The free vibration of disk-blade coupled systems which have shrouds interconnecting the blades is investigated analytically. The effects of rotation are taken into account by estimating the potential energies due to centrifugal force for both the disk and blades, and artificial springs are introduced between the components to satisfy their continuity conditions. Shrouds are also replaced by artificial springs, and their masses are considered as concentrated masses attached to the blades. The orthogonal polynomials generated using the Gram-Schmidt process are employed as the admissible functions. The frequency equation derived by the present method is solved numerically and the effect of retation and the mass and position of the shrouds are investigated.

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A flexible shaft with an asymmetrical rotor exhibits a complicated change in amplitude of whirling when the shaft passes through the critical speed. The amplitude fluctuation is related to the torsional vibration of the shaft. Accordingly, analyses of the precise torsional vibration require equations of motion which hold an accuracy of the second-order of shaft deformations, shaft deflection, angle of deflection, and torsion. The driving condition of the shaft provides a constant angular acceleration. The present asymptotic solution demonstrates that the torsional vibration resonates at two rotating speeds immediately after the rotating shaft passes the critical speed of whirling. One of these resonance points appears owing to the asymmetry of rotor. The maximum amplitude increases and decreases alternately as the angular acceleration is changed monotonously.

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Microvibration control is becoming more important in high-technology fields such as semiconductor manufacturing, and influence of microvibration on precision machines is increasing. However, microvibration sensitivities of these machines cannot be measured using conventional vibration testing devices. In this study, using an active 6DOF microvibration control system with piezoelectric actuators, feasibility of a microvibration simulator is discussed. A control method is proposed based on the model matching method, which achieves almost the desired frequency characteristics using only absolute acceleration. Experimental studies are conducted with satisfactory results in isolation performance against micro-ground motion, and servo performance for various reference inputs.

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The purposes of this study are to clarify the characteristics of fluid film of a squeeze film damper (SFD) which consists of fluid film and centering springs, and to develop an analytical method which can simulate vibration phenomena of a flexible rotor system supported by the SFD's. It is also supposed that a squeeze film damper∼flexible rotor system is subjected to a base excitation, such as an earthquake with a vertical shock. The fluid film forces of the SFD were computed by solving the Reynolds equation for finite-length bearings. In the formulation of a rotating shaft, a finite-element method (FEM) was used to consider the elasticity and arbitrary shape of the shaft. We show the calculated results for the properties of the fluid films, vibration modes of the rotor system and time history responses in the case when the rotor system was subjected to a base excitation. The results of the calculations show that usage of the SFD's can effectively reduce the rotor vibration caused by both unbalance of the rotor and the base excitation.

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Achieving quiet and comfortable ride in a railway passenger car requires elastic vibration analysis of the passenger car body as a three-dimensional structure. This paper presents experimental and theoretical analyses of elastic vibration of a passenger car body at less than 30Hz. The body structure has one floor, two sides, one roof, and two ends, and each of these is composed of stringers, cross members, columns, reinforcements or panels. The three-dimensional FEM model has 670 elements, which are all beam or panel elements. The cross section of the model is formed from 11 connected straight lines, including 3 lines in the side and 4 lines in the roof. The theoretical analysis shows good agreement with the experiment, especially in the one-node floor bending, and slight difference in the two-node and the three-node floor bending.

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The driving system of a vibratory machine by self-excited vibration follows the resonance frequdncy change automatically and it reduces electric power consumption. The self-excited vibration is generated by positive feedback of vibration velocity or phase delay control of vibration displacement deviation on a mechanical resonance system. The amplitude of the self-excited vibration is limited by saturation of a power amplifier output. The vibration amplitude can be controlled by a variable saturation level. The frequency of self-excited vibration is equal to the phase crossover frequency on which the open loop transfer function of the system has a phase lag of 180°. The phase adjustment of the open loop transfer function realizes an agreement of the self-excited vibration frequency and the natural frequency of the vibratory machine. The self-excited vibration is suppressed quickly by switching from a feedback loop which generates self-excited vibration to a feedback loop which possesses a large phase margin.

