森田 泰弘

Among a wide variety of challenging projects planned for the coming decade is the MUSES-C mission designed by the ISAS of Japan. Despite huge amount of data collected by the previous interplanetary spacecraft and probes, the origin and evolution of the solar system still remains unveiled due to their limited information. Thus, our concern has been directed toward a sample return to carry sample from an asteroid back to the earth, which will contribute to better understanding of the system. One of the keys to success is considered the reentry technology with hyperbolic velocity, which has not been demonstrated yet. With this as background, the demonstrator of atmospheric reentry system with hyperbolic velocity, DASH, has been given a commitment to demonstrate the high-speed reentry technology, which will be launched in summer of next year by Japan's H-IIA rocket in a piggyback configuration. The spaceship, composed of a reentry capsule and its carrier, will be injected into a geostationary transfer orbit (GTO) and after several revolutions it will deorbit by burn of a solid propellant deorbit motor. The capsule, identical to that of the sample return mission, can experience the targeted level of thermal environment even from the GTO by tracing a specially designed reentry trajectory. (C) 2002 Elsevier Science Ltd. All rights reserved.

Among a wide variety of challenging projects planned for the coming decade is the MUSES-C mission designed by the ISAS of Japan. Despite huge amount of data collected by the previous interplanetary spacecraft and probes, the origin and evolution of the solar system still remains unveiled due to their limited information. Thus, our concern has been directed toward a sample return to carry sample from an asteroid back to the earth, which will contribute to better understanding of the system. One of the keys to success is considered the reentry technology with hyperbolic velocity, which has not been demonstrated yet. With this as background, the demonstrator of atmospheric reentry system with hyperbolic velocity, DASH, has been given a commitment to demonstrate the high-speed reentry technology, which will be launched in summer of next year by Japan's H-IIA rocket in a piggyback configuration. The spaceship, composed of a reentry capsule and its carrier, will be injected into a geostationary transfer orbit (GTO) and after several revolutions it will deorbit by burn of a solid propellant deorbit motor. The capsule, identical to that of the sample return mission, can experience the targeted level of thermal environment even from the GTO by tracing a specially designed reentry trajectory. (C) 2002 Elsevier Science Ltd. All rights reserved.

This paper presents an effective method for the redesign of the M-V 3(rd) stage attitude control algorithm. The objective of the redesign procedure is to introduce an integral term into the controller in order to reduce the steady state error due to the offset of the centre of gravity point of the vehicle and due to the thrust axis misalignment. The proposed method is based on the idea to use the existing controller as the inner (attitude angular velocity) controller of the cascade control. By adding the velocity - position integrator into the controller itself its desired integral characteristic is obtained. The dynamic characteristics and the robustness (by means of the gain and amplitude margins) are investigated for five controllers and corresponding nominal and deviated models.

This paper presents an effective method for the redesign of the M-V 3(rd) stage attitude control algorithm. The objective of the redesign procedure is to introduce an integral term into the controller in order to reduce the steady state error due to the offset of the centre of gravity point of the vehicle and due to the thrust axis misalignment. The proposed method is based on the idea to use the existing controller as the inner (attitude angular velocity) controller of the cascade control. By adding the velocity - position integrator into the controller itself its desired integral characteristic is obtained. The dynamic characteristics and the robustness (by means of the gain and amplitude margins) are investigated for five controllers and corresponding nominal and deviated models.

This paper deals with the design algorithm of the first-stage attitude control for the M-V launch vehicle, Japan's scientific satellite carrier. The control features enhanced and robust characteristics against a range of uncertainties of the system parameters. To achieve sufficiently robust characteristics, the problem is approached within the framework of the H-infinity mixed sensitivity problem. The emphasis is put on how to apply the robust control theory to a complicated real problem. In the design, the standard process is modified in a special way. The original, unstable plant dynamics are preliminarily stabilized by a direct output feedback prior to using the standard design process. Then the. standard theory is applied to these pre-stabilized plant dynamics to yield control. The final form of the controller is provided by its combination with the pre-specified feedback. This modification of the procedure is prompted by the fact that it is not always effective in unstable systems. Thus, the controller can be derived much more easily. The effectiveness of the design has been filially established by the first ever flight of the vehicle successfully putting the world's first radio astronomy satellite into orbit.

