This paper presents the design, fabrication, and preliminary results of a soft hip exosuit to assist hip flexion and extension during walking. The exosuit uses soft and compliant materials to create a wearable robot that has a low profile, low mass, and is highly flexible to freely move with the user’s natural range of motion. The Soft Robotic Hip Exosuit (SR-HExo) consists of flat fabric pneumatic artificial muscles (ff-PAM) that contract when pressurized. The ff-PAM actuators are oriented in an ‘X’ shape to allow for natural range of motion across the hip joint and can generate 190 N of force at 200 kPa in a 0.3 sec window. The ‘X’ configuration (X-ff-PAM) actuators were placed on the anterior and posterior sides of the hip joint with height adjustable Velcro straps. Extension assistance and flexion assistance was provided in 10-45% and 50-90% of the gait cycle, respectively. To evaluate the effectiveness of the SR-HExo with healthy participants, hip range of motion and muscle activity during walking were monitored using a motion capture system and surface electromyography sensors. The impact of the SR-HExo on the range of motion was minimal with only a 4.0oreduction from the target range of motion of 30o. The exosuit contributed to reducing hip muscle activity. Hip extensor muscles showed a reduction of 13.1% for the gluteus maximus and 6.6% for the biceps femoris. Hip flexor muscles showed a reduction of 10.7% for the iliacus and 27.7% for the rectus femoris.

This paper presents a soft robotic ankle-foot orthosis (SR-AFO) exosuit designed to provide support to the human ankle in the frontal plane without restricting natural motion in the sagittal plane. The SR-AFO exosuit incorporates inflatable fabric-based actuators with a hollow cylinder design which requires less volume than the commonly used solid cylinder design for the same deflection. The actuators were modeled and characterized using finite element analysis techniques and experimentally validated. The SR-AFO exosuit was evaluated on healthy participants in both a sitting position using a wearable ankle robot and a standing position using a dual-axis robotic platform to characterize the effect of the exosuit on the change of 2D ankle stiffness in the sagittal and frontal planes. For both sitting and standing test protocols, a trend of increasing ankle stiffness in the frontal plane was observed up to 50 kPa while stiffness in the sagittal plane remained relatively constant over pressure levels. During quiet standing, the exosuit could effectively change eversion stiffness at the ankle joint from about 20 to 70 Nm/rad at relatively low- pressure levels (<; 30 kPa). Eversion stiffness was 84.9 Nm/rad at 50 kPa, an increase of 387.5% from the original free foot stiffness.

This paper presents the design of the Multi-material Actuator for Variable Stiffness (MAVS), which consists of an inflatable soft fabric actuator fixed between two layers of rigid retainer pieces. The MAVS is designed to be integrated with a soft robotic ankle-foot orthosis (SR-AFO) exosuit to aid in supporting the human ankle in the inversion/eversion directions. This design aims to assist individuals affected with chronic ankle instability (CAI) or other impairments to the ankle joint. The MAVS design is made from compliant fabric materials, layered and constrained by thin rigid retainers to prevent volume increase during actuation. The design was optimized to provide the greatest stiffness and least deflection for a beam positioned as a cantilever with a point load. Geometric programming of materials was used to maximize stiffness when inflated and minimize stiffness when passive. An analytic model of the MAVS was created to evaluate the effects in stiffness observed by varying the ratio in length between the rigid pieces and the soft actuator. A finite element analysis (FEA) was generated to analyze and predict the behavior of the MAVS prior to fabrication. The results from the analytic model and FEA study were compared to experimentally obtained results of the MAVS. The MAVS with the greatest stiffness was observed when the gap between the rigid retainers was smallest and the rigid retainer length was smallest. The MAVS design with the highest stiffness at 100 kPa was determined, which required 26.71 ± 0.06 N to deflect the actuator 20 mm, and a resulting stiffness of 1,335.5 N/m and 9.1% margin of error from the model predictions.

This paper presents the design of a soft ankle-foot orthosis (AFO) exosuit to aid natural gait restoration for individuals suffering from foot drop. The sock-like AFO is comprised of soft actuators made from fabric-based, thermally-bonded nylon and designed to be worn over the users shoes. The system assists dorsiflexion during swing phase of the gait cycle utilizing a contracting soft actuator, and provides ankle joint proprioception during stance with a variable stiffness soft actuator. A computational model is developed using finite element analysis to optimize the performance characteristics of the fabric actuators prior to fabrication, maximize contraction, and minimize overall volume. The dorsiflexion actuator is able to achieve a linear tensile force of 197 N at 200 kPa. The variable stiffness actuator generates up to 1. 2 Nm of torque at the same pressure. The computational model and soft AFO are experimentally validated and with a healthy participant through kinematic and electromyography studies. When active the AFO is capable of reducing by 13.3% the activity of the muscle responsible for ankle dorsiflexion during the swing phase.

This paper investigates the design of a soft elbow exosuit capable of providing supplemental lifting assistance by reducing muscle activity of the bicep muscle. The aim is to improve the efficiency and endurance of workers who are tasked with repetitive lifting. The design consists of an array of pneumatically pressurized soft actuators, which are encased in nylon fabric that allows for a high force-to-weight ratio of 211.SN/g. An analytical model governing the bending behavior of two consecutive actuators and torque generated by the exosuit is developed, with test results showing less than 10% error from the theoretical model. An elbow joint torque value of 27.6N.m is achieved at 300kPa, which is comparable to the 30N.m maximum set by OSHA requirements in the USA. Further testing with a healthy participant is performed using surface electromyography (sEMG) sensors and a motion capture system to assess the capabilities of the exosuit to provide active assistance to the bicep during isometric and concentric contractions. Measurable assistance to lifting is observed with minimal obstruction to the user's range of motion for all experiments.