Steering control for skewed scissors pair CMG clusters

A method of controlling a spacecraft attitude comprising:

• providing at least two torque generation devices by providing at least two single two axis control moment gyros;
• orienting said torque generation devices so that their torque generation vectors are not collinear;
• selecting a boresight direction fixed relative to the spacecraft body;
• measuring spacecraft attitude using spacecraft sensors and forming corresponding pitch, roll, and yaw signals about the boresight;
• accepting a trajectory command for boresight pitch and roll;
• generating torque commands based on the signals for pitch, roll and yaw about the boresight and the accepted trajectory command for boresight pitch and roll;
• applying the generated torque commands through an actuator law to the at least two torque generation devices;
• providing at least one low authority torque generation devices;
• orienting the low authority devices so that their torque vectors are not coplanar with the torque generation vectors of the at least two torque generation devices;
• accepting a set point or desired history for boresight yaw;
• generating torque commands for the at least one low authority torque device that reduce error between yaw about spacecraft boresight and the desired history during boresight trajectory control;
• and
• modifying the torque commands generated based on the signals for pitch, roll and yaw about the boresight and the accepted trajectory command for boresight pitch and roll to compensate for the torque commands generated for the low authority torque device and maintain precise boresight pitch and roll following.

A method of controlling a spacecraft attitude comprising:

• providing at least two torque generation devices;
• orienting said torque generation devices so that their torque generation vectors are not collinear;
• selecting a boresight direction fixed relative to the spacecraft body;
• measuring spacecraft attitude using spacecraft sensors and forming corresponding pitch, roll, and yaw signals about the boresight;
• accepting a trajectory command for boresight pitch and roll;
• generating torque commands based on the signals for pitch, roll and yaw about the boresight and the accepted trajectory command for boresight pitch and roll;
• applying the generated torque commands through an actuator law to the at least two torque generation devices;
• providing at least one low authority torque generation devices;
• orienting the low authority devices so that their torque vectors are not coplanar with the torque generation vectors of the at least two torque generation devices;
• accepting a set point or desired history for boresight yaw;
• generating torque commands for the at least one low authority torque device that reduce error between yaw about spacecraft boresight and the desired history during boresight trajectory control;
• and
• modifying the torque commands generated based on the signals for pitch, roll and yaw about the boresight and the accepted trajectory command for boresight pitch and roll to compensate for the torque commands generated for the low authority torque device and maintain precise boresight pitch and roll following.

A method of controlling a spacecraft attitude comprising:

• providing at least two torque generation devices;
• orienting said torque generation devices so that their torque generation vectors are not collinear;
• selecting a boresight direction fixed relative to the spacecraft body;
• measuring spacecraft attitude using spacecraft sensors and forming corresponding pitch, roll, and yaw signals about the boresight;
• accepting a trajectory command for boresight pitch and roll;
• generating torque commands based on the signals for pitch, roll and yaw about the boresight and the accepted trajectory command for boresight pitch and roll;
• applying the generated torque commands through an actuator law to the at least two torque generation devices;
• wherein bore sight pitch and roll excursions from the command trajectory are minimized by adding a feedback law acting on the error between the boresight pitch and roll trajectory and the sensed boresight pitch and roll.

A method for steering a spacecraft along a desired boresight trajectory, wherein the spacecraft includes a set of control moment gyros and associated attitude control arrangement gimbaled with respect to the spacecraft body, said method comprising:

• determining trajectory accelerations corresponding to the desired boresight trajectory;
• determining corresponding body accelerations as a function of the desired trajectory accelerations;
• determining control moment gyro gimbal rates as a function of the determined body accelerations;
• and
• generating torque control signals for controlling operation of the, control moment gyro based on the determined gimbal rates.

A method for steering a spacecraft having a skewed scissor pair control movement gyro (SSP CMG) attitude control arrangement gimbaled with respect to the spacecraft body, said method comprising:

• selecting a desired boresight trajectory which is fixed relative to the spacecraft body;
• determining the boresight angular accelerations based on the desired boresight trajectory;
• translating the determined boresight angular accelerations into a set of corresponding SSP CMG gimbal rates;
• determining whether an existing torque capacity of a motor torque drive element associated with each SSP CMG is exceeded by the determined gimbal rates;
• and
• determining new gimbal rates based on a reduced boresight acceleration if the existing torque capacity is exceeded.