Dan Liu

US Patent:

8380370, Feb 19, 2013

Filed:

Jun 18, 2009

Appl. No.:

12/487187

Inventors:

Dan Y. Liu - Rancho Palos Verdes CA, US
Richard Y. Chiang - Torrance CA, US

Assignee:

The Boeing Company - Chicago IL

International Classification:

B64G 1/24

US Classification:

701 13, 701 3, 701 4, 701 11, 701400, 701408, 701501, 701505, 701512, 701513, 701523, 701534, 2441581, 2441584, 2441588, 244164, 244165, 244171, 2441711, 2441726

Abstract:

A system and a method for commanding a spacecraft to perform a three-axis maneuver purely based on “position” (i. e. , attitude) measurements. Using an “inertial gimbal concept”, a set of formulae are derived that can map a set of “inertial” motion to the spacecraft body frame based on position information so that the spacecraft can perform/follow according to the desired inertial position maneuvers commands. Also, the system and method disclosed herein employ an intrusion steering law to protect the spacecraft from acquisition failure when a long sensor intrusion occurs.

US Patent:

8620496, Dec 31, 2013

Filed:

Jul 23, 2008

Appl. No.:

12/178440

Inventors:

Dan Y. Liu - Rancho Palos Verdes CA, US
Qinghong W. Wang - Torrance CA, US
Richard Y. Chiang - Torrance CA, US

Assignee:

The Boeing Company - Chicago IL

International Classification:

B64G 1/38
B64G 1/28

US Classification:

701 13, 244165, 244170

Abstract:

A system for damping nutation and removing wobble of a spacecraft spinning about a given axis is provided. The system includes a sensor configured to determine three dimensional attitude measurements of the spacecraft, a processor operatively coupled to the sensor and configured to execute a process that facilitates aligning the spin axis with a spacecraft momentum vector. The processor, when executing the process, is programmed to receive spacecraft attitude data from the sensor, determine a torque command using the received attitude data, and control a momentum storage actuator on the spacecraft using the determined torque command such that an angular deviation about the given axis is reduced.

US Patent:

53101430, May 10, 1994

Filed:

Jun 10, 1993

Appl. No.:

8/075843

Inventors:

John F. Yocum - Rancho Palos Verdes CA
Dan Y. Liu - Rancho Palos Verdes CA
Richard A. Fowell - Culver City CA
Douglas J. Bender - Redondo Beach CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

B64G 124

US Classification:

244164

Abstract:

The three axes thruster modulation (8) of the present invention accepts three axes of input torque commands or angular acceleration commands and generates thruster selection and thruster timing (40) information which is used to fire thrusters (48) for the purpose of spacecraft attitude control and velocity change maneuvers. The modulation logic (8) works in all three axes simultaneously and is suitable for use with an arbitrary thruster configuration, including a configuration in which individual thrusters or thruster groups do not produce torques about mutually orthogonal axes. After thruster selection and on-times have been determined, the modulation logic (8) uses this information to compute a best estimate of the actual rate change (42) which is then compared to the commanded rate change (44) to develop a residual unfired rate change. The residual unfired rate change is retained and fed forward for addition to the subsequent acceleration command in computing the commanded rate change for the subsequent sample period (10, 20, 30). As a result, all commanded rate changes will ultimately be fired even if the commanded rate change is below a minimum rate change achievable.

US Patent:

53114353, May 10, 1994

Filed:

Nov 27, 1991

Appl. No.:

7/800660

Inventors:

John F. Yocum - Rancho Palos Verdes CA
Dan Y. Liu - Rancho Palos Verdes CA

Assignee:

Hughes Aircraft Company - Los Angeles CA

International Classification:

G01C 2100
G06G 778

US Classification:

364459

Abstract:

A method of attitude control for spacecraft with flexible structures utilizes an estimator/state controller pair with on-board time-varying gain scheduling. The control method includes an attitude estimator (100) for each axis, which uses rate input from inertial reference sensors (4, 5, 6) to produce estimates (37, 38, 39) of each of the state variables. The estimator employs a predictor-corrector structure which computes initial rate and position estimates for each sample interval and corrects these values by weighing them with iteratively-calculated time-varying gains according to equations 35 and 36. The state controller (40) for each axis operates on these inputs, combining them with position and rate commands (41, 42) and weighing the results with time-varying gains calculated iteratively for each sample period according to equations 46, 47, and 48. The final result is a commanded control acceleration (50) which is forwarded to a thruster modulation logic.