A damping vibration experiment was carried out on an actual shell structure (a PC cylindrical shell) to clarify damping characteristics of the shell structure, and also to aid in preparing a data base on damping ratios of shell and spatial structures for use in dynamic response analysis. The experimental methods used were microtremor observation and a human excitation experiment. The analytical methods used for evaluating damping ratios were the random decrement technique (RD technique) and the half-power method.

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For civil engineering structures damage will inevitably occur and continuously accumulate during their service life. As damage develops, both, the physical properties, such as mass, stiffness and damping, as well as the dynamic properties of a structure change. It is therefore feasible to utilise measured dynamic quantities such as time histories, frequency response functions (FRFs) and modal parameters from structural vibration to detect damage. Vibration based damage identification is essentially a form of pattern recognition problem, which looks for the discrimination between two or more signal categories, e.g. before and after a structure is damaged. Artificial neural networks are capable of pattern recognition, classification, signal processing and system identification, and are therefore an ideal tool in complementing dynamic based damage detection methods. Likewise, principal component analysis (PCA) has pattern recognition abilities and is capable of data reduction and noise filtering. Together, these two techniques are able to extract enhanced damage fingerprints from vibrational data and assist in delivering robust and accurate damage identification. This paper presents a dynamic based damage identification method that utilises FRF data to identify boundary imperfections of a two-storey framed structure. The proposed method utilises artificial neural networks to map changes in FRFs to boundary condition damage of the structure. In order to obtain suitable patterns for neural network inputs, PCA techniques are adopted to reduce the size of the measured FRF data. Further, patter recognition and noise filtering capabilities of PCA enhance damage fingerprints in FRF data and thereby improve damage identification results. A hierarchy of neural network ensembles is created to take advantage of individual characteristics measured from different sensors. The method is applied to laboratory and numerical models of two-storey framed structure. Boundary damage is simulated by changing the condition of individual joint elements of the structure from fixed to pinned. In total, ten different types of boundary damage are investigated, i.e. four single and six multiple joint changes. From the numerical and the laboratory structure, FRF data are determined and compressed utilising PCA techniques. The PCA-reduced FRFs are then used as input patterns for training and testing of neural network ensembles predicting the type of boundary damage.

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Many houses were destroyed in destructive earthquakes in the world. Then, control of seismic response of house is important for protection from destruction. In this paper, two story houses are focused on and oil dampers of some shapes are proposed. Oil damper is connected to the ceiling of the first story and the foundation. The spherical damper, the rectangular parallelepiped damper and the cylindrical damper with silicon oil are proposed. The effectiveness of the dampers is examined experimentally. It is concluded that the peak of the frequency response function of the first vibration mode decreases and the damping ratio increases when the dampers are used. From simulation method using the analytical model, it is found that the maximum response decreases when the dampers are used.

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This paper discusses the characteristics of the dynamic response of a structure with simple semi-active control system. The control system consists of controllable dampers that are set at each inter-story level. At first, a proposed control method of the damper force was examined. The method, which based on potential energy of inter story, controls the hysteretic shapes of the damper. The proposed algorithm aims at reducing a displace response without increasing an acceleration response. To examine the performance of the proposed control scheme under seismic excitations, numerical analysis based on equivalent linearization method were conducted. Then extension of this control method to a multi-story building is discussed. As a result, it is confirmed that the MDOF model was well controlled by the proposed methods under seismic excitations.

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An integrated design method of structural and semi-active control systems for civil structures is presented. The Vibration Control Device (VCD) that has been developed by authors is used as the semi-active control device. A new semi-active control method, which is referred to as the Inverse Lyapunov Approach, is proposed. In the Inverse Lyapunov Approach we firstly assume a bang-bang type semi-active control law based on an unknown Lyapunov function. The Lyapunov matrix that defines the Lyapunov function is optimized so that quantitative performance measures on vibration suppression of civil structures are optimized. The control design problem of the semi-active control law in the Inverse Lyapunov Approach results in an optimization problem of the Lyapunov matrix to construct the Lyapunov function. In the present study, in addition to the design parameters to determine the Lyapunov matrix structural design parameters, the stiffness between neighboring two floors of the structural system itself and the parameters of the VCD are optimized simultaneously so that the structural responses subject to recorded and/or artificial earthquake waves are optimized in the sense of the specifications on vibration suppression of civil structures. We adopt the Genetic Algorithm (GA) to get the optimal Lyapunov matrix and the structural design parameters.

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This paper presents a 6 force component balance to be used in wind tunnel vehicle model tests. Several parallel plate force sensors are built in the balance, and strain gauges are used to measure strain produced by 6 force components of loads. 24 strain gauges are arranged to 6 full bridges. Each bridge outputs voltage in proportion to one of the 6 force components. Output gains are estimated through theoretical and FEM calculations. Calibration result shows that the balance realized high linearity, small crosstalk and small hysteresis performance. Single component load calibration results agree with FEM estimations, and the critical frequency of the system including the balance and a vehicle model is about 28 Hz, therefore substantial ability to measure nonsteady aerodynamic forces is achieved.

