A rigid (micro) robot mounted serially to the tip of a long, flexible (macro) manipulator is often used to increase reach capability, but flexibility in the macromanipulator can make it susceptible to vibration. A rigid manipulator attached to a flexible but unactuated base was used to study a scheme to achieve positioning of the micromanipulator combined with enhanced vibration damping of the base. The interaction forces and torques acting between the robot and its flexible base were modeled and studied. Simulated and measured interactions generated at the base of a three degree of freedom rigid robot are compared. Simulated and experimental results are included that demonstrate with the proper control of these interactions, damping can be added to the base.

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A new vibration isolation system using negative stiffness realized by active control technique is proposed in this paper. The serial connection of a normal spring and a suspension system with negative stiffness enables the isolation system to have low stiffness for vibration from the ground and high (theoretically infinite) stiffness against direct disturbance acting on the isolation table. A control method of realizing negative stiffness with a linear actuator is presented in an analytical form. The validity of this method is confirmed experimentally with an apparatus equipped with a voice coil motor. It is also confirmed experimentally that high stiffness against direct disturbance on the isolation table can be achieved in the proposed vibration isolation system.

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Although active magnetic guides (AMG) can obtain an infinite static stiffness and high damping using sophisticated multi-degree-of-freedom control, still a non-negligible dynamic compliance is inherent. This is especially true when high controller gains cannot be achieved due to spill over effects. Several approaches are known to overcome this problem, repetitive control and frequency estimation being two of them. Both have drawbacks concerning flexibility, robustness and compensation quality. This paper proposes a smart frequency identification and compensation scheduling algorithm along with tracking compensation oscillators to cancel arbitrary periodic disturbances. The proposed algorithm has been implemented and tested on an AMG. The introduced smartness provides a very robust behavior and leads to an infinite steady state stiffness.

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A design method that can suppress the vibration from high-order resonant modes in a head-positioning system of a hard disk drive was developed. This method uses the vector locus of an open-loop transfer function to design both the controller and the structure simultaneously. Application of the method to an actual hard disk drive showed that positioning accuracy under high-order resonant modes can be improved by 55%. In addition, when all resonances are in-phase, the developed method can suppress vibrations caused by all mechanical resonances. It is concluded that the method can design a control system with high robustness and high following-control performance.

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In this paper, we propose a method of applying a two-degree-of-freedom (2DOF) control since such control of a multi-axis electrodynamic shaking system requires no iteration control and has real-time performance. We first introduce an ideal mathematical model and an uncertainty weighting function for the system, and design a feedback controller using µ-synthesis. Moreover, we adopt a 2DOF controller to improve the transient response. Then, an adaptive filter is added when control performance still cannot be satisfied. An adaptive filter is inserted in series in a feed-forward block and is structured to compensate the difference between a nominal model and an actual plant. Also, uncertainty of the system is considered, and an adaptive filter based on the H_∞ filter is employed. Lastly, we inspect the performance of the controller experimentally, using a resonant specimen. The proposed controller is confirmed to have achieved a superior performance in such a situation.

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This paper proposes a reduced-order physical modeling method for controlling the multi-modes of vibration of an active isolation system with an elastic table. In the lightweight isolation table, the elastic modes appear on the isolation table in a lower frequency domain. In order to avoid the spillover phenomena, the reduced order model, which includes elastic modes, is used in this modeling method. In this study, a reduced order physical model, expressed by 5DOF systems for controlling the multi-modes for designing the controller, LQ control systems, and a two-degree-of-freedom control method with feedforward control are applied. Finally, the discrete model and the controller design are verified through numerical calculations and experimentation.

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In this paper, a design method for decoupling a multiple-degree-of-freedom (DOF) control system is proposed. In general, decoupling control systems have been designed by transforming the motion modes into the vibration modes using a modal matrix often utilized in the field of modal analysis. In the case where the physical parameters of the system are unknown, experimental modal analysis is currently the preferred method of estimating the modal matrix. This paper, however, proposes a new modal matrix estimation procedure based upon the state space model that has been identified by the subspace method. It then illustrates a design method for an independent modal control system using the estimated modal matrix. The effectiveness of the proposed method is examined through numerical simulations.

