Thin steel plates widely used in various industrial products are contacted with rollers in a production line. There is a problem in that the quality of the surface is deteriorated, such as scratches and peeling of the plated layer of the thin steel plate, by this conveyance method. We have proposed a magnetic levitation system that uses electromagnets and permanent magnets in combination, utilizing static attraction of permanent magnets to assist levitation. We used the genetic algorithm to search for the optimal placement of permanent magnets in order to improve the deflection of the steel plate during levitation. In this report, the weighting factors of the evaluation function are changed, and the placement results of permanent magnets obtained from GA are discussed.

When an thin and flexible steel plate is to be levitated, levitation control becomes difficult because the thin steel plate undergoes increased flexure. We propose a levitation of an thin steel plate that is bent to the extent that the plate does not induce plastic deformation. It has been confirmed that vibrations are suppressed, and levitation performance is improved by bending levitation. In this study, we applied sliding mode control theory to the bending levitation system using 1DOF model and carried out levitation experiments. We conducted experiments on levitation performance when the electromagnet was oscillated by vibrator in the bending levitation system. We conducted experiments on levitation performance when the electromagnet was displaced by frame vibration in the bending levitation system. As a result, it is possible to realize stable levitation in the face of an input external disturbance when levitating at the optimum bending angle.

It is effective to reduce sliding frictions to improve fine positioning abilities. On the other hand, flexible supports are advantageous for securing rigidity. Therefore, in the present study, we developed the uniaxial flexible support table for fine-positioning that is actuated by attraction forces between electromagnets and permanent magnets. By installed two pairs of electromagnets and permanent magnets, the expected advantage of this apparatus is possible to output a displacement for a long stroke, a high resolution and cooperated the two. On this occasion, based on the calibration of attraction force and the stiffness analysis of the flexible support mechanism, a moving displacement of the table for applied current to electromagnets was estimated. Then, referring to those estimated results, three kinds of materials with different Young’s modules: A2017, C5191 and SUS303 were adopted as the flexible support mechanism, and the apparatus was developed. When positioning experiments with step responses were conducted, step-wise displacements were recognized. The maximum displacement with the long stroke positioning was 108μm(A2017), and the minimum displacement with the high resolution positioning was 60nm(SUS303). In addition, when C5191 material was installed for the flexible support mechanism and experimented the cooperation positioning, a displacement for a long stroke and for a high resolution were equivalent to the case where the respective positioning was made separately.

The continuous steel plate production line in a steel works is as long as several kilometers, during which the steel plates are supported by contact and transported by a number of rollers. In the traveling of the continuous steel plate by such a roller, problems such as vibration, friction, distortion and surface quality deterioration due to contact between the steel plate and the roll occur. As a solution, this research group is studying noncontact guide control system that suppresses the vibration of the steel plate by applying an electromagnetic force near the edge of the traveling continuous steel plate. In this study, we examined the running characteristics of the flexible steel plate as a basic study.

A vibration reducing effect of a magnetic suspension system using a first-order-reset element (FORE) in the controller is enhanced by a modified reset function. The proportional-derivative (PD) feedback control is the simplest control method of stabilizing the magnetic suspension systems which consists of two elements. In the PD-controlled systems, restoring force is produced with the proportional element and damping effect is produced with the derivative element. Meanwhile, the feedback controller consisted of a FORE for the stabilization of magnetic suspension system has been proposed. The FORE is replaced a linear integrator built into a first-order-low-pass filter with a non-linear integrator. The proposed controller can be achieved the stabilization of magnetic suspension system with one element which produces two effects of the restoring and the vibration reducing. However, the FORE-controlled system cannot given the restoring force and the vibration reducing effect, separately. The vibration reducing effect will be determined when the restoring performance is achieved by the feedback gain of FORE. Therefore, this paper proposes more reduced vibration by modified the value for the transition at the reset. This paper shows several results in the simulations and the experiments.

Recently, visual measurements have been used widely for automatic control systems, such as self-driving cars, robots, drones, etc. Since a camera can detect multiple objects and degrees of freedom, there are significant advantages for magnetic levitation system over conventional sensors such as simplification of control system and reduction of the number of sensors. However, the measurement by the camera has a trade-off relationship between sampling-rate and resolution, and only one can obtain high accuracy. In addition, there is a disadvantage that there is a delay due to detection and image processing. In this paper, we use an inexpensive USB camera and applied vision-based control to a single-degree-of-freedom magnetic levitation system. We describe the measurement algorithm and control system in the magnetic levitation system, and show the results of levitation tests.

This study discusses the effects of stability control for tractor and three-trailer combinations on the lane-keeping performance. The stability control compensates the direction difference angles between the velocity vector at the front articulation point and the trailer using active steering of the trailer wheels. The control effects are evaluated by examining computer simulation with the driver-vehicle system, which consists of a vehicle model, a driver model and the stability controller. The stability control suppresses the direction difference angles at the front articulation points. The damping characteristics of the lateral displacements of the centers of gravity of the trailers are improved by reducing the direction difference angles. The stability control prevents amplification of the lateral displacement of rearward trailers, whereas the lane-keeping performance of the vehicle without the stability control deteriorates. The stability control suppresses the oscillation and the tracking deviation of the rearward trailer axle.

