Highly precise positioning control is based on mechatronics. Nanotechnology, especially nanometer positioning technology with high-speed and robust positioning feedback control, is used in various technical fields including measuring systems, magnetic recording and the semiconductor industry. To date, various actuator systems have been proposed, but the structural models have working distance of either less than a millimeter or more than ten millimeters. A structural model with working distance of several millimeters has not been reported in the relevant literature. We propose an actuator structural design that would enable production of actuator systems with such working distances. This actuator has a voice coil motor and a new guide with an elastic support mechanism consisting of a special spring that is restricted to movement in only one direction. This ESM causes no lost motion, friction with motion, or mechanical play. The voice coil motor thrusts and displaces the elastic support mechanism linearly. Therefore, highly precise positioning control can be realized using a simple controller. This paper describes evaluation of the positioning control method from the displacement of ESM and presents basic data for development of future nano-actuator systems.

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In this paper a pneumatic positioning stage which is mounted on the base plate and supported by the coil-type spring isolators is considered. The stage is moved by the driving force during positioning and the reaction force causes vibration of the base plate with its natural frequency, which degrades the performance of the positioning. To reduce the effect of the reaction force and improve the positioning time, the base plate jerk feedback is proposed. An external force is used to realize the principle of the base plate jerk feedback based on the theoretical background. The experimental results confirm that the working principle of the base plate jerk feedback obeys the theoretical concepts. The feedback is then employed for the real positioning. Based on the experimental results including repeatability, the effect of the reaction force was considerably reduced and the settling time of the response was improved, after employing the base plate jerk feedback with approximate optimal gain.

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Horizontal motion of booms in rotary cranes typically generates undesirable two-dimensional load-sway; therefore, crane operators must be highly skilled to control the crane's motion. To reduce the burden on human operators, automatic control systems that can simultaneously control the boom's position while suppressing unwanted load-sway have been widely investigated. In most existing control schemes, both horizontal and vertical boom motion must be used to suppress load-sway. However, it would be less energy intensive and indeed safer if a control scheme could be developed that only utilized horizontal boom motion, i.e. without the need for any vertical motion. In this paper, we present a nonlinear controller design that enables both boom positioning and load-sway suppression using only horizontal boom motion. Numerical simulations and experimental results demonstrate the effectiveness of the proposed method.

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This paper proposes a multi time scale behavior control method for autonomous omni-directional mobile robot. As for motion planning, there are many problems to solve such as pass planning for a goal, moving by obstacle avoidance, keeping away from danger, and so on. The method is based on virtual potential field method. For each problem having a time scale, the corresponding module is constructed and virtual potential field is generated. Virtual force calculated from each potential field is used for generating the velocity command. The numerical simulations were carried out to verify the usefulness of the proposed method. From the results, it was confirmed that the robot can reach the destination without colliding with the static and moving obstacles by using the proposed method.

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The simple multi-period repetitive control system proposed by Yamada and Takenaga is a type of servomechanism for the periodic reference input. That is, the simple multi-period repetitive control system follows the periodic reference input with small steady state error, even if a periodic disturbance or uncertainty exists in the plant. In addition, simple multi-period repetitive control systems make transfer functions from the periodic reference input to the output and from the disturbance to the output have finite numbers of poles. Yamada and Takenaga clarified the parameterization of all stabilizing simple multi-period repetitive controllers. Recently, the parameterization of all robust stabilizing simple multi-period repetitive controllers for time-delay plants with uncertainty was clarified by Yamada et al. However, using the method by Yamada et al., it is complex to specify the low-pass filters in the internal model for the periodic reference input of which the role is to specify the input-output characteristic. The purpose of this paper is to propose the parameterization of all robust stabilizing simple multi-period repetitive controllers for time-delay plants with the specified input-output characteristic such that the input-output characteristic can be specified beforehand.

