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Volume 38, Issue 4
Displaying 1-11 of 11 articles from this issue
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Yusaku FUJII2002 Volume 38 Issue 4 Pages 337-344
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSThe method, which has been proposed by the author for quick and accurate mass measurements under microgravity conditions using the law of conservation of momentum, and whose feasibility for measuring mass of rigid objects has been experimentally investigated in the previous works, is reviewed and improved. In this work, the feasibility of the proposed method for measuring mass of non-rigid objects has been experimentally and theoretically investigated. In the experiment, an object levitated with sufficient small friction using a pneumatic linear bearing is made to collide with a force transducer. Momentum change of the object is measured as the impulse, i.e. the time integration of the impact force, acting on the force transducer, the velocity is measured highly accurately using an optical interferometer, and then the mass of the object is determined. In this paper, the mass of a non-rigid object is determined with the relative standard uncertainty of approximately 0.1% by means of estimating the velocity of the gravity center of the object. Some points to be considered for measuring mass of general objects under microgravity conditions are discussed.View full abstractDownload PDF (4193K) -
Jun TAMBA, Masaru ARAI2002 Volume 38 Issue 4 Pages 345-350
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSThe non-uniqueness of the International Temperature Scale of 1990 (ITS-90) around 100°C is expected to be 0.1-0.5mK. It is necessary to investigate the non-uniqueness by the precise intercomparison of an appreciable number of standard platinum resistance thermometers (SPRTs) in order to improve the accuracy of the ITS in the future. In this paper a comparison furnace using a pressure-controlled water heat pipe was developed and its characteristics were investigated. The heat pipe has a well with 10mm in inner diameter and 400mm in depth. The pressure in the heat pipe was controlled between 105kPa and 580kPa by means of thermal expansion of helium, and the good pressure stability of ±0.40Pa at 105kPa and ±5.8Pa at 580kPa were obtained. Owing to this control system, the temperature stability within ±0.11mK was achieved and maintained for more than 10 hours between 100°C to 157°C. The good temperature uniformity within 0.4mK over 20cm was also obtained. The repeatability of the heat pipe temperature was within the temperature stability. Totally, the uncertainty of the comparison measurement is estimated to be within ±0.11mK and the performance of the present furnace is high enough to investigate the non-uniqueness.View full abstractDownload PDF (1792K) -
Masahiro ISHIBASHI, Sakujiro OHTSUKI2002 Volume 38 Issue 4 Pages 351-360
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSHigh-precision nozzles whose machining error is less than ±1μm accompanied with a mirror finish were calibrated in critical conditions at pressures up to 0.9MPa against other high-precision nozzles connected in series at the downstream location. Since the Reynolds numbers of the downstream nozzles in a series connection of critical nozzles are lower than that of the upstream one as well as the boundary layer transitions in high-precision nozzles are very stable, the discharge coefficient of the upstream nozzle accompanied with the boundary layer transition could be measured against the downstream nozzles accompanied with the laminar boundary layer. The discharge coefficients of six high-precision nozzles were measured in 14 combinations of the upstream and downstream nozzles at the upstream Reynolds number up to 2.4×106. The boundary layer transitions were detected at the Reynolds number between 0.9×106 and 1.5×106. In the turbulent boundary layer regime, the discharge coefficients of the high-precision nozzles obeyed exactly the newly derived curve, which is expected to be introduced to the revised ISO 9300. The dependence of the discharge coefficient on the Reynolds number during the boundary layer transition were very stable and didn't depend on the nozzle combinations. When all the high-precision nozzles were accompanied with the laminar boundary layers, the mass flowrates calculated from the upstream nozzle and the downstream nozzles based on an unique fitted curve, which had been measured in the laminar boundary layer regime, agreed within -0.02 to +0.05%. This agreement is better than the scattering of the primary calibrations of the high-precision nozzles. Furthermore, it is shown that the high-precision nozzles manufactured in 1992 and 1997 by two different manufacturers had exactly the same discharge coefficient in this regime, therefore, high-precision nozzles are very stable for long period and their characteristics are universal.View full abstractDownload PDF (2465K) -
Yoshio KOSUGE, Masayoshi ITO2002 Volume 38 Issue 4 Pages 361-368
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSWe already reported the necessary and sufficient condition that an α-β-γ filter is stable under the condition that the values of filter gains α, β and γ are positive and are smaller than 1. However, the values of filter gains α, β and γ are not always smaller than 1. Therefore, we present a new necessary and sufficient condition of the stability that can be used even when the values of filter gains, α β and γ are larger than 1. Furthermore, we have made clear that the steady state variances of an α-β-γ filter for a constant velocity target become positive when an α-β-γ filter is stable. We also present the optimal choice of the α, β, γ combination of an α-β-γ filter. In order to evaluate the α, β, γ combination, we use the steady state errors of the predicted position of the α-β-γ filter. More exactly, we use the steady state variance for a constant velocity target under the condition that the steady state errors for a constant jerk (derivative of the acceleration) target are constant. Then we showed that this α-β-γ filter is stable.View full abstractDownload PDF (1481K) -
Manabu YAMADA, Shinichi OHTA, Yuichiro SYUMIYA, Yasuyuki FUNAHASHI2002 Volume 38 Issue 4 Pages 369-378
