Self-aligning mechanisms in passive and powered exoskeletons
An exoskeleton device that includes an artificial joint and a frame member extending from the artificial joint. The frame member is configured for extension over a limb of a user. The exoskeleton device also includes a self-aligning mechanism connected to the frame member. The self-aligning mechanism includes three passive degrees of freedom (pDOF) provided in a prismatic-revolute-revolute (PRR) configuration. The self-aligning mechanism also includes a limb attachment member configured for mechanically coupling to a portion of the limb of the user.
1. An exoskeleton device, comprising:
an artificial joint;
a frame member extending from the artificial joint and configured for placement over a limb of a user; and
a self-aligning mechanism connected to the frame member, the self-aligning mechanism comprising three passive degrees of freedom (pDOF) provided in a prismatic-revolute-revolute (PRR) configuration, the self-aligning mechanism further comprising
(i) a link connected to the frame member and being configured to extend along the limb of the user,
(ii) a linear guide slidably connected to the link, the linear guide forming a prismatic pDOF of the self-aligning mechanism,
(iii) a cuff attached to the linear guide via a rotary joint, the rotary joint enabling the cuff to rotate about a first rotational axis thereby forming a first revolute pDOF of the self-aligning mechanism, and
(iv) a limb attachment member configured for engaging with a first portion of the limb of the user, the limb attachment member being connected to the cuff via a rotary element, the rotary element enabling the limb attachment member to rotate about a second rotational axis that is substantially perpendicular to the first rotational axis thereby forming a second pDOF of the self-aligning mechanism,
wherein the artificial joint is connected to a slider-crank mechanism powered by a linear actuator, wherein the slider-crank mechanism comprises a four-bar mechanism, wherein the four-bar mechanism comprises a first slider-crank structure connected between the linear actuator and a first component of the artificial joint positioned on a first lateral side of a joint of the limb of the user and a second slider-crank structure positioned on a second lateral side of a joint of the limb of the user.
2. The exoskeleton device of claim 1 , wherein the frame member comprises a bridging element, the bridging element being connected to both the first component and the second component on opposing ends of the bridging element, and wherein the link extends from a central portion of the bridging element to extend along the limb of the user.
3. The exoskeleton device of claim 1 , wherein the link is configured to extend along an anterior side of the limb of the user.
4. The exoskeleton device of claim 1 , wherein the self-aligning mechanism weighs less than 200 g.
5. The exoskeleton device of claim 1 , wherein the self-aligning mechanism forms less than 6% of a total weight of the exoskeleton device.
6. The exoskeleton device of claim 1 , wherein the limb attachment member is configured for engaging with a shank of a leg of the user.
7. The exoskeleton device of claim 1 , wherein the linear actuator is configured for securement over a second portion of the limb of the user, the second portion being on an opposing longitudinal side of the joint of the limb relative to the first portion of the limb of the user.
8. The exoskeleton device of claim 7 , further comprising a shell connected to the linear actuator, the shell being configured to form about the second portion of the limb of the user.
9. The exoskeleton device of claim 8 , further comprising a strap connected to the shell and configured to secure the shell to the second portion of the limb of the user.
10. The exoskeleton device of claim 7 , wherein the linear actuator is configured for securement over the second portion of the limb in parasagittal alignment with the joint of the limb of the user.
11. The exoskeleton device of claim 7 , wherein the linear actuator is configured for securement over a thigh of a leg of the user.
12. The exoskeleton device of claim 1 , wherein the cuff and limb attachment member together encircle the first portion of the limb of the user.
13. The exoskeleton device of claim 1 , wherein the artificial joint is configured to align with a knee of the user.
14. A method for facilitating exoskeleton-assisted movement, comprising:
arranging an exoskeleton device on a user limb with an artificial joint of the exoskeleton device positioned about a joint of the user limb; and
compensating for misalignment between the artificial joint and the joint of the user limb with a self-aligning mechanism of the exoskeleton device, the self-aligning mechanism comprising three passive degrees of freedom (pDOF) provided in a prismatic-revolute-revolute (PRR) configuration, the self-aligning mechanism further comprising
(i) a link connected to a frame member of the exoskeleton device and being configured to extend along the limb of the user,
(ii) a linear guide slidably connected to the link, the linear guide forming a prismatic pDOF of the self-aligning mechanism,
(iii) a cuff attached to the linear guide via a rotary joint, the rotary joint enabling the cuff to rotate about a first rotational axis thereby forming a first revolute pDOF of the self-aligning mechanism, and
(iv) a limb attachment member configured for engaging with a first portion of the limb of the user, the limb attachment member being connected to the cuff via a rotary element, the rotary element enabling the limb attachment member to rotate about a second rotational axis that is substantially perpendicular to the first rotational axis thereby forming a second pDOF of the self-aligning mechanism,
wherein the compensation contributes to reduced spurious forces and/or torques exerted on the first portion of the user limb by the exoskeleton device,
wherein, for an assistive torque of about 50 Nm applied on the user limb by the exoskeleton device, a peak spurious force exerted on the first portion of the user limb by the exoskeleton device is below 10 N and/or a peak spurious torque exerted on the first portion of the user limb by the exoskeleton device is below 1 Nm.
15. The method of claim 14 , wherein the exoskeleton device is configured for placement on a user's leg to assist knee movement of the user.
16. An exoskeleton device, comprising:
an artificial joint comprising
a first component configured for positioning on a first lateral side of a joint of a limb of the user, and
a second component configured for positioning on a second lateral side of a joint of a limb of the user;
a frame member extending from the artificial joint and configured for placement over a limb of a user; and
a slider-crank mechanism powered by a linear actuator and configured to control movement of the artificial joint, the slider-crank mechanism comprising a four-bar mechanism that includes
a first slider-crank structure connected between the linear actuator and the first component of the artificial joint, and
a second slider-crank structure connected between the linear actuator and the second component of the artificial joint.
17. The exoskeleton device of claim 16 , wherein the frame member comprises a bridging element, the bridging element being connected to both the first component and the second component on opposing ends of the bridging element, and wherein the link extends from a central portion of the bridging element to extend along the limb of the user.
18. The exoskeleton device of claim 17 , further comprising a link extending from a central portion of the bridging element to extend along the limb of the user.
19. The exoskeleton device of claim 16 , wherein the exoskeleton device is configured for placement on a leg of the user to power movement of a knee of the user.