Alan P Fleming

US Patent:

39840719, Oct 5, 1976

Filed:

Aug 29, 1974

Appl. No.:

5/501545

Inventors:

Alan W. Fleming - Palos Verdes Peninsula CA

Assignee:

TRW Inc. - Redondo Beach CA

International Classification:

B64G 100

US Classification:

244169

Abstract:

An active attitude control apparatus for damping roll/yaw nutation motion within the control deadband of a satellite which is three-axis stabilized to local vertical by means of a pitch biased, body-fixed reaction wheel and offset roll-yaw thrusters. The apparatus is incorporated into a system in which large attitude motion outside the deadband is controlled by means of the offset roll/yaw control thrusters with an accompanying control mechanism for activating the thrusters in an appropriate direction when motion outside the deadband is sensed. The present apparatus includes logic circuitry apparatus to cause a second thruster activation, of the same sense, after each deadband actuated thruster firing, where such a firing in the same sense has not been triggered within a certain elapsed portion of the satellite nutation period, approximately 5/8ths of the period being preferred.

US Patent:

42609429, Apr 7, 1981

Filed:

Apr 17, 1978

Appl. No.:

5/897072

Inventors:

Alan W. Fleming - Palos Verdes Peninsula CA

Assignee:

TRW Inc. - Redondo Beach CA

International Classification:

G05B 2302

US Classification:

318565

Abstract:

Apparatus and a related method for detecting failures of control elements, such as skewed-axis reaction wheels with closed-loop speed control, used in satellite attitude control systems, and for compensating for such failures and thereby maintaining continuity of operation. The apparatus includes a wheel loop model for simulating operation of each of the reaction wheels and speed control loops in the satellite, and for deriving an estimated wheel speed from a command speed for each wheel. By comparing the estimated speed of each wheel with the corresponding actual or observed speed, the apparatus determines whether a failure was occurred in the wheel, or in its control loop. Upon detection of such a failure, the apparatus disconnects driving power from the failed wheel, modifies the corresponding wheel loop model to reflect disconnection of power, and reconfigures a distribution matrix in such a manner that a set of desired momentum commands with respect to the vehicle axes is properly redistributed among the remaining reaction wheels. Compensation is also made for the momentum contributions of failed wheels that continue to spin after being powered down.