This paper deals with the design algorithm of the first-stage attitude control for the M-V launch vehicle, Japan's scientific satellite carrier. The control features enhanced and robust characteristics against a range of uncertainties of the system parameters. To achieve sufficiently robust characteristics, the problem is approached within the framework of the H-infinity mixed sensitivity problem. The emphasis is put on how to apply the robust control theory to a complicated real problem. In the design, the standard process is modified in a special way. The original, unstable plant dynamics are preliminarily stabilized by a direct output feedback prior to using the standard design process. Then the. standard theory is applied to these pre-stabilized plant dynamics to yield control. The final form of the controller is provided by its combination with the pre-specified feedback. This modification of the procedure is prompted by the fact that it is not always effective in unstable systems. Thus, the controller can be derived much more easily. The effectiveness of the design has been filially established by the first ever flight of the vehicle successfully putting the world's first radio astronomy satellite into orbit.

The paper reveals the essential feature of the attitude control of the lunar penetrator system and evaluates its fundamental performance. The spinning LUNAR-A mother spacecraft, orbiting a low lunar elliptic orbit, is to release penetrator modules one by one, which penetrate into the moon's surface carrying scientific instruments. This final phase of the journey is featured by a thumb line controlled attitude maneuver followed by an active nutation control, to ensure the proper impact point attitude. The accuracy of the control will play a key role in the mission as it directly affects the level of the impact load. Although the maneuvering strategy itself cannot be considered special, a relatively high spinning rate of the module makes the problem absolutely different. The level of fluctuation in response time delay of the actuating system has significant influence on the control accuracy: as small as I msec of error leads to approximately 0.7 degree of directional dispersion, almost half the required accuracy. Thus a special autonomous delay compensating algorithm has been developed while the active nutation control is also expected to enhance the control capability of the system. The performance of the entire attitude control system has been finally established through a flight test via an ISAS' sounding rocket in January 1997.

Differential throttling of rocket engines for a high performance vehicle such as rocket powered SSTO is studied. For both powered ascent and landing of a vertical landing rocket vehicle, taking into account the attitude motion of the vehicle in atmospheric flight, the necessary restoring moments are evaluated, These were converted to the throttling requirement for each engine in terms of both static and dynamic characteristics, and rocket firing tests were carried out. Engine throttling was done by control of the hot turbine working fluid. Stable static throttling capability was demonstrated from 30 % to 100 % of its maximum thrust level, The frequency response of the engine thrust modulation was investigated and the correspondence between the simulation-model derived dynamic response and the real behavior was verified, closed-loop engine thrust control by connecting a pressure signal from the engine combustion chamber to the throttling valve was tested for better dynamic response, The expected improvement was achieved in the frequency range concerned, As a result of the study, good controllability for attitude control by applying differential thrust of the primary propulsion was demonstrated.

The paper reveals the essential feature of the attitude control of the lunar penetrator system and evaluates its fundamental performance. The spinning LUNAR-A mother spacecraft, orbiting a low lunar elliptic orbit, is to release penetrator modules one by one, which penetrate into the moon's surface carrying scientific instruments. This final phase of the journey is featured by a thumb line controlled attitude maneuver followed by an active nutation control, to ensure the proper impact point attitude. The accuracy of the control will play a key role in the mission as it directly affects the level of the impact load. Although the maneuvering strategy itself cannot be considered special, a relatively high spinning rate of the module makes the problem absolutely different. The level of fluctuation in response time delay of the actuating system has significant influence on the control accuracy: as small as I msec of error leads to approximately 0.7 degree of directional dispersion, almost half the required accuracy. Thus a special autonomous delay compensating algorithm has been developed while the active nutation control is also expected to enhance the control capability of the system. The performance of the entire attitude control system has been finally established through a flight test via an ISAS' sounding rocket in January 1997.

Differential throttling of rocket engines for a high performance vehicle such as rocket powered SSTO is studied. For both powered ascent and landing of a vertical landing rocket vehicle, taking into account the attitude motion of the vehicle in atmospheric flight, the necessary restoring moments are evaluated, These were converted to the throttling requirement for each engine in terms of both static and dynamic characteristics, and rocket firing tests were carried out. Engine throttling was done by control of the hot turbine working fluid. Stable static throttling capability was demonstrated from 30 % to 100 % of its maximum thrust level, The frequency response of the engine thrust modulation was investigated and the correspondence between the simulation-model derived dynamic response and the real behavior was verified, closed-loop engine thrust control by connecting a pressure signal from the engine combustion chamber to the throttling valve was tested for better dynamic response, The expected improvement was achieved in the frequency range concerned, As a result of the study, good controllability for attitude control by applying differential thrust of the primary propulsion was demonstrated.