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By using the corrugation formatting and developing model we successfully fixed the formatting and developing mechanism of rail corrugation on curved track. The frequency of corrugation is governed by the vertical dynamic system of the wheelset including the contact stiffness between rail and wheel, but not by the torsional dynamic system of the wheelset. From the simulation results we find that, (1) reducing the wheelset mass and static wheel load, (2) increasing the radius difference between inside/outside wheels in curving, the damping of axle suspension and axle torsional stiffness, are useful means to reduce corrugation. However, reducing axle suspension stiffness has almost no influence on the reduction of corrugation, because the contact stiffness between rail and wheel is much greater than the suspension stiffness.

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A method is introduced which suppresses the unbalance vibration of a rotor suspended by magnetic bearings, using two adaptive filtering techniques. The first filter separates the rotor displacement signal into rotation-synchronous and rotation-asynchronous components. The former signal can be cancelled by the output of the second filter, which allows estimation of the unbalance disturbance force using the impulse response of the plant of rotor with control system measured on-line under high-speed rotation. Both simulation and experimental results are shown to describe the basic and practical effectiveness of the proposed method. The system works well even when using only the initial part of the plant response.

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Unless the collocation requirement is satisfied, it is difficult to control the vibration of a mechanical system with direct velocity feedback control. In the control of a cantilever beam with a piezoelectric actuator and a displacement sensor, state-space methods are usually used because the actuator and sensor cannot be collocated. Though state-space methods are very useful, a large number of sensors at least equal to the number of eigenvalues concerned are needed to fulfill observability conditions. In this paper, a simple design for a stable dynamic compensator with which modal damping ratios of the mechanical system are greatly increased using a noncollocated actuator and sensor is proposed. Experimentally it is found that three natural frequencies of the cantilever beam are well damped with the designed compensator and calculated results of the mechanical system poles and forced response are consistent with experimental ones.

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Vibration control techniques, such as TMD and AMD, have been widely introduced into the design of high-rise buildings to reduce vibrations due to wind and earthquakes. Although these systems are capable of attenuating vibrations against low-level input such as wind and weak earthquakes to a fairly perceptible r. m. s. vibration level, they can not function well for destructive earthquakes because these kinds of systems have their own design limitations mainly on the size of the mass utilized on the tops of buildings and on the stroke of the actuators or travel distance of the mass. A new type of multi-tuned mass damper has been developed to reduce the displacement of the primary mass by using impact forces produced by added mass. Accordingly dynamic tests using a shake table were carried out to confirm its performance. The damper was installed at the top of a 5-storey steel-framed building model of 5 400 kg in total mass. Overall mass of the system comprised from primary and added mass was 22. 4 kg and it was equivalent to 0. 47% of the first modal mass of the building. Then computer response analyses were conducted to simulate the performance of the system.

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In the previous paper, the authors proposed new characteristics of damping force of an ER damper that are expressed as a function of road profile and horizontal position of the damper on the road by piecewise linear form, and minimized the maximum acceleration of the sprung mass of a vehicle model with the ER damper. In this paper, we propose a method of multiobjective optimization that two objective functions, namely the maximum acceleration and maximum displacement of the mass of the vehicle model with the ER damper having a damping force revised for the high frequency vibration shown in the previous paper are minimized. As the result of the optimization, Pareto optimal solution is obtained using the ε-constant method, and the trade-off for the objective functions is analyzed. In addition, the optimum ER damper is compared with the optimum existing damper which the damping force is expressed as a function of piston speed of the damper.

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A structural topology optimization method based on the genetic algorithm is presented in this paper. The fitness function composed of a natural frequency is maximized by optimizing the topology of the structure. The optimum topology of the structure is determined by optimizing the placement of the finite elements in FEM analysis. In the optimum design based on the genetic algorithm, the computation burden should be decreased for practical use. This study improves the genetic operations with respect to crossover and mutation and realizes high efficiency of the calculation. Furthermore, the higher efficiency of the calculation is achieved by the model reduction in structural analysis. Effectiveness and practicability of the proposed approach are verified by optimizing the topology of the guide-arm installed in the magnetic disk device.

