Method and apparatus for making coordinate measurements

• US 4,961,267 A
• Filed: 11/23/1988
• Issued: 10/09/1990
• Est. Priority Date: 05/23/1987
• Status: Expired due to Term

• Current Assignee: Carl Zeiss Industrielle Messtechnik GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: Carl-Zeiss-Stiftung
• Inventors: Herzog, Klaus
• Primary Examiner(s): Haroian, Harry N.
• Application Number:
  US07/276,471
• Time in Patent Office: 685 Days
• Field of Search: 33/1 M, 33/1 MP, 33/1 PT, 33/503, 33/504, 33/505
• US Class Current: 33/503
• CPC Class Codes: G01B 11/005 coordinate measuring machines
• CPC Class Codes: G01B 5/008 using coordinate measuring machines

Abstract

The invention is directed to a coordinate measuring apparatus which includes an elevation measuring device. The elevation measuring device is connected with a stationary granite table via one or several linkage arms for determining the planar coordinates. Transducers for detecting angular values or pull-out lengths are arranged with respect to the joints or pull-out members of the linkage arms from which these planar coordinates can be computed by a computer. A method of determining the coordinates is also disclosed.

Claims

1. A coordinate measuring apparatus comprising:

surface means for defining a planar surface;

a measuring device mounted on said surface so as to be movable thereon, the measuring device including;

a carrier having a base in contact engagement with said surface;

said carrier defining a guide path extending vertically upwardly from said base;

a measuring head mounted on said carrier so as to be displaceable along said guide path;

said measuring head including a measuring probe responsive to contact in a plurality of spatial directions; and

, position sensing means for measuring the vertical position of said measuring head along said guide path;

linkage means for connecting said measuring device to a fixed reference location on said planar surface;

a plurality of sensing units mounted on said linkage means for measuring the position of said measuring device in said plane;

said linkage means including;

a guide;

a first rotational joint for pivotally mounting said guide at said reference location;

a pull-out arm slideably engaging said guide and having an outer end; and

, a second rotational joint pivotally connecting said outer end to said measuring device;

one of said sensing units being a linear transducer for measuring the pull-out length of said pull-out arm with respect to said guide;

one of the remaining ones of said sensing units being a first angle encoder corresponding to said first rotational joint for measuring the angular position of said arm vis-a-vis said reference location; and

,

an other one of the remaining ones of said sensing units being a second angle encoder corresponding to said second rotational joint for measuring the angular position of said arm vis-a-vis said measuring device.

2. The coordinate measuring apparatus of claim 1, comprising:

computer means connected to the outputs of said position sensing means and said sensing units to receive the signals thereof for computing the position of said measuring probe in a predetermined coordinate system.

13. The coordinate measuring apparatus of claim 2, said fixed reference location being said foot of said table;

and, said linkage means having a first end pivotally connected to said measuring device and a second end pivotally connected to said foot.

3. A coordinate measuring apparatus comprising:

surface means for defining a planar surface;

a measuring device mounted on said surface so as to be movable thereon, the measuring device including;

a carrier having a base in contact engagement with said surface;

said carrier defining a guide path extending vertically upwardly from said base;

a measuring head mounted on said carrier so as to be displaceable along said guide path;

said measuring head including a measuring probe responsive to contact in a plurality of spatial directions; and

, position sensing means for measuring the vertical position of said measuring head along said guide path;

linkage means for connecting said measuring device to a fixed reference location on said planar surface;

a plurality of sensing units mounted on said linkage means for measuring the position of said measuring device in said plane;

said linkage means including;

first and second guides;

a first rotational joint for pivotally connecting said first guide at said fixed reference location;

a second rotational joint for pivotally connecting said second guide to a second fixed reference location on said planar surface;

a first pull-out arm slideably engaging said first guide and having an outer end;

a second pull-out arm slideably engaging said second guide and having an outer end; and

, a third rotational joint pivotally connecting said outer ends to said measuring device;

two of said sensing units being linear transducers for measuring the respective pull-out lengths of said arms with respect to corresponding ones of said guides; and

,

a remaining one of said sensing units being an angle encoder corresponding to one of said rotational joints for measuring the angular position of one of said arms with respect to said measuring device.