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This paper reports the experimental tests conducted on a 5-storey benchmark model defined by Samali, using an Active Mass Driver (AMD) system, where the control action is achieved by using Fuzzy Logic controller and UTS state-of-the-art shake table facility. The performance of the Fuzzy controller is checked against Hachinohe 1968 and Northridge 1994 earthquake records as input excitation to the benchmark model. The main advantage of the Fuzzy controller is its inherent robustness and ability to handle any non-linear behaviour of the structure. The results of the experimental tests show the ability of the adopted Fuzzy controller to reduce the building responses for the two earthquake records used.

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The X-, Y- and Z-Tower office buildings of the Harumi Island Triton Square are located very close to one another. The distance between two of the three towers is as narrow as 13 meters. To increase the habitability of these buildings when they vibrate during a strong wind, they are equipped with active-damping bridges. Each active-damping bridge connects one building to another and actively controls expansion and contraction to reduce vibrations. In this paper, a general description of the buildings and equipment will be presented, following which an applied control system design method will be related. The paper will conclude with a report of tests on the actual buildings conducted to verify performance.

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Uncertainties in the dynamics model of a smart structure are often of significance due to model errors caused by parameter identification errors and reduced-order modeling of the system. Design of a model-based Failure Detection and Isolation (FDI) system for smart structures, therefore, needs careful consideration regarding robustness with respect to such model uncertainties. In this paper, we proposes a new method of robust fault detection that is insensitive to the disturbances caused by unknown modeling errors while it is highly sensitive to the component failures. The capability of the robust detection algorithm is examined for the sensor failure of a flexible smart beam control system. It is shown by numerical simulations that the proposed method suppresses the disturbances due to model errors and markedly improves the detection performance.

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This paper deals with the active control of progressive wave of a simply supported, lossless, thin distributed-parameter planar structure. It is the purpose of this paper to present a novel active wave control method for blocking the progressive wave, and thus a quiet zone (a specific region where vibration is to be prohibited) is produced. It is also the purpose of this paper to present a means to visualize wave propagation of the structure, whereby control effect for suppressing power flow in terms of vibration intensity, progressive wave, reflected wave and the combination of thereof becomes evident.

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The effectiveness of feedback control technique in suppressing flow-excited oscillations is illustrated by considering several examples of fluid-structure-sound interaction mechanisms. These include impinging flow oscillations, flow-excited acoustic resonance, vortex-induced lock-in vibration and turbulent buffeting vibration. The control actuator in all examples consists of a synthetic jet issuing from a narrow slit positioned at the location of flow separation. The synthetic jet is generated by loudspeakers, which are activated by the signal of a sensor monitoring the system response. Different types of controllers are used to properly adjust the phase and the gain of the speaker signal with respect to those of system response. Different sensors are also employed to investigate the effect of sensor type on the control performance. The developed technique proved to be very effective; reducing the oscillation amplitudes by amounts reaching 35dB.

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In this paper, we elucidate the development and the multitask cooperative control of humanitarian demining assistance robots. In particular, the aim in this paper is to propose the first platform robots for humanitarian demining as a global pioneering project. Here we propose two kinds of mine detection robots which consists of six-legged walking robots with two manipulators for added stability, mobility, and functionality. One of the proposed mine detection robots is the COMET-II which is a 120kg class robot driven by electric power. The other robot is the full autonomous mine detection robot the COMET-III which is a 1 ton class robot driven by hydraulic power with a gasoline engine. The COMET-III has a crawler and six legs and it can continue a mine detection operation for four hours. An improved version of this kind of robot will be engaged for mine detection operation in actual mine fields in the near future.

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This paper considers the derivation and application of closed loop vibration controllers that are designed for the attenuation of multiple discrete frequency rotor vibration components. The complex amplitudes of each vibration component are evaluated in real-time and used for dynamic feedback control with frequency matched control signals. Multi-input, multi-output system gain matrices are derived from on-line identification routines, performed under a finite set of different operating conditions. Controller gain matrices are synthesised using linear matrix inequality existence conditions for closed loop system stability and attenuation performance. Thus, the controllers can be designed with a degree of robustness to changing/non-linear dynamics. Implementation and testing is undertaken on a flexible rotor test rig with magnetic bearings. The controllers are shown to simultaneously attenuate vibration due to direct rotor disturbance forces and other indirectly forced non-synchronous frequency components over a range of operating conditions.

