Variable-stiffness mechanism based on compliant beams

A variable-stiffness mechanism comprising:

• a first unit, wherein the first unit defines a plurality of slotted arcs;
• a second unit, wherein the second unit is configured to rotate relative to the first unit;
• and
• a plurality of crank-slider subassemblies, wherein the second unit is disposed radially inwards of and axially aligned with the plurality of crank-slider subassemblies, wherein the plurality of crank-slider subassemblies comprise:
• a compliant member, wherein the compliant member abuts the second unit;
• an input crank, wherein the input crank is coupled to the first unit by a revolute joint;
• a pair of connecting rods;
• a pair of rod-to-member revolute joints, wherein the compliant member is coupled to the pair of connecting rods by the pair of rod-to-member revolute joints;
• and
• a pair of crank-to-rod revolute joints, wherein the pair of connecting rods are coupled to the input crank by the pair of crank-to-rod revolute joints, wherein the pair of crank-to-rod revolute joints are configured to follow within the plurality of slotted arcs, wherein a circumferential center of the compliant member to which the second unit abuts is configured to flex radially inwards and outwards as the pair of crank-to-rod revolute joints follow within the plurality of slotted arcs, wherein a stiffness of the variable-stiffness mechanism is varied based on flexure of the compliant member.

A variable-stiffness mechanism comprising:

• a first unit;
• a second unit, wherein the second unit is configured to rotate relative to the first unit, wherein the second unit is annular;
• a planetary gearset, wherein the planetary gearset is disposed radially inwards of and axially aligned with the second unit, wherein the planetary gearset comprises:
• a sun gear, wherein the sun gear is configured to rotate relative to the first unit;
• a plurality of planet gears, wherein the plurality of planet gears are coupled to the first unit by a plurality of unit-to-planet revolute joints, wherein the sun gear engages with the plurality of planet gears;
• a plurality of ring-gear segments, wherein the plurality of planet gears engage with respective of the plurality of ring-gear segments;
• and
• a plurality of compliant members, wherein the plurality of compliant members are coupled to and revolve with respective of the plurality of ring-gear segments about the sun gear, wherein the plurality of compliant members comprise:
• an arc-segment portion, wherein the arc-segment portion couples to the plurality of ring-gear segments;
• and
• a contact portion, wherein the contact portion extends radially from the arc-segment portion and abuts the second unit;
• and
• a plurality of pivot pins fixed to the first unit, wherein the plurality of pivot pins and the plurality of ring-gear segments are radially aligned, wherein the arc-segment portion of the plurality of compliant members abut and pivot about the plurality of pivot pins, wherein a stiffness of the variable-stiffness mechanism is varied based on a circumferential position at which the plurality of pivot pins abut the arc-segment portion of the plurality of compliant members.