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Several studies have been performed on improving the stability of articulated vehicles through trailer wheel steering, but the principle on which to base the control of such steering has not yet been clarified. The authors propose a method of semitrailer wheel steering control called "Vector Follower Control", and clarify the conditions which must be satisfied to achieve this control. Then, this method is evaluated through a series of simulations. The results indicate that this method is highly effective for improving both the directional stability and the tractor's track followability of the semitrailer. In order to confirm the results of the simulations, the authors conducted the lane change test and track followability test using a scale model (scale#1/8) with controllable wheels.

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This paper proposes a new method of visual servoing for autonomous vehicles using multiple landmarks. In this method, a vedicle is controlled using the geometrical relationship of the landmark images between teaching and autonomous running. One CCD camera and two objects which exist in the surroundings as landmarks are used, and the positions of the landmarks are not necessary. Therefore, autonomous running is possible without any landmark map, target mark, or internal sensor. In this paper, the fundamental principle of this method is shown and a concrete constitution of the visual servoing system is described. Moreover, its efficiency is confirmed by examinations with a test vehicle.

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A new robust control logic for the active rear steering (ARS) system of an automobile is presented. It maintains good control performance even if the vehicle parameters and/or road condition are changed. This system makes the vehicle follow the desired dynamic model by the state feedback of both yaw rate and side silp angle. To utilize noisy yaw rate sensor and also to maintain high robust control performance, a controller with frequency-dependent gain characteristics was designed by μ synthesis. To estimate the side silp angle using a noisy sensor, a time-variant observer applying a frequency filter is introduced. Results of simulations and actual tests prove the great effect of this new ARS control.

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This paper presents a numerical method for motion control of a variable-geometry flexible beam structure. The transient response of the structure is calculated using updated nodal coordinates and internal forces, and the stiffness matrix for the beam elements in a finite element model. Using the results of various quasi-static finite element analyses, the neural-network feedforward controller learns an inverse model of the controlled flexible structure. To minimize the tracking error and to damp the vibration, the fuzzy feedback controller is combined with feedforward controller, which uses the above inverse model to estimate the sensitivity of the controlled structure. As an example, this method is applied to an arm-like flexible, lightweight beam structure which has 21 elements including two variable links, and the motion is analyzed.

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A simultaneous optimization problem of mechanical/structural elements and controller parameters has been studied. In this paper, an H^∞ simultaneous optimization problem is formulated, which is similar to the conventional H^∞ optimization. The descriptor forms are used for a controlled object and a generalized plant because the structural parameters appear naturally in these forms. Static state feedback is considered as a control law. The objective function is the H^∞ performance, which is the H^∞ norm of the closed-loop transfer function from exogenous input to controlled output. In order to obtain the solvability conditions of the formulated problem, the descriptor form representation is transformed into a state space one. The conditions can be expressed in terms of linear matrix inequalities (LMI). An iterative procedure is proposed for solving LMI by use of convex optimization.

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This paper is a study on the minute grasping force control of a two-fingered miniature gripper driven by piezoelectric bimorph cells. The system is composed of two flexible fingers and a compact force sensor attached to the tip of one finger. Control action is implemented by two piezoelectric bimorph strips placed at the base of each finger. The theoretical model of the electromechanical system is developed and applied to the study of control problem where the gripper is commanded to grasp its object with a constant force 0.01 N at a prescribed fingertip position. The PID control algorithm is introduced to drive the gripper. The system control behaviour is examined both theoretically and experimentally.

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In this paper, a new drive method for the regeneration of a system with flywheel batteries and mechanical loads is proposed. The system consists of more than two motors and their symmetric driving circuits. In order to arbitrarily accelerate the motors with mechanical loads, we exploit the energy stored in the flywheel batteries. Conversely, to arbitrarily decelerate the motors with mechanical loads, we carefully control and accelerate the motor connected to the flywheel batteries. A design of the driving circuits and a driving algorithm are proposed. Experimental results illustrate that the energy flow can be arbitrarily controlled between flywheel batteries and mechanical loads.

