Variable stiffness series elastic actuator

A robotic manipulator, comprising:

• a variable stiffness actuator comprising:
• a first flexure plate rotatable about a first common joint axis, the first flexure plate comprising an outer ring that defines an outer periphery of the flexure plate, the outer ring coaxial about the first common joint axis and a first cantilevered beam extending inwards from the outer ring towards the first common joint axis;
• a first housing rotatable about the first common joint axis;
• and
• a first contactor pivotably secured at a first revolute joint to the first housing, the first contactor rotates about the first revolute joint at a first rotation axis, the first rotation axis offset on the first housing from the first common joint axis, wherein the first contactor engages the first cantilevered beam at a variable angle about the first rotation axis to adjust a stiffness of a mechanical connection between the first flexure plate and the first housing;
• an input link operably connected to the first flexure plate;
• an output link secured to the first housing;
• a motor secured to the input link;
• and
• a hollow shaft rotatable by the motor, the hollow shaft secured to the outer ring of the first flexure plate.

A method of controlling stiffness in an actuator joint, the method comprising:

• providing an actuator joint comprising:
• a flexure plate comprising an outer ring that defines an outer periphery of the flexure plate, the outer ring coaxial about a common joint axis, a first cantilevered beam extending inwards from the outer ring towards the common joint axis;
• a housing, the housing and the flexure plate rotatable about a common joint axis;
• and
• a first contactor pivotably secured at a revolute joint to the housing, the first contactor rotates about the revolute joint at a first rotation axis, the first rotation axis offset on the housing from the common joint axis;
• adjusting an engagement between the first contactor and the first cantilevered beam by adjusting a continuously variable angle of the first contactor about the first rotation axis;
• engaging the first cantilevered beam with the first contactor at a first angle of the first contactor to provide a first stiffness mechanical connection between the flexure plate and the housing;
• and
• engaging the first cantilevered beam with the first contactor at a second angle of the first contactor to provide a second stiffness mechanical connection between the flexure plate and the housing;
• providing an input torque on the flexure plate through a hollow shaft secured to the outer ring of the flexure plate;
• and
• transferring at least a portion of the input torque through the flexure plate to the housing through engagement between the first cantilevered beam and the first contactor.

A variable stiffness actuator, comprising:

• a flexure plate comprising a first cantilevered beam extending inwards from an outer periphery of the flexure plate;
• a housing, the housing and the flexure plate rotatable about a common joint axis;
• and
• a first contactor pivotably secured at a first revolute joint to the housing, the first contactor rotates about the revolute joint at a first rotation axis, the first rotation axis offset on the housing from the joint axis, wherein the first contactor engages the first cantilevered beam at a variable angle about the first rotation axis to adjust a stiffness of a mechanical connection between the flexure plate and the housing;
• a second cantilevered beam extending inwards from the outer periphery of the flexure plate;
• a second contactor pivotably secured at second revolute joint to the housing, the second contactor rotates about the second revolute joint at a second rotation axis, the second rotation axis offset on the housing from the joint axis;
• a third cantilevered beam extending inwards from the outer periphery of the flexure plate;
• a third contactor pivotably secured at third revolute joint to the housing, the third contactor rotates about the third revolute joint at a third rotation axis, the third rotation axis offset on the housing from the joint axis;
• a fourth cantilevered beam extending inwards from the outer periphery of the flexure plate;
• and
• a fourth contactor pivotably secured at fourth revolute joint to the housing, the fourth contactor rotates about the fourth revolute joint at a fourth rotation axis, the fourth rotation axis offset on the housing from the joint axis.

A method of controlling stiffness in an actuator joint, the method comprising:

• providing an actuator joint comprising:
• a flexure plate comprising:
• a first cantilevered beam extending inwards from an outer periphery of the flexure plate, a second cantilevered beam extending inwards from the outer periphery of the flexure plate, a third cantilevered beam extending inwards from the outer periphery of the flexure plate, and a fourth cantilevered beam extending inwards from the outer periphery of the flexure plate;
• a housing, the housing and the flexure plate rotatable about a common joint axis;
• a first contactor pivotably secured at a revolute joint to the housing, the first contactor rotates about the revolute joint at a first rotation axis, the first rotation axis offset on the housing from the common joint axis;
• a second contactor pivotably secured at second revolute joint to the housing, the second contactor rotates about the second revolute joint at a second rotation axis, the second rotation axis offset on the housing from the joint axis;
• a third contactor pivotably secured at third revolute joint to the housing, the third contactor rotates about the third revolute joint at a third rotation axis, the third rotation axis offset on the housing from the joint axis;
• and
• a fourth contactor pivotably secured at fourth revolute joint to the housing, the fourth contactor rotates about the fourth revolute joint at a fourth rotation axis, the fourth rotation axis offset on the housing from the joint axis;
• adjusting an engagement between the first contactor and the first cantilevered beam by adjusting a continuously variable angle of the first contactor about the first rotation axis;
• engaging the first cantilevered beam with the first contactor at a first angle of the first contactor to provide a first stiffness mechanical connection between the flexure plate and the housing;
• and
• engaging the first cantilevered beam with the first contactor at a second angle of the first contactor to provide a second stiffness mechanical connection between the flexure plate and the housing;
• and
• simultaneously driving the first, second, third, and fourth to matching angles about the respective first, second, third, and fourth rotation axes.