Soft Arm Research Articles

Integrated design of an aerial soft-continuum manipulator for predictive maintenance.

This article presents an integrated concept of an aerial robot used for predictive maintenance in the construction sector. The latter can be remotely controlled, allowing the localization of cracks on wall surfaces and the adaptive deposit of the material for in situ repairs. The use of an aerial robot is motivated by fast intervention, allowing time and cost minimizing of overhead repairs without the need for scaffolding. It is composed of a flying mobile platform positioned in stationary mode to guide a soft continuum arm that allows to reach the area of cracks with different access points. Indeed, some constructions have complex geometries that present problems for access using rigid mechanical arms. The aerial robot uses visual sensors to automatically identify and localize cracks in walls, based on deep learning convolutional neural networks. A centerline representing the structural feature of the crack is computed. The soft continuum manipulator is used to guide the continuous deposit of the putty material to fill the microscopic crack. For this purpose, an inverse kinematic model-based control of the soft arm is developed, allowing to estimate the length of the bending tubes. The latter are then used as inputs for a neural network to predict the desired input pressure to bend the actuated soft tubes. A set of experiments was carried out on cracks located on flat and oblique surfaces, to evaluate the actual performances of the predictive maintenance mechatronic robot.

Global Missile Proliferation: Challenges and Solutions

Developments in missile proliferation are analyzed, including the main drivers, trends, and actors. The increasing complexity of the global missile proliferation landscape is shown. They key areas of technological development are identified, as well as several types of missile proliferators, to substantiate the importance of missile proliferation in the context of international security. Existing and prospective mechanisms are discussed with respect to arms control, nonproliferation, and multilateral risk reduction measures. It is stressed that the existing mechanisms are aimed primarily at reducing the risks associated with creating delivery vehicles for weapons of mass destruction whereas the greatest importance is now attached to the potential use of conventionally armed missiles. It is proposed to concentrate efforts on “soft arms control” in order to lay a foundation for a gradual increase in controllability in the absence of real prospects for verifiable and intrusive multilateral measures.

Adaptive Hybrid FES-Force Controller for Arm Exosuit.

Patients suffering from neuromuscular diseases experience motor disabilities which hinder their independence during activities of daily living (ADLs). For such impaired subjects, robotic devices and Functional Electrical Stimulation (FES) are technologies commonly used to rehabilitate lost functions. Nevertheless, both systems present some limitations, and merging FES and robots in Hybrid Robotic Rehabilitation Systems allows to overcome these boundaries. Here we propose for the first time a hybrid cooperative controller involving FES and a soft wearable upper arm exosuit to rehabilitate elbow movements. We tested the designed hybrid controller on six healthy participants. The results showed how the proposed hybrid controller allowed the wearers to perform flexion movements with no significant decrease in accuracy and precision with respect to the exosuit alone, while significantly decreasing the fatigue level by about 63% and delaying its onset with respect to the FES action alone.

A policy gradient algorithm integrating long and short-term rewards for soft continuum arm control

A policy gradient algorithm integrating long and short-term rewards for soft continuum arm control

Bipedal Walking of Underwater Soft Robot Based on Data-Driven Model Inspired by Octopus.

The soft organisms in nature have always been a source of inspiration for the design of soft arms and this paper draws inspiration from the octopus’s tentacle, aiming at a soft robot for moving flexibly in three-dimensional space. In the paper, combined with the characteristics of an octopus’s tentacle, a cable-driven soft arm is designed and fabricated, which can motion flexibly in three-dimensional space. Based on the TensorFlow framework, a data-driven model is established, and the data-driven model is trained using deep reinforcement learning strategy to realize posture control of a single soft arm. Finally, two trained soft arms are assembled into an octopus-inspired biped walking robot, which can go forward and turn around. Experimental analysis shows that the robot can achieve an average speed of 7.78 cm/s, and the maximum instantaneous speed can reach 12.8 cm/s.