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Flow-induced vibration may occur in the structures such as elastic beams subjected to annular flow in the narrow passage. Once the flow-induced vibration occurs, vibration amplitude becomes larger, consequently it causes a lot of troubles such as fatigue or failure in mechanical structures. In this paper, for the purpose to avoid these troubles, the active control of vibration of an axisymmetric elastic beam subjected to annular flow is investigated. An air-pressured actuator is attached on the surface of the circular cylinder for the vibrational control. As the shape of the actuator changes by control, the gap width in narrow passage changes, which causes the change of the fluid pressure. Therefore, the vibration of the fluid-structure coupled system can be suppressed. The fluid-structure coupled equation based on the Euler-Bernoulli type of partial differential equation and the Navier-Stokes equations is analytically derived including control terms. By applying the optimal control law to the coupled system, the unstable behavior is stabilized. The stability of the coupled system is investigated by eigenvalue analyses of controlled coupled equations. Numerical simulations are performed to investigate the efficiency of the proposed control method.

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The FDC (Flow Dynamics Conveyer) has often been used in power plants and iron works because of its superiority in low noise and power compared with roller type conveyers. The FDC consists of a trough and a belt, and the air is supplied from a series of holes provided on the trough. However, large vibrations occur when the flow rate reaches a certain value. This abnormal vibration is defined to be self-excited vibration caused by leakage flow. In this study, as a first step, the theoretical model of a non-tapered clearance flow passage is examined and the natural frequency is calculated. In addition, experiments are conducted to examine the validity of the theory. As a second step, in the case of a tapered clearance flow passage, a concentrated load is added to the belt. The effects of the belt deformation, the flow rate, and the added loads on the clearance flow are examined along with considering the generation mechanism of the abnormal vibration. As a result, it was clarified that the generation mechanism of the self-extracted vibration was due to the phase shift by a change in parameters.

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In this study, the influence of valve closing and opening operations to change inner pressure during pump operations on the pulsation boundary condition was investigated to improve the prediction accuracy of pressure pulsation. Vibration experiments were conducted by using an actual size mock-up piping system with 40 m long as found in nuclear power facilities. A drastic change in the boundary condition of the acoustic resonance by a slightly different valve opening ratio to set a different inner pressure was seen in the experimental results. The simulation results by using the method of characteristics showed that the boundary condition of the acoustic resonance changed when the valve opening ratio was changed slightly from 10 % to 15 %. This indicated that the boundary condition of the acoustic resonance had a pulsed change and changed even at the small valve opening ratio, which was approximately 15% though the design threshold value was 25 %. It was concluded that the boundary condition of the acoustic resonance was sensitive to a slight change of the valve opening ratio and this was one of the reasons why it is difficult to predict the pressure pulsation behavior including acoustic resonance accurately in actual plants.

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In this study, first, the optimum adoption of singular values was investigated by a numerical example when the unknown parameters were the nodal forces of a finite element. It was shown that the distribution of the singular values depended on the sensor location and that accurate estimation results could be obtained by using one singular value in this example based on the condition number. Then the new expression of the virtual additional force was proposed. That is one of the regularization methods of inverse analysis, and the magnitude of the impulsive force is set as an unknown parameter. The numerical example showed that the estimated location of the abnormality determined by the proposed method agreed with that determined by the adoption of one singular value using the previous method in which the nodal forces were set as the unknown parameters. Also, the numerical and the experimental results showed that the accurate estimated location of the abnormality could be obtained by adopting one singular value using the proposed method. As a result, it was shown that the proposed method could be used in the actual application.

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In this study, we introduce the concept of “modal radar” as a novel structural damage analysis methodology for HFR (high-frame-rate)-video-based modal testing that can accurately quantify both the degrees and positions of structural damage. Our modal radar method consists of four parts: (1) vibration displacement measurement using an HFR video camera, (2) stochastic subspace identification to estimate modal parameters, (3) improved local Fisher discriminant analysis for supervised learning based on modal parameters, and (4) feature space normalization for damage quantification. Based on our modal radar method, numerical simulations were performed for beam-shaped cantilevers with different weights as structural damage, and the positions and degrees of the weights were accurately estimated in the normalized feature space, even when the objects to be observed were not involved in the sample set for supervised learning. These tendencies were also confirmed in HFR-video-based modal testing of actual steel cantilever beams with different weights, which were excited by human finger tapping. These experimental results demonstrated the effectiveness of our concept of “modal radar” for accurate structural damage quantification.

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