Mechanisms to determine position and orientation in space

• US 4,676,002 A
• Filed: 12/20/1985
• Issued: 06/30/1987
• Est. Priority Date: 06/25/1984
• Status: Expired due to Fees

• Current Assignee: Alexander H. Slocum
• Original Assignee: Alexander H. Slocum
• Inventors: Slocum, Alexander H.
• Primary Examiner(s): Little, Willis
• Application Number:
  US06/811,737
• Time in Patent Office: 557 Days
• Field of Search: 33/1 MP, 33/1 N, 33/1 PT, 33/1 M, 33/503, 33/504, 33/185 R, 901/45, 901/9
• US Class Current: 33/1.0MP
• CPC Class Codes: B25J 13/088 with position, velocity or acceleration sensors
• CPC Class Codes: B25J 17/025 mounted in series
• CPC Class Codes: B25J 18/002 comprising beam bending compensation means
• CPC Class Codes: B25J 19/02 Sensing devices
• CPC Class Codes: B25J 9/046 Revolute coordinate type

Abstract

A system to move an object in space. The system includes a structural mechanism having interconnected structural beams for applying translational forces and movements to position an object held by the structural mechanism. The system has a measuring mechanism to determine, with precision, the actual position and orientation of each structural beam with respect to its attached neighboring structural beam. The structural mechanism includes at least one structural beam and an associated measuring beam. The measuring beam is in contact only with its associated structural beam, the contact being effected through support devices that provide the only physical contact between the structural beam and the associated measuring beam.

Claims

1. A system to move an object in space, that comprises:

an articulated structural mechanism for applying forces and moments to position an object held by the structural mechanism, said structural mechanism comprising a plurality of structural beams, a measuring beam associated with each structural beam, each measuring beam being in contact only with the associated structural beam, each said structural beam further including support device means that provides the only physical contact between the structural beams and the associated measuring beam such that the structural beam applies no significant loads on the associated measuring beam; and

measuring means, which includes said measuring beam, operable to determine the actual position and orientation of said each structural beam with respect to a spatial reference.

2. A system according to claim 1 wherein the structural mechanism comprises two structural beams connected together in an articulated arrangement with adjacent ends of adjacent associated measuring beams slightly spaced apart from one another but in close proximity to one another and in which the measuring means includes sensors that note the spatial relationship or orientation of one measuring beam with respect to the adjacent measuring beam.

3. A system according to claim 1 wherein the associated measuring beam is supported at each end thereof by a support device that supplies the only connecting between the measuring beam and its associated structural beam.

4. A system according to claim 1 wherein said measuring beam is in contact only with the support device means, of the associated structural beam said support device means being located to position the measuring beam always essentially parallel to the associated structural beam.

5. A system according to claim 4 in which the support device means holds the measuring beam essentially parallel to the associated structural beam in a manner which causes the measuring beam to be subject to loads due only to its own weight.

6. A system according to claim 5 in which the support device means comprises a pair of support devices to support the measuring beam with reference to its associated structural beam, with the measuring beam length-to-diameter ratio greater than about five, said pair of support devices being respectively a two-degree-of-freedom anchoring device that support one end of the measuring beam and a four-degree-of-freedom anchoring device that supports the other end of the measuring beam.

7. A system according to claim 6 in which said two-degree-of-freedom anchoring device holds one end of said measuring beam to one end of said structural beam such that the two degrees of freedom are provided for the measuring beam to move with respect to the structural beam and provide said two degrees of freedom in a way that allows small rotations about two orthogonal axes.

8. A system according to claim 7 in which said small rotations are no greater than the order of five angular degrees.

9. A system according to claim 6 wherein the four-degree-of-freedom anchoring device for holding the other end of said measuring beam to the other end of said structural beam permits four degrees of freedom whereby the measuring beam is allowed to move with respect to the structural beam in small rotations about three orthogonal axes and in small linear motion along one axis.

10. A system according to claim 9 wherein the small rotations are no greater than about five angular degrees and the small linear motion is no greater than about one centimeter.

11. A system according to claim 6 wherein the two-degree-of-freedom anchoring device is a two-degree-of-freedom gimbal and wherein the four-degree-of-freedom anchoring device is a four-degree-of-freedom gimbal.

12. A system according to claim 11 wherein each gimbal is a gimbal mechanism that uses wires to support the measuring beam, said wires being arranged to provide two small degrees of freedom at one end and four small degrees of freedom at the other end of said measuring beam.

13. A system according to claim 6 that comprises a plurality of measuring beams, each with an associated structural beam that supplies support, through said anchoring devices to its associated measuring beam, forming an articulated structure, wherein said measuring means is adapted to measure six degrees of freedom between each set of adjacent ends of the measuring beams without transferring any loads from one measuring beam to the other.

14. A system according to claim 13 wherein the measuring means measures one large degree of freedom and five small degrees of freedom, which measuring means comprises sets of juxtaposed plates that serve as plate-pairs, one plate being mounted on each free end of each measuring beam, said plates having sensors that determine the position and orientation of one adjacent plate with respect to the other, juxtaposed, plate.

15. A system according to claim 14 wherein the two plates in a plate-pair are disposed essentially parallel to each other.

16. A system according to claim 14 wherein said measuring means includes distance-measuring devices and position-measuring devices to determine the position and orientation of said plates with respect to each other.

17. A system according to claim 14 wherein the measuring means includes position measuring means comprising an array of at least two light sources attached to one of said plates and at least one position-measuring device mounted to the other plate, said line sources and said position-measuring device being used in determining the translational position and rotational orientation of one said plate with respect to the other said plate.

18. A system according to claim 17 wherein the two light sources are lasers or other light sources which remain sufficiently collimated over the distance between said plates.