本書は, 文部省宇宙科学研究所が平成7年1月15日に打ち上げたM-3SII型ロケット第8号機の第2段飛翔中に発生した姿勢異常について行った技術検討結果を報告するものである。本書は, M-3SII-8号機調査特別委員会の報告書ではなく, 内容は, 技術検討結果のみを報告するものである。過去, 今号機において行われた飛翔前試験の実施状況や, 体制を含めた不具合発生との関連, 再発防止などについては, 同調査特別委員会の最終報告書にゆずる。内容は, 何回かの調査特別委員会にて検討に供された技術資料を, 順次章ごとにたどる形式が採られている。本書では, 以下の同委員会報告内容の主たる点を, この冒頭で記述するにとどめる。「姿勢異常の原因は, 制御系を介した構造振動モードの励振に端を発した姿勢制御用噴射体の枯渇にあったことが明らかとなった。制御系が自励的に構造振動を発振せしめた原因は, 今第8号機におけるペイロード重量増により, 姿勢検出部における構造振動モードが不安定側に大きく転じていたことと, 同じ理由により構造振動に対する制御利得が著しく大きな値となっていたためである。M-3SII型ロケットの開発にあたっては, その初号機の飛翔前においては, 構造振動モード解析ならびにそれら柔軟性を考慮した制御系解析が行われたのであるが, 1)初号機においては剛体性が極めて高いことが数値指標で確認されていたこと, 2)姿勢検出部は初号機においては第1次構造振動モードの腹の位置にあり少なくとも線形性の成立する範囲ではペイロード重量の構造振動モードの制御安定性におよぼす感度は十分小さいと判断されていたこと, 3)今号機の飛翔以前の7回の飛翔を通じて第1次構造振動モードは励振はもちろん検出されたことがなかったことから, 今第8号機の飛翔前においては, 依然として剛体性近似が適用できると判断し, 構造振動モード解析および柔軟性を考慮した制御系検討は行われなかった。これが今回の不具合を事前に発見するにいたらなかった理由である。」

To determine the origin of asteroids and furthermore the solar system, a sample return mission is now planned. This paper presents a mission scenario and the spacecraft design. Some new technologies which must be developed to achieve the mission under strict weight constraint are also described, for example, sampler which must be adaptable to any case of the asteroid surface state, electric propulsion system which is essential to reduce fuel, autonomous navigation of the spacecraft using optical camera, and design of capsule for Earth direct re-entry.

To determine the origin of asteroids and furthermore the solar system, a sample return mission is now planned. This paper presents a mission scenario and the spacecraft design. Some new technologies which must be developed to achieve the mission under strict weight constraint are also described, for example, sampler which must be adaptable to any case of the asteroid surface state, electric propulsion system which is essential to reduce fuel, autonomous navigation of the spacecraft using optical camera, and design of capsule for Earth direct re-entry.

In order to investigate the geomagnetic tail region of the magnetosphere, a joint project, called GEOTAIL, is planned between the Institute of Space and Astronautical Science (ISAS) of Japan and the United States National Aeronautics and Space Administration (NASA). The dual-spinning satellite, equipped with two pairs of wire antennas of 50 m in length, will contribute to deeper understanding of fundamental magnetospheric processes. The high degree of flexibility of the wire antennas and their dimensions may lead to undesirable wire vibrations as well as satellite attitude perturbations through in-orbit events such as antenna deployment, satellite spin-up, despun motor operation, attitude and orbital maneuvers, resulting in distortion of the attitude control accuracy and the scientific observation environment. In the study, the dynamics of dual spinning systems with highly flexible deployable wire antennas has been formulated in a relatively general manner. The associated extensive parametric analysis reveals the interactions among the attitude, orbital and vibrational dynamics as affected by wire deployment, mast "tension and despun antenna operation as well as attitude and orbit maneuvers.

