An effective algorithm for the finite-horizon linear quadratic continuous terminal control is proposed. It is the combination of existing continuous soft and hard terminal control. We apply the algorithm to the automatic landing control of OH-6A helicopters. Numerical demonstration shows that, whether noise exists or not, the algorithm has less computation time and less feedback gains than existing hard terminal control while generally achieving the same terminal accuracy. The optimization problem which represents the hard terminal control can be addressed by sweep method and transit matrix method. It is also discovered that transit matrix method is a crucial point for improving terminal accuracy.
On the possible influence of Rocket 2nd booster or debris (i.e., by-product of the separation) to radar observation, the concept of ROIO (Radar Overlapped Image Orbit) is introduced. In this paper, the geometry between the radar location and the trajectory plane are described, the orbit determination method of ROIO in space is also proposed, the case of two or more radars is discussed and the influence caused by the earth's rotation is analyzed as well. Simulation results indicate that the influence is neglectable; the original orbit's ROIOs are determined by radar observation range and the geometry between the radar's location and the trajectory plane. Finally, some recommendations are presented on how to avoid ROIOs to affect the determination of the target's orbit.
Fig.l.LVLH frame to describe the relative motion referring to target the same time. In our work, at one hand we try to solve the terminal proximity problem taking the coupling into account. The linearzing error of the relative model, measurement noise of relative velocity and position and the misalignment of the thruster are also taken into consideration. At the other hand the adverse of the orbital control acting on the attitude control system are also considered when design the attitude tracking controller. The outstanding feature is that the orbital control and attitude control command are implemented by the same thrusters system. Our control method have good prospect for engineering practice.The rest ofthis paper is organized as following. In section II the orbital tracking control problem, the attitude tracking problem and the coordination problem between orbital and attitude control are formulated. In section III the linear H 00 model reference controller for orbital control and the nonlinear H 00 controller for attitude control are designed. The coordination method is also given. In section IV the simulation scenario and results are given. Section Vconclude this paper. II. PROBLEM FORMULATIONA. The proximity tracking control problem formulation Referring to Fig.l, assume there is a target spacecraft in a circle orbit. Attached to the target center of mass is a right-handed local-vertical-local horizontal (LVLH) frame, with the z-axis downward along the vector R to the center of mass of the earth; the x-axis along the target velocity vector V and perpendicular to the z-axis; and the y-axis completing the right-handed frame.In the LVLH frame, the location of chaser spacecraft is (x,y,z) , and its velocity is(~~,r~v,~~).When the chaser approaches the target, its relative velocity must be diminished to safe limits. This requirement can be fulfilled by tacking a traj ectory along which the velocity decays exponentially [6]. We adopt a widely used glideslope scheme which is illustrated by Fig.2. The speed jJ must diminish with p . jJ is obtained by differentiating p .Since the proximity time is very short, we can treat the LVLH frame as an inertial target sapcecraftAbstract-In the final proximity of rendezvous, linear H 00 and nonlinear H 00 control method are adopt for orbital tracking control and attitude tracking control respectively. We use the same thrusters system to implement orbital and attitude control command simultaneously. Because of the coupling caused by implementation, orbital control and attitude control command may conflict; we adopt a logic coordination method to avoid this situation. To the best of our knowledge, this is the first solution for orbital and attitude coupling control by the same implementation system in the final proximity of rendezvous. Numerical simulation verifies the validity and feasibility.I.
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