Very lightweight sliding parts, which require wear rates that are almost zero, are beginning to be used in magnetic recording devices and micro-mechanical systems. The wear of sliding surfaces subjected to very light loads is primarily due to surface interaction force rather than to load or weight. If we can control the surface interaction force, we can drastically decrease the wear rate under very light loads. The ultimate goal of micro-tribology is to create practical zero-wear devices. Microtribological evaluations of solid surfaces and lubricants have begun to employ new tools such as the scanning probe microscope.

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In this paper, the development of a modal sensitivity analysis method is described for a system with repeated eigenvalues. It is shown that the new algorithm proposed by the authors has much better computational accuracy than the method proposed by S. H. Chen and H. H. Pan, and this method is simpler in terms of calculations than Ojalvo's and Dailey's methods, which was presented recently. The new method can also be extended to a coupled acoustic-structural system with repeated eigenvalues, and thus can be applied to vibration-noise reduction problems.

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A new mode-superposition technique with higher accuracy and efficiency was proposed by the authors in Ref. (1). This paper applies the technique to eigenmode sensitivity analysis for a structural system and a coupled acoustic-structural system. It will be shown that the use of a new mode-superposition technique greatly improves the convergency of a modal sensitivity analysis, and makes it possible to calculate the sensitivity with better efficiency than Fox and Kapoor's modal method and Wang's modified modal method, and also with better efficiency than Nelson's method. The theoretical results are verified through application of the method to a box structure and a practical vehicle interior noise problem.

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In this paper we propose a method by which the calculation of the natural frequencies of bending vibration of a straight rod with an additional mass and subjected to axial compression, and the estimation of the axial force based on the natural frequency is simplified. This method is an extension of Rayleigh's method. The effect of the additional mass on the mode shapes is first studied using a rigorous analysis. The deflections of the rod assumed in the calculation are modified principal mode shapes of bending vibration of a rod with neither additional mass nor axial force. Comparisons between calculated results and experimental results show that if the additional mass is lighter than about half the mass of the rod, natural frequencies up to the third mode are obtained with good accuracy, and that estimation of the axial force can be made with errors of less than ten percent.

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The finite element method is used to study the effects of rotating the plate principal axes with respect to the geometric axes, orthotropicity parameter, E₁/E₂, and shear deformation on the vibration and flutter characteristics of anisotropic plates. The vibration and flutter of anisotropic square plates, under a variety of boundary conditions are analyzed using the triangular finite element used in the previous paper. This element incorporates shear deformation according to Mindlin's theory.

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When calculating the resonant response of bladed turbine disks, it has been expedient to assume that all blades on a given disk are identical. This leads to the prediction that all blades experience the same amplitude of displacement and stress when excited by forces harmonically related to the rotor speed. However, it has been shown experimentally that significant variations in these amplitudes occur for different blades on the same disk. These variations arise due to the effects of mistuning, which refers to small differences in blade characteristics. In this paper, effects of mistuning for free-standing blades and integral shroud blades are studied by means of Monte Carlo simulation and sensitivity analysis. It is found that weakly coupled systems with low damping are very sensitive to mistuning. Also, the validity of the lumped model used in this paper is examined by comparing the calculated results with experimental data.

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In this paper the dynamic behavior of a rotor with variable parameters and small nonlinearity is analyzed. Besides the linear damping, rigidity and gyroscopic force that are time-dependent, some nonlinear forces exist. They cause self-excited vibrations of the rotor. The vibration problem is solved analytically as well as numerically. A new procedure based on the Krylov-Bogolubov method is developed for solving a differential equation with a complex deflection function, time variable parameters and small nonlinearity. The asymptotic analytical solutions are in good agreement with the numerical results. For the rotor with variable parameters, the stability of th pure rotational motion is also analyzed. The direct Lyapunov stability and instability theorems are applied. The methods developed in this paper are applied to three special cases : 1. the mass of the rotor is time-dependent, 2. a linear damping force is applied. 3. a linear gyroscopic or a "cross coupling damping" force is applied.

