Robot dynamics has been traditionally viewed from the perspective of a manipulator's joint motions, and significant effort has been devoted to the development of joint space dynamic models and control methodologies. However, the limitations of joint space control techniques, especially in constrained motion tasks, have motivated alternative approaches for dealing with task-level dynamics and control. The operational space formulation, which falls within this line of research, has been driven by the need to develop mathematical models for the description, analysis, and control of robot dynamics with respect to task behavior. In this article, we review the operational space task-level models and discuss the various control methodologies that have been developed in this framework. These include : the unified motion and force control approach ; the notion of dynamic consistency in redundant manipulator control ; the reduced effective inertia property associated with macro-/mini-manipulator systems and the dextrous dynamic coordination strategy proposed for their control ; and the augmented-object model for the control of robot systems involving multiple manipulators.

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In previous papers, we proposed nonparametric identification techniques of nonlinear multi-degree-of freedom systems. Theoretically, these techniques can be applied to systems with any number of degrees of freedom. In practical cases, however, it has been found difficult to apply these techniques to systems with greater number of degrees of freedom, because the unknown parameters for a system become vast as the degrees of freedom become more numerous. In this paper, an improved technique is proposed which requires fewer unknown parameters, and which is furthermore more convenient for use in succeeding vibration analysis. Numerical simulation is conducted, and the applicability of the improved technique is shown. Its advantage in succeeding vibration analysis is demonstrated through using the identification results in the incremental transfer matrix method.

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In previous papers, the authors proposed a numerical approach for analyzing the vibration problem of combined systems. For free vibration analysis, the approach consists of two steps. One is estimating Green's function for a static bending problem of the same plate and the other is to solve a frequency equation. First, this approach is applied to a symmetrically laminated FRP(fiber-reinforced plastic) composite plate. Numerical calculations are carried out for a cantilevered plate and a clamped plate. Green's function of a cantilevered plate is estimated by the Ritz method and that of the clamped plate is obtained by Galerkin's method. Accuracy and convergency of natural frequencies of these plates are discussed. Next, in an attempt to reduce the number of dimensions of the frequency equation, it is assumed that the deflections at 5 adjacent points on a straight line can be approximated as a parabolic function. This approximation reduces the number of dimensions of the frequency equation and the number of Green's functions. The improved approach was applied to a cantilevered plate. Numerical results showed that the computing time was reduced significantly by the approximation.

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The spline finite strip method applied so far to the free vibration analysis of plates with classical boundary conditions has been extended to the forced vibration analysis of plates with edges elastically restrained against both translation and rotation. The steady-state response of plates under harmonic excitation is studied in this paper. The formulation has been generalised, so that arbitrarily shaped plates with restrained curved boundaries can be handled. The contribution of the edge restraining has been incorporated in the structural stiffness using a consistent formulation. Deflection and bending moment amplitudes have been determined for different edge restraints, aspect ratios, forcing frequencies and plate shapes, as available in the literature, and comparison of the results indicates good accuracy.

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This paper deals with the modal analysis of complex structure systems with weak connectors by means of matrix perturbation. A complex structure is divided into a number of uncoupled substructures by disconnecting the weak connectors between them, and then the complex structure is regarded as a perturbed structural system deriving from the uncoupled substructures system. Therefore, the eigensolutions of the complex structure can be obtained from the eigensolutions of the uncoupled substructures using the matrix perturbation technique. Two examples are included to illustrate and verify the validity of the procedure.

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This paper describes a new method that detects directly the point where rubbing occurs during operation using data of vibrations. This method is based on the analysis of the nonlinear vibration caused by rubbing. A particular feature of the nonlinear vibration is that the amplitude of higher harmonics in the response becomes large in the vicinity of the point where rubbing occurs. The point where rubbing occurs can, thus, be detected by investigating the distribution of the amplitude of higher harmonics included in the response along the rotor. In the case of a rotor system having an overhanging disk or excited by internal resonance, the distribution of the amplitude occasionally shows another large peak in addition to the peak at the point where rubbing occurs. Even in this case, the presented method can be used to detect the point where rubbing occurs by investigating the eigenvalues and the mode of the rotor system and taking the influence of the overhanging disk into consideration, because the influence of internal resonance on the amplitude of higher harmonics is not great and, furthermore, the influence of the overhanging disk appears only in the vicinity of the overhanging disk.