In recent years, PMVs (Personal Mobility Vehicles) have been attracting attention as a new means of transportation. We focus on the three-wheeled PMV which has two front-wheel and one rear-caster. They are environmentally friendly without exhausting harmful gases. These vehicle bodies are relatively smaller than cars, so they have a high affinity for pedestrian space. However, depending on the specifications of the vehicle, there is a possibility that wheel lifts during turning because the weight of the vehicle is low. In this study, we proposed the model of the three-wheeled PMV with two front-wheel and one rear-caster. We discussed the validity of the modeling by comparing the numerical simulation and the experiments. In terms of the driving force of the front wheels, the modeling was generally valid when the velocity of the vehicle is low and the turning radius is large. However, in the opposite case, the centrifugal force of the driver during the turning becomes larger and the moment around the front wheels axle center point is generated. Then it is expected that more detailed analysis will be possible by considering the relationship between the centrifugal force received by the driver and the driving force of the motor in consideration of the driver’s behavior. From the parametric study, it was found that the normal forces of the wheels greatly changed depending on the riding position of the driver. The area of the risk of falling was shown.

This paper describes an online (real-time) optimization for control target values of NOx emission in diesel engine. Diesel engines are required to realize high efficiency and low fuel consumption while achieving exhaust emissions regulations which will become even more severe in the future. For that purpose, it is necessary to manage together the NOx reduction rate on the engine side and the aftertreatment system side. The target value manager performs online optimization based on the actual operating state of the engine and aftertreatment system. Online optimization uses a gradient method. By this method, the control target value that minimizes the operation cost (fuel and urea water) is calculated while suppressing the NOx emission to the regulated value or less. In addition, multi-objective particle swarm optimization is used to calibrate Lagrange multiplier parameters that affect NOx emissions and total operation cost, and Pareto optimal solutions for the two evaluation functions are obtained. This optimization improves the performance of the target value manager and visualizes tradeoffs between NOx emissions and total operating costs. The effectiveness of this approach is evaluated by simulation using data measured with a diesel engine test bench.

The stability of energy optimal control (EOC) when the hybrid electric vehicle performs self-driving with speed control is verified by simulation and numerical calculation. As for the effects of the dead time of acceleration and velocity feedback, simulation that add dead time stepwise to both feedback results in negligible control error even if the dead time up to 40 ms (equivalent to 4 cycles of control loop) is given. As for the convergence of control, since the necessary and sufficient condition for the solution of the Euler-Poisson equation gives the minimum value of the evaluation function is that the second variation of the evaluation function is positive, the second variation of the evaluation function for both control law of engine and motor are calculated. As a result, it was shown that the engine control law is positive over the whole operation area on the torque-angular velocity plane, and it is the optimum solution over the whole operation area. Regarding the motor control law, although a part of the locus passes through the negative region, most of it exist within the positive region, indicating that the motor operated generally under the condition that the evaluation function had a minimum value.

Pneumatic control technology is widely used in industry. Electronic control is generally used as a method to control pneumatic equipment, but it cannot be used in explosive atmospheres or high radiation environments. The master-slave robot used in this study transfers the position command from the master robot using the air pressure signal, and mechanically feedback controls the position of the slave cylinder according to the signal. Since control is performed without using electronic control, we can use it even in extreme environments or when electric power is lost. On the other hand, its characteristics may change depending on the structure and operating conditions. In this study, we examined the configuration of the master robot for generating the signal air pressure. We proposed a method of decompressing compressed air and a method of compressing by external force as a method of generating signal air pressure and evaluated its characteristics. As a result, we found that a master using a cylinder has less delay and better frequency response.

In the assembly of micro components, a slight impact during assembly greatly affects product performance. This work focuses on the assembly of parts including magnetized components. In the assembly of such parts, the attractive force acting between the parts causes a difficulty of assembly without collision. For this reason, such a work is conducted by skilled workers. However, the lack of successors has become a problem. Therefore, a bilateral operation system is developed for training such successors. A bilateral control is installed using two devices including a voice coil motor, a leaf spring and a sensor. The slave device is controlled to follow the motion of the master device. The force applied to the slave device is estimated with a full order observer to reflect the force on the master device. It is confirmed experimentally that the slave device can follow the master device and that the force applied by the slave device can be presented to the master device. In addition, assembling experiments are conducted using the bilateral operation system. The displacement of the both device and the applied external force to slave device are obtained. It is demonstrated that the assembling technology could be evaluated quantitatively.

A kind of an air cushion vehicle (ACV) is known as a hovercraft which carries out a cruise by blowing off the air from the bottom of the body. The ACV has many advantages, such as amphibian vehicle, large payload, and so on. However, the ACV has drawbacks such as its drivability is bad. An improvement of the drivability is effective for the control of the ACV and the disturbance rejection performance of the controller is very significant.

In this research we makes controller that can run an arbitrary curve whose shape has not been determined in advance. And we verified usefulness of controller by running the simulation. Using various sensor and image processing technology we get control value which required for controller. We verified usefulness of these methods by executing control experiments.

