In recent years, more efficient internal combustion engines have been required to solve global warming problem. It is necessary to realize the non-axisymmetric non-cylindrical inner cylinder machining of about several tens of micrometers, which is difficult to be solve. Moreover, there is no inner cylinder machining method and machine tool machining this shape. In this research, we develop a spindle motor that can generate radial force and rotational torque at the same time. This makes it possible to control the rotational motion of the spindle and the axial position of the spindle simultaneously. Therefore our main research purpose is that we develop a high-performance spindle to machine the inner cylinder shape with high accuracy by controlling the precession of the spindle and the rotational angler position of the spindle. First, building a control model required for position control of the tool tip point set on the spindle, then estimate the disturbance using a disturbance observer, and create a control system that can cancel the actual disturbance by feedback of the estimated disturbance value. To validate the proposed method, the active center position control of the spindle axis was carried out comparing with a control model. After that, applying disturbance to the spindle during rotating, and the performance of the positioning control is evaluated.

The development period can be shortened by applying model-based development, which has been attracting attention in recent years, to machine tools. In this research, we will identify the necessary parameters in order to apply the model-based development to the moving table by ball screw drive system, which is indispensable for machine tools. Guide friction, friction torque, rigidity, and damping coefficient were identified using a rotary encoder, linear scale, and force gauge. Simulation is possible with the identified guide friction, starting torque, stiffness, and damping coefficient. In the future, it will be possible to estimate the cutting force and control using a disturbance observer.

This study will develop a desktop machine tool that can process steel materials with high precision. To reduce the size of conventional large-scale factories and increase production efficiency, it is necessary to reduce the size of machine tools. However, small machine tools have low rigidity and are easily deformed, thus machining hard materials is difficult. Therefore, a 3-axis small NC milling machine that can cut steel has been prototyped. However, due to insufficient rigidity, the machine body is deformed during machining, resulting in insufficient machining accuracy compared to ordinary large machine tools. Therefore, in this study, the method for reducing the machining error of the prototype by optimally controlling the tool path according to the body’s deformation estimated by cutting forces is proposed, and improvement the effect by applying the method to the prototype machine. As a result, the processing error was improved by the proposed method.

Inconel 625 is an alloy consisting of Ni with Cr and other elements. Inconel 625 has the advantages of high-temperature strength, oxidation resistance, and corrosion resistance, and therefore is used in the places exposed to harsh environments such as aircraft jet engines and chemical plants. However, due to its low thermal conductivity, high tool affinity, and susceptibility to work hardening, it is difficult to machine and is considered as a difficult material to cut. While the research on turning Inconel 625 has been conducted, there are fewer examples of the research on cutting compared to turning. Therefore, in this study, in order to improve the efficiency of the cutting of Inconel 625, the cutting process was carried out under two kinds of rotation speeds and four kinds of feeds per flute for high feed machining using a coated carbide end mill. The tool life was compared from the tool wear and the surface roughness of the machined surface, and the effect of feed rate on the tool life and surface roughness was clarified. In addition, the state of tool welding and coating peeling were observed, and the occurrences in welding due to differences in feed rate on tool life were clarified.

Titanium alloys are widely used as implant materials because of their excellent corrosion resistance and strength, light weight, and high biocompatibility. The Young's modulus of titanium alloy is about 110 Gpa. Therefore, the bone strength around the insertion implant lowers and looseness are generated by the bone resorption by the stress shielding. Not only biocompatibility but also Young's modulus near the bone are necessary for the implant material. The niobium-titanium alloy is composed of Nb element and Ti element, and has characteristics of very low cytotoxicity and Young's modulus of about 60 GPa, which is relatively close to human bone. However, this alloy is difficult to cutting because of its low thermal conductivity and high weldability. In this study, the influence of difference cutting environments on tool life was investigated by milling of niobium-titanium alloy using round tool. It was clear that the MQL method can be extended the tool life by suppressing the generation of adhesion due to the lubrication effect of the oil mist. Moreover, it was clear also clear that the flank wear on the end cutting edge side rapidly progressed, and that the surface roughness increased.

