With rapid advances in a technology of industry, rotating machinery tend to be more larger in size and capacity, high speed, and high performance. These advances have happened to occur many vibration troubles on rotating machinery. Especially in recent year, the radial clearance between rotating shaft and casing come to smaller to get higher performance of the machines. As a result, sever vibration occur on the rotating shaft accidentally, when the contact between shaft and casing occurred. Such problems dose not yet solved enough due to the complexity of the rubbing-contact and the collision mechanisms. This paper deals with the vibration behavior of the rotating shaft due to contact with casing, theoretically and experimentally.

View full abstract

The objective of the H₂ optimization of the dynamic vibration absorbers (DVAs) is to minimize the vibration energy transmitted to the system from the source of excitation. In this optimization criterion, the squared area (called H₂-norm) under the frequency response curve of the system is minimized. If the system is subjected to random excitation instead of sinusoidal one, then the H₂ optimization is probably desirable than the popular H_∞ optimization. The H₂ optimization is a classical optimization problem of DVAs, and has been already solved for a special case when the primary system has no damping. However, for the general case where the damping is present in the primary system, the H₂ optimization problem is not solved by algebraic approach until today. This paper proposes a closed-form exact solution for the H₂ optimization of DVAs attached to the damped primary systems.

View full abstract

In recent years, research and development of various dampers, which reduce the vibration by earthquakes and wind of the structures, have been prograssed. In this study, simple structural damper was suggested, which could aims at the development of the large-capacity damper. This damper uses unvulcanized rubber as working fluid, and obtains damping force by making plastic flow of rubber material in a vessel. In this paper, load tests were carried out to small model damper, and design formula was drawn. The design formula was theoretically obtained from the equation of the Navier-stokes. It has been applied by using the assumption of parameter of viscosity coefficient for the formula of the theoretical flow, in the flow of the unvulcanized rubber. By comparing the experimental results with design formula, it was proven that both agreed very well. Furthermore dynamic load tests were carried out for 98 kN damper which was designed by formula. As the results, the load-displacement characteristic of this damper was the rectangle shape that had the roundness, and it was confirmed that there is velocity dependence of the 0.2 nd power of the velocity on the damping force.

View full abstract

A self-sensing actuator using piezoelectric two films with different thickness and area, which are closely installed on one surface of general curved structures and are treated as two capacitors in the active RC bridge circuit, is proposed from the view-point of simplification of hardware aspects of devices toward the realization of smart structures. It is first implied that this device is effective in the following points, i.e., 1) compensation of ME noises, 2) ability of obtaining high gain feedback and enough control power and 3) compensation of temprature for pyroelectric effect. Then, vibration control effects are estimated by theoretical analyses of free vibration response and harmonic steady -state response of a cantilever which is an example of fundamental flexible structures, and the guideline for constructing control circuit is shown. Finally, the validity of proposed self-sensing actuator scheme is verified by conducting the experiment of free vibration response of a cantilever.

View full abstract

In the authors' 1st report, a smart and simplified self-sensing actuator technique using piezoelectric films with different thickness is proposed. In this paper, application of the proposed method to the vibration control of curved structures is investigated. A flexible circular ring is treated as an example of curved structures and piezoelectric films with different thickness are bonded on one surface of the ring. The two films are treated as two capacitors in the active RC bridge circuit, and these are totally used as a self-sensing actuator. At first, fundamental equations of the circular ring with proposed self-sensing actuator are derived and vibration control effects are estimated by numerical analysis. Then, vibration control experiment is performed using an aluminum circular ring, and it is shown that the lowest vibration mode is efficiently controlled.

View full abstract

There are three basic finite element formulations which are used in the multibody dynamics of flexible beams. These are the floating frame of reference approach, the incremental finite element approach and the large rotation vector approach. Recently, the absolute nodal coordinate formulation was proposed by A. A. Shabana et al. In this formulation, the mass matrix becomes constant, whereas the stiffness matrix becomes nonlinear function of time, even in case of linear elastic problems. In this paper, a new formulation to calculate the elastic forces is proposed. This formulation is based on the assumption that the deformations within each element remain very small. So, the expression of the resulting elastic force is simple, and this formulation is efficient for large rotation and medium deformation problems. Numerical examples are demonstrated for this formulation by using planar static buckling problems and flexible pendulum problems.