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High precision rotation of compact spindles that are contact-free suspended by active magnetic bearings, require high performance position sensors placed in suitable locations around the spindle. Industrial available position sensing devices either use large sensing probes, or are too expensive and are often already too application specific to be adapted. Therefore, an alternative position sensing device based on the electrostatic sensing principle measuring mutual capacitance is studied in this paper. For getting insight into the general tendency of mutual capacitance, an overview is elaborated by finite element modeling, mathematical derivations and experiments. It shows that there are three different types of spindle surface materials, each influencing the mutual capacitance in a different way. In addition, an optimized sensor pattern has been manufactured using a standard, low cost printed circuit board technology. First experimental results demonstrate a position measurement with a 40[nm] resolution and a signal-to-noise ratio of 74[dB].

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Implantable left ventricular assist devices are powered by batteries. Their limited capacity has to be used as efficiently as possible. At the example of a MAGLEV centrifugal LVAD it was demonstrated that a drastic reduction of power consumption (50% in the bearing) could be achieved by vibration control. A vibration controller design for the non-linear plant is discussed, simplified and extended to four harmonics. A new phase shift strategy is presented to eliminate time-consuming matrix operations. Based on this simplification the implemented algorithm applied on the bearingless slice motor allocates little memory and requires short computation time. Additionally, the decreased control currents lead to higher control margins of the power amplifiers and therefore to improved robustness.

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A MEMS device for the profile measurement of high aspect-ratio microstructures has been developed. The goal was to implement a method to be used when the conventional methods were inappropriate. The main part of the tool is a silicon micro-probe with a sharp tip at its end and an integrated piezoresistive strain gauge sensor. The probes are from 500µm to 1mm long with a cross section area of 20×20µm²; they were mainly designed for the characterization of narrow and deep “EDM” micromachined micro-holes having a radius as small as 50µm and a depth up to 800µm. The profile measurement method has been extended to the characterization of several other microstructures. The measurement accuracy is about ±30nm.

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In order to realize a wearable power assisting suit for assisting a nurse to carry a patient in her arms, the power supply and control systems of the suit have to be miniaturized, and it has to be wireless and pipeline-less. The new wearable suit consists of shoulders, arms, back, waist and legs units to be fitted on the nurse's body. The arms, waist and legs have new pneumatic rotary actuators driven directly by micro air pumps supplied by portable Ni-Cd batteries. The muscle forces are sensed by a new muscle hardness sensor utilizing a sensing tip mounted on a force sensing film device. An embedded microcomputer is used for the calculations of control signals. The new wearable suit was applied practically to a human body and a series of movement experiments that weights in the arms were held and taken up and down was performed. Each unit of the suit could transmit assisting torque directly to each joint verifying its practicability.

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This paper describes an easy-to-operate, omni-directional cart. This cart includes power assist technology that acts for both the longitudinal and rotational motions of the cart. Two objectives are set for this development. The first objective is to overcome the difficulty of shifting the cart laterally. Therefore, the equation for calculating the cart turning speed is modified so that the moment, which is driven by the operating force in the right/left direction, is offset. As a result, it becomes possible to stabilize the balance between the operating force in the right/left direction and the operating moment, and improve the operating performance. The second objective is to overcome the other difficulty whereby, during the one-hand pull-operation, the cart tended to run off course to the right/left. To solve this problem, we add a positional control in the right/left direction. As a result, we reduce the lateral deviation of the cart, and improve the operating performance.

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The system considered in this paper is a Toroidal Continuously Variable Transmission (TCVT) system for cars. This system is unstable in reverse motion as some mechanical parts have been removed from the original one for cost reduction, and the gear ratio has to be regulated around its nominal value for car reverse motion. The control theory used here is the Linear Quadratic Regulator (LQR) associated to a gain-scheduling technique, as the TCVT system is nonlinear according to the car speed. Moreover, as the LQR method requires the entire TCVT state vector and as the only available signal is the gear ratio, a full-order observer is designed. In order to take the other nonlinearities of the system into account, the observer is nonlinear: a diffeomorphism is then used for converting the variables provided by the nonlinear observer into the needed variables. In order to verify the effectiveness and the robustness of the controller against the car speed and the torque shift disturbance phenomenon, several experiments with a test-bed and with an actual vehicle have been performed and showed the efficiency of the proposed controller.