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Distributed tensioning in a wide range is usually applied to a tipped saw. This distributed tensioning effect was studied analytically and experimentally using normal and tensioned disks. The following conclusions were reached. (1) Residual stress due to tensioning was measured. Residual stress distribution could be calculated in terms of Gaussian-type isotropic additional stress. (2) Natural frequency change due to tensioning treatment was calculated by means of the energy method and was in good agreement with measured frequencies. (3) A backward-traveling wave of the two-nodal-diameter mode determined the critical rotating speed, and the rotating speed domain above this critical point was unstable. This phenomenon was confirmed by transfer function measurement. (4) The tensioning effect increased natural frequencies and expanded the stable domain.

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In this paper, nonlinear imbalance response and forced damped natural frequency are calculated for horizontal Jeffcott rotors supported by oil film damper bearings having no centering springs. The former calculation reveals that there exists four types of synchronous imbalance responses. In one of the four types, the vibration amplitide can become infinitely large, and this dangerous type of vibration can appear easily with increasing imbalance. The latter calculation reveals that the stability margin, which is determined from the calculated complex eigenvalues, greatly depends on the type of synchronous response that happens to appear.

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The phenomena of 'stick-slip' oscillation in a hydraulic driving system are studied both experimentally and analytically. The system consists of a table lying on a rectilinear sliding surface, an actuator cylinder, a 4-way servovalve, a relief valve and an oil pump. In our experiment, certain friction-velocity curves are observed to exhibit hysteresis with increasing- and decreasing-velocity motion of the table. Here and in the theoretical analysis, the acceleration and deceleration portions of the friction-velocity curves are assumed to be distinct. The variations of friction are modeled as follows. (1) Kinetic friction varies with applied electric current and sliding velocity. (2) Static friction varies with electric current passing through the servovalve and the sliding velocity. The principal experimental variables are lubricant viscosity and the table mass. Their influences on the characteristics of 'stick-slip' oscillation are studied.

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This paper presents experimental studies on vibration of an axisymmetric body in a cavitating leakage flow. The experimental passage is a narrow annular parallel passage. The effects on the characteristics of vibration and the flow pattern in the passage were evaluated by changing the width of the passage, the downstream pressure and other conditions. From the experimental results, the following conclusions were obtained. When the narrow passage becomes choked and the cavitation bubbles are concentrated around the wake, a divergent passage is formed by the columniform bubbles, and self-excited vibration due to the negative damping occurs in the system. Under such conditions, the self-excited vibration becomes intense when the cavitation number is about 0.2.

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This paper deals with the synthesis of a single-input/single-output ripple-free deadbeat tracking control system using a two-degree-of-freedom compensator scheme. The proposed system can simultaneously follow a reference input and eliminate the effects of a disturbance with no ripple in a finite time. Both the reference input and the disturbance are general types of those generated by linear time-invariant systems. Moreover, the ripple-free deadbeat system with optimal transient performance is proposed, which can make as moderate as possible the transient responses for both the reference input and the disturbance. The algorithm is based on a simple iterative operation with no matrix inversion.

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This paper describes a control system design method concerning feedback and feedforward control to cancel disturbance forces, for two kinds of active vibration control devices. One is the active vibration absorber (AVA) utilizing a fixed point for a civil structure such as a bridge, and the other is the active dynamic vibration absorber (ADVA) utilizing an auxiliary mass for a buildinglike structure. We have built two test rigs to simulate large structures with an AVA or an ADVA. In order to carry out fast computation, including the estimation of disturbances, we have used a digital signal processor (DSP). In conclusion, we found that the disturbance forces are perfectly cancelled and the output zeroing is actually realized when the disturbance frequency is exactly equivalent to the design frequency of the observer. We have confirmed that the proposed disturbance cancellation control is very useful for active vibration control.