AMS6260 is one of the materials specified in the U.S. Aerospace Materials Standard, which is mainly composed of Fe and contains Ni, Cr, and Mo. It is used as a material for parts that require high toughness, such as gears of aircraft engines and large parts of aircraft. Although the heat treatment hardenability and high toughness have been shown to be advantages of AMS6260, there are few research examples. In this study, we focused on the heat treatment hardenability of AMS6260, and AMS6260 after the heat treatment process is cur using a radius end mill on a NC milling machine under some cutting conditions. The tool life after cutting was evaluated from the images of flank wear taken by a microscope, and the surface roughness of the bottom surface of the machined part was measured. As a result, the cutting characteristics of AMS6260 using the radius end mill was clarified.

In this study, the creep rupture time and creep properties of Ti43Al5V4Nb were evaluated at 1033 K (760°C), which was designed usage limited temperature and 923 K (650°C), which was close to the usage temperatures for the material at actual components. The creep strain curve at 923 K showed a smaller percentage of tertiary stage creep than that at 1033 K. The fracture surface of the crept specimen at 1033 K had many dimples due to ductile fracture mode, and the fracture surface at 923 K showed intergranular cracking due to brittle fracture mode. Creep rupture time was calculated using the θ method proposed by Evans et al. By considering both stress and temperature in the θ parameter, the minimum strain rate under arbitrary stress and temperature conditions could be calculated. The creep rupture life in the range from 923 K to 1073 K could be predicted within a factor of 2 scatter band by using the Monkman-Grant rule.

This is a report on a study of simple design method for the snow melting system where geothermal energy is transported from underground to road surface by circulating water in winter, while solar heat is collected on road surface and stored into underground in summer. This system showed enough heat storage and snow melting power for road surface area of several thousand m² order, and also demonstrated good long-term reliability. Through numerical simulations of this system, the non-dimensional correlation for many system parameters was derived, which shows possibility of simplification of evaluation process for system performance.

The present paper deals with the multi-modal vibration control of truss structures based on the independent modal space control. A modal sensor for identifying specific vibration modes is constructed by one accelerometer and band-pass filters, where the sensor is optimally placed based on the minimization criterion of observation spillover due to unmeasured vibration modes. Besides, one stacked piezoelectric actuator is also optimally placed to maximize the induced modal control forces for controlled vibration modes. The proposed optimal placement method of a sensor/actuator using satisficing trade-off method is examined through the numerical examples.

Liquid distribution machine has an important role in industry, which pressure drop as well as flow distribution be simultaneously improved. In this paper, a multi-objective design optimization for minimizing the standard deviation of liquid flow and the pressure drop is performed using numerical simulation. Numerical simulation in computational fluid dynamics (CFD) is so intensive that sequential approximate optimization using radial basis function is adopted for the design optimization with a small number of simulations. Through the numerical result, the pareto-frontier between the standard deviation of liquid flow and the pressure drop is clarified. In addition, it is confirmed that the angle of perforated plate reduces vortex which have a significant influence on the flow maldistribution.

Sheet metal forming is one of the important manufacturing technologies to produce metal parts. Tearing and wrinkling are major defects in sheet metal forming, and they should strongly be prevented for the high product quality. A constant blank holder force (BHF) is conventionally used for successful forming, but variable blank holder force (VBHF) that the BHF varies during the forming process has attracted attention and has been recognized as one of the advanced manufacturing technologies. However, it is difficult to determine the VBHF trajectory for successful sheet forming without defects. In other words, a trial-and-error method is so widely used to determine the VBHF trajectory. In addition, blank shape also affects the product quality. In this paper, blank shape and sloped VBHF trajectory are optimized simultaneously. To determine them, a multi-objective optimization is performed. Numerical simulation in sheet metal forming is so intensive that sequential approximate optimization is adopted to determine them, and the pareto-frontier is then identified. An automotive part provided from NUMISHEET2011 (BM3) is selected for the application of the proposed approach. The optimal blank shape and the optimal sloped VBHF trajectory is determined through the numerical simulation. It is found from the numerical result that the optimal blank shape minimizing earing without tearing and wrinkling can be obtained.

