This paper deals with nonlinear vibrations of a two-degrees-of-freedom system with clearance. The resonance curves of harmonic, higher-harmonic and ultra-subharmonic vibrations are obtained using the direct numerical integral method previously presented by us, which is a kind of shooting method and is highly accurate. Beat, chaos and hyper-chaos are also determined numerically. Influences of acceleration amplitude and frequency of base excitation on the vibration characteristics are discussed. It was found out that (1) higher-harmonic vibrations which had the islandlike resonance curves occurred in a large base excitation amplitude, (2) there were two routes to chaos, namely, period doubling route and torus doubling route, and (3) hyper-chaos was found for the first time in a mechanical system.

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This paper deals theoretically and experimentally with the nonlinear vibrations of a structure caused by water sloshing in a cylindrical tank. The structure carrying the tank is horizontally subjected to sinusoidal excitation. In a theoretical analysis, the modal equations for this coupled system are derived, and the analytical equations for the resonance curves of the harmonic oscillation are presented when the water surface is in a state of planar motion. According to the derived equations, the numerical calculations are carried out for a tuned condition such that the natural frequency of the structure is equal to the natural frequency corresponding to the fundamental sloshing mode. As a result, it is found that the resonance curves change from soft spring type to hard spring type as the water level decreases. These results agreed quantitatively well with the experimental results.

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This paper deals theoretically and experimentally with the nolinear vibrations of a structure caused by water sloshing in a cylindrical tank. The structure carrying the tank is horizontally subjected to a comparatively large sinusoidal excitation. In a theoretical analysis, the resonance curves are obtained by swept sine test in a numerical simulation of the modal equations. As a result, it is found that a swirl motion of the water surface and an almost periodic oscillation of the structure appear in certain regions of the excitation frequencies. In addition, a super-summed-and-differential harmonic oscillation can occur at the tuning frequency. These results agreed quantitatively with the experimental results.

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A simplified FEM vibration analysis program is developed for laminated composite cylindrical beam structures. In this program, a composite cylinder which has various diameters and thicknesses laminated in various fiber orientations is modeled by a single beam element to decrease the degree of freedom of the vibration problems. Therefore, eigenvalues and transfer functions of laminated composite cylinders can be analyzed without influence from the aspect ratio of the element. In the transfer function analysis, a proportional viscous damping is assumed and a method of surmising theoretical damping is utilized. Using this program, the eigenvalue and the transfer function of CFRP golf club shafts are analyzed. And compared with the experimental results obtained by the impact test. As a result, the validity of this program is proven because the analytical results show good agreement with the experimental ones.

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This paper deals with a new method for analysis of lateral vibrations of flat plates of various shapes. A general solution is derived as a linear combination of particular solutions of the governing equation. To determine the natural frequencies and the natural modes, the collocation method and the method of virtual work are used. Programs for computation are very simple because of simplicity of the basic principles. The natural frequencies of circular, elliptic, square and rhombic plates with clamped edges and square and rhombic plates with free edges are calculated as numerical examples. The results agree well with the exact values or the values which have been obtained so far by various methods of approximation. This method may be used not only for plates of various shapes and with various boundary conditions but also for structures containing plates as elements.

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This paper deals with pattern formation of smoother roll covering rubber in a paper-making machine and its countermeasures carried out using a controlled damper roll, taking the lateral deformation of the rolls in the axial direction into account. The authors describe the modelling of the system, record this vibration phenomenon as unstable vibration due to time lag and attributable to the viscoelastic characteristics of the rubber. It was made clear that (1) the pattern formation due to the rigid modes and the elastic modes between the top and bottom rolls was easily quenched by the external friction of support-bearing parts, and (2) that due to the combined rigid and elastic mode, called convex mode, between the top and bottom rolls was effectively quenched not by the external friction but by the internal friction and the additional rigidity generated using the controlled damper roll.