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Rubber-like materials have strong nonlinearities in dynamic and static stiffness and damping characteristics. To confirm all of the nonlinearities of rubber material, a large number of tests must be carried out. Therefore, the evaluation method with which stiffness and damping characteristics including several nonlinearities of rubber element can be estimated by a few kinds of material tests is greatly useful. The purpose of this study is to establish an evaluation method in which the nonlinearities of rubber-like material caused by loads applied in both the shear and compression directions are taken into consideration. As the first step of this study, the material stretch test, the static load test and the FEM analysis were carried out to verify the nonlinear characteristics of the static stiffness caused by loads applied in both the compression and shear directions. It was verified that the static compression stiffness dependency on the initial shear deformation and the static shear stiffness dependency on the initial compression deformation can be expressed by the FEM analysis. To accurately express the force-displacement relationship, the estimation methods of a strain level which dominates the stiffness of a rubber isolator should be investigated.

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This paper presents two different response evaluators which evaluate the response of the system and decide the control input to the system. The characteristics of the response evaluators were designed based on the source region and ground motion of earthquakes. They were applied to a base isolated structure with a semi-active oil damper whose damping coefficient has large or small values. The response evaluators were designed by a multilayer neural network which uses the building response and the peak ground velocity as input data and outputs a switching signal for the damping coefficient as output data. A genetic algorithm was used to adjust the neural network parameters which determine the performance of the response evaluators. A computer simulation was carried out using several kinds of earthquake motions, and absolute acceleration and displacement of each story, which are in a trade-off relationship with each other, are reduced to intermediate values of the response in the case where constant damping coefficients are large or small. From the result of the simulations, the control effect of the response evaluators was verified.

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In this paper, a new vibration control device called pendulum-type tuned mass damper (P.T.M.D) is proposed to reduce an ordinal house vibration. In recent years, three or four stories houses are built increasingly in the urban areas to obtain wide living space. These houses are subjected to a problem caused by the traffic vibration, because a dominant frequency of the traffic vibration is coincident with the natural frequency of these houses. Although tuned mass dampers (T.M.D) are considered to solve the problem, it needs to prepare a large mass on the top floor of these houses in order to obtain effective vibration reduction. On the contrary, P.T.M.D can be placed between the first and second floor and it acts effectively on the principle of lever mechanism, since an action of the mass is expanded. A semi-optimal design approach for the P.T.M.D is described, while it has an adjustable mechanism to adapt to various specifications of these houses. Effectiveness of the P.T.M.D is demonstrated theoretically and experimentally by controlled results using frequency, time and seismic responses. Also this paper shows that the P.T.M.D is effective against random vibration like earthquakes.

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Magnetorheological fluid (MRF) has received significant attention lately and MRF based devices have been proposed for structural control applications in recent years. The unique characteristics of MR fluid lies in its abilities to reversibly, repeatedly and instantly change from a free flowing liquid to a semi-solid state when exposed to a magnetic field. The electric power required to drive the MR devices can be easily provided by a battery. Possessing such unique properties, MR fluid based devices, such as MR damper, have become promising candidates in the semi-active control for civil structure applications. However, most of the published research has focused on application of MR dampers instead of exploring other type of MR devices. In addition, MR based devices exhibit complex nonlinear hysteresis behaviour and thus making their modelling a challenging task. In this paper, a novel MR fluid based device, namely MR pin joint, is proposed as smart structural members in development of an intelligent civil structure that can suppress unwanted vibrations to ensure safety and serviceability of the structure. After design and fabrication, experiments have been conducted to characterise dynamic behaviours of the new device under different harmonic excitations with various input currents. Test data shows that the MR pin joint possesses a unique behaviour in the moment-angular velocity plot. A hyperbolic hysteresis model is proposed to model such unique behaviour. The investigation presented in the paper explores dynamic performance of MR pin joint. Finally, a parametric model is developed following the investigation on the correlation of coefficients in the proposed model with the loading conditions and applied currents.

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Magnetorheological (MR) dampers are a promising alternative structural active actuators as they provide adjustable damping over a wide range of frequencies without large power requirements. However, the complex dynamics that characterizes these devices makes it difficult to formulate control laws based on the MR damper model. Instead, many semiactive control strategies proposed in the literature have been based on the idea of "clipping" the voltage signal so that the MR damper force "tracks" a desired active control force which is computed on-line. With this idea many algorithms have been proposed using, among others, techniques such as optimal control, H_∞, control, sliding mode control, backstepping and QFT. This work presents a semiactive control strategy based on the same idea of "clipping" the voltage signal but using a simpler PI design. The proportional and integral gains of the controller are calculated so that the controller guarantees stability, minimization of the closed loop response and robustness against modeling errors. Effectiveness of the control strategy is compared to some others techniques and passive cases as well. Simulation results shows that this simple strategy can effectively improve the structural responses and achieve performance index comparable to that of more complex algorithms.

