Many real-world problems, including the design problem, involve multiple and often conflicting objectives. Genetic Algorithm (GA) is an effective method to solve such multi-objective optimization problems. The designer usually has some information and knowledge based on his/her experience. This paper describes a new method for multi objective design problems using GA. which can integrate designer's vague preferences into GA search. First, a multi objective optimization problem with constraints is expressed as a satisficing problem of constraints by introducing an aspiration level for each objective. Furthermore, the unsatisfying function is introduced in order to handle fuzziness involved in aspiration level and constraint, and the problem is formulated as a multi objective minimization problem of unsatisfaction ratings. In order to obtain a group of Pareto optimal solutions in which the designer is interested, a new strategy based on tournament selection is proposed. Finally, the proposed method is applied to a simple numerical example and a design problem of a four bar plane truss.

View full abstract

This paper presents a solution algorithm of nonlinear eigenvalue problem which occurs in an eigenvalue analysis of a structure with damping. The solution of nonlinear eigenvalue problems usually require operations of a complex matrix and complex vectors to generate Krylov subspace. The proposed algorithm is especially effective in terms of large scale analysis, because it does not use complex matrix nor complex vectors. Therefore, the number of operations and the size of memory used in the analysis is reduced. Furthermore, the accuracy of the solutions is confirmed to be satisfactory.

View full abstract

This paper studies a random vibration of chaotic mechanical system with stochastic excitation. To dates, studies of mechanical chaotic vibrations have mainly focused on their deterministic properties. However, stochastic properties of mechanical system are sometimes unavoidable especially in practical situations. We have already shown that stabilities and scaling properties of experimental chaotic behavior are well modeled by stochastic models rather than deterministic models. We also have demonstrated that errors in deterministic modeling are getting larger in non-chaotic region. These results seem to imply that stability reduces determinism of stochastic behavior. In this paper, we evaluate determinism of the target stochastic behavior as a function of a bifurcation parameter. For this purpose, we use the Wayland's test and chaotic synchronizations. The two methods give distinct results. Dependency of stability of target stochastic behavior on accuracy of their deterministic and stochastic descriptions is clearly evaluated by the chaotic synchronizations.

View full abstract

Nonlinear liquid motion in a partially filled annular cylindrical tank, in response to a pitching excitation, is investigated. The nonlinearity of the liquid surface oscillation is considered in the response analysis of the sloshing motion. Basic equations are derived by employing the variational principle. The nonlinear ordinary differential equations governing the liquid surface oscillation are then derived by applying Galerkin's method to the basic equations. The effects of the ratio of inner radius to outer one on liquid surface oscillation are discussed. The time histories of the liquid surface displacement are calculated to the harmonic pitching excitations. An experiment was conducted using a model tank. A good agreement was found between the theoretical and experimental results. It is shown that the nonlinear analysis is important for estimating the sloshing responses.

View full abstract

Recently identification techniques using neural networks for nonlinear vibratory systems attract interests of engineers. The identification techniques developed so far can determine the input-output relation of the objective vibratory system as a whole. They cannot determine the parameters of the system separately. In this report, we propose a new experimental identification technique which can determine the linear parameters as well as nonlinear terms of the system. The applicability of the technique is confirmed by numerical simulation and experiment.

View full abstract

This paper presents a design method of neural controllers for semi-active suspensions with nonlinear devices such as electrotheological or magnetotheological dampers. It is shown that the use of two neural networks corresponding to each signs of the relative velocity is effective to realize the desired controllers, i. e., semi active controllers inherently include discontinuous mappings due to the passivity constraint and it is generally very difficult to realize them with single neural network. A model-following type controller with these neural networks is proposed, and two learning methods, the feedforward learning and the recurrent learning, for the controller are investigated from a viewpoint of system identification theories : the equation error method and the output error method.

