Dielectric Electro-Active Polymer (DEAP) devices consist of a dielectric polymer sandwiched between two electrodes. This paper describes the use of a tubular DEAP actuator for active vibration isolation. First, the quasi-static and dynamic characteristics of the actuator are discussed. These involve the voltage-strain-force behaviour of the actuator. It is seen that the actuator is inherently non-linear, involving an approximately quadratic relationship between excitation and extension under given loading conditions. In a control context, this can be compensated for either by driving the actuator about some d.c. off-set excitation in a quasi-linear manner, or by including a linearization component within the control. Next, issues concerning the frequency response over a wide range of frequency are considered. Internal resonances exist in the actuator, which limit the bandwidth over which it can be used for active control. The actuator has significant internal damping. The potential for active vibration isolation is then explored. The dynamic performance is limited by the potential bandwidth, the maximum force that can be generated and the maximum range of movement, together with the inherent nonlinearity. Performance for harmonic disturbances is investigated within an adaptive feedforward control scheme. Experimental results are presented. Good attenuation of the excitation frequency is achieved but compensation is required to get good attenuation of higher harmonics introduced by the actuator nonlinearity. Isolation in response to a band-limited random input is then demonstrated, with attenuation of 19dB being achieved over a frequency range from 2-8 Hz.

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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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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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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 diameter 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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All rotating machines, such as electrical AC machines, suffer greatly from vibrations in their rotating parts. Vibrations occur at certain frequencies called critical frequencies that are always characteristic to the machine. 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 a more accurate linear time periodic (LTP) system model of the electrical AC machine. Utilization of a more accurate model enables using more precise control and is therefore expected to give better controller performance. The performance of the developed periodic state feedback control method is compared to the performance given by a constant gain state feedback control. 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. It is revealed that the proposed control method works successfully but it gives only small improvement of performance in vibrations control. The reason for so moderate improvement of performance is supposed to be due to the small variations in the time-periodic parameters of the system model.

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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 a smart structural member 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. Response time of the MR pin joint is compared when the MR pin joint is driven under different applied currents and moving speeds. 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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In this study, a semi-active vibration suppression system comprising piezoelectric elements is developed for flexible structures. The vibration suppression system comprises a cantilevered beam with bimorph piezoelectric ceramic tiles shunted by an RL electrical circuit with a switch. A general design method for vibration suppression of the beam is theoretically analyzed using mode analysis, wherein it is assumed that the piezoelectric elements are sufficiently thin and do not change the mode shape of the beam. With this assumption, the vibration suppression system for the beam is designed by tuning the optimal resistance and inductance parameters of the shunted RL network. In this paper, we propose a semi-active vibration control law to improve the damping effect while maintaining the stability of the passive control system. The proposed control law is similar to a sliding-mode control that accelerates the convergence of the system by using switching functions. As an example, numerical simulations have been performed for a cantilevered beam. This study shows that the resonant circuit functions as a type of a dynamic damper for mechanical systems and that sliding-mode control is very effective in damping the multi-mode responses. The results of the numerical simulations show that the semi-active vibration control system is practically more effective in damping vibrations than the passive control system.