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This paper studies the applicability of a quite novel methodology of experimental testing so-called Real-Time Dynamic Substructuring Test (RTDST) in the assessment of protection systems for natural hazards mitigation. RTDST allows testing critical components of the structure at full-scale under realistic extreme loading conditions. Only those components where the nonlinearity is concentrated on are physically tested, whilst the remainder of the structure is simulated numerically. In this technique, unavoidable delays associated with the transfer system dynamics affect the signal of experimental measurements which is fed-back to the numerical model. It may cause instability during the test. This work is focused on testing a passive control system based on nonlinear fluid viscous dampers. Throughout explicit stability analyses, we present a complete set of closed-form expressions to describe the dynamics of the main complex delay-induced phenomena exhibited for this system when a delay is considered in the damper response. The theoretical results were confirmed numerically with good agreement.

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In this paper, the design of a nonlinear adaptive controller for a single-rotor type small helicopter is described. First, the configuration of small autopilot device, which can be applied any single-rotor helicopters is presented. We construct the hardwear of the autopilot device based on FPGA (Field Programmable Gate Array). In the case of small helicopter, payload limitation of them is so tight. Therefore, we have to use only small and light weight sensors and computer for the control. All sensors we use are light enough and low cost, the total weight of the autopilot device with box is about 300 g. Next, the nonlinear adaptive attitude controller is designed by using backstepping method. We guarantee that the attitude of the helicopter can follow arbitrary time varying reference attitude, even when the helicopter model has the parameter uncertainty, such as inertia moment or aerodynamic uncertainties. Finally, the effectiveness of the adaptive attitude controller is verified by simulation with parameter uncertainties.

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Flexible spacecrafts have been required to agile and precise attitude switching maneuver recently. For this requirement, the controller of the flexible spacecrafts is required to be robust against high-frequency unmodelled uncertainty and to have high performances of motion and vibration control. In this paper, the attitude controller of the flexible spacecrafts is designed by nonstationary frequency-shaped robust control based on the differential game theory. The weightings of the proposed controller are designed to be replaced high-frequency unmodelled uncertainty and enable the controller to suppress the spillover instability. The proposed controller generates optimal input torques to control agile and precise attitude switching maneuver of the spacecraft by the weightings of the state vector which are designed in the time domain. Several simulation results show the effectiveness of the proposed controller.

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It has been expected to clarify the mechanism of free flying sports such as aerial ski, diving contest and so on. The attitude motion in those sports is constrained by the conservation of angular momentum, and the aerial players are, thus, a kind of nonholonomic, under-actuated mechanical systems with initial angular momentum, in which the number of the generalized coordinates is more than the number of control inputs. Because their dynamics is complicated, it is difficult to control them and grasp their motion intuitively. In addition, because zero gravity environments are hardly realized on the ground, it is difficult to carry out experiments with the actual machine for a long time. This paper addresses numerical simulations and experimental set up for attitude control by a feedback control strategy for 3-D free-flying robots with non-zero angular momentum, in which the attitude of the main body of the robot and configuration of the robot can approach the desired states. Contrary to past studies that considered only the final attitude, in this study, we consider situations to make the configuration of the robot transit some intermediate states to emulate performance in aerial sports.

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The accuracy of small and low cost GPS is insufficient to provide data for precisely landing Micro Air Vehicles (MAV)s. This study shows how a MAV can land on a small targeted landing site by using sensors rather than imprecise GPS data. This paper describes a proposed movable range finding sensor system for measuring the environment and an algorithm of position measurement. This range finding system consists of four Infrared (IR) sensors, four servo motors and one ultrasonic sensor. In order to measure the MAV's position, the sensor system vertically swings each IR sensor using the servo motors and these IR sensors detect the edge of landing target. And this sensor system calculates the position from the measured edge direction and the ultrasonic altitude. Additionally, experiments of autonomous hovering over a 52cm × 52cm table and autonomous landings were carried out indoors using the proposed sensor system. Our experiments succeeded, and as a result, the MAV kept flying horizontally within a 18cm radius circle, and then it landed on the table from a height of 50cm. The IR sensors were selected because of the payload limitations of small MAVs. If the MAV's payload capacity were higher than a laser sensor would be used since lasers can operate better in sunlight than IR sensors and also they tend to have longer scanning ranges and are more accurate.

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MAV (Micro Air Vehicle) can be used for many applications such as the investigation of inhospitable environments, regions contaminated by nuclear pollution or hazardous material and other inaccessible areas. For such kind of purposes, a small machine that can autonomously fly seems to be appropriate. It can be used no matter how complicated geographical features are, since the air is relatively free from obstacles. MAV is not flown by a radio controller. It can autonomously fly and accomplish target duties. In our laboratory we select a Quad-Rotor MAV as our platform, and achieved autonomous take-off, landing, hovering, way-point navigation, and vision-based navigation flight, however, the payload of our current platform is low (about 500grams), and the flight duration is only about 10 minutes. To overcome these obstacles, we designed a Six-Rotor type MAV with 770mm of diameter, 1.9Kg of weight, 1.5Kg of payload and 12 minutes of flight duration(without payload). To achieve autonomous flight, we install our developed autopilot system and design model-based controller (attitude control, velocity control and position control). In this paper, we present the main design considerations which are essential for the construction of Six-Rotor type MAV and controller design technique.

