IPC분류정보
국가/구분 |
United States(US) Patent
등록
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국제특허분류(IPC7판) |
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출원번호 |
US-0487364
(1983-04-21)
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발명자
/ 주소 |
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출원인 / 주소 |
- Ford Aerospace & Communications Corporation
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대리인 / 주소 |
Radlo, Edward J.Allen, Kenneth R.Sanborn, Robert D.
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인용정보 |
피인용 횟수 :
17 인용 특허 :
6 |
초록
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Transients and steady state error induced in maneuvering a satellite due to a disturbance torque caused by thrust mismatch or differential in the alignment of thrusters with respect to the center of mass are minimized by introducing a torque balancing bias at the input of a thrust modulator of the t
Transients and steady state error induced in maneuvering a satellite due to a disturbance torque caused by thrust mismatch or differential in the alignment of thrusters with respect to the center of mass are minimized by introducing a torque balancing bias at the input of a thrust modulator of the thrusters prior to sensing position or attitude error. The bias may instantly off-modulate the thruster control signal to cancel the effects of attitude transients before errors develop. Other axes thrusters may be on-modulated instantaneously to compensate for cross-axis torque. The bias may be introduced into the satellite control scheme by manual ground control or in automatic on-board compensation based on stored parameters obtained for example from calibration measurements. Specifically, the torque balancing bias may be developed by reference to thrust mismatch detected and stored during previous maneuvers, thus anticipating expected attitude error without actual detection thereof.
대표청구항
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1. For use in a spacecraft during a change in velocity maneuver, the spacecraft employing a plurality of thrusters, at least a first thruster and a second thruster being disposed to develop mutually counteractive moment arms of thrust relative to at least one axis through a center of mass of the spa
1. For use in a spacecraft during a change in velocity maneuver, the spacecraft employing a plurality of thrusters, at least a first thruster and a second thruster being disposed to develop mutually counteractive moment arms of thrust relative to at least one axis through a center of mass of the spacecraft, said first thruster and said second thruster being capable of developing unequal moment arms of force, a method for counteracting disturbance transients comprising the steps of: storing prior to said manuever a value representative of an estimated disturbance torque; thereafter modulating in response to said stored value one of said first and second thrusters during said maneuver to counteract an actual disturbance torque a sufficient amount to compensate for said actual disturbance torque in order to minimize a net position error without initially detecting said net position error; thereafter detecting said net position error, said net position error being indicative of a difference between said estimated disturbance torque and said actual disturbance torque with respect to said axis; and thereafter modulating in response to a sum of said stored value and said net position error one of said first and second thrusters during said manuever to counteract said actual disturbance torque to further minimize said net position error. 2. The method according to claim 1 wherein said modulating step comprises off-modulating one of said thrusters at an initial time in said maneuver to minimize transient net position error during initial periods of said manuever. 3. The method according to claim 1 wherein said spacecraft includes at least a first thruster and a second counteracting thruster associated with each of a first axis, a second axis and a third axis, said first axis, said second axis and said third axis being orthogonal to one another, wherein said detecting step comprises measuring net position error indicative of net disturbance torque with respect to each one of said first axis, said second and said third axis, and wherein said modulating steps comprise applying a counteracting torque by either on-modulating an off thruster or off-modulating an on thruster during said maneuver. 4. The method according to claim 2 wherein said spacecraft includes at least a first thruster and a second counteracting thruster associated with each of a first axis, a second axis and a third axis, said first axis, said second axis and said third axis being orthogonal to one another, wherein said detecting step comprises measuring said net position error indicative of net disturbance torque with respect to each one of said first axis, said second axis and said third axis, wherein said storing step includes storing at least one value representative of said estimated net disturbanee torque with respect to each one of said first axis, said second and said third axis, and wherein said modulating steps comprise applying a counteracting torque by either on-modulating an off thruster or off-modulating an on thruster during said maneuver. 5. For use in a spacecraft during a change in velocity maneuver, the spacecraft comprising a plurality of thrusters, at least a first thruster and a second thruster being disposed to develop mutually counteractive moment arms of thrust relative to at least one axis through a center of mass of said spacecraft, said first thruster and said second thruster being capable of developing unequal thrust, an apparatus for independently modulating thruster discharge for counteracting disturbance transients comprising: means for generating a value representative of an estimated net disturbance torque for storage prior to said manuever; means for modulating one of said first and second thrusters in response to said estimated disturbance torque value obtained following storae during said maneuver to counteract an actual disturbance torque a sufficient amount to compensate for said actual disturbance torque in order to minimize a net position error without initially detecting said net position error; means for combining said net position error and said estimated disturbance torque value to produce a control value for controlling said modulating means during said maneuver; and means for detecting said net position error, said net position error being indicative of a difference between said estimated disturbance and said actual disturbance torque with respect to said one axis. 6. The apparatus according to claim 5 wherein said modulating means includes means for off-modulating an on thruster and means for on-modulating an off thruster, said modulating means being coupled to receive a stored value in the form of a prebias command. 7. The apparatus according to claim 6 further including means for storing said value representative of said net disturbance torque. 8. The apparatus according to claim 5 wherein said means for generating said value for storage includes a storage means and wherein said generated value is stored aboard said spacecraft. 9. The apparatus according to claim 5 wherein said detecting means is included within a control loop including means for damping said control loop during a change in velocity maneuver. 10. The apparatus according to claim 5 wherein said spacecraft includes at least a first thruster, a second counteracting thruster associated with each one of a first axis, a second axis and a third axis, said first axis, second second axis and said third axis being orthogonal to one another and wherein said detecting means includes means for measuring net position error to generate a difference value indicative of said difference between said estimated disturbance torque and said actual disturbance torque with respect to each of said first axis, said second axis and said third axis and said modulating means comprises means for applying a counteracting torque thrust in response to said control value with respect to a corresponding axis. 11. The apparatus according to claim 9 wherein said spacecraft includes at least a first thruster, a second counteracting thruster associated with each one of a first axis, a second axis and a third axis, said first axis, said second axis and said third axis being orthogonal to one another and wherein said detecting means includes means for measuring net position error to generate a difference value indicative of said difference between said estimated disturbance torque and said actual disturbance torque with respect to each of said first axis, said second axis and said third axis and said modulating means comprises means for applying a counteracting torque thrust in response to said control value with respect to a corresponding axis. 12. The apparatus according to claim 8 wherein said spacecraft includes at least a first thruster, a second counteracting thruster associated with each one of a first axis, a second axis and a third axis, said first axis, said second axis and said third axis being orthogonal to one another and wherein said detecting means includes means for measuring net position error to generate a difference value indicative of said difference between said estimated disturbance torque and said actual disturbance torque with respect to each of said first axis, said second axis and said third axis and said modulating means comprises means for applying a counteracting torque thrust in response to said control value with respect to a corresponding axis. 13. The apparatus according to claim 7 wherein said spacecraft includes at least a first thruster, a second counteracting thruster associated with each one of a first axis, a second axis and a third axis, said first axis, said second axis and said third axis being orthogonal to one another and wherein said detecting means includes means for measuring net position error to generate a difference value indicative of said difference between said estimated disturbance torque and said actual disturbance torque with respect to each of said first axis, said second axis and said third axis and said modulating means comprises means for applying a counteracting torque thrust in response to said control value with respect to a corresponding axis.
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