Passive Elbow Movement Assistant (PEMA): A portable exoskeleton to compensate angle-dependent tone profile of the elbow joint post-stroke

Upper limb soft robotic wearable devices: a systematic review

INTRODUCTION

Soft robotic wearable devices, referred to as exosuits, can be a valid alternative to rigid exoskeletons when it comes to daily upper limb support. Indeed, their inherent flexibility improves comfort, usability, and portability while not constraining the user's natural degrees of freedom. This review is meant to guide the reader in understanding the current approaches across all design and production steps that might be exploited when developing an upper limb robotic exosuit.

METHODS

The literature research regarding such devices was conducted in PubMed, Scopus, and Web of Science. The investigated features are the intended scenario, type of actuation, supported degrees of freedom, low-level control, high-level control with a focus on intention detection, technology readiness level, and type of experiments conducted to evaluate the device.

RESULTS

A total of 105 articles were collected, describing 69 different devices. Devices were grouped according to their actuation type. More than 80% of devices are meant either for rehabilitation, assistance, or both. The most exploited actuation types are pneumatic (52%) and DC motors with cable transmission (29%). Most devices actuate 1 (56%) or 2 (28%) degrees of freedom, and the most targeted joints are the elbow and the shoulder. Intention detection strategies are implemented in 33% of the suits and include the use of switches and buttons, IMUs, stretch and bending sensors, EMG and EEG measurements. Most devices (75%) score a technology readiness level of 4 or 5.

CONCLUSION

Although few devices can be considered ready to reach the market, exosuits show very high potential for the assistance of daily activities. Clinical trials exploiting shared evaluation metrics are needed to assess the effectiveness of upper limb exosuits on target users.

Development of Self-Adaptable Mechanism to Compensate Angle-Dependent Flexor Tone of the Elbow Joint Post-stroke: A Pilot Study

Upper extremity impairments are common among stroke survivors. Robotic devices enable a high-dose of repetitive training for patients, but most systems are confined to the laboratory settings due to their complexity and power requirements. Previously we developed a passive elbow device that can counteract the angle-dependent tone of flexor muscles with hypertonia, but its efficacy was found limited as the increase in passive assistance during elbow extension was found not sufficient to provide assistance to those with more severe impairments. Therefore, in this study, we developed a 'self-adaptable' passive device that adjusts its assistance level based on the movements of patients. In addition to the morphological design to adjust moment arms of the elastic components, we incorporated a self-adaptation mechanism, in which the lengths of the elastic bands were adjusted by a pair of miniature linear motors based on the joint position feedback signals. The capacity of the device was then tested in a pilot testing with two healthy subjects, for whom angle-dependent flexion torque was implemented to simulate flexor hypertonia. The additional adjustment of passive component lengths was found to further increase the elbow extension assistance as the elbow joint extended. The proposed self-adapting mechanism, which does not require any complex control input from the experimenters, can be incorporated with the existing passive device to improve its functional efficacy in home-based training.