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Davenport, P. B.

Publications and source records attributed to Davenport, P. B..

15 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Algorithm for in-flight gyroscope calibration

An optimal algorithm for the in-flight calibration of spacecraft gyroscope systems is presented. Special consideration is given to the selection of the loss function weight matrix in situations in which the spacecraft attitude sensors provide significantly more accurate information in pitch and yaw than in roll, such as will be the case in the Hubble Space Telescope mission. The results of numerical tests that verify the accuracy of the algorithm are discussed.

Davenport, P. B.↗
NASA NTRS1988

In-flight determination of spacecraft magnetic bias independent of attitude

A simple algorithm for the in-flight determination of the magnetic bias of a spacecraft is presented. The algorithm, developed for use during the Hubble Space Telescope mission, determines this bias independently of any attitude estimates and requires no spacecraft sensor data other than that from the spacecraft magnetometer(s). Estimates of the algorithm's accuracy and results from a number of numerical studies on the use of this algorithm are also presented.

Davenport, P. B.↗
NASA NTRS1980

Spacecraft momentum management procedures

Techniques appropriate for implementation onboard the space telescope and other spacecraft to manage the accumulation of momentum in reaction wheel control systems using magnetic torquing coils are described. Generalized analytical equations are derived for momentum control laws that command the magnetic torquers. These control laws naturally fall into two main categories according to the methods used for updating the magnetic dipole command: closed loop, in which the update is based on current measurements to achieve a desired torque instantaneously, and open-loop, in which the update is based on predicted information to achieve a desired momentum at the end of a period of time. Physical interpretations of control laws in general and of the Space Telescope cross product and minimum energy control laws in particular are presented, and their merits and drawbacks are discussed. A technique for retaining the advantages of both the open-loop and the closed-loop control laws is introduced. Simulation results are presented to compare the performance of these control laws in the Space Telescope environment.

Chen, L. C.↗
NASA NTRS1973

Rotations about nonorthogonal axes.

Given a desired three-axis reorientation, it is well known that there are, in general, twelve possible sequences of three successive rotations about orthogonal axes which will perform the reorientation. The present paper determines whether the maneuver can or cannot be accomplished with three successive rotations aobut arbitrary (not necessarily orthogonal) axes. This result is then employed to derive conditions on the axes which insure that every rotation may be so generated. The associated angles of all the possible three-legged slews are exhibited by a closed analytical procedure which requires no assumptions concerning the degree of nonorthogonality nor any approximations. The classical orthogonal case (Euler angles) is then an immediate consequence as a special case of the generalized solution.

Davenport, P. B.↗
NASA NTRS1973

Spacecraft reorientation via slewing about nonorthogonal axes

A mathematical procedure was developed which determines the exact slews relative to any known axes. The axes may be completely arbitrary; their coordinates merely reside on a data base which can be changed at any time without affecting the software. Given the desired reorientation, the procedure then determines all of the two-legged or three-legged slews which will accomplish the reorientation. For example, there are 12 possible permutations of three axes, and if they are orthogonal each always has two solutions. The nonorthogonal case, on the other hand, gives some surprising results, including the nonexistence of a solution: Consider a large reorientation where the three axes are nearly collinear. In this connection, it can be shown that every three-axis reorientation can be accomplished by three successive slews, if and only if the middle axis is perpendicular to the other two.

Davenport, P. B.↗
NASA NTRS1971

Slewing about non-orthogonal axes

Three-legged slewing about nonorthogonal axes, solving single-axis reorientations by two successive rotations about arbitrary fixed lines

Davenport, P. B.↗