19. A system according to claim 17 in which the position-measuring device contains a photo-sensitive diode device.

20. A system according to claim 17 in which the position-measuring device contains an array of photo-sensitive diodes.

21. The system of claim 17 in which the position measuring means comprises a plurality of position measuring devices, in which each position-measuring device is photo sensitive and in which the measuring means is configured such that at least one line source is always able to project onto the sensor surface of each said position-measuring device.

22. The system of claim 21 wherein the position-measuring means comprises a configuration to determine translation and rotation of said juxtaposed plates in a plate-pair with respect to one another.

23. The system of claim 17 wherein the position-measuring means comprises a single photo-sensitive device and in which the measuring means is configured to provide radiation from two said light sources which always projects onto the photo-sensitive region of said single photo-sensitive position-measuring device.

24. The system of claim 23 wherein the position-measuring means comprises a configuration to determine translation and rotation of said juxtaposed plates in a plate-pair with respect to one another.

25. A system according to claim 17 wherein the measuring means uses three distance-measuring devices to measure the separation of the juxtaposed plates in a plate-pair and their angular orientation (nonparallelism), which information is combined with information from the photo-sensitive position-measuring means to uniquely determine the relative position and orientation of said juxtaposed plates in a plate-pair and, hence, of said adjacent measuring beam.

26. A system according to claim 13 wherein the terminal endpoint of the ultimate structural beam holds an end effector plate used for attaching end effectors (grippers, etc.), and an ultimate measuring beam, with a length-to-diameter ratio less than about five, anchored rigidly to the end effector plate, the other end of the ultimate measuring beam being free floating or unrestrained.

27. The system of claim 26 wherein the position and orientation of the ultimate measuring beam with respect to the penultimate measuring beam is determined by measuring the relative position and orientation of two plates, one plate being attached to the respective ends of each of the ultimate and penultimate measuring beam.

30. The measuring beam system of claim 1 wherein said measuring beams are made from hollow tubular beams which employ mirrors in the regions where the measuring beams meet to enable a light beam to be beamed through the center of each measuring beam, said light beam being directed to the end of the terminal measuring beam system where it does useful work.

28. A sensor to measure one large rotational degree of freedom, two small rotational degrees of freedom and three small translational degrees of freedom, comprising:

a substantially flat plate with a circular raised portion extending out of the plane of the plate, the cross dimensions of the raised portion being smaller than the cross dimensions of the plate;

a ring with bumps formed in it at the inner surface thereof, the ring being placed adjacent to but spaced from the plate such that the bumps face the raised portion of in a nested configuration wherein the raised portion is the outer beam and is free to revolve about an axis that is common to the ring and the circular raised portion said ring having a planar surface juxtaposed with respect to the flat plate and facing the flat plate;

at least three first non-contacting distance measuring devices which measure the distance between the flat plate and said planar surface; and

at least three further non-contacting distance measuring devices which measure the distance between said raised inner surface of the flat plate and said bumps on the ring such that one sensor is alway reading distance between said raised surface and the steepest sloping part of a bump.

29. A sensor to measure angular rotation and position of two beams configured to permit relative rotation between the beams that comprises:

a first beam of the two beams, having a series of fine bumps disposed in a circular configuration and at least three non-contacting measuring devices disposed in a circular nested fashion with respect to the circularly-disposed series of fine bumps, the measuring devices being spatially out of phase with one another with respect to the bumps so that one sensor of the three sensor senses the peak of a bump, another sensor senses the ramp of a bump, and the other sensor senses the trough between bumps, the combined sensor serving to provide angular and position (runout of the angular motion axis) information with respect to the two beams.

31. A system that comprises:

a plurality of links in an articulated arrangement, each link comprising a structural beam, a measuring beam and connecting means to attach the measuring beam to the structural beam to provide three degrees of freedom between the measuring beam and the structural beam such that deflections of the structural beam do not impose any significant load on the measuring beam, said connecting means providing the only connection between the structural beam and the measuring beam.

32. A system according to claim 31 in which the structural beam is a hollow elongated member, in which the measuring beam is disposed within the structural beam and along the axis of the structural beam, and in which the measuring beam is connected only at each end thereof to the respective end of the structural beam.

33. A system according to claim 31 in which said deflections are small motions of said structural beam resulting from loads on said structural beam, said motions include small angles of twist about the axis of the structural beam and small bending movements about the transverse axes of the structural beam.

34. A system according to claim 33 in which said small motions induce less than about 5% strain on the structural members.

35. A system according to claim 31 in which each link of the plurality of links is like said link, a first link being rotatably connected at one end thereof to an anchor and being rotatably connected by a joint at the other end thereof to a second link of the linkage, said system including measuring means and said measuring beam operable to establish spatial relationship of the measuring beam of the first link with respect to the anchor at said one end thereof and said other end thereof with respect to the measuring beam of said seond link.

36. A system according to claim 35 in which adjacent ends of the measuring beams at said joint are slightly spaced apart but in close proximity to one another and in which the measuring means include sensors that note spatial relationship of one measuring beam with respect to the adjacent measuring beam.

37. A system according to claim 31 comprising several links and several joints with sensors at each joint to note said spatial relationship at each joint.

38. A system according to claim 37 having an end effector at the end point of the structural beam of the last link and a drive motor at each joint connected to effect angular motion of the structural beams at said each joint with respect to one another.

39. A system according to claim 37 in which the measuring means is adapted to measure said spatial relations to an accuracy of about one part in 50000.

40. A system according to claim 31 in which said connecting means comprises wires connecting one end of the structural beam to one end of the measuring beam and further wires connecting the other end of the structural beam to the other end of the measuring beam.

41. A system according to claim 40 wherein the connecting means provides six small degrees of freedom between the structural beam and the measuring beam.