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In this paper we propose a model reference adaptive control strategy using output feedback. When the control system is constructed using the proposed controller, the maximum value of the output error decreases as the value of the feedback gain of the output error increases. Moreover, the proposed control system has good performance that the maximum value of the control input does not increase even if the value of feedback gain increases and that high-freqency vibrations have difficulty appearing in the control input. A control system having such properties would be very useful for controlling actual plants.

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In a previous paper, we proposed an experimental identification technique for boundary conditions of a beam. In that paper, the applicability of the technique was confirmed by numerical simulation. In this paper, the applicability is examined in practical cases. For this purpose, the technique is applied to an actual beam. The responses obtained using the identified results are compared with those obtained experimentally. It is found that the technique reproduces the actual responses well. In this way the applicability of the technique is confirmed. Finally, all example of application of the technique to a rolling bearing is shown.

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We present research results on feedback active noise control schemes using H^∞ control theory in a one-dimensional duct. In this study, based on the model identified using frequency-domain test data, a H^∞ controller is designed by formulating the control specifications into a mixed sensitivity problem. Simulations and experiments are carried out using the designed H^∞ controller. The experimental results are in good agreement with the simulation results, and at the location of the microphone, noise reductions of about 7 dB are achieved at the 3rd-8th resonant frequencies.

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A strange noise occurs around the anchor of the bridge when catwalk ropes of the Akashi Kaikyo Bridge collide with each other in a strong wind. This noise was studied using the two-vibration measuring techniques. The transfer function of vibrations, spacing δ on the rope, was measured. Peak and dip frequencies of the transfer function indicate that bending waves propagate in the catwalk rope. Since the propagation speed of the bending wave varies according to frequency, higher-frequency waves travel faster than lower-frequency waves. In addition, the acoustic radiation coefficient of the rope is less efficient in the low-frequency range. Therefore, the high-frequency range is emphasised. This is the mechanism of noise generation.

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A technique based on the principle of acoustic reciprocity has been developed for measuring acoustic transfer functions for sound radiation from vibrating components of vehicles. With this technique, frequency response functions of sound pressure on the surfaces of components are measured with loudspeakers installed at receiver points. In this paper we will first explain the acoustic reciprocity principle for coupled structural-acoustic systems, realization of a simple sound source, measurement of effective volume velocity of a sound source and signal processing. Empirical examples will then be given of applications of this technique to the analysis of sound radiation from the engine of a passenger car. The results indicate that the reciprocity technique is often more accurate than the conventional acoustic excitation method which uses loudspeakers installed on the surfaces of components.

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The cochlea is a principal sensory organ of the mammalian auditory system. High sensitivity and sharp tuning of a healthy cochlea as well as otoacoustic emissions (OAEs) have been discovered. In a recent study, an outer hair cell (OHC) isolated in vitro was shown to be motile. This motility is speculated to contribute to the cochlear function and OAEs. Various investigations have been carried out concerning this function and OAEs. However, the mechanism for generation of OAEs is still unclear. Therefore, in this study, using a one-dimensional model of the cochlea, which was established in our previous paper, and comparing the numerical results with the experimental data, an attempt is made to clarify the mechanism for generation of transiently evoked OAEs (TEOAEs).

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An accurate, high-efficiency light sectioning technique is required for the measurement of 3-D surface shapes. To obtain 3-D information, a mechanical scanning construction or multislit lighting is necessary. However, the former requires a long measurement time for the scanning procedure and the latter a complex calculation to separate the overlapped lines. In addition, measurement of a specular surface is often limited because of the specular reflection and/or multiple reflection on the target surface. To realize high-speed 3-D measurement, we propose a new sensing system utilizing a pulse operation laser diode (LD). Pulse operation of LD increased light intensity, resulting in increase of the SN ratio. The need for mechanical scanning was eliminated by employing time-sharing pulse operation of multiple LDs that was synchronous with CCD detection. In the present system, a pair of parallel lightsheets was employed to confirm this idea. A correction scheme for multiple reflection was also proposed. Using this system, 3-D shape of a soldering surface was measured.

