Method and apparatus for tracking the position and orientation of a stylus and for digitizing a 3-D object

• US 6,134,506 A
• Filed: 10/29/1996
• Issued: 10/17/2000
• Est. Priority Date: 08/07/1995
• Status: Expired due to Term

• Current Assignee: Immersion Corporation
• Original Assignee: Microscribe, LLC
• Inventors: Schena, Bruce M., Rosenberg, Louis B., Jackson, Bernard G.
• Primary Examiner(s): Wachsman, Hal
• Application Number:
  US08/739,454
• Time in Patent Office: 1,449 Days
• Field of Search: 364/571.01, 364/71.02, 364/571.04, 364/571.05, 364/571.08, 364/190, 364/559-564, 364/167.01, 364/474.03, 364/474.28, 364/474.35 , 364/474.36, 364/474.37, 364/505, 364/506, 364/178, 364/551.02, 33/556, 33/558, 33/559, 33/561, 33/551, 33/502-505, 33/1 M, 33/1 N, 33/1 MP, 33/1 PT, 33/1 CC, 33/513, 33/514, 73/866.5, 73/862.041, 73/865.8, 73/1.37, 73/1.39, 73/1.41, 73/1.63, 73/1.73, 73/1.75, 73/1.78, 73/1.79, 73/1.81, 74/490.01, 74/490.05, 74/490.06, 74/490.07, 74/490.09, 901/41, 901/15, 901/3, 901/4, 901/27-29, 901/16, 395/82, 395/83, 395/86, 395/93, 395/90, 395/99, 345/161, 345/179, 345/162, 345/156-158, 178/18, 433/72, 433/75, 702/33, 702/87, 702/88, 702/94, 702/95, 702/97, 702/104, 702/105, 702/113, 702/116, 702/150-153, 702/155-158, 702/166-168
• US Class Current: 702/95
• CPC Class Codes: A63F 2300/1037 being specially adapted for converting control signals received from the game device into a haptic signal, e.g. using force feedback
• CPC Class Codes: B25J 9/1692 Calibration of manipulator
• CPC Class Codes: G01B 21/04 by measuring coordinates of points
• CPC Class Codes: G01B 21/042 Calibration or calibration artifacts G01B3/30, G01B9/02072 take precedence
• CPC Class Codes: G01B 5/008 using coordinate measuring machines
• CPC Class Codes: G05B 19/4207 in which a model is traced or scanned and corresponding data recorded
• CPC Class Codes: G05B 2219/37021 Robot controls position of touch probe
• CPC Class Codes: G05B 2219/37043 Touch probe, store position of touch point on surface
• CPC Class Codes: G05B 2219/39015 With different manipulator configurations, contact known sphere, ballbar
• CPC Class Codes: G05B 2219/39021 With probe, touch reference positions
• CPC Class Codes: G05B 2219/39024 Calibration of manipulator
• CPC Class Codes: G05B 2219/39048 Closed loop kinematic self calibration, grip part of robot with hand
• CPC Class Codes: G05B 2219/45055 Assembly
• CPC Class Codes: G05B 2219/45061 Measuring robot
• CPC Class Codes: G06F 2203/015 Force feedback applied to a joystick
• CPC Class Codes: G06F 3/016 Input arrangements with force or tactile feedback as computer generated output to the user
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device
• CPC Class Codes: H01H 2003/008 with a haptic or a tactile feedback controlled by electrical means, e.g. a motor or magnetofriction

Abstract

A method and apparatus for measuring three-dimensional (3-D) coordinates. A 3-D object can be digitized into a mesh representation manipulable by a computer system by tracing a stylus of a probe apparatus over surfaces of the object. The probe apparatus includes an arm having a series of linkages and joints. The arm can be assembled by placing the joints of the arm in joint fixtures a desired distance and angle apart and bonding the joints to a linkage. The probe apparatus is calibrated by placing the tip of the stylus at an arbitrary point in a work volume and varying the stylus'"'"' orientation to find error values and determine calibration parameters. The sensors of the probe apparatus are zeroed by placing the probe apparatus in the only possible home position and assigning assumed starting angles to the sensors. A rotary table can be used to support the object being digitized, where the rotation of the rotary table and object during digitization is sensed and included in coordinate calculations. A mesh representation of the object is-developed by a computer system by incrementally creating and displaying triangles from data points of contour lines of the mesh. A selection template allows commands to be selected by the stylus by defining a template having selection areas within the probe'"'"'s work volume and associating the selection areas with specific commands to the host computer.