Visual Servoing for Pose Control of Soft Continuum Arm in a Structured Environment

For soft continuum arms, visual servoing is a popular control strategy that relies on visual feedback to close the control loop. However, robust visual servoing is challenging as it requires reliable feature extraction from the image, accurate control models and sensors to perceive the shape of the arm, both of which can be hard to implement in a soft robot. This letter circumvents these challenges by presenting a deep neural network-based method to perform smooth and robust 3D positioning tasks on a soft arm by visual servoing using a camera mounted at the distal end of the arm. A convolutional neural network is trained to predict the actuations required to achieve the desired pose in a structured environment. Integrated and modular approaches for estimating the actuations from the image are proposed and are experimentally compared. A proportional control law is implemented to reduce the error between the desired and current image as seen by the camera. The model together with the proportional feedback control makes the described approach robust to several variations such as new targets, lighting, loads, and diminution of the soft arm. Furthermore, the model lends itself to be transferred to a new environment with minimal effort.

Redundancy and overactuation in cephalopod-inspired soft robot arms

Current soft robotic arms commonly follow traditional—i.e. hard—robot design conventions. Omnidirectional soft arms most commonly consist of segments that contain three parallel longitudinal actuators, or actuator groups, of which one or two are activated to induce bending. This design uses the minimum number of actuators required for omnidirectional bending, which is consistent with traditional robot design but unnecessarily constrains the soft arm design space. The cephalopods that frequently inspire soft robot arms have tens of bundles of longitudinal muscle fibers, and these bundles are distributed around the limb circumference rather than grouped. This article analyzes fluid-driven soft arm architectures with up to 12 actuators, which mimics the redundant and distributed nature of cephalopod arms and tentacles, in order to investigate the performance implications of an arm morphology closer to nature. Overactuation (i.e. activating more than two actuators) was considered, which is possible because soft robots—unlike traditional robots—can tolerate misaligned or partially opposed actuation without jamming. A previously-developed generalizable model was used to simulate design performance, and a subset of the examined architectures were constructed and tested. Many-actuator soft arms achieve high strokes under equivalent load and equivalent actuation pressures, without sacrificing no-load reach. These arms are also able to achieve quasi-omnidirectionality, as well as to execute near constant-curvature turns using a simple actuation pattern and a single pressure signal. The introduced framework also enables non-circular cross sections that are not possible with minimalist arm designs, allowing the load capacity and reach to be tuned in multiple directions. Several elliptical cross section arms were analyzed to explore the potential of non-circular cross sections. Overactuated, many-actuator arms significantly expand the design space of soft arms, improving performance in some cases and introducing options to tailor behavior that are infeasible in structurally minimal arms.

Model Analysis of Robotic Soft Arms including External Force Effects.

Because robotic soft arms have a high power-to-weight ratio, low cost, and ease of manufacturability, increasing numbers of researchers have begun to focus on their characteristics in recent years. However, many urgent problems remain to be resolved. For example, soft arms are made of hyperelastic material, making it difficult to obtain accurate model predictions of the soft arm shape. This paper proposes a new modeling method for soft arms, combining the constant curvature model with Euler–Bernoulli beam theory. By combining these two modeling methods, we can quickly solve for the soft arm deformation under the action of an external force. This paper also presents an experimental platform based on a cable-driven soft arm to verify the validity of the proposed model. We carried out model verification experiments to test for different external effects. Experimental results show that the maximum error of our proposed soft arm deformation model is between 2.86% and 8.75%, demonstrating its effectiveness.

Redundancy and overactuation in cephalopod-inspired soft robot arms.

