Data processing: measuring – calibrating – or testing – Measurement system – Speed
Reexamination Certificate
1998-07-21
2001-08-14
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Speed
C378S901000
Reexamination Certificate
active
06275780
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to photogrammetry, and more particularly to rotational axis determination utilizing photogrammetric data.
The successful operation of certain rotating devices, such as a flight dual axis drive for positioning antennas, is dependent largely on the ability to maintain proper alignment of the device about its rotational axis. To maintain such alignment, data related to the average axis of rotation must typically be collected. Conventional techniques for determining the average axis of rotation are generally ineffective and inaccurate. Even in the absence of such problems, these techniques rely upon manual operation and repeated readings, and are thus extremely slow. For example, optical instruments, such as multiple theodolites, are typically utilized in conjunction with mirrors to measure the average axis of rotation. A conventional theodolite typically includes a telescope, mounted to be rotatable about vertical and horizontal axis, and horizontal and vertical circular is scales against which the angular position of the telescope can be measured, after it has been aligned on a remote target. Data representing the bearing or azimuthal direction of the target from the theodolite location and elevational angle of the target above or below the horizontal is attained. This technique, however, requires a human observer to both align the telescope on the target and read the azimuthal and elevational data from the circular scales. Since manual operation and repeated readings are required, this technique is extremely slow (typically requiring 4 to 6 weeks), costly and subject to error.
What is needed therefore is an apparatus and method which is accurate and time and cost efficient for determining the average axis of rotation for a rotational device.
SUMMARY OF THE INVENTION
The preceding and other shortcomings of the prior art are addressed and overcome by the present invention which provides, in a first aspect, an apparatus and method for computing the average axis of rotation for a rotational device which utilizes photogrammetric data derived from a rotational device in conjunction with an iterative algorithm to determine the average axis of rotation within a desired resolution. The input photogrammetric data is determined by photogrammetry. In particular, a target plate including a plurality of targets is installed on each rotational axis, the targets are photogrammetrically measured at an initial rotational position, the target plate is rotated to a different position and the targets are photogrammetrically measured at the new position. As the measurement process is repeated for different positions, the present invention transforms each set of photogrammetric measurements from each rotational position into a common coordinate system to generate photogrammetric data points and inputs each set of data points from each rotational position into the algorithm to determine the average axis of rotation of the device within a desired resolution. The algorithm, via an iterative process, calculates the average axis of rotation from the input photogrammetric data by assigning each photogrammetric data point a unique identification, determining vectors based upon data points positioned approximately 180 degrees apart and determining the average axis of rotation by the resulting vector's rotation about the drive axis.
The foregoing and additional features and advantages of this invention will become apparent from the detailed description and accompanying drawing figures below. In the figures and the written description, numerals indicate the various features of the invention, like numerals referring to like features throughout both the drawing figures and the written description.
REFERENCES:
patent: 4643574 (1987-02-01), Muller
patent: 5294972 (1994-03-01), Kemmler
patent: 5552883 (1996-09-01), Busch-Vishniac et al.
patent: 5719674 (1998-02-01), Martin et al.
patent: 5758429 (1998-06-01), Farzan et al.
patent: 5963613 (1999-10-01), Navab
Glick Gary L.
Jones Donald L.
Hoff Marc S.
Keller Robert W.
Raymond Edward
TRW Inc.
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