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In aeroelastic tailoring or aeroelastic control, the bending-torsional coupling effect for a composite wing has been utilized. As a fundamental study on aeroelastic tailoring, this paper examines the vibration characteristics of cantilevered laminated plates with bending-torsional coupling using lamination parameters which can express every laminate configuration. Effects of laminate configurations and bending-torsional coupling on vibration characteristics are studied through the representation of natural frequencies on a lamination parameter plane. Effects of sweep angle on natural frequencies and associated mode shapes are also discussed for a composite wing model.

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The optimal placement of storey-installation type damper for vibration control has not been established yet. In most cases, dampers have been installed uniformly in each storey. However, this method is thought to be inefficient placement in that it produces different energy dispassions between low and high storeys. This study applies genetic algorithm (GA) to an optimal placement problem of a storey-installation type damper. The parameter survey by GA used a 5-storey building model and the storey-installation type damper model was investigated by applying various parameters in order to obtain more rapid convergence of the algorithm and correctly converged results.

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A method determining the optimum placement of vibration control actuators using the Voronoi diagram was proposed focusing on the continuous planar structures. The entire plane is partitioned by a Voronoi diagram which consists of the same number of polygons as that of vibration control actuators. The objective function consisting of the locations of actuators and vibration mode amplitude is minimized for optimization. The location of actuators obtained by the proposed method was found to have effective vibration control capability through finite-element response analyses.

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We present a system for reducing noise from structures using electromagnetic vibration absorbers. Conventional design techniques for vibration absorbers are not appropriate for noise reduction absorbers, because higher-mode vibrations exert strong effects on noise. Hence, we first derive an analytical expression for noise power including higher modes, then present a method for obtaining optimal parameters for noise reduction absorbers. In this method, noise power is taken as a function of cost, and the parameters are decided by using a neural network procedure. An improved algorithm of the neural network for obtaining the parameters is given, experimental tests are performed and the theoretical values are compared with the experimental data.

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The construction and the frame with a fin in a totally enclosed induction motor have almost the same design worldwide. A method for estimating natural frequencies of a stator core pressed into the frame of this type of motor was found by a finite-element method (FEM) analysis. First, the number of circumferential contact points between the inner surface of the frame and the outer surface of the core was determined by experiments and FEM analysis. It was confirmed that the number of circumferential contact points was three. In these analysis, spring elements with radial and circumferential spring constants were set at these contact points. Good agreement in natural frequencies obtained by measurement and by FEM analysis was attained when the number of spring constants in the radial direction was infinite and that in the circumferential direction was finite. FEM analysis with spring elements at contact points is useful in practical applications to obtain the natural frequencics of a stator core with frame.

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A method of levitation control of an induction-type motor is proposed. It is assumed that the stator has a current sheet which can produce an arbitrarily distributed magnetic flux, while the rotor is assumed to have a uniform magnetic property where the induced current is produced of the same form as that of the rotor magnetic flux. The levitation force can be produced and controlled by a proposed ±2 pole algorithm. A horizontal experimental apparatus is fabricated to validate the proposed method. In this paper, the load torque and the radial force capability are tested using a torque test apparatus and the rotor gravity as the radial load. The results obtained are discussed in detail.

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In a previous paper, the authors proposed a new identification technique for a rotating shaft system and confirmed the applicability of the technique by numerical simulation. In the present paper, the applicability of the technique is investigated by applying it to a real system. In a preparatory study, it was found that the initial deflection of the shaft had a significant effect on the accuracy of identification. Hence, before applying the technique, the governing equations on which the technique is based are modified so that they include the effect of the initial deflection. Then, the technique based on these modified equations is applied to an actual rotating shaft system with a rotor at its mid span. The responses predicted by the identification are compared with those obtained by experiments. In this way the applicability of the technique in a real system is confirmed.

