Robust self-propulsion in sand using simply controlled vibrating cubes.

Much of the Earth and many surfaces of extraterrestrial bodies are composed of non-cohesive particulate matter. Locomoting on such granular terrain is challenging for common robotic devices, either wheeled or legged. In this work, we discover a robust alternative locomotion mechanism on granular media-generating movement via self-vibration. To demonstrate the effectiveness of this locomotion mechanism, we develop a cube-shaped robot with an embedded vibratory motor and conduct systematic experiments on granular terrains of various particle properties and slopes. We investigate how locomotion changes as a function of vibration frequency/intensity on such granular terrains. Compared to hard surfaces, we find such a vibratory locomotion mechanism enables the robot to move faster, and more stably on granular surfaces, facilitated by the interaction between the body and surrounding grains. We develop a numerical simulation of a vibrating single cube on granular media, enabling us to justify our hypothesis that the cube achieves locomotion through the oscillations excited at a distance from the cube's center of mass. The simplicity in structural design and controls of this robotic system indicates that vibratory locomotion can be a valuable alternative way to produce robust locomotion on granular terrains. We further demonstrate that such cube-shaped robots can be used as modular units for vibratory robots with capabilities of maneuverable forward and turning motions, showing potential practical scenarios for robotic systems.

Nonbiomorphic Passively Adaptive Swimming Robot Enables Agile Propulsion in Cluttered Aquatic Environments.

Aquatic swimmers, whether natural or artificial, leverage their maneuverability and morphological adaptability to operate successfully in diverse, complex underwater environments. Maneuverability allows swimmers the agility to change speed and direction within a constrained operating space, while morphological adaptability allows their bodies to deform as they avoid obstacles and pass through narrow gaps. In this work, we design a soft, modular, nonbiomorphic swimming robot that emulates the maneuverability and adaptability of biological swimmers. This tethered swimming robot is actuated by a two degree-of-freedom (2-DOF) cable-driven mechanism that enables not only common maneuvers, such as undulatory surging and pitch/yaw rotations, but also a roll rotation maneuver that is steady and controllable. This simple 2-DOF system demonstrates full 3D swimming abilities in a space-constrained underwater test bed. The soft compliant body and passive foldable fins of the swimming robot lend to its morphological adaptability, allowing it to move through narrow gaps, channels, and tunnels and to avoid obstacles without the need for a low-level feedback control strategy. The passive adaptability and maneuvering capabilities of our swimming robot offer a new approach to achieving underwater navigation in complex real-world settings.

Alpha-band activity in parietofrontal cortex predicts future availability of vibrotactile feedback in prosthesis use.

Prosthesis disuse and abandonment is an ongoing issue in upper-limb amputation. In addition to lost structural and motor function, amputation also results in decreased task-specific sensory information. One proposed remedy is augmenting somatosensory information using vibrotactile feedback to provide tactile feedback of grasping objects. While the role of frontal and parietal areas in motor tasks is well established, the neural and kinematic effects of this augmented vibrotactile feedback remain in question. In this study, we sought to understand the neurobehavioral effects of providing augmented feedback during a reach-grasp-transport task. Ten persons with sound limbs performed a motor task while wearing a prosthesis simulator with and without vibrotactile feedback. We hypothesized that providing vibrotactile feedback during prosthesis use would increase activity in frontal and parietal areas and improve grasp-related behavior. Results show that anticipation of upcoming vibrotactile feedback may be encoded in motor and parietal areas during the reach-to-grasp phase of the task. While grasp aperture is unaffected by vibrotactile feedback, the availability of vibrotactile feedback does lead to a reduction in velocity during object transport. These results help shed light on how engineered feedback is utilized by prostheses users and provide methodologies for further assessment in advanced prosthetics research.

Lateral bending and buckling aids biological and robotic earthworm anchoring and locomotion.