Current soft robotic arms commonly follow traditional - i.e., hard - robot design conventions. Omnidirectional soft arms most commonly consist of segments that contain three parallel longitudinal actuators, or actuator groups, of which one or two are activated to induce bending. This design uses the minimum number of actuators required for omnidirectional bending, which is consistent with traditional robot design but unnecessarily constrains the soft arm design space. The cephalopods that frequently inspire soft robot arms have tens of bundles of longitudinal muscle fibers, and these bundles are distributed around the limb circumference rather than grouped. This article analyzes fluid-driven soft arm architectures with up to 12 actuators, which mimic the redundant and distributed nature of cephalopod arms and tentacles. Over-constraints (activating more than two actuators) were considered, which are possible because soft robots - unlike traditional robots - can tolerate conflicting constraints without jamming. A previously-developed generalizable model was used to simulate design performance, and a subset of the examined architectures were constructed and tested. Many-actuator soft arms achieved high strokes under equivalent load without sacrificing no-load reach and were able to execute near constant-curvature turns with a simple actuation pattern. The framework introduced here also enables cross section variations that are not possible with minimalist designs.

Modeling the Soft Bellows of the Bionic Soft Arm

Conventional robots are strong, fast and rigid. Although these properties make them useful for industrial applications, for human machine collaborations they pose a threat. An alternative is provided by soft robots. However, model-based control algorithms for soft robots are not yet at the same level as for conventional robots. Their performance is often limited by their soft materials, which are difficult to model. The goal of this paper is to extend and increase the quality of the existing model for the bionic soft arm while ensuring real-time feasibility. In particular, the focus is on the soft bellows of the manipulator that actuates the robot. In this work, the three-dimensional geometrical problem of the inflating bellows is reduced to a two-dimensional problem that can be efficiently solved in real-time. The solution approximates the nonlinear behavior of the hyperelastic material and is part of a regressor, which then models the driving torque. In comparison to the existing model, the new developed model is able to describe hysteresis effects caused by the material. This increases the overall accuracy of the model. The results are backed up by experimental data.

Stiffness Modelling and Performance Evaluation of a Soft Cardiac Fixator Flexible Arm with Granular Jamming

To meet the practical application requirements of cardiac fixation during off-pump coronary artery bypass surgery, a soft cardiac fixator with a flexible arm was previously designed. To enable the soft cardiac fixator to adapt to uncertain external forces, this study evaluates the variable-stiffness performance of the flexible arm. First, the flexible arm was simplified as a soft silicone manipulator measuring 60 mm × 90 mm × 120 mm, which can actuate, soften, or stiffen independently along the length of the arm by combining granular jamming with input pressure. Then, the soft manipulator was modelled as a cantilever beam to analyse its variable-stiffness performance with granular jamming. Next, based on theoretical analysis and calculations, many experiments were conducted to evaluate the variable-stiffness performance of the soft manipulator. The experimental results demonstrated that the variable-stiffness performance is influenced by the flexible arm length, the size of the granules, and the input pressure.

Modeling of a bio-inspired soft arm with semicircular cross section for underwater grasping

Fluid-filled fiber-reinforced elastomeric enclosures (FREEs) with a circular cross section, inspired by the muscle structure of octopus arms, are a popular choice for actuators because of their high power density and relatively low manufacturing cost. However, the shape, flexibility, and grasping force of FREEs are slightly different from those of real octopus arms. A soft arm with a semicircular cross section has better bending performance than that of FREEs with a circular cross section and can thus more easily achieve flexible grasping. In this paper, to better describe the deformation of soft arm shape in an underwater environment, a model based on a constrained maximization volume is proposed for a semicylindrical soft arm. In particular, the model takes into account the effect of the expansion of the bottom on the semicylindrical soft arm and the proposed analytical model is used to analyze the factors that affect the helix radius of the soft arm, including the helix angles of the fibers, wall thickness, and inner radius of the soft arm. Then a method for fabricating soft arms with a semicircular cross section (length: 700 mm) and a method for extracting the helix radius are also proposed. Finally, a series of driving experiments is performed to measure the accuracy of the model using a hydraulic platform. Experimental results show that the maximum error rate of the helix radius is between 8.99% and 12.29%. The helix radius can be varied from 74.3 mm to 176 mm by changing the parameters of the soft arm.