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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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Active vibration control usually reduces vibration amplitude and mechanical energy of vibrating structures. In the situation, actuators of active vibration control systems must remove energy from vibrating structures. However, the consideration is inconsistent with a common knowledge of active vibration control, active vibration control systems need external power supply to drive actuators. To find an answer to the inconsistency, a power flow in an active vibration control system of a SDOF oscillator using a piezoelectric actuator has been investigated by the authors analytically. The reason for using the piezoelectric actuator is that piezoelectric actuators have little internal loss and the characteristics make easy to understand essentials of power flows in active vibration control systems. The investigation shows that the actuator is not consuming power from external source but removing and regenerating energy from the SDOF oscillator. The power consumption of the system is caused by the energy loss of the amplifier to drive the actuator. The result implies that an energy regenerative active vibration control method can be realized by reducing energy losses of amplifiers. The energy losses can be reduced by using class D amplifiers, high efficient amplifiers based on switching operation of semiconductor devices, instead of conventional linear amplifiers. The validity of the approach is shown by a numerical simulation. An advantage of the proposed method compared to other energy regenerative vibration control methods and semi-active methods is that the proposed method can use any controllers for ordinary active vibration control and can achieve the same control performance because the difference between ordinary active vibration control methods and the proposed method is only type of amplifier. In this paper, the validity and the advantage are confirmed by experimental comparisons of power flows 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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In this paper, structural sound and vibration control using passive and semi-active shunt piezoelectric damping circuits is presented. A piezoelectric patch with an electrical shunt circuit is bonded to a base structure. When the structure vibrates, the piezoelectric patch strains and transforms the mechanical energy of the structure into electrical energy, which can be effectively dissipated by the shunt circuit. Hence, the shunt circuit acts as a means of extracting mechanical energy from the base structure. Different types of shunt circuits (such as an RL series circuit, an RL parallel circuit and an RL-C circuit) employed in the passive damping arrangement, are analyzed and compared. Using the impedance method, the general modeling of different shunt piezoelectric damping techniques is presented. The piezoelectric shunt circuit can be seen as an additional frequency-dependence damping of the system. One of the primary concerns in shunt damping is to choose the optimal parameters for shunt circuits. In past efforts most of the proposed tuning methods were based on modal properties of the structure. In this study, a design method based on minimization of the sound power of the structure is proposed. The optimal parameters for shunt circuits are obtained using linear quadratic optimal control theory. Numerical simulations are performed for each of these shunts techniques focusing on minimizing radiated sound power from a clamped plate. It is found that the RL series, RL parallel and pulse-switching circuits have basically the same control performance. The RL-C parallel circuit allows us to reduce the value of the inductance L due to the insertion of an external capacitance C. However, the control performance will be reduced simultaneously. The pulse-switching circuit is more stable than an RL series circuit with regard to structural stiffness variations. Finally, experimental results are presented using an RL series/parallel shunt circuit, RL-C parallel shunt circuit and pulse-switching circuit.

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This paper discusses 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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This paper presents a vibration isolation system using negative stiffness suspension. The vibration isolation system is developed by combining a positive stiffness suspension in series with a negative stiffness suspension. The developed system could realize zero-compliance to direct disturbance, as well as ground vibration isolation. In the previous system, the ground vibration and, the static and low frequency sinusoidal direct disturbances were efficiently suppressed. However, there was a reverse action in case of impulse or step wise disturbance. Therefore, a peak was appeared which was, sometimes, larger than the displacement caused by the step load. This unpleasant response might hamper the objective function of many advanced systems. In this research, a feedforward controller is added in combination with zero-power control to overcome this problem. Some experimental results are presented to verify the proposed control system in a vibration isolation apparatus.

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In this paper, to realize the comfortable steering feeling during driver's steering or a rough road running, we design a control system of an electric power steering (EPS) for a vehicle with an active stabilizer. Although control systems of the conventional EPS are designed generally to obtain the comfortable steering feeling similar to that using a hydraulic power steering (HPS), the steering feeling might not be realized on a rough road. We propose a design strategy for the control system of the EPS in consideration of the active stabilizer to avoid side effects to the steering system by the reaction force of the front tire due to roll stiffness control for the active stabilizer. According to the design strategy, a controller of the EPS is designed and tuned to realize the HPS-like steering feeling by applying a gain-scheduled control corresponding to both a vehicle speed and a sensor torque on a steering axis in consideration of the active stabilizer, which is designed so as to not only reduce the roll motion of a vehicle body but also suppress the restoring torque which acts on the steering axis through the front tire during the rough road running. It is verified that the control system of the EPS designed is effective to realize the HPS-like steering feeling during the driver's steering and suppress the rotational vibration of a steering wheel during the rough road running.

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Flexible spacecrafts have been requested to perform 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 performance of motion and vibration control. In this paper, an attitude controller of the flexible spacecrafts is designed by nonstationary frequency-shaped robust control based on the differential game theory. The frequency weights of the proposed controller are designed to envelop high-frequency unmodelled uncertainty and enable the controller to suppress the spillover instability. Moreover, the frequency weights for the state vector are designed in the time domain. The proposed controller generates optimal input torques to perform agile and precise attitude switching maneuver of the spacecraft. Several simulation results show the effectiveness of the proposed controller.

