This article presents a review on the application of the fractional calculus to viscoelasticity. There are several methods to treat viscoelasticity of viscoelastic materials. One such method is to use the fractional derivative model for describing the constitutive relation of the materials. The application of the fractional operator in this field, the Riemann-Liouville's fractional operator is emphasized among several definitions of the fractional operator. The survey suggests that the viscoelastic constitutive models incorporating with the fractional calculus have been well established for fairly wide range of viscoelastic materials and the advantages of adopting the fractional calculus in viscoelasticity are that the constitutive relation of some viscoelastic materials can be described accurately by the fractional calculus model with a few experimental parameters, and that the fractional calculus approach can lead to well-posed problems even when incorporated into the finite element formulation.

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We propose to apply dampers using electrorheological(ER)fluid for suspensions of ambulances, and present an optimization method of the ER dampers for reducing jolts experienced by patients when ambulances pass over speed humps which have been built on roads as a means of reducing the speed of vehicles. It seems that the large jolts affect ambulances that rapidly arrive at a scene of an accident and transport patients to hospitals, because such jolts force the drivers to pass over speed humps at lower speeds than normal ones. As a result of the optimization of the ER dampers, the optimum damping force of each of the front and rear dampers is obtained and the jolts are reduced. The maximum acceleration imposed on the patient obtained in this study is compared with the one obtained by the optimization of suspensions for a vibration-isolation bed in a previous investigation.

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Cover gas is constantly supplied to a main tank the bottom of which is connected to that of a subtank. The water levels in the tanks oscillate alternately until the free surface in the main tank pushed by the gas reaches the bottom end of a vertical release pipe. Then the gas is ejected from the main tank, resulting in a sudden surface rise and plugging of the pipe inlet. The cover gas pressure increases again, thus, gas ejection occurs intermittently. The behavior of the oscillation system can be expressed by a set of linear equations that are properly selected according to the water surface position. The calculated interval between the ejections exhibits chaotic features : a simple return map of the disorderly fluctuating interval and oversensitiveness to the initial condition. The effect of superimposed random noise is examined.

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This paper reports on the study of chaotic behavior of nonlinear vibration systems with stochastic excitation. Previous studies examining mechanical chaotic vibrations have mainly focused on their deterministic properties even if the target system contains stochastic elements which are sometimes unavoidable in experimental situations. In view of this, this paper investigates random vibrations arising in nonlinear stochastic systems, which the authors call SCB(stochastic chaotic behavior). SCB has negative largest Liapunov exponents while it behaves similarly to deterministic chaos, exhibiting the expanding and folding process of chaos. This feature of SCB is in good agreement with that of a experimental chaotic behavior observed in our experiments and implies that the physical chaotic behavior may not have positive largest Liapunov exponents even though it behaves chaotically. These kinds of chaotic properties of SCB and experimental chaos can be characterized by the probability density function of local expansion rates.

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A bounded sliding-mode controller is developed for a class of multi-input bilinear systems. The sliding vector design is based on the conventional pole-assignment method for linear time-invariant systems. Three conditions are required for the assigned eigenvalues when applying the pole-assignment method. A potential reaching-and-sliding region and a stable sliding region are determined around the origin, which is shown to be locally asymptotically stable. Numeric simulation results are used to demonstrate the success of the proposed bounded sliding-mode controller.

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Adaptive feedforward control, self-organizing fuzzy control and proportional control are comparatively implemented to a 3-axial electrohydraulic control system. Its typical implementations include 3-axial vibrating system and space-tracking system. Although parameters of this system are time-variant and space dependent, adaptive feedforward control and self-organizing fuzzy control have the capabilities of on-line modifying the control law, and they have similar robustness. Proportional control requires plenty of trial and error to determine optimal gains. Experimental results indicate that adaptive feedforward control has excellent tracking performance and almost no phase lag. Proportional control and self-organizing fuzzy control have similar magnitude response ; however, proportional control has serious phase lags problem, which degrade the tracking performance.

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In this paper presents an accurate AFM used in liquid that is free from the Z-directional distortion of a servo actuator is described. Two correction methods are employed in this AFM. One is the external-monitoring method, and the other is the in situ self-calibration method. The external-monitoring method, is based on the fact that PZT actuators from the same class show similar hysteresis patterns. The same voltage signal used to control the servo actuator is applied to another PZT actuator which is termed the reference actuator. The displacement of the reference actuator is measured by a displacement sensor. As a result, the distortion of the AFM image can be corrected satisfactorily. In the in situ self-calibration method, the derivative of the calibration curve function of the PZT actuator is calculated from the profile measurement data sets which are obtained by repeating measurements after a small Z-directional shift. Input displacement at each sampling point is approximately estimated first by using a straight calibration line. The derivative is integrated with reference to the approximate input to obtain the approximate calibration curve. Then the approximation of the input value of each sampling point is improved using the obtained calibration curve. Next the integral of the derivative is improved using the newly estimated input values. As a result of repeating these improving process, the calibration curve converges to the correct one, and the distortion of the AFM image can be corrected. Principles and experimental results of the two methods are presented.

