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将来の宇宙開発に必要となると予想される大型デブリ回収機(Remover)、軌道上作業機(OMV)など、高い機動性を備えた宇宙機のミッションとして、大きな角度の姿勢運動と位置変動を伴うものが考えられる。このような、3次元空間で並進・回転の6自由度運動を行う宇宙機の運動方程式は両者が連成した非線形方程式になるため、通常の線形制御理論を適用することは難しい。本稿では非線形の制御対象を変換することなく直接取り扱うことができるスライディングモード制御を、タンブリングしている大型デブリや故障した衛星(本稿ではこれらを総称してターゲットと呼ぶ)の姿勢に宇宙機の姿勢を一致させ、その回りを一定の距離を保って周回するように宇宙機の位置を制御するといった宇宙機の姿勢・位置制御ミッションに対して適用した結果を示す。スライディングモード制御は、可変構造制御(variable structure control)、可変構造系(Variable Structure System: VSS)と呼ばれるものの中で最も理論的に体系化されているものの一つで、何らかの制御入力によって制御対象の状態をあらかじめ設定した超平面に到達、拘束させ、その状態を平衡点に滑らせることによって制御対象を安定化させる制御手法である。最初に宇宙機のダイナミクス・キネマティクスの定式化を行う。ここで考えているような大角度のマヌーバが予想されるミッションにおいては、キネマティクスに特異点の問題のあるオイラ角ではなくクオーターニオンを用いる。次にスライディングモード制御系の設計手順を示し、その安定性に関する評価を行う。さらに、制御対象の変動・不確定性に対するロバスト性を評価する。最後に数値シミュレーション結果を示す。, Future spacecraft such as the Orbital Maneuvering Vehicle or 'Remover' which tries to capture and remove large space debris objects in orbit need to be able to perform large angle and complicated position maneuvers in space. The equation of motion of a rigid body that performs attitude and translational motion (six degrees of freedom motion) is a nonlinear equation. This paper applies sliding mode control that can handle a nonlinear system to the six degrees of freedom control for such a vehicle. Its feasibility is investigated through a numerical simulation of proximity flight around a tumbling target object., 資料番号: AA0001081000, レポート番号: NAL TR-1330

The VSS design problem for a linear system has been investigated using a quadratic performance index, the value of which can be lowered more by logically switching admissible gains {K0, K1,・・・, Kp} than by the single constant gain K0. A unique guaranteed cost control method is introduced to derive the gain switching control law, which uses a simple quadratic function of the state as the switching law. An extension is made to the case where the standard linear control system has undamped oscillatory modes and some sufficient conditions for asymptotic stability have been given. Even the case where the mathematical model of the system includes some bounded modeling errors can be treated successfully by introducing a parameter σ into the switching law. The results of some simulation experiments are also presented to demonstrate the effectiveness of the proposed design technique and to illustrate the corresponding relationship between the parameter σ and the robustness property.

The VSS design problem for a linear system has been investigated using a quadratic performance index, the value of which can be lowered more by logically switching admissible gains {K0, K1,・・・, Kp} than by the single constant gain K0. A unique guaranteed cost control method is introduced to derive the gain switching control law, which uses a simple quadratic function of the state as the switching law. An extension is made to the case where the standard linear control system has undamped oscillatory modes and some sufficient conditions for asymptotic stability have been given. Even the case where the mathematical model of the system includes some bounded modeling errors can be treated successfully by introducing a parameter σ into the switching law. The results of some simulation experiments are also presented to demonstrate the effectiveness of the proposed design technique and to illustrate the corresponding relationship between the parameter σ and the robustness property.