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This paper reports on the development and control of a compact, high dynamic camera orientation system with three degrees-of-freedom (DoF). The system orients a small camera around its pan, tilt, and roll axes, using a parallel kinematics driven by ultrasonic piezo-actuators. To fit its application as part of a gaze-driven head-mounted camera system (EyeSeeCam) or as an artificial eye for humanoid robots, the camera orientation device was designed to be small in weight and size as well as to replicate the high dynamic movements of the human eye. The mechanical setup is described and the closed loop control architecture, including a dead zone compensation for the actuators, is introduced. Control experiments conducted with the prototype demonstrated that the system performance is comparable to and even exceeds that of the human oculomotor system.

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In order to reduce greenhouse gas emissions, the generation of renewable energy is required. Therefore, this paper focused on a small-sized hydraulic generator, since small scale hydropower has a large potential for power generation. Standard mechanical bearings are installed in conventional small-sized hydraulic generators to support the rotating shaft. However, mechanical ball bearings cause rotational loss, noise and limitation of device durability. In order to upgrade the performance of a hydraulic generator, a new type of permanent magnet hybrid type magnetic bearing is proposed in this study. The stator is designed by finite element method magnetic field analysis. According to the analytical result, by making the root of stator salient pole wider and eliminating magnetic saturation, stronger bearing power was obtained. The analytical attractive force and negative spring force characteristics were then verified under static operation conditions with a simple experimental setup. Moreover, in order to confirm dynamic performance in the time domain, the impulse response was measured with the result showing good performance. In addition, by using the measured coefficient of attractive force and negative spring force, a numerical simulation was carried out to check the dynamic performance in the frequency domain and compared with an experimental result. The result of the frequency response showed good control performance in frequency domain.

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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 method 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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Previous theoretical studies have shown analytically and numerically that a vibrating system can be stabilised and its vibrations can be suppressed by an open-loop control of a stiffness parameter, a stabilisation by parametric stiffness excitation. This approach is investigated further numerically and implemented experimentally for a flexible rotor with multiple disks supported by active bearings. A periodic open-loop control of the stiffness coefficients of a bearing is realised by periodically changing the control parameters of an active magnetic bearing. This periodic variation of control parameters is regulated at fixed frequency and amplitude in such a way that it acts like a parametric excitation in the rotor system. As it was shown for simple vibrating structures (chain mass system, cantilever, Jeffcott rotor), a periodic variation can enhance the effective damping which leads to a vibration reduction in a vibrating system. Since this control is open-loop, it can be operated in parallel to existing and well-established controllers already in use in active magnetic bearings.
In this paper, the method of damping by parametric excitation is realised experimentally in a rotor system. Direct numerical simulation is performed to calculate ranges for control and system parameters where damping by parametric excitation is effective. First experimental results are shown to demonstrate the applicability of the method.

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In this study, a nonlinear adaptive control system for a single-rotor type small helicopter is designed. First, a small autopilot device, which can be applied any single-rotor type helicopters, is developed based on FPGA (Field Programmable Gate Array) board. In the case of small helicopter, the payload limitation is so tight. Therefore, we can only use small and light weight sensors and computer for the control. All the sensors we use for the autopilot device are light enough to be mounted on any small helicopters. the total weight of the autopilot device with box is about 300 g. Next, a nonlinear adaptive attitude controller for small helicopter is designed by using adaptive backstepping method. It is guaranteed to make the attitude of the helicopter follows arbitrary time varying reference attitude, even when the helicopter model has the parameter uncertainties, such as inertia moment or aerodynamic uncertainties. Finally, the effectiveness of the autopilot device and the adaptive attitude controller are verified by simulation with parameter uncertainties, and the flight experiment using heterogeneous small helicopters.

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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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This article described on the implementation of impedance control with the adaptive elements and compliant walking mechanism in hydraulically driven hexapod robot named COMET-IV. The main issue when applying impedance control in this robot is the body attitude stability during walking on the uneven terrain that contains of major soft surface. The impedance controller is derived for each leg from vertical motion changes. In addition self-tuning stiffness method is proposed as an adaptive element from the changes of the robot's body attitude vector (magnitude), to ensure the robot is self-adapted with the changes of stepped ground. On the other hand, compliant walking mechanism is designed for force-based walking trajectory and proposed impedance controller integration. The proposed controller and mechanism are verified by running the robot on the designed uneven terrain (extremely soft surface) in the laboratory using critical condition of side walking setting.

