The transfer stiffness coeficient method was developed in order to improve the computation efficiency and extend the applicability of the transfer influence coefficient method through introduction of the concept of the substructure synthesis method. In the new method, the structure to be analyzed is divided into substructures, each of which is divided into a number of identical fundamental elements. Each substructure is reconstructed by connection of the fundamental elements and the computation cost is markedly reduced by elimination of the degrees of freedom at the inner nodes of substructures in the process of reconstruction. In addition, the computation procedure, which is the same as that in the transfer influence coefficient method, is applied to the entire structure reconstructed from the substructures, for even greater improvement of the computation efficiency. As the most fundamental example of use of the present method, an algorithm is formulated for free and forced vibration analyses of a straightline beam structure. The validity of the present method is confirmed by the results of numerical computation.

抄録全体を表示

State-space solutions of the H_∞ controller are well developed. Hence, for real structure control design, the first spep is to derive a state-space model of the structure. There are several analytical and experimental dynamic modeling methods that can be used. It is difficult to obtain an accurate model for a flexible and complex structure by the finite-element method(FEM). Therefore experimental modeling is attempted. In this work, we used the eigensystem realization algorithm(ERA)time-domain method based on system impulse response data, to establish a state-space model in order to design the H_∞ control law for vibration suppression. The robust control implementation is exerted on a test bed(truck cab model)with three degrees of freedom. The validity of experimental state-space modeling is confirmed and the robust control performance is achieved.

抄録全体を表示

This paper describes the study of active noise control schemes using two-degree-of freedom control based on model matching for a one-dimensional exhaust duct. In this study, at first, the models are identified using measured frequency responses. Then the feedback controller is designed by using H^∞ control theory and the feedforward controller is designed by using model matching theory. Simulations and experiments are carried out using the designed controllers. The experimental results show a good agreement with the simulation results, and noise reduction of more than 15 dB is obtained over the frequency range from 100 Hz to 500 Hz at the microphone location.

抄録全体を表示

This study investigates, experimentally and analytically, the polygonal wear of truck / bus and car tire and elucidates the generation mechanism of polygonal wear caused by the first natural vibration mode of the tire in the vertical direction. In the analysis, the phenomenon is modeled as a time delay system accompanied by wear in which the amount of wear of the tire is fed back as forced displacement in the vertical direction after the time period of tire rotation. The progress of the polygonal wear of the tire is very slow and is caused by unstable vibration in the steady-state wear process generated in the limited regions where the products of polygonal numbers and the rotational speed of the tire are less than the natural frequencies of the tire system. The tire is deformed almost to the shape of a regular polygonal when polygonal wear occurs. Good agreement between experimental and analytical results concerning the occurrence of polygonal wear of the tire was confirmed.

抄録全体を表示

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

抄録全体を表示

Stochastic fuzzy control using stochastic control theory, instead of using conventional fuzzy reasoning, is proposed. We first solve a control problem of one-step predictive output tracking for linear stochastic systems. Next, we consider dynamic multiple model adaptive control(MMAC)for the initial data distribution, under the uncertainties of the initial states. We further consider static MMAC that can be applied for cases of completely unknown plants. It is then shown that a stochastic fuzzy control has some Gaussian potential functions as membership functions and can be used to assign some a priori probabilities to the fuzzy sets or to the control rules, if the probability density function with respect to the output error is replaced by a simple characteristic function. It is also shown that the stochastic fuzzy contol becomes fuzzy control, if all of the a priori probabilities are set to be equal at any control instant.

抄録全体を表示

A new concept for a robust active rear steering(ARS)system is presented. The system exhibits good control performance even if the vehicle parameters and / or road surface conditions are changed. This system makes the vehicle follow the desired dynamic model by state feedback of both yaw rate and side slip angle. For utilization of a noisy yaw rate sensor and maintenance of high robust control performance, a controller with frequency-dependent gain characteristics was designed by μ synthesis. For estimatation of the side slip angle using a noisy sensor, a new time-variant observer employing a frequency filter was introduced. The results of the simulation and the experimental tests prove the great effect of the new ARS system.

抄録全体を表示

In this paper, mixed H₂ / H_∞ control is studied using the linear matrix inequality approach(LMI). In many linear control problems, the design constraints can be reformulated in terms of LMI. In general, in H_∞ control good frequency response performance is maintained but transient response of control system may not be guaranteed. Here, we have formulated H_∞ and H₂ control separately by means of LMI, and combined both objectives as a mixed control problem. We applied mixed H₂ / H_∞ control to an active vibration control problem and obtained reasonable results in frequency and time domains. The design approach described here is based on a numerical optimization technique which requires use of efficient convex optimization software.