4. A coordinate measuring apparatus comprising:

surface means for defining a planar surface;

a measuring device mounted on said surface so as to be movable thereon, the measuring device including;

a carrier having a base in contact engagement with sad surface;

said carrier defining a guide path extending vertically upwardly from said base;

a measuring head mounted on said carrier so as to be displaceable along said guide path;

said measuring head including a measuring probe responsive to contact in a plurality of spatial directions; and

, position sensing means for measuring the vertical position of said measuring head along said guide path;

linkage means for connecting said measuring device to a fixed reference location on said planar surface;

a plurality of sensing units mounted on said linkage means for measuring the position of said measuring device in said plane;

support means connected to said fixed reference location;

a fist holder mounted on said support means;

a second holder mounted on the upper end of said carrier of said measuring device;

a first articulating joint for articulately connecting said first holder to said support means and a second articulating joint for articulately connecting said second holder to said measuring device; and

,

an arm held in said holders for articulately connecting said measuring device to said support means so as to permit movement of said measuring device on said planar surface relative to said support means.

5. The coordinate measuring apparatus of claim 4, said measuring device being disposed entirely beneath said arm so as to be freely rotatable through 360°

on said planar surface.

6. A coordinate measuring apparatus comprising;

surface means for defining a planar surface;

a measuring device mounted on said surface so as to be movable thereon, the measuring device including;

a carrier having a base in contact engagement with said surface;

said carrier defining a guide path extending vertically upwardly form said base;

a measuring head mounted on said carrier so as to be displaceable along said guide path;

said measuring head including a measuring probe responsive to contact in a plurality of spatial directions; and

, position sensing means for measuring the vertical position of said measuring head along said guide path;

linkage means for connecting said measuring device to a fixed reference location on said planar surface;

a plurality of sensing units mounted on said linkage means for measuring the position of said measuring device in said plane;

support means connected to said fixed reference location;

first and second holders;

first and second rotational joints for pivotally connecting said first and second holders to said support means, respectively;

first and second guides;

a third rotational joint for pivotally connecting said first and second guides to the upper end of said carrier of said measuring device;

a first arm held in said first holder and slideably engaging said first guide so as to permit movement of said first guide relative to said first arm;

a second arm held in said second holder and slideably engaging said second guide so as to permit movement of said second guide relative to said second arm; and

,

said measuring device being disposed entirely beneath said arms so as to be freely rotatable through 360°

on said planar surface.

7. The coordinate measuring apparatus of claim 6, said third rotational joint defining a vertical rotational axis (A);

said measuring probe including a contact ball at the outer end thereof; and

, said measuring head being mounted on said carrier so as to cause said contact ball to be in the immediate vicinity of said axis (A).

8. The coordinate measuring apparatus of claim 7, said measuring head being mounted on said carrier so as to cause said axis (A) to pass through said contact ball.

9. The coordinate measuring apparatus of claim 6, comprising:

counter-balancing means for balancing said arms so that the latter apply substantially no weight to said upper end of said carrier of said measuring device.

10. The coordinate measuring apparatus of claim 9, said support means comprising two mutually spaced vertical stands attached to said surface means and extend upwardly of said planar surface to define respective upper ends for receiving corresponding ones of said holders thereon;

and, a rigid transverse member interconnecting said stands at said upper ends thereof, said transverse member being made of a material having a low thermal coefficient of expansion.

11. The coordinate measuring apparatus of claim 10, said third rotational joint defining a vertical rotational axis (A);

and, said arms extending through said guides so as to extend outwardly beyond said axis (A).