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This paper deals with a problem of modeling and vibration analysis of a flexible robotic arm under fast motion. Conventional method of modeling does not exactly express the bending mechanism of a flexible beam. Then a new description of deformation on the flexible shaft and Hamilton's principle are used to derive the dynamic model of the flexible robotic arm. A nonlinear dynamic model is proposed to describe the dynamic behavior of the flexible beam and the dynamic equations of the flexible robotic arm are also presented. Derived equations consist of some nonlinear forces and nonlinear stiffness. The present research considers the effect from those nonlinear forces coupling with angular functions (angular position, velocity, acceleration). A forced vibration method is applied to evaluate the characteristics of flexible vibration. In this research, numerical calculations based on two strategies are applied to analyze the flexible vibration. In the first strategy (AIM, angle independent method), angles of joints are assumed to be independent of the external forces. In the second strategy (ADM, angle dependent method), the effect on the angular functions of joints due to the external forces is considered. Especially, the gravity affects significantly on the residual vibration of flexible robotic arm and on the angular functions.

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This paper discusses a control method which can stabilize the giant swing motions of 3-link horizontal bar gymnastic robot. A method called Multiple-prediction Delayed Feedback Control(MDFC) proposed by the authors, which has been shown to be effective in control such chaos system, is extended in this paper to experimental gymnastic robot system, taking in account the effect of friction around the link joint. The dynamic of underactuated systems like gymnastic robot shows significant differences in cases of with friction and without friction. However, MDFC considers only the ideal situation without friction. Therefore, a stabilization control method consisting of three kind of control inputs which the one is MDFC for guaranteeing asymptotic stability and the others are used for friction compensation is derived. Numerical simulations and experimental results prove its effectiveness of our proposed method.

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The German Pavilion on the World Exhibition EXPO 2010 in Shanghai showed an interactive 3D-pendulum as one of its main attractions. The pendulum consists of a sphere with 3m diameter which is equipped with several hundred thousand LEDs and used as a projection screen. The sphere is mounted via a long bar at an electrically driven crosstable which is used for the excitation of the pendulum. The crosstable is located in a theater-like building where the visitors can follow the show. Thereby, the sphere performs large circular and pendular motions, while the crosstable can only perform very small motions. Also during some parts of the show the sphere should move in a certain way which is obtained by interpreting the visitors' action as a physical excitation. In this paper the system and control design are discussed and experimental results are presented.

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In this paper, we describe the manipulation of nuts and flexible objects for assembly work by incorporating force sensorless impedance control in a robot. This robot is a dual-arm manipulator, and each of its end effectors is a three-fingered robot hand. Generally, a force sensor is used for recognition of external force on the fingertips. However, such sensors are very expensive and easily damaged by inappropriate contact with the object. This motivated us to estimate the external force without using a force sensor. In this study, the external force on the robot fingertip was estimated using a disturbance observer. Then, estimated results were compared with measurement results of the force sensor to validate the former. Impedance control was designed for a three-fingered robot hand by using this estimated external force. By application of the designed impedance control to the robot hand, the robot was successfully able to grasp nuts ranging in size from 2 mm to 12 mm through an algorithm formulated in the study. In this algorithm, we incorporated a method called following control to retain the contact of the finger with the worktable while performing the grasping task. Thus, the nut grasping task could be performed at a higher success rate, despite some errors in the robot position and vision data. Furthermore, a boiled egg considered as a flexible object was successfully grasped through force sensorless impedance control. An impedance controller for the boiled egg was designed using identified model parameters of the egg, and its effectiveness was validated experimentally.

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As one of structural health monitoring systems, the authors developed a broadband ultrasonic propagation system using macro fiber composite (MFC) actuators and fiber Bragg grating (FBG) sensors. This system can send and receive broadband Lamb waves efficiently in a specific direction, and the MFCs and FBGs can be integrated into composite laminates because of their flexibility and high fracture strain. In this research, this system was applied to detect an interlaminar delamination in carbon fiber reinforced plastic (CFRP) laminates. One MFC and one FBG were bonded on each surface of the CFRP laminate to generate and receive the symmetric modes and the anti-symmetric modes separately for identification of the multiple modes of Lamb waves in the laminate. Then we investigated the mode conversion of Lamb waves at both tips of a delamination in the middle of the thickness of the laminate, through an experiment and finite element analysis (FEA). On the basis of the knowledge about the mode conversion, an index to evaluate the delamination length was proposed using velocity changes by the mode conversions. From the results of experiments and FEA for the laminates with an artificial delamination, this new index was found to be effective to evaluate the delamination progress in the laminate quantitatively.

