A Variable Stiffness Bioinspired Swallowing Gripper Based on Particle Jamming

As the chameleon tongue swallows the food, it wraps the entrapped meat around the food, ensuring that it is completely enclosed and preventing it from falling off. Inspired by swallow behavior, this article introduces the design, manufacture, modeling, and experimentation of a variable stiffness swallowing gripper (VSSG). The VSSG is comprised of an intimal membrane, an adventitial membrane, and an internal medium of particles and liquid water. This gripper integrates swallowing behavior with a particle jamming mechanism, exhibiting both soft and rigid state. In the soft state, it gently swallows objects by folding its intimal and adventitial membranes. In the rigid state, the bearing capacity is enhanced by promoting particle jamming phenomenon through pumping out liquid water. Therefore, the proposed gripper has the capability to mitigate the issue of extrusion force applied on the object, while simultaneously enhancing the load-bearing capacity of swallowing gripper. In this article, the swallowing principle of the VSSG is analyzed, the mathematical model of the holding force and extrusion force is deduced, and preliminary experiments are carried out to verify the actual gripping effect of the gripper. The experimental results demonstrate that the VSSG can successfully swallow objects of different shapes in the soft state, exhibiting excellent flexibility and adaptability. The carrying capacity of the gripper in the rigid state increased approximately twofold compared with its soft state. In addition, several swallowing grippers with different filling medium were comparatively studied, and the results show that the VSSG has a large load-bearing capability.

A Mouth and Tongue Interactive Device to Control Wearable Robotic Limbs in Tasks where Human Limbs Are Occupied

The Wearable Robotic Limb (WRL) is a type of robotic arm worn on the human body, aiming to enhance the wearer's operational capabilities. However, proposing additional methods to control and perceive the WRL when human limbs are heavily occupied with primary tasks presents a challenge. Existing interactive methods, such as voice, gaze, and electromyography (EMG), have limitations in control precision and convenience. To address this, we have developed an interactive device that utilizes the mouth and tongue. This device is lightweight and compact, allowing wearers to achieve continuous motion and contact force control of the WRL. By using a tongue controller and mouth gas pressure sensor, wearers can control the WRL while also receiving sensitive contact feedback through changes in mouth pressure. To facilitate bidirectional interaction between the wearer and the WRL, we have devised an algorithm that divides WRL control into motion and force-position hybrid modes. In order to evaluate the performance of the device, we conducted an experiment with ten participants tasked with completing a pin-hole assembly task with the assistance of the WRL system. The results show that the device enables continuous control of the position and contact force of the WRL, with users perceiving feedback through mouth airflow resistance. However, the experiment also revealed some shortcomings of the device, including user fatigue and its impact on breathing. After experimental investigation, it was observed that fatigue levels can decrease with training. Experimental studies have revealed that fatigue levels can decrease with training. Furthermore, the limitations of the device have shown potential for improvement through structural enhancements. Overall, our mouth and tongue interactive device shows promising potential in controlling the WRL during tasks where human limbs are occupied.

Experimental Study on Double-Joint Soft Actuator and Its Dexterous Hand

In this paper, we propose a pneumatic double-joint soft actuator based on fiber winding and build a dexterous hand with 11 degrees of freedom. Firstly, soft actuator structural design is carried out according to the actuator driving principle and gives the specific manufacturing process. Then, an experimental analysis of the bending performance of a single soft actuator, including bending angle, speed, and force magnitude, is carried out by building a pneumatic control experimental platform. Finally, a series of dexterous robotic hand-grasping experiments is conducted. Different grasping methods are used to catch the objects and measure the objects' change in height, length, and rotation angle during the experiment. The results show that the proposed soft actuator is more consistent with the bending rule of human fingers, and that the gestures of the dexterous hand are more imaginable and flexible when grasping objects. The soft actuator can carry out horizontal and vertical movements, and rotation of the object in the dexterous hand, thus achieving better human-computer interaction.

Design, Computational Modelling and Experimental Characterization of Bistable Hybrid Soft Actuators for a Controllable-Compliance Joint of an Exoskeleton Rehabilitation Robot

This paper presents the mechatronic design of a biorobotic joint with controllable compliance, for innovative applications of “assist-as-needed” robotic rehabilitation mediated by a wearable and soft exoskeleton. The soft actuation of robotic exoskeletons can provide some relevant advantages in terms of controllable compliance, adaptivity and intrinsic safety of the control performance of the robot during the interaction with the patient. Pneumatic Artificial Muscles (PAMs), which belong to the class of soft actuators, can be arranged in antagonistic configuration in order to exploit the variability of their mechanical compliance for the optimal adaptation of the robot performance during therapy. The coupling of an antagonistic configuration of PAMs with a regulation mechanism can achieve, under a customized control strategy, the optimal tuning of the mechanical compliance of the exoskeleton joint over full ranges of actuation pressure and joint rotation. This work presents a novel mechanism, for the optimal regulation of the compliance of the biorobotic joint, which is characterized by a soft and hybrid actuation exploiting the storage/release of the elastic energy by bistable Von Mises elastic trusses. The contribution from elastic Von Mises structure can improve both the mechanical response of the soft pneumatic bellows actuating the regulation mechanism and the intrinsic safety of the whole mechanism. A comprehensive set of design steps is presented here, including the optimization of the geometry of the pneumatic bellows, the fabrication process through 3D printing of the mechanism and some experimental tests devoted to the characterization of the hybrid soft actuation. The experimental tests replicated the main operating conditions of the regulation mechanism; the advantages arising from the bistable hybrid soft actuation were evaluated in terms of static and dynamic performance, e.g., pressure and force transition thresholds of the bistable mechanism, linearity and hysteresis of the actuator response.