Biped robots are expected to be able to operate in the human living environment. It is necessary to generate walking motions adapted to various grounds. The biped walking motion is determined by the position and timing of the landing point and ensuring stability. Optimal walking motions based on minimizing energy consumption and walking time under stability are derived based on optimization by genetic algorithms. The purpose of this study is to develop a strategy for generating walking gait for biped robots in various environments, such as stairs and obstacles. Gait generation for stair walking is performed by applying the algorithm for generating straight walking by the optimization method using the genetic algorithm. The effectiveness of the proposed method is shown from the obtained generation results.

The number of solar arrays and the annual amount of the received light in the mega solar plant are maximized by the optimum layout design of the solar arrays and the site shape. The layout design parameters of solar arrays consist of tilted angles, azimuth angles, intervals, and center coordinates of the entire solar arrays. The configuration of arrays is one of the critical parameters in the photovoltaic system. In the author’s previous studies, the placement optimization of the solar arrays by the conjugate gradient method at the multiply-connected domain is examined. The layout of the solar arrays was optimized by the proposed method to increase the annual amount of the received light. In this study, we show some optimization results with different initial values in the iterative calculation and consider the initial value dependence of the obtained solution.

In this study, a two-step optimization method that combines the continuous optimization method and the combinatorial optimization method is proposed for solar arrays placement optimization. The optimum solution of array’s placement obtained by the genetic algorithm is used to the conjugate gradient method as the initial solution. This two-step optimization can be expected to make the quasi-optimal solution a global optimal solution in a mixed variable optimization problem. From the results of several example analyses, it was found that the proposed two-step optimization method could be used to increase the total amount of received light of the photovoltaic power plant.

Cold forging is a typical manufacturing technology to produce various mechanical components with high productivity. Various process parameters such as punch velocity and forging loads are adjusted for successful forging. In this paper, a backward extrusion of aluminum alloy using the spring devices is considered. The target product handled in this paper has earing, around which the risk of crack is high with inappropriate process parameters. Therefore, it is important to determine optimal process parameters to minimize the risk of crack. In addition, in the cold forging, it is important to form the product with minimum forging load. In this paper, a multi-objective process parameters optimization minimizing the risk of crack and the forging energy is performed using numerical simulation. Numerical simulation in the forging is so intensive that sequential approximate optimization using radial basis function is adopted to determine the optimal process parameters with a small number of simulations. Through the numerical result, the pareto-frontier between the risk of crack and the forging energy is clarified. In addition, it is found that the smooth flow lines along the product shape can be obtained. Based on the numerical result, the experiment is also carried out to validate the proposed approach.

A risk assessment is essential, when designing new machines or modifying existing machines, to build adequate design strategy for accident prevention related to the use of machines. However, it is not a process that can be achieved by mechanically implementing certain formulated procedures, actually, it is a sort of creative work that requires much experience and knowledge about all the risks associated with the machine from engineers involved in its design. Therefore, securing and developing personnel with relevant skills for the risk assessment are being recognized as a big burden, especially, on small and medium-sized manufactures which generally suffer from a shortage of human resource. In this paper, an essential aspect of “hazard identification” which is the most important step in any risk assessment and needs supports most for inexperienced designers are clarified. In the hazard identification, the designers are required to derive(imagine) possible accident scenarios based on their empirical knowledges and accumulated information. From preliminary considerations on application of product safety standards (so called as Type-C standards) which are dealing with significant hazards concerned in a certain type of machine to the risk assessment, a practical way to facilitate inexperienced designers identify the hazards in the machine design phase by utilizing basic and generic safety standards which are comprised of fundamental requirements relating to general safe design of machinery is proposed.