View full abstract

Inflatable structures have attracted considerable attention as space structures. In many space experiments, folds occurred during deployments of inflatable structures. They had undesirable influences on the body of space structures. This paper is intended as an investigation of deploying behaviors under microgravity of inflatable tubes that have a plastic fold on the center and a mass block on the tip. During their deployments, spring-back phenomena were happened in some experimental conditions. In order to examine these spring-back phenomena, a numerical simulation was conducted using the equation of motion under a consideration of restorable moments with the plastic folds. As a result, simulations corresponded well with experiments. Consequently, a following conclusion was obtained: Spring-back phenomena were caused by restorable moments of the plastic folds.

View full abstract

The dynamic behavior of the flexible beam, which is pulled into the slit of the elastic wall, is discussed with Multibody Dynamics formulation and experiments. This behavior is called "Spaghetti Problem". The gap size of the slit is thought to affect the lateral deformation of the beam. Dynamic behavior of the beam is simulated numerically and examined the accuracy of the presented formulation by the gap size and the pulling velocity of the beam as parameters. It is clarified that the gap size and the pulling velocity influence the increase of the lateral vibration near the inlet of the slit.

View full abstract

In this paper, the authors propose a new method for identifying a set of spatial matrices of a test structure from its modal parameters experimentally estimated in advance. The algorithm of the method is based on the mathematical relationship between a set of spatial matrices and frequency response functions (FRFs in brief). An appropriate set of spatial matrices can be determined without mathematical iterations. The algorithm is explained. The basic validity of the method is demonstrated with an actual frame structure. The FRFs of the specimen under single input and multiple output condition are obtained by hammering testing. Using the FRFs, the method identifies a set of spatial matrices that can predict FRFs between any two measurement points with practically acceptable accuracy.

View full abstract

Electromagnetic acoustic transducers (EMATs) can generate and detect ultrasonic waves in a conductive specimen by electromagnetic coupling without any contact with a specimen. Moreover, theoretical modeling and formulation of the process based on elastodynamics and electromagnetics can be obtained. This feature makes it possible to analyze the inspection process in detail theoretically or numerically. In this research, effects of a flaw on the propagation of ultrasonic waves and on receiver signals of EMAT testing were evaluated by using numerical analysis. Predicted receiver signals agree well with the experimental ones, which validates our analysis. The numerical result of the wave propagation explains the effects of the flaw, i. e. interruption, diffraction and multiple reflection. Among the three effects, the peak of receiver signals due to multiple reflection is well influenced by the parameters of the flaw. These results can be useful to establish a method of quantitative flaw identification by EMAT testing.

View full abstract

The practical active exhaust muffler using ANC system was studied for reducing 'the harmonics of basic frequency which are the main components of exhaust noise generated by a medium size diesel engine truck during the period of acceleration. The muffler structure which reduces the thermal affect to ANC speaker by exhaust gas, was designed, and the time base Synchronized Filtered-X method with a modified variable stepsize algorithm was proposed as the control strategy in time-varying environment. The effectiveness are verified after applying the ANC system to the exhaust noise control of the truck on the condition of accelerated running.

View full abstract

We developed an on-line experimental system for conducting hybrid experiments in real time. This. system combines a computer for simulating vibration and generating a control signal with an actuator for vibrating a structure according to the control signal. And the system compensates for actuator delay, so that experiments can be carried out in real time. In this report, we discuss the stability ciriterion with respect to the mass of the structure under excitation in conducting real-time hybrid experiments, and propose a new method for compensating actuator delay so the experiments are more stable. This method increases the stability criterion (the allowable ratio of the mass of the structure under excitation to that of the mumerical model) by about three times compared with that of the conventional method.

View full abstract

The optimum seismic shutdown level for elevators, which will reduce the number of shutdowns occurring without seismic damage, is estimated. This estimation uses maintenance record data of elevators for obtaining seismic-shutdown-ratio curves and damage-occurrence criterion, which are then used to determine the shutdown-level margin. It was thus revealed that the newly revised shutdown level (150 cm/s²) for rope elevators corresponds to a safety factor of 1.4 and the shutdown level for hydraulic elevators can be raised to 75 cm/s², which corresponds to the safety factor comparable to rope elevators. It is concluded that seventy percent of shutdowns can be eliminated by adopting these new shutdown levels.

