A Novel Clinical-Driven Design for Robotic Hand Rehabilitation: Combining Sensory Training, Effortless Setup, and Large Range of Motion in a Palmar Device

Abstract

Neurorehabilitation research suggests that not only high training intensity, but also somatosensory information plays a fundamental role in the recovery of stroke patients. Yet, there is currently a lack of easy-to-use robotic solutions for sensorimotor hand rehabilitation. We addressed this shortcoming by developing a novel clinical-driven robotic hand rehabilitation device, which is capable of fine haptic rendering, and that supports physiological full flexion/extension of the fingers while offering an effortless setup. Our palmar design, based on a parallelogram coupled to a principal revolute joint, introduces the following novelties: (1) While allowing for an effortless installation of the user's hand, it offers large range of motion of the fingers (full extension to 180° flexion). (2) The kinematic design ensures that all fingers are supported through the full range of motion and that the little finger does not lose contact with the finger support in extension. (3) We took into consideration that a handle is usually comfortably grasped such that its longitudinal axis runs obliquely from the metacarpophalangeal joint of the index finger to the base of the hypothenar eminence. (4) The fingertip path was optimized to guarantee physiologically correct finger movements for a large variety of hand sizes. Moreover, the device possesses a high mechanical transparency, which was achieved using a backdrivable cable transmission. The transparency was further improved with the implementation of friction and gravity compensation. In a test with six healthy participants, the root mean square of the human-robot interaction force was found to remain as low as 1.37 N in a dynamic task. With its clinical-driven design and easy-to-use setup, our robotic device for hand sensorimotor rehabilitation has the potential for high clinical acceptance, applicability and effectiveness.

Design of a Haptic Palmar Device with Thumb Flexion and Circumduction Movements for Sensorimotor Stroke Rehabilitation

“…We recently developed a novel clinical-driven robotic hand rehabilitation device (PRIDE), which is capable of fine haptic rendering and that supports physiological full flexion/extension of the fingers while offering an effortless setup [4]. To develop a compatible thumb module that preserves the kinematic, haptic, and ergonomic characteristics of our palmar device, a few key points had to be considered.…”

“…2 ) such that the end-effector tracks the thumb fingertips movements of the four hand sizes as closely as possible. The thumb movements were computed based on a three DoF serial kinematic chain model with constant inter-joint couplings, as presented in [4]. The optimization was performed by first discretizing the thumb and end-effector paths for the four sizes in five equally spaced points each.…”

“…We therefore recognized the need for a highly backdrivable actuation that would not hamper any self-initiated movements. Hence, we aimed for a capstan drive, similar to the actuation of the fingers [4].…”

“…Although many hand rehabilitation devices have been developed up to date (see [4] for a review), they are not delivering the anticipated treatment outcomes [5], probably because the majority of current hand rehabilitation robots does not support patients to regain the functional movements needed to perform Activities of Daily Living (ADL). Furthermore, one of the main obstacles listed for the poor clinical acceptance of these sophisticated devices is their high complexity [6].…”

“…We recently designed a novel clinical-driven haptic device that allows to train collective finger movements of the index to little finger. Our solution combines an effortless setup, sensory training, and a large range of motion in a palmar device [4]. The sensorimotor training is achieved through high-quality haptic rendering, which allows patients to not only rely on visual feedback -e.g., from a computer screen -but to also integrate somatic feedback (tactile, proprioceptive) during training [8], [9].…”