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This study aims at establishing a robust intelligent control method with higher control performance and wider applicable region by extending the Cubic Neural Network (CNN) intelligent control method. In particular, this study deals with a nonlinear and failure-proof control problem for an intelligent control method of integrated CNN. The proposed CNN is applied to a control problem of a swung up and inverted double pendulum mounted on a cart. In this study, the dynamical energy principle is embedded into the integrator of CNN that consists of multilevel parallel processing on different degrees of abstraction. In order to confirm the effectiveness of the integrated CNN controller, we carried out computational simulations and experiments using a real apparatus. As a result, it was demonstrated that the integrated CNN controllers can stand up the double pendulum taking into account the cart position limit for the case of arbitrary initial condition of the pendulum angle.

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In this paper, we propose a method of control system design which takes the actuator saturation into consideration. By using a hyperbolic tangential function as the saturation function, we introduce both the time derivative of the controller output and the anti-windup control structure with the feedback loop of the error between the controller output and the saturation function output. Furthermore, we formulate a linear parameter-varying system to design the gain-scheduled controller. The effectiveness of our proposed method is verified by carrying out the experiments of the positioning control for a cart and inverted pendulum system.

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This paper deals with compensation for windup phenomena due to actuator saturation in sliding mode control systems with integral action. It is shown that the actuator saturation causes windup phenomena similar to integrator windup, which might take place in linear control systems with integral action, even if the linear component of the control input does not include any integral action. This means it is not sufficient just to apply the existing anti-windup methods for the linear controllers to the sliding mode controllers. In other words, the nonlinear component of the control input should be reconsidered. Therefore a simple modification for the switching function is presented in order to reduce the nonlinear component of the input during saturation. It is shown that this modification makes it possible to keep the plant state close to the ideal sliding mode. Simulation and experimental results show the effectiveness of the proposed method.

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In this paper, a new type of sliding mode controller with gain-scheduled variable hyper plane for position and force control is presented. In this controller, the hyper plane in the sliding mode controller is continuously adjusted according to the environmental stiffness identified in real time. This controller is applied for force control using a one-degree-of-freedom manipulator system, and the performance of this controller is verified for both simulation and experiments.

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In this paper, a dynamic impact control is proposed. To deal with an impact phenomenon and to establish the control method, a pendulum-like impact shot system is devised. In this system, a slider strikes a ball suspended by a wire, and the energy of the ball is controlled via impact force from the slider. In order to transmit the energy adequately, it is necessary for a slider to reach the target position with specified velocity just at the moment of collision. The reference trajectory for a slider is generated and adjusted in real time, and the proposed variable structure (VS) servo control enables chattering-free precise tracking to the reference trajectory. Additionally, by combining an adaptive VS-differentiator, the performance of the VS-servo control is enhanced. The effectiveness of the proposed impact control, the VS-servo control and the adaptive VS-differentiator is verified by simulation and experiment.

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This paper describes a numerical and experimental study of a double jointed fish robot utilizing self-excitation control. The fish robot is composed of a streamlined body and a rectangular caudal fin. The body length is 280mm and it has a DC motor to actuate its first joint and a potentiometer to detect the angle of its second joint. The signal from the potentiometer is fed back into the DC motor, so that the system can be self-excited. In order to obtain a stable oscillation and a resultant stable propulsion, a torque limiter circuit is employed. From the experiment, it has been found that the robot can stably propel using this control and the maximum propulsive speed is 0.42m/s.