View full abstract

This paper deals with an experimental study of propulsion force characteristics of traveling-wave motion of a flexible plate modeled on the flexible caudal fin of fish. The flexible plate is set at the trailing edge of an oscillating wing which are heaving and pitching around the leading edge of the oscillating wing, and the traveling-wave motion of the flexible plate is excited by the combination motion of the heaving and pitching motion of the wing. In the experiment, the propulsion force and side force in stationary water is examined. As the result of the experiment, the effect of the traveling -wave motion of the flexible plate on the propulsion force characteristics is clarified with changing the length and thickness of the flexible plate, and the motion pattern of the oscillating wing.

View full abstract

This paper presents an active control for stabilization of a cantilevered pipe conveying fluid using optimal output feedback controls with Piezoelectric actuators. The output feedback controls are more practical technique than the state feedback controls, but, on the other hand, the control performance is restricted within some limits. Therefore, in this paper, various properties of this control system are clarified by numerical simulation. By the output feedback controls, the pipe conveying fluid is stabilized effectively same as the state feedback. The location of the actuators is very important factor to construct an output feedback control system. Because the control system has no effective feedback gain for stabilization on the location and even if the gain exist, satisfactory stabilizing effects are not obtained. When the controlled system of the pipe conveying fluid has strong unstability, the system can not be stabilized by using the output feedback controls.

View full abstract

This paper deals with total synthesis of structure and controller under pole (finite dynamic mode) placement constraints on the closed-loop system in a descriptor form. First, closed-loop system is described in a descriptor form. Secondly, a necessary and sufficient condition for pole placement of descriptor system is given. The problem is reduced to bilinear matrix inequality (BMI) problem. Finally, an example is shown with its iterative algorithm.

View full abstract

In this paper, a method is presented to determine the control forces using several output values which are predicted by a short-term prediction method of time series based on chaos theory assuming that the disturbances of the system are not measurable. The concept of the forward horizon is important for such predictions. The forward horizon is defined for the time series to be predicted and represents the number of values near future which are used for determination of control forces. A method is also proposed to calculate the forward horizon for output time series. The control forces are consist of the predictive control part and the feedback control part by linear feedback theory. The predictive control method proposed in this paper is applied to a numerical example in a rotating disk simply supported by two rigid bearings. The effectiveness of the proposed method is shown by the control results.

View full abstract

The method of input control signal determination for rapid positioning is proposed. A fine motion stage has been developed for an inspection system of TAB (Tape Automated Bonding) type lead or other microscopic observation systems. The stage consists of flexure hinges driven by piezoelectric actuators, however, it lacks in motion damping. In order to obtain the fast settling motion without aids of damping elements, a numerical simulation in consideration of nonlinear factors such as discrete DAC signal, PZT hysteresis, amplifier delay and non-linear spring, is developed. The input control signals are optimized by a gradient method. To avoid the vibrating solutions which may result in divergence, the rank of a gradient matrix of objective function is reduced, and then the general inverse of Moore Penrose is obtained. It is found by several experiments that the fast settling motions are realized with the optimized input signals.

View full abstract

The idle speed reduction is one of the important solutions for fuel economy improvement. And to achieve it, it is required to improve the performance of idle speed control to prevent from engine stall. In the mass production engines, PID is mainly used for the idle speed control because of easiness of design. Recently there are many studies applying the linear control theory like LQG and H infinity to improve the performance. However there are few studies applying the nonlinear control theory in spite of the idle speed control system has non linearity like torque and friction characteristic. So we have pursued to develop the algorithm the performance of which is superior to PID and LQG by applying the sliding mode control (SMC) representative in the nonlinear control theory. In this study, at first we built the low order model of the system by using the design specifications and simple experimental results, and then we designed three controllers applying PID, LQG and SMC. And consequently we could achieve the above aim by adopting the acceleration reaching law to nonlinear input in SMC instead of the conventional constant reaching law.

View full abstract

A stabilization strategy of rotary cranes has been proposed in this paper. Since the linearized system of the rotary crane becomes uncontrollable for radial motion, nonlinear control is required. An easy algorithm can be found for stabilizing the load at the specified position by moving the boom at each half periods of the load swing. The effectiveness of the proposed method has been shown by simulations and experiments.