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In this paper, a method for three-dimensional dynamic simulation analysis of rotary snow removing machines is constructed to contribute to optimum design and control of the machines. The simulation analysis method is based on the Distinct Element Method, which is suitable for simulation of the dynamic behavior of discontinuous objects like snow. The key part in the simulation analysis is contact judgment between snow and rotary equipment and described in detail. As a first step to evaluate the validity of the constructed method, motion characteristics of snow thrown from a shooter into the air were analyzed and compared with experimental results. The simulation results showed a similar tendency to the experimental ones. Moreover, as snow removal characteristics, we analyzed and discuss not only the motion characteristics of the snow in the process of snow removal but also the resistance torque on the equipment such as auger from the snow. These results demonstrate the practical usefulness of the constructed method.

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Nowadays, eco-driving as a series of driving behaviors is proposed to reduce CO₂ discharge of vehicle and realize safe driving. The eco-driving behaviors are mainly about accelerator and brake works that are operated by leg`s motions of driver; however, there are few studies to explain physical fatigue resulted by leg`s motions for eco-driving behaviors. In the paper, eco-driving experiment was conducted in the modes of normal driving, eco-driving with instruction, and eco-driving with eco-indicator. The simulated driving experiment was realized by a universal driving simulator system, and surface electromyography of leg muscle of 10 subjects was measured to clarify physical fatigue of driver in different driving modes. The experiment indicates that fuel economy in eco-driving with eco-indicator is higher than other driving modes, and muscle activities are lowest by signal analysis of the surface electromyography. The result also suggests that eco-indicator is effective assistant system to help driver realize eco-driving as well as reduce physical burden of driver.

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A high efficiency digging algorithm for hydraulic excavator has not been established, because the relationship between digging control parameters and digging efficiency is too complicated. Therefore, we have investigated how digging efficiency is affected by the digging control parameters. In this paper, the digging efficiency is defined by the scooped soil mass per applied digging energy because it is the one of the most simple equation to show the digging efficiency. A digging test device was developed to reproduce the digging behavior of entire hydraulic excavator with using the pre-programmed bucket tip trace. In addition, a digging simulation model by two dimensional distinct element method (2D-DEM) is developed to clarify the digging efficiency with considering some different digging settings. The simulation results are verified by comparing with the test data using the digging device. The digging simulations were performed in order to investigate how the bucket tip trace and velocity effect the digging efficiency. This study shows digging efficiency can be improved by changing tip traces or digging velocities.

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In series-type multiple magnetic suspension systems, multiple floators are suspended in tandem by one electromagnet. The nearest floator to 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 with an arbitrary number of floators are discussed. They are controllable and also observable even when only the displacement of the floator nearest to the electromagnet is detected. 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 normal floators to carry out experiments in various conditions. As the first step to realize the levitation of multiple floators using one electromagnet and one sensor, a basic trial was carried out in the fabricated system.

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Since the number of trans-femoral amputees has increased by industrial or traffic accidents in modern society, the demand for a prosthetic limb has also increased year after year. In this case, loads applied to a prosthetic limb are important indices for contact relation and position relation to the human body. However, conventional systems cannot measure long continuous walking motion of amputees under a wide range of environmental conditions. Moreover, conventional structural optimization method for a multi-axis force/moment sensor has not been put into practical use. In this paper, we developed a six-axis force/moment sensor that can be attached to a prosthetic limb and improved performance of this sensor by a new practical structural optimization method. The developed sensor in the present study can be easily fixed between the artificial knee joint and the prosthetic foot to detect the load condition during walking. We used finite element analysis, response surface method and desirability function as proposed techniques for multi-objective structural optimization in three-dimensional space. As results in the present study, we optimized the structure of this sensor and validated the effectiveness of optimum design variables and the proposed techniques.

