Robust stabilization of the Space Station

A robust H-infinity control design methodology and its application to a Space Station Freedom (SSF) attitude and momentum control problem are presented. This approach incorporates nonlinear multi-parameter variations in the state-space formulation of H-infinity control theory. An application of this robust H-infinity control synthesis technique to the SSF control problem yields remarkable results in stability robustness with respect to moments of inertia variation of about 73 percent in one of the structured uncertainty directions. The performance and stability of this robust H-infinity controller for the SSF are compared to those of other controllers designed using a standard linear-quadratic-regulator synthesis technique

Robust on-off pulse control of flexible space vehicles

The on-off reaction jet control system is often used for attitude and orbital maneuvering of various spacecraft. Future space vehicles such as the orbital transfer vehicles, orbital maneuvering vehicles, and space station will extensively use reaction jets for orbital maneuvering and attitude stabilization. The proposed robust fuel- and time-optimal control algorithm is used for a three-mass spacing model of flexible spacecraft. A fuel-efficient on-off control logic is developed for robust rest-to-rest maneuver of a flexible vehicle with minimum excitation of structural modes. The first part of this report is concerned with the problem of selecting a proper pair of jets for practical trade-offs among the maneuvering time, fuel consumption, structural mode excitation, and performance robustness. A time-optimal control problem subject to parameter robustness constraints is formulated and solved. The second part of this report deals with obtaining parameter insensitive fuel- and time- optimal control inputs by solving a constrained optimization problem subject to robustness constraints. It is shown that sensitivity to modeling errors can be significantly reduced by the proposed, robustified open-loop control approach. The final part of this report deals with sliding mode control design for uncertain flexible structures. The benchmark problem of a flexible structure is used as an example for the feedback sliding mode controller design with bounded control inputs and robustness to parameter variations is investigated

Robust control of flexible space vehicles with minimum structural excitation: On-off pulse control of flexible space vehicles

Both feedback and feedforward control approaches for uncertain dynamical systems (in particular, with uncertainty in structural mode frequency) are investigated. The control objective is to achieve a fast settling time (high performance) and robustness (insensitivity) to plant uncertainty. Preshaping of an ideal, time optimal control input using a tapped-delay filter is shown to provide a fast settling time with robust performance. A robust, non-minimum-phase feedback controller is synthesized with particular emphasis on its proper implementation for a non-zero set-point control problem. It is shown that a properly designed, feedback controller performs well, as compared with a time optimal open loop controller with special preshaping for performance robustness. Also included are two separate papers by the same authors on this subject

Reaksi dekuaternerisasi N-Isopropil-N-Metilpiperidinium Iodida dengan Trifenifosfin

Metode transformasi amina tersier masih dikembangkan di Laboratorium Kimia Organik UNDIP melalui alkilasi terhadap metil-amina-tersier membentuk garam metil-alkil-amonium-kuatemer, diikuti dekuaternerisasi spesifik untuk menghasilkan alkil-amina-tersier. Guna mencapai tujuan tersebut, pada penelitian ini digunakan N-metilpiperidin sebagai reaktan, yang telah diisopropilasi membentuk N-isopropil-N-metilpiperidinium iodida (tahap 1), diikuti dengan dekuaternerisasi garam amonium tersebut dengan trifenilfosfin (tahap 2). Pada langkah pertama, garam N-isopropil-N-metilpiperidinium iodida telah berhasil diisolasi sebanyak 94 % dalam refluk klorofrom selama 24 jam. Keberadaan senyawa tersebut telah dapat dibuktikan melalui spektroskopi II-I-NMR. Selanjutnya garam amonium ini di-dekuatemerisasi dengan trifenilfosfin sebagai nukleofil dalam refluk DMF selama 18 jam (langkah kedua). Hasil analisis produk-produk dekuaternerisasi menggunakan spektroskopi 1H-NMR menunj ukkan bahwa garam N-isopropil-N-metilpiperidinium iodida telah ter-dekuaternerisasi (84,61 %). Pada kasus ini, ion iodida diusulkan berperan lebih kuat dibandingkan dengan trifenilfosfin. Tertiary Amine transformation method has been developed in Organic Chemistry Laboratory of Diponegoro University by alkylation of methyl-tertiary amine forming methyl-alkyl-quaternary ammonium, followed by spesifie dequatemization to produce alkyl-tertiary amine. In order to accomplished that aims, this research using N-methylpiperidine as the reactant, that is isopropylated to N-isopropyl-N-methylpiperidinium (first step), followed by dequaternization of that ammonium salt with triphenylphosphine (second step). In the first step, N-isopropyl-N-methylpiperidinium iodide was isolated until 94 % in chloroform reflux for 24 hours. The existence of this salt was proved by 'H-NMR spectroscopy. Then, Ammonium salt was dequaternized with triphenyl¬phosphine (PPh3) as nucleophyle in DMF reflux for 18 hours (second step). Analysis result of dequaternization products using 11-1-NMR spectroscopy showed that N¬isopropyl-N-methylpiperidinium iodide salt was dequaternized (84,61 %). In this case, was recommended that the role of iodide ion is stronger t

Periodic-disturbance accommodating control of the space station for asymptotic momentum management

Periodic-disturbance accommodating control is investigated for asymptotic momentum management of control moment gyros used as primary actuating devices for the Space Station. The proposed controller utilizes the concepts of quaternion feedback control and periodic-disturbance accommodation to achieve oscillations about the constant torque equilibrium attitude, while minimizing the control effort required. Three-axis coupled equations of motion, written in terms of quaternions, are derived for roll/yaw controller design and stability analysis. The quaternion feedback controller designed using the linear-quadratic regulator synthesis technique is shown to be robust for a wide range of pitch angles. It is also shown that the proposed controller tunes the open-loop unstable vehicle to a stable oscillatory motion which minimizes the control effort needed for steady-state operations