12. A coordinate measuring apparatus comprising:

surface means for defining a planar surface;

a measuring device mounted on said surface so as to be movable thereon, the measuring device including;

a carrier having a base in contact engagement with said surface;

said carrier defining a guide path extending vertically upwardly from said base;

a measuring head mounted on said carrier so as to be displaceable along aid guide path;

said measuring head including a measuring probe responsive to contact in a plurality of spatial directions; and

, position sensing means for measuring the vertical position of said measuring head along said guide path;

linkage means for connecting said measuring device to a fixed reference location on said planar surface;

a plurality of sensing units mounted on said linkage means for measuring the position of said measuring device in said plane;

a table having a top plate defining a workpiece surface for receiving a workpiece thereon to be measured by said apparatus;

a narrow foot interposed between said top plate and said planar surface and being configured so as to cause said top plate to overlap said foot to form an annular gap between said top plate and said planar surface; and

,

said base of said measuring device being a large-surface base plate and said carrier extending upwardly from said base plate at only one portion thereof to permit said base plate to be movable under said table and into said gap when said measuring device is moved to said table for making measurements on a workpiece mounted thereon.

14. A coordinate measuring apparatus comprising:

surface means for defining a planar surface;

a measuring device mounted on said surface so as to be movable thereon, the measuring device including;

a carrier having a base in contact engagement with said surface;

said carrier defining a guide path extending vertically upwardly from said base;

a measuring head mounted on said carrier so as to be displaceable along said guide path;

said measuring head including a measuring probe responsive to contact in a plurality of spatial directions; and

, position sensing means for measuring the vertical position of said measuring head along said guide path;

linkage means for connecting said measuring device to a fixed reference location on said planar surface;

a plurality of sensing units mounted on said linkage means for measuring the position of said measuring device in said plane;

said measuring device including first drive means for driving said measuring head along said guide path in the vertical direction; and

,

said apparatus including second drive means for displacing said measuring device horizontally over said planar surface.

15. The coordinate measuring apparatus of claim 14, said measuring device having a center of gravity and said second drive means acting on said measuring device at said center of gravity.

16. The coordinate measuring apparatus of claim 15, said measuring device being movable over a measuring region on said planar surface;

and, said second drive means comprising;

two supports mounted on said surface means adjacent said measuring region;

a first linear drive arranged between said supports and mounted thereon so as to be movable therebetween in a first direction; and

, a second linear drive mounted on said first linear drive for engaging and acting on said measuring device in a second direction transverse to said first direction and for coacting with said first linear drive to move said measuring device on said planar surface within said measuring region; and

,

a rotatable table mounted on said planar surface within said measuring region and defining a surface for receiving a workpiece on which measurements are to be made.

17. A method for determining the coordinate values of a measuring probe with a coordinate measuring apparatus which includes:

a support defining a horizontal planar surface;

a measuring device mounted on said planar surface so as to be displaceable thereon and including;

a carrier having a base in contact engagement with said planar surface, the carrier defining a guide path extending vertically upwardly from said base, a measuring head mounted on said carrier so as to be vertically displaceable along said guide path, said measuring head including a measuring probe with a contact element T_k responsive to contact in a plurality of directions, and position sensing means for measuring the position in elevation of said measuring head along said guide path; and

, linkage means for connecting said measuring device to two fixed reference points on said horizontal planar surface;

the method comprising the steps of;

determining the planar position coordinates (X, Y) of the measuring device for the measuring probe by making two length measurements from said two points on said planar surface, said points having a fixed spacing (b, L) from each other;

determining the angular position δ

₄ of the measuring device about a vertical axis (A) with the aid of an angle encoder;

computing corrective values (X₁, Y₁) for said planar position coordinates (X, Y) from a known distance (h) between said axis (A) and said contact element T_k as well as the measured angular position δ

₄ ;

combining said measured planar position coordinates (X, Y) with said corrective values (X₁, Y₁); and

,

determining the elevation coordinate value (Z) of said contact element T_k by means of said positioning sensing means.