View full abstract

When an asymmetrical shaft is supported horizontally by single row deep groove ball bearings, a difference in shaft stiffnesses, that of support stiffnesses, and nonlinear spring characteristics coexist, and various kinds of nonlinear forced oscillations and nonlinear parametric oscillations occur. In this paper, internal resonance phenomena in the neighborhood of the secondary critical speed and the major critical speed are investigated. The following are clarified in both cases : (1) two peaks of a superharmonic resonance with both a forward and a backward components appear. (2) almost periodic motion due to Hopf bifurcation and one verified from a super combination resonance occur.

View full abstract

This paper presents an optimal design method regarding large scale structure subject to frequency response. It is difficult to directly apply an optimal design method to a large scale structure, because this model includes more than I million degrees of freedom. First, the dynamic mutual mean compliance is used as the measure of the acceleration at the observation grid and a sensitivity of the dynamic mutual mean compliance with respect to a scalar spring constant is formulated. A selection method of practical evaluation parts from a whole structure based on the measure of sensivities is proposed. Second, a new reduction method based on frequency response functions is presented. Third, an optimization problem, where the square of acceleration and additional spring constants are regarding as an objective function and design variables, respectively, is formulated. Finally, we demonstrate the effectiveness of the proposed method through the simple model.

View full abstract

This paper deals with prediction of structural and kinematic coupled vibration on internal combustion engine. Many researches have been conducted in prediction of engine vibration. Most of them are categorized into two groups according to their targets and their methods. One is prediction of structural vibration in relatively higher frequency. The other is prediction of kinematic vibration in very low frequency. Nowadays, it is getting more important to treat coupled vibration between structural and kinematic vibration in middle range frequency while the demand of light weight and low friction rises. In this paper, we develop an engine vibration analysis system that can analyze structural and kinematic coupled vibration comprehensively in wide range. The validity of the system is discussed comparing the calculation results to the experimental results.

View full abstract

Fast seeking in magnetic disk drives leads to residual vibration due to the mechanical resonance of the positioning system. We have therefore developed a two degree of freedom control algorithm that overcomes this problem. It has three main features. First, it generates a seeking trajectory that does not excite the primary resonance of the head actuator. Second, it calculates acceleration feed forward that assures the perfect tracking to the desired trajectory at position sampling (PTC : Perfect Tracking Control). Third, it modifies the target position trajectory, in order to reduce the modeling error, by taking into account digital control and a primary mechanical resonance. We confirmed by simulation and experiment that the control algorithm improves the track settling performance by reducing the vibration due to both the primary mechanical resonance of the head access mechanism and the slow transient response induced by tracking error in the target position trajectory. It was found that the one track seek time of a drive controlled by the algorithm is 15% faster than the conventional time.

View full abstract

Electromagnetic acoustic transducers (EMATs) can transmit and detect ultrasonic waves in a conductive specimen out of any contact with it. This process can be given theoretical modeling and formulation based on elastodynamics and electromagnetics. It suggests the possibility of quantitative nondestructive evaluation using EMATs. This research deals with a numerical method of flaw identification from a receiver signal obtained by EMATs. Experimental results of receiver signals agree well with numerical ones, which verified the mathematical model of the inspection process. Flaw identification is formulated as a problem of parameter optimization. To avoid being trapped in a local optimum, initial parameters were successfully evaluated from the height and the time period of peaks in the receiver signals. Flaw parameters were identified from receiver signals obtained from numerical simulations and experiments, which verified the method of flaw identification presented here.

View full abstract

Periodic input sometimes controls mechanical systems dynamically. We have investigated a pendulum system from a view point of such a dynamic control. In this paper, we present the motion control that stabilizes the pendulum to a desired limit cycle by a periodic input. In our method, the periodic input is added so that the energy of the pendulum may become the energy of the desired limit cycle, and is consisted of a periodic solution of van der Pol's equation which is inputted the angle of the pendulum. Experimental results support the effectiveness of the proposed method.

View full abstract

In recent years, linear motors are noticed as an excellent driving device of the straight pass transfer system. Advanced needs of transportation in linear motor is highly demanded in motor industries. This paper is to present motion control of a cylindrical linear induction motor (CLIM) by adjusting the frequency of V/f inverter. However, thrust characteristics of CLIM is governed by a complex non linear equation. To overcome this, first, the thrust characteristics is analyzed. And, the linearity of the thrust characteristic between thrust and slip frequency within the limited range is investigated. Then the reference acceleration range is decided based on the linearity range from this characteristics. Finally. H_x loop shaping control design method is applied and its usefulness has been demonstrated via experiments by comparing with conventional LQI control.

