US4874998A
Expired / Lapsed
US
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Magnetically levitated fine motion robot wrist with programmable compliance
Assignee: International Business Machines Corp
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Filing: 1988-06-21
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Granted: 1989-10-17
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Expires: 2008-06-21
Abstract
Abstract Selective compliance in up to six degress of freedom in a magnetically levitated fine motion device, or robot wrist, with limited motion in X,Y,Z, ROLL, PITCH, YAW, is provided by controlled actuation currents applied to six electrodynamic forcer elements. The wrist has a stator support base defining a dual periphery, carrying a number of stator magnet units. A shell flotor unit nests within the stator support base dual periphery, and carries forcer coils at locations corresponding to respective magnet units. The magnet unit and related flotor coil form a forcer element. There are a number of forcer elements. The vector sum of all the translational forces and rotational torques established at the forcer elements determines the X,Y,Z, ROLL, PITCH, and YAW motion of the flotor. The flotor carries an end effector which may be a tool. Position and orientation of the flotor is monitored by light emitting diodes and lateral effect cells. Coil currents are controlled as a composite of present position, desired final position, and desired compliance. As the fine motion device approaches its final position, the control unit changes forcer coil current patterns at various sets of forcer elements, to provide selected compliance in one or more degrees of freedom while approaching and finally while maintaining the desired position. Cooling is provided as needed; docking and locking provision is made to allow de-energizing the coils for cooling, motion of the base, or shutdown.
Inventors
- 👤 Ralph L. Hollis Jr
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 00:33
CPC Classifications
F; F16; F16C; F16C32/00; F16C32/04; F16C32/0406; F16C32/044; F16C32/0474; F16C32/0493; B; B23; B23Q; B23Q5/00; B23Q5/22; B23Q5/28; B25; B25J; B25J17/00; B25J17/02; B25J17/0208; B25J17/0283; B25J7/00; B25J9/00; B25J9/10; B25J9/12; F16C32/0444; H; H02; H02N; H02N15/00; F16C2322/00; F16C2322/39
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
227 words
A six-degree-of-freedom fine motion device, having but a single moving part, comprising: (a) a stator support unit (9) defining a base and a dual enclosure having dual walls upthrust from the base to define a dual periphery; (b) a multiplicity of forcer magnets (4) disposed at spaced positions about said dual periphery; (c) a flotor unit (1) having a related periphery nested in said dual periphery of said stator support unit (9); (d) forcer elements (5) including a multiplicity of forcer element flotor coils (3) arrayed about said periphery of said flotor unit (1) in active juxtaposition with said forcer magnets (4); (e) position and orientation sensing means (6) arrayed about said dual periphery of said stator support unit (9) and about said periphery of said flotor unit (1) to sense the relative positions and orientations of said stator support unit and said flotor unit; and (f) control means connected to said position and orientation sensing means (6) in feedback mode, for providing respective forcer elements (5) with electrodynamic actuation appropriate to maintain equilibrium at a desired starting position and orientation, appropriate to cause motion to a desired final position and orientation according to a force-to-displacement ratio K, and appropriate to provide a desired compliance in at least one degree of freedom by selectively lessening the force-to-displacement ratio K in a related set of forcer elements (5).
Claim 2
Dependent Claim
227 words
A six-degree-of-freedom fine motion device, having but a single moving part, comprising: (a) a stator support unit (9) defining a base and a dual enclosure having dual walls upthrust from the base to define a dual periphery; (b) a multiplicity of forcer magnets (4) disposed at spaced positions about said dual periphery; (c) a flotor unit (1) having a related periphery nested in said dual periphery of said stator support unit (9); (d) forcer elements (5) including a multiplicity of forcer element flotor coils (3) arrayed about said periphery of said flotor unit (1) in active juxtaposition with said forcer magnets (4); (e) position and orientation sensing means (6) arrayed about said dual periphery of said stator support unit (9) and about said periphery of said flotor unit (1) to sense the relative positions and orientations of said stator support unit and said flotor unit; and (f) control means connected to said position and orientation sensing means (6) in feedback mode, for providing respective forcer elements (5) with electrodynamic actuation appropriate to maintain equilibrium at a desired starting position and orientation, appropriate to cause motion to a desired final position and orientation according to a force-to-displacement ratio K, and appropriate to provide a desired compliance in at least one degree of freedom by selectively lessening the force-to-displacement ratio K in a related set of forcer elements (5).
Claim 3
Dependent Claim
51 words
A six-degree-of-freedom fine motion device according to claim 1, wherein said stator support unit (9) dual periphery and said flotor unit (1) periphery are in similar closed configuration, and said forcer elements (5) are six in number arrayed about said dual periphery and said flotor unit periphery of the closed configurations.
Claim 4
Dependent Claim
35 words
A six-degree-of-freedom fine motion device according to claim 2, wherein the closed configuration of said dual periphery of said stator support unit (9) and said periphery of said flotor unit (1) are hexagonal in section.
Claim 5
Dependent Claim
34 words
A six-degree-of-freedom fine motion device according to claim 2, wherein the closed configuration of said dual periphery of said stator support unit (9) and said periphery of said flotor unit (1) are substantially spherical.
Claim 6
Dependent Claim
69 words
A six-degree-of-freedom fine motion device according to claim 1, wherein said stator support unit (9) dual periphery and said flotor unit (1) periphery are hexagonal prisms in configuration; said forcer elements (5) are six in number, arrayed one to each rectangular surface of the hexagonal prism; and said control means provides control values related as a 6×6 square matrix T, with eigenvalues defining that the matrix T is non-singular.