We investigated an active biped walker based on a passive dynamic walking model with a torso which can walk down a shallow slope without any actuation. The active biped walker was composed of a torso, hips, and two legs, without ankles and knees. The motion of the walker was constrained to the sagittal plane. The passive walking model used bisecting hip mechanism in order to hold the torso. We used the passive walking model with the torso to determine the physical parameter values of the active biped walker. The physical parameters, leg center of gravity and leg moment of inertia, were determined so that the walking speed in the passive walking model was maximized. The simulations demonstrated that the walking speed of the active biped walker increased, and the energy efficiency of walking was improved. Thus, we confirmed that the design based on the passive walking model with the torso enabled the active biped walker to improve the walking performance.

We experimentally examined the effect of foot mounting position on walking speed in a planar passive walker with flat feet and ankle springs. First, in the compass-like passive walking model with pointed feet, we conducted a simulation to investigate the influence of the position of the mass center of the leg and the moment of inertia around the mass center of the leg on the walking speed. Next, we constructed a planar passive walker with flat feet and ankle springs and no knees. While designing the walker, we used the compass-like passive walking model with pointed feet to determine the position of the center of mass of the leg and the moment of inertia around the mass center of the leg at which the walking speed was maximum. The constructed passive walking machine has a leg length of 0.5 m, a foot length of 0.1 m, and a total mass of 5 kg. Changing the amount of foot attachment offset to 0, 0.025, and 0.05 m, we measured the step length and step time at multiple inclination angles of the slope, and then calculated the average walking speed from the data. The experimental results demonstrated a decrease in the walking speed as the offset amount increased. For instance, at the offset amount of 0 m and slope angle of 0.038 rad, the walking speed was 0.56 m/s. At the same slope angle, the walking speed decreased by 27 % when the offset amount was increased to 0.025 m. Furthermore, at 0.05 m offset amount, we could not find a stable walking position when the slope angle was smaller than 0.038 rad.

When shrimp walk and swim, they use their swimming legs, as called abdominal limbs, under the abdomen as well as the walking legs called chest legs located at the front of the body to generate thrust. Based on the lessons from the shrimp’s swimming method, this paper introduces a novel paddle-typed propulsion mechanism. Moreover, a shrimp-like prototype realizing the propulsion mechanism is fabricated. Practically, the prototype is composed of a microcontroller, eight motors and motor driver, and eight paddles. The outer shell is manufactured by using polylactic acid resin. Specifically, the paddles are evenly installed at both sides where one side consists of a pair of four paddles. To evaluate the effectiveness of thrust generation by paddle-typed propulsion mechanism and to investigate the thrust relation between movement-timing lags of paddles and propulsion speed, several experiments were performed and their experimental results are presented in this paper. Details on this prototype and several video clips for its experimental scenes are introduced in our presentation.

In nature, a wide variety of insects and animals uses flapping wings to fly. Recently flapping flight systems imitated from their flapping wings have been reported in the field of robotics. These studies have introduced distinctive flapping-wing prototypes according to the number of wings and the shape of the wing. Remarkably, in spite of recent advances, the flapping wings have only been studied in a small part of these biosystems. As considering counterless living species, many challenges still remain in understanding and studying flapping wings. Along with this consideration, our study direction is to study the flapping wings of ladybugs and then to realize a ladybug-based artificial flapping wing. What is the most important aspect from the biological point of view is to identify key mechanisms that allow the ladybug to fly. For that purpose, a simple wing prototype capable of flapping and feathering based on the flying motion of the ladybug is developed. We are now in the preliminary stage of identifying the key mechanisms by using the prototype. In this presentation, investigation results obtained from the mechanism through simulations and experiments are introduced.

Designing an active vibration control system generally requires the mathematical model of target structures. The control performances sometimes get worse due to modeling errors and aging of target structures. In addition, actuators have parameter uncertainty due to aging and individual differences. Therefore, the actuator uncertainty causes destabilization of the control system and deterioration of the performance. This study proposes the vibration control method, in which a controller designed without using the model of target structures for arbitrary structures considering actuator uncertainty. First, we introduced a virtual controlled object, which is a SDOF system, for control system design and construct a state equation consisting of only the actuator and virtual structure, not using the model of target structure. Next, the actuator uncertainty is compensated by H_∞ controller and sliding mode controller. Finally, the effectiveness of the proposed method is demonstrated by simulations.

In recent years, as buildings become higher, the effect of wind disturbance on the tall buildings increases. In the general active control systems with fixed gain, the control force is approximately proportional to the strength of the disturbance. So the performance of the device may not be fully demonstrated because of wind disturbance intensity fluctuation. For example, when the gain is designed according to the wind disturbances of strength once in 50 years, the system may not obtain enough control force when the wind of strength once a year is entered. In this paper, we designed an active vibration control system, based on the State Dependent Riccati Equation (SDRE), to make the gain variable according to the strength of the wind for a super high-rise building with a height of 300 m. Numerical simulations for wind disturbances of strength once in 50 years and winds of strength once a year show that the proposed method can achieve high performance regardless of the strength of wind disturbance.