View full abstract

This paper describes an algorithm for constructing generalized T-S fuzzy models from nonlinear models. We frst present a generalized form of Takagl-Sugeno fuzzy systems. The generalized form has a decomposed structu.re for each element of A^^^(SUB)p and B^^^(SUB)p matrices in consequent parts. Next, an algorithm for constructing generalized T-S fuzzy model from nonlinear models is proposed. A construction example for a typical mechanical system is illustrated. The results show the utility of the proposed algorithm.

View full abstract

No matter whether the power source will be the electric batteries, or the IC engine/generator, or the fuel cell, etc., the power device for driving directly the tire/wheel of automobiles seems to shift from conventional IC engines to electric motors. The major characteristic difference between IC engines and electric motors, especially vector-controlled motors is rapidness of their torque response. That means the necessity of the traction control device. In this study, TRC which made the most of the superior feature of vector-controlled motors was successfully proposed.

View full abstract

Refrigerated super-showcases are used for displaying and preserving food products at places such as supermarkets It is important that trouble occurring in showcases is anticipated in advance. However, there exist difficulties due to the existence of numerous types of units, inconsistent characteristics, and too few sensors, all of which make it hard to develop a standardized method of evaluation for determining if a showcase is operating correctly. In this paper, we propose a new method of occurrence-forecast of trouble for showcases by using criteria adapted to environmental conditions. This method is based on the characteristics of showcases that their operating state is influenced by environmental conditions. We have evaluated this method from field data of a supermarket. The result leads us to convince that this method can be put to practical use.

View full abstract

Disk drives are required highly accurate positioning performance against disturbance friction force and vibration. In this paper, a novel configuration of realizing a two-degree-of-freedom (2DOF) track following controller with disturbance observer is proposed for large capacity FDDs with backwards compatibility. The controller is designed using two position sensors, one of which is used to handle low density disks. Furthermore, a new open loop design method is applied to choice the atable parameter against unmodeled dynamics. The validity of the proposed scheme has been confirmed by experiments.

View full abstract

Many kinds of actuators are used in robots or mechatronics systems. The torque/inertia ratio is one of the indexes that show the characteristics of the actuator. Since the actuator that has large torque/inertia ratio can respond very fast, it is suitable for haptic interface. In this study, rapid-response miniature ER actuators are proposed, and modeling and control of the wire drive system using miniature ER actuators are discussed. The ER fluids are kinds of functional fluids. The ER actuator can realize large torque/inertia ratio and rapid response. Firstly, multiple-disk-type miniature ER actuators are developed, and its static and dynamic characteristics are investigated. Next, a wire drive system is constructed by using miniature ER actuators and the transfer function of the system is derived. Finally we design the PD feedback position control system. Frequency response and time response experiments are conducted. It is verified that the feedback control system can be designed by using the derived model.

View full abstract

In this paper, a teaching system of force control is proposed for a polishing robot using a game joystick. The teaching process is as follows: first, a zigzag path considered according to both sizes of each work and polishing tool is prepared; next, the polishing robot, in which an impedance model following force control method is incorporated, profiles the surface of the work using the zigzag path. The operator has only to control the orientation of the polishing tool using a game joystick so that the tool and work can be in contact each other, keeping the desired relation of position and orientation. Since the impedance model following force controller keeps the contact force to be a desired value, the operator has to give no attention to a sudden over-load or non-contact state. The desired trajectory is automatically obtained as the data including both continuous information of the position and orientation along the zigzag path on the object's surface. After all, the robot can achieve the polishing task without any assists of the operator by referring the acquired trajectory.

View full abstract

This study investigates the possibility whether protozoa can be treated as a living micro manipulator/actuator or not. Motion control of protozoa was made by using the negative galvanotaxis. In the previous study, it was succeeded to control the paramecium along figure '8'. Its controllability, however, has problems about speed control, rapid turn and position accuracy. Therefore, this paper first investigates the application of pulse width modulation method for the control of paramecium's swimming speed. However, the results show that the application of the pulse electric field causes the strange reaction such as rotation, zigzag swimming, etc. Next, rapid stopping phenomenon of paramecium's swimming by the sudden stop of electrical field is investigated to improve the rapid turning ability of paramecium's swimming. To adopt this method to the automatic motion control program, paramecium can be controlled along any shaped guide route. Paramecium's generating force is also measured by pushing the small object by controlled paramecium. It is estimated about 2.7×10^-8 N. For an example of the micro mechanical application, the micro impeller (φ 0.5 mm) is rotated by paramecium. These results show that micro mechano-bio-fusion system can be constructed by using protozoa.