Claim 7
Dependent Claim
73 words
A six-degree-of-freedom fine motion device according to claim 1, wherein said stator support unit (9) dual periphery and said flotor unit (1) periphery have reactive surfaces which generally follow the surface of a sphere, with the centroid of the sphere internal to and close to the axis of each of said stator support unit (9) and said flotor unit (1) and said forcer elements (5) being arrayed about the surface of the sphere.
Claim 8
Dependent Claim
107 words
A six-degrees-of-freedom fine motion device according to claim 1, wherein said forcer elements (5) include forcer magnets (4) on said stator support unit(9) and flotor coils (3) in said flotor unit (1), and said flotor coils (3) generally following the configuration of the periphery of said flotor unit (1) and the positions of respective forcer magnets (4); and sets of said forcer magnets (4) disposed substantially opposite each other on the dual periphery of said stator support unit (9) having substantial gaps in which gaps said flotor coils (3) can move during levitated fine motion of said flotor (1) with respect to said stator support unit (9).
Claim 9
Dependent Claim
116 words
A six-degrees-of-freedom fine motion device according to claim 1, wherein said forcer elements (5) include forcer magnets (4) on said stator support unit (9) and flotor coils (3) in said flotor unit (1), and said flotor coils (3) generally following the configuration of the periphery of said flotor unit (1) and the positions of respective forcer magnets (4), and said forcer elements further including passive damping means; and sets of said forcer magnets (4) disposed substantially opposite each other on the dual periphery of said stator support unit (9) have substantial gaps in which gaps flotor coils (3) can move during levitated fine motion of said flotor (1) with respect to said stator support unit (9).
Claim 10
Dependent Claim
82 words
A six-degrees-of-freedom fine motion device according to claim 1, wherein said forcer elements (5) include forcer magnets (4) on said stator support unit (9) and flotor coils (3) in said flotor (1), and said flotor coils (3) generally following the configuration of the periphery of said flotor (1) and the positions of respective forcer magnets (4), and said forcer magnets (4) being configured with sufficient magnetic gap to permit flotor coil movement within the gap sufficient for a desired range of motion.
Claim 11
Dependent Claim
18 words
A six-degrees-of-freedom fine motion device according to claim wherein said forcer elements are arrayed in two orthogonal groups.
Claim 12
Dependent Claim
22 words
A six-degrees-of-freedom fine motion device according to claim 1, wherein said stator support unit (9) and said flotor (1) include docking means.
Claim 13
Dependent Claim
22 words
A six-degrees-of-freedom fine motion device according to claim 11, wherein said docking means includes mechanical detenting means (18-19) and locking means (16-17).
Claim 14
Dependent Claim
19 words
A six-degrees-of-freedom fine motion device according to claim 1, wherein said stator support unit (9) includes heat transfer means.
Claim 15
Dependent Claim
24 words
A six-degrees-of-freedom fine motion device according to claim 1, wherein said stator support unit (9) undergoes motion and said flotor unit (1) remains fixed.
Claim 16
Dependent Claim
108 words
A motion and compliance emulation system comprising: a matched electrodynamically levitated flotor and stator combination, having clearance gaps between flotor and stator sufficient for a desired range of relative motion and greater than required for electrodynamic efficiency; electrodynamic forcer means for receiving coil currents for applying controlled magnetic forces mutual to the flotor and stator and analogous to a number of synthetic springs, each synthetic spring having a zero-point and a stiffness value; and programmable means for controlling both zero-point and stiffness value by controlling the coil currents in sets applied to said forcer elements during the entire range of mutual motion, thereby controlling position, orientation and compliance.
Claim 17
Dependent Claim
108 words
A motion and compliance emulation system comprising: a matched electrodynamically levitated flotor and stator combination, having clearance gaps between flotor and stator sufficient for a desired range of relative motion and greater than required for electrodynamic efficiency; electrodynamic forcer means for receiving coil currents for applying controlled magnetic forces mutual to the flotor and stator and analogous to a number of synthetic springs, each synthetic spring having a zero-point and a stiffness value; and programmable means for controlling both zero-point and stiffness value by controlling the coil currents in sets applied to said forcer elements during the entire range of mutual motion, thereby controlling position, orientation and compliance.
Claim 18
Dependent Claim
35 words
A motion and compliance emulation system according to claim 15, wherein said programmable means for controlling both zero-point and stiffness value includes software settable limit stops, of significant stiffness, near the limits of mechanical motion.
References Cited (Backward Citations)
US3184271A
Cited
US3061805A
Cited
US3948093A
Cited
US4078436A
Cited
US4156548A
Cited
US4244629A
Cited
US4316394A
Cited
US4402053A
Cited
US4645409A
Cited
US4602848A
Cited
US4536690A
Cited
US4611863A
Cited
US4597613A
Cited
US4509002A
Cited
US4514674A
Cited
US4595334A
Cited
US4686404A
Cited
US4700094A
Cited
US4694230A
Cited
US4739241A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-10-16 | 1993-04-17 | 1993-10-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-10-16 | 1997-04-17 | 1997-10-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-10-16 | 2001-04-17 | 2001-10-17 | $7700.00 | Window Closed / Lapsed |