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Both repulsive and attractive forces caused by the pinning state where a magnetic field is trapped in a superconductor are capable of noncontact steady support of an object in all directions. This paper describes the characteristics of the levitation forces, the force relaxation caused by the flux creep and the bearing loss under high rotational speed on a disc-type superconducting bearing at 77K, as well as the rotational characteristics of the pinning-type superconducting radial bearings. The bearing consists of Y₁Ba₂Cu₃O_x(YBCO) oxide superconductors fabricated by the QMG (quench-melt-growth) process and rare-earth permanent magnets. The rotor with permanent magnets supported by the pinning force in the superconductor can be safely operated under high rotational speed.

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A newly developed six-axis precise positioning system incorporating a surface motor (SFM) is presented and its operational principle, mechanical and control system design, and some experimental results are described. The positioning system is levitated on a base plate by three air-bearing pads ; being driven by simultaneous operation of three linear motors in the x-, y-, and θ_z-directions and piezo elements in the z-, θ_x-, and θ_y-directions. A new design concept is discussed that incorporates (i) a mechanical design relative to the drive and sensing point locations which enables stabilization of the x-, y-, and θ_z-directional planar motions and (ii) a six-axis position control method using a force disturbance observer for achieving high positioning resolution as well as quick response capabilities. Evaluation of experimental results indicates that the system is capable of achieving six-axis precise motion with 10-20 nm resolution in the x- and y-directions and that the proposed control strategy enables better positioning characteristics than the conventional PID-based servo control method.

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We present a high-speed track seeking technique based on two-degree-of-freedom (2DOF)control. 2DOF control, which simultaneously uses feedback and feed-forward control, specifies loop performance and response performance independently. Therefore, conventional mode-switching from velocity control to positioning control becomes unnecessary. Focusing on how to effectively use a voice coil motor (VCM), that is, a head actuator, for fast track seeking, a new reference model is also proposed. In this 2DOF control system, a reference model plays an important role in shortening of seek times. Considering the VCM dynamics, this reference model generates a reference trajectory allowing high-speed movement and fast settling to target tracks. Experimental results using a typical hard disk drive indicated the validity of the proposed method, especially for short stroke seeks.

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A controller for the manipulator of an underwater robot must position it speedily and accurately, even when it grips an unknown body. In addition, an underwater manipulator system is nonlinear. Therefore, a sliding mode control is suitable, because it has robustness and is able to deal with nonlinear systems. However, chatter due to switching delay of input is a serious problem. In this study, a discrete-time sliding mode control, which is able to suppress the chatter, is applied to the positioning controller of a flexible rotating arm in water driven by a thruster. However, it is found that stable equivalent control cannot be obtained. Therefore a positioning controller is developed using a combination of discrete-time sliding mode control and optimal control. The hyperplane is defined by the feedback gain of optimal control, and the equivalent control is replaced by the optimal control. Then, positioning experiments are carrried out. The performance of the developed controller is confirmed.

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A 6-degrees-of-freedom (DOF) motion system using a new paralled link mechanism is developed for the purpose of evaluating human motion sensation. This motion system is made up of three five-bar link mechanisms, each of which has 2-DOF and is driven by AC servo motors. Therefore, this system is very small, but its working area is larger and its response is better than those of the hydraulic Stewart platform. Furthermore, I have developed a high-speed parallel signal processing controller for motion control and a new 6-DOF acceleration sensing system based on the parallel sensing concept. Combining the new motion and sensory system with a multi-video system, we have constructed a new analytical system for evaluating a wide bandwidth of motion sensation in riding such vehicles such as automobile or airplanes.

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A method for time optimal collision free trajectory planning problem is proposed. In this paper, the dynamics of manipulator and obstacles in workspace are considered. This optimal trajectory planning problem is very difficult and complicated one because of non-linearity of manipulator dynamics and existence of obstacles. Generally, it results in a multimodal optimization problem. The proposed method is basically an iteratively improving one based on a gradient method. Firstly, two global methods (a genetic algorithm and an exact cell decomposition method ) are used to search multiple initial feasible spatial paths for the gradient method. Next, the gradient method searches time optimal solution locally with the multiple initial feasible solutions. Simulation results show that this approach is effective to the time optimal collision free trajectory planning problem.

