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Robust resonance reduction using staggered posicast filters
| Details |
Inventors: Fowell, Richard A.;
Assignee: Hughes Aircraft Company (Los Angeles, CA)
Primary Examiner: Malzahn; David H.
Assistant Examiner:
Attorney, Agent or Firm: Gudmestad; Terje, Denson-Low; Wanda K.
A method for filtering actuator commands for a satellite control system to reduce resonant mode excitation despite uncertain knowledge of the resonance frequencies, due to parameter variations, nonlinearities, and the like. The present method filters the actuator commands with staggered proportional plus delay (posicast) filters having distinct delay values, chosen to provide a desired resonance attenuation over a resonance uncertainty range. The present method may be extended to filter multiple resonances by cascading the staggered filters for each resonance. The present invention has wide application, such as in spacecraft precession and translation maneuvers, as well as gimbaled payload stepping. A particular advantage of the present invention is its direct applicability to fixed-amplitude actuators (such as thrusters and stepper motors), and reduced excitation of resonances at frequencies above those of primary concern. |
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DETAILED DESCRIPTION In order to meet the above and other objectives, the present invention is a method of filtering actuator commands for a satellite control system, for example, to reduce resonant mode excitation despite uncertain knowledge of the resonance frequencies, due to parameter variations, nonlinearities, and the like.
The present invention filters the actuator commands with staggered proportional plus delay (posicast) filters having distinct delay values, chosen to provide a desired resonance attenuation over a resonance uncertainty range.
The present invention may be extended to filter multiple resonances by cascading the staggered posicast filters for each resonance.
The present invention has wide application, such as in spacecraft precession and translation maneuvers, and gimbaled payload stepping.
The present invention achieves the desired level of resonance reduction despite uncertainty in the resonance frequencies.
An advantage of the present invention versus prior art is its direct applicability to fixed-amplitude actuators (such as thrusters and stepper motors), and reduced excitation of resonances at frequencies above those of primary concern.
A satellite control system is designed to move a system with a lightly damped resonance(s) of uncertain frequency so there is little residual ringing after the move.
More specifically, on an HS-601 satellite, for example, the control system is designed to provide movement commands that perform an east-west translational thruster maneuver without undue excitation of solar panel bending modes.
The present invention filters the movement commands through at least two proportional plus delay (posicast) filters with staggered zeros bracketing the expected frequency of the resonance(s) of concern, to provide a desired level of attenuation of any resonance within the frequency uncertainty range.
The present invention thus uses cascaded, staggered, proportional plus delay (posicast) filters to avoid excitation of lightly damped resonances where the delays of the cascaded filters are distinct and the filters are designed to guarantee a desired resonance attenuation over a finite frequency range
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Control Computers 