Claims

1. A method for calibrating a probe apparatus which provides three-dimensional position and orientation data to a computer system, said probe apparatus including a probe coupled to a mechanical linkage assembly including a plurality of joints, said mechanical linkage assembly being supported by a support base, wherein said probe is moveable within a selected volume, and wherein sensors coupled to said mechanical linkage assembly are operative to sense joint angles related to a position and orientation of said probe and provide joint angle data to said computer system, the method comprising:

(a) positioning said probe such that a known point on said probe is located at an arbitrary location within said selected volume with respect to said support base;

(b) varying an orientation of said probe to move a plurality of joints of said mechanical linkage assembly while maintaining said known point on said probe at said arbitrary location;

(c) sampling sets of data at a plurality of orientations of said probe as said orientation of said probe is varied about said arbitrary location, said sets of data being provided by said sensors and describing different configurations of angles of said joints;

(d) determining a set of spatial coordinates for said known point on said probe at each of said plurality of orientations of said probe;

(e) determining a plurality of error, values each error value being between said set of said spatial coordinates determined for each of said plurality of said orientations of said probe and at least one other set of said spatial coordinates; and

(f) increasing the accuracy of position and orientation data provided by said probe apparatus by determining calibration parameters based on said error values, said calibration parameters being used when determining said position and orientation of said probe in normal usage.

2. A method as recited in claim 1 further comprising loading previous calibration parameters from a memory device.

3. A method as recited in claim 2 wherein said determining a set of spatial coordinates includes adjusting said previous calibration parameters based on said error values.

4. A method as recited in claim 3 wherein said previous calibration parameters are nominal calibration parameters with assumed ideal values when said probe apparatus is first being calibrated.

5. A method as recited in claim 4 wherein said adjusted calibration parameters are stored such that said adjusted calibration parameters may be later retrieved and used during operation of said probe apparatus.

6. A method as recited in claim 5 wherein said adjusted calibration parameters are stored on an EPROM memory device, said EPROM memory device being unable to store data over previously written data stored in said EPROM memory device.

7. A method as recited in claim 6 wherein said adjusted calibration parameters are stored as a most recent set of adjusted calibration parameters in a specific section of said EPROM memory device such that, when said adjusted calibration parameters are retrieved during operation of said probe apparatus, only said most recent set of adjusted calibration parameters are retrieved.

8. A method as recited in claim 7 wherein said EPROM memory device is positioned within said support base.

9. A method as recited in claim 1 further comprising repeating said positioning said probe, said varying an orientation, said sampling, said determining a set of spatial coordinates, and said determining a plurality of error values, said repeating performed when said probe is placed at a location in said selected volume different from said arbitrary location and using said plurality of sampled orientations from said arbitrary location and said different location when determining said error values.

10. A method as recited in claim 1 wherein said known point on said probe is a tip of said probe.

11. A method as recited in claim 1 therein said determining a set of spatial coordinates includes using kinematic equations in a mathematical representation of said probe, and wherein said error values represent inaccuracies in said mathematical representation.

12. A method as recited in claim 11 wherein said calibration parameters are to be used in calculation with said kinematic equations for said probe when determining said position and orientation of said probe in normal usage.

13. A method for zeroing sensors of a probe apparatus of a three-dimensional coordinate measuring system, said probe apparatus including a linkage arm assembly having a probe positioned at a first end, a support base positioned at a second end, and at least five rotary joints positioned between said probe and said support base, said at least five rotary joints being coupled to a plurality of sensors, each sensor operative to measure an angle differential resulting from movement of an associated rotary joint, the method comprising:

placing said probe in a receptacle positioned on said probe apparatus, said receptacle being positioned such that when said probe is positioned in said receptacle, four of said at least five rotary joints are substantially fixed in a known angular configuration and wherein a fifth of said at least five rotary joints may be positioned at any rotary position relative to a member coupled to said fifth rotary joint, said known angular configuration being a home position;

receiving an indication to zero said sensors of said probe apparatus, wherein said fifth rotary joint is positioned at a particular rotary position relative to said member coupled to said fifth rotary joint when said indication to zero said sensors is received; and

assigning a known angle to each of said at least five rotary joints when said probe is positioned in said receptacle, wherein said particular rotary position is considered a known angle for said fifth rotary joint.

14. A method as recited in claim 13 wherein said probe is a stylus.

15. A method as recited in claim 14 wherein said known angles have previously been calibrated for said probe apparatus.

16. A method as recited in claim 13 wherein said indication to zero said sensors includes receiving electrical power for said probe apparatus.