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A design method for the hip prosthesis is proposed which can alleviate problems associated with stress shielding, proximal loosening and the high stress of bone-implant interfaces after total hip replacement. The stress shielding which may lead to bone resorption, can cause a loosening of the stem and a fracture of femoral bone. Generally the composites were more suitable for hip prosthesis material in the long-term stability than metallic alloy because design cases of composite materials produced less stress shielding than titanium alloy. A bone remodeling algorithm was implemented in a nonlinear finite element program to predict the long-term performance of the hip prosthesis. The three neck shapes and three cross sections of composite hip were examined. It was found that the stress concentration in the distal region of the titanium stem which may cause the patient's thigh pains was reduced using composite material. The head neck shape was closely related with the cortical bone resorption and the cancellous bone apposition at proximal region whereas the cross-section was closely related with the relative micromotion between interfaces. The convex head neck type with the quadrangle cross-section produced less subsidence at proximal region on the medial side than the others. For all composite material cases, the cancellous bone apposition occurred at partial interfaces, which may result in a stable bio-fixation. The design performances of the convex neck head type with the hexagonal cross-section designed to insure the long-term stability were found to be more suitable than the others.

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This paper presents a numerical method of optimum design of mechanical structures for reducing noise. This method couples an optimization technique based on a genetic algorithm (GA) with both a finite element code for determining structural vibrations and acoustic radiation analysis for determining sound pressure levels at the receiver point. Reducing the sound pressure level associated with the fundamental acoustic resonant mode is accomplished by adding masses to a vibrating plate coupled to an acoustic cavity which is excited by a sound source. The positions of the masses on the plate are adopted as the design variables. By using the presented method, the optimal positions that would not be easy to be found by any intuitive solution are determined so as to effectively reduce the sound pressure level. The numerical prediction of the effect of the optimization is compared with the experimental result.

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In magnetic disk drives, the disk flutter due to high-rotational speed causes the increase of the head-positioning error. It is important to clear the mechanism of the head-positioning error caused by the disk flutter. This paper conducts the experiments to verify the mechanism proposed in the former report. The experiment was conducted by comparing the head-positioning error predicted by the proposed mechanism with the measured head-positioning error signal. It is confirmed that the proposed mechanism can predict the head-positioning error within the 10% error. The former reports also said that the flutter transfer ratio defined in the report could decrease the head-positioning error without reducing the amplitude of the disk flutter. This paper also verifies it experimentally. In the experiment, the thickness of the slider was changed to make the flutter transfer ratio small. This paper also proposes the method of making the beam angle of the gimbal slant to make the flutter transfer ratio small. The effectiveness was confirmed by the simulation.

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The accuracy of rotor balancing is influenced by measuring errors essentially. The conventional influence coefficient method considering measurement errors is able to improve the balancing accuracy of symmetrical rotors. However, the balancing accuracy of asymmetrical rotors cannot be improved by using conventional method. Since asymmetrical rotors are axis-asymmetrical, the balancing result is affected by inequality of rotary inertia and bending rigidity. This study has presented a modified influence coefficient method for the determination of imbalance with the consideration of measurement errors based on the least-squares technique. The present method has derived theoretically and verified by the experiments of balancing a rotor kit.

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An experimental validation of a model based identification technique is presented in this paper. The validation is performed on both real machines, like large steam and gas turbogenerators, and test rigs. The aim is to show that the method is able to locate the actual fault, to evaluate its severity and to discriminate among faults that have similar symptoms. A quantitative index, called residual is introduced to evaluate the accuracy of the performed identification. The actual developing faults taken into account are some of the most common on rotating machines such as unbalances, thermal bows, fatigue cracks and radial and angular misalignments of couplings.

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This paper is concerned with the application of fuzzy neural networks to fault diagnosis systems for rotary machines. In practical fault diagnosis, it is very difficult to improve the recognition rate of pattern recognition, especially when the sample data are similar. To solve these difficulties, a fault diagnosis system using fuzzy neural networks is proposed in this research. A fault diagnosis system with fuzzy neural networks is based on a series of standard fault pattern pairings between fault symptoms and fault. Fuzzy neural networks are trained to memorize these standard pattern pairs. Unlike other neural networks, fuzzy neural networks adopt bi-directional association. They make use of information from both the fault symptoms and the fault patterns, which can improve recognition rate greatly. When an unknown sample becomes the input for a trained fault diagnosis system, the fault diagnosis system can make fault diagnosis by bi-directional association of fuzzy neural networks. Through experiments with a rotor testing table and applications in monitoring and fault diagnosis of water pump sets of oil plant, it is verified that fuzzy neural networks have a well distinguished ability and are effective to perform fault diagnosis of rotary machines.