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Only the natural frequencies and the modal damping ratios are the unknown parameters in the iterative process, and the natual modes and the residual terms are determined from these unknown parameters. The number of unknown parameters is smaller, and convergence of solution in the iterative process is better in the presented approach than in the conventional one. It is clarified by simulation that the presented approach is especially useful in cases where many data are referred to simultaneously.

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An approach is presented for the identification of modal parameters in frequency domain in an experimental modal analysis with multiple frequency response functions, using the non-linear least squares method and the optimization method. Computation time is reduced, and, stability and accuracy of results are improved compared with thone of conventional approach, when input bata are contaminated with errors. Validity and usefulness of presented approach are verified experimentally with an iron plate.

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An approach is presented for the identification of modal parameters in the frequency domain in an experimental modal analysis with multiple frequency response functions. With improvement of the calculation method and reduction of the FRF matrix, computer time for calculation becomes shorter. Experimental modal analysis and FEM calculation are done on two structures. The results of experiment and calculation agree well up to 4000 Hz in 51 and 25 modes. Validity and usefulness of the presented approach are verified by these agreements.

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Design of practical structures can involve difficulties when it is based only on analytical models. Experimental data are therefore often made use of for such cases. There have been many studies on identification of statistical and dynamical characteristics of structural systems, making use of experimental data. In this study, we propose a method to identify the characteristics of structures with proper accuracy by using a hierarchical neural network (HNN) that has excellent projection ability even for systems which have nonlinearities. HNN has been generally used to learn dynamic characteristics with minimum number of experimental data. We use HNN as the solver of an optimum design, that is to estimate the dynamic characteristics and sensitivities. The effectiveness of this method is demonstrated through several numerical examples and experiments. Then we utilize the derived sensitivities for gradient-based optimization techniques and to solve the optimum design problems. It is found that the proposed method is valid and effective for such optimum design problems.

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This paper deals with an application of Electrorheological (ER) fluid to a squeeze film damper which enables reduction of whirling amplitude of rotor by adjusting the damping property at each rotating speed. An experimental model composed of a flexible shaft and a controllable ER squeeze film damper was constructed and its performance was studied under various electric field strengths. The ER Fluid used in the present experiment was a colloidal suspension of silica powder in mineral oil. Furthermore, a theoretical approach to investigate the performance of ER squeeze film damper under an electric field was made in which the short-bearing approximation of a journal bearing with Bingham plastic fluid was introduced. It was concluded that the continuous change of natural frequencies of a flexible shaft caused by supporting damping variation could be measured experimentally and that the simplified theory introduced in this paper showed good agreement with the present experimental results.

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We propose a new type of hydraulic shock absorber whose resisting force matches impacts of various masses using electro-rheological (ER) fluid having apparent viscosity that can be modified by an electric field. In this paper, we show by simulation that the maximum acceleration of the light body nearly equals that of the heavy body, which has twice the mass of the light body, during impact for the proposed shock absorber, while the maximum acceleration of the former is 2. 3 times that of the latter during impact for the existing hydraulic shock absorber, whose resisting force is expressed as a function of the relative displacement and squared of the relative velocity of the piston.

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This paper presents the working principle and the control performance of a hydraulic actuator system driven by a multilayered piezoelectric element. The main parts of the system are an accumulator, a reciprocating pump driven by the piezoelectric element, a single-rod cylinder and a control valve. The control valve is a variable throttle valve inserted between the rod-side and the head-side ports of the cylinder. When the pump is driven by its maximum voltage, the control valve is shut off, and the piston rod is then drawn into the cylinder by the working liquid supplied from the pump. Inversely, when the voltage becomes zero, the control valve is open, and the piston rod is pushed out of the cylinder by the working liquid supplied from the accumulator. Thus, the velocity of the rod is manipulated by changing the voltage applied to the pump. The experimental device was constructed using a piezoelectric element of 22 mm diameter and 55. 5 mm length, and a cylinder of 12 mm inner diameter and 6 mm rod diameter. The positioning controller was desinged using PD, feedforward and phase-lag compensators and a disturbance observer. Then, the positioning accuracies of about l0 μm and 50 μm were obtained for the external load forces of 0N and 60N, respectively, where the response frequency was about l0 Hz. Numerical simulations based on a set of mathematical models were also carried out to confirm the control performance of the proposed actuator system.