View full abstract

This paper proposes a simplified design method for sampled-data critical control systems with rate-limited exogenous inputs. Fast-discretization technique is used to obtain the input-output relationship with intersample behavior. From the input-output relationship, we derive an approximate condition for the critical specification. It is given as the inequality constraint on the step response, which can be calculated recursively. Controller parameters are determined by a numerical search. A design example is presented to show the validity of the proposed method.

View full abstract

This paper proposes a motion learning method for motion systems using basis function networks. Motion systems have unknown nonlinearities such as variation of inertia, Coriolis's force, nonlinear electromagnetic driving characteristics and gravity that are complicated to formulate. In this study, these nonlinearities are described by basis function networks. The updating rules of the weights in the network are derived by Popov's Hyper Stable Theory. However, there exist modeling errors and unmodeled forces which generate tracking errors. Therefore, H_∞control is introduced to attenuate the influence of modeling errors. This paper shows an analytical formulation of basis function networks for motion systems and effectiveness of the proposed motion control method by demonstrating an experiment of tracking desired trajectory in 2 types of 2-degree-of-freedom link motion system that have different motion equations.

View full abstract

When a system is parameter dependent and its trajectories of changeable parameters are affinely located in a convex polytope set, the state estimation of such a system cannot be precisely performed by using the existing linear observer theory. In dealing with this kind of state estimation problem, the polytopic observer is developed and the algorithm is formulated by LMIs in order to obtain the solutions of Riccati inequalities in solving the estimation gain matrix. Meanwhile, the stability of the proposed polytopic observer is proved and the convergence of the state estimation is guaranteed. The effectiveness of polytopic observer is testified by simulation comparison study.

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. We consider that the sliding mode control (SMC) representative in the nonlinear control theory is suitable for the idle speed control system. Because this system has non linearity like torque and friction characteristics. However it was said that it was difficult to get the high performance by SMC because of the chattering problem. In the previous paper, we described the following issues. The chattering problem comes from the large switching gain to attenuate the disturbance that does not satisfy the matching condition. However we could reduce the chattering of output (engine speed) by applying the acceleration reaching law and we could get the high performance superior to PID and LQG. In this paper, we describe the more effective way to reduce the chattering. That is, we applied the robust hyper plane that is frequency_shaped by H infinity control. And then we could succeed in reducing not only the chattering of output (engine speed) but also the chattering of control input while keeping the high performance.

View full abstract

An analytical method is proposed to evaluate the viscoelasticity of a biomaterial in water by the scanning probe microscope. The proposed method utilizes the dependence of amplitude and phase lag of cantilever vibration on the viscoelasticity when the tip on the cantilever cyclically penetrates into the cell. The cyclical penetrations are carried out in two ways; one is by excitation of the cantilever fixed end, and other by that of the table. The analysis takes the drag force of water due to the cantilever vibration into account. The stiffness and the viscosity of the cell are analytically related with the amplitude and the phase lag of the cantilever vibration. The results shows that the relations among the amplitude, the phase lag, stiffness and viscosity vary significantly depending on the excitation frequencies of the cantilever fixed end and the table.

View full abstract

A new optical system for measuring motion errors such as the straightness of a slide table has been developed. The optical system mainly consists of three components : (i) The He-Ne Zeeman laser that emits two partial beams of different frequencies polarized orthogonally to each other, (ii) A grating mounted on a slide table and (iii) A heterodyne interferometer where the beams of the ±1st order diffracted on a grating are superimposed and a beat signal, which has a phase shift δφ depending on an in plane displacement δx of the grating, is generated. The straightness of a slide table can be measured, because the phase shift δφ is proportional to the in plane displacement δx in principle. In this study, two different types of interferometers, which we call "Mach Zehnder type" and "Michelson type", are developed. Using each interferometer, the straightness of a slide table is measured experimentally. As a result, in "Michelson type", a straightness measured by the new optical system is good agreement with one measured by a laser interferometer commercially obtained. The effectiveness of the new optical system is confirmed by this experimental result.

