Five-fingered Hand with Wide Range of Thumb Using Combination of Machined Springs and Variable Stiffness Joints

Development and Evaluation of a Five-Fingered Robotic Hand with Enhanced Thumb Mobility and Variable Stiffness Joints

Introduction to the Robotic Hand Design

The development of robotic hands that mimic the dexterity and power of human hands remains a significant challenge in robotics. This paper discusses the design, fabrication, and evaluation of a five-fingered robotic hand equipped with a thumb that has an extensive range of motion and fingers that feature a variable rigidity mechanism. The innovative use of machined springs in combination with a variable stiffness mechanism enables the robotic hand to grasp a diverse array of objects and exert substantial gripping force.

Human Hand Structure and Robotic Application

The human hand's ability to grasp and manipulate objects of various shapes and sizes is facilitated by a complex arrangement of joints, muscles, and ligaments. The paper successfully translates these features into the robotic domain by focusing on two critical areas:

• Thumb CM Joint: The thumb's carpometacarpal (CM) joint, characterized by its wide range of motion, is recreated using a combination of three machined springs. This design allows for significant mobility in thumb movements, essential for performing opposition and gripping functions.
• MP Joints of Four Fingers: The metacarpophalangeal (MP) joints of the fingers are implemented with variable rigidity mechanisms. This novel approach allows the robotic hand to adjust joint stiffness dynamically, enabling it to manipulate objects more dexterously.

Design and Fabrication

The fabrication of the robotic hand introduces several key innovations:

• Finger Joint Design: Machined springs are used to create robust and flexible finger joints. This design approach provides adequate strength and flexibility, enabling the hand to support heavy loads and absorb impacts effectively.
• Thumb CM Joint Complexity: The intricate design of the thumb CM joint, involving three machined springs, enables a wide range of motion. This mechanic is critical for achieving the thumb's complex movements.
• Variable Rigidity Mechanism: A tendon-driven mechanism is employed in the MP joints of the fingers to adjust their stiffness variably. This feature is fundamental for increasing the hand's versatility in handling different objects.

Experimental Evaluation

The evaluation of the robotic hand involved several key experiments:

• Object Grasping: The hand demonstrated the ability to grasp various objects by adjusting the stiffness of its finger joints and employing the wide range of motion of the thumb CM joint.
• Load Support: The robotic hand showed substantial strength by supporting loads up to 400N, indicating its potential for practical applications requiring power.
• Functional Movements: Experiments involving the switching of a lever in a vehicle and wiping a table showcased the hand's functional diversity. These movements highlighted the effectiveness of the variable rigidity mechanism and the enhanced thumb mobility.

Conclusion and Future Work

The paper concludes with a positive assessment of the robotic hand's capability to mimic human hand functions closely. The combination of machined springs and variable stiffness mechanisms has proven effective in reproducing both the dexterity and the power of the human hand. Future work will focus on refining the hand's skill-level through advanced control of force sensors, optimizing joint designs, and developing more compact and powerful actuators. The research opens promising avenues for creating more sophisticated robotic hands capable of performing a wide variety of tasks with human-like proficiency.

References

A well-cited section includes references to existing robotic hands, design mechanisms, and material properties relevant to the development of the robotic hand presented in this paper. These citations play a crucial role in situating the work within the broader context of robotic hand research and development.

Implications for AI and Robotics

The advancements in robotic hand design discussed in this paper have broad implications for AI and robotics. Enhanced dexterity and strength in robotic hands can significantly improve the capabilities of robots in industrial, medical, and consumer applications. Furthermore, integrating AI with these sophisticated mechanical designs could lead to autonomous robots capable of performing complex tasks with minimal human intervention. As technology progresses, the convergence of AI and advanced robotic designs will undoubtedly lead to innovations with far-reaching impacts.