Compact Series Visco-Elastic Joint (SVEJ) for Smooth Torque Control.

The design and control of a new series-viscous-elastic joint are presented. The proposed joint consists of 3D printed parts compressing nonlinear elastic silicone springs. The use of silicone springs is the main novelty of the system; they exhibit internal damping, which enhances system performance allowing a simpler and more stable control. Their stiffness allows the system to bear a torque of about 4.5 Nm at a deformation angle of about 20 degrees. In this article, the system is modeled using the Neo-Hookean material model and then characterized through experiments to build the joint torque estimator. A proportional torque controller is implemented to evaluate bandwidth, transparency, impedance rendering, and stability, obtaining satisfactory results. The bandwidth ranges from 6.9 to 9.9 Hz depending on chirp input torque amplitude, as the system is nonlinear. The proposed solution is compact and cheap; both the design and the torque controller are suitable for future integration in an exoskeleton, or a cooperative robot, or a haptic device. SVEJ works as a torque sensor and introduces compliance between the motor and the environment, enhancing safety for robotic devices interacting with humans.

An Assistive Soft Wrist Exosuit for Flexion Movements With an Ergonomic Reinforced Glove.

Soft exosuits are a promising solution for the assistance and augmentation of human motor abilities in the industrial field, where the use of more symbiotic wearable robots can avoid excessive worker fatigue and improve the quality of the work. One of the challenges in the design of soft exosuits is the choice of the right amount of softness to balance load transfer, ergonomics, and weight. This article presents a cable-driven based soft wrist exosuit for flexion assistance with the use of an ergonomic reinforced glove. The flexible and highly compliant three-dimensional (3D)-printed plastic structure that is sewn on the glove allows an optimal force transfer from the remotely located motor to the wrist articulation and to preserve a high level of comfort for the user during assistance. The device is shown to reduce fatigue and the muscular effort required for holding and lifting loads in healthy subjects for weights up to 3 kg.

On the edge between soft and rigid: an assistive shoulder exoskeleton with hyper-redundant kinematics.

In this paper, we present a prototype of an innovative portable shoulder exoskeleton for human assistance and augmentation. The device provides torques to flexion/extension movements of the shoulder, compensating for gravitational forces, and is passively compliant along the remaining degrees of freedom letting the shoulder moving along them. The novelty of our system is a flexible link, made of a hyper-redundant passive structure, that avoids joint misalignment by adapting to the complex movements of the humerus head, similarly to a soft component. The flexible link is compliant to rotations around one axis but rigid around the other two axes, allowing transmission of flexion/extension torque but kinematically transparent along the remaining degrees of freedom. The device is light weight and allows to cover around the 82% of the shoulder flexion/extension range of motion. The exoskeleton was tested on a cohort of 5 healthy subjects, monitoring shoulder kinematics, interaction forces and acquiring the electromyography of three major muscles contributing to shoulder flexion. During both static postures and dynamic movements, assistance from the exoskeleton resulted in a significant reduction of muscular effort in the anterior (-32.2% in static, -25.3% in dynamic) and medial deltoid (56.9% in static, -49.6% in dynamic) and an average reduction of the biceps brachii.