Earthworms (Lumbricus terrestris) are characterized by soft, highly flexible and extensible bodies, and are capable of locomoting in most terrestrial environments. Previous studies of earthworm movement focused on the use of retrograde peristaltic gaits in which controlled contraction of longitudinal and circular muscles results in waves of shortening/thickening and thinning/lengthening of the hydrostatic skeleton. These waves can propel the animal across ground as well as into soil. However, worms benefit from axial body bends during locomotion. Such lateral bending and buckling dynamics can aid locomotor function via hooking/anchoring (to provide propulsion), modify travel orientation (to avoid obstacles and generate turns) and even generate snake-like undulatory locomotion in environments where peristaltic locomotion results in poor performance. To the best of our knowledge, lateral bending and buckling of an earthworm's body has not yet been systematically investigated. In this study, we observed that within confined environments, worms use lateral bending and buckling to anchor their body to the walls of their burrows and tip (anterior end) bending to search the environment. This locomotion strategy improved the performance of our soft-bodied robophysical model of the earthworm both in a confined (in an acrylic tube) and above-ground heterogeneous environment (rigid pegs), where present peristaltic robots are relatively limited in terradynamic capabilities. In summary, lateral bending and buckling facilitates the mobility of earthworm locomotion in diverse terrain and can play an important role in the creation of low cost soft robotic devices capable of traversing a variety of environments.

Recent advances in wearable biosensing gloves and sensory feedback biosystems for enhancing rehabilitation, prostheses, healthcare, and virtual reality.

Wearable sensing gloves and sensory feedback devices that record and enhance the sensations of the hand are used in healthcare, prosthetics, robotics, and virtual reality. Recent technological advancements in soft actuators, flexible bioelectronics, and wireless data acquisition systems have enabled the development of ergonomic, lightweight, and low-cost wearable devices. This review article includes the most up-to-date materials, sensors, actuators, and system-packaging technologies to develop wearable sensing gloves and sensory feedback devices. Furthermore, this review contemplates the use of wearable sensing gloves and sensory feedback devices together to advance their capabilities as assistive devices for people with prostheses and sensory impaired limbs. This review is divided into two sections: one detailing the technologies used to develop strain, pressure, and temperature sensors integrated with a multifunctional wearable sensing glove, and the other reviewing the devices and methods used for wearable sensory displays. We discuss the limitations of the current methods and technologies along with the future direction of the field. Overall, this paper presents an all-inclusive review of the technologies used to develop wearable sensing gloves and sensory feedback devices.

Towards Sonomyography-Based Real-Time Control of Powered Prosthesis Grasp Synergies.

Sonomyography (ultrasound imaging) offers a way of classifying complex muscle activity and configuration, with higher SNR and lower hardware requirements than sEMG, using various supervised learning algorithms. The physiological image obtained from an ultrasound probe can be used to train a classification algorithm which can run on real time ultrasound images. The predicted values can then be mapped onto assistive or teleoperated robots. This paper describes the classification of ultrasound information and its subsequent mapping onto a soft robotic gripper as a step toward direct synergy control. Support Vector Classification algorithm has been used to classify ultrasound information into a set of defined states: open, closed, pinch and hook grasps. Once the model was trained with the ultrasound image data, real time input from the forearm was used to predict these states. The final predicted state output then set joint stiffnesses in the soft actuators, changing their interactions or synergies, to obtain the corresponding soft robotic gripper states. Data collection was carried out on five different test subjects for eight trials each. An average accuracy percentage of 93% was obtained averaged over all data. This real-time ultrasound-based control of a soft robotic gripper constitutes a promising step toward intuitive and robust biosignal-based control methods for robots.

Stretchable Nanocomposite Sensors, Nanomembrane Interconnectors, and Wireless Electronics toward Feedback-Loop Control of a Soft Earthworm Robot.

