초록 ▼

A 3-axis stabilized spacecraft includes roll and yaw magnetic torquers, and a momentum wheel oriented with its spin axis orthogonal to, and pivotable about, the roll axis. Roll control may be applied by pivoting the wheel. Secular increases in pivot angle may result in loss of control authority when

A 3-axis stabilized spacecraft includes roll and yaw magnetic torquers, and a momentum wheel oriented with its spin axis orthogonal to, and pivotable about, the roll axis. Roll control may be applied by pivoting the wheel. Secular increases in pivot angle may result in loss of control authority when the mechanical limits of the pivot are reached. The pivot angle is sensed, and an unloading control loop is closed, by which magnetic torquers are energized to torque the spacecraft, to return the pivot angle toward zero. The unloading control loop includes a bandpass filter, which eliminates constant components of pivot angle offset. This prevents the unload control loop from attempting to maintain the pivot at a position in which the wheel axis is offset from the desired normal to the orbit plane. Consequently, the magnetic torquers do not expend system energy attempting to maintain an undesirable attitude.

대표청구항 ▼

A system for three-axis control of a spacecraft in an orbit about a heavenly body having a center of mass, which orbit defines an orbit plane, said system comprising: a spacecraft body associated with a pitch axis nominally orthogonal to said orbit plane, a roll axis parallel to the direction of orb

A system for three-axis control of a spacecraft in an orbit about a heavenly body having a center of mass, which orbit defines an orbit plane, said system comprising: a spacecraft body associated with a pitch axis nominally orthogonal to said orbit plane, a roll axis parallel to the direction of orbital motion, and a yaw axis extending between the centers of mass of said spacecraft body and said center of mass of said heavenly body; a wheel adapted for being spun about a spin axis, and for producing torques about said spin axis in response to angular acceleration; wheel mounting means for supporting said wheel with said spin axis orthogonal to said roll axis, said wheel mounting means being pivotable about said roll axis; wheel mounting drive means coupled to said body and to said wheel mounting means for driving said wheel about said roll axis in response to a wheel drive signal, whereby said body may be torqued about said roll axis, said wheel mounting means being movable about said roll axis from a nominal position to at least one travel limit; roll attitude sensing means coupled to said body for generating roll attitude signals representative of a desired positioning of said yaw axis of said body relative to inertial space; roll control means coupled to said roll attitude sensing means and to said wheel mounting drive means for comparing said roll attitude signals with signals representing said desired positioning of said yaw axis for forming a roll error signal, and for applying said roll error signal to said wheel mounting drive means, whereby said yaw axis may be positioned by control of said roll, but said wheel mounting drive means may eventually reach said travel limit, whereupon further roll control may not be possible; yaw torquing means coupled to said body and controllable in response to yaw torquer drive signals, for producing torques about said yaw axis in response to said drive signals; spin axis position determining means responsive to the position of said wheel mounting means about said roll axis for generating an unload error signal representative of at least the direction in which said wheel mounting means departs from said nominal position; unload control signal processing means coupled to said spin axis position determining means and to said yaw torquing means, for processing said unload error signal by at least high-pass filtration for generating said yaw torquer drive signals, and for applying said yaw torquer drive signals to said yaw torquing means for unloading said wheel mounting means toward a position in which the constant roll torque generated by the offset of said spin axis from a normal to said orbital plane counteracts the constant component of environmental roll torque.