Planar flexure members and actuators using them

{
  "publication_number": "US9556920B1",
  "country": "US",
  "kind": "B1",
  "title": "Planar flexure members and actuators using them",
  "abstract": "A planar flexure member for resisting rotation about a central axis thereof includes, in various embodiments, a central portion comprising a plurality of attachment points; and at least one serpentine flexure arm extending from the central portion in a plane. The arm(s) terminate in an arcuate mounting rail that includes a series of attachment points. The rails are positioned in opposition to to each other to partially define and occupy a planar circular envelope radially displaced from but surrounding the central portion of the flexure member. A portion of the serpentine arms may extend to (or substantially to) the envelope between the mounting rails.",
  "claims": [
    "1. A planar flexure member for resisting rotation about a central axis thereof, the flexure member comprising: a central portion comprising a plurality of attachment points; and at least two serpentine flexure arms extending oppositely and symmetrically from the central portion in a plane, each of the arms terminating in an arcuate mounting rail, the mounting rails each comprising a plurality of attachment points and being positioned in opposition to to each other to partially define and occupy a planar circular envelope radially displaced from but surrounding the central portion, a portion of the serpentine arms extending substantially to the envelope between the mounting rails.",
    "2. The flexure member of claim 1, wherein the serpentine arms have a varying thickness with a thinnest portion thereof at the envelope.",
    "3. The flexure member of claim 1, wherein the arms and the central portion have a unitary height, the height being at least equal to a width of the arms at a narrowest portion thereof.",
    "4. The flexure member of claim 3, wherein a ratio of the height to the width is at least 2.",
    "5. The flexure member of claim 1, wherein the arms and the central portion have a non-unitary height.",
    "6. The flexure member of claim 1, wherein the flexure member is made of titanium.",
    "7. The flexure member of claim 1, wherein at least a portion of the arms has an I-beam cross-section.",
    "8. The flexure member of claim 1, wherein at least a portion of the arms has voids along a neutral bending axis thereof.",
    "9. A rotary actuator comprising: a motor configured for rotation about an actuation axis; and a planar flexure member having a central output portion mechanically coupled to a load and at least two serpentine flexure arms extending oppositely and symmetrically from the central portion in a plane, each of the arms terminating in an arcuate mounting rail having a plurality of attachment points for mounting to the motor, the mounting rails being positioned in opposition to each other to partially define and occupy a planar circular envelope radially displaced from but surrounding the central portion, a portion of the serpentine arms extending substantially to the envelope between the mounting rails.",
    "10. The actuator of claim 9, wherein the serpentine arms have a varying thickness with a thinnest portion thereof at the envelope.",
    "11. The actuator of claim 9, wherein the arms and the central portion have a unitary height, the height being at least equal to a width of the arms at a narrowest portion thereof.",
    "12. The actuator of claim 9, wherein a ratio of the height to the width is at least 2.",
    "13. The actuator of claim 9, wherein the arms and the central portion have a non-unitary height.",
    "14. The actuator of claim 9, wherein the flexure member is made of titanium.",
    "15. The actuator of claim 9, wherein at least a portion of the arms has an I-beam cross-section.",
    "16. The actuator of claim 9, wherein at least a portion of the arms has voids along a neutral bending axis thereof.",
    "17. The actuator of claim 9, wherein the actuator has an actuation axis coaxial with an output axis."
  ],
  "description_excerpt": "The present invention relates to elastic flexure elements and actuators employing these elements for use, for example, in robotic applications.\n\nIndustrial robots perform a variety of tasks involving the movement and manipulation of various objects. A typical industrial robot as used, e.g., in a manufacturing environment, may have one or more arms equipped with grippers that allow the robot to pick up, transport, and manipulate objects. A key mechanical requirement for industrial is the ability to generate large but precise forces and torques while maintaining overall control stability. These torques and forces are generated by actuators, i.e., motors responsive to control signals to apply a commanded torque, which is transmitted mechanically to a load either directly (where rotational actuation is required) or via a linear conversion element, such as a lead screw (when linear force is required).\n\nStiff actuators can exert large forces from small joint displacements, and permit high-bandwidth force control and precise position control. But stiffness makes force control difficult. Because of the importance of force control in robotic applications, stiffness and the attendant bandwidth is typically sacrificed to achieve better force control. One approach is to utilize an elastic element in series with the actuator. Elasticity has the effect of making the force control easier, as larger deformations are needed to exert a given force relative to a stiff actuator. robot. In effect, the elasticity allows force to be controlled via position rather than directly, which improves accuracy and stability, and reduces noise.",
  "cpc": [
    "F16F 1/027",
    "B25J 17/0225",
    "B25J 19/0004",
    "B25J 9/0009",
    "F16D 3/005",
    "F16D 3/12",
    "F16D 3/62",
    "F16D 3/79"
  ],
  "ipc": [
    "F16D 3/12",
    "F16D 3/52",
    "F16D 3/79",
    "F16F 1/02"
  ],
  "assignees": [
    "Rethink Robotics Inc"
  ],
  "inventors": [
    "Matthew Knoll",
    "Jonathan Bond",
    "Robert White",
    "Umberto Scarfogliero",
    "Andrew Wallace"
  ],
  "filing_date": "2015-07-23",
  "publication_date": "2017-01-31",
  "grant_date": "2017-01-31",
  "priority_date": "2015-07-23",
  "application_number": "US-201514806807-A",
  "family_id": "56842595",
  "cited_by_count": 3,
  "citations": [
    "US2127688A",
    "US2947529A",
    "US4317339A",
    "US4480736A",
    "US5147246A",
    "US8876094B1",
    "US9183975B2",
    "US20160102724A1"
  ]
}