Immersive Virtual Reality paired with soft robotics may be synergized to create personalized assistive therapy experiences. Virtual worlds hold power to stimulate the user with newly instigated low-cost, high-performance commercial Virtual Reality (VR) devices to enable engaging and accurate physical therapy. Soft robotic wearables are a versatile tool in such stimulation. This preliminary study investigates a novel rehabilitative VR experience, Project Butterfly (PBF), that synergizes VR Mirror Visual Feedback Therapy with soft robotic exoskeletal support. Nine users of ranging ability explore an immersive gamified physio-therapy experience by following and protecting a virtual butterfly, completed with an actuated robotic wearable that motivates and assists the user to perform rehabilitative physical movement. Specifically, the goals of this study are to evaluate the feasibility, ease-of-use, and comfort of the proposed system. The study concludes with a set of design considerations for future immersive physio-rehab robotic-assisted games.

For stroke survivors and many other people with upper-extremity impairment, daily life can be difficult without properly functioning arms. Some modern physical therapy exercises focus on rehabilitating people with these troubles by correcting patients' perceptions of their own body to eventually regain complete control and strength over their arms again. Augmentative wearable robots, such as the upper-extremity exoskeletons and exosuits, may be able to assist in this endeavor. A common drawback in many of these exoskeletons, however, is their inability to conform to the natural flexibility of the human body without a rigid base. We have built one such exosuit to address this challenge: Compliant Robotic Upper-extremity eXosuit (CRUX). This robot is a compliant, lightweight, multi-DoF, portable exosuit that affords its wearer the ability to augment themselves in many unconventional settings (i.e. outside of a clinic). These attributes are largely achieved by using a modified tensegrity design situated according to measured lines of minimal-extension, where a network of tension members provide a foundation to apply augmentative forces via precisely placed power-lines. In this paper, we detail the design process of CRUX, the report on CRUX's prototypical composition, and describe the mimetic control algorithm used. We also discuss the results of three studies that illustrate the efficacy of CRUX's mimetic controller, CRUX's flexibility and compliance, and the metabolic cost reduction when users exercise with assistance from CRUX as opposed to without. We conclude this paper with a summary of our findings, potential use cases for this technology, and the direction of future related work.

Wearable robots can potentially offer their users enhanced stability and strength. These augmentations are ideally designed to actuate harmoniously with the user's movements and provide extra force as needed. The creation of such robots, however, is particularly challenging due to the underlying complexity of the human body. In this paper, we present a compliant, robotic exosuit for upper extremities called CRUX. This exosuit, inspired by tensegrity models of the human arm, features a lightweight (1.3 kg), flexible multi-joint design for portable augmentation. We also illustrate how CRUX maintains the full range of motion of the upper-extremities for its users while providing multi-DoF strength amplification to the major muscles of the arm, as evident by tracking the heart rate of an individual exercising said arm. Exosuits such as CRUX may be useful in physical therapy and in extreme environments where users are expected to exert their bodies to the fullest extent.

The flexibility and structural compliance of the biological shoulder joint allows humans to perform a wide range of motions with their arms. The current paper is a preliminary study in which we propose a structurally compliant robotic manipulator joint inspired by the human shoulder joint, which elastically deforms when actuated. The tensile actuation is similar to the contraction and extension of biological muscles. We present four separate models for the shoulder: a simple saddle, a complex saddle, a suspended tubercle, and interlocked tetrahedrons. The analysis explores the dynamics in each design to compare the inherent advantages and disadvantages, which gives insight into the design and development of better interfaces for biologically inspired human-oriented robotics.

In this paper, we present a lightweight, multi-axis compliant tensegrity joint that is biologically inspired by the human elbow. This tensegrity elbow actuates by shortening and lengthening cables in a method inspired by muscular actuation in a person. Unlike many series elastic actuators, this joint is structurally compliant not just along each axis of rotation, but along other axes as well. Compliant robotic joints are indispensable in unpredictable environments, including ones where the robot must interface with a person. The joint also addresses the need for functional redundancy and flexibility, traits which are required for many applications that investigate the use of biologically accurate robotic models.