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We describe a new approach to a nonlinear block stacking problem in a traditional AI field. In our problem setting, we see the problem as one of planning in a dynamic environment and attempt to solve it in a distributed manner. Each block is considered as an autonomous agent having sensors and effectors and capable of moving in the block world. As the behaviors of the agents change the environment, the agents are required to resolve conflict among other agents. In our approach, motions of the agents are controlled using a recurrent neural network (RNN). Based on sensory inputs to the RNN, the agents select their alternative actions. The RNN implemented in each agent is trained through evolutionary learning and both the structure and connection weights of the network are altered appropriately using two kinds of mutations according to the degree of success of the planning. Actions of agents are triggered by activation levels which are calculated on the basis of received signals from other agents and the environment. Based on the proposed methodology, computational experiments are carried out and some experimental results are shown.

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This paper deals with a micro mobile robot in water that acquires swimming ability through unsupervised learning. The robot utilizes PZT [Pb (Zr, Ti) O₃] as an actuator and moves fins for propulsion. The motion of a fin is subject to dynamics, thus, acquisition of swimming ability indicates creation of appropriate input to the PZT. We used an unsupervised self-tuning RBF Fuzzy Neuro based on the radial basis function with an insensible region to generate the input signals. The method of learning is based on a genetic algorithm (GA). In other words, a string in the GA stands for a fuzzy system. We show the effectiveness of the method through simulations. We stress that the leaning method does not require any dynamic or physical parameters of the robot. Therefore, the method is effective for leaning in a complicated dynamic system and an unknown environment.

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A skill learning method is proposed in this paper. For a Dual-peg-in-hole problem, it is very difficult to analyze force and contact status. To extract the human skill of this kind of work, we record the force/torque data, sequence data, and psychological data by observing human work. Since human performance is inherently stochastic, we use a Hidden Markov Model (HMM) to represent these characteristics. By trainning the HMM using human data, we obtain a reasonable sequence of Dual-peg-in-hole work and the threshold of contact-state transition. We represent the human skill as a set of simple production rules that can easily be adopted into an actual manipulator system. This method is used in the assembly of self-organizing manipulator cells. The simulations and experiments illustrate the effectiveness of the algorithm.

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A trajectory generation method based on an artificial potential field approach may be useful for real-time motion planning of a moving robot, since it is effective and computationally much less expensive than other methods using global information on a task space. In the present paper, we argue that dynamic behavior of a generated trajectory and control of the direction of motion of the moving robot should be taken into account within the framework of the artificial potential field approach for practical use, and propose a new method using active deformation of the artificial potential field. The method can regulate movement time from an initial position to a goal, and velocity profile of the trajectory as well as the position and the direction of motion of the robot by changing the orientation and shape of the artificial potential ellipse.

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We have been aiming at developing a robotic aid for disabled persons who need assistance in moving from a bed or a chair. An MH actuator shows spring like behavior with adjustable stiffness realized by varying pressure in a bellows. The antagonistic MH actuator system using two MH actuators arranged in opposition to each other was developed to realize compliant joint motion of a robotic aid. The joint stiffness of the antagonistic MH actuator was varied in proportion to the sum of internal pressures of the two MH actuators. A robot arm having two degrees of freedom driven by antagonistic MH actuators was designed to test its behavior in contact with a human body. When the robot arm was inserted between a bed mat and a unilateral lower extremity of a human lying in a supine posture, the reaction force from the bed and the lower extremity were measured. From the experimental results, in the case of high joint compliance, the reaction forces from the body were lower than in the case of low joint compliance (nearly 0 rad N^-1m^-1). It was concluded that a robot arm that is to be used for handling a human body must have variable compliance joints, and that the antagonistic MH actuator was appropriate for use in robotic aids that handle the human body.