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In this paper, we propose a new approach on nonlinear preview control with fuzzy logic. Because preview control can decrease not only the overshoot but also the control energy, there have been many approaches on preview control. However, as these approaches are based on linearized models(18), they cannot get a good result when they are applied to nonlinear plants. So we propose a fuzzy preview control to compensate the nonlinear properties of plant. Here, first, a simple Fuzzy Logic Control (S-FLC) with single-input-single-output is introduced. This kind of Fuzzy Logic Control can decrease the number of rules and make the fuzzy reasoning be more quickly. Second, using the I-PD control system proposed by T. Kitamori, fuzzy I-PD control's scaling factors are designed with matching technique. Then to compensate nonlinear properties of plant, two parameters are injected and optimized with Genetic Algorithm (GA). Third, a new designing scheme of preview control element using fuzzy theory is proposed and the preview control element is optimized with GA under a performance criteria. Being designed on the nonlinear model, it will make the fuzzy preview control be more suitable to nonlinear plant. At last, some experiments with a two-cascaded tank system illustrate the efficiency of the proposed approach.

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This paper deals with modeling and control of electrostrictive polymer (EP) for endoscopic microcapsule. The EP is so flexible that we considered it as a flexible membrane. And the EP has time variant variable. It is the reason that the elastic modulus of EP is very small and changes during deformation of EP. But an electronics, polymer science and mechanics must be considered at the same time to have exact model of EP. So a control algorithm was used. The control algorithm must overcome the limit of modeling. So the algorithm of adaptive fuzzy algorithm was used to control the actuator exactly.

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The development of ultraprecision positioning technology is urgently required with the incessant demand for higher accuracy in high technology manufacturing. In this study, therefore, a linear pneumatic-driven ultraprecision table is built; and, a velocity compensator is designed to overcome the stick-slip effect of the pneumatic table. The velocity compensation signal is directly added to the conventional PD and Fuzzy controller to control the table, respectively. This method is effective not only to overcome the stick-slip phenomenon of the cylinder but also to improve the positioning accuracy of the pneumatic servo system. The experimental results have shown that the table has the positioning accuracy of 20nm.

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We propose a design method for robust modified repetitive control systems without solving the µ synthesis problem using a two-step design method. The basic idea of the two-step design method is that if the modified repetitive control system is robustly stable, then the modified repetitive controller must satisfy the robust stability condition. The parameterization form of all robustly stabilizing controllers for the plant are obtained using an H_∞ problem based on either the Riccati equation or on a Linear Matrix Inequality. Using the free parameter of the parameterization, we can design robust modified repetitive control systems. The necessary condition for the existence of robust modified repetitive controllers is given. Using the proposed method, the limitation on the low pass filter in the repetitive controller that exists in the robust repetitive controller is clarified. A numerical example is used to illustrate the effectiveness of the proposed method.

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We construct a handing over robot system with consideration of individual preferences. In this robot system, a human (cooperator) can adjust motion characteristics of planar two-degrees-of-freedom robot to satisfy his or her individual preferences. The robot recognizes the shape of the cooperator's hand as the order using image processing. Then, the robot changes the motion characteristics, such as the maximum velocity, the position of the velocity peak, the handing over position and the initial position, according to the cooperator's order (that is preference). By accomplishing the adjustments, the handing over motion of the robot will become the most comfortable for the cooperator. Furthermore, this proposed robot system uses a bell-shaped velocity pattern based on the minimum jerk model, which can reproduce the point-to-point motion of human hands. Therefore, the motion of this robot becomes similar to human's hand motion, and a more human friendly robot can be realized.

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This paper presents a closed inverse dynamic formulation by the Lagrangian approach in terms of quasi-coordinates for the general 6-6 Stewart platform manipulator. It is shown that the symbolic computation using quasi-coordinates is most efficient as the structure undergoes finite rotations. The derived inverse dynamic equations are demonstrated to be well structured, straightforward, and suitable for computer programming. Numerical examples are finally carried out to validate the approach. Results of simulation are justified to be useful in the design and dynamic control of the manipulator.

