Design and Simulation of a Differential Mechanism for a Robotic Hand Prosthesis with Independent Control and Optimal Force Distribution among Fingers and Thumb

In recent years, the development of robotic hand prosthesis systems aimed at restoring motor functions and improving the quality of life for individuals with limb loss has emerged as a leading field in biomedical engineering. In the present study, a novel robotic hand prosthesis mechanism utilizing a differential force distribution system and a solenoid-based locking mechanism was designed and simulated to achieve more precise and natural control over finger and wrist movements. To reduce weight and enhance efficiency, an under-actuated mechanism was employed in the finger design, and the geometric dimensions were extracted based on the anatomical structure of a human hand. For the thumb, two separate actuators were incorporated at the CMC joint to facilitate both flexion and rotational movements, thereby improving opposability and object grasping capability. The solenoid’s magnetic field and optimal activation current were simulated using COMSOL Multiphysics. Furthermore, dynamic simulations were conducted to analyze hand movements including fist formation, pointing (extension of the index finger while the other fingers remain flexed), flexion of the ring and little fingers, thumb flexion, and wrist rotation. The results demonstrated that the proposed differential mechanism effectively distributes forces uniformly among the fingers, while the solenoid-based locking system allows the user to selectively activate desired fingers. The measured ranges of motion (ROM) for the MCP, PIP, and DIP joints were ۷۸°, ۹۵°, and ۶۰°, respectively, and for the thumb joints were ۹۰°, ۳۸°, and ۳۰°, showing good conformity with natural human hand movements. Overall, the proposed design—with reduced number of actuators, lower weight, intelligent force distribution, and independent finger control—represents a significant advancement toward next-generation prosthetic hands with performance closely resembling that of a natural human hand.

کلیدواژه ها:

Robotic hand prosthesis ، Differential mechanism ، Artificial neural network ، COMSOL