Therefore, in this paper, a new page turning roller is developed for a high reliable page turning process on ATM. ATM has to turn both a high stiffness cover page and low stiffness inner pages of passbooks. First, press force of the page turning roller is considered to turn a cover and inner pages stably. Next, we constructed a simulation model about the press force of the page turning roller and considered the shape of the page turning roller by using the simulation model. The developed page turning roller has the desired press force characteristic to turn a cover and inner pages stably. By applying the developed page turning roller, a page turning machine for ATM can stably turn cover pages and inner pages of passbooks.

This paper presents experiments and an analysis of the self-excited vibration of a plate supported by air pressure. In the analysis, the unsteady fluid force acting on the plate is calculated based on the basic equation of a two-dimensional gap flow between the plate and a chamber surface. The basic equation considers the effect of air compressibility in the chamber. The characteristic equation of the system is derived from the plate motion coupled with the unsteady fluid force acting on the plate. The instability condition and vibration frequency are predicted through the root locus of the system with changing air flow rate supplied to the chamber. The experiment consists of a plate supported by the air pressure supplied from a slit on the upper surface of the chamber, where the vibration characteristics are examined. The influence of the slit width and chamber volume on the instability condition of the self-excited vibration is clarified comparing the analytical result with experiments. Moreover, the local work done by the unsteady fluid force acting on the plate (bottom surface) is shown in this paper, and the instability mechanism is discussed. Lastly, the influence of slit width on the unsteady fluid force is addressed by the block diagram showing the phase relationship of pressure fluctuation and plate displacement.

Because of using interference of sound wave, it is difficult to control in whole three-dimensional acoustic field by Active Noise Control (ANC). Instead, around-head-control is investigated in this paper. In this system, two error microphones are set near ears, and noise is reduced around evaluation points locally. This system requires fast adaptation speed of controller following movement of head, and a problem still remains that the control effect during movement becomes worse. Against this problem, we propose Modified Reference signal Method (MRM). This method improves adaptation speed during movement, by modification of filtering of input signal in Filtered-x. The secondary path model that controller requires is interpolated by the method Ohno et al. proposed. There is modeling error of secondary path caused by interpolation and measuring error of it, and this modeling error causes divergence of controller. In this paper, suppression method of divergence is also investigated. Suppression of divergence is executed by addition of penalty term to evaluation value, and it is equivalent to ridge regression mathematically. Proposed method requires a large number of matrix calculations, therefore reducing method of computational complexity according to acoustic characteristics is also investigated in this paper. The validity of the proposed method is shown by numerical simulation and experiment.

Karman vortex shedding occurs when the gas passes through the duct with tube bank of the heat exchangers, such as gas heaters and boilers. Very high level sound in called “self-sustained tones” occurs due to the interference of the vortex and the sound field in the duct. In general, baffle plates are used to suppress the self-sustained tone. However, it is difficult to use them effectively, because insertion conditions have not been established. Then, perforated plates are installed in both sides of the duct to suppress the self-sustained tones. As a result, it was clarified that the perforated plate could suppress the self-sustained tone as expected. The perforated plates are generally used with a cavity to obtain the suppression effect effectively. However the perforated plates change the acoustic natural frequency of the sound field of the duct. In previous paper, this was not referred. This paper aims to clarify the role of the perforated plates when it changes the acoustic natural frequency of the duct. In this study, one dimensional duct will be used for simplicity and the relationship between the aperture ratio and the acoustic natural frequency will be obtained analytically and experimentally. As a result, it was clarified that the analytical results are in good agreement with the experimental ones and the plates with holes had a role of acoustic damping in calculation of the acoustic natural frequency of the one dimensional sound field like a duct with plates with holes.