We propose a new active vibration control strategy based on the future seismic waveform information obtained in remote observation sites. The waveform information in the remote site is transmitted by a waveform transmission network to the structure under control. The waveform transmission network is realized by interconnecting multiple controlled structures and observation sites. By using the future waveform information obtained through the network, we propose a control law realizing fairly higher control performance over the conventional structural control methodologies. A preview control law consisting of the state-feedback and feedforward control (preview action) is adopted. For the preview action, future values of the disturbance in some time interval are necessary. However, because the future value of the earthquake waveform is unknown, the preview action contributing the performance improvement is generally impossible. To get over this difficulty, an AI-based wave estimation system to estimate the future earthquake waveform is proposed. The wave estimation system is a multi-layered artificial neural network (ANN). Through a small scale simulation study with a recorded earthquake event in Japan, we show that the proposed control method achieves much higher control performance over the conventional LQ-based active control.

A magnetorheological (MR) fluid is a suspension of micron-sized magnetic particles in a carrier fluid. In the presence of a magnetic field, magnetic particles form the chain-like structure called “cluster” along the field. This phenomenon is MR effect. The clusters resist against the shear flow and the pressure flow. As a result, MR fluid generates the yield shear stress within few milliseconds by a magnetic field. The drastic change of the rheological property and the quick response to the external magnetic field enable the MR fluid to be used as a hydraulic oil of controllable dampers. However, conventional dampers using the MR fluid have two serious problems. One is the sedimentation, and the other is the narrow dynamic range. The sedimentation is the settlement of particles which arises from the density mismatch between the dispersed particles and the base oil. In order to keep the performance of the MR damper, its magnetic particles have to be held in the carrier fluid. On the other hand, the dynamic range is the ratio of the maximum damping force to the minimum damping force. The cylindrical-type dampers require the sealing elements to confine the MR fluid, thus the sliding friction between the sealing and the cylinder is inevitable. In order to suppress the vibration response in the high frequency range, the minimum damping force due to the sliding friction must be reduced. In this study, a shear-type MR grease damper was proposed to solve the sedimentation problem. The MR grease is a suspension of micron-sized magnetic particles in the grease, which is a lubricant composed of base oil, thickener, and additives. We hope that the particles in the MR grease might be held since the thickener is a three-dimensional network structure. Furthermore, the application of the MR grease to the shear-type damper can solve the problem of the narrow dynamic range. A shear-type damper doesn’t require sealing elements, thus the sliding friction is theoretically zero. As a result, the wider dynamic range is realized. Additionally, in order to verify its damping effect in the application to a structure, the vibration suppression test using a small structure model was carried out.

This study proposes a new type of active Vibrometer measuring vibration possessing long period and wide dynamic range. In order to lower the natural frequency and expand the detectable amplitude, the sensor with the low natural frequency is realized by using feedback control. A digital feedback controller using classical control theory in previous study had problems such as limitation of measurement range, and mismatch of the measurement signal in large amplitude vibration. In order to improve measurement performance more, we aim to introduce the controller with modern control theory. In this report, to measure the relative displacement of the sensor in order to do modern control with two state variables, a photo-reflector is introduced and its property is examined.

A 3-degree-of-freedom zero-compliance mechanism is applied to a force measurement device using a cantilever. Force measurement using a cantilever has advantages of high resolution because of the low stiffness of the cantilever. However, it has a problem that the measurement conditions change because the point of force is displaced when force acts on the cantilever. To prevent such an undesired displacement, a force measurement device is fabricated in which the detection point is moved to counteract the displacement of the point of force. In this device, the force is estimated from the displacement of the detection point. The efficacy of this device is demonstrated by experiments on measuring milli-Newton-order static force.

The energy efficiency of the conventional flow control of hydraulic systems using the pressure loss of throttle valves, which are widely used in construction machinery, is very low. If the hydraulic PWM control system is used, a significant improvement in energy regeneration efficiency can be expected. However, the non-linear damping and delay in response of switching valves affect the decrease of the energy regeneration efficiency of the hydraulic PWM control system, unlike the transistor in the boost chopper of the electrical system. Therefore, in this study, we grasp the effects of parameters by numerical simulation for a model that simulates a typical hydraulic system used in construction machinery, and try to understand how the characteristics of the switching valves affect the energy regeneration efficiency of hydraulic PWM control system.

The purpose of this research is to expand the output of the vibration power generator. Vibration power generation has been drawing more attention in recent years as it can be used for sensors applied to health monitoring of aged buildings and bridges. Lever mechanism has been adopted in order to apply more force onto reverse-magnetostrictive material for power generation. The natural frequency can be changed by changing leverage ratio so that the applicable frequency band can be adjusted. The experimental machine has been built and frequency response from the acceleration of the vibration to the generated voltage has been obtained. The theoretical vibration power generator has also been analyzed by using software “Creo Simulate”. Experimental and theoretical results have been compared and examined.

This paper presents an approach to deal with the identification of continuous-time Hammerstein-Wiener systems, characterized by a series connection of static nonlinear elements and a linear dynamic element. The static nonlinear elements are a sum of known basis functions and the linear dynamic element is a parametric rational transfer function. The proposed method is based on the projection of input-output data onto the finite dimensional parameter space whose basis is determined by the structure of an overparameterized representation of the Hammerstein-Wiener model. Simulation results show the effectiveness of the proposed continuous-time identification method.