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Position control, namely proportional-derivative (PD) control, is a quite common application on controlling of electrical motor. Proper application and tuning of this control algorithm can bring many efficiency and performance benefits with the motor controlling. However, electrical energy consumption of the control method for an electrical motor was few studied up to now, even the problem is very important for practical application. In the paper, an PD tuning algorithm of the position control was studied for saving energy consumption and maintaining high response performance for an electrical direct-current (DC) motor control. Firstly, response performances in time domain are analyzed by tuning of PD parameters for a position control system. Sequentially, electrical energy consumption of an electric DC motor in the position control system is discussed by simulating study. Finally, a multi-objective scheme to determine PD parameters is developed for saving energy consumption of DC motor, and high response performances are also achieved by the position control method.

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In the next generation of baby carriages, better comfort for both the baby as well as the parent is required, in addition to safety concerns. To develop a comfortable baby carriage, fundamental data are required about the types of vibrations babies prefer and find pleasant. In order to obtain such data, it is necessary to develop a shaking table for baby carriages having nonlinear characteristics, and develop a control system in which the shaking table follows a desired input characterized as a random wave. In this study, a single axis shaking table for a baby carriage is studied. The table under the right front wheel of the baby carriage is shaken according to a desired waveform. The proposed control system is a proportional controller with an outer feedback loop based on a discrete-time sliding mode controller, i.e., an input waveform shaping filter. The performance of the controller is evaluated using a numerical simulation. The results show that although the shaking table displacement could follow the desired waveform by using only the proportional controller, the robustness of the response to disturbance was weak, and also that the robustness could be improved with the addition of the proposed input waveform shaping filter. The effectiveness is demonstrated using a control experiment. The results of this experiment show that the mean square error of the table displacement when using proportional controller along with the input waveform shaping filter was about 75% compared with the error when using only the proportional control.

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In this paper a method of suppressing vibrations in an industrial rolling process with varying rotational frequency is presented. The vibrations in a rolling process are problematic as they do not only cause structural fatigue on the machinery, but also deteriorate the quality of the end product. The traditional approach for this type of a problem would be to avoid the critical frequencies of the process by changing the rotation speed of the reel, thus decreasing the vibrations. However, in practice this is hard to achieve as the radial velocity of the reel should be constant, while rotation speed of the reel varies depending on the width of the reel. The changes in radial velocity are typically not allowed as the rolling process is usually part of a larger process, where change in rotation speed affects the whole process. This paper introduces a generic modified LQ-control law to tackle the problem. This control design was designed in a previous ACRVEM-project (Active Control of Radial Rotor Vibrations in Electric Machines) and has been successfully used in suppression of radial rotor vibrations in electric drives, resulting in 90% damping of the vibrations. The major drawback of the controller has been the limitations due to its linear nature; the control is applicable only at a certain predefined rotational frequency, and outside this frequency the controller becomes unstable. In order to resolve this problem, a nonlinear optimal state-feedback controller based on continuous gain scheduling is introduced. This modification of the original controller is capable of suppressing the vibrations over the whole operational frequency range. In this paper the modelling and identification of the rolling process is first discussed. After the model has been obtained the control design procedures for both linear and nonlinear controllers are presented in detail. The performances of both controllers are analyzed in extensive simulations. Finally the simulation results are validated by implementing the designed controllers in the actual rolling process. It will be shown that this control methodology is highly effective for this type of vibration damping problems resulting in over 90% decrease in the vibrations over the whole frequency range of rotation.

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We verified through experimentation on five carts connected in series by four springs that a control method for always efficiently exciting a multi-degree-of-freedom system at a resonance frequency. When an excitation point corresponds to a vibration detection point in a multi-degree-of-freedom system, a phase lag at a given resonance frequency and the phase lead at an anti-resonance frequency alternately appears in the vibration characteristics, and the phase lag is 90° at all resonance frequencies. Therefore, if a controller with a 90° phase lag and a constant gain in a wide frequency range is used, self-excited vibration is generated at all resonance frequencies. The local feedback controller for each actuator consists of a self-excited vibration controller that is the sum of the integral control of the displacement and the positive velocity feedback control, a saturation element that limits excitation force, and a negative velocity feedback controller that provides active damping. We used a four-degree-of-freedom system consisting of five carts and four springs in our experiment. Four voice coil motors controlled by the local feedback were used to generate self-excited vibration at all the resonance frequencies of a four-degree-of-freedom system. The self-excited vibration mode can be freely switched on by changing the frequency of the sine wave that is added as an electric disturbance. A system using many actuators with local feedback control, i.e., decentralized control, driven at a resonance point with a natural frequency is excellent in its adaptability to the environment, in its extendibility, and in its fault tolerance.

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In this paper, we have developed an analysis and synthesis method for mixed-sensitivity problems in sampled-data positioning control systems. To avoid complicated calculations, this method uses frequency responses of the controlled object and the digital controller for calculating the characteristics of the control system. This paper shows relationships between the sensitivity function and complementary sensitivity function for the mixed sensitivity problem in a sampled-data positioning control system. This paper also addresses the mixed sensitivity for multi-rate control systems that include an interpolator, a multi-rate filter, and a multi-rate hold. Simulations and experiments conducted on the sampled-data positioning control system of a head-positioning control system in a hard disk drive verify the validity of the proposed method.