View full abstract

Transformation of the medial arch angle of human foot was observed at sagittal plane during gait cycle by two methods : X ray television and Computer Aided Video Motion Analysis (VICON). Although the X-ray television has access to measurement of angles between templates, the X ray television has problems such as exposure to radiation, human error in acquiring digital data out of the templates, and low sampling late of Digital Radiograph-Fluroscopy. The VICON is a method to measure 3D coordinates of markers attached at the surface of the foot by 3D video tracking system, then estimate medial arch angle of the templates from the 3D markers. Transformation of the medial arch angle at stance phase were measure by the X ray television and the VICON, and results of the two methods were compared. The transformation pattern estimated by the VICON was approximate to the transformation measured by the X ray. Use of the VICON for the estimation of the medial arch angle of human foot was confirmed.

View full abstract

In this paper, a control method for trajectory tracking control is discussed. The control method which has a multiplicative effect on disturbance decoupling is derived by combining the internal model control (IMC) and limiting properties of LQ control. Then the proposed control is applied to trajectory tracking for a two links robot manipulator. Experimental results show that the proposed method is effective on robot trajectory control.

View full abstract

Device in human machine interface such as interactive force display system requires not only high power and quick response, but also safety for human. Magnetorheological (MR) fluids are materials that change their rheological behavior by an applied magnetic field. The devices using MR fluids have an ability to provide high torque, low inertia, safe device and simple interface. In this study, we propose the magnetic circuit method to develop an actuator using MR fluid. The magnetic characteristics is analyzed by means of the finite element method. In order to investigate the characteristics of the developed MR fluid actuator, the experiments are examined. Finally, the torque control system is constructed and the response of torque is improved.

View full abstract

Keeping haptic interface stable is one of the most important issues for haptic interface, because haptic device has direct contact with operators. Virtual environment is discretely calculated in computers and the discrete-time system adversely influences stability. In this paper, we propose a new haptic interface with a device which realizes spring and damper effect by an electric circuit. The springs and dampers can continuously generate impedance on the tip of the haptic device. We propose utilizing the continuous time impedance for haptic interface to decrease the influence of the sampling period. We discuss the composition of electric circuit and analyze the stability of the proposed method when it is applied to 1-DOF display. Finally, we perform some experiments with a two dimensional haptic display device to show the effect of the proposed method.

View full abstract

We have proposed two different digital control methods, where the controlled variables are joint torque and joint angular velocity, of space robot manipulators using the transpose of Generalized Jacobian Matrix. These methods are developed in discrete time domain so that the stability of system can be guaranteed when digital computers are used as controllers. The relation between the two methods, however, is not reported, although the basic concepts of these methods ar similar. This paper presents a novel digital control method, which integrates joint torque control with joint velocity control, of nonredundant space robot manipulators using the transpose of Generalized Jacobian Matrix. The merit of this new control law is to be applicable to both joint's torque controller and joint's velocity controller by only tuning the controller gains. Furthermore, computer simulation of a 6-DOF space robot manipulator is performed. Simulation result demonstrates the effectiveness of the proposed method.

View full abstract

Some manipulation tasks have a direction of end-effector acceleration of a manipulator and directions for which dynamic accuracy is required in the motion. This paper presents a new index (DAIT : Dynamic Accuracy Index for Task-directions) that allows us to evaluate the dynamic accuracy of manipulators considering the task-directions. First, the DAIT is derived. Second, the geometrical relationship of the DAIT to the dynamic manipulability ellipsoid is represented. Third, a manipulation performance of a planar 2-DOF manipulator for a task is evaluated on the basis of some indices that have been proposed and the DAIT. Finally, from these evaluation results, it is shown that the DAIT is useful to evaluate the dynamic accuracy of manipulators for the task-directions.

