Compliant four-bar linkage mechanism for a robotic finger
Inventors
Akhtar, Aadeel • Bretl, Timothy • Choi, Kyung Yun
Assignees
Publication Number
US-11185427-B2
Publication Date
2021-11-30
Expiration Date
2039-04-29
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Abstract
A system and method for a compliant four-bar linkage mechanism for a robotic finger that includes: a monolithic bone structure comprised of a compliant joint region and an input link segment and a coupler link segment, wherein the input link segment and the coupler link segment are connected through the compliant joint; an output link; a ground structure; wherein the monolithic bone structure, output link, and ground structure are connected through a set of joints in a configuration of a compliant four-bar linkage mechanism which comprises: the output link on a first end and the coupler link segment connected through an output joint, the output link on a second end connected to a ground joint on the ground structure, and the monolithic bone structure connected to an input joint connected to the ground structure; and an actuation input coupled to the input joint.
Core Innovation
The invention provides a system and method for a compliant four-bar linkage mechanism designed for use in a robotic or prosthetic finger. The mechanism features a monolithic bone structure consisting of an input link segment and a coupler link segment, which are joined by a compliant joint region made of a compliant material. This bone structure, together with an output link and a ground structure, connects through a series of joints to form a compliant four-bar linkage. The actuation input, coupled to the input joint, enables the mechanism to produce finger-like planar motion.
The problem addressed by the invention stems from the vulnerability and maintenance challenges of conventional prosthetic fingers. Existing designs often incorporate rigid components and pin joints, making them prone to breakage, especially under lateral impacts encountered in daily use. Repairing such broken fingers can be complex and costly. The invention seeks to overcome these limitations by introducing compliance into the mechanism, making it more resilient to incidental forces and reducing failure points associated with rigid pin joints.
In the preferred embodiment, the compliant four-bar linkage replaces the conventional rigid input and coupler links, as well as a standard pin joint, with an integrated, flexible monolithic bone. This compliant architecture is intended not only to maintain a range of motion suitable for simulating natural finger movement but also to enhance impact resistance. While the system is primarily described for prosthetic applications, its design can be adapted for other robotic and automated mechanisms requiring resilient actuation structures.
Claims Coverage
The patent includes three independent claims, each defining inventive features for compliant four-bar linkage mechanisms applied to prosthetic fingers and hands.
Compliant four-bar linkage mechanism for a prosthetic finger
- A monolithic bone structure comprising a compliant joint region and input and coupler link segments, with the joint region made of a compliant material and connecting the segments. - An output link and a ground structure, with these elements connected through joints configured as a compliant four-bar linkage: the output link and coupler link segment are connected via an output joint, the output link is connected at another end to a ground joint on the ground structure, and the monolithic bone is connected to an input joint on the ground structure. - An actuation input coupled to the input joint.
Compliant four-bar linkage for a prosthetic finger with a compliant proximal interphalangeal joint
- A monolithic bone structure comprising a compliant proximal interphalangeal joint connecting input and coupler link segments, with the joint made of a compliant material. - An output link and a prosthetic hand structure, with connections as a compliant four-bar linkage: the output link and coupler link segment are connected via an output joint, the output link is connected at another end to a ground joint on the prosthetic hand structure, and the monolithic bone structure is connected to a metacarpophalangeal input joint on the prosthetic hand structure. - An actuation input coupled to the compliant metacarpophalangeal input joint.
Prosthetic hand system with multiple compliant four-bar linkage finger mechanisms
- A base palm body integrating a set of worm gear actuation systems. - A set of compliant four-bar linkage mechanisms, each forming a prosthetic finger, where each mechanism includes: a monolithic bone structure comprising a compliant joint region and input and coupler link segments, with the joint region made of a compliant material; an output link. - In each finger mechanism, the output link and coupler link segment are connected through an output joint, the output link is connected at another end to a ground joint on the palm body, and the monolithic bone is connected to an input joint on the palm body. - Each worm gear actuation system mechanically couples to the input joint of each four-bar linkage mechanism.
The inventive features focus on a compliant four-bar linkage architecture for prosthetic fingers and hands, utilizing a monolithic bone with a compliant joint region, integration of actuation systems, and a configuration that enhances impact resistance and simplifies assembly.
Stated Advantages
Enhanced impact resistance compared to conventional rigid four-bar linkage mechanisms.
Reduction in failure points by eliminating a standard pin joint and using a compliant joint.
Lower energy loss due to decreased friction from link rotation, as one pin joint and associated friction are eliminated.
Easier fabrication, assembly, and maintenance due to fewer components and compatibility with 3D printing and molding techniques.
Reduced weight of the prosthetic finger and hand by replacing rigid components with a compliant monolithic bone structure.
Potential for producing smaller prosthetics, such as for women or children, due to part reduction and manufacturing flexibility.
Ability to recover from loads exceeding the mechanical load capacity, with compliant joints deforming elastically and returning to initial positions.
Improved conformity to various object shapes during grasping, as compliant fingers can adapt their positions.
Reduction in hysteresis, resulting in a more responsive prosthetic finger.
Decreased need for lubrication and maintenance of moving joints.
Documented Applications
Actuated fingers in prosthetic hands to simulate natural finger motion and enhance durability.
Prosthetic hand systems with multiple compliant, actuated fingers.
Robotics, automated mechanisms, or other applications requiring an actuating limb, lever, or mechanism with resilience to lateral forces.
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