Exo-Glove Pinch: A Soft, Hand-Wearable Robot Designed Through Constrained Tendon Routing Analysis

Developing tendon-driven soft hand-wearable robots requires reducing the actuator counts to manage system complexity and functionality. Researchers have leveraged the tendons' inherent ability to apply position or force constraints to the joints, enabling the use of fewer actuators. Considering these constraints is important as they significantly affect the robot's motion characteristics such as adaptability and force capability. In this letter, we introduce the Exo-Glove Pinch, which utilizes two active tendons—a flexor and an extensor—to assist individuals with spinal cord injuries (SCI) in performing power grasps (enclosing objects with adaptable motion) and pinch grasps (applying sufficient contact force at the fingertip). By co-contracting the flexor and extensor, the system expands achievable joint torque manifolds, increasing maximum fingertip force by changing the direction of the contact force as verified through analysis and simulation. Preliminary testing with an individual with a spinal cord injury (SCI) suggests that the proposed robot is a promising solution for assisting in grasping variously shaped objects with adaptable power grasps and improving pinch grasp strength, generating fingertip forces 1.36 times greater than the previous actuation strategy.