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In this paper the eigenfrequency of a Helmholtz resonator, which is used to reduce noise of machines or structures, is actively controlled in simulation. The eigenfrequency of a resonator is controlled to the desired value by PID control of the boundary condition of a resonator. The gains of PID controller are obtained by the model matching method. The obtained gains are substituted in the transfer function of a resonator and the Bode diagrams are drawn by simulation. As a result the position of the peak frequency of a diagram is agreed well with the designed eigenfrequency.

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This paper deals with a research on vibration control for suspended load of crane utilizing a variable-pitch propeller thrust. Vibration suppression of crane load suspended by hoisting rope is an important issue to speed-up crane operation. In this study, a novel vibration control system using a variable-pitch propeller thrust as an actuator is presented. An experimental system using a simple pendulum composed of a load suspended by four thin strings and a variable-pitch propeller with a motor. The propeller thrust decelerates the oscillation of the pendulum. The basic property of the system is investigated experimentally and is its effectiveness is confirmed.

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Handling devices are required to operate with a wide variety of materials and loads, and their dynamics often leads to incorrect positioning. It is nearly impossible to produce a dynamic model that takes into account all possible combinations of handling device and load in order to design an error-free control system. However, adaptive control methods can be effective in dealing with a plant with unknown dynamics or variable parameters. The Minimal-Control-Synthesis (MCS) method is one such adaptive control method and does not require knowledge of the plant dynamics. In this paper, we experimentally demonstrate MCS control of a one-degree-of-freedom table device that is driven by a linear actuator. A comparison is made between the Proportional-Integral-Derivative (PID) and MCS control methods for four different configurations. The results show that MCS achieves faster device positioning and reduces the effects of nonlinearity.

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Continuous unloaders play an important role in handling bulk products at ports and so should be fitted with antiseismic devices to protect them in case of emergency by severe earthquakes. Continuous unloaders usually have a hinged-leg type structure and their posture changes over a wide range during operations. For the seismic design of continuous unloaders and to optimize antiseismic devices for them, these features must be taken into consideration and the dynamic behavior of unloaders under representative earthquakes must be clarified. This paper proposes an antiseismic device using linear ball bearing and laminated rubber bearings installed between the traveling gears and the fixed legs on the land side. To clarify the dynamic behavior of a continuous unloader with hinged-leg structure under representative earthquake excitations, experiments using a 1/15-scale model of an actual unloader, modal analysis and time response history analysis using the finite element method were conducted, and the performance of the proposed antiseismic device was investigated. The validity of the finite element analysis was evaluated by experiments using the 1/15-scale model, and the effects of posture on dynamic behavior were also studied in the analysis. The time history of the response acceleration near the total center of gravity and the response reaction force at leg points as well as the natural frequencies and modes were calculated and discussed.

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The purpose of this study is to develop a spreader for loading and unloading a container in unstable environments of the open sea. In order to overcome the swing of a spreader due to waves and wind, an auto positioning spreader was proposed with three degrees of freedom (DOF). By constraining a spreader on the top of a container, DOFs for the auto positioning were reduced from six to three in three dimensional spaces and therefore the auto positioning spreader was easily implemented. Virtual force algorithm employing six proximity sensors was proposed to control the remaining three DOFs of the spreader system. A RecurDyn dynamic model and a one to twenty scale model were developed and the effectiveness of the new spreader system introduced in this paper was verified in both numerical simulation and downscale model test.

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In this paper, a control scheme of a container crane that is installed on a small vessel, which is used for loading and unloading containers from a large vessel that cannot access a port because of shallow water, is investigated. Control objectives are to move a container to a desired position as well as to suppress the transverse vibration of the container under ship motions using nonlinear control. The control law guarantees the asymptotically stability of the closed-loop system. Simulation results are presented to demonstrate the efficiency of the proposed algorithm.

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A mobile harbor is a floating structure especially designed for loading and unloading containers from and to a large container ship. The purpose of this study is to develop a stacking guidance system (SGS) of containers in the mobile harbor, MH. The guidance system is an aid for loading containers with a wider opening for easier stacking of a container into a moving storage cell due to waves. Thus the system can provide an extra space through the expanded cell-guide. In order to determine the most effective inclination angle of the cell-guide, this study performed the dynamic analysis of the SGS equipped in the MH subject to fluctuations of the sea. The use of the cell-guide could increase the opening by 50% comparing to the case without it. The motions of the guidance system and a container loaded were calculated using ADAMS. The simulation results of the contact force between the two rigid bodies showed that a desirable angle of the cell-guide should be around 20 degrees from the vertical. This proposed SGS can considerably reduce the loading or unloading time, and will enhance the performance of the MH.

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This study proposes a new vibration control method using harmonically-varying damping. Previous research has demonstrated that resonance could be induced by the combination of a sinusoidal base excitation (not at the natural frequency) with harmonically varying damping. The amplitude and phase of the resulting resonance can be controlled through appropriate choice of variable damping. This finding is used herein for response control. A single degree-of-freedom structure excited by an external sinusoidal input disturbance is considered. An ideal variable damper is employed as a semi-active control device, in conjunction with a secondary base displacement, resulting in cancellation of the input disturbance. In this paper, an expression for the ideal damping required, as well as the secondary base displacement, are developed; the control performance is then confirmed through numerical simulation.