This paper propose a vibration control system for overhead cranes considering nonlinear behavior. Overhead cranes are widely used in the industrial field to carry heavy loads. It is a non-linear system, and vibration of the load occurs as it moves. As one of remarkable nonlinear control methods, there is NNDIC (Neural Network Direct Inverse Control). This control method is important as an intelligent approach to counter the problem of mathematical models. However, it show a high sensitivity to noise and disturbance. In order to ensure the stability and improve performance, this study applies IDCS (Inverse Dynamic Compensation via ‘simulation of feedback control Systems’) to NNDIC. The IDCS allows a suitable control without noise and disturbance by inputting control variable generated in simulation area into a real crane. Simulations and experiments verified that the proposed method suppresses the vibration of lifted load and solves the problem of stability against noise and disturbance.

A cooperative transportation system of different-size objects to each corresponding destination has been developed as an application of Swarm Intelligence. It is well known that several kinds of insects may achieve complex tasks in a group, where each insect may play its role by the information of its surroundings. By making a swarm, the insects achieve difficult tasks that an individual cannot manage alone. This collective behavior, as emerged in a group of social insects, has been called Swarm Intelligence. Although the Swarm Intelligence has been applied to control a robotic swarm, these artificial systems still depend on an outside datacenter to share the information or on a controller placed outside of a swarm to get rules for each robot. In order to improve the system and implement the natural behavior into the artificial control system, a swarm should have the learning ability that may correct and acquire its behavior by itself. In this study, a cooperative transportation task of different-size objects to the proper destinations by lots of workers has been simulated. Transportation goals are varied to the size of objects. Smaller objects should be carried one goal and larger objects should be carried to the other goal. In addition, workers could not sense the size of the object solely. Workers are required to estimate the size of objects based on positional information of their neighbors. A solution of the task of decision-making problems about a transportation goal has been proposed by using an artificial neural network. Considering individual workers in a group as a unit in the artificial neural network, the learning algorithm of neural networks has been applied to decide the transportation destinations. Each worker may decide his action based on nearby objects and the state of nearby individuals, and the swarm transports objects under the control of the swarm network. As a result, it is shown that the swarm acquires the learning ability how to decide on an appropriate goal for given objects.

Labyrinth seals have been used as non-contacting sealing devices for rotors such as on turbo machines. In recent years, an improvement of the sealing performance of labyrinth seals has been required due to the increasing pressure of turbo machines. In this paper, it is suggested that new type pump labyrinth seals (Radial labyrinth type) have high sealing performance on pump wear rings in the radial direction of fundamental labyrinth grooves seals. This study was carried out by CFD analysis. First, radial labyrinth seals were tested in an actual double suction pumps. Subsequently, it became clear that pump radial labyrinth seals have an effect of increasing pump efficiency by reducing leakage compared to general plain wear ring seals. It was also confirmed by various experiments that the radial labyrinth seal have the effect of increasing pump suction specific speed. Furthermore, it was demonstrated that the rotor-dynamics coefficients of radial labyrinth seals are smaller than plain seals.

In this study we make clear dynamic characteristics of a vertical rotor supported with cylindrical gas journal bearings which have air supply and exhaust holes on each bearing surface in its circumferential direction. Natural frequency, modal damping ratio and natural vibration mode of the rotor-bearing system are measured in impact test. Threshold rotating speed of self-excited half-frequency whirl of the rotor-bearing system is also measured in rotating test. Its natural frequency and its threshold rotating speed decrease and its modal damping ratio increases as supply pressure of air film decreases. Its threshold rotating speed in case of speeding up the rotor speed is higher than that in case of slowing down of the rotor speed in all conditions. Its lower order natural vibration mode is rotating vibration mode and its higher order natural vibration mode is translational vibration mode. The vibration mode of half-frequency whirl is only translation mode and the rotating mode doesn’t becomes unstable in all conditions. Even if the supply pressure becomes zero, threshold speed doesn’t become zero. Put another way, the vertical rotor supported with the cylindrical hydrodynamic gas journal bearing, which is fabricated several supply and exhaust holes on the bearing surface, and its eccentricity of steady state is zero, becomes stably for half-frequency whirl within a certain rotating speed. The threshold speed increases as the volume of the chamber connected to air supply and exhaust holes, but it converges almost to the threshold rotating speed with the air supply and exhaust holes opened through atmosphere.