Recently, proceeding of the aging society has encouraged research and development of power assist systems. The authors' research group studies on the assist system control using an assist cart as a rollator. The merit of the proposed system is the aging people walk by themselves using the cart as the assisting tool and it helps anti-aging. Most serious problems of the proposed system are the avoidance of fallings and collisions without losing operability. To solve the problem, this paper proposes the remote control system taking operators' safety and operability into account. The remote control has a possibility of the establishment of the cost-effective multiple target control systems by reducing the requirement for each control target system. However, because of the limitation of communication data capabilities, the controller cannot grasp the state of the controlled object completely. To grasp the state and keep the safety, the authors apply an evaluator in the remote control system. It detects the effect of the uncertainty and keeps the controlled object safe. In addition, as an interface for the users to avoid the collisions, this paper applies the stiffness control. Introducing the virtual spring into the control system, the proposed system prevents the controlled object to collide the obstacle, without losing operability. Based on an application example for the one-dimensional assist rollator collision avoidance, this paper reveals the practicality of the proposed system by conducting experiments and the simulations. The result shows the proposed way is one of the effective ways for applying a remote control system to the assist system problem.

This paper analyzes metal-mold polishing by human hands. The metal-mold polishing generally requires long experiences about polishing works. Although experienced persons have many excellent skills, it is a little difficult to evidently teach them to beginners in words because most skills are considered to depend on their physical and intuitive memories. Thus we attempt to bring out the characteristic skills about metal-mold polishing by human hands. This paper mainly discusses the difference of polishing skills between experienced persons and beginners. First, a new data acquisition tool is developed to obtain polishing data, which is designed similar to old tools used by experienced persons. The tool basically consists of a small grasping spatula, a grindstone chip, a force sensor, and a 3D motion sensor. Second, basic data acquired from the developed tool are explained, and the estimation method about some kinds of data is proposed, which are not directly obtained from the sensors attached to the tool. Third, the characteristics between experienced persons and beginners are carefully compared from the view of the tool angle, the polishing velocity, the pressing force, and the mean power of polishing. Then, we focus on the phase trajectories between the polishing position and velocity, and the resistant forces appeared in forward and backward polishing. In order to understand the interesting phenomena about the phase trajectories and resistant forces, a simple dynamical model is newly assumed, and the model evidently explains the phenomena. Finally, the main results and future works are summarized.

Tapping screw fabricates the female thread due to plastic deformation during screw rotation. Since the tapping screw skips the preliminary fabrication of female thread, it is widely used for the tightening in the fields of such as electric parts and car parts. However, there is a few theoretical studies for its self-tapping process and loosening proof. In this paper, we have investigated the mechanism of tapping torque and shape of female thread using three-dimensional finite element analysis. In addition to the plastic flow caused by the friction force due to the rotation of male thread, the plastic flow at the top of male thread separated by the up and down directions occurs. That contact at thread top mostly contributes the torque of self-tapping. Also, plastic flow along the lower surface of frank thread separated by the outside and inside radial directions creates the characteristic shape of female thread. The analysis results well reproduce the tapping torque and the shape of female thread. We also investigate the loosening proofs due to shear loading both for tapping screw and normal screw using there-dimensional finite element analysis. The shape of female screw obtained by self-tapping analysis is incorporated into the analysis model. It is found that the loosening proof of the tapping screw is superior to that of normal screw since contact at the top of thread in the lower part of tapping bolt inhibits the thread slip.