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In this paper, the nonlinear vibration behavior of a composite beam with embedded shape memory alloy (SMA) wires is investigated. The wires are embedded in the neutral surface of the beam. Using a variational formulation, the governing equations of motion and associated boundary conditions for the beam with extensible mid-plane are obtained. Considering mid-plane stretching in nonlinear analysis provides several unique advantages that cannot be obtained in linear analysis. It allows modeling damping due to pseudo-elasticity property of wires and the effect of vibration amplitude and initial conditions on the beam vibration characteristics. In this study, the constitutive relations of SMA are combined with elastic properties of the beam to derive governing differential equation of motion. Although there is no distinct damping term in the governing equation, the results show decrease in the vibration amplitude. Corresponding phase plane diagrams, as well as, the stress-strain curves for the SMA are obtained. The variation of damping with strain amplitude for different initial conditions is studied and the general features of the responses are found to be in agreement with the reported experimental observations.

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In a mechanical system, parameter uncertainties always exist due to several reasons such as manufacturing tolerances, manufacturing process irregularity and environmental change. For instance, mass, stiffness, damping coefficient and friction coefficient which are design parameters of a vibration system may have uncertain characteristics caused by such reasons. Therefore, for a reliable design of a vibration system, the performance uncertainty which results from the system parameter uncertainties needs to be estimated accurately. In this paper, a performance measure is defined for a nonlinear vibration system and a statistical method to estimate the performance uncertainty using the first order reliability method (FORM) is employed. It was found that the FORM could provide good results even if the system of concern is nonlinear. Compared to the results obtained by Monte Carlo Simulation (MCS), the accuracy of the FORM applied to nonlinear system was verified.

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This study presents a method of preventing disk brake squeal by managing the distributions of pressure and stiffness on the frictional contact surfaces of the disk and the pad. Self-excited vibration is shown to be the cause of squeal, and it is generated when the coupled vibration of the disk and the pad becomes unstable. A surface contact analysis model is used to examine the squeal generation mechanism. The model is composed of a disk that has one degree of freedom (out-of-plane direction) and a pad-caliper that has two degrees of freedom (rotational and translational). The frictional contact surface is expressed as a distributed spring (contact stiffness). Analyses using this model clarify that squeal is generated when the contact stiffness is larger on the leading side than on the trailing side. The measurements of dynamic stiffness between the disk and the pad clarified that the contact stiffness become hared when the thrust pressure for braking become large. A squeal test was executed with experimental apparatus that can adjust the pressure distribution on the frictional contact surface. Squeal does not occur when the pressure distribution is kept uniform over the contact surface. The experimental results and calculations show that squeal can be decreased by making an appropriate thrust pressure for braking and keeping the stiffness distribution over the frictional contact surface uniform.

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For the disc brake system, the couples of brake disc and brake pads were supposed to be multi-points contact, and the brake dynamic model with multi-points contact was established considered the semi-empirical theoretical model of the friction coefficient-relative speed curve, which was verified by the rig experiment. Based on the model, assuming that the initial DTV and SRO can be represented mathematically as sinusoidal functions, the influence of the order, maximum and the phase of the initial DTV and SRO on brake judder were discussed in detail using the evaluation indicators of the time-frequency characteristics and the root mean square of the BPV and BTV. The results show that the order of DTV produces the order of the frequency of the BPV and BTV with the angular velocity; BPV has the stronger sensitivity of SRO and BTV has the stronger sensitivity of DTV, and the root mean square of the BPV and BTV has linear incremental relations with maximum of SRO and DTV; the phase of the SRO influents the BPV and BTV by changing the maximum of the DTV.

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A railway vehicle wheel experiences the problem of hunting motion above a critical speed, which is caused by the contact force between the wheels and rails. The resonance is one of flutter-type self-excited oscillations and the growth of the response amplitude can lead to the derailment of railway vehicles. In our previous studies, a stabilization control method using a gyroscopic damper is proposed, which does not make the yawing motion mechanically stiffer. In this paper, an improved method considering constant curve was proposed.

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In order to achieve sustainable transportation, "Low Emission & Energy Saving", "Safety & Security" and "Comfort & Healthy" are important target for study. The Advanced mobility research center was established in the Institute of Industrial Science, The University of Tokyo for the integrated research in April 2009. In this paper the following three topics which are related with the motion and vibration control are shown: Research and development of ITS (Intelligent Transport System), Advance Railway System, and Personal Mobility. For the topics of ITS, transportation experimental space with driving simulator collaborated traffic simulation and its application and electro magnetic suspension system will be shown. For the railway vehicle system, dynamics and control of railway truck including self-powered active vibration control, independent rotating wheel system and friction control between wheel and rail will be introduced. For examples of new type of vehicle motion control, the use of potential energy and gyro moment of flywheel battery are proposed. Finally future mobility mode in urban area, robotic two wheel vehicle is proposed.