抄録全体を表示

This paper describes a simplified dynamic model and autotuning of feedback gain for the directional control of a small tunneling robot. First, we constructed a dynamic model for the amount of directional correction and determined its parameters by the least squares method. Next, we used a neural network to automatically obtain four feedback gains for the directional control of both pitching and yawing. The inputs for the neural network are an initial deviation and an initial angular deviation for pitching and yawing. The outputs of the neural network are the feedback gains for angular deviations and deviations. The neural network learns from the deviations obtained in the simulations. The neural network, which can adapt to any initial deviations, was formed using plural initial deviations in learning. Moreover, this method can tune the optimum gain for any design line. These results establish the validity of the proposed method.

抄録全体を表示

The combined 3-point method, which combines the generalized 3-point method with the sequential 3-point method, is described in the present paper. The combined 3-point method can not only measure profiles that include high-frequency components whose spatial wavelengths are shorter than the probe distance, but also cancel the influence of the z-directional error and the pitching error in the scanning motion. In the combined 3-point method, some data points from a profile evaluated by the generalized 3-point method are chosen as reference points of the standard area and are used to determine the relative heights among the data groups of the sequential 3-point method. An automatic selection method was used to select the standard area correctly and quickly. Theoretical analyses and computer simulations were performed to confirm the effectiveness of the combined 3-point method. Experimental profile measurements were also carried out using three capacitance-type displacement probes.

抄録全体を表示

A magnetostrictive vibration sensor has several advantages over conventional piezoelectric sensors. First, due to the high impedance output signal, piezoelectric sensors require a charge to voltage converter and a power supply to process the signal. In the case of the magnetostrictive sensors, the output signal is already a low impedance voltage which can be analyzed directly. A second advantage is its structural simplicity. The sensor can be easily assembled or disassembled. A third advantage of the magnetostrictive vibration sensor can be attributed to the high Curie temperature of magnetostrictive materials, which stands at 380°C as compared to 180°C for a typical piezoelectric material. This study presents a novel application of giant magnetostrictive material to a three-dimensional vibration sensor. The sensor is called three-dimensional because it is intended to measure a vibration exerted along an arbitrary direction. Sensor signals are measured for various directions of vibration based on which the identification of unknown vibration is attempted. A neural network is employed to learn the observed data. The generalization of the trained network is tested on unknown vibrations.

抄録全体を表示

The stability robustness problem of discrete-time linear regulators with computational delays under nonlinear / linear time-varying perturbations is considered in this paper. A new sufficient condition is derived for the stability robustness of discrete-time linear regulators with computational delays under nonlinear time-varying. perturbations, and a new sifficient bound is presented for structured linear time-varying perturbations of discrete-time linear regulators with computational delays. An example is given to show numerically that the new structured perturbation bound may provide improved results for elemental perturbations over results based on the structured perturbation bound reported recently for linear time-varying perturbations.

抄録全体を表示

Active vibration dampers and isolators are capable of reducing vibration, and the results are remarkable and can be achieved adaptively. However, they require a large amount of energy to control the vibration. Since structural vibration has motional energy, a question arises as to how we can utilize this energy rather than just simply suppressing it. In this paper an energy regenerative type suspension is presented which utilized an electrodynamic actuator to regenerate electric power during the high-speed motion of the actuator. At low-speed motion, an active control algorithm is applied to the same actuator to provide good damping performance. In order to reduce energy loss in the control amplifier, active relay control is applied instead of linear control. The system is first simulated on a computer and followed by a simple experiment similar to a suspension system. The results are very encouraging and show that the system performed better than a passive suspension system and can regenerate vibration energy.

抄録全体を表示

NKK developed a new combustion controller that reduces both NO_x and CO concentrations in the exhaust gas of municipal refuse incineration furnaces. We found that the manipulation of the cooling air flow rate is important because it affects the furnace temperature and the O₂, NO_x and CO concentrations in the exhaust gas. The new controller manipulates the cooling air flow rate. The controller monitors the furnace temperature and the O₂, NO_x and CO concentrations as process variables and then operates the cooling air flow rate as a manipulated variable. This multi-input / single-output controller was designed using a fuzzy control algorithm and tested on site at a municipal refuse furnace. The result of the on-site test was quite successful.