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A constant speed control system of an ultrasonic motor(USM)is designed based on H_∞ control with a repetitive compensator. Generally driving mechanism of USM uses frictional force. It comes the following disadvantages of the motors : (1)the dynamic response shows non-linear natures and depends on the operating temperature ; (2)the average rotational speed gradually decreases with temperature rise ; (3)the speed fluctuates periodically synchronizing with rotation. To tackle the problems, multiplicative uncertainties are introduced into the plant model to represent the non-linearity and the temperature dependency. The decrease and the fluctuation in speed are treated as a step and a periodic disturbance respectively. The control system is designed as follows. Firstly, and integral type H_∞ controller is designed which guarantees robust stability against the uncertainties. Secondly, a repetitive compensator is attached to the system without loosing stability to attenuate the periodic disturbance. Experiments confirm the validity of the proposed control system.

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As a method for measuring vibration intensity on a thin plate, the wave composition method is presented. Sensors are arranged on a circle, and accordingly, measurement is easier using this method than the conventional finite difference method in which sensors are arranged in an array. High measurement accuracy is expected because spatial differentiation is performed algebraically by applying Fourier transform. Simulations of estimation error are performed for progressive wave and divergent wave fields. The error is smaller for a smaller measurement circle ; however, when there are measurement errors at sensors(unavoidable in practical measurements), estimation accuracy using a smaller measurement circle is deteriorated by these measurement errors. Larger circle diameters are suitable for robust measurement. Comparison with the conventional finite difference method is performed. The present method shows good accuracy over a wide frequency range.

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As an application of fuzzy control technology, the control of refrigerant flow in package air conditioners has been established thus far. However, it is difficult to control refrigerant flow precisely by conventional technologies because package air conditioners have various operational environments, such as machine type or length of refrigerant pipe, among others. Therefore, for high-quality control, it is important to design controllers such that they can adapt to various environments. In this respect, we have established a new controller which has a cascade, two-layer fuzzy control structure, in order to achieve higher refrigerating capacity. The adaptability problem, however, remains unsolved in this controller. In this paper we report on the above controller and the results of two additional attempts to improve the adaptability of the controller. First, we outline the controller which has a cascade, two-layer fuzzy control structure. Then, we improve the controller to make it suitable for practical use. Lastly, we develop a new automatic tuning method for fuzzy control that uses a look-up table, in order to improve stability. We demonstrate the ability of the new controller by experiments and simulation.

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The authors introduced a new approach on modeling and proposed a concept of the functional model in the previous report. A method for expansion and unification of this functional model is presented in the present report. The machine is an organic system consists of many parts. All parts act cooperating one another, transferring and changing the energy according to their specific rolls, and as the result of their dynamical collaborations, the machine fulfills its mission as required performance. It is necessary for next age computer aided development of machine to construct the virtual product with which connecting parts from small scale to large scale units, assembling the machine from parts to total product, exchanging parts and disassembling the machine can be performed by simulation in the computer. The proposed method makes this possible. This method is shaped up with three application examples.

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This paper discusses control of a crane mounted on a tower-like structure in case of varying load-rope length. A fast transfer of the load causes the sway of the load rope and the vibration of the flexible structure. Our object is to control both the sway and the vibration by control of torque to the boom. If the length of the load rope varies, it is difficult to control by the fixed compensator, because not only the natural frequency of the load rope but also gain of the plant to the control input vary. We design the gain-scheduled H_∞ controller based on the LMI for the length of the load rope and verify the efficiency of the controller by simulaitons and experiments.

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It has been explained that the position of the shoe center of a ski has a very important effect on skiing, especially on the ski turn. Although the position of the shoe center is impossible to change by using most of the binding available on the market, it is possible to adjust the position by using special bindings. However, we can not find any reports of instructions that explain how to determine the best position of the shoe center. The authors have already developed a numerical approach for estimating the ski turn caused by a skier's edging action. Since the dynamic bending deformation and movement of the ski can be analyzed by the approach, we can estimate the effects of the position of the shoe center on the ski turn by using the approach. In the present study, the ski turn of various skis with a different position of the shoe center are estimated numerically, and the effects of the position of the shoe center on the locus of the ski turn and the relative direction of the ski to the tangent of the locus of the ski turn are discussed.