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Recently, LQ optimal regulators have been successfully applied to design of active vibration control systems. Most of them have been discussed in terms of the closed-loop performance and the relationship to the performance indices. However, optimization through the entire design procedure has not been completed on passive elements. So, for optimizing all design parameters, we propose a numerical method which is based on the necessary condition for controller parameters and the performance sensitivities to passive parameter changes. The method includes an iterative procedure ; the convergence is examined using 2-degree-of-freedom models. It is shown that the proposed method provides good closed-loop performance and LQ optimality.

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Fuel cells, which have been given much attention in recent years, are now actively being studied and developed. However, their dynamic behaviors have not been fully discussed due to their complicated structures. This paper first explains the nonlinear dynamic models which show temperature behaviors by considering heat and mass balances in the cell. Then, we attempted to construct a control system by using feedback linearization to compensate for the effect of load change. Finally, it is shown by computer simulation that this system is quite effective.

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In this work we consider unstable control objects such as an inverted pendulum. Two evaluation procedures in genetic algorithm (GA) are set. The first involves the following steps : set two limits, -Θ and Θ, on both sides of the unstable equilibrium point, set an initial point θo in [-Θ, Θ], initiate a motion, measure the time when the motion reaches one limit, repeat simulations of neuro-control, select neural networks in order of length of holding times, and apply GA-crossover to superior neural networks of long holding times. The second involves the following steps : select neural networks in order of shortness of settling time to the equilibrium point, and apply GA-crossover to superior neural networks of short settling times. We adopt only the first evaluation procedure in the early generation stages of GA. After the number of neural networks of controllability reaches a sufficient percentage of all the neural networks in a computer, we adopt the second evaluation procedure, and GA evolution is continued. Neural networks of controllability appear at about the 10th generation and evolve to the ability limit predetermined by the structure of neural networks.

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Fluidized bed incinerators can burn waste in a short time by stirring waste and fluidized sands. However, recently refuse shows various temperament and high calorie output. Changes in quality and quantity of waste cause fluctuations in combustion, and burning in fluidized bed incinerators is sometimes incomplete when much waste is supplied at one time. Furthermore, since these combustion systems are nonlinear and multi-variable, it is difficult to form mathematical models and to control them through an ordinary control algorithm. Therefore we adopted a neural network controller which can express characters as nonlinear and multi-variable. The proposed neural network controller learns so as to reduce disturbances, such as changes of waste type, adaptively in a stability area, together with controlling by an ordinary controller. We call this neural network control system RANC (robust adaptive neurocontroller). The method was applied to a real plant. The manipulated variable is amount of secondary air to the freeboard and the controlled variable is the concentration of O₂. O₂ is used as an index of stable combustion. The usefulness was verified since this method was able to reduce the fluctuation of O₂ concentration and CO concentration.

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For a small underwater robot floating in water, arm positioning requires cooperation between arm actuators and thrusters installed on the body for mobility and attitude control, because the robot can be moved by fluid drag force and inertial force acting on the arm. The body of an underwater robot is approximately spherical. The thrusters require high power due to weak resistance to body rotation, and rapid positioning also requirs high power. When the thrusters become powerful, the dynamics cannot be ignored. In this study, the thruster dymanics is investigated, a thruster model is proposed, and the arm positioning system of the underwater robot floating in water is developed based on the optimal control theory considering the thruster dynamics. Then a linearization method appropriate to the optimal control is examined by computer simulations. The performance of the developed control system is confirmed with the experimental models.