Numerical and experimental analyses of the static and dynamic characteristics of liquid annular seals with axially partial helical grooves were carried out to investigate the effects of the helix angle γ of grooves. In this analytical model, the effect of γ corresponded to that of the number of thread grooves n because the helical groove pitch along the axial length was set to be constant. The numerical solution and experimental procedures were applied in the same manner as in the previous study on the partially helically grooved seal. The numerical results qualitatively agreed with the experimental results, demonstrating the validity of the numerical analysis. The leakage flow rate Q for a large γ was higher than that for a small γ because an increase of γ diminished the effect of the fluid energy loss at the steps between the groove and the land regions on the reduction of Q. It is noted that all types of the partially helically grooved seals produced smaller Q than the smooth surface seal. For a small concentric whirling motion of the rotor, the tangential dynamic force Ft for the partially helically grooved seals was lower than that of the smooth surface seal and it became lower with increasing γ, resulting a large magnitude of the tangential reaction force for a rotor forward whirling motion. This was expected because a large γ enhances an effect equivalent to the negative inlet swirl motion induced by the helical grooves, which facilitate spiral flow in the direction opposite to that of the spinning rotor. The radial dynamic force F_r became lower with increasing γ, which was attributable to the fact that a large γ enhances the “Lomakin effect” produced at the downstream end of the helical grooves and causes an increase in the magnitude of the radial reaction force. The results obtained within the present analysis showed that the helical grooves with a combination of a large γ (= 29.6°) and a small g_al/L (=0.2), in which g_al is the axial length of a helically grooved section in a seal stator and L is the seal length, yielded a better dynamic characteristics for the stability margin of pumps because of the suppression of the forward whirling motion of the rotor with large radial and tangential dynamic reaction force.

This paper presents an experimental evaluation of dynamic characteristics of arc spring dampers which reduce the vibration of rotating machinery. Arc spring damper is a recently proposed oil-film damper that has two or more arc-shaped centering springs and multi-layered oil films formed by Wire Electric Discharge Machining (WEDM). They require less space and weight than those of conventional Squeeze Film Dampers (SFDs) with squirrel cage springs. However, the basic characteristics of arc spring dampers, which include the influence of the number of arc springs, added mass coefficients, and cross-coupled terms have not been investigated so far. In the present study, a series of centered, unidirectional excitation tests on 2 types of arc spring dampers which have different arc patterns are conducted to identify their damping coefficients and added mass coefficients. The following are main findings of this study: (1) 4-arc type has larger direct damping coefficients in comparison with 2-arc type; (2) Arc spring dampers can have considerable amount of added mass and small amount of cross-coupled coefficients.

Substitution of plastic gears for steel gears has been discussed aiming to reduce noise and vibration. Plastic gears are superior in mass, friction and damping characteristics. On the other hand, they are inferior in strength and stiffness that sometimes bring unexpected troubles. The mechanism of vibration excitation by meshing in plastic gears is considered basically same as that of steel gears. However, the difference in stiffness and damping effect can yields different behavior from steel gears. For example, it is well known if you mesh plastic gear with steel gear for the purpose of heat radiation, the plastic gear vibrates much harder than the case of pair of plastic gears. The vibration characteristics of plastic gears are discussed in this report by comparing vibration among gears with different materials.

A rocket turbopump is the high-speed and high-power turbomachinery to feed the propellant to the engine and various rotor vibration problem had occurred in the past development. Rotordynamic fluid forces generated by the shaft seals is affects to the vibration characteristics of turbopump rotor. It has been reported that the floating ring seal often applied to rocket turbopumps has a stabilizing effect of rotor vibration. On the other hand, the component layout of the turbopump rotor also affects to the vibration characteristics. In this study, we investigate the effect of the component layout and shaft seal position on the rotor vibration characteristics by using complex eigenvalue analysis. Rotordynamic fluid force of floating ring seal is modelled using the cross-coupled stiffness. The results showed that the cross-coupled stiffness of the floating ring seal is effective to improve the modal damping ratios in some component layout. In addition, the effective position of floating ring seal on the turbopump rotor to stabilize the rotor vibration was described.

To develop turbomachinery blades with high reliability, it is indispensable to verify the natural frequency, the damping, the resonant stress, etc. under operating condition, and utilize these data in the mechanical design of a new blade. BTT (Blade Tip Timing) and the telemetry system have been widely used to measure the modal parameters of turbomachinery blades. In measurement of the modal parameters of blades in rotation, it is well known that the mistuning phenomena make the identification of modal parameters difficult. Namely, because, in a mistuned bladed disk, responses of many vibration modes are superimposed, it becomes difficult to correctly identify the natural frequency and the damping of each vibration mode. This is one of the critical issues to be overcome for developing blades with high reliability. Recently LSCF（Least-Squares Complex Frequency-Domain）method has been proposed as an effective method for identifying the modal parameters from complicated frequency responses. This method was also applied to derive the modal parameters of a bladed disk from the frequency responses expressed by travelling wave coordinates. In this paper, the validity of the LSCF method is verified by numerical simulations, where the modal parameters of mistuned bladed disks are identified from the frequency responses consisting of many vibration modes. In addition, the accuracy of the conventional half power method used in identifying the blade damping is researched.

