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US 4,587,622 AGranted
Method and apparatus for determining and correcting guidance errors
AssigneeCarl-Zeiss-Stiftung, Heidenheim/Brenz
InventorKlaus Herzog
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AssigneeCarl-Zeiss-Stiftung, Heidenheim/Brenz
InventorKlaus Herzog
Estimating the term…
Two methods are disclosed for eliminating the influence of guidance errors on the precision of determining the position of guided machine parts as in a coordinate-measuring machine, whereby the resulting measurement may be provided with a correction which is dependent on the guidance error. In a first method of the invention, the relevant guidance errors of the machine are determined and approximated by correction functions which are stored in the computer of the machine; the stored correction functions are used for automatic correction of errors otherwise inherent in operation of the coordinate-measuring machine. In a second method of the invention, additional measuring devices are mounted to displaceable parts of the machine, and these devices respond to changes in offset distance from reference surfaces arranged parallel to applicable coordinate guides; these measurement devices provide continuous detection of guidance errors, throughout the measurement process.
In a measuring machine (i) wherein a rectilinear guide establishes a path of longitudinal guidance in the course of displacement of a movable part with respect to a fixed part of a given plane, (ii) wherein said parts longitudinally overlap for a predetermined fraction of the maximum extent of longitudinal guidance, and (iii) wherein means including an incremental scale and a scale-reading device measure displacement along said path, a longitudinally extending scale and two scale-reading transducers for determining deviations from a desired straight path of displacement, said scale being a fixed feature of said fixed part and comprising a plurality of uniformly and closely spaced parallel longitudinally extending lines which are strictly parallel to each other and which establish a basis of parallel reference to the desired straight-line path over the longitudinal extent of said path, the lines of said scale being parallel to said given plane and extending the length of said path, said transducers being carried at predetermined longitudinal spacing near the repective longitudinal ends of said movable part and effectively spanning the extent of said overlap, each of said transducers producing a change in transverse measurement in response to any traversing incremental scan displacement with respect to one or more of the lines of said scale;
In a measuring machine (i) wherein a rectilinear guide establishes a path of longitudinal guidance in the course of displacement of a movable part with respect to a fixed part in a given plane, (ii) wherein said parts longitudinally overlap for a predetermined fraction of the maximum extent of longitudinal guidance, and (iii) wherein means including an incremental scale and a scale-reading device measure displacement along said path, a straight-line reference and two longitudinally spaced transducers for determining deviations from a desired straight path of displacement, said straight-line reference being a fixed feature of said fixed part and extending over the longitudinal extent of said path, said transducers being oriented transverse to said straight-line reference for measuring response to instantaneous offset from said reference in a plane parallel to said given plane, said transducers being carried at predetermined longitudinal spacing near the respective longitudinal ends of said movable part and effectively spanning the extent of said overlap, each of said transducers producing a digital output for measurement of offset with respect to said straight-line reference;
In combination, a measuring reference comprising an elongate rigid body having a straight flat scale surface with a first plurality of uniformly and closely spaced parallel lines which extend for the longitudinal extent of said body and a second set of plural uniformly and closely spaced parallel lines which are transversely offset from said first plurality and which are oriented transverse to the elongate dimension of said body, a longitudinally guided deviation-tracking device spanning a predetermined fraction of the length of said rigid body, a first two scale-reading transducers carried by said device at longitudinal spacing and facing said first plurality of lines, the longitudinal extent of said parallel lines exceeding the longitudinal spacing of said transducers, each of said transducers producing a digital response to any traversing incremental scan displacement with respect to one or more of the lines of said first plurality, and a third transducer facing lines of said second set and producing a digital response to any traverse of the lines of said second set.
In combination, a measuring reference comprising an elongate rigid body having a straight flat scale surface with a plurality of uniformly and closely spaced parallel lines which extend from the longitudinal extent of said body, a longitudinally guided deviation-tracking device spanning a predetermined fraction of the length of said rigid body, and two-scale reading transducers carried by said device at longitudinal spacing and facing said first plurality of lines, each of said transducers producing a digital response to any traversing incremental scan displacement with respect to one or more of the lines of said first plurality.
A measuring reference comprising an elongate rigid body of rectangular cross-section with first, second and third scales respectively on first, second and third elongate surfaces of said body, each of said scales comprising a plurality of uniformly and closely spaced parallel lines which extend for the longitudinal extent of said body.
In a measuring machine wherein a rectilinear guide establishes a path of longitudinal guidance in the course of displacement of a movable part with respect to a fixed part in a given plane, and wherein said parts longitudinally overlap for a predetermined fraction of the maximum extent of longitudinal guidance, and wherein incremental distance is measured for displacement along said path, the method of using two longitudinally spaced transducers on said movable part to determine and correct errors in lognitudinal guidance which comprises:
Dependencies are inferred from the claim text.