抄録全体を表示

Ambulatory capability results in overall improvement of ability of daily life(ADL)of the elderly. Technical aid of walking ability is a basic solution for an elderly society. The number of the aged in bed will decrease. Walk Training System for the elderly is now under development. It has two parts:a training environment and a patient-support element. The training environment comprises a treadmill and a display. The trainee stands on the treadmill and begins to walk. The belt of the treadmill is driven by active impedance control. The trainee is supported by a two-degree-of-freedom manipulator. The force on the support is determined by the displacement of the trainee from the reference point, so as to correct the posture of the trainee or to support the trainee's weight. The Walk Training System was tested on 30 persons, and its basic function was highly rated.

抄録全体を表示

A robot system composed of a mobile robot and a manipulator is called a "mobile manipulator". In this paper a calculation method of inverse dynamics compensation for a power-wheeled-steering(PWS)mobile manipulator is proposed. Newton-Euler method is used for the compensation calculation. A mobile manipulator dirrers from a floor-fixed manipulator in that it moves according to non-holonomic constraints. As the constraints integrate velocity and angular velocity errors of the mobile manipulator on a floor, the errors influence the hand position and orientation of the mounted manipulator. The integrated errors do not disappear even after the dynamical vibration of the mobile manipulator is settled. Therefore, to reduce the integrated errors, the velocity errors of the mobile manipulator should be reduced. We propose a calculation method, and the effects of the method are confirmed by simulation experiments.

抄録全体を表示

The dimensional synthesis of the mechanism of an in-parallel actuated manipulator should take into account high motion transmissibility and avoidance of the area surrounding singular points as well as the singular points in the prescribed working space. In this paper we propose a new method based on the Monte-Carlo technique to obtain the kinematic constants which assure high motion transmissibility. This method has been applied to dimensional synthesis of a 6-RSS type spatial in-parallel actuated manipulator with six degrees of freedom. The effectiveness of the proposed method has also been investigated by comparison of the results to those obtained by the conventional method. These results have been used to develop a manipulator driven by direct drive motors. The position repeatability has been experimentally investigated and the result reveals that the manipulator can be used to realize precise positioning superior to those of conventional industrial robots.

抄録全体を表示

It is expected that in the future, robots will play important roles in coexisting with humans. Whenever humans come into contact with these robots unexpectedly, the robots must not only be safe for the humans but also be able to adjust their physical softness parameters, which will help humans remain calm and which will be favorable for human emotions. Therefore, it is desirable for robots to control their impedance characteristics in such cases. From these points of view, desirable values of the impedance parameters of robots are investigated in this work by a rating scale method. In the experiment, 11 subjects come into physical contact with an impedance-controlled robot and evaluate this contact subjectively. The evaluations are performed on 48 combinations of virtual mass, viscosity coefficient, and stiffness. In terms of the results, the emotions felt by the subjects with regard to the robots being soft, pleasant, and human-like are explained by a linear regression model of the impedance values, and the emotions of being reassuring are classified into four groups.

抄録全体を表示

In this paper, we propose a new reinforcement learning algorithm to generate a fuzzy controller for robot motions. This algorithm generates a range of continuous real-valued actions, and the reinforcement signal is self-scaled. This prevents the weights from overshooting when the system receives very large reinforcement values. Therefore this algorithm can obtain a solution in less iteration times. The proposed method is applied to the control of the brachiation robot, which moves dynamically from branch to branch like a gibbon swinging its body in a pendulum fashion. Through computer simulations, we show the fast convergence and the robustness against disturbances.

抄録全体を表示

In order to develop a micromanipulator system for microbonding by adhesive, the characteristics of superelastic hinges made of superelastic materials, for example, shape memory alloy, have been analyzed and represented in the form of charts which enable rational design of micromanipulators. Making use of the characteristic charts, shapes and sizes of hinges can be considered in the determination of the kinematic parameters of a pantograph mechanism with superelastic hinges. The effective performance of the design system is demonstrated using an example of a manipulator for microbonding by adhesive.

抄録全体を表示

A criterion for predicting fracture initiation due to nonuniform shrinkage during sintering of ceramic powder compacts is proposed. In the present criterion, the occurrence of sintering fracture is determined using the difference of volumetric strain between nonuniform and uniform shrinkages because stress is induced by the difference of volumetric strain during sintering. The material constants in the criterion are determined by means of a sintering test using ringed compacts under a condition of restricted shrinkage. Nonuniform shrinkage behavior due to the density distribution during sintering of circular plates and rings with a boss is simulated by the viscoplastic finite element method and the occurrence of sintering fracture is predicted using the criterion from the calculated results. The predicted fracture rates and sites of the sintered products are in good agreement with the experimental results for alumina compacts.