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Uninterrupted power supply has become indispensable during the maintenance task of active electric power lines as a result of today's highly information-oriented society and increasing demand of electric utilities. This maintenance task has the risk of electric shock and the danger of falling from high place. Therefore it is necessary to realize an autonomous robot system using electro-hydraulic manipulator because hydraulic manipulators have the advantage of electric insulation and power/mass density. Meanwhile an electro-hydraulic manipulator using hydraulic actuators has many nonlinear elements, and its parameter fluctuations are greater than those of an electrically driven manipulator. So it is relatively difficult to realize not only stable contact work but also accurate force control for the autonomous assembly tasks using hydraulic manipulators. In this paper, the robust force control of a 6-link electro-hydraulic manipulator system used in the real maintenance task of active electic line is examined in detail. A nominal model for the system is obtained from experimental frequency responses of the system, and the deviation of the manipulator system from the nominal model is derived by a multiplicative uncertainty. Robust disturbance observers for force control are designed using this information in an H_∞ framework, and implemented on the two different setups. Experimental results show that highly robust force tracking by a 6-link electro-hydraulic manipulator could be achieved even if the stiffness of environment and the shape of wall change.

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This paper studies the output tracking and almost disturbance decoupling problem of nonlinear control systems with uncertainties. The main contribution of this study is to construct a controller, under appropriate conditions, such that the resulting closed-loop system is valid for any initial condition and bounded tracking signal with the following characteristics: input-to-state stability with respect to disturbance inputs and almost disturbance decoupling, i. e., the influence of disturbances on the L₂ norm of the output tracking error can be arbitrarily attenuated by changing some adjustable parameters. The fundamental theoretical approaches are the differential geometry approach and the composite Lyapunov approach. Two examples, which cannot be solved by the first paper on the almost disturbance decoupling problem, are proposed in this paper to exploit the fact that the tracking and the almost disturbance decoupling performances are easily achieved by the proposed approach. In order to demonstrate the practical applicability, the paper has investigated a pendulum control system that cannot be solved by some existent approaches.

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Robust asymptotic stability for a class of uncertain systems with multiple time delays is considered. Lyapunov theory and linear matrix inequality (LMI) approach are applied to solve the stability problem for such systems. New delay dependent criterion is derived to guarantee stability for the systems. Some numerical examples are given to demonstrate that our robust stability condition is less conservative than those reported in the recent literature.

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An analytic algorithm for simulation of discontinuous stick-slip friction is presented in this paper. In this algorithm, a two-stage integration technology is proposed to resolve the discontinuity of the friction model at zero velocity. Two types of the Coulomb friction models, the static+Coulomb friction model and the exponential Coulomb friction model, are evaluated. A procedure to estimate the Stribeck velocity, which characterizes the exponential Coulomb friction model, is also presented in this paper. A closed-loop position-control system is implemented to study the stick-slip motion and to verify the simulation results. The experimental and simulation results reveal that the exponential model is more verisimilar in representing the low-velocity feature of Coulomb friction.

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When developing a fuzzy diagnosis system for machinery conditions, the relationship between fault symptoms and fault categories must be defined for fuzzy inference. However, it is not easy to determine the fault symptoms by which all fault categories can be distinguished perfectly and automatically. In order to resolve this problem, we proposed: (1) a new fuzzy diagnosis method called “sequential fuzzy diagnosis”, and (2) an identification method of the membership function of the symptom parameter by possibility theory. The efficiency of the above methods was verified by applying them to the rolling bearing diagnosis system and others. In the system of rolling bearing diagnosis, the symptom parameters are calculated by “goodness of fit” with spectrum analysis. The results of sequential fuzzy diagnosis show the correct conclusions when inputting field data to the system.

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Insertion assembly of polygonal pegs exhibits distinct mating process compared to that for conventional round pegs and holes. Their inherent orientation characteristic increases the degree of complexity of the assembly tasks and limits completion of the insertion assembly. This paper is devoted to analysis of motion behavior of the polygonal peg-hole insertion to clarify constraint conditions for successful insertion assembly. Effective regions for possibly successful insertion assembly on the chamfer surface will also be presented. Therefore, appropriate manipulation strategies can be concluded and automated polygonal insertion assembly becomes realizable in the future.

