Data processing: measuring – calibrating – or testing – Measurement system – Orientation or position
Reexamination Certificate
2002-03-28
2004-04-06
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Orientation or position
Reexamination Certificate
active
06718280
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a measurement device for determining the three-dimensional orientation of a body relative to a reference direction. Instead of a body, only the relative angular position of one edge of the body relative to a reference direction can also be measured with the measurement device. In the same way, with the measurement device for example one axis of symmetry of a body can also be measured, for example the alignment of a satellite antenna (ground station) relative to geographical coordinates. In doing so the body can be stationary or movable and can be represented by a motor vehicle or a machine, or by the human body or an animal body or parts thereof. Furthermore the invention relates to one or more processes for making available an overall measurement result from individual measurement results which are made available by subsystems. Moreover, the invention relates to use of the measurement device for determining the three-dimensional orientation of machines or machine elements such as for example rolls or rollers, and for making available correction information in order to move a maladjusted machine or machine element into an aligned position.
2. Description of the Related Art
For purposes of determining the three-dimensional orientation of a body relative to a reference direction and absolutely within an inertial system, it has been known for some time that precision gyro systems can be used. In addition to mechanical gyros, with a precision which is limited by mechanical boundary conditions, for some time optically-based gyros, especially in the embodiment with a so-called ring laser, have been on the market as high precision direction and orientation measurement devices. One such means is known from patent U.S. Pat. No. 6,195,615. Unfortunately the costs of especially precise instruments of this type are considerable, so that it is of significant importance to distinctly improve the cost/benefit relation of these measurement devices. This is the object of this invention. The invention achieves this object in that redundant design of a gyro-equipped inertial direction measurement system improves its functional properties not only with regard to operating reliability, but also especially with respect to accuracy. At the same time, when using less accurate and economical individual gyro systems, production costs are reduced. In other words: the invention, instead of a gyro system consisting of three individual gyros aligned orthogonally to one another, of which each is estimated at roughly 20,000 euros, now calls for providing one such system which consists for example of eight individual gyros located symmetrically around one axis or a center and which now cost only roughly 5000 euros each. Typically, as claimed in the invention all combinations of 3 out of 8 gyros are used for an individual gyro triad in order to take a host of independent directional measurements with gyro triads formed in this way. Since in the indicated example of 3 out of 8 gyros therefore a total of 56 individual measurement systems which can be evaluated for detection of the angular orientation in space can be described, the accuracy of the desired measurement result with respect to drift and other errors can be significantly increased by averaging and other statistical considerations. At the same time, the indicated measurement systems consisting of three individual gyros each can be mutually checked so that individual gyros with impaired measurement properties as claimed in the invention can be identified during regular operation and optionally shut down. As mentioned, at the same time a certain redundancy is present so that a measurement system of the proposed type upon failure of an individual gyro nevertheless continues to be useful, even if with reduced accuracy. Therefore, as claimed in the invention a measurement device for determining the three-dimensional orientation of a body relative to a reference direction is devised which has a housing for resting on the surface or one edge of a body to be measured which is provided with a plurality of gyro systems for determining the proportional rotary motion around one axis of symmetry at a time assigned to them and which is characterized in that at least four, preferably other individual gyros are present within the housing and are oriented or aligned in the respectively different three-dimensional directions, and all combinations of three individual gyros at a time which can be combined into a so-called gyro triad yielding one initial measurement result at a time which identifies the three-dimensional angular orientation of the measurement device or a body which has made contact with it. This arrangement as claimed in the invention is used such that first a plurality of initial measurement results is made available and then from the plurality of initial measurement results in addition an overall measurement result is determined which (compared to the individual initial measurement results) has a significantly more accurate angular orientation of the measurement device or of a body which has made contact with it.
The number of eight individual gyro systems within an overall system as claimed in the invention is not mandatory. For example four, five, six, etc. gyros or a much larger number can also be used. The chosen number of individual gyros should however lead to a compromise with respect to equipment cost and the attainable increase in accuracy. One such compromise depends apparently also on which cost proportion can be estimated for the required individual arithmetic unit.
SUMMARY OF THE INVENTION
As mentioned, as claimed in the invention it is possible to group the provided individual systems symmetrically around an individual preferred axis. It is likewise possible to distribute the orientation of the individual systems according to the symmetry directions of a regular polyhedron or however roughly statistically over the solid angle (4*Pi). But it should be ensured that the individual orientations with respect to a device-fixed coordinate system can be set or measured relatively accurately. Furthermore, it is important that the direction vectors of three individual gyros at a time are not coplanar. As claimed in the invention, the measured values which are determined by the individual gyros typically in an oblique-angled, three-dimensional coordinate system are converted to a rectangular Cartesian coordinate system. In this way, the output measured value can be expressed for example in Euler angles (pitch, yaw and roll). This conversion is done, in the same manner as statistical computations, by the computer provided in the surrounding housing of the measurement device.
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Orthogonalization of Nonorthogonal Vector Components, Ludvik Pfeifer, Defense Mapping Agency, Washington, DC 20305-3000, pp. 553-559.
Skewed Axis Inertial Sensor Geometry for Optimal Performance, Mark A. Sturza, Litton Systems, Inc., Guidance and Control Systems Division, 5500 Canoga Avenue, Woodland Hills, California 91367-6698, 88-3874-CP, pp. 128-135.
The Effect of Geometry on Integrity Monitoring Performance, Alison Brown and Mark Sturza, NAVSYS Corporation, 18725 Monument Hill Road, Monument, CO 80132, pp. 121-129.
Cherry Stephen J.
Nixon & Peabody LLP
Prüftechnik Dieter Busch AG
Safran David S.
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