PLEXUS Hand: Lightweight Four-Motor Prosthetic Hand Enabling Precision-Lateral Dexterous Manipulation.

Area of Science:

• Robotics
• Biomedical Engineering
• Prosthetics

Background:

• Electric prosthetic hands require lightweight designs, cosmetic human-like shapes, and protected internal motors for user acceptance and durability.
• In-hand manipulation, involving rotational movements for tasks like reorienting objects or using tools, is crucial for daily activities but is limited in current prosthetic hands.
• Existing prosthetic hands often lack in-hand manipulation or use complex, heavy mechanisms, compromising functionality and user comfort.

Purpose of the Study:

• To develop a lightweight electric prosthetic hand capable of in-hand manipulation using a minimal number of motors.
• To enable essential daily tasks and tool operation through advanced grasping and reorientation capabilities.
• To overcome the weight and complexity limitations of current prosthetic hand designs.

Main Methods:

• Integration of a single-axis thumb with optimized thumb positioning within a prosthetic hand.
• Utilizing only four motors to achieve both basic posture and in-hand manipulation, specifically reorientation between precision and lateral grasps.
• Experimental validation with primitive objects of varying widths (5-30 mm) and shapes (cylinders, prisms) to assess reorientation success rates.

Main Results:

• The developed prosthetic hand weighs 311 g and successfully performs in-hand manipulation tasks.
• Reorientation tasks achieved success rates of 90-100% with various objects.
• Demonstrated capabilities include seal stamping, USB device insertion, and screwdriver operation through rotational movements.

Conclusions:

• A novel electric prosthetic hand design successfully integrates in-hand manipulation with a lightweight, human-like form factor.
• The use of a single-axis thumb and optimized positioning with four motors provides a viable solution for advanced prosthetic functionality.
• This approach enhances the potential for everyday use of prosthetic hands by enabling complex daily activities and tool interactions.