IPMSM (Interior permanent Magnet Synchronous Motor) is widely used for many industrial applications because of its high power density and high efficiency. Also, in recent years, the product’s rotational speed has become faster and the size has become lighter and more compact. On the other hand, these changes have increased magnetic flux density inside the motor and radial electromagnetic excitation, which causes large noises as a result of the sound and vibration. It is known that one of the causes of the noise is the resonance between the electromagnetic excitation force and the stator core. Although it is necessary to clarify the resonance condition of the electromagnetic excitation force and the stator core to reduce noise, the condition when the resonance happens has not become clear enough yet. In this report, we carried out the research on the resonance condition of the electromagnetic excitation force and the stator core. IPMSM can be regarded as a periodic structure, and one equation of motion with 48 degree of Freedom (DOF) is transformed into 48 equations of motion with 1 DOF using the coordinate transformation specific to cycle-symmetric structures. By solving these 48 equations of motion, it became clear that the resonance occurred when the excitation frequency matches the natural frequency and the excitation mode order matches the natural vibration mode order. This resonance condition was also consistent with the experimental results. In addition to that, for IPMSMs with 8 interior permanent magnets and 48 slots, it became clear that the stator core is excited in the vibration modes which is multiples of 8 and the occurrence of resonance can be suppressed by avoiding the use of the frequency which satisfies the resonance condition.

Sloshing is a phenomenon of fluid motion in a partially filled container. Sloshing often caused overflow, during events such as seismic vibrations. Thus, the prediction of the sloshing phenomenon with overflow is important. The purpose of this study is to propose an analysis method of the sloshing with overflow in a rectangular tank and to clarify the influence of overflow on the sloshing phenomenon. For this purpose, the basic equations of the system considering overflow are derived. The velocity potential of sloshing with overflow is represented by a linear combination of bulging modes in a rectangular tank without overflow. Then, the differential equations governing the generalized coordinates of velocity potentials and the water depth are obtained. The eigenvalue and the time history analyses are carried out to investigate the characteristics of sloshing with overflow. Then, the results of these analyses are compared with the results of the conventional linear sloshing analysis and experiments to verify the validity of the proposed method.

This study addresses the nonlinear sloshing in the two-dimensional problem based on the Arbitrary Eulerian–Lagrangian finite element formulation (ALE). In particular, this paper focuses on a technique to control the computation mesh in the ALE formulation for preventing mesh distortion. Since this technique introduces algebraic relations for nodal coordinates, this study treats these relations as constrained equations. Then, we introduce formulation for constrained systems with the Lagrange’s method of undetermined multipliers to derive equations of motion. As a result of this formulation, it can be found that equations of motion of this system is given by the differential algebraic equations (DAEs) consisting of differential equations for time evolution of sloshing and algebraic equations (constraints) regarding the nodal coordinates. In order to calculate the DAEs formulated by the present method, this study employed a numerical integration technique based on the mid-point schemes with the Newton-Raphson iterative procedures. The proposed approach is validated by comparisons with an existing model in the time domain analysis.

This short paper presents a visual feedback experiment for non-planar sloshing without any geometrical feature extraction. First, we construct a dynamical model by applying Walsh basis approach. Second, we design a feedback controller by applying a port-Hamiltonian approach instead of the standard LQG approach. Finally, we confirm the validity of the model and controller by the non-planar feedback control experiment.

This paper describes the applicability of the numerical model on estimating of sloshing wave crest impact pressure acting on a fixed roof of cylindrical tank. A large shaking table test, conducted on the E-Defence shaking table, has been analyzed. In the shaking table test, partially water-filled cylindrical tank with the flat fixed roof was subjected to the earthquake motion recorded in the site of the existing nuclear power plant, when the Niigataken Chuetsu-oki earthquake occurred in 2007. In order to clarify the liquid sloshing behaviour observed from the tests, we conducted the numerical simulations of the observed violent sloshing phenomena with strong nonlinearity, such as splash of the tank liquid, breaking waves and so on, by using the open source code “OpenFOAM”. Based on the computed results, time histories of pressure acting on the tank roof and wall is presented. The numerical model well simulated the observed waveform with a sharp large pressure peak at the time of liquid impact on the tank wall. As for the liquid impact zone of the tank roof, the numerical computations indicated good agreement with the observed results.

This paper describes vibration characteristics of a cantilevered flexible sheet under forced excitation (motion excitation) in uniform flow. A theoretical model of the sheet subjected to forced excitation in fluid flow using the Doublet-point Method based on the unsteady lifting surface theory is developed. Frequency response (amplitude ratio between the excitation displacement and displacement of the sheet with changing excitation frequency) is investigated theoretically.

When machines and structures exist in a fluid, they are affected by fluid. Therefore, the unstable vibration such as flutter may occur and induce an accident problem. So, it is important to predict the vibration caused by the influence of fluid. Here, a flutter of flexible plate is investigated. As examples of flutter of flexible plate, countermeasures against flutter in power generation turbines and nuclear power fields, vibration of vocal cords, the oscillating doom roof, a high-speed printing machine are enumerated. In this analytical method, dynamic stability of rectangular flexible plate is considered in three-dimensional channel. Channel wall is considered rigid and established only thickness direction of the flat board. So, it is possible to investigate effect of channel wall. The fluid assumed as an ideal flow in a subsonic domain, and the fluid pressure is calculated using the velocity potential theory. The unsteady fluid pressure is determined by using the integral equations for the pressure along the span and the pressure along the chord under the boundary conditions in the Fourier space. Applying the Galerkin method to the equation of motion of an elastic plate, the three-dimensional coupled equation of motion of a flexible cantilevered plate is derived. Changing the mass ratio, aspect ratio and gap ratio, the critical flow velocity and vibration made of the plate are investigated. And, the relationship among mass ratio, aspect ratio and gap ratio are investigated.