Workspace Volume of Human Bimanual Precision Manipulation Influenced by the Wrist Configuration and Finger Combination

Bimanual precision manipulation is an essential ability in daily human lives. However, the kinematic ability of bimanual precision manipulation due to its complexity and randomness was rarely discussed. This study firstly presents an objective quantitative evaluation of bimanual precision manipulation based on workspace volume. It focuses on studying the effects of the wrist and finger factors on the bimanual manipulation abilities by measuring the workspaces through which ten participants manipulated an object under the 12 situations (3 wrist configurations × 4 finger combinations). The results show that the wrists participation significantly increases the workspace for bimanual precision manipulation, while different finger combinations also substantially affect workspace volume. Therefore, we found an optimal hand situation (two indexes cooperating with the wrists participation), allowing the workspace to reach a volume of 1600cm³, which is ten times higher than the worst situation. Furthermore, the involvement of the right thumb can significantly increase the contribution ratio of finger movement in bimanual precision manipulation, making the movement more accurate and stable. The study has the potential to contribute to the researches in many domains, ranging from developing surgical devices, training doctors in microsurgical techniques, providing normative data for rehabilitation.

Playing the piano with a robotic third thumb: assessing constraints of human augmentation

Contemporary robotics gives us mechatronic capabilities for augmenting human bodies with extra limbs. However, how our motor control capabilities pose limits on such augmentation is an open question. We developed a Supernumerary Robotic 3rd Thumbs (SR3T) with two degrees-of-freedom controlled by the user’s body to endow them with an extra contralateral thumb on the hand. We demonstrate that a pianist can learn to play the piano with 11 fingers within an hour. We then evaluate 6 naïve and 6 experienced piano players in their prior motor coordination and their capability in piano playing with the robotic augmentation. We show that individuals’ augmented performance with the SR3T could be explained by our new custom motor coordination assessment, the Human Augmentation Motor Coordination Assessment (HAMCA) performed pre-augmentation. Our work demonstrates how supernumerary robotics can augment humans in skilled tasks and that individual differences in their augmentation capability are explainable by their individual motor coordination abilities.

A soft pneumatic bistable reinforced actuator bioinspired by Venus Flytrap with enhanced grasping capability

Soft actuators, as an important part of soft robotics, have attracted significant attention due to their inherent compliance, flexibility and safety. However, low capacity in force and load limits their applications. Prestored elastic energy can improve the capacity in output force and load of soft actuators. This work introduces a soft pneumatic bistable reinforced actuator inspired by the Venus Flytrap's bistable mechanism that allows for the storage of elastic energy. The proposed actuator consists of two separated 3D-printed actuation chambers that are attached to a central prestressed steel shell to achieve bistability. The pressure triggering the pneumatic bistable reinforced actuator from one stable state to the other is derived and validated by experiments. Further experimental comparisons between the proposed actuator and a dual chamber actuator show that the proposed design significantly improves the block tip force, load capacity and stiffness. The pneumatic bistable reinforced actuator also demonstrates superior performance in the actuation speed and bending angle under the same input pressure. Finally, a two-finger gripper is developed using the proposed actuator, which is demonstrated to grasp and hold various objects.

Soft Poly-Limbs: Toward a New Paradigm of Mobile Manipulation for Daily Living Tasks

We present the design and development of the fluid-driven, wearable, Soft Poly-Limb (SPL), from the Greek word polys, meaning many. The SPL utilizes the numerous traits of soft robotics to enable a novel approach in providing safe and compliant mobile manipulation assistance to healthy and impaired users. This wearable system equips the user with a controllable additional limb that is capable of complex three-dimensional motion in space. Similar to an elephant trunk, the SPL is able to manipulate objects using a variety of end effectors, such as suction adhesion or a soft grasper, as well as its entire soft body to conform around an object, able to lift 2.35 times its own weight. To develop these highly articulated soft robotic limbs, we provide a novel set of systematic design rules, obtained through varying geometrical parameters of the SPL through experimentally verified finite element method models. We investigate performance of the limb by testing the lifetime of the new SPL actuators, evaluating its payload capacity, operational workspace, and capability of interacting close to a user through a spatial mobility test. Furthermore, we are able to demonstrate limb controllability through multiple user-intent detection modalities. Finally, we explore the limb's ability to assist in multitasking and pick and place scenarios with varying mounting locations of the SPL around the user's body. Our results highlight the SPL's ability to safely interact with the user while demonstrating promising performance in assisting with a wide variety of tasks, in both work and general living settings.