Haijun Shen

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Tracking control laws are developed for a rigid spacecraft using both thrusters and momentum wheels. The model studied comprises a rigid body with external thrusters and with rigid axisymmetric wheels controlled by axial torques. Modified Rodrigues parameters (MRPs) are used to describe the kinematics. The thruster torques and the axial motor torques are(More)
A control law for an Integrated Power/Attitude Control System (IPACS) for a satellite is presented in this paper. Four or more energy/momentum wheels in an arbitrary non-coplanar configuration and a set of three thrusters are used to implement the torque inputs. The energy/momentum wheels are used as attitude control actuators, as well as an energy storage(More)
BACKGROUND Multidrug resistance (MDR) mediated by the overexpression of adenosine triphosphate (ATP)-binding cassette (ABC) transporters, such as P-glycoprotein (P-gp), remains one of the major obstacles to effective cancer chemotherapy. In this study, lipid/particle assemblies named LipoParticles (LNPs), consisting of a dimethyldidodecylammonium bromide(More)
A control law for an Integrated Power/Attitude Control System (IPACS) for a satellite is presented in this paper. Four non-coplanar momentum wheels in a special configuration, and a set of three thrusters are used to implement the torque inputs. The momentum wheels are used as attitude control actuators, as well as an energy storage mechanism, providing(More)
This paper studies the scheduling of servicing multiple satellites in a circular orbit. Specifically, one servicing spacecraft (SSc) is considered to be initially on the circular orbit of the satellites to be serviced. The SSc then rendezvous with each satellite of the constellation and services it until all satellites are visited. The total time is assumed(More)
In this paper, we consider the minimum-time reorientation problem of an axi-symmetric rigid spacecraft with two independent control torques mounted perpendicular to the spacecraft symmetry axis. The objective is to reorient the spacecraft from an initial attitude, with some angular velocity, to a nal attitude with a certain angular velocity in minimum time.(More)
— In this paper, we study the scheduling problem arising from refuelling multiple satellites in a constellation. It is assumed that there is no fuel delivered to the constellation externally. Instead, the satellites in the constellation are assumed to be capable of refuelling each other. The cost of the rendezvous maneuver between two satellites conducting(More)
The minimum-¢V, xed-time, two-impulse rendezvous between two spacecraft orbiting along two coplanar uni-directional circular orbits (moving-target rendezvous) is studied. To reach this goal, the minimum-¢V, xed-time, two-impulse transfer problem between two xed points on two circular orbits is rst solved. This xed-endpoint transfer is related to the(More)