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The polynomial or algebraic method based on the transfer function can achieve simultaneously pole and zero placement. Since the method has clear physical interpretation, it is easy to introduce many different constraints such as vibration modes and the operation limit of the actuator. However, when the controlled plant is high-order, numerical problems arise in the solution of a Diophantine equation or a Sylvester matrix. In order to make the conventional polynomial method practicable, this paper presents an improved polynomial method based on the modified delta operator δ for the microprocessor control. The modified delta form can significantly improve numerical conditioning of a Sylvester matrix on pole and zero assignment in controller design. As an example of a controlled plant, a 10th-order plant is considered. Then, the numerical sensitivity of a Sylvester matrix reduces at one millionth of the conventional one obtained on the z-plane. The simulated results show that the proposed method can be applied to a high-order plant and a robust controller can be developed. Therefore, the proposed method would be useful for the computer controlled plants in industry.

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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, an evaluation method by which stiffness and damping characteristics including several nonlinearities of rubber element can be estimated by a few kinds of material tests would be greatly useful. The purpose of this study is to establish an evaluation method in which the nonlinearities of rubber-like material caused by loads simultaneously applied in both the shear and compression directions are taken into consideration. As the first step of this study, a material stretch test, a static load test and an FEM analysis were carried out to determine the nonlinear characteristics of static stiffness caused by loads applied in both the compression and shear directions. The method proposed in this paper for correcting material parameters on the basis of the strain level of the rubber was verified to be useful for accurate estimation of nonlinear stiffness. It was verified that the dependency of the static stiffness on the initial deformation can be expressed by the FEM analysis and the proposed method can precisely estimate the nonlinear behavior of rubber isolators.

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A three-degree-of-freedom (3-DOF) active vibration isolation system using displacement cancellation control technique is developed. The displacement cancellation concept is presented and implemented in this research to obtain zero compliance of vibration isolation table against direct static force as well as to suppress the dynamic disturbances acting on the isolation table. In the displacement cancellation control technique, relative movements of the vibration free table are followed with I-PD control and movements of the middle mass respect to base are controlled with PD control. The corresponding controllers are designed in such way so that actuator can generate opposite force against disturbance to cancel the effect of displacement of the middle mass on the vibration isolation table, which finally leads zero compliance of the isolation table. Voice coil motors (VCMs) are used for getting linear actuating effect and corresponding displacements of the table are detected by eddy-current gap sensors. The experimental results showed that the developed system with displacement cancellation mode control has capability to maintain zero compliance against direct static force in the 3-DOF motions associated with horizontal translations and a vertical rotation. Moreover experiments have been conducted to measure the dynamic responses of the vibration isolation table to direct disturbance.

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Current surgical robotic systems have shown that the robotic approach bring many benefits to both surgeons and patients. However, these systems still need further improvements to increase dexterity and to facilitate a cost-effective integration in any standard operating room. With this goal, we propose a compact and accurate positioning mechanism, called Dionis. This spatial hybrid mechanism based on a parallel kinematics provides three rotations and one translation for single incision laparoscopy. The corresponding axes intersect at a remote center of motion that is coincident with the entry point into the patient's abdominal cavity. In addition, the compact design of the Dionis robot allows direct access to the patient, without removing the robotic system. This, besides saving precious space in the operating room, improves safety over existing solutions. This article presents the conceptual design of the Dionis robot followed by its workspace and dynamic analysis. The required maximum speed and maximum torque of the actuators are obtained for a set of typical trajectories to chose the most appropriate actuators. The final design and a summary of the control architecture are as well described.

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The selection of optimal inputs and outputs from larger candidate sets is an important prerequisite step to enable an effective design of a robust control law. This is especially true for active damping of complex and high-dimensional multi-input multi-output systems (MIMO) with flexible modes. Existing optimal selection strategies are commonly based on a single nominal system model and cannot explicitly consider parameter variations in the system. Such nominally optimal selection, however, may perform poorly for a different parameter setting and thus deteriorate achievable robust performance. The proposed integrated input-output (I/O) selection strategy overcomes this problem by explicitly considering a set of systems covering the range of relevant parameter variation. It is structured in three consecutive selection steps, where only the subset of accepted candidates is fed into the subsequent selection; thus, it is also computationally efficient. An additional advantage is a quantitative ranking of the final candidates, which enables the control engineer to make an optimal I/O choice. The method is illustrated by a flexible beam example as well as a blended wing-body passenger aircraft model.