Fiber-reinforced soft polymeric manipulator with smart motion scaling and stiffness tunability

Minimally invasive surgery (MIS) is emerging as a burgeoning mode of medical treatment and is widely adopted in practical clinical operations. Here, we report a soft manipulator that can actively deform and navigate through a narrow and constrained environment. Stiffness tunability, tremor filtration, and motion scaling capabilities are incorporated to ensure the position and posture of the manipulator during operation. Based on teleoperation through a handle shank, we demonstrate the capability of navigating through a complex, constrained, and narrow space of the human skeleton. By attaching a camera and syringe needle at the front tip of the soft manipulator, the capability of acupuncture treatment and in vivo drug delivery in a medical mannequin is further demonstrated. Finally, autonomous recognition and tracking systems are developed to ensure the surgeon can effortlessly teleoperate the soft manipulator to enter the human body. A soft manipulator navigating through a constrained environment is designed Stiffness tunability, tremor filtration, and motion scaling capabilities are explored Teleoperation through a handle shank demonstrates navigation through a human skeleton Acupuncture treatment and in vivo drug delivery in a medical mannequin are realized Existing surgical manipulators for MIS are typically structured as rigid and straight arms or as soft arms that lack active deformation. Zhang et al. propose a soft manipulator that can actively deform and navigate through a narrow and constrained environment. This work provides a potential teleoperated MIS mode for inaccessible lesion sites and thereby overcomes the challenges faced by existing medical devices in healthcare.

Koopman-Based Control of a Soft Continuum Manipulator Under Variable Loading Conditions

Controlling soft continuum manipulator arms is difficult due to their infinite degrees of freedom, nonlinear material properties, and large deflections under loading. This letter presents a data-driven approach to identifying soft manipulator models that enables consistent control under variable loading conditions. This is accomplished by incorporating loads into a linear Koopman operator model as states and estimating their values online via an observer within the control loop. Using this approach, autonomous control of a pneumatically actuated soft continuum manipulator is achieved. In several trajectory following experiments, this controller is shown to be more accurate and precise than controllers based on models that do not explicitly account for loading. The manipulator also successfully performs pick and place of objects with unknown mass, demonstrating the efficacy of this approach in executing real-world manipulation tasks.

Economic Multilateralism in Peril

The Doha Round of multilateral negotiations is at a stalemate. The aid situation is changing as many countries are graduating from the soft loan arm of the World Bank Group. Developing countries built up their foreign exchange reserves to avoid borrowing from the International Monetary Fund (IMF), leading the IMF to retrench. This article explores the evolution of multilateralism from, essentially, its political roots to the economic area after the First World War (FWW), though in a limited way, and more fully after the Second World War (SWW). We then discuss how the workings of these economic multilateral institutions resulted in the current situation, where they risk becoming irrelevant. Finally, the article discusses the possible role of theG20 in the revival of multilateralism and, in particular, the role that developing countries might play in the revival.

Kinematic modeling and control of a novel pneumatic soft robotic arm

A novel soft robotic arm (SRA) composed of two soft extensible arms (SEAs) and a soft bendable joint (SBJ) for space capture systems is presented in this paper. A diamond origami pattern was applied in the design of the SEAs, and large deformations of the SEAs in positive pressure were simulated using the nonlinear finite element method. A kinematic model of the SRA using the Denavit–Hartenberg method based on the assumption of constant curvatures was proposed. A closed-loop model-free control system based on a PID controller was developed using real-time data from a vision sensor system. The kinematic model and closed-loop model-free control system are experimentally evaluated on an SRA prototype by four experiments. The experimental results demonstrate that the derived kinematic model can finely describe the movement of the SRA and that the closed-loop control system can control the SRA to reach the desired destination or trajectory within an acceptable error and performs well in long-term repeated operations.

Development of Entrepreneurship in Universities

It is necessary for university students to be trained with real cases so that they experience experiential learning, where they have a concrete experience and learn from it. Integrating training, education, and soft skills arm them with the necessary tools to develop an entrepreneurial intention. This will be done by training multidisciplinary work using business models adapted to teaching entrepreneurship. Thus, achieving avoids drifting talent trained in universities, which does not find a stimulus to knowledge to achieve the development of their venture. It should be provided from schoolwork that can lead to potential businesses, through the association of different university careers to generate and enhance multidisciplinary professional student-student relationships.