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The restriction of the range of motion (ROM) of joints is one of the major causes contributing to walking disabilities as well as neural dysfunction and decreased muscle force. This study was designed to develop a biomechanical model of walking consisting of both the neural and muscunloskeletal systems, and to simulate the characteristics of walking disability due to restriction of the ROM of hip and knee joints. The neural and muscunloskeletal functions in the present model were represented by neural oscillators and a two-dimensional five-link model, respectively. The walking patterns produced under the non restricted ROM of the joints were similar to those obtained from normal individuals. The simulation with the restricted ROM of joints demonstrated more unstable walking with increasing severity of the joint impairments as well as with increasing walking velocity. Even if the ROM of hip and/or knee joints of this model was restricted, both stride length and cadence during stable walking were within the range determined from normal individuals. However, the vertical acceleration of the body center of gravity was considerably greater during walking with the restricted joints compared with free joint movement. These characteristics obtained from the simulation were very similar to those of disabled walking produced experimentally by healthy subjects whose lower limb joints were restricted by orthotic devices. It is considered that the present biomechanical model/simulation is a useful way to identify a single cause such as joint contracture from the multiple and complex impairments associated with walking disabilities and to assess the degree of the disabilities due to the specified impairment.

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Ambulatory capability results in overall improvement of ADL (Ability of Daily Life). Technically aiding the walking ability of the elderly is the basic solution for an elderly society. A walk training system for the elderly is now under development, It consists of two parts: training environment and patient support apparatus. The training environment consists of two elements: treadmill(walk plain) and display. The patient stands on endless belts (one belt each foot) of the walk plain, and commences to walk. Endless belts are driven by the method of active impedance control. The patient support element is a 2 degree-of-freedom manipulator. The force of the manipulator is defined by the displacement of the patient from the datum point, in order to keep posture of the patient or to support the patient's weight. The walk training system was tested on 30 subjects (max. age is 94). Its basic function was found to be successful in improving the ADL of the subjects.

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The rarefaction-modified Reynolds equation considering porosity of thin liquid lubricant film coated over a sliding surface was extended to solve dynamic problems. Applying the perturbation method, a calculation procedure based on the FEM method for obtaining stiffness and damping of gas lubricating films over a permeable liquid lubricant was formulated. Calculations were then performed for specified flying head sliders. Effects of the permeability and the porosity correction coefficient which serve to increase molecular mean free path were presented, focusing on landing on/off characteristics and the stiffness and damping versus vibration frequency characteristics. It was found that the permeability and the porosity correction coefficient increasingly affect landing on/off characteristics in the higher velocity region, and that permeability is effective to increase damping of lubricating film.

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In the 1st and 2nd reports, it was shown that a newly developed hydrostatic bearing with pressurized oil supplied through an inner shaft is suitable as a stern bearing for a contra-rotating propeller system. This paper presents a theoretical analysis of coupled shaft alignment and bearing performance for a CRP system, taking account of propeller forces, and measurement results of bearing performance of a full-scale ship, which is the world's first merchant ship to be equipped with contra-rotating propellers. It is confirmed that measured results of oil film thickness and inclination angle between inner shaft and stern bearing agree well with predicted ones.

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The present paper proposes a method of determining the displacements of planar link mechanisms with clearances under specified load conditions. A virtual mechanism, of which the contact positions between pairing elements are assumed as pairing points without clearances, is introduced, and the geometric and static conditions which each link and joint should satisfy individually are considerd separately. Then an algorithm, in which a systematic method of analysis for mechanisms without clearances is iteratively utilized, is prposed for searching the appropriate contact positions at each pair. The contact loss and the multiple solutions of the contact positions of pairs are also considered in the analysis. The effectiveness of the method is confirmed through an illustrative example of a four-bar mechanism.

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A robotic manipulator usually operates its end effector on a front face of the object. However, sometimes the end effector of the manipulator has to go round behind obstacles to carry out painting, assembling or welding. Evaluations of the go-round performances are required especially in developing a new manipulator mechanism whose degrees of freedom are limited. This paper proposes two methods for evaluating the reaching ability of the end effecter compared with the room required for moving the manipulator body. The first method is for an orthogonal reach direction to the robot-object line. Another method is for a turn-back reach direction to it. These methods are applied to serial types of geared link mechanisms which have one bending degree of freedom and of which root links are driven not rotationally but parallely. The link lengths and the gear ratios which enable optimum performance are investigated.