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In this paper an adaptive sliding controller is presented for second order nonlinear systems with system parameter uncertainties. Using an adaptive technique to estimate uncertain system parameters, an adaptive sliding controller is then proposed to ensure that the sliding condition is maintained in finite time. The proposed adaptive sliding control scheme can be implemented without the requirement that the bounds of uncertain system parameters should be known in advance. Furthermore, the control chattering drawback occurred in the classical sliding mode control can be alleviated in the proposed control scheme. To show the effectiveness of the proposed scheme, some simulation results are presented.

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A laser displacement sensor with the triangular method was applied to the measurement of dimensional errors of a curved profile. Three motors control the position of this laser sensor in the x, y, and θ directions to follow the curvature of the workpiece. Fuzzy-based positioning control was found to be effective for measuring curvatures. The measuring system has an accuracy of several micrometers.

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Adoption of an electronically controlled throttle valve has much potential for improving the performance of automobiles in view of such a valve's flexibility. One of the uses is optional tuning for the accelerator pedal sensitivity, which can be achieved by using two feedback signals, a speed signal and a torque signal, of the wheel axle.It is less expensive and therefore desirable to use a torque signal which does not require a hardware device. Therefore, control using the newly developed software torque meter was attempted in this research. The principle of the software torque meter depends upon a Luders-Nerenda-type adaptive observer. Experimental results showed its superior tuning ability as expected, indicating that the objective of saving costs was achieved. Moreover, it was found that the control achieved adopting the software torque meter is superior to that achieved adopting a hardware sensor, because of the characteristic of low-pass filter of the software torque meter.

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This paper presents the enhancement of vehicle cornering stability through active and independent rear toe control. Because toe change in the rear wheel during high-speed turning maneuvers is an important factor influencing vehicle stability, the active rear toe control vehicle such as four-wheel steering(4WS)vehicle has been developed in past years. Especially, a toe in the rear outer wheel(bump side)plays a dominant role in cornering, hence the four-wheel independent steering(4WIS)system which selectively or simultaneously controls the rear wheels, could be suggested. In the proposed system, there are some advantages not only in energy consumption, but also in control responsiveness. The independent rear steering strategy using rear toe control scheme has been developed and its performances were evaluated with the ADAMS full vehicle model. Also, 4WIS system is compared to the conventional four-wheel steering(4WS)system through the step input and the double lane change test. The simulation results of 4WIS system show the similar handling performance with those of the conventional 4WS system and the total consumed power to control the system in rear wheels was much reduced.

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As an application of virtual reality to welfare work, an obstacle experience system was proposed in which a healthy person can experience the situation with a wheelchair. It is considered that such wheelchair experience system is necessary in dealing with the wheelchair's problems such as the development of new wheelchair and other welfare implements, and the design of cities and various facilities. In this research, a wheelchair experience system, which is capable of moving in a virtual environment with vision information and force feedback, was constructed. This paper describes mainly the development of force feedback system and a fundamental experiment about the movement characteristics with spatial recognition. Experiments of distance assessing by movement are done in the real and virtual environment with the attention to concept of sensory integration and active to evaluate the necessary of force feedback. The results of the experiment are discussed and the effectiveness of present system is inspected.

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Cooperative transportation of an object by two or more mobile robots requires each robot to exert an appropriate force to support and move the object, to move along the object, and to maintain the robot's attitude stably. Studies of cooperative transportation by multiple robots so far have scarcely considered the stability of the robot's attitude influenced by the force from the object. To take part in cooperative transportation, a mechanically unstable robot, such as a wheeled inverted pendulum, needs to control the force and follow the object while standing stably against the force in an integrated manner. We call this "cooperative behavior". To realize this behavior of a mechanically unstable robot, we built a control system to estimate the external force, maintain standing, and exert a specified force. Experiments were conducted on cooperative transportation between a human and the robot.

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In this paper we discuss the stability of frictionless planar grasps using a two-dimensional(2D)virtual spring model. In previous research, a one-dimensional(1D)spring model was widely used for frictionless grasps. However, this 1D spring model has two problems. (i)The direction of contact force was not investigated when the grasped object was displaced by an external disturbance. (ii)The motion of a finger is restricted to the direction along the normal at the initial contact point. To overcome these problems, a 2D spring model is introduced. The force condition, where the contact force always acts along the normal at the contact point, is formulated. Using the potential energy method, the stiffness matrix is obtained. Numerical examples demonstrate the effects of tangential spring stiffness and contact force. As a result, it is shown that an optimum contact force exists for stabilization of the grasp. Stiffness conditions of the springs for stabilization are also established.

