Preliminary design and control of a soft exosuit for assisting elbow movements and hand grasping in activities of daily living

The development of a portable assistive device to aid patients affected by neuromuscular disorders has been the ultimategoal of assistive robots since the late 1960s. Despite significant advances in recent decades, traditional rigid exoskeletonsare constrained by limited portability, safety, ergonomics, autonomy and, most of all, cost. In this study, we present thedesign and control of a soft, textile-based exosuit for assisting elbow flexion/extension and hand open/close. We describea model-based design, characterisation and testing of two independent actuator modules for the elbow and hand,respectively. Both actuators drive a set of artificial tendons, routed through the exosuit along specific load paths, thatapply torques to the human joints by means of anchor points. Key features in our design are under-actuation and the useof electromagnetic clutches to unload the motors during static posture. These two aspects, along with the use of 3Dprinted components and off-the-shelf fabric materials, contribute to cut down the power requirements, mass and overallcost of the system, making it a more likely candidate for daily use and enlarging its target population. Low-level control isaccomplished by a computationally efficient machine learning algorithm that derives the system’s model from sensorydata, ensuring high tracking accuracy despite the uncertainties deriving from its soft architecture. The resulting system isa low-profile, low-cost and wearable exosuit designed to intuitively assist the wearer in activities of daily living

The Influence of External Forces on Wrist Proprioception

Proprioception combines information from cutaneous, joint, tendon, and muscle receptors for maintaining a reliable internal body image. However, it is still a matter of debate, in both neurophysiology and psychology, to what extent such body image is modified or distorted by a changing haptic environment. In particular, what is worth investigating is the contribution of external forces on our perception of body and joint configuration. The proprioceptive acuity of fifteen young participants was tested with a Joint Position Matching (JPM) task, performed with the dominant wrist under five different external forces, in order to understand to what extent they affect proprioceptive acuity. Results show that accuracy and precision in target matching do not change in a significant manner as a function of the loading condition, suggesting that the multi-sensory integration process is indeed capable of discriminating different sub-modalities of proprioception, namely the joint position sense and the sense of force. Furthermore, results indicate a preference for target undershooting when movements are performed in a viscous or high resistive force field, rather than passive or null fields in which subjects did not show any predominance for under/over estimation of their position