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An estimation method to detect the human reasoning state in machine operation is discussed in terms of a fuzzy linear regression model. Simple experiments of human operation using a computer display show that the change in the human internal state during the reasoning in the operation can be reflected in the system parameters of the fuzzy linear regression model. This model is constructed using fundamental operational data, and fuzziness parameters are calculated by means of traditional linear programming approaches. The characteristics of the human reasoning state are represented by fuzziness parameters, and the advantage of the proposed approach to human reliability is demonstrated by the example of vehicle operation.

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The fuzzy "sliding mode" control method is proposed in this paper for the design of a closed-loop fuel-injection system. A fuzzy logic control using variable structure system is combined with current oxygen sensors to maintain the stoichiometric air-to-fuel ratio. The fuzzy cell technique is also proposed to implement the designed controller on nonfuzzy processors. The proposed method offers good potential for the design of an engine controller since : (1) bias and large chattering errors due to the hysteresis of the oxygen sensor can be reduced by utilizing fuzzy logic control inside the boundary layer of the sliding mode ; (2) robustness and stability are analytically guaranteed by the hybrid control structure. Simulation studies based on a typical engine-only model demonstrate the usefulness of the proposed method.

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This paper is concerned with a control system design for the new type of omnidirectional AGV (automated guided vehicle) without any steering mechanisms. The system is regarded as a highly nonlinear multidimensional system with parameter uncertainties, so the conventional control techniques are not available. Here we propose a new control algorithm by combining nonlinear decoupling control with robust simple adaptive control (SAC). Both techniques were developed by one of the authors. The control system then results in single-input and single-output (SISO)control systems by the effect of decoupling control, and the control accuracy is assured by robust SAC. The effectiveness of the proposed method is confirmed through numerical simulations.

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For chassis control systems such as 4-wheel steering and active suspension, the most suitable and reasonable control is always desired to achieve better driving sensation. We discuss a theoretical analysis of the stability criteria and a performance index for a driver-vehicle (closed-loop) system. Assuming a linear preview control model of a driver in a lane change maneuver and an equivalent linear bicycle model for the vehicle, the stable and unstable zones on the u-T_p plane (u : velocity, T_p : preview time) are derived, and a typical quadratic expression for the cost function is proposed. Vehicle design parameters, the rear-wheel steering control algorithm and the driver characteristics can be discussed quantitatively in the same terms on the f_y-K plane (f_y : yawing natural frequency, K : stability factor) to determine pleasurable driving sensation or a possible safety criteria.

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In the previous paper, we developed equations of motion for analyzing the dynamic behavior of crawler-type vehicles during straight propelling on soft ground and firm ground. In this study, experiments were carried out in order to verify the validity of the simulation model. The power shovel, a typical example of a crawler-type vehicle, was used in the tests. We measured the dynamic characteristics of the ground to determine the settlement and shear with consideration of hysteresis. The results of experimental tests are in good agreement with the theoretical results. The dynamic behavior of the vehicles, as indicated by parameters such as the dynamic ground pressure, is determined.

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Automatic operation is important for the in-service inspection of nuclear power stations or the decommission of retired plants. Master & slave control will be introduced for work-robot control. It is desirable that the slave possess problem-solving capabilities. In this paper we assume that the slave incorporates the general problem solver (GPS) algorithm. In view of having solved the "monkey and banana" problem, the slave system is regarded as a reasonable alternative which incorporates the capability of problem-solving. Basically, the GPS solves a problem by reducing the difference between the initial state and goal state, and hence the performance of GPS depends on selection of the difference to be reduced. The conventional GPS is given the order of importance of the differences in advance. In this study, the GPS was improved by making use of the rules which determine the order. When several choices are available for the given difference, a fuzzified decision to determine the necessary action is made, as demonstrated in this paper.