In order to investigate the geomagnetic tail region of the magnetosphere, a joint project, called GEOTAIL, is planned between the Institute of Space and Astronautical Science (ISAS) of Japan and the United States National Aeronautics and Space Administration (NASA). The dual-spinning satellite, equipped with two pairs of wire antennas of 50 m in length, will contribute to deeper understanding of fundamental magnetospheric processes. The high degree of flexibility of the wire antennas and their dimensions may lead to undesirable wire vibrations as well as satellite attitude perturbations through in-orbit events such as antenna deployment, satellite spin-up, despun motor operation, attitude and orbital maneuvers, resulting in distortion of the attitude control accuracy and the scientific observation environment. In the study, the dynamics of dual spinning systems with highly flexible deployable wire antennas has been formulated in a relatively general manner. The associated extensive parametric analysis reveals the interactions among the attitude, orbital and vibrational dynamics as affected by wire deployment, mast "tension and despun antenna operation as well as attitude and orbit maneuvers.

A relatively general formulation for studying dynamics of a large class of interconnected flexible and/or rigid bodies forming a chain type topology is developed. The problem is approached using the Lagrangian procedure with the generalized forces accounting for the environmental effects, damping and control. The flexible members are taken to be the Euler-Bernoulli beams with their bending and torsional deformations discretized using a series of admissible functions. As a particular case, the general formulation is applied to study complex dynamics of the SCOLE (Spacecraft COntrol Laboratory Experiment) system as proposed in the NASA's design challenge. The classical infinite time linear state feedback regulator utilizing the Shuttle's primary and vernier thrusters is designed to suppress the vibrations as well as control the Shuttle attitude motion. The results suggest that flexibility of the mast during the prescribed slewing maneuver substantially induces the line-of-sight error if the Shuttle is uncontrolled, However, the proposed control strategy can damp both the vibrational motion of the mast and librational motion of the Shuttle to the specified acceptable limit within 5 s of the completion of the maneuver.

A relatively general formulation for studying dynamics of a large class of interconnected flexible and/or rigid bodies forming a chain type topology is developed. The problem is approached using the Lagrangian procedure with the generalized forces accounting for the environmental effects, damping and control. The flexible members are taken to be the Euler-Bernoulli beams with their bending and torsional deformations discretized using a series of admissible functions. As a particular case, the general formulation is applied to study complex dynamics of the SCOLE (Spacecraft COntrol Laboratory Experiment) system as proposed in the NASA's design challenge. The classical infinite time linear state feedback regulator utilizing the Shuttle's primary and vernier thrusters is designed to suppress the vibrations as well as control the Shuttle attitude motion. The results suggest that flexibility of the mast during the prescribed slewing maneuver substantially induces the line-of-sight error if the Shuttle is uncontrolled, However, the proposed control strategy can damp both the vibrational motion of the mast and librational motion of the Shuttle to the specified acceptable limit within 5 s of the completion of the maneuver.

A relatively general formulation for studying the dynamics of an arbitrary spacecraft with interconnected flexible bodies is developed accounting for thermal deflection, transient system inertias, shift in the centre of mass, shear deformations, rotary inertias and geometric non-linearities. The computer implementation has been carried out through symbolic manipulation of the equations of motion. Versatility of the formulation is indicated through application to problems of contemporary interest.

A relatively general formulation for studying the dynamics of an arbitrary spacecraft with interconnected flexible bodies is developed accounting for thermal deflection, transient system inertias, shift in the centre of mass, shear deformations, rotary inertias and geometric non-linearities. The computer implementation has been carried out through symbolic manipulation of the equations of motion. Versatility of the formulation is indicated through application to problems of contemporary interest.

The paper presents a relatively general formulation for studying librational dynamics of a flexible platform supporting a mobile base connected to a series of slewing, flexible appendages. It is applicable to missions requiring slew maneuvers of antennas, telescopes, scientific instruments, and in particular, the U.S. proposed Space Station's Mobile Remote Manipulator System (MRMS). Application of the formulation is illustrated through two simple examples: (i) a satellite consisting of a rigid platform with a slewing, rigid appendage; (ii) a flexible beam-type platform representing the space station with a mobile, flexible, slewing arm. The analysis provides a useful insight into interactions between inertia parameters, orbit geometry, translational and slewing time histories, flexibility and initial conditions. Results suggest that under critical combinations of the parameters the system may become unstable. Application of the infinite time linear regulator is demonstrated to regain stability.

