초록 ▼

A digital system for controlling the attitude of a spacecraft (14), e.g., a satellite, with respect to three orthogonal axes. The system can control satellites (14) in parking orbit, transfer orbit, or final operational orbit, whether or not the satellite (14) employs one or more momentum wheels. A

A digital system for controlling the attitude of a spacecraft (14), e.g., a satellite, with respect to three orthogonal axes. The system can control satellites (14) in parking orbit, transfer orbit, or final operational orbit, whether or not the satellite (14) employs one or more momentum wheels. A processor (2) converts weighted data from spacecraft sensors (12), representing angular orientation and angular velocities about each of the three axes, into thruster pulsetrain signatures to command the firing of each of six thrusters positioned about spacecraft (14), a positive and a negative thruster being positioned to impart both directions of angular momentum about each of the three axes. Each thruster pulsetrain signature is created once every processed error cycle period T1, and contains a varying number of pulses of varying widths. A negative feedback PWPF loop (2, 16, 20, 22, 24) is actuated for each of the three axes, preferably several times each T1 in order to achieve better thruster on/off resolution. The PWPF loops are preferably implemented by digital means. Serial-out shift registers (44, 46) load the thruster pulsetrain signatures into means ( 48, 50, 52, 54) for firing the thrusters, preferably after splitting the signature pulses into clone pulses in order to minimize the impact of errors due to asynchronization between the clock which loads the registers (44, 46) and the clock which shifts these registers. Data extenders (40, 42) eliminate possible gaps caused by asynchronization, and thus prevent unwanted on/off thruster switching.

대표청구항 ▼

An apparatus for controlling the attitude of a spacecraft with respect to each of three orthogonal reference axes, comprising: means for imparting angular velocity to the spacecraft about each of three orthogonal spacecraft axes that are fixed with respect to the spacecraft; means for measuring the

An apparatus for controlling the attitude of a spacecraft with respect to each of three orthogonal reference axes, comprising: means for imparting angular velocity to the spacecraft about each of three orthogonal spacecraft axes that are fixed with respect to the spacecraft; means for measuring the angle between each spacecraft axis and a corresponding one of the reference axes, and for measuring the angular velocity of the spacecraft about each of the spacecraft axes; and means for periodically observing output signals produced by the measuring means and creating in response thereto a pulsetrain signature for each spacecraft axis for aligning said spacecraft axis with its corresponding reference axis; wherein each pulsetrain signature has a varying number of pulses of varying duration, and is loaded into a shift register which piecewise outputs a signal for alternately switching on and off the imparting means for the corresponding spacecraft axis in response thereto; said apparatus further comprising means for splitting each of said pulses into several bits of shorter duration each having the same amplitude as its precursor pulse; wherein the bits are loaded into the shift registers for subsequent piecewise outputting to the imparting means.