View full abstract

This paper describes an alternative method for the assessment of locomotion, based on the combination of the advanced wearable instruments and a simple kinematic model. The advantage of the method is that it does not require special laboratory equipments and can be used for field studies with a completely body-mounted recording system. Multiaxis accelerometers and gyroscopes were attached to each segment of lower extremities. The process included detection of temporal parameters of locomotion, calculation of joint angles, and estimation of the ground reaction force in the sagittal plane. In addition, inter segmental joint moments and powers were calculated by inverse dynamical analysis. Finally we obtained an index of energy expenditure. Validation of the method was evaluated in comparison with a conventional gait analysis system such as video-based motion analysis system and force plate. Initial results show that it is possible to use this method for the long-term assessment of locomotion during normal level walking.

View full abstract

In this paper, we use the radial basis function network in order to approximate the fitness function of the genetic algorithms and try to obtain the approximate optimum results within the relatively small number of function call. The radial basis function networks (RBF) is a kind of neural network that is composed by the number of radial basis function in Gaussian distribution. RBF has learning system that is composed by additional learning of a basis function and a new data and forgetting of a basis function and an undesirable data. Thus the key issues in RBF are to give new data and to place basis function. So that if we can give these values appropriately, we can carry out approximate optimization even in the case that the optimum solutions are outside the range of the initial settings. Together with the adaptive range genetic algorithms that are proposed to treat mixed variable optimization, we will propose the way to give a new data and basis function. In this study, we have shown the effectiveness of the proposed method through simple numerical examples in unconstrained optimum design case.

View full abstract

In this paper, we use the radial basis function network in order to approximate the fitness function of the genetic algorithms and try to obtain the approximate optimum results within the relatively small number of function call. In the first report, we have shown the effectiveness of the proposed method in unconstrained optimization. In the constrained optimization, we have to take care of constraints. In genetic algorithms, we usually treat them by including into fitness function with penalty function. However, when we estimate fitness function by using penalty function, giving good penalty becomes very difficult. Moreover, when we give a large penalty to them, approximation will be influenced by those penalities and it becomes almost impossible to obtain real optimum solutions. In order to use the benefits of the method in unconstrained problems, we ignore data those which are not included in feasible region and assume to have unconstrainted optimum problem. From famous 25 bar truss problem, we will show the effectiveness of the method.

View full abstract

This paper describes a new approach for competitive self-growing neural network and its application to fault diagnosis of electric parts using image analysis. Conventional competitive network such as RCE network proposed by Cooper et. al. has a greenhand for its decision making process. Thus, we introduce the confidential voting process in order to avoid the ambiguous decision making in the network. Reliability of electric product is evaluated with some average properties such as the Mean Time To Failure. However, if we can find an efficient method for fault diagnosis of individual electric product, the more efficient maintenance and quality control can be performed. The basic concept of this study is that the performance degradation of carbon film resistor can be efficiently estimated from their images using the proposed method. We first discuss some essential issues to be considered in reliability problems. Experimental results by using the proposed competitive network with confidential voting are also described. It is shown that the network gives a good performance.

View full abstract

Generally, a carbide hob is excellent in durability, cutting with high speed and high accuracy, but it occurres chipping easily. Therefore it is difficult to use under stable conditions. Kurume N.C.T. succeeded in practical application of the carbide hob for the first time in the world during 1970 year. It was used by many production plants, but it was not used by automobile plants under severe conditions. Recently, there has been a growing demand to cut gears without cutting oil for a good environment. To achieve this purpose in a mass-production line for the automobile plant, the authors have successfully developed dry cutting system with the carbide hob by incorporating a highly rigid CNC hobbing machine. This source of success has been accomplished by establishment of the selection system of the hob material is investigated. And after the hob is produced as the experiment, cutting is performed using it on the hobbing machine truly.