The paper presents a relatively general formulation for studying librational dynamics of a flexible platform supporting a mobile base connected to a series of slewing, flexible appendages. It is applicable to missions requiring slew maneuvers of antennas, telescopes, scientific instruments, and in particular, the U.S. proposed Space Station's Mobile Remote Manipulator System (MRMS). Application of the formulation is illustrated through two simple examples: (i) a satellite consisting of a rigid platform with a slewing, rigid appendage; (ii) a flexible beam-type platform representing the space station with a mobile, flexible, slewing arm. The analysis provides a useful insight into interactions between inertia parameters, orbit geometry, translational and slewing time histories, flexibility and initial conditions. Results suggest that under critical combinations of the parameters the system may become unstable. Application of the infinite time linear regulator is demonstrated to regain stability.

A relatively general formulation for studying dynamics of a flexible Mobile Remote Manipulator System (MRMS), supported by an orbiting flexible platform, is developed using the Lagrangian approach with generalized forces accounting for the environmental effects, damping and control. The flexible members are treated as continua and their flexural deformations are represented by a series of admissible functions. The computational algorithm is so structured as to isolate the effects of various system parameters thus helping in assessment of their relative importance. Application of the general formulation, illustrated through several typical MRMS configurations of practical importance, reveals complex interactions between vibrational and librational degrees of freedom, in the presence of MRMS maneuver, over a range of system parameters and initial conditions. Effectiveness of the formulation is also demonstrated through another illustrative example of the SCOLE configuration representing the Shuttle based flexible beam supporting a rigid reflector plate at its end.

A relatively general formulation for studying dynamics of a flexible Mobile Remote Manipulator System (MRMS), supported by an orbiting flexible platform, is developed using the Lagrangian approach with generalized forces accounting for the environmental effects, damping and control. The flexible members are treated as continuum and their flexural deformations represented by a series of admissible functions. The highly nonlinear, nonautonomous and coupled equations of motion, being not amenable to any known closed-form solution, are solved numerically. The computational algorithm is so structured as to isolate the effects of various system parameters thus helping in assessment of their relative importance. Next, effectiveness of the general formulation is illustrated by studying complex interactions between vibrational and librational degrees of freedom in the presence of MRMS maneuver over a range of system parameters and initial conditions. The problem is purposely approached in an increasing order of complexity to gain physical appreciation of the system response. To that end the MRMS is replaced by a single arm. To start with a parametric study of a rigid platform supporting a rigid arm is carried out followed by a progressive introduction of the platform and arm flexibility. Finally, the general case of the Eulerian beam type platform with a flexible slewing and translating arm lays a foundation for studying more complex configurations which the formulation is designed to tackle. Results suggest that the MRMS maneuver can affect librational and vibrational response substantially and under critical combinations of parameters the system can become unstable. The information is fundamental to the design of a control strategy which, for a flexible system in the presence of generalized forces, has received virtually no attention. The thesis ends with a set of recommendations for future course of study which is likely to be innovative, useful and satisfying.

A relatively general formulation for studying dynamics of a flexible Mobile Remote Manipulator System (MRMS), supported by an orbiting flexible platform, is developed using the Lagrangian approach with generalized forces accounting for the environmental effects, damping and control. The flexible members are treated as continuum and their flexural deformations represented by a series of admissible functions. The highly nonlinear, nonautonomous and coupled equations of motion, being not amenable to any known closed-form solution, are solved numerically. The computational algorithm is so structured as to isolate the effects of various system parameters thus helping in assessment of their relative importance. Next, effectiveness of the general formulation is illustrated by studying complex interactions between vibrational and librational degrees of freedom in the presence of MRMS maneuver over a range of system parameters and initial conditions. The problem is purposely approached in an increasing order of complexity to gain physical appreciation of the system response. To that end the MRMS is replaced by a single arm. To start with a parametric study of a rigid platform supporting a rigid arm is carried out followed by a progressive introduction of the platform and arm flexibility. Finally, the general case of the Eulerian beam type platform with a flexible slewing and translating arm lays a foundation for studying more complex configurations which the formulation is designed to tackle. Results suggest that the MRMS maneuver can affect librational and vibrational response substantially and under critical combinations of parameters the system can become unstable. The information is fundamental to the design of a control strategy which, for a flexible system in the presence of generalized forces, has received virtually no attention. The thesis ends with a set of recommendations for future course of study which is likely to be innovative, useful and satisfying.