抄録全体を表示

In this study, a robust design approach is presented to determine the desired damper force characteristics of a double-tube shock absorber based on a dynamic analysis in which design constraints to prevent cavitation are derived. First, a nonlinear mathematical model of the shock absorber is developed based on fluid mechanics. Then, the design constraints to prevent cavitation are derived based on a dynamic analysis, and a design methodology of the desired damper force characteristics of a spring-loaded valve is determined. Finally, experimental verifications are performed to confirm the mathematical model and the design constraints, and computer simulations are performed for three design cases to verify the postulated design methodology.

抄録全体を表示

In this paper, the dynamic response of a rectangular elastic plate supported by a fluid on one side and impacted by a low velocity projectile on the other side is analyzed for the first time. A nonlinear Volterra integral equation for impact force F(t)is derived, and a linear numerical method is proposed, which is used to solve the equation and calculate the transverse deflection of and the bending stress in the plate. The presence of the fluid not only lowers the natural frequency of the plate due to the increased inertia, but also damps its transverse vibration due to the energy dissipated in the form of sound waves. As a practical example, the transverse deflection of a square plate supported at the edges and impacted centrally by a low velocity sphere and the impact force are computed numerically. Our results for the natural frequencies of the system consisting of the plate and the fluid, and the transverse deflection-time curve at the center of the plate in vacuo are in excellent agreement with those reported previously.

抄録全体を表示

In this paper we describe the float characteristics of a new type of squeeze-film gas bearing which can be used to realize non-contact linear-motion guide systems which do not require supply of pressurized air. Piezoelectric actuators and elastic hinges are used to induce vibration of the bearing and generate squeeze-film pressure under the bearing. In a theoretical analysis, a simple dynamic model of the bearing structure is presented. The influences of the displacement and vibrational frequency of the piezoelectric atcuators on the float characteristics are investigated theoretically and experimentally. Furthermore, the load capacity at a vibrational frequency of 2400 Hz and the float characteristics at the resonance frequency of the bearing are measured. It was found that the bearing can be used to realize a non-contact linear motion guide and that the dynamic model presented in this paper can be used for accurate prediction of the float characteristics of the bearing.

抄録全体を表示

This paper is devoted to the kinematic and sensitivity analyses of a new designed toggle mechanisms which is the combination of two slider-crank mechanism. The analytic analysis is developed for obtaining the general equations of position, velocity, and acceleration for each link. Three common types of motion including constant acceleration, simple harmonic and cycloidal are considered as the inputs while the corresponding outputs between two toggle positions are studied. By using geometric relationships and trigonometry, the various results of kinematic and sensitivity analyses are presented and compared between the four-point type and five-point type toggle mechanism.

抄録全体を表示

In past sequential studies on qualitative optimization, it has been shown that we can carry out optimization using qualitative grasps of the behaviors of the objective functions and constraints. A key issue in carrying out qualitative optimization is the determination of qualitative sensitivities. In this paper, we propose a new method of deriving qualitative sensitivities using existing optimum design results of simple structures. In general, the results of optimum design greatly depend on the formulation of the problem, so it is very difficult for the designer to formulate large-scale or complex problems, and to formulate their sensitivities. However, even in these cases, it will be possible to use analogies with parts of the optimization results for simple structures. In this study, we estimate qualitative sensitivities by making use of local information regarding these existing optimum results. We examine the proposed method and demonstrate the effectiveness of the method through simple numerical examples.

抄録全体を表示

In a previous paper, for a variety of structures extracted from a machine, a hierarchical representation sheme was introduced, in which s-structures(s=1, 2, ···, 5)were identified as the machine structures essential to analyzing the phenomena of interference among parts of a machine in motion. In this paper, the properties of the structures are mathematically treated in terms of interference. By using a topological link of closed curves, a theorem is proved which states a sufficient condition for the following proposition:A given 3- or 4-structure with closed loops of members is Σ³-interferential with regard to a closed motion. This proposition means that the 3- or 4-structure causes every machine derived from it to produce interference during the motion;hence the theorem enables one to filter out unsuitable design plans of 3- or 4-structures from the point of view of interference avoidance.

抄録全体を表示