17. A method as recited in claim 13 wherein said receptacle comprises a divot positioned on a joint member rotatable coupled to a grounded joint member of said probe apparatus.

18. A method as recited in claim 13 wherein said fifth of said rotary joints is coupled to said support base and said fifth rotary joint may be positioned to any rotary position relative to said support base.

19. A method as recited in claim 13 wherein a local microprocessor performs said zeroing method such that values associated with said at least five rotary joints in said home position are set.

20. A method as recited in claim 19 wherein said local microprocessor includes setting predefined starting counts associated with said at least five rotary joints in said home position.

21. A method as recited in claim 20 wherein said predefined starting counts are communicated to a quadrature chip.

22. A method as recited in claim 13 wherein said linkage arm assembly includes six rotary joints.

23. A method for calibrating a three-dimensional probe apparatus having a probe moveable within a selected volume and a plurality of joints provided in a mechanical linkage coupled to said probe, the method comprising:

retrieving calibration parameters from a storage device;

sampling a plurality of orientations of said probe as said orientations of said probe are varied at an arbitrary location within said selected volume, wherein a position of a known point on said probe is maintained fixed at said arbitrary location while said orientation of said probe is varied to provide multiple configurations of angles of said joints of said probe apparatus, said sampled plurality of orientations of said probe being sampled from data provided by sensors that detect said joint angles and are coupled to said probe apparatus;

using said sampled plurality of orientations of said probe to determine a set of spatial coordinates of said known point on said probe at each of said sampled plurality of orientations;

comparing said set of determined spatial coordinates of said known point at each of said sampled plurality of orientations and determining differences between said set of determined spatial coordinates at each of said sampled plurality of orientations and at least one other set of said determined spatial coordinates; and

adjusting said calibration parameters based on said determined differences between said set of determined spatial coordinates at each of said sampled plurality of orientations and at least one other set of said determined spatial coordinates such that said adjusted calibration parameters are used when determining a position and orientation of said probe during operation of said probe apparatus.

24. A method as recited in claim 23 wherein said probe apparatus provides three-dimensional position and orientation data to a computer system, wherein said sensors are coupled to said mechanical linkage and are operative to sense said joint angles that are related to said position and orientation of said probe and send joint angle data to said computer system, and wherein said known point on said probe is a tip of said probe.

25. A method as recited in claim 23 wherein said calibration parameters are nominal calibration parameters with assumed ideal values when said probe apparatus is first being calibrated.

26. A method as recited in claim 25 wherein said adjusted calibration parameters are stored such that said adjusted calibration parameters may be later retrieved and used during operation of said probe apparatus.

27. A method as recited in claim 26 wherein said adjusted calibration parameters are stored on an EPROM memory device.

28. A method as recited in claim 23 further comprising repeating said sampling a plurality of orientations of said probe, using said sampled plurality of orientations of said probe to determine a set of spatial coordinates, and comparing said set of determined spatial coordinates, said repeating performed when the probe is placed at a location in said selected volume different from said arbitrary location and using said plurality of sampled orientations from said arbitrary location and said different location when determining said determined differences between said set of determined spatial coordinates at each of said sampled plurality of orientations and at least one other set of said determined spatial coordinates.

29. A method for zeroing sensors of a probe apparatus of a three dimensional coordinate measuring system, said probe apparatus including a linkage arm assembly having a probe positioned at a first end, a support base positioned at a second end, and N rotary joints positioned between said probe and said support base, wherein N is an integer, said N rotary joints being coupled to a plurality of sensors, each sensor operative to measure an angle differential resulting from movement of an associated rotary joint, the method comprising:

placing said probe in a receptacle positioned on said probe apparatus, said receptacle being positioned such that when said probe is within said receptacle, N-1 of said rotary joints are substantially fixed in a known angular configuration, and an Nth rotary joint is substantially free to be positioned at any rotary position relative to a member coupled to said Nth rotary joint; and

providing a known angle reference for said sensors when said N-1 rotary joints are in said known angular configuration when an indication to zero said sensors is received, wherein a particular rotary position of said Nth rotary joint relative to said member is considered a known angle for said Nth rotary joint, said Nth rotary joint being positioned at said particular rotary position when said indication to zero said sensors is received.

30. A method as recited in claim 29 wherein said member coupled to said Nth rotary joint is said support base, wherein said Nth rotary joint is substantially free to be positioned at any rotary position relative to said support base.