View full abstract

This paper presents a new method for evaluating an input/output characteristic of a manipulator. The proposed method can clarify a required torque and velocity for a manipulator outputting isotropic force and velocity, translational and rotational components of which are evaluated independently. This study calls such a characteristic as actuatibility. Actuatibility can be easily evaluated by solving the eigenvalue problem of Jacobian which reveals the infinitesimal input/output relation of a manipulator. The evaluation of actuatibility will reveal an appropriate configuration of a manipulator, required specifications of actuators and so on, thereby bringing the improvement of various performances of a manipulator. This paper has especially clarified the actuatibility of an in-parallel actuated manipulator and compared the proposed method with the evaluation of manipulability which is a representative method evaluating of an input/output characteristic of a manipulator. As a result, it has been confirmed that the proposed method will be more practical for derermining the configuration, selecting the actuators of a manipulator and so on.

View full abstract

In this paper, a trajectory planning method of a mobile manipulator is presented. We derive the dynamics of the mobile manipulator considering it as the combined system of the manipulator and the mobile platform. The planning problem is formulated as an optimal control problem. To solve the problem, we use the concept of the order of priority. A gradient based iterative algorithm which synthesizes the gradient function in a hierarchical manner based on the order of priority is used. The simulation results of the 2-link planar nonholonomic mobile manipulator are given to show the effectiveness of the proposed algorithm.

View full abstract

This paper proposes a new model and method for knowledge acquisition for planning problems in manufacturing, such as production planning, packing problems, and so forth, based on a problem solving process of a planner. In our proposed model, knowledge used for solving the objective problem is obtained through construction of state action network. A state action network consists of states describing some phases of the problem solving process and planner's actions in each phase. Moreover, reinforcement learning is used to refine the obtained state action network and to evaluate the problem solving process. We apply the proposed method to two dimensional packing problems and demonstrate its applicability and effectiveness through some computational experiments.

View full abstract

We proposed a self-organised manufacturing scheduling and proved the abilities of multi-agent paradigm with simple architecture and algorithm to move appropriately in relation to several process machines. This paper studies the effects of information sharing amongst agents to context formation in the self-organised scheduling Simulation experiments indicate the information sharing plays an important role to obtain efficient individual behaviour. The work agents are observed to naturally formulate the context with coordinated motions.

View full abstract

In such as collision warning systems and automatic braking systems, it may be difficult for deciding a suitable timing affecting their effectiveness. Thus, toward designing these systems with human factor considerations, a real-world experimental study was conducted. From the data we decided the most suitable visual information (e.g., distance, headway time, and so on) as the index for assessing the collision danger associated with a lead vehicle or a stationary vehicle. The result showed that the index had the dependency of driving situation such as approaching a lead vehicle and avoiding the collision for a stationary vehicle. Using the obtained indices, a display system of collision dangerous assessment was developed and showed the effectiveness experimentally.

View full abstract

Idlers are widely used in synchronous belt drives in order to adjust the center distance and in order to increase the angle of contact. A meshing phase angle occurs when an idler is attached and this is thought to generate a transmission error. In the present study, a transmission error having a period of one pitch of the pulley was investigated both theoretically and experimentally for synchronous belt drives with an idler attached on the belt span. The experimental conditions were such that the speed ratio was one under a quasi-static condition and no load. The experimentally obtained transmission error that occurs due to the idler agrees closely with the computed result. In addition, changes in tooth load and frictional force have a greater influence than change in meshing phase angle on the magnitude of the transmission error. The magnitude of the transmission error is affected when the idler is moved in the direction normal to the bearing stand, and is unaffected when the idler is moved in the direction parallel to the bearing stand. Furthermore, when the diameter of the idler increases, the transmission error remains constant. However, when the diameter of the idler decreases, the transmission error increases.