Sensors that can detect external stimuli and perceive the surrounding areas could offer an ability for soft biomimetic robots to use the sensory feedback for closed-loop control of locomotion. Although various types of biomimetic robots have been developed, few systems have included integrated stretchable sensors and interconnectors with miniaturized electronics. Here, we introduce a soft, stretchable nanocomposite system with built-in wireless electronics with an aim for feedback-loop motion control of a robotic earthworm. The nanostructured strain sensor, based on a carbon nanomaterial and a low-modulus silicone elastomer, allows for seamless integration with the body of the soft robot that can accommodate large strains caused by bending, stretching, and physical interactions with obstacles. A scalable, cost-effective, and screen-printing method manufactures an array of the strain sensors that are conductive and stretchable over 100% with a gauge factor over 38. An array of nanomembrane interconnectors enables a reliable connection between soft sensors and wireless electronics while tolerating the robot's multimodal movements. A set of computational and experimental studies of soft materials, stretchable mechanics, and hybrid packaging provides the key design factors for a reliable, nanocomposite sensor system. The miniaturized wireless circuit, embedded in the robot joint, offers real-time monitoring of strain changes during the motions of a robotic segment. Collectively, the soft sensor system presented in this work shows great potential to be integrated with other flexible, stretchable electronics for applications in soft robotics, wearable devices, and human-machine interfaces.

Optical Sensor-Embedded Pneumatic Artificial Muscle for Position and Force Estimation.

This study presents the design of a pneumatic artificial muscle with integrated soft optical sensing for estimation of muscle contraction length and contraction force. Each optical sensor uses an light emitting diode (LED)-photodiode pair to measure the light reflected by a silicone diaphragm embedded in the muscle. One diaphragm is designed to respond primarily to changes in muscle pressure, whereas the other is designed to respond to changes in muscle length. Muscle sensors were calibrated by measuring muscle contraction force versus length for a range of fixed muscle pressures and then mapping optical sensor data to the corresponding length and force data. To evaluate sensorized muscle performance in a robotic system, two antagonistic muscle pairs were used to actuate a planar two-degree-of-freedom arm. In various static and dynamic tests, arm positions and forces were estimated from optical sensor measurements. Optical sensor estimates of static and dynamic end-effector position estimation yielded average errors of 1.3 and 1.1 cm, respectively. Optical sensor estimates of static and dynamic end-effector force yielded average total force errors of 0.16 and 0.12 N for maximum end-effector forces of 2.0 and 2.4 N, respectively.

Estimating surgical needle deflection with printed strain gauges.

The ability to track surgical needle deflection during procedures such as therapeutic drug delivery, biopsies, and medical device implantation allows clinicians to minimize positioning errors and procedural complications due to instrument deviations. We describe the use of a novel strain gauge printing method to sensorize surgical needles for the purpose of sensing needle shape and deflection during surgical procedures. The additive vapor-deposition based sensor fabrication method used here is capable of applying strain gauges (and resistive circuit elements) with micron-scale features onto surgical instruments of varying curvature and material composition without the need for mechanical machining. This fabrication method is used to apply several strain gauges onto an 18 gauge core biopsy needle to sense deflections. Validation experiments demonstrate a gauge factor of 1.16 for the printed strain gauges and nominal needle deflection measurement resolution of 500 microns.

Design considerations for an active soft orthotic system for shoulder rehabilitation.

Strokes affect over 750,000 people annually in the United States. This significant and disabling condition can result in paralysis that must be treated by regular sessions with a dedicated physical therapist in order to regain motor function. However, the use of therapists is expensive, in high demand, and requires patient travel to a rehabilitation clinic. We propose an inexpensive and wearable upper body orthotics system that can be used at home to provide the same level of rehabilitation as the current physical therapy standard of care. The system is composed of a soft orthotic device with an integrated cable actuation system that is worn over the upper body, a limb position sensing system, and an actuator package. This paper presents initial design considerations and the evaluation of a proof of concept system for shoulder joint rehabilitation. Through simulations and experimental evaluation, the system is shown to be adjustable, easily wearable, and adaptable to misalignment and anatomical variations. Insights provided by these initial studies will inform the development of a complete upper body orthotic system.