森田 泰弘

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。」

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.