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The purpose of this paper is to present the development of effective antiloosening screw fasteners which are very resistant to loosening without sacrificing any of the advantageous features of conventional screw fasteners. Two factors cause loosening of screw fasteners. One is relative slip between the bolt and the nut screw thread. The other is relative slip between the bearing surface of the bolt or nut and the surface of fastened material. Prevention of loosening could be realized if either one of these causes were eliminated. In order to eliminate relative thread slip, we developed a new screw called the "step-lock bolt". This bolt has 8 steps in one helical circumference. Bolts of size M8 with the new shape were made by the rolling process. The performance of the bolts fastened with conventional nuts was examined and the efficacy in preventing loosening was discussed. The results show that a step-lock bolt fastened with a force of 12kN or higher does not loosen.

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The objective of this paper is to explain the mechanism of the occurrence of self-excited vibration observed in roller mills. In the first report, it is determined that the vibration of a roller mill is a kind of stick-slip motion, and the powder has negative-damping properties relative to velocity. We assume that these negative-damping properties cause the vibration of the mill. Thus, by this assumption, we model a three-degrees-of-freedom vibration system with such friction characteristics for a simplified test apparatus and propose the corresponding equations of motion. The fluctuations similar to the experimental results are obtained by numerical integration of them. Moreover, we note that the negative-damping properties cause the fluctuation in rotational motion of the roller.

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Limiting load for scuffing was investigated using spur gears which were case-hardened and ground. The load was stepped up according to the load stages which were determined in accordance with the FZG spur gear test in our experiments up to the load stage where scuffing failure occures. Before and after running the test gears, the degree of wear was measured with a balance. At first the running time of test gears at each load was varied greatly and we found that the running time at each load stage has no influence on the limiting load for scuffing. For our experiments four kinds of base oil viscosity were used. As antiscuffing additive EP and ZDTP additives at various concentrations were used. Influence of lubricating oil viscosity and concentration of EP and ZDTP additive on limiting load for scuffing and specific wear were investigated and the results were summarized. Furthermore the integral temperature of the tooth surface according to the ISO proposal was illustrated and discussed.

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The tooth bearing in a bevel gear varies sensitively with assembly errors, shaft angle errors and deviation of apex, and tooth end contact is easily induced. Therefore, it is important for strength design to know the load distribution on a line of contact and the tooth root stress of a bevel gear which contains assembly errors. In this paper, the load distribution and the tooth root stress distribution are calculated. Furthermore, the influence of assembly errors on bevel gears is clarified.

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The tooth bearing in a bevel gear is sensitive to with assembly errors, shaft angle errors and deviation of apex, and the tooth end contact is easily induced. Therefore, it is important for strength design to know the load distribution on a line of contact and the tooth root stress of the bevel gear which is subjected to assembly errors and shaft angle error. In a previous report, the load distribution and the tooth root stress distribution with assembly errors in the direction of driven gear shaft and in the direction perpendicular to both of driving and driven gear shaft were calculated. In this paper, the load distribution and the tooth root stress distribution with assembly error in the direction of driving gear shaft and shaft angle error are calculated. Furthermore, the influence of assembly error and shaft angle error on bevel gear is clarified.

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In the case of parallel axis gears (for instance spur gears, helical gears), it is clear that rotational vibrations of gears are mainly transmitted to the gear housing through gear shafts and bearings. Therefore it is necessary to improve them in order to reduce vibration of the gear housing. On the other hand, spiral bevel gears have been widely used as low noise gears among bevel gears. However, in the case of spiral bevel gears, there have been few studies dealing with dynamic behavior under running conditions, and little work has been done to clarify the mechanism of vibration of the gears and housing. Therefore it is necessary to clarify characteristics of vibration of spiral bevel gears to reduce vibrations of the gear housing. Thus, in this study, rotational acceleration of Oerilkon-type spiral bevel gears and vertical acceleration of the housing are measured under various conditions. At the same time, the root stresses are observed in order to assess the meshing condition of the gears. We conclude that it is important to estimate the rotational acceleration of geas in order to reduce vibration of the gear housing. It is found that rotational vibration of gears is related to the real contact ratio. In addition, we propose use of the free vibration to model the rotational motion of spiral bevel gears by means of equivalent spur gears. Results calculated using this model are in good agreement with experimental ones.

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