Planar flexure members and actuators using them
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 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.
1. A system for transmission of torque from a motor to a load, the system having an output axis and comprising:
a motor configured for rotation about an actuation axis; and
a planar flexure member having:
a central portion having a plurality of first 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 having a plurality of second attachment points, 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 each of the serpentine arms extending substantially to the envelope between the mounting rails,
wherein the planar flexure member receives torque from the motor along the actuation axis and causes transmission of torque to the output axis.
2. The system of claim 1 , wherein the actuation axis of the motor is coaxial with the output axis.
3. The system of claim 1 , wherein the actuation axis of the motor is parallel to and offset with respect to the output axis.
4. The system of claim 1 , wherein the actuation axis of the motor is oblique with respect to the output axis.
5. The system of claim 1 , wherein the serpentine arms have a varying thickness with a thinnest portion thereof at the envelope.
6. The system 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.
7. The system of claim 6 , wherein a ratio of the height to the width is at least 2.
8. The system of claim 1 , wherein the arms and the central portion have a non-unitary height.
9. The system of claim 1 , wherein the flexure member comprises titanium.
10. The system of claim 1 , wherein at least a portion of each of the arms has an I-beam cross-section.
11. The system of claim 1 , wherein at least a portion of each of the arms has voids along a neutral bending axis thereof.
12. The system of claim 1 , wherein the arcuate mounting rails are mechanically coupled to the motor via the plurality of second attachment points, whereby the load mechanically couples to the central portion via the plurality of first attachment points.
13. The system of claim 1 , wherein the central portion is mechanically coupled to the motor via the plurality of first attachment points, whereby the load mechanically couples to the arcuate mounting rails via the plurality of second attachment points.
14. The system of claim 1 , further comprising a gearbox for translating torque between the motor and the flexure member, an output of the gearbox being mechanically coupled to the flexure member via the plurality of first attachment points or the plurality of second attachment points.
15. The system of claim 14 , wherein the gearbox is integral with the motor.
16. The system of claim 14 , wherein the gearbox is separate from the motor.
17. The system of claim 14 , wherein the output of the gearbox comprises aluminum.
18. The system of claim 1 , wherein the motor and the flexure member are disposed within a robotic appendage.
19. The system of claim 1 , further comprising a load mechanically coupled to the flexure member via the plurality of first attachment points or the plurality of second attachment points, wherein at least a portion of the load in contact with the flexure member comprises aluminum.
20. A method of transmitting torque to a load, the method comprising:
mechanically coupling a motor to a planar flexure member, the motor being configured for rotation about an actuation axis, wherein the planar flexure member comprises:
a central portion having a plurality of first 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 having a plurality of second attachment points, 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 each of the serpentine arms extending substantially to the envelope between the mounting rails;
mechanically coupling a load to the planar flexure member; and
receiving, with the planar flexure member, torque from the motor along the actuation axis, thereby causing transmission of torque to an output axis of the load.