View full abstract

Helical synchronous belts have been confirmed to reduce transmission error and noise. However, side tracking in the axial direction occurs in helical synchronous belts under no load. When torque acts on the belt, in addition to incurring side tracking, offset, which is a difference in the axial direction between the belt on the driving pulley and the belt on the driven pulley, is occurred. It seems that side tracking and offset result in damage at the side face of the belt because the belt is forced against the pulley flange. Therefore, it is necessary that it clarifies the process in which side tracking and offset grow and investigates methods for reducing side tracking and offset. In the present study, side tracking and offset in a helical synchronous belt were investigated both theoretically and experimentally under torque. The experimental results were agreed closely with the calculated values. Side tracking was confirmed to occur because of shearing strains of the belt at the beginning of meshing and offset, and could be reduced by lowering the installation tension. Offset showed to increase proportionately with torque.

View full abstract

A N-type constant-torque spring is made of pre-stressed material and offers the advantage of constant torque and is being made in various sizes, suitable for a variety of applications (for example, drive mechanism, counterbalance, retracting and restoring mechanism). This spring takes the form of a tightly wound spiral and is placed on two drums. When the device is wound up by winding the spiral from the first drum to the second drum, the curvature of spiral is reversed. In this process, the constant torque is developed due to the tension plus the reverse bending moment of the spiral. In this report, the mechanism of constant torque and states of deformation are analyzed by using a large deformation theory. Moreover, an experiment is carried out to confirm the applicability of the proposed theory. The experimental results agree well with the theoretical estimations.

View full abstract

A novel finite element method for solving the time dependent lubrication problem using spatial elements and time elements has been formulated, and an alternatively iterative solution method of the lubrication equation and the dynamic equation has been derived. The alternatively iterative method was permitted by incorporating the mathematical iterative step for solving nonlinear lubrication equation regarding the spatial axis into the time step for solving it with respect ot the time axis. This method was applied to solving transient response of a flying head slider for magnetic disk storage use. From waveform of the transient response, the natural frequency and the damping ratio were identified by means of the regression analysis. The calculation results were compared with those resulting from the current two methods; the alternating direction implicit (ADI) method and the perturbation method. From the comparisons, the natural frequencies and the damping ratios were found to be in good accordance except for the damping for a higher order mode. It is interesting to note that a peculiar numerical phenomenon appears both in the present and ADI methods wherein the natural frequency remains almost constant with a varying time increment while the damping ratio varies showing a tendency of saturation with a further shortening time increment.

View full abstract

This paper clarified the effects of accommodation coefficient, which characterize the gas surface scattering at the boundary surfaces, on molecular gas film lubrication charcteristics by the use of the molecular gas film lubrication (MGL) theory and the Direct Simulations Monte Carlo (DSMC) technique. Using the MGL theory, flow rate coefficient Q_P in the MGL equation and shear stress coefficient W_C in Kang's formula, which reflect molecular gas effects, are rigorously calculated with accommodation coefficient α and inverse Knudsen number D as a parameters. An inverse step-type slider with nano-meter spacings was analyzed by the use of these coefficients, and the lubrication characteristics especially normal pressures and shearing stresses are compared with each simulation method. It is found that pressures and shearing stresses by the two methods are in good agreement with each accommodation coefficient. This means that MGL theory and these coefficients we calculated will be correct.

View full abstract

Squeeze film effect between a porous surface and a rigid surface is investigated as a problem of visco-elastic hydrodynamic lubrication (VEHL). An axisymmetric continuum model is introduced based on a three element visco-elastic model to estimate the deformation of a cylindrical porous rubber block. The coefficients in the visco-elastic constitutive equation are experimentally determined and the deformation is calculated by FEM. To take into consideration the fluid inertia effect in the squeeze film, the approximate solutions for the film pressure are obtained from the Navier-Stokes equation and the continuity equation using the perturbation method. The squeeze-film pressures and forces are measured under the sinusoidal squeezing motion with a cylindrical porous rubber block. The difference between the VEHL solutions and the EHL (elastohydrodynamic lubrication) solutions becomes more marked for a higher frequency of squeeze oscillation due to the effect of viscoelasticity of the porous rubber. Hence, the VEHL solutions correspond better to the measured results and yield a smaller surface deformation of the porous rubber block than the EHL solutions as the frequency of squeeze oscillation increases.