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In an effort to improve the intelligence of a robot fitted with tactile sensors, we have developed a tactile sensor array which detects the distribution of three applied force vector components. Here, we introduce formulas for basic tactile information such as applied force and moment, centroid of distributed pressure, contact pattern, contact state and mechanical properties, obtained through contact of the tactile sensor with an object. We then produce a tactile expert system which is capable of recognizing the material, shape and stability of the object by means of a reasonably combining the basic tactile information. Recognition experiments show that the system can infer the material and shape of seven objects and that it can control the hand in response to the different kinds of grasping instability.

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This paper deals with a new type of dynamically mobile robot developed by modeling a gibbon, which is a long-armed ape that moves from branch to branch swinging its body like a pendulum. Since it makes use of gravity to swing, it does not use much force to move. The manner of moving like a gibbon is called brachiation. In this paper, we present a new method to control a brachiation robot and describe the results of simulations using a two-link-model robot. The main subject of this study is how to control it naturally and dynamically while taking advantage of gravity. First, we introduce a heuristic approach in which locomotive forces are generated by the robot itself after familiarizing repetitions. Next, we show that interpolation utilizing the spline function between heuristically generated driving inputs creates new forces that can accommodate the robot to previously unexperienced conditions. We also show that trajectory feedback control based on feedforward control achieves natural and dynamical locomotion of the brachiation robot.

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A practical compliance control method has been developed for a robot manipulator. The developed method has the following practical features. 1) The response of position control is not reduced, although the compliance is set high, when the manipulator hand is not constrained by its environment. 2) Easy and continuous change among compliance, force and position controls is possible. 3) The reference signals to joints of a manipulator are rate signals. In this paper, the compliance control equation which satisfies these features simultaneously was applied to a one-degree-of-freedom model of a manipulator in consideration of its transmission stiffness. As a result, the propriety of the control equation has been confirmed through analysis and experiments.

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We have studied the "cellular robotic system (CEBOT), " which consists of many kinds of units called "cells." CEBOT is required to be able to carry out many sorts of tasks under various surroundings. However, it is impossible for CEBOT to install all sorts of the task execution procedures. Then CEBOT should be able to generate task execution procedures for a new task by reconfigurating itself. In this paper, we propose a new kind of distributed intelligence system which is based on the concept of CEBOT. This proposed intelligence system has the abilities of learning, reasoning, and self-organizing. Similar to the hardware structure of CEBOT, this system consists of various kinds of intelligence units called "knowledge cells." By using the knowledge cells and the proposed algorithms, the system which can generate task procedures is realized. Some simulations are also shown for demonstrating the self-organization and self-evolution abilities of the distributed intelligence system.

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In the previous report, the mechanism of a wall-inspection robot which is capable of moving in a weak wind on a vertical wall was investigated. For emergency use of a wall-climbing robot, such as in rescue, and fire-fighting, the robot must be able to move in strong and turbulent winds at any time. Therefore, the control system for large wind load is important. A combined control system consisting of a thrust force controller, a frictional force augmentor and a damper is used, and its performance is estimated by a computer simulation technique. The safety of the robot is ascertained for an actual turbulent and strong wind gust.

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In a space environment, owing to recent active developments, there is an increasing number of cases in which it is necessary to quickly move and manipulate objects with a large moment of inertia. Therefore, it is desirable to develop more powerful and lightweight actuators. Presently, electric motors are used in this area, however, their capability is not sufficient from the viewpoint of the output torque-inertia ratio. The actuator proposed and developed here for hydraulic control in space is called the flexible hydraulic actuator (FHA). The actuator consists of an oilproof rubber core tube with a cover of braided durable string cords (aramid fibers). With sufficient increase of the internal pressure, the FHA contracts in the axial direction by a maximum of about 30% of the full effective length, and its output force in the axial direction is 1500 N at maximum (3 MPa of internal pressure) and the weight is 0.3 kgf. The main features of the FHA are that it needs no lubrication and has no leakage. The precise mathematical model of the FHA in static and dynamic behavior is derived and compared with experiments. The actuator with loads is investigated experimentally. It is also ascertained that the FHA responds sufficiently quickly.