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A theoretical and experimental study of the forced frequency response of a nonlinear magnetic bearing system is presented. The system under investigation consists of an unload symmetric rotor that is attached to a flexible coupler at one end and is supported by a radial magnetic bearing at the other end. Identification of a mathematical model describing the dynamic response of such a nonlinear closed loop system based on the principle of harmonic balance is our main goal. We modify this traditional identification technique in order to identify this system more precisely. The frequency response of the resulting nonlinear model has been proven to be well in agreement with that of the experimental data.

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When a gear pair which has tooth surfaces(elastic)modified slightly and convexly from involute helicoids for one member and the conjugate surfaces(rigid)of the involute helicoids for the other is given, the path of contact with its contact normals of the gear pair is obtained as algebraic functions of angle of rotation expressed by two parameters, the deviation of the tangent plane from that at the corresponding point of contact without modification and the inclination angle of the path of contact on the plane of action, which are determined by measuring the single flank error and the helix form deviation. Fundamental requirements for multiple tooth pair contact of the gear pair are clarified and the path of contact with its contact normals under load are calculated, which is expressed through the deviation of the tangent plane at a point of contact under load from that at the corresponding point of contact without modification under no load. The path of contact under load is discontinuous generally at the point where the region of mesh changes. The actual contact ratio of the gear pair which depend on load is also calculated along the path of contact.

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Because sliding leadscrews used in precision positioning systems are directly driven by motors with higher speed, it becomes necessary to evaluate more accurately their friction losses to estimate the required motor power or the amount of heat generated. It has been proved experimentally that the interface between the screw shaft and the nut achieves a hydrodynamic condition under higher rotational speed. Hewever, a method of calculating the friction has not yet been established. This study aims at proposing a theoretical formula to describe the frictional characteristics of sliding leadscrews under the hydrodynamic condition and at verifying it experimentally. In this report, lead errors of a screw shaft and a nut are measured accurately and discussed to formulate a clearance shape model with respect to the drunkenness error of the nut. The infinitely short bearing theory is applied to the shape model in order to derive some dimensionless numbers.

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The theory proposed in the previous report is verified experimentally. The proposed theory is based on the clearance shape model with respect to the drunkenness error of an internal thread, and the frictional property of a sliding leadscrew is described under the hydrodynamic condition by some dimensionless numbers derived from the infinitely short bearing theory. To verify the proposed theory, some experiments are performed on several specimens which have different nominal dimensions. The experimental results are arranged according to dimensionless numbers S and M and are compared with the theoretical results. The experimental results agree with the theoretical results in the range of the hydrodynamic condition ; thus, the appropriateness of the proposed theory is verified. The appropriate driving condition is considered based on the theory and experimental results, and the selection criterion for oil viscosity is shown.

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A new gravity pendulum method has been proposed in order to precisely measure the tooth surface friction coefficient of a pair of mating gears excluding the bearing loss. In this new method, the center-to-center distance between the pair of gears is kept constant with a flexure hinge mechanism in order to reproduce the relative motion, including rolling and sliding, between the tooth surfaces of practical rotating gears. The free damped oscillation of the gravity pendulum was measured, and the tooth surface friction coefficient was calculated by equating the dissipated potential energy of the gravity pendulum during oscillations to the work done by the frictional force between the teeth of mating gears. This method has a big advantage, in that the tooth surface friction coefficient can be measured in a very small region of the tooth profile, because the oscillation amplitude can be set approximately equal to or less than one arc-degree. The distribution of tooth surface friction coefficient on the entire tooth profile can be obtained, as the result. After investigating the influences of the horizontal oscillation of floor and that of the small clearances in the flexure hinge mechanisms on the free oscillation of the gravity pendulum, the distribution of the tooth surface friction coefficient along the tooth profile has been precisely measured for a pair of internal and external gears.

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Running-in tests have been carried out for a piston pump and motor and the lubrication characteristics have been investigated. The friction characteristics on the sliding surfaces have been studied with pin and V-block type of Falex friction tester before the running-in tests, to select suitable conditions of the running-in test. The running-in condition has been decided with considering parameters such as friction force, separation voltage, roughness, roundness and cylindricity. The results are summarized as follows : (1)the rate of running-in of the cylinder with low hardness and low stiffness is lower than that of the piston with high hardness and high stiffness, (2)the optimum taper angle at the piston top for friction force is found, (3)the friction force decreases with decreasing stiffness of the piston.