View full abstract

A theoretical study is carried out to investigate the squeeze film phenomena between a cylindrical porous rubber block and a rigid plate. The porous rubber block is stationary, while the rigid plate is oscillated sinusoidally in the direction perpendicular to its surface or dropped on the porous rubber surface, subjected to its own weight and the squeeze film force. The deformation of the porous rubber block is evaluated with an axisymmetric continuum model based on a three element visco elastic model. The approximate solutions for the film pressure including the fluid inertia effect are obtained using the perturbation method. for each type of rigid plate motion, the numerical results show various effects of the permeability of porous rubber block and the fluid inertia force on squeeze film characteristics such as the film pressure, force, thickness and the leakage flow from the squeeze film.

View full abstract

This report describes a new method to finish tooth flanks of pinion cutters by form grinding with multiple relieving motions, which are the approaching motion between the grinding wheel and the pinion cutter, the rotational motion of the pinion cutter and the shifting motion of the grinding wheel. The method can successfully finish the whole depth of the cutting edge of the pinion cutter with an arbitrary profile by one-pass grinding for each tooth flank. The motions were decided as to minimize the cutting edge errors at two regrinding positions. As an example of profile calculation and the finishing test, the involute helical pinion cutter with a protuberance was selected. The profile of grinding wheel was calculated by applying the element removal method. The finishing test was conducted on the NC form gear-grinding machine and the pinion cutter with almost no profile error and a small regrinding error was obtained.

View full abstract

In this paper we describe the effect of die-sinking EDM under mirror finishing conditions on mirror surface properties of four-different types steel, SKD11, NAK55, PX5 and SKD61, which contain the free cutting element, sulfur. In particular, the influences of the quantity of sulfur on the machined steel surface, the composition and microstructure with die-sinking EDM. The following conclusions were obtained. 1) A mirror surface of steel containing more than 0.04% sulfur could not be realized. 2) In the case of steel with 0.1% sulfur, the surface property is dependent on the machining direction. 3) Pits are generated on the machined steel surface because the aggregated part of the MnS fiber preferentially melts with the circumferential base metal. In addition, the quantity and shape of pits change according to those of MnS. In the longitudinal section, the shape of the pit is a series of channels, whereas in the transverse section it is a cirele.

View full abstract

An autonomous NC machine tool is required to have several functions, such as the optimization of outting conditions, and the avoidance of cutting troubles during machining operation. The virtual copy milling system has been developed to achieve these functions. This system based on copy milling principle is able to generate tool paths in real time. In this paper, the collision check between the stylus and the master model to generate tool paths is improved and completed to avoid over cutting. Furthermore, contour-line machining is realized besides scanning-line machining performed in the previous report. Experimental milling is succeeded to show NC programless machining of sculptured surface.

View full abstract

In order to realize higher machining accuracy and higher productivity, it is required to materialize the table system which has capabilities of nanometer order positioning accuracy and high speed feed drive. In particular, nanometer order tracking accuracy is urgently required in semiconductor production systems. Accordingly, it is increasing to apply a linear motor and aerostatic guideway to the table systems. The linear motor-driven aerostatic table system has the advantage of non-contact direct drive, however, disturbances such as the force ripple of the linear motor deteriorate directly tracking accuracy of the table. In this paper, therefore, the performances of the linear motor-driven aerostatic table system using a repetitive control method were evaluated. Furthermore, through a series of experiments, it was proved that the repetitive control method could restrain tracking error caused by various factors.

View full abstract

Controlled ecological life support system (CELSS) is a unique tool for researches such as test beds for the global change problem and the large-scale life support system in outer space. Growing rates of kidney bean and structure of the tissue were investigated by the plant culture system in which the pressure of the atmosphere and the concentration of CO₂ could be adjusted. The growing rate of the leaf was made to increase by the decompression. The effect, however, was decreased by the increase in CO₂ concentration. the growing rate of the stalk was made to decrease by the decompression. The adaptive remodeling of the tissue arising from the decompression was observed through microscopy. Auxin (indole-3-acetic acid) had the physiological activation that loosens the cell wall even in the decompression. But the synergistic effect of the decompression and the physiological activation of the auxin was small.

View full abstract