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSThis paper proposes a new feedback control system based on a multirate sampled data control and a periodic switching for a class of nonholonomic systems in time-state control form. A coordinate transformation is introduced to transform the discretized nonholonomic system with a zero order hold and a sampler into a linear time-invariant discrete-time system. Moreover, a simple necessary and sufficient condition is derived to assure the controllability of the transformed linear system. The contributions are as follows. First, the problem of finding a controller to stabilize the nonholonomic systems is reduced to the well-known pole assignment problem. As a result, a simple and explicit design method of the stabilizing controllers is obtained. Secondly, a quadratic regulator problem is posed and is solved of finding a controller to minimize a cost functional consisting of the state and the control input. This minimization problem is reduced to a linear quadratic regulator (LQR) problem, and a simple design method of the optimal feedback gain is presented. Finally, a simulation for a two-wheeled vehicle demonstrates the effectiveness of the proposed method.View full abstractDownload PDF (2081K) -
Teturo ITAMI2002 Volume 38 Issue 4 Pages 379-387
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSFor realization of nonlinear optimal feedback control, “superposition principle” has been utilized. In dealing with the corresponding linear wave equation, eigenvalue analysis will be efficiently applied. In this paper, a picture of nonlinear optimal feedback control as eigenvalue problems of linear Hamiltonian operator on functional space is given. Emphasis is on an important role of the nondegenerate eigenfunction corresponding to the eigenvalue with the lowest imaginary part. Behaviors of control systems are determined by such eigenfunction. For linear-quadratic systems entirely the same results as the well-known one by Riccati equation are attained also in this eigenvalue analysis scheme. And a typical nonlinear system with discontinuous cost function is also analyzed.View full abstractDownload PDF (1468K) -
Kiyotsugu TAKABA, Yutaka ICHIHARA, Tohru KATAYAMA2002 Volume 38 Issue 4 Pages 388-394
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSIn this paper, we derive necessary and sufficient conditions for internal stability of an implicit system in terms of linear matrix equations (LMEs) under the assumptions of finite dynamics detectability and impulse observability. These LME conditions are generalizations of stability conditions for descriptor systems. We also show that a constrained linear matrix inequality condition and a linear matrix inequality condition for the internal stability can be obtained from the present LME conditions. Moreover, the effectiveness of the LME stability condition is demonstrated by applying it to the stability analysis of an implicit linear quadratic optimal control system.View full abstractDownload PDF (1331K) -
Ken'ichi NISHIGUCHI2002 Volume 38 Issue 4 Pages 395-403
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSObstacle detection and avoidance are essential for achieving a successful soft landing on the moon and the planets. In this paper, we propose an image processing method for obstacle detection and avoidance on the moon and the planets. The proposed method consists of two stages. The first stage is a coarse classification of all points in an image into two regions: the safe landing region and the obstacle region. The discrimination function for the classification is composed of local and semi-global statistics of image intensity. This function is devised so as to avoid the opposition effect of the sun and to be independent of the direction of the sun. In the second stage, a point in the safe landing region that has the maximum distance from the obstacle region is selected as a landing point. Although the classification of the first stage is coarse and there is some miss classification, the procedure of the second stage ensures the selection of a safe landingg point. The ability of the proposed method is evaluated by using CAD images constructed by fractal modeling.View full abstractDownload PDF (4323K) -
Ken'ichi NISHIGUCHI, Shoji YOSHIKAWA2002 Volume 38 Issue 4 Pages 404-410
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSObstacle detection and avoidance are essential for achieving a successful soft landing on the moon. In a previous paper, we proposed using local and global statistics of image intensities to select a safe landing site. In this paper, we apply that method to photographs of the moon's georama. In the assumed landing scenario, an unmanned lander takes photographs of the landing area, detects obstacles, and makes avoidance maneuvers. In the experiments, our image processing method is applied to the photographs of the georama taken at three different distances, and the validity of the finally selected site is evaluated. It is shown that safe landing sites are selected in conditions with a variety of light directions, and the robustness of the proposed method is confirmed.View full abstractDownload PDF (4203K) -
Weishui WAN, Kotaro HIRASAWA, Jinglu HU, Junichi MURATA2002 Volume 38 Issue 4 Pages 411-419
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSIt is well known that Backpropagation algorithm is one of the most basic algorithms in neural networks(NNs). Its role can not be overestimated in the field of neural networks. In this paper we propose a new variant of backpropagation algorithm through controlling the outputs of the hidden layers. The proposed algorithm therefore provides better generalization results than the basic backpropagation algorithm. The added term to the criterion function has the following property: (1) Small added noises in the inputs to the networks will not give evident effects to the outputs of the networks; (2) Small added noises in the weight matrix except the one between the hidden layer and output layer will not give large effects to the outputs of the networks. In addition, simulation comparisons are also made between the new algorithm and some conventional regularization methods, such as Laplace and Gaussian regularizer. Simulation results on the two-spiral problem, function approximation problem and Iris data classification problem confirm this assertion.View full abstractDownload PDF (2185K) -
Masatoshi NAKAMURA, Peng LIU, Satoru GOTO, Nobuhiro KYURA2002 Volume 38 Issue 4 Pages 420-421
Published: April 30, 2002
Released on J-STAGE: March 27, 2009
JOURNAL FREE ACCESSIn this paper, modified input data method as a feedforward compensator to improve control performance of mechatronics was proposed. The proposed method was designed by using the pole assignment regulator. Effectiveness of the proposed method was proved by experiments of contour control of an actual robot arm. The proposed method can be easily apllied without any change of hardware of the systems and accepted in industrial applications.View full abstractDownload PDF (366K)
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