DIGITAL PWPF THREE AXIS SPACECRAFT ATTITUDE CONTROL

摘要

DIGITAL PWPF THREE AXIS SPACECRAFT ATTITUDE CONTROLAbstractA digital system for controlling the attitude of aspacecraft (14), e.g., a satellite, with respect to threeorthogonal axes. The system can control satellites (14) inparking orbit, transfer orbit, or final operational orbit,whether or not the satellite (14) employs one or moremomentum wheels. A processor (2) converts weighted datafrom spacecraft sensors (12), representing angularorientation and angular velocities about each of the threeaxes, into thruster pulsetrain signatures to command thefiring of each of six thrusters positioned about spacecraft(14), a positive and a negative thruster being positionedto impart both directions of angular momentum about each ofthe three axes. Each thruster pulsetrain signature iscreated once every processed error cycle period T1, andcontains a varying number of pulses of varying widths. Anegative feedback PWPF loop (2, 16, 20, 22, 24) is actuatedfor each of the three axes, preferably several times eachT1 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 thrusterpulsetrain signatures into means (48, 50, 52, 54) forfiring the thrusters, preferably after splitting thesignature pulses into clone pulses in order to minimize theimpact of errors due to asynchronization between the clockwhich loads the registers (44, 46) and the clock whichshifts these registers. Data extenders (40, 42) eliminatepossible gaps caused by asynchronization, and thus preventunwanted on/off thruster switching.