View full abstract

A serial printer using a synchronous belt in the print-head carriage system sometimes generates a vertical striped pattern in the printing image. This is known as jitter and caused by vibration of the print-head carriage system. This paper describes the method to reduce the jitter due to the meshing vibration of a synchronous belt under low speed printing (dye-sublimation transfer printing). Firstly, the vibration of carriage system is analyzed by using a single-degree-of-freedom model and the vibration characteristic of a thermal serial printer is investigated experimentally. Then, experiments for valuating transmission error of synchronous belts are carried out. It is confirmed that jitter due to the meshing vibration of a synchronous belt is remarkably reduced by changing the belt pitch from 1.411 mm to 1 mm and using a helical synchronous belt.

View full abstract

In front wheel drive cars, a fixed type CV-Joints is located at the wheel side, and a plunging type CV-Joints is located at the gearbox differential side ; both are connected by a interconnecting shaft. These are most popular applications of CV-joints. It is important for their design to analyze the internal forces of CV-Joints and the support bearing forces and moments. But in analysis of CV-Joint, only one CV-Joint is took up as the object up to now. For example, Kimata analyzes the CV-Joint internal forces considering all components' displacements and Hertzian deformations. But, it is inadequate in consideration of CV-Joints' mutual interactions on half-shafts application. In this paper, developping the Kimata's analysis, the system consisting of the interconnecting shaft, two CV-Joints with it's both end, and the support bearings is analyzed based on statics, then 3n^o+3nⁱ+32 (n^o: ball number of BJ, nⁱ: ball number of DOJ) simultaneous nonlinear equations are obtained. The equations can be solved numerically. From the solution, the contact forces acting between the joint's members, the induced forces and moments from CV-Joints, and the bearing forces and moments are obtained.

View full abstract

Taking into account the surface dilatational viscosity, influences of development of negative pressure including tensile stress on the static characteristics are studied for the oil film of journal bearing : When negative pressure develops in the oil film, the maximum oil film pressure remains almost unchanged. However, when negative pressure develops, the mean oil film pressure increases to some extent under light load, but decreases under heavy load, and the coefficient of friction decreases under light load, but increases under heavy load. When negative pressure develops, the semicircle-like orbit curve of the journal center under static load deforms perpendicularly to the load direction and towards the bearing outside. When negative pressure develops, the side flow rate can decrease by the amount of back flow caused by the negative pressure in the oil film. These results indicate that the state of operation of journal bearing can shift towards more dangerous range, when the negative pressure develops in the oil film.

View full abstract

This paper presents the result of fatigue tests carried out with an ATF and two types of traction oil. Since the performance of these oils as working fluid is preferred, the performance as a lubricant is inferior. The pitting life is evaluated by the value of D computed by the surface roughness and EHL film thickness. The high traction coefficient causes the tooth surface temperature rise by frictional heat, and then the oil film thickness and pitting life are decreased. To evaluate the performance of these oils as lubricants, the tooth surface temperature is measured in the pitting tests and the EHL film thickness is calculated with it for computing the value of D precisely. All results of fatigue test with three types of oils are examined together and it is found out that they are evaluated by the value of D only. The experimental formula to estimate the pitting life is obtained. This procedure is useful to design the surface gear strength of the automotive ATs and CVTs.

View full abstract

The torque variation during friction welding is related closely to the friction welding mechanism and the mechanical characteristics of the weld. Especially, the influence of initial torque on the accuracy of welded specimen is remarkably high. In this report, the effects of the initial torque characteristics on the friction welding of carbon steel are examined both theoretically and experimentally. The surface roughness of turned surfaces is modeled as triangular columns that are constructed in concentric configuration. Based on the relationship between the temperature change measurements during friction welding and the high temperature tensile strength of carbon steels, the contact width changes of the interrace and the torque changes are estimated. The experimental and theoretical results show good agreement.

View full abstract

As a basis to establish a method for evaluating the pure thermal shock resistance of brittle tools without applying cutting forces, a study was carried out about the starting point of the thermal crack by a method in which CO₂ pulse laser beam is irradiated on the rake face of a cemented carbide tool. The method is an original one recently proposed by the authors. Observations using a scanning acoustic microscope have demonstrated that thermal cracks not confirmed on the irradiation surface exist beneath the surface. The influence of the internal defects such as pore and so on, the fields of thermal stress was analyzed setting a spherical minute pore beneath the surface. The maximum main principal tensile stress, which occurs on the pore surface, increases rapidly after the start of the irradiation and maintains a higher level during the irradiation. The stress is markedly high beneath the irradiation surface. From these results, the thermal cracks on the rake face due to the irradiation may have originated from the internal defects beneath the irradiation surface.

