초록 ▼

A method for controlling transition from thruster control to momentum wheel control to minimize nutation angle and transition time in a three-axis stabilized spacecraft employing an internal body fixed-momentum wheel as an attitude stabilizer. The method employs direct, substantially real-time measu

A method for controlling transition from thruster control to momentum wheel control to minimize nutation angle and transition time in a three-axis stabilized spacecraft employing an internal body fixed-momentum wheel as an attitude stabilizer. The method employs direct, substantially real-time measurement of momentum components and angular rates and generates paired roll thrust impluses and paired yaw thrust impulses in synchronization with the nutation period of the spacecraft to drive the spacecraft to a state of substantially zero nutation. The controller employs a deadbeat principle in a closed-loop real-time feedback system. In a preferred embodiment, the impulsive thruster firing commands in roll and yaw are simultaneous, spaced one-half nutation period apart in time with the effect that the target momentum is achieved in one to three pairs of impulse firings. The invention provides, with minimum transient overshoot, automatic reduction of angular momentum relative to a desired on-orbit state to a level which can be managed by a low-authority momentum wheel controller.

대표청구항 ▼

In a three-axis stabilized spacecraft employing an internal body-fixed momentum wheel as an attitude stabilization means and characterized by a nutation period, an apparatus for controlling transition from thruster control to momentum wheel control to minimize nutation angle and transition time, sai

In a three-axis stabilized spacecraft employing an internal body-fixed momentum wheel as an attitude stabilization means and characterized by a nutation period, an apparatus for controlling transition from thruster control to momentum wheel control to minimize nutation angle and transition time, said apparatus comprising: sensor means for obtaining values representative of spacecraft roll angle, spacecraft yaw angle, spacecraft roll rate and spacecraft yaw rate; and means coupled to said sensor means for controlling firing of spacecraft roll and yaw attitude control thrusters at intervals of substantially one-half of said nutation period, including means for calculating a spacecraft transverse angular momentum vector at intervals of one-half of said nutation period from spacecraft moments of inertia and said values representative of spacecraft roll angle, spacecraft yaw angle, spacecraft roll rate and spacecraft yaw rate, said transverse angular momentum vector comprising a roll component and a yaw component, means for computing from said values representative of spacecraft roll angle, spacecraft yaw angle, spacecraft roll rate and spacecraft yaw rate a firing duration for said attitude control thrusters for causing spacecraft motion following thruster firing to reduce nutation amplitude toward a transverse angular momentum of zero, means for causing firing of said roll and yaw attitude control thrusters according to said firing duration, and timing means for sequencing firing of said roll and yaw attitude control thrusters at intervals of substantially one-half of said nutation period of said spacecraft.