Maintenance is one of the important issues in control systems. It is possible to take appropriate measures for maintenance of the control system by detecting change in characteristic of a controlled object. In this paper, three methods are proposed to detect characteristic change of the controlled object by applying the data-driven control FRIT. The method 1 detects the characteristic change of the controlled object based on a P gain value or an I gain value tuned by FRIT. The method 2 retunes parameter values of a reference model that describes desired response defined in FRIT so that the response is fastest within a range where a P gain value or an I gain value does not exceed each upper limit value. Then the characteristic change of the controlled object is detected based on the retuned values. The Method 3 detects the characteristic change of the controlled object by automatically tuning the parameter values of the reference model with maintaining current values for a P gain and an I gain. Performance of the proposed methods was evaluated by applying the methods to a prototyped small heater. An efficiency of the small heater was pseudo-deteriorated by covering a thermocouple with caps of various materials and thicknesses. A relation between the efficiency and the parameter values tuned by the each method at the pseudo-deteriorated condition was approximated by a linear function, and a correlation between the efficiency and the parameter values was evaluated with coefficient of determination. ζs were estimated from each characteristic change detection parameter values with the obtained linear functions, and the errors between the estimated value of ζ and the measured value of ζ were evaluated under two pseudo-deteriorated conditions. The coefficients of determination of the three methods were more than 0.95. The errors were smaller than 4%. It was confirmed that the proposed methods were effective for detecting the characteristic change of the prototyped small heater.

The on-board components mounted on the structural panel of spacecraft are exposed to a severe random vibration environment, mainly induced by the acoustic excitation of the panel structure due to the large acoustic noise from the launch vehicle. To verify the components' resistance against the vibrational environment, random vibration tests of the components are generally performed at the excitation level based on vibroacoustic prediction. In order to consider the prediction uncertainty, there actually needs to add a margin, which often poses an excess of design and testing. JAXA has been involved with predicting wide frequency band vibro-acoustic behavior of the structural panel using SEA (Statistical Energy Analysis), in which we have to add margin to take into account spatial and frequency bandwidth uncertainties. These kinds of uncertainty margin may result in over conservative margin and causes costly over conservative design. To reduce the over conservative margin in SEA method, in this paper, a wavenumber expression of joint acceptance method calculated by fast Fourier transform approach on finite element model parameter of panel, i.e., mode frequency and mode shape is proposed. The proposed method is applied to two structural panels of actual spacecraft and compared with acoustic test results. It is shown by comparison with the test result of an actual panel that the proposed method achieved less conservative prediction in each individual component mounting location rather than enveloping every mounting location that SEA calculates.

Sequential press forming of thin sheets is a method in which different locations within a single workpiece are pressed in sequence, and is used to manufacture large structures, such as storage tanks. In the sequential press forming, it is important to estimate bending-defect areas efficiently because a product shape can be corrected not by repairing dies but by only re-pressing the bending-defect areas in the subsequent process. At present, high skill is required to determine bending-defect areas because they are judged by measuring a gap from a template. In this study, a versatile method to estimate bending-defect areas in products obtained with sequential press forming is proposed. Specifically, a cosine similarity is calculated between the product shape and templates of ideal shapes with known defects prepared beforehand. A cosine similarity is calculated based on curvatures. Bending-defect areas are then evaluated from the magnitude of the deviation from the average of the multiple calculated cosine similarities. This paper also presents a procedure to calculate the threshold for estimating bending-defect areas by the proposed method. The effectiveness of the proposed method was confirmed through case studies that considered virtual products and actual workpieces. It was confirmed that the proposed method can estimate bending-defect areas and excess or deficiency of bending even when local deformation and measurement noise exist.

Journal bearings are an important mechanical element of rotating machines and support the rotor system by oil film reaction forces. As rotational speeds increase, the shear heat of the oil film causes a significant temperature distribution on the journal surface. As a result, bending of the shaft occurs and vibration modes called Morton effect are generated. The Thermo Hydrodynamic Lubrication (THL) model is used for analyzing of lubricant, and one of the authors has modified and applied it as a simple unsteady model to efficiently analyze the temperature, viscosity, and pressure distribution of the oil film , maintaining computational accuracy. In this paper, the simplified THL model is modified with the boundary condition that both the bearing and journal are adiabatic (ADIADI) in order to construct an accurate and efficient analytical model of the Morton effect in the rotor system. The journal vibration is assumed to be small, and dynamic coefficients of journal bearing are derived considering the temperature distribution. Eigenvalue analysis is performed using these dynamic coefficients to predict the onset speed of instability of the rotor system. The validity of the eigenvalue analysis is verified by direct numerical integration simulation.