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The paper presents a method to get better maneuverability by improving steering feelings so that inexperienced captains can smoothly control pleasure boats in critical situation for collision avoidance. To achieve this aim, firstly in order to show how much difficult it can be to control the boats; the complicated dynamics of them are evaluated by using a developed simulator including a steering system with simulation software. Then, it is considered to vary whole rotation angles and to give a virtual reaction torque on a helm. The results show that it may be able to navigate stably and reduce the meanders if the reaction torque is appropriately supplied and the whole rotation angle on the helm is suitably determined for inexperienced captains.

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For rudder angle servo mechanism in steer-by-wire (SBW) system of pleasure boats, this paper presents a sliding mode controller with continuous control input. The sliding mode control theory is applied to the controller so as to have high robustness against the normal pressure of a rudder, which is regarded as an unknown disturbance. Designed with the twisting algorithm and the describing function method, a switching input of the proposed controller could enforce a switching function into a limit cycle. As a price of abandoning the perfect sliding mode, the proposed controller can bring not infinite-frequency switching input but continuous control input. As a result, the improvement of the load of the actuator in SBW system can be achieved.

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High performance of the contact wire and pantograph dynamic interaction is required in the operation of high speed railway vehicles. Due to the constraint of field test, simulation and lab experiment procedures are performable to verify the interaction. Such simulation needs accurate modeling of the response of the pantograph for the consistency in prediction and control. A simple system identification of the pantograph is executed based on the lab experimental data using commercial software and least squares method. The validation of the procedure is performed through comparison between extended experimental data and numerical simulations of the pantograph system. Further analysis is by applying active pantograph control on the system by simulation. The results show availability of the design for active pantograph system.

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This paper proposes a noncontact magnetic suspension system for levitating two different weight iron balls simultaneously using a flux path control mechanism. 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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Flexural waves traveling in an elastic wedge (plate whose thickness decreases towards zero following a power law function) are not reflected back and accumulate at the zero thickness edge what results in a very efficient damping. In practice reflection always occurs because manufacturing a zero thickness edge is not possible. To solve that problem Krylov proposed the addition of a small quantity of damping material on the thinner edge of the plate what results in very effective damping. In this paper, the application of elastic wedges to reduce the vibrations of turbine blades is investigated. The objectives of this research are to evaluate the damping effectiveness of elastic wedge theory in blades and second, to evaluate a non-polymeric material as vibration damping material. In this way, the vibration energy of the blade is dissipated by the damping material and, at the same time, high temperature and low strength problems characteristic of polymeric damping materials are prevented. First, a FEM modal analysis of a simplified blade model is performed to understand the effects that the elastic wedge has on the modal shapes and frequencies of the blade. Next, to evaluate the damping levels achieved, a frequency response of the simplified blade model with and without elastic wedge is evaluated with the added damping material. The results show that elastic wedge theory combined non-polymeric damping materials can be an efficient method to reduce vibrations of turbine blades or similar applications.

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This paper presents control system design for occupant lower extremities protection in vehicle frontal collision. A protective control system consisting of an active knee bolster and an active lap belt is designed to reduce the maximum load to the femurs and the maximum lap belt force. In the control system design, we examine the effects of the initial distance between the occupant's knees and the active knee bolster, and the maximum pelvis displacement. It is expected that the initial distance affects the protection performance because the control duration of the active knee bolster mainly depends on the initial distance. To avoid the collision with the steering wheel, the maximum pelvis displacement is restrained. The lap belt force and the contact force between the knees and the instrument panel are calculated so that the load to the femurs is reduced while the lap belt force is not increased compared to passive lap belt. Simulation results clarify the effects of the initial distance and the maximum pelvis displacement on occupant protection under assumption that the protective control system can vary the initial distance.

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In the present paper, a vibration mode modification method when the dynamic characteristics of the vibration system change by assembly is proposed. When the dynamic characteristics change, component mode synthesis (CMS) is widely used. However, CMS is not suitable for vibration control. Therefore, the present paper proposes a component mode modification technique for vibration control problem. The vibration modes are modified using component modes for constructing a reduced-order model. In this method, vibration modes are modified using static correction modes (attachment modes). Using these modes, orthogonalization is performed by subspace iteration. First, the concept of vibration mode modification is proposed. This concept is then applied to the proposed modeling method, which is referred to as the extended reduced-order physical modeling method. Finally, the proposed method is examined through dynamic responses of an elastic vehicle. Using the elastic vehicle, a single lane change test and simulation are carried out.

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