A Wearable Soft Robotic Exoskeleton for Hip Flexion Rehabilitation.

Leg motion is essential to everyday tasks, yet many face a daily struggle due to leg motion impairment. Traditional robotic solutions for lower limb rehabilitation have arisen, but they may bare some limitations due to their cost. Soft robotics utilizes soft, pliable materials which may afford a less costly robotic solution. This work presents a soft-pneumatic-actuator-driven exoskeleton for hip flexion rehabilitation. An array of soft pneumatic rotary actuators is used for torque generation. An analytical model of the actuators is validated and used to determine actuator parameters for the target application of hip flexion. The performance of the assembly is assessed, and it is found capable of the target torque for hip flexion, 19.8 Nm at 30°, requiring 86 kPa to reach that torque output. The assembly exhibits a maximum torque of 31 Nm under the conditions tested. The full exoskeleton assembly is then assessed with healthy human subjects as they perform a set of lower limb motions. For one motion, the Leg Raise, a muscle signal reduction of 43.5% is observed during device assistance, as compared to not wearing the device. This reduction in muscle effort indicates that the device is effective in providing hip flexion assistance and suggests that pneumatic-rotary-actuator-driven exoskeletons are a viable solution to realize more accessible options for those who suffer from lower limb immobility.

Tubular Jamming: A Variable Stiffening Method Toward High-Force Applications with Soft Robotic Components.

The use of soft robotic actuators is on the rise because these soft systems offer the advantage of being highly flexible, which affords safer robot-environment interactions and the gentleness necessary to handle delicate objects. However, this advantage becomes a shortcoming in high-force applications where flexible components fold and fail under large loads. Various methods were sought to meet this challenge by providing a level of rigidity to soft components, but previously proposed solutions bring their own drawbacks including bulky systems, addition of superfluous weight, and restriction of actuator motion. Alternatively, this article presents Tubular Jamming, a new and effective means of stiffening that is adaptable to motion, lightweight, and can be implemented with minimal equipment. In this study, the mechanism of tubular jamming is expounded and is demonstrated through two exemplary soft structures: a tubular jammed beam (TJB) and a tubular jammed hinge (TJH). Both TJB and TJH are exhibited in areas of fabrication, characterization, and a few possible examples of implementation in soft robotic systems. In the TJB structure, tubular jamming is found to increase bending stiffness by nearly threefold at the maximum pressure and packing ratio tested, compared with a traditional soft pneumatic actuator (SPA) beam. The TJB is shown to require less supply pressure to achieve the same performance as a traditional SPA and is shown to perform better in maintaining the vertical position of a borne object. A triangular support configuration made from TJBs is demonstrated to be proficient in weight bearing, supporting a load of nearly 33 times its own weight. In the TJH structure, tubular jamming is shown to have a compound effect on torque output, as three jammed tubule hinges produce approximately four times the torque of a single tubule hinge. The TJH is exhibited in a wearable elbow flexion device. Tubular jamming opens new possibilities for soft components to achieve the stiffness needed to perform high-force tasks such as weight bearing and large-scale actuation while retaining the suppleness to enable a safe robot-to-environment interface.

A Reconfigurable Pneumatic Bending Actuator with Replaceable Inflation Modules.

A fully reconfigurable, pneumatic bending actuator is fabricated by implementing the concept of modularity to soft robotics. The actuator features independent, removable, fabric inflation modules that are attached to a common flexible but non-inflating plastic spine. The fabric modules are individually fabricated by heat sealing a thermoplastic polyurethane-coated nylon fabric, whereas the spine is manufactured through fused deposition modeling 3D printing; the components can be assembled and dismantled without the aid of any external tools. The replacement of specific modules along the array facilitates the reconfiguration of the actuator's bending trajectory and torque output; likewise, the combination of inflation modules with dissimilar geometries translates to several different trajectories on a single spine and allows the actuator to bend into assorted, unique structures. A detailed description of the actuator's design is thoroughly presented. We explored how reconfiguration of the actuator's modular geometry affected both the steady state and the dynamic characteristics of the actuator. The torque output of the actuator is proportional to the magnitude of the pressure applied. The actuator was excited by sinusoidal and square pressure inputs, and a second-order linear fit was performed. There were no perceived changes in its performance even after 100,000 inflation and deflation cycles.