This paper presents a three-dimensional flutter analysis and wind-tunnel experiments of coupled parallel plates (double plate) in axial fluid flow. The unsteady fluid force acting on the plate surface is calculated by using Doublet-point method based on the unsteady lifting surface theory. The equation of motion of the plates coupled with the fluid flow is derived employing the finite element method. The characteristic roots of the system are obtained from the flutter determinant, and the stability of the system is examined with changing flow velocity. The variations of flutter velocity and mode are shown with mass ratio.

This paper deals with active control to suppress a flow-induced sheet flutter in a spacious passage. The sheet flutter is suppressed by using injection and suction air flow which are formed through the nozzles. To show the validity of this method, the suppression performance is experimentally examined and evaluated from the increase rate of the flutter velocity with control as compared to it without control. The influences of the number and the arrangements of nozzles on suppression performance are discussed based on the visualized air flow patterns around the sheet and the nozzles with control.

This paper presents a dynamic stability analysis on the self-excited vibration of a plate supported by air pressure. In the analysis, the unsteady fluid force acting on the plate surface is calculated based on the theory of two-dimensional leakage-flow. The model built in the dynamic stability analysis applies iterative calculation by a numerical solution to determine the floating displacement of the plate, its steady state, and the pressure and rate of air that flow through the bottom of the plate. This model demonstrates the dynamic stability of the plate when it vibrates close to steady state. In addition, the local work done by the unsteady fluid force acting on the plate (bottom surface) is calculated, and the region where the excitation fluid force acts is examined. Furthermore, the fluid force that acts on the plate is separated into factors, such as compressibility and viscosity. This is done to analyze the effect of the work done by the fluid force that results from those factors on the dynamic stability of the system. From the results, the factor which is important for the occurrence of the self-excited vibration is shown, and the instability mechanism is discussed.

Free-standing rack system where each rack is not fixed to the floor nor the wall is proposed and is in use in European countries and the US as a storage method of the nuclear power station spent fuel. Although this system can reduce the influence of the excitation force of earthquake by making use of frictional force between the bottom surface of the rack and the floor surface together with the fluid force excited by the motion of each rack, design guidelines are not yet established. In this research, for the purpose of estimating the fluid force more precisely, the gap between the racks is treated as a two-dimensional gap flow, the pressure loss coefficient at the flow path junction and the top of the flow path is estimated based on the steady CFD calculation and incorporated with the motion model. Our main concern in this paper is the rocking motion. As a result, it was concluded that rocking motion can be suppressed by increasing the pressure loss coefficient at the top of the fuel rack.

The present work is concerned with energy harvesting from a piezo element-covered flapping flag. In order to obtain analytical insight into the problem we consider a two degrees of freedom model, which might be the simplest possible model of the flag. In this short note we derive the mathematical model and discuss a simple optimization problem.

A cantilevered pipe conveying fluid causes unsuitable motion as flow speed increases, such as fluttering and divergence because of fluid structure interactions. On the other hand, although continuum flying robots actuated by expelling fluid jets are developed by several researchers, they have not taken the interactions into account to design the controller. This study proposes controller for the cantilevered pipe to fly stably, whose tip emits water jets to gain controllable net force, by taking the fluid structure interactions into account. First, the pipe model with nozzles on the head is designed based on some assumptions. Then, the proportional derivative controller to the head position is proposed to dissipate an energy function regardless of the flow speed. If there is no gravity, the controller ensures Lyapunov stability of the system regardless of the flow speed. Finally, the simulation with the proposed controller verifies that the pipe can keep stable even when the flow speed increases. In addition, the stability analysis with various control parameters shows that the stability of the system can be improved by tuning the control parameters.

The rotational behavior of a lifting capsule was investigated using 3DOF free rotational apparatus in a wind tunnel. Several sizes of glass beads were added on the frontal surface to simulate an ablated surface. The rotational behavior was compared and the effect of the surface roughness was investigated in a flow of Mach 0.3. The roughness of one percent of capsule diameter completely suppressed the rolling motion, which was peculiar to the capsule with smooth surface.

We are researching centrifugal blowers used for dust collection and air conditioning in homes and factories. In this study, we targeted turbo type. It is characterized by high efficiency and high pressure air. However, the downside is that there is a lot of noise. In this study, we focused on the high pressure of the rear edge of the blade due to the collision of the rear edge of the blade. As a result, there is a pressure difference before and after the blade, which interferes with each other as it passes through the tongue and generates noise. This noise is the BPF noise represented by the actual rotational speed x blade. By reducing the flow of this collision, we thought that we could reduce the pressure difference before and after the blade and reduce the noise generated. Therefore, focusing on the slowdown of the vortex generated between the impeller and the circulation flow near the cutoff, we took measures. The vortex that occurs between the blades expands the wrap gap to generate a flow through the blade, reducing the scale of the vortex. As a result, the collision flow to the rear edge of the blade is relaxed, it was revealed that BPF noise was reduced. Decrease in circulation flow is alleviated by attaching a projection to the bottom of the casing. This slowdown reduces the collision flow to the rear edge of the blade and reduces BPF noise.