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An oil film formed in a bearing clearance is experimentally investigated to explicate the mechanism of lubrication in porous journal bearings. To visualize the oil film, a porous bronze bearing impregnated with a fluorescent-dyed oil is used for the test bearing, and the oil film is rendered visible by a pair of ultraviolet lamps. It is observed that the oil film is formed in the loaded part of the bearing and, in particular, it extends over a wide range for the relatively small static load and high oil-feed pressure. However, even under hydrodynamic lubrication conditions, the angular extent of the oil film for the porous journal bearing is significantly small as compared to that for the solid journal bearing. This suggests that the previous postulate for the solid journal bearings, i. e., the half-film condition known as the Gumbel or half-Sommerfeld condition, is not applicable to the theoretical analysis of the porous journal bearings, unless an unlimited amount of oil is supplied to the bearing gap through the oil-feed hole.

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he influence of dynamic fluid reaction forces and moments of a long annular seal on the stability of fluid machinery was investigated. The stability analysis was carried out by using a submerged motor pump in a circulation boiler, in order to explain the effect of the long seal. In the stability analysis, the individual contributions of the fluid forces and moments due to rotor conical and cylindrical whirl movements were evaluated according to logarithmic decrements. As a result, the individual contributions depend on the mode shapes of the vibration. Fluid forces acting on the long seal due to conical and cylindrical whirl movements should not be ignored because they play an important role in the stability.

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This paper deals with determination of whether protoplasts are alive or not. The protoplasts are plant cells which are removed cell walls, and have been used for cell fusion to generate new species of plants. Cell fusion uses living protoplasts, and therefore, a method of life or death determination for protoplasts is necessary. FDA (fluorescein diacetate) has been used for this purpose. However, FDA has not been applied for cell fusion because it is toxic to protoplasts. In this Paper, we propose a new harmless method for the above determination using the image processing technique and an artificial neural network. The proposed method measures shape and colors of protoplasts using image processing for sensory information. The neural network determines whether protoplasts are living or not based on the sensory information. Experiments were performed in order to show the effectiveness of the proposed method. As the result, the proposed method is found to be able to recognize states of protoplasts with an accuracy of 85 percent. This method is promising for determining life or death of protoplasts in cell fusion, instead of FDA.

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Most commuter trains in large cities of Japan are loaded to their full capacity in the morning rush hour. Consequently, it takes time for many passengers to get on and off at major stations, and the trains are often delayed. Although the construction and performance of commuter train doors is considered to have a great influence on the ease of getting on and off, a method for quantitatively evaluating the relationship between them has not yet been established. The authors proposed a new method for evaluating the above relationship, and obtained a satisfactory result in practical application of the method

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Based on the present investigation, a computer-aided thread grinding method is proposed for generating helicoids without the form dressing process, in which a standard-shaped grinding wheel independent of the final helicoid is used. The method involves a simple conical or plain wheel, without limitations on diameter or base angle. With a five-axis control system, the wheel axis is set three-dimensionally at the computed optimum angle of inclination comprising the tilt and swivel angle components of the planned helicoid and wheel. The optimum angle of inclination is deter-mined through simulation of the grinding process and an investigation of the optimum angle of inclination that will give the minimum geometrical error. Both the approximate ideal screw helicoids and the approximate advanced-chased helicoids are developed more accurately than the conventionally milled helicoids.

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We investigate the use of a new sensor device for detection of acoustic emission (AE) through fluid, for a drilling machine. Within the industry there has always been the need for a practical application of the AE sensor through fluid to detect the cutting-process-related signals from the tool side. A mounting apparatus which enables the sensor to be fixed close to the rotating cutting tool has been developed to meet this need. Thus, there is now a more practical method for detecting the tool breakage and tool wear of twist drills. Judgment of tool life by a quantitative method using the ratio of the event count to oscillation count per unit time was carried out very accurately. From our experiments, the evaluation method for quantifying tool life using the ratio of the event count to oscillation count was found to be effective.

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