Omni-directional movers have no restrictions on movement in a plane. Taking advantage of this characteristic, some manufacturers have sold forklifts that can move in all directions. However, the operation method of these vehicles differs among manufacturers, and a general operation method has not yet been established. Therefore, the purpose of this study is to develop an evaluation method for passenger omni-directional wheelchair that can compare and examine various possible operation methods in order to find a better operation method. First, the evaluation method of operability was examined. The evaluation criteria for operability vary depending on the purpose and use of the omni-directional mover. Even if we focus only on the operation elements, it is necessary to consider various things such as installation position, angle, and the relationship between input and output. Therefore, in this study, we examined a method to evaluate multiple operation methods for the operation of a wheelchair type omni-directional mover. Next, we constructed a common platform for the evaluation of operability. This is a four-wheel-drive, four-wheel-steering vehicle that can be ridden. The microcomputer calculates the angular velocity of the tires and the steering angle from the command values from the control elements and performs feedback control. We are currently working on the control program, and we will evaluate the operation of the omni-directional moving vehicle with a 3-axis joystick in the future. From the above, this study provides a basis for investigating the operation method of omni-directional mover.

Even in 2019, the number of occupational accidents that occur in Japan is about 850, and the number of casualties is about 125,000, which is not a small number. In addition, there are reports that the frequency of occupational accidents is increasing as the size of business establishments becomes smaller. The Ministry of Health, Labor and Welfare is promoting the introduction of risk assessment as a measure to reduce the number of victims of occupational accidents. However, it has not been fully spread in small and medium-sized enterprises due to lack of human resources. In this study, we propose a method of contrasting machine photographs and illustrations based on the fact that the machine is compared with the list of hazards. In addition, although it is necessary to present the accidents as comprehensively as possible when creating the illustrations used in the risk assessment, if the number of illustrations is excessively large, the amount of work increases and it becomes difficult to carry out. In addition, it is desirable that the method of creating an illustration be as simple and easy to understand as possible. From these things, we have summarized the procedure that anyone can create an illustration in an easy-to-understand manner.

Caluculus crushing factor of f-TUL which is one of the treatments for ureteral stone disease is thermal effect of pulsed laser and collapse impact of laser-induced bubbles. These factors play an important role in crushing calculus, but can cause mechanical and thermal damage to surrounding tissues. In order to improve the safety of f-TUL, we observed the behavior of bubbles when pulse conditions and laser energy were changed, and measured temperature around bubbles using a thermocouple. As a results, in a single pulse the behavior changes depending on length of pulse duration and temperature around long pulse bubble is higher than that in short pulse. In the case of double pulse, the behavior is different from that of a bubble formed by a single pulse, and ambient temperature of bubble tends to be low.

Acoustic metamaterials are artificial materials whose acoustic properties, such as the medium density and volume elasticity, are adjusted in order to reproduce a peculiar wave phenomenon. The materials are featured by a miniature unit structure whose size is usually smaller than the wavelength. In the present study, we developed a sound reflection device comprising an acoustic metamaterial used to reflect the incoming acoustic waves back to an arbitrary direction in space. The metamaterial structure is composed of a series of acoustic ducts where each set of neighboring paths has a constant relative length. Numerical simulations revealed that the incident sound wave reflected for the target reflection angle as large as 60 degrees. In addition, the sound field measurements showed that reflection of sound whose frequency ranged between 500 Hz to 2kHz could be possible.

To develop domestically produced stringed instruments, the sound and vibration characteristics of the top plate of the ukulele made from the compressed cedar wood in Japan were experimentally investigated and compared with those produced from rosewood. We measured the density of compressed cedar wood plates and found that the density was close to that of the rosewood plate when the compression rate was over 70 %. Then, the vibrational accelerations of the top plate were measured for modal analysis when each string was played. The results showed that the vibrational modes were similar to each other for the fundamental frequency of each string. However, it was found that they were quite different at harmonic frequencies.

Tri-star wheel is characterized by being able to climb a stair in addition to the stability during translation. In this paper, we analyze the dynamic behavior especially focusing on the force acting on the ground wheel when climbing a stair in order to design an optimal controller, which achieves stable climbing. Based on this analysis, we propose a method to determine the design parameters of the optimal controller together with SRL (symmetric root locus) method.