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The study of friction loss of spur gears was carried out, using test gears with a center distance a=183 mm. The load for the test gears was comparatively high, i.e.the load was applied up to about 60% of the Hertzian pressure of tooth surface strength in endurance strength range and the range of circumferential velocity was extended up to about 120 m / s. Generally speaking, we obtained that, the higher the lubricating oil viscosity, the lower the friction loss. Further we found that a most suitable oil viscosity in order to reduce the friction loss exists for the gear unit, including not only the test gears but also the bearings and the gear box. As far as tooth form is concerned, the cutter pressure angle α₀=25° gives the lowest friction loss for the gear unit.

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We propose a new design scheme of the PID controller optimized of multiple objectives. The game of designing the PID controller is considered in the context of the n-person bargaining game. In this game, a player is defined as having one of the desired properties : decreased ITSE(Integral of Time multiplied by Squared Error) ; fast response time and less overshoot. Utility functions corresponding to the players are also defined as objective functions related to their roles. A set of desired parameters of the PID controller(e.g.PID gains)is given by acquiring the objective functions, it is easy to apply this design scheme to complex design problems. In this paper, an example of simulation results is illustrated to show the effectiveness of this scheme.

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One of major problems in testing or evaluating precisely the thermal behavior of a machine tool is the difficulty of identification of heat transfer coefficient on the surface by conventional method. This paper presents a new method based on the inverse analysis to identify the distribution of heat transfer coefficient. The present method requires only the temperature change measured at several selected points on the machine tool surface. The temperature change is obtained easily during a certain period of warming-up operation of the machine tool. The experimental result obtained with a head stock model verifies the effectiveness of the present method.

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In injection molding of short fiber-polymer melt mixture, the velocity field of the mixture changes due to interaction between fibers, when fiber volume fraction increases. Interaction between fibers and a mold wall also has an effect on the mixture flow property, expecially when fiber length is of the same order as the mold cavity thickness. In this paper, an iso-thermal flow of mixture through a slit channel and fiber orientation distribution in that flow are analysed numerically in consideration with fiber-fiber interaction and fiber-mold wall interaction, and the following results are obtained : (1)In rather short distance from entrance of a slit channel, fibers are rearranged rapidly and the flow becomes approximately steady after that. (2)When fiber volume fraction increases, the mixture flow tends to become plug-like one and pressure loss increases. (3)A layer of low fibers volume fraction is generated along mold wall due to fiber-mold wall interaction, and the pressure loss decreases as fiber length increases.

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A flexible mechanical structure can provide an additional function, such as a kinematic function if flexibility is implemented in some appropriate portions. This flexible structure can be used as a new type of mechanisms which are called compliant mechanisms. We can also construct so-called flextensional actuators by combining the flexible structure with piezoceramic material. In this study, we present a methodology to obtain an optimal structural configuration of a flextensional actuator using the homogenization design method. First, the extended kinematic flexibility defined as the mean transduction is formulated using a mutual energy concept. Second, we propose a new multi-objective function incorporating the kinematic flexibility and stiffness. Next, an optimization procedure is constructed based on the homogenization method and sequential linear programming(SLP). Finally, some examples are presented to confirm the problem specifications of the optimal configurations.

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This paper attempts the control of scheduling in the changing environment by comparing a simple model of the life-cycle of successful human being with the control of scheduling in the industry. The four layers of this comparison are of vital importance, that represent the basic control pattern of scheduling. Then a distributed architecture is designed based on the proposed model. The agents behavior is tested while considering one of the changing parameter i.e.machine breakdown, in a simple scheduling problem. It differs from the other systems because of the distributed architecture, which emphasize the transfer of process for a particular job, during breakdown of machine to another similar machine autonomously, having minimum job-change over time, by using the learning technique. The fitness of an individual is calculated based on makespan. The initial experimental results show that the system reaches good performance both with respect to the quality of the learned knowledge and with respect to obtaining good schedule in the changing environment.

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This paper focuses on the development of domain knowledge in feature-based fixturing planning. A knowledge base can be classified into compiled, qualitative, and quantitative knowledge. The knowledge is expressed in the form of rules to aid the assessment of machining sequences. One example is the utilization of the combination factor for feature primitives. The assessment of the combination factor precludes less optimal machining sequences for machining operations. Four sub-domains, viz., predicate logic, frames, production rules, and procedural programs represent the domain knowledge in fixturing planning. Production rules are the most essential type of knowledge for fixturing planning process. They are a collection of fixturing rules and axioms. The inference mechanism based on the 3-2-1 fixturing method can refer to the production rules and suggest fixturing configurations from a feature-based workpiece data model.

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