Prosthetic hand and method of operating the same

Passive prosthetic forearm with spatial four-bar linkage mimicking ulnar-radial rotation

This technology is a passive prosthetic arm that uses a spatial four-bar linkage structure to replicate the natural cross-rotation mechanism between the human ulna and radius. It captures the rotational movement of the residual limb and transmits it from the first axis (coupling) to the second and third axes, using a gear set to amplify the rotation and physically extend the range of motion of the wrist.

Existing electric motor-based prosthetics suffer from heavy weight and poor replication of natural human movement. Furthermore, patients with partial forearm amputations often face limitations in pronation and supination due to the loss of the natural ulnar-radial cross-rotation.

This technology features a coupling unit that converts the movement of the residual limb into rotation around a first axis, a base link corresponding to the ulna, and a four-bar linkage fastening structure. By using a rotation amplification unit composed of four types of gears, the input rotation is amplified and transmitted to the wrist, enabling passive movement that closely mimics the forearm rotation of a healthy individual. It can be applied to prosthetics, rehabilitation aids, and wearable devices, extending the range of wrist pronation and supination without the need for motors, thereby reducing both weight and cost.

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Key Features:

• A fastening unit that provides a second axis linked to the rotation of the first axis on the upper side of the other surface, and a third axis spaced at a predetermined distance from the second axis on the lower side of the other surface.
• A coupling unit attached to one end of the residual limb that generates rotation around the first axis through the pronation or supination movement of the arm.
• A base link that extends from the elbow area to the wrist area of the residual limb and is positioned on one side of the ulna.
• A prosthetic arm where the angle formed by a first virtual line, defined by the cross-sections of the first and second axes, and a second virtual line, defined by the cross-sections of the second and third axes, changes during movement.

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This invention was developed with support from the Ministry of Science, ICT and Future Planning for the development of biomimetic bionic arm mechanisms.