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In an underwater robot, the maximum stress at the end of the manipulator clamped with the shaft can be suppressed by using a thruster instead of a DC motor. Therefore, the thruster must be powerful enough for speedy positioning. As the thruster becomes more powerful, consideration of its dynamics becomes more important to achieve accurate positioning. In this study, a thruster model considering its dynamics is derived and a method to identify its parametes is proposed. The advantage of this method is that measurement of the screw speed is unnecessary. A positioning system for the underwater flexible rotating arm with a thruster is developed using the optimal control theory. Then, an underwater arm system is fabricated and control experiments are carried out. As a result, the control system without consideration of thruster dynamics cannot position the arm, but the system with consideration of the thruster dynamics can position it for about l second.

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Analysis method of vehicle handling characteristics and stability has been carried out by using the system matrix for state variables. The effects of the terms of the system matrix on the performances have been clarified and the evaluation method using these terms has been derived. It has been verified that the control law derived from this evaluation method improves vehicle handling characteristics and stability in integrated control.

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The analysis applied to a linear system in the first report is applied to a nonlinear system in this report. Expression in terms of state plane and velocity vector of trajectory makes it easy to analyze vehicle dynamics for nonlinear tire characteristics. Using this expression, local stable range (vehicle outside this range cannot maintain steady state) and "convergent" range (vehicle outside this range cannot converge to equilibrium) are distinguished. These ranges vary with tire characteristics and 4WS control law. By considering these ranges, it is verified that the 4WS system gives a larger stability margin under nonlinear conditions than 2WS.

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This paper proposes a control method for the power assist system which is used to attenuate the load force. In the power assist system, selecting suitable power assist ratios is important. The power assist ratio must be selected with consideration of the maximum torque of actuators used in the system. When the system has an excessively large ratio, actuator saturation occurs which causes the lack of maneuverability and stability. To avoid such saturation problems, a control method in which the gravity load is assisted with a ratio different from one for the dynamic load is proposed. The gravity load applies to the operator every time a load is supported. The dynamic load applies to the operator only when the operator moves the load. With this consideration in mind, the method proposes that the ratio for the dynamic load should be selected considering the remaining actuator torque usable after the ratio for the gravity load is determined considering the operator's capability. The control method is formulated for a single-axis power assist system and the effectiveness of the method is confirmed by experiments.

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An electric vehicle with a motor in each of its wheels has a higher degree of freedom of vehicle dynamics control than conventional vehicles because the steering and traction forces of each wheel can be controlled independently of those of the other wheels. Taking note of this special feature, a new electric vehicle with high maneuverability, i. e., the ability to move obliquely or laterally or to make a turn given a very small space has been developed. Such improved maneuverability has been realized with a wide-angle steering system comprised of steering and other related mechanisms and their control devices, which can set the maximum steering angle for the front and rear wheels at 90 degrees or greater. This paper deals with the special steering system of the new electric vehicle.

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As for an automotive automatic transmission, a total control system using estimated output shat torque has been investigated in order to enhance drivability and improve fuel economy. The system provides efficient control for both engine and transmission, which leads to an enhancement of drivability by reducing shock during gear shifting. This paper describes a new smooth gear shift control method especially for 2-3 upshift using the total control system based on torque. A test vehicle equipped with an electronically controlled throttle valve has been developed and the effectiveness of the proposed control method has been verified.

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Active suspensions have been considered for improving the ride quality of railway vehicles. Recently various control methods have been proposed. In this paper preview control is studied. Preview control, a kind of feedforward control, has two disadvantages. ( 1 ) Preview control does not increase the stability of a system. ( 2 ) Safety problem occurs from the practical point of view when it fails. In order to compensate the above disadvantages, a combination control by preview and H_∞ feedback is considered in this paper. Numerical simulations are performed for lateral vibration of railway vehicles. It is shown that preview control reduces the vibration with small control power and that H2 control (feedback control) reduces residual vibration even if errors exist in preview information. Furthermore, the effect of this control system is confirmed by experiments.