31. A method for zeroing sensors of a probe apparatus of a three dimensional coordinate measuring system, said probe apparatus including a linkage arm assembly having a probe positioned at a first end, a support base positioned at a second end, and a plurality of rotary joints positioned between said probe and said support base, said rotary joints being coupled to a plurality of relative sensors, each of said sensors operative to measure an angle differential resulting from movement of an associated rotary joint, the method comprising:

providing an index mark at a predetermined position in a sensing range of each of said relative sensors such that each of said index marks corresponds to a known angle of an associated rotary joint;

detecting said index mark for each of said sensors when a user grasps said probe and moves said probe within a workspace, said movement of said probe causing said rotary joints to rotate such that said index mark of each of said sensors is detected; and

assigning a predefined reference angle to each of said rotary joints associated with said detected index mark of each of said sensors, wherein said predefined reference angle of each of said rotary joints associated with said detected index mark of each of said sensors is a reference zero angle.

32. A method as recited in claim 31 wherein said probe is moved by said user from a first location in said workspace to a second location in said workspace, said movement causing said index mark of each of said sensors to be sensed by said associated sensor.

33. A method as recited in claim 32 wherein said first and second locations in said workspace are predetermined.

34. A method as recited in claim 31 wherein said movement of said probe in said workspace is a single, fluid motion to cause said index mark of each of said sensors to be detected.

35. A probe apparatus which provides three-dimensional position and orientation data to a computer system and determines calibration parameters, said probe apparatus comprising:

a mechanical linkage assembly, including;

a support base provided at a first end of said mechanical linkage assembly for supporting said mechanical linkage assembly;

a probe provided at a second end of said mechanical linkage assembly and moveable within a selected volume;

a plurality of joints provided between said probe and said support base; and

a plurality of sensors coupled to said mechanical linkage assembly operative to sense joint angles related to a position and orientation of said probe and provide joint angle data to said computer system;

means for determining a set of spatial coordinates for a known point on said probe at each of a plurality of sampled orientations of said probe when said probe is positioned at an arbitrary location within said selected volume and said orientation of said probe is varied while maintaining said known point on said probe at said arbitrary location;

means for determining error values, each of said error values being between said set of spatial coordinates determined for each of said plurality of said sampled orientations and at least one other set of said spatial coordinates; and

means for increasing the accuracy of position and orientation data provided by said probe apparatus by determining calibration parameters based on said error values, said calibration parameters being used when determining said position and orientation of said probe in normal usage.

36. A probe apparatus which provides three-dimensional position and orientation data to a computer system and zeroes transducers of the apparatus, the probe apparatus comprising:

a mechanical linkage assembly, including;

a support base provided at a first end of said mechanical linkage assembly for supporting said mechanical linkage assembly;

a probe provided at a second end of said mechanical linkage assembly and moveable within a selected volume;

N rotary joints positioned between said probe and said support base, wherein N is an integer; and

a plurality of sensors coupled to said mechanical linkage assembly, each sensor operative to measure an angle differential resulting from movement of an associated rotary joint;

a receptacle positioned on a joint member rotatably coupled to said support base of said probe apparatus such that when said probe is positioned in said receptacle, N-1 of said rotary joints are substantially fixed in a known angular configuration, and an Nth rotary joint is substantially free to be positioned at any angular position; and

a device that provides a known zero angle reference for said sensors when said N-1 rotary joints are in said known angular configuration.

37. A method for zeroing sensors of a probe apparatus of a three-dimensional coordinate measuring system, said probe apparatus including a linkage arm assembly having a probe positioned at a first end, a support base positioned at a second end, and at least five joints positioned between said probe and said support base, said at least five joints being coupled to a plurality of sensors, each sensor operative to measure an angle differential resulting from movement of an associated joint, the method comprising:

placing said probe in a receptacle positioned on said probe apparatus, said receptacle being positioned on a joint member rotatably coupled to a grounded joint member of said probe apparatus such that when said probe is positioned in said receptacle, four of said at least five joints are substantially fixed in a known angular configuration and wherein a fifth of said at least five joints may be positioned at any angular configuration, said known angular configuration being a home position;

receiving an indication to zero said sensors of said probe apparatus; and

assigning a known angle to each of said at least five joints when said probe is positioned in said receptacle.

38. A method as recited in claim 37 wherein said receptacle comprises a divot positioned on said joint member rotatably coupled to said grounded joint member.