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Screw motion primitives considerably extend the commonly used rotations and translations, but retain their representational conciseness and specific geometric properties. Each piecewise-screw motion is specified in terms of a sequence of key poses of the object that it interpolates at user controlled time values. The resulting piecewise-screw motion is unique and coordinate system independent. Also, the motion is independent of the manner in which the key-poses were specified. Although any two arbitrary poses may be interpolated by an infinite of motions we advocate screw motions for their simplicity, uniqueness and computational advantages. We present a new and efficient algorithm for constructing the boundaries of swept volumes created by moving polyhedra in screw motions. The algorithm takes a generate-and-test approach by computing the candidate surfaces of boundaries and trimming them after applying the point-in-sweep test. Examples are provided to show the efficacy of the algorithm.

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The tested knife material here is mainly SUS420J2 (a kind of stainless steel). This kind of knife is very popular for daily use. From SEM observation of the initial state of the knife-edge tip after the burr removal treatment, we find either some burr and/or a micro-groove, or no burr and no micro-groove along the edge-tip. In order to abrade intentionally, the edge of a knife is repeatedly rubbed perpendicularly to the surface of a Japanese cypress woodblock using the durability-testing machine. During this rubbing process, the abrasion and/or crushing of the edge tip are observed by SEM in detail. The frictional load between the knife-edge and the woodblock is measured. Using the cutting-test machine, the cutting performance of the abraded knives is evaluated by the number of cut pieces of paper. It is discovered that the groove evolves and grows on the edge tip with abrading operation. Moreover, it is concluded that both micro-sidewalls of the groove play a role as cutting edges (i. e., the secondary edge) and this secondary edge and the groove width govern the durability of cutting performance of the knife. Especially the groove width governs it most. These conclusions are also valid for the knives made of other materials such as SUS410 and SUP10.

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In this study, the influence of graphite particles (number of graphite particles) in austempered ductile iron (ADI) on tool wear and finished surface roughness was investigated, using TiN and (Al, Ti)N coated high-speed steel cutting tools in hobbing. The experiments were performed using a fly tool of the same geometry as that of one blade of a hob, at the cutting speed of 47m/min in dry cutting. As a consequence, the following points were clarified: (1) ADI having an average number of 284 graphite particles per 1mm² (the average diameter of 28.0µm) showed a good machinability without causing tool failure. The tool life was improved when using the (Al, Ti)N coated tool, and the finished surface roughness R_y was 3.5µm at the end of cutting. (2) It was suggested that the adhesion of deposited metal on the rake face influences the tool failure which occurred when cutting ADI. (3) The interrelation between the center wear and the surface roughness was recognized.

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This research is to develop a new method to enhance the bending load capacity of gear tooth using asymmetric tooth profiles. For many power transmission devices operate in one direction, only one side of the tooth surfaces (the front of tooth) is in mesh. So the tooth is not necessary to be a symmetric form. The dimensions of the front and back profiles of the tooth could be designed individually. The back profile of the tooth that does not contact in running could be decided to decrease the maximum tensile stress at the root of tooth. Different standard pressure angles are used in the front and back profiles of an asymmetric tooth. Tooth root stress and bending stiffness of the asymmetrical tooth for several combinations of standard pressure angles were calculated by the use of finite element method. Based on the results of calculations, it is clarified that a larger standard pressure angle in the back profile of tooth makes the tooth root stress decrease remarkably and bending stiffness of tooth increase, but dose not change the load sharing ratio.

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A method for predicting gear noise from the vibration step to the sound-generation step of a complete gear system, including a gearbox, was developed. This method consists of three separate steps: gear-vibration analysis by an in-house program, gearbox-vibration analysis by an FEA program, and sound-radiation analysis by a commercial software. By using this method, it can obtain the vibration behavior of the gear and gearbox, and the distribution of the sound-pressure around the gearbox and identify the areas from which noise radiates intensely. To validate the method, we measured the displacement of a gear shaft, the acceleration of points on the surface of the gearbox, and the sound-pressure levels around the gearbox. The measured results agreed well with the corresponding calculations. According to the calculated noise, a low-noise gearbox was designed by adding ribs near the antinodes of the gearbox's vibration mode.

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