US5222023A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Compensated transition for spacecraft attitude control
Assignee: Lanteris Space LLC
•
Filing: 1991-04-02
•
Granted: 1993-06-22
•
Expires: 2011-04-02
Abstract
Abstract An improved method for transitioning a spacecraft from a thruster (5) controlled, station keeping mode to an operational, on-orbit mode, in which attitude control is maintained using internal momentum wheels (3). The method first utilizes a thruster compensation technique to supplement the conventional transition mode control system. This compensation uses empirical thruster data to derate thruster (5) efficiency for extremely short pulse durations necessarily used in transition mode operation. Secondly, a three step deadbeat thruster (5) sequence is employed in which a first pulse linearizes spacecraft (1) motion prior to orienting and stopping nutation. This linearization provides improved accuracy in computing and shortens the waiting time for subsequent thruster (5) firings.
Inventors
- 👤 Tung Y. Liu
- 👤 Scott W. Tilley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 15:32
CPC Classifications
B; B64; B64G; B64G1/00; B64G1/22; B64G1/24; B64G1/38; B64G1/244; B64G1/26
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
119 words
A method for damping nutation in a spacecraft having a control system comprising thrusters and noise filters, by using a modified deadbeat thruster firing sequence, wherein the method comprises the steps: firing a first thruster pulse to linearize spacecraft motion; computing direction and duration of a second thruster pulse firing; allowing a momentum error to reach steady state through a short wait period having a duration of between six and ten seconds; firing the second thruster pulse in order to nutate the spacecraft to an origin point of desired on-orbit operation; waiting one-half of a nutation period as the spacecraft nutates to the origin; and firing a third thruster pulse to stop nutation when the spacecraft reaches the origin.
Claim 2
Independent Claim
119 words
A method for damping nutation in a spacecraft having a control system comprising thrusters and noise filters, by using a modified deadbeat thruster firing sequence, wherein the method comprises the steps: firing a first thruster pulse to linearize spacecraft motion; computing direction and duration of a second thruster pulse firing; allowing a momentum error to reach steady state through a short wait period having a duration of between six and ten seconds; firing the second thruster pulse in order to nutate the spacecraft to an origin point of desired on-orbit operation; waiting one-half of a nutation period as the spacecraft nutates to the origin; and firing a third thruster pulse to stop nutation when the spacecraft reaches the origin.
Claim 3
Independent Claim
140 words
A method for controlling transition from thruster control to momentum wheel control in a spacecraft by compensating for thruster losses in a nutational damping control system, wherein the method comprises the steps: generating empirical loss data for at least one thruster; characterizing the thruster loss data by a polynomial equation of the form: ##EQU3## where EPW is the electrical pulsewidth of the thruster, L is the loss coefficient, and n is a positive non-zero integer; solving extended pulsewidth times from the recursive equation: C(IPW) * L(EPW')=1 where EPW'=C(IPW) * IPW and C(IPW) is the compensation function of the idealized pulsewidth (IPW); quantizing the extended pulsewidth times using the function: EPW=INT((EPW'+1.0)/2.0) * 2.0; implementing the quantized extended pulsewidth times in the nutational damping control system; and firing thrusters by application of pulses of duration determined by the nutational damping control system.
Claim 4
Independent Claim
140 words
A method for controlling transition from thruster control to momentum wheel control in a spacecraft by compensating for thruster losses in a nutational damping control system, wherein the method comprises the steps: generating empirical loss data for at least one thruster; characterizing the thruster loss data by a polynomial equation of the form: ##EQU3## where EPW is the electrical pulsewidth of the thruster, L is the loss coefficient, and n is a positive non-zero integer; solving extended pulsewidth times from the recursive equation: C(IPW) * L(EPW')=1 where EPW'=C(IPW) * IPW and C(IPW) is the compensation function of the idealized pulsewidth (IPW); quantizing the extended pulsewidth times using the function: EPW=INT((EPW'+1.0)/2.0) * 2.0; implementing the quantized extended pulsewidth times in the nutational damping control system; and firing thrusters by application of pulses of duration determined by the nutational damping control system.
Claim 5
Dependent Claim
37 words
The method in claim 2, wherein the step for generating empirical thruster loss data comprises the substeps: operating the thrusters over a range of burn durations; and p1 recording thruster impulse as a function of burn duration.
Claim 6
Dependent Claim
17 words
The method of claim 3, wherein the range of burn durations extends from 0 to 64 msec.
References Cited (Backward Citations)
US3643897A
Cited
US3624367A
Cited
US3866025A
Cited
US3944172A
Cited
US3997137A
Cited
US4023752A
Cited
US3937423A
Cited
US3984071A
Cited
US4288051A
Cited
US4174819A
Cited
US4370716A
Cited
US4386750A
Cited
US4521855A
Cited
US4504032A
Cited
EP0119810A2
Cited
US4537375A
Cited
US4758957A
Cited
US4725024A
Cited
US4927101A
Cited
US4931942A
Cited
US5098041A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1996-06-21 | 1996-12-21 | 1997-06-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2000-06-21 | 2000-12-21 | 2001-06-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2004-06-21 | 2004-12-21 | 2005-06-22 | $7700.00 | Window Closed / Lapsed |