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In some three-dimensional flexible manipulators, the relationship between vibrations and actuators depends upon the manipulators' configuration. It has been reported that fixed gain vibration control in such manipulators makes the system unstable. Therefore, configuration dependence of such manipulators must be considered. In this paper, a configuration-dependent variblegain vibration-suppression control strategy for three-dimensional flexible manipulators is presented. The vibration control scheme computes the feedback control gain in real time depending upon the configuration. Thus, the scheme is effective for practical applications. The control scheme is examined by experiment for the case of a two-link seven-joint-type flexible manipulator. The stability of the control scheme is analyzed based on the location of closed-loop poles.

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Manipulators which can move by itself are called "Mobile Manipulators". In this paper we propose a calculation method of inverse dynamics compensation for a power-wheeled-steering (PWS) mobile manipulator. The Newton-Euler method is used for the compensation calculation. The mobile manipulator has a different characteristic from a floor-fixed manipulator in that it moves according to nonholonomic constraints. The constraints integrate velocity and angular velocity errors of the mobile manipulator on a floor, then the errors influence the hand position and orientation of the mounted manipulator. The integrated errors do not disappear even after the dynamical vibration of the mobile manipulator has settled. Therefore, to reduce the integrating errors, the velocity errors of the mobile manipulator should be reduced. We propose a method of inverse dynamics compensation, and comfirm the effects by simulation experiments.

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Dynamic control approaches (decoupled algorithms) for a Coupled Tendon-Driven Manipulator Arm (or CT Arm) are presented in this paper, in which the dynamics of a manipulator arm also the dynamics of a tendon-driven system are considered for the case of high speed motion. The mechanism for the CT Arm is a special tendon traction transmission mechanism, in which a pair of terdons used to drive a joint are pulled from base actuators via pulleys mounted on the base-side joints. The mechanism can optimally utilize the coupled drive function of the tendon traction forces and thus enables the lightweight manipulator to exhibit enormous payload capability. Its properties will be elucidated by the proposed dynamic control approaches. Computer simulation was also executed in this study to verify the validity of the proposed control approaches.

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In this paper, we propose a control algorithm of dual manipulators handling flexible sheet metal ; we discuss how to bend sheet metal and how to manipulate it. First we derive the relationship between the static deformation of the sheet metal and the bending moments exerted on the sheet using the Lagrange equation based on its finite-element model. We then design a control algorithm by which the motion of the manipulated sheet is controlled using the resultant force applied to the sheet, and the deformation of the sheet is controlled using the internal force applied to the sheet. Since the rigidity of the deformed sheet is not uniform, that is, the stiffness of the deformed sheet may depend on the direction along which the external force is applied, we cannot use the compliance of the flexible sheet for tasks involving interactions between the sheet and its environment. The proposed control algorithm is designed so that the apparent impedance of the manipulated sheet metal is specified. The experimental results using industrial robots illustrate the validity of the proposed control system.

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This paper presents an adaptive tracking control scheme for robot manipulators with flexible joints using only the information of the motors as feedback. The states of linkage are estimated by a robust sliding observer. Stability of the dynamic control system with the sliding observer is confirmed using Lyapunov stability theory. To illustrate the effect of the algorithm upon combination of the controller and the observer, computer simulations have been carried out using SCARA-type 2-DOF manipulator.

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As miniaturization of exposure patterns progresses, high positioning accuracy of submicron order is necessary for the semiconductor components. Moreover, in order to transcribe the circuit pattern to multiple positions on an IC wafer, a positioning mechanism with long stroke also must be developed. This paper focuses on the former. By driving the piezo actuators mounted under the flat plate, this mechanism has a positioning function with 3 degrees of freedom. This paper first describes a mathematical model of a fine motion mechanism with 3 d. o. f., and we confirm the adequacy of the control model by comparison with the measured frequency response. Secondly, both static and dynamic decoupling conditions for the controlled object itself are derived, and we show that this conditions are equivalent to that of the center of percussion. In the case of control for the positioning mechanism with multi-d. o. f., the matrix inversions are generally inserted into the control loop to cancel the interference based on the space assignment of both the position sensors and actuators. However, if the controlled object can be kinematically decoupled by the mechanical design, it is unnecessary to construct the complex control loop. Finally, we propose acceleration feedback in order to improve the control performance, and its superior performance is illustrated by the numerical simulation.