Pneumatic rubber artificial muscles are nearly ideal for power assistance, medical care, and rehabilitation due to their lightweight drive unit made of rubber, which is soft and safe for human use. However, they have complex nonlinearities, including input saturation, hysteresis, and changes in static characteristics due to shrinkage. Additionally, when used with a human subject, the artificial muscle control system’s characteristics may vary based on the person’s physique, fitness, temperature, and the rubber’s deterioration. Therefore, it is desirable to be able to auto-tune the PID and other controllers in a short time before use. Data-driven controls such as FRIT and VRFT are suitable for auto-tuning in a short time. Among them, V-Tiger presented a procedure for predicting the actual closed-loop response and its Confidence interval. However, V-Tiger is not applicable to nonlinear systems with input saturation. This paper describes a procedure for (1) tuning PID gains by predicting the closed-loop response with V-Tiger in the presence of input saturation, (2) obtaining Confidence intervals for the predicted response affected by input saturation, and (3) how to use the Confidence intervals to apply this method to nonlinear systems.

Research and development are actively conducted for recent advances in the self-driving and unmanned vehicles, along with further efficiency and safety. In such fields, obstacle avoidance is frequently addressed in control applications through the concept of active safety technology. This paper investigates the real-time optimal obstacle avoidance control that the optimal path generator embedded model predictive controller. By offline computation, a large number of optimal obstacle avoidance control solutions are calculated to generate the supervised learning data for the deep-learning neural network used for the optimal path generator. Then, constructed optimal path generator is embedded in the model predictive controller to generate the reference command for the tracking task during the optimization process. The utility of the proposed controller is evaluated by both the numerical simulation and experimental testing of the obstacle avoidance maneuver of the micro-unmanned vehicle. Results show that the proposed real-time optimal controller successfully performs obstacle avoidance.

Three-dimensional (3D) elastic vibrations in railway vehicle carbodies sometimes negatively impact ride comfort, and efficient numerical analysis methods are required to study effective countermeasures. The authors proposed in their former work a new vibration analysis model in which the railway vehicle carbody is modeled as a box-like structure composed of elastic plates, straight beams, and curved beams. This model can easily express complex 3D vibration shapes observed in actual carbody, such as the interaction between the roof, floor, and side structures. In this paper, an improved version of the previous model is proposed, firstly. Then, a series of numerical studies are carried out by changing the structural properties of each face of the carbody shell, including cross-sectional shapes or bending rigidities, to investigate their effect on the natural frequencies. According to the numerical results, it has been shown that the side pillars primarily affect the modes with cross-sectional deformation of the carbody. Additionally, as a general tendency, the bending and shear rigidities of the roof panel have been found to have a relatively significant effect on the first bending and the diagonal distortion modes.

In this paper, the prediction of crack propagation with two cracks using machine learning is described. The analysis results of crack propagation by s-version FEM (s-FEM), which combines the automatic mesh generation technique, are used for generation of training and validation datasets. Plural crack propagation with the different vertical distance between the two cracks as a variable are analyzed. The analysis cases are divided into training and validation datasets. In training process, the input parameters are the coordinates of 4 crack tip, the output data are crack propagation vectors, the number of cycles for crack propagation of 0.25 mm. Initial crack configurations should be specified. After the specification, the predictor iteratively predicts crack propagation direction and the number of loading cycles. A prediction accuracy depends on the training datasets, which contains 0.25 mm length of each crack propagation in this study. To improve prediction accuracy, the data augmentation is effectively applied. In case of plural crack interaction, when the crack tips close each other, the accuracy gets worse and worse. Reducing datasets which satisfy the crack coalescence condition, it is shown that the prediction accuracy is improved. Even if training datasets are not enough number for accurate prediction, it is shown that the prediction accuracy is improved by the data augmentation.