View full abstract

This paper addresses a scheduling problem of a mold die production system in which parts can be assembled after all parts composing a die are fabricated. First, we analyze effects of dispatching rules, which relate to due date, slack time, operation time and modified process due date, on a part makespan and a ratio (the makespan/the maximum total operation time of part in a die), and present the optimum rule which minimizes the makespan. Next, we consider a method for estimating due dates based on the mean and the standard deviation of the ratio. Finally, using the above method we make a schedule, and analyze effects of rules and estimated due dates on the tardiness of die. The results show that rules are classified into three groups. The rules modifying process due dates perform well in the makespan, while the rule ignoring due dates performs worst. Furthermore, the coefficient of due date, which reduces a percentage of tardy dies to a desired value, can be approximately estimated by the proposed method. The rules modifying process due dates yield a smaller tardiness, and the rules using process due dates yield a smaller maximum tardiness.

View full abstract

The number of pallets circulating in a closed loop production system is an important factor which affects the production rate. If the number is large, pallets stagnate in the system. If the number is small, an idling state occurs frequently in many stages. In both cases the production rate drops. Therefore, it is necessary to control the number of in-process pallets in the system according to the states of pallet flow and stages in order to maximize the production rate. In this paper, we study the effect of pallet input control for a closed loop production system with constant operation cycle time and stage breakdown. First, we model a pallet flow in the system by a Markov model, and analyze the maximum production rate yielded in the system and the optimum policy for pallet input control by a Markov decision process. Next, we present the effectiveness of pallet input control comparing with the uncontrolled system. Finally, in order to investigate the effect of the number of pallets on the production rate, we analyze the production rate and the number of in-process pallets under the optimum policy using the reward function which consists of the production rate and the number of in-process pallets. The main results are as follows. (1) There is the optimum policy for pallet input control which yields the maximum production rate. (2) The pallet control is effective to increase the production rate and decrease the number of in-process pallets. (3) The decrease of the number of pallets monotonously reduces the production rate. However, if the buffer capacity is large, the reduction is very small near the maximum production rate.

View full abstract

In this paper, we address the problem Of cellular manufacturing system, which, in essence, consists of three main problems, cell formation and machine duplication and part subcontract. While a number of research have been conducted on the problem, most of them considered machine duplication and part subcontract separately. One paper considering cell formation, machine duplication and part subcontract is published, but the paper proposes two step method, so has a problem for possibility of local search. On the contrary this paper propose an integrated approach using Genetic Algorithm (GA) to solve the problems simultaneously on one step method. Our numerical experiments and results show that our method performs better compared to a conventional method which using two step method.

View full abstract

This paper proposes the synthesis method of the robotic arm and leg mechanisms suitable for the specified usage of robots. The adequate mechanism configurations will be decided through the use of the heuristic algorithms proposed by S. Lin, et al. The method will search the optimum mechanism-configuration by operating the matrix composed of the design variables on robotic mechanisms. This optimization method needs the function that can simultaneously evaluate the plural characteristics of robotic mechanisms. However, those characteristics are considerably different in unit and range. Thus the present study proposes new design data that show the cumulative frequency distributions on the static characteristics of robotic mechanisms. The proposed data permit the concurrent evaluation of different plural characteristics by their cumulative relative frequencies as a common criterion. Furthermore, this study describes that the importance of each mechanism characteristic to the usage of a robot is utilized as the limit condition for the synthesis of robotic mechanism. The present paper confirms that the proposed method will determine the robotic mechanisms suitable for their usage.

View full abstract

The Producibility Evaluation Method (PEM) was developed to comprehensively assess design quality for easier manufacturing of parts and products. It covers processing, assemly, and procurement. It's features are : (1)novel extended machining-producibility evaluation method that covers the difficulty involved in manufacturing dies for molding, die-casting, etc., (2)extended assemblability evaluation with a function for estimating part-level operation cost, (3)producibility evaluation that provides united evaluation of processability, assemblability, and procurement. This paper describes the derivation and theory of these methods.

View full abstract