18. The method of claim 17, comprising the further steps of:

determining the tilt angle α

₄ of the measuring device with respect to the vertical coordinate axis with the aid of an ancillary measuring arrangement which provides ancillary measured values;

computing second correction values (X₂, Y₂, Z₁) from said ancillary measured values and said elevation coordinate value (Z); and

, combining said second correction values (X₂, Y₂, Z₁) with the measured position coordinates (X, Y) and with the elevation coordinate value (Z).

19. The method of claim 18, wherein said tilt angle (α

₄) is measured by means of an electronic inclination measuring device mounted on said carrier.

20. The method of claim 18, wherein the measurement of said tilt angle α

₄ is performed with said ancillary measuring arrangement comprising at least three mutually spaced sensors (M₁, M₂, M₃) mounted on said base of said measuring device for measuring the distance to said planar surface.

21. The method of claim 20, comprising determining the topography of said planar surface in a separate measuring process and storing the same in a computer as a two-dimensional corrective matrix;

and, determining said tilt angle α

₄ utilizing said corrective matrix and the measured values of said sensors (M₁, M₂, M₃).

22. The method of claim 17, wherein said planar position coordinates (X, Y) are measured with the aid of laser interferometers.

23. A method for determining the coordinate values of a measuring probe with a coordinate measuring apparatus which includes:

a support defining a horizontal planar surface;

a measuring device mounted on said planar surface so as to be displaceable thereon and including;

a carrier having a base in contact engagement with said planar surface, the carrier defining a guide path extending vertically upwardly from said base, a measuring head mounted on said carrier so as to be vertically displaceable along said guide path, said measuring head including a measuring probe with a contact element T_k responsive to contact in a plurality of directions, and position sensing means for measuring the position in elevation of said measuring head along said guide path; and

, linkage means for connecting said measuring device to a fixed reference point on said horizontal planar surface;

the method comprising the steps of;

determining the planar position coordinates (X, Y) of the measuring device for the measuring probe by making one distance measurement from said reference point on said planar surface and at least one angular measurement from said reference point;

determining the angular position δ

₄ of the measuring device about a vertical axis (A) with the aid of an angle encoder;

computing corrective values (X₁, Y₁) for said planar position coordinates (X, Y) from a known distance (h) between said axis (A) and said contact element T_k as well as the measured angular position δ

₄ ;

combining said measured planar position coordinates (X, Y) with said corrective values (X₁, Y₁); and

,

determining the elevation coordinate value (Z) of said contact element T_k by means of said positioning sensing means.

24. The method of claim 23, comprising the further steps of:

determining the tilt angle α

₄ of the measuring device with respect to the vertical coordinate axis with the aid of an ancillary measuring arrangement which provides ancillary measured values;

computing second correction values (X₂, Y₂, Z₁) from said ancillary measured values and said elevation coordinate value (Z); and

, combining said second correction values (X₂, Y₂, Z₁) with the measured position coordinates (X, Y) and with the elevation coordinate value (Z).

25. The method of claim 24, wherein said tilt angle (α

₄) is measured by means of an electronic inclination measuring device mounted on said carrier.

26. The method of claim 24, wherein the measurement of said tilt angle α

₄ is performed with said ancillary measuring arrangement comprising at least three mutually spaced sensors (M₁, M₂, M₃) mounted on said base of said measuring device for measuring the distance to said planar surface.

27. The method of claim 26, comprising determining the topography of said planar surface in a separate measuring process and storing the same in a computer as a two-dimensional corrective matrix;

and, determining said tilt angle α

₄ utilizing said corrective matrix and the measured values of said sensors (M₁, M₂, M₃).

28. The method of claim 23, wherein said planar position coordinates (X, Y) are measured with the aid of laser interferometers.