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In this paper, series-type multiple magnetic suspension systems are studied. Several floators are suspended in series by one electromagnet in these systems. The nearest floator by the electromagnet is directly suspended by the electromagnet. The others are indirectly suspended by the attractive force due to the magnetization of the floators. The controllability and observability of series-type multiple magnetic suspension systems that have arbitrary number of floators, and in which the nearest floator by the electromagnet is detected are proved mathematically. A series-type multiple magnetic suspension system was fabricated in order to verify the analyses experimentally. In the fabricated system, magnetic suspension units that are equipped with a sensor and an electromagnet are used instead of the normal floators to study on various conditions. As the first step to realize the levitation of multi floators using one electromagnet and one sensor, a basic trial is carried out in the fabricated system.

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This paper describes a H_∞ loop shaping technique in a vibration control system. The prototype of the system consists of vibration body, two permanent magnets, two linear actuators, and control devices. The aim of this prototype system is to suppress the vibration by controlling the air gap between the magnet and the vibration body. The concept of the H_∞ loop shaping technique is to reduce the amplitude of the vibration signal in closed loop system when continuous sine wave disturbance was added. The numerical simulation results verify the effectiveness of the developed vibration suppression system.

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Active vibration control usually reduces vibration amplitude and mechanical energy of vibrating structure. In the situation, actuator of active vibration control system must remove energy from vibrating structure. However, the consideration is inconsistent with a common knowledge of active vibration control, active vibration control system needs external power supply to drive actuator. To find an answer to the inconsistency, power flow in an active vibration control system of a SDOF oscillator using a piezoelectric actuator has been investigated by authors analytically. The piezoelectric actuator is used because it has little internal loss and it makes easy to understand essentials of power flow in the active vibration control system. The investigation shows that the actuator is not consuming power from external source but removing and regenerating energy from the SDOF oscillator. Power consumption of the system is caused by energy loss of the amplifier to drive the actuator. The result implies that an energy regenerative active vibration control system can be realized by reducing energy loss of the amplifier. The energy loss can be reduced by using class D amplifier, high efficient amplifier based on switching operation of semiconductor devices, instead of conventional linear amplifier. The validity of energy regenerative active vibration control system using class D amplifier is shown by a numerical simulation. An advantage of proposing method compared to other energy regenerative vibration control methods and semi-active methods is that proposing method can use any controller used in ordinary active vibration control and can achieve the same control performance because difference between ordinary active vibration control methods and proposing method is only type of amplifier. In this paper, the validity and the advantage are confirmed by experimental comparison of power flow and control performance of two active vibration control systems using a conventional linear amplifier and a class D amplifier with the same controller and the same actuator.

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This paper proposes a noncontact magnetic suspension system for levitating two different weight iron balls simultaneously using flux path control method. In this system, the suspension force is generated by a disk-type permanent magnet, and controlled by varying the angle of the permanent magnet that is driven by a rotary actuator. In this paper, first, the suspension principle is explained, and the prototype is introduced. Second, the characteristics of this system are examined by some basic experimental results. Third, a model is created, and the controllability is proved, theoretically. Finally, the numerical simulation results of suspension are shown and discussed.

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This paper discusses on the feasibility of zero-power control in parallel magnetic suspension systems. In parallel magnetic suspension systems, multiple floators are suspend with a single power amplifier. The zero-power control has been used in magnetic suspension systems with permanent magnets providing bias flux. This control realizes the steady states where the attractive force produced by the permanent magnets balances the weight of the suspended object and the electromagnet coil current converges to zero. This paper shows that parallel magnetic suspension systems incorporating zero-power control can assign the poles arbitrary if the original parallel suspension systems are controllable. The feasibility of the zero-power control in a parallel magnetic suspension is demonstrated experimentally.

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A new variable flux-path unit is developed for flux-path control magnetic suspension with multiple magnetic sources. The authors have proposed the variable flux-path magnetic suspension system as a unique magnetic suspension system using permanent magnet. This system has ferromagnetic plates between a permanent magnet and a floator. The flux from the permanent magnet to the floator, and the attractive force acting on the floator can be adjusted by the motion control of the control plates. Stable suspension and 2-DOF control with a single magnetic source was achieved. However, the horizontal control force was much less than the vertical control force. In this paper, flux-path control magnetic suspension with multiple magnetic sources is proposed. An experimental apparatus with a variable flux-path unit is developed for realizing multiple-magnetic-source systems. Basic characteristics of the apparatus are measured. Stable levitation is achieved by applying PD and PID controls. In addition, stable levitation with zero-power control is also achieved.

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New flux concentrated hybrid (HB) type radial and axial magnetic bearings are proposed in this paper. It is intended to use ferrite permanent magnet (PM) for producing high bias flux. For this purpose flux concentrated PM arrangement is used. The capability of proposed magnetic bearings is designed using commercial FEM code "ANSYS". The experimental setup is fabricated and tested. The results show high possibility with less expensive PMs. Especially axial magnetic bearing is very strong and has almost the same diameter of the radial bearing core which means easy for manufacturing and maintenance.

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This paper presents a method of increasing the load capacity of magnetic suspension systems. The limits of coil current and suspension gap determine the load capacity. In PID-controlled systems, the displacement is kept zero and the coil current increases when load is added to the floator. In contrast, the current is kept zero and the gap decreases in zero-power controlled systems. As a result, the load capacity is determined by the current limit in the former and the gap limit in the latter. It can be increased by switching them each other. The switching stiffness control is applied for this purpose. Experimental results demonstrate the operating range is extended almost twice.