Most traditional robotic mechanisms feature inelastic joints that are unable to robustly handle large deformations and off-axis moments. As a result, the applied loads are transferred rigidly throughout the entire structure. The disadvantage of this approach is that the exerted leverage is magnified at each subsequent joint possibly damaging the mechanism. In this paper, we present two lightweight, elastic, bio-inspired tensegrity robotic arms adapted from prior static models which mitigate this danger while improving their mechanism's functionality. Our solutions feature modular tensegrity structures that function similarly to the human elbow and the human shoulder when connected. Like their biological counterparts, the proposed robotic joints are flexible and comply with unanticipated forces. Both proposed structures have multiple passive degrees of freedom and four active degrees of freedom (two from the shoulder and two from the elbow). The structural advantages demonstrated by the joints in these manipulators illustrate a solution to the fundamental issue of elegantly handling off-axis compliance. Additionally, this initial experiment illustrates that moving tensegrity arms must be designed with large reachable and dexterous workspaces in mind, a change from prior tensegrity arms which were only static. These initial experiments should be viewed as an exploration into the design space of active tensegrity structures, particularly those inspired by biological joints and limbs.

Heat shields play a vital role in protecting space vehicles during the atmosphere reentry. Therefore, they are essential for space vehicles, and better designed heat shields will vastly improve the ability both of robots and humans to explore extraterrestrial destinations. The main goal of the current paper is to investigate the feasibility of designing, building and deploying a tensegrity-based heat shield, which would withstand the atmospheric reentry of a low gravity and dense atmosphere celestial body (such as Titan), where the reentry accelerations and therefore, drag forces, will be lower than in the case of a high gravity planet (e.g., Earth or Mars). The paper is a preliminary study, which investigates the parameters that would be helpful in designing tensegrity-based heat shields. We explore the dynamics of entry and how the atmospheric forces interact with the heat shield. Tensegrity structures consist of tension elements used in conjunction with rigid rods which are actuated by changing the lengths of the tension elements. The advantage of the proposed approach versus the traditional one (rigid heat shields) is that tensegrity structures are flexible structures able to adapt the shape to obtain an optimal reentry configuration. The proposed heat shield will be able to fold in a small space during transport (e.g., to the target celestial body), unfold when the target is reached and provide additional mobility for an optimal reentry pattern. However, to achieve a deployable configuration, the tensegrity structure must withstand significant dynamics and thermal loads. We will use NASA Tensegrity Robotics Toolkit (NTRT) to simulate the structural designs of the heat shield as well as for designing the controllers.

Multiagent learning has been shown to be e↵ective in creating control policies for sophisticated soft-robotic systems based on tensegrity structures (built from interconnected rods and cables). The distributed nature of the tension network within a tensegrity structure along with its smooth distribution of forces is a natural match for distributed learning. Indeed, multiagent learning has been used to make control policies that allow tensegrity robots to roll e ciently, climb hills and even go over obstacles. In this paper, we extend these results allowing a tensegrity robot to take advantage of its flexible structure to escape deep trenches, a situation that is usually unrecoverable regarding traditional rovers. Usualy these problems are tightly coupled with large, flat search spaces which are di cult for typical multiagent learning. As an alternative, we show how a two-step Monte Carlo algorithm combined with a simplified control space based on sinusoid actuations can be used to solve this problem. Using this technique, we are able to create control policies that allows a ball-shaped tensegrity robot to escape craters. To further investigate the utility of these control policies on these flexible structures, we were able to implemented this technique on under-actuated versions of our tensegrity robot model. We found that although a decrease in the number of functioning actuators made it more di cult for the robot to escape a crater, some control policies still allowed the robot to successfully escape, despite this limitation. This success is an important step in creating a robot that can navigate reliably over