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In the previous report, we proposed a method of modifying the estimated directional angle with the laser beacon measuring system for a wheeled mobile robot (WMR). It dealt only with a stable area of modifying gains, which are necessary to calculate the modifying quantity of the estimated directional angle. But it did not deal with a method of deciding modifying gains. In the present report, we propose the method of deciding the modifying gains using both a simulation reflecting disturbance and a fuzzy reasoning. This method has two merits : firstly, a mathematically expressed exact model is not necessary because of using the fuzzy reasoning, and secondly, using the simulation for both the design of the fuzzy reasoning means and the decision of the modifying gains reduces the number of necessary experiments. Moreover, we conduct the experiment using the modifying gains which are determine in this paper, and show that they are effective in the trajectory tracking control for WMR.

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This paper deals with a micro-mobile robot in water utilizing PZT (Pb (Zr, Ti) O₃) as an actuator. A robot driven by PZT requires a magnification mechanism and the effects of resonance to enlarge the displacement of PZT. In this paper, we propose a prototype micro-mobile robot which has a new steering mechanism. The robot possesses a pair of legs, each of which has a pair of fins at some angle, which is essential to improve the performance of the robot. A leg gnerates force both forward and backward depending on frequency because the offset angle between a pair of fins functions appropriately. Therefore, the robot can steer efficiently by a combination of both modes. The size of the robot is 32 mm in length and 19 mm in width. This robot has many possible applications, such as inspection of small pipelines and use in biomedical fields.

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Focusing on the biological fixation mechanism, we propose a fixation technique, and implement it into an active vision system. In our technique, large and small camera movements are coordinated to detect an object precisely at the optical axis of the camera. Each type of movement is performed via two separate fixation methods : approximate fixation and adjustment fixation. In the former fixation, a preliminary fixation point is detected using the multi-resolution retina. After the optical axis of the camera is aligned in the direction of this point, the latter fixation method determines the precise fixation point by means of visual feedback control, which minimized the angle between the object's center and the optical axis of the camera. Experimental results show that the active vision system using our proposed technique succeded in fixating objects one after another in a scene, even if several objects are placed within it. According to these results, we have confirmed that bottom-up processing using primitive visual features is an effective technique for precise fixation.

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A novel method for detection of dynamic characteristics of biological soft tissues is presented. In this method, viscoelastic properties of soft tissues are measured indirectly by using free damped vibrations of small cantilever beam following a small impact applied at the beam end where a small piece of specimen is suspended. Natural frequencies and logarithmic decrements of the vibrations are measured in order to find out elasticity constant and viscous damping coefficient of the soft tissues. As a practical application, viscoelasticity of normal, hypertrophied, and cancerous human prostate tissues obtained at autopsy were measured. It was found that the present method was capable of detecting changes in viscoelasticity caused by these pathological changes, suggesting a feasibility of this method for the application of tissue characterization.

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In order to calculate the mechanical load on living tissues from measured kinesiological data, the human musculoskeletal system was modeled three-dimensionally by nineteen rigid segments and one hundred fifty -six muscles. The length, mass, and moment of inertia of each segment can be adjusted according to the subject's stature and weight. The muscle model includes several physiological elements that consume mechanical energy. The component ratio of muscle fibers can be changed arbitrarily. The proposed musculoskeletal model can be modified easily to a system with fewer segments or a two-dimensional system to suit the purpose of analysis. This flexibility increases the applications of the method to various motion analyses. As examples, we analyzed three-dimensional bipedal walking by a model without upper extremities, and rowing motion of whole body segments.