A broad-band frequency tunable dynamic vibration absorber was designed and fabricated based on the primary design principle of a mass damper. A magneto-rheological elastomer (MRE) that can change the relative stiffness when an external magnetic field is applied was used to control the natural frequency of the movable mass of the absorber. A coil to generate the magnetic field was also used as a movable mass to decrease the total weight and to create a constant closed loop of the magnetic force. For the purpose of further improving of the absorber to reduce the vibration effectively, the absorber that can reduce the vibration both in the lateral and vertical direction of the vibrating objective was studied. As a result of changing the shape of MRE used in the previous absorber from a circular shape one to an elliptical shape one, the vibration in both the lateral and vertical direction of the vibrating objective could be reduced with applying the optimum current to the coil.

The burden of vibration on passengers during vehicle operation is significant, and prolonged exposure can cause vibration problems such as back pain. However, it is difficult for passive dampers to provide good insulation against steady and transient inputs. In this study, we develop a semiactive vibration control method that insulates the vibration by sealing magnetorheological fluid in the damper mounted on the seat suspension and adaptively changing the viscosity according to the magnitude of the magnetic field. The viscosity switching law is based on the skyhook theory, which discriminates the appropriate magnitude of the damping force from the combination of input signals. First, the vibration damping performance is compared using two vibration methods, steady-state excitation and shock input, in a passive state. The effectiveness of the variable viscous damper is then evaluated by simulating a semiactive condition. The results show that the system exhibits the damping characteristics of a 1-DOF vibration system, reducing the vibration by up to 52% at the peak of resonance.

In recent years, various vibration damping methods have been studied to solve vibration problems caused by the sophistication of mechanical technology, and research on vibration damping devices using smart materials is underway. The magnetorheological elastomer (MRE) is known to belong to a class of smart materials whose viscoelastic properties can be varied by an externally applied magnetic field. By using this property, development of semi-active vibration control equipment that enables effective vibration control over a wide range of frequency is being studied. In this study, the characteristics of molded MRE which change stiffness applied magnetic field were evaluated by the dynamic test. Additionally, we proposed a numerical model that expresses elastic behaviors of the MRE and predicted spring constant of MRE incorporated the vibration isolator．Furthermore, we actually developed variable stiffness control vibration isolator incorporated the MRE, and the performance was evaluated by the force responses to forced vibration. Experimental investigations show that the developed vibration isolator has excellent stiffness changing characteristics as compared to the conventional isolator and proposed numerical model can express the change in the stiffness of vibration isolator.

Articulated robots, as represented by industrial robots, maintain high stiffness and control the end effector position. These robots are equipped with fences to separate the workspace from the human body to ensure safety. On the other hand, since it is a link mechanism in collaborative robots that require softness, there is a problem that the direction of force and displacement does not match. As an approach to this problem, the authors have focused on the muscle function of bi-articular muscles in vertebrate animal. Implement a bi-articular drive actuator that simulates the bi-articular muscles. By controlling the stiffness of the actuator, it is expected that a robot with characteristics closer to those of a human can be realized. In this case, the stiffness is controlled by combining force control, which can control the force more directly, with position control. Authors have investigated the change of the stiffness ellipsoid at the center of gravity by changing the stiffness of a bi-articular drive actuator. In the present study, the control method in the direction of the axis of the ellipsoid is investigated in the direction as a reverse problem. It was found that the stiffness of the actuator greatly affected the adjustable range of the axis of the stiffness ellipsoid at the trunk of the robot with the bi-articular drive actuator.

The present paper deals with identification of location and history of impact forces which act on aluminum alloy plates. A transfer matrix to relate an impact force to sensor responses is determined based on high-velocity impact tests. The location and history of applied force are evaluated as solution of error minimization problem by using the transfer matrix and measured strain responses. The identification of applied force history can be achieved by solving an inverse problem where a penalty on the force history is imposed in this paper. The validity of the present identification method is examined through the numerical examples.