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In active vibration control, gust load alleviation and flutter suppression method are studied for aircraft. For this purpose, an aero-servoelastic analysis code was developed using the finite element code MSC/NASTRAN. Moreover, a control law synthesis method was developed and applied to the LQG (linear quadratic Gaussian) method for reduced-order control law design. To validate both aeroservoelastic analysis and the control law synthesis code, the wind tunnel test of gust load alleviation was conducted in a 2 m low-speed wind tunnel of Nagoya Aerospace Systems Works using an aeroelastic wind model equipped with an actively controlled trailing edge surface. Analytical results were compared with the results from tests, and good agreement was obtained for wing acceleration. To estimate the effects of gust load alleviation and flutter suppression, they were applied to a 150-passenger twin-engine commercial airplane. For gust load alleviation, a 46.9% wing bending moment reduction was caused, as well as a flutter suppression of 30.7% flutter speed augmentation.

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We can recognize that both the model-following servo control system and 2-degree-of-freedom control system comprise the stable closed loop for the controlled object, the model, and the feedforward path from the model to the closed loop. In spite of the structural similarities, they are considered to be different systems. Since the mathematical tools used for the formulations are the state equation and the transfer function matrix, respectively, the approaches to solving the problem are different. However, the basic structures in both control systems are the same and it may be inconvenient for us to consider the two system as entirely different ones. Hence, clarifying the relationship between the model-following servo control system and the 2-degree-of-freedom (d.o.f.) control system is a very significant issue in the case of application to an actual plant. In this paper, the design method of the model-following servo control system and 2-d.o.f. control system are examined, and their similarities and differences are clarified. Next, the convergence to the model given by the designer is compared using the frequency response. In the model-following servo control system, the dimension of the model was not previously taken into consideration. However adequate convergence to the model can be shown by using numerical examples, if the dimension of the model is restricted in them.

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This paper describes finite-element analysis of electromagnetic fields and optimization of eddy current densities. First, we derive the state equations by means of the finite-element method. Eddy current densities are represented by derivatives of the state variable x(t). A linear quadratic performance index is introduced so that eddy current densities will track the desired functions. We obtain an optimal control law from the stationary conditions of the performance function. Optimal inputs are expressed by solutions of two differential equations. Finally, we show numerical examples.

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In measuring the roughness of machined surfaces with an scanning tunneling microscope (STM), it is necessary for the STM to have a large scanning area. In this report, a newly developed STM system which meets this requirement is described. It consists mainly of an X-Y stepping motor stage and three tunneling tips along a line, each of which is driven by a piezoactuator. The tip positioned at the midpoint is used as a measuring probe ; the right and the left ones are used as smoothing probes, which are not sensitive to surface roughness and are used to create a kind of reference surfaces. The STM is designed to cancel the relative shift in the z-direction due to thermal drift and/or vibration between the measuring tip and the specimen by means of the two smoothing tips. The basic characteristics of the STM system are investigated and measurements are attempted. The STM makes it possible to perform millimeter-scale scanning without visible reduction in resolution. Moreover, a new system combining an optical sensor with the STM is also constructed. With the use of this system, the results from our STM and those from the optical sensor can be compared closely.

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In this study, a four-bar linkage above-knee (AK) prosthesis with an electrohydraulic controller was developed. A microcomputer was employed to regulate the puppet valve of the hydraulic control system. To obtain a reliable design, a test rig was also designed for evaluation of the knee controller performance. The rig had a variable-speed alternate-current servomotor for simulating the angular displacement of the hip joint at different walking speeds. A proportional+derivative (PD) controller was employed to regulate the knee torque of the above-knee prosthesis. Experimental results revealed that the controller can produce a knee joint trajectory close to that of a normal person or a designed one. Use of the electrohydraulic controller can be expected to improve the amputee swing phase gait.

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This paper describes one approach for the communication architecture of a "cellular robotic system (CEBOT)", which consists of a large number of autonomous robotic units or "cells." The strategy is based on the selection of a "master cell, " where the master cell is assumed as a coordinator in the system. The selection is made using "network energy" as an evaluation function, which is proposed in this paper and is based on the probability of the information flow in the network. We describe a mastering method which implies the determination of a master cell, and show the mastering method using the local sensitivity of the network energy, called "local energy sensitive estimation." The local sensitivity is defined as local network energy which takes only the influence of a cell adjacent to the master cell into consideration. The search for a master cell can be performed effectively. We show the simulation results of mastering.