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Various types of visual substitutes have been developed for helping blind people to walk safely, and some of them have been applied in practice. However, most substitutes use stimulation elements which induce pain in users or occupy other important sense organs. In this study we attempted to develop a stimulation display which enables scenery recognition by the user by control of arrayed air Jets. New ideas have been applied in this display considering portability, speedy judgment of obstacles, and long term use without fatigue, and in particular, the need for small size, light weight, high speed and low noise. A visual substitute was constructed by combining the stimulation display with a 3 D range finder. One important feature is that this substitute obtains distances in 8 directions and enables the user to perceive distance through his perception without using his ears and hands. Through walking and shape recognition tests the practicability of this visual substitute has been confirmed.

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The forces and moments in the wrist and the elbow which are induced by striking a tennis ball were theoretically investigated. A dynamic model of a ball, racket and arm was simulated by two masses, a beam and two rigid bodies connected by springs. The modes of vibration and impulse response were calculated. The forces can be decreased by setting the striking point such that the translational and rotational movements at the grip cancel each other. The component of force with high frequency can be reduced by coinciding the striking point with the nodal point of the racket and by matching the natural frequency of the ball with that of the racket.

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Reducing distortion of the camera system should promise to improve the accuracy. In this paper we propose a new technique of reconstructing the camera property by using a neural network as learning mechanism. We show that relatively simple neural networks effectively eliminate the distortion for pin-hole camera model. We apply our method to synthesized image data with distortion in a simulation. By experiment, we verify that the performance is excellent.

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In this paper, a new type of aerostatic journal bearing with a self-controlled restrictor employing a floating bush is proposed in order to obtain very high static stiffness. The proposed self-controlled restrictor makes use of the force balance of fluid film pressures acting on the floating bush to control the gas flow entering bearing clearance. The effects of various parameters influencing the static characteristics of the proposed bearing are discussed theoretically and experimentally. Then the optimum design method for obtaining very high static stiffness is also discussed. It is consequently demonstrated that the proposed bearing is very useful for achieving very high static stiffness.

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An acoustic emission technique was developed to study the tribological characteristic of boriding SKD steel using a pin-on-disk type wear testing machine with acoustic emission sensor. AE signal of 300 kHz frequency spectrum generated by crack propagation in the specimens was observed in the wear tesing. The R. M. S. value of the emission signal was expressed in terms of wear and friction parameters, The experimental results showed that AE generation from pin contact with a rotating disk indicates the feasibility of utilizing AE in boriding metal wear sensing.

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A method to analyze meshing characteristics of helical gears with 3-D modified tooth surfaces under a no-load condition is proposed as follows. Firstly, the tooth profiles of the conjugate gear, having the same dimensions as those of the driven gear and meshing exactly with the driving gear, are calculated in multiple transverse planes. Secondly, the difference between the profiles of the conjugate and driven gears is calculated in the plane of action, which is defined "a meshing clearance" in this report. The meshing clearance shows the meshing characteristics of the driving and driven gears. Thirdly, the transmission error and tooth bearing pattern of the gear pair under a no-load condition can be calculated from the meshing clearance. To verify the usefulness of this method, meshing tests of the helical gears with the modified tooth surfaces were carried out and experimental results showing good agreement with the calculated ones were obtained.

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To clarify the scoring resistance, the seizure resistance and the fatigue strength of martensitic stainless steel SUS 440 C gears, of which the surface layer was thermally diffused at about 400°C after being Sn-plated, scoring tests and pitting tests were carried out using a power-circulating gear machine. From the tests, the following results were obtained. Under forced lubrication, the scoring resistance of SUS 440 C gears was considerably increased due to the Sn-diffused layer. Under dry friction, the seizure resistance of the gears with the diffused layer was at least twenty times as large as that of the gears without the diffused layer. Furthermore, a significant effect of the diffused layer on increasing the fatigue strength of SUS 440 C gears was recognized.

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