Modeling and motion control of an octopus-like flexible manipulator actuated by shape memory alloy wires

Soft robots are concerned by researchers due to several characteristics, such as high adaptability in complex unstructured environments, safe interaction with environments, and a high degree of dexterity. The deformability and dexterity of the octopus arm are remarkable and interesting for the development of bioinspiration soft robots. In this study, we proposed a biomimetic flexible manipulator actuated by shape memory alloy (SMA) wires and its PI controller, and evaluated its performances with focused experiments. This study aims to find out the advantages of the developed manipulator actuated by SMA wires. We designed the bionic structure to achieve flexible bending in 3D space based on the analysis of the octopus muscle structure. Then we built the mathematical models that described the relationship between the bending angle and the driving parameters. Surprisingly, the soft movement capacity of the bionic manipulator was investigated at different heating voltages and PWM duty cycles by the PI controller based on the self-sensing resistance feedback. The soft manipulator was able to bend flexibly with the maximum bending angle of 60°. Compared to the traditional soft arm, the soft manipulator has higher accuracy, with the error of the deflection angle less than 5° and the errors of bending angles less than 2°.

Soft Robotic Manipulation System Capable of Stiffness Variation and Dexterous Operation for Safe Human–Machine Interactions

AbstractSoft robots have attracted great attention in the past decades owing to their unique flexibility and adaptability for accomplishing tasks via simple control strategies, as well as their inherent safety for interactions with humans and environments. Here, a soft robotic manipulation system capable of stiffness variation and dexterous operations through a remotely controlled manner is reported. The smart manipulation system consists of a soft omnidirectional arm, a dexterous multimaterial gripper, and a self‐powered human–machine interface (HMI) for teleoperation. The cable‐driven soft arm is made of soft elastomers and embedded with low melting point alloy as a stiffness‐tuning mechanism. The self‐powered HMI patches are designed based on the triboelectric nanogenerator that utilizes a sliding mode of tribo‐layers made of copper and polytetrafluoroethylene. The novel soft manipulation system has great potential for soft and remote manipulation and human machine interactions in a variety of applications from elderly care to surgical operation to agriculture harvesting.

Self-Locomotive Soft Actuator Based on Asymmetric Microstructural Ti3C2Tx MXene Film Driven by Natural Sunlight Fluctuation.

Soft actuators and microrobots that can move spontaneously and continuously without artificial energy supply and intervention have great potential in industrial, environmental, and military applications, but still remain a challenge. Here, a bioinspired MXene-based bimorph actuator with an asymmetric layered microstructure is reported, which can harness natural sunlight to achieve directional self-locomotion. We fabricate a freestanding MXene film with an increased and asymmetric layered microstructure through the graft of coupling agents into the MXene nanosheets. Owing to the excellent photothermal effect of MXene nanosheets, increased interlayer spacing favoring intercalation/deintercalation of water molecules and its caused reversible volume change, and the asymmetric microstructure, this film exhibits light-driven deformation with a macroscopic and fast response. Based on it, a soft bimorph actuator with ultrahigh response to solar energy is fabricated, showing natural sunlight-driven actuation with ultralarge amplitude and fast response (346° in 1 s). By utilizing continuous bending deformation of the bimorph actuator in response to the change of natural sunlight intensity and biomimetic design of an inchworm to rectify the repeated bending deformation, an inchwormlike soft robot is constructed, achieving directional self-locomotion without any artificial energy and control. Moreover, soft arms for lifting objects driven by natural sunlight and wearable smart ornaments that are combined with clothing and produce three-dimensional deformation under natural sunlight are also developed. These results provide a strategy for developing natural sunlight-driven soft actuators and reveal great application prospects of this photoactuator in sunlight-driven soft biomimetic robots, intelligent solar-energy-driven devices in space, and wearable clothing.