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Use of a wall-climbing robot for such purposes as rescue, wall inspection and fire-fighting in high-rise buildings has been anticipated for a long time. Three different types of models have been developed in our laboratory. The present one can move on a wall using the thrust force of propellers, which are inclined slightly toward the wall to produce the frictional force between the wheels and wall surface. It has a long and lightweight body for climbing an irregular wall surface, and its mechanism and the control system by which it can move in calm or mild wind conditions are discussed briefly.

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The hunting reduction and increase of stability during high-speed travel are two major considerations in improving the traveling characteristics of unmanned delivery carts (AGV : automated guided vehicle), an important component of modern factory automation systems. An AGV has been developed for the study of traveling behavior, particularly the behavior related to inertial force and the cornering force on wheels. A scheme for control of the AGV's steering system has been used to examine the limiting speed for stable traveling and control system stability. For an AGV to travel in a straight line at a high speed, it requires highly accurate detectors, a highly responsive steering system and optimal steering gain. In experiments using a new AGV with the above control scheme, the AGV traveled smoothly at 60 m/min with a hunting amplitude as low as ± 16 mm and a hunting period of less than 3 seconds. This hunting amplitude is less than the width of the guiding tape. The new AGV became unstable near 96 m/min.

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The rotational motion of a gear pair with modified tooth surfaces under load is analyzed with their equivalent tooth profiles. The path of contact consists of two different curves connected discontinuously. On its continuous region, equations of motion are solved and the fluctuating tooth load is calculated. At the point where it is discontinuous, the impact load is calculated from the difference in angular momentum. The gear pair rotates steadily because the kinetic energy which is transferred from one member to the other in the mesh region is returned through the impact. The dynamic increment of tooth load during one period, i.e., the external force acting on the gear vibration system, is given by a periodical function composed of the fluctuating and the impact loads, which is expressed as a Fourier series. The newly developed method is applied to a gear pair with symmetrical convex tooth surfaces, by which most tooth surfaces modified for practical use can be approximated. An analytical equation for the amplitude of the dynamic increment of tooth load is derived and its characteristics are shown through a numerical example.

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This paper presents a study on the deflection and bending moment of the WN (Haseg SymMarC) gear tooth. The tooth deflection and root stress of a Haseg SymMarC gear tooth due to a concentrated load were calculated using the three-dimensional finite element method (FEM) and compared with the measured values. The study confirmed the validity of the gear model and constraint condition used in this FEM analysis, and determined the critical section of the Haseg SymMarC gear tooth and the effects of the number of teeth and face width on the tooth deflection and bending moment. Furthermore, on the basis of these results, the approximate equations of the influence function for the deflection and bending moment factor of the Haseg SymMarC gear tooth were derived.

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Polygon mirror laser scanners have been widely used in computer peripheral equipment and office automation systems, and improvement in scanning quality has been desired. In light of this, the use of self-acting air bearings has been recommended in spindle design to realize superior performance in terms of rotational speed and rotational errors. This study concerns the analysis of characteristics of spirally grooved thrust air bearings. Namely, it reports the rigidity, load capacity, power loss and critical damping factors. Employed in this study are the finite element method (FEM) and the computer simulation method in order to obtain a numerical solution to the Reynolds equation. Based on calculation results, the load characteristics and the effects of various design parameters of the bearing are discussed, and optimization principles for designing the bearing are proposed. The proposal may be summarized as follows. ( 1 ) The bearing rigidity and load capacity are closely related to the spiral groove width, depth, length in the radial direction and spiral groove pump-in angle, and the number of grooves should be as large as possible. ( 2 ) Decrease in the bearing clearance and increase in the bearing outer radius together achieve the best damping characteristics.

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The results of experimental study of ultraprecision orthogonal microdiamond cutting of single-crystal copper are presented. The orthogonal cutting tests were carried out on an ultraprecision fly-cutting machine at various nominal depths of cut from 3.0μm down to 0.01μm (10nm). The machinability in microcutting and the influence of crystal orientation on the microcutting process are discussed from the standpoints of chip formation, cutting force and surface integrity. It is confirmed that continuous chips are formed under all cutting conditions examined. The magnitude of the cutting force and the shear angle are substantially influenced by the crystal orientation at depths of cut of 1μm or more, while they are not notably influenced with depths of cut below 1μm.

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