Session: 07-10-02: Medical Robotics, Rehabilitation, and Surgery II

Paper Number: 167159

New Affordable Three-Dof Wrist Exoskeleton With High Torque and Wide Range of Motion 

This work aims to enhance rehabilitative medical exoskeleton technology for the upper extremities of the human body by developing an affordable wrist exoskeleton (radiocarpal joint). Breakthroughs in medical exoskeleton technology have enabled individuals who have suffered debilitating injuries or were born with certain neurological conditions to regain motor function in their upper or lower limbs. However, exoskeletons focusing primarily on the radiocarpal joint are limited in the current market and provide a restricted range of motion, offering only two degrees of freedom: flexion and extension, and radial and ulnar deviation. Therefore, the primary goal is to replicate all three degrees of freedom of a human wrist: flexion and extension, radial and ulnar deviation, and pronation and supination. This innovative design aims to integrate pronation and supination along with the previously mentioned two degrees of freedom. The challenge in producing the motions of pronation and supination stems from the fact that the two bones comprising the human forearm, the radius and the ulna, cross over each other, making it a domain that researchers have yet to explore mechanically and safely. Successfully integrating and replicating all three degrees of freedom is crucial for effective rehabilitative wrist therapy. The exoskeleton’s design embodies a novel stationary robotic device. Its mechanistic stability, practicality, functionality, and user safety are the key focus areas. The mechanism has a desired range of motion of 15 degrees for both radial and ulnar deviation, 75 degrees for both flexion and extension and 105 degrees for axial rotation.

Furthermore, incorporating C++ programming ensures that all components, including the motors and circuits, operate in sync. At the core of the computer program lies a Fourier series, which allows for controlled sinusoidal motion of the motor's oscillation while maintaining precise and coordinated movement. User safety is paramount; calculating and inputting appropriate constants into the derived Fourier series establishes optimal motion parameters that minimize risk and maintain efficiency. For fabrication, utilizing Fused Deposition Modeled (FDM) PETG-CF components substantially reduced production costs, along with constructing around an affordable ESP-32 microcontroller. Three CubeMars AK80-9 direct current (DC) brushless motors are utilized, one positioned at each of the three degrees of freedom. Designing each motor to directly actuate each degree of freedom ensures that the desired range of motion is achieved for specific user applications, such as rehabilitation activities. The combination of cost-effective components and an optimized design process will make the mechanism affordable and accessible to a broader range of users. This device can set the groundwork for future developments in the rehabilitation of upper extremities using advanced assistive robotics.

Presenting Author: Sanad A. Shabbar San Jose State University

Presenting Author Biography: Sanad A. Shabbar is a senior at San Jose State University pursuing a degree in Mechanical Engineering. Originally from Santa Barbara, California, he has a strong passion for mechanical design, robotics, and mechatronics. His projects focus on advancing rehabilitative medical exoskeleton technology by developing exoskeletons that replicates all the degrees of freedom of human motion. By integrating innovative mechanical design, C++ programming, and cost-effective components, his work aims to enhance accessibility and effectiveness in upper and lower limb rehabilitation. Sanad is dedicated to contributing to the field of assistive robotics and pushing the boundaries of medical exoskeleton development.

Authors:

Michael Iwamiya San Jose State University
Mojtaba Sharifi San Jose State University
Ron Raymundo San Jose State University
Alec Karaguezian San Jose State University
Merlin Perez Lopez San Jose State University
Will Valencia San Jose State University
Sanad A. Shabbar San Jose State University