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This paper mainly adopts robust control to realize a speed controller for sensorless permanent magnet synchronous motor (PMSM). To control speed, the robust control estimator is used to estimate the motor back-electromotive force (back-EMF) and then estimate the magnetic pole angle θ^^〜_e corresponding to motor rotation, as so to send a feedback to the current loop for vector control. This method further converts the magnetic pole angle into the rotor speed for speed control. In the system of the motor control loop, due to motor parameter uncertainty and external load interference, the motor angle estimation error cannot be guaranteed to be converged within a tolerable range, thereby causing system instability. In order to improve estimator robustness, the H∞ observer method is derived to realize the speed controller for sensorless PMSM. The H∞ observer relies on the estimated current and actual current values to estimate the magnetic pole angle of the motor. The H∞ observer guarantees that the gain value for the worst-case estimation error is within the index range of design performance. This paper proves the convergence of the H∞ observer and utilizes matlab simulations to verify results. The simulation results show that the H∞ observer-based speed controller for senseless PMSM yields good performance.

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This paper introduces a high-load-type active magnetic bearing (HL-AMB) for an induction-heated roll. To support the induction coil installed in a heated roller, a novel active magnetic bearing that can support a load of about 10 kN and has a compact body is introduced. The HL-AMB consists of fan-shaped bias cores and cross-shaped control cores. Bias cores produce a large bias force and bias moment to support the mass of a levitated object, and control cores produce control forces and moments. In this paper, the design and control system of the HL-AMB are described and the results of levitation and rotational tests are presented.

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Since few years ago, electrical energy storage had been attracted as an effective use of electricity and coping with the momentary voltage drop. Above all, energy storage flywheel systems using superconductor have advantages of long life, high energy density, and high efficiency. Our experimental machine uses a superconducting magnetic bearing (SMB) together with a permanent magnet bearing (PMB) and plans to reduce the overall cost and cooling cost. Energy storage flywheel systems operate by storing energy mechanically in a rotating flywheel. The generating motor is used to rotate flywheel and to generating electricity from flywheel rotational. The generating motor consists of 2-phase 4-poles brush-less DC motor and a Hall sensor. A purpose of this research is the development of a compact energy storage flywheel system using SMB and PMB. This paper shows the new model of flywheel that has higher storage energy comparing with conventional one, the improvement of motor drive (DC motor) to increase the speed rotating, and estimating the system at momentary voltage drop.

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All rotating machines, such as electrical AC machines, suffer greatly from vibrations in their rotating parts. These vibrations occur at certain frequencies characteristic to the machine and are dependent e.g. on the structure of the machine, geometrical asymmetry of the parts and the used materials. In case of electrical machines these frequencies are also called the critical frequencies. Driving a machine at or near the critical frequencies cause two kinds of problems due to the vibrations. First, the air gap between the rotor and the stator must have greater safety margins, which decreases the efficiency of the motor. Otherwise, the motor would suffer a fatal damage from a rotating rotor hitting the stator. Secondly, wear of the structures is significantly increased due to vibrations which causes increased maintenance costs and decreased motor life-time. Active vibration control aims to suppress the vibrations at the critical frequencies by assistance of an additional actuator that is capable of exerting an external force to the rotor. This actuator is implemented with additional windings in the stator such that it has minimal effects on the normal operation of the motor. Active vibration control methods applied in electrical AC machines have previously mainly relied on linear time-invariant (LTI) models of the motor and correspondingly on traditional control methods such as LQ control and convergent control. These methods have produced successful results in active damping of vibrations and significantly decreased the vibrations at the critical frequency of the machine. In this paper, similar methods are studied in the case of more accurate linear time periodic (LTP) model of the electrical AC machine. Utilization of a more accurate model enables using more precise control. The performance of a periodic state feedback control method is compared to performance of a constant gain state feedback. The developed control methods are tested by simulations with a model that is identified from the data measured from a 30kW squirrel-cage induction motor.

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This paper presents three different LQ controllers, which are used to attenuate rotor vibrations in an electrical motor. The controllers are compared in performance and control effort. A dynamic way of solving the related Riccati equation is discussed to overcome the issue of finding the solution, when the model including disturbance dynamics is not stabilizable. One LQ controller is calculated utilizing particle swarm optimization, and the benefits of doing so are evaluated with respect to the cases when no optimization was used in tuning the controller.

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In this paper, a model of in-wheel motor and tire system has been established to analyze numerically the dynamic feature in time domain and frequency domain, from the viewpoint of vehicle longitudinal motion analysis. The model consists of two sub-models, permanent magnet synchronous motor (PMSM) model and transient rigid-ring tire dynamics model. As the simulation results show the electric current measurement error and non-sinusoidal magnetic field distribution can cause motor torque ripple. The vehicle velocity, vertical load, tire sidewall damping and stiffness coefficients can influence the transient response of the tire. It is found from the frequency analysis results that there exist two major resonant regions and the vibration amplitude in the first resonant region is dominant. The dynamics response is greatly affected by vehicle velocity and vertical load.

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