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Showing papers on "Actuator published in 2022"


Journal ArticleDOI
Lin Guohuai1, Hongyi Li1, Hui Ma1, Deyin Yao1, Renquan Lu1 
TL;DR: Using neural networks and fault estimators to approximate unknown nonlinear dynamics and identify the actuator faults, respectively, the neighborhood observer-based neural fault-tolerant controller with dynamic coupling gains is designed and it is proved that the state of each follower can synchronize with the leader's state under a directed graph.
Abstract: This paper considers the human-in-the-Ioop leader-following consensus control problem of multi-agent systems (MASs) with unknown matched nonlinear functions and actuator faults. It is assumed that a human operator controls the MASs via sending the command signal to a non-autonomous leader which generates the desired trajectory. Moreover, the leader's input is nonzero and not available to all followers. By using neural networks and fault estimators to approximate unknown nonlinear dynamics and identify the actuator faults, respectively, the neighborhood observer-based neural fault-tolerant controller with dynamic coupling gains is designed. It is proved that the state of each follower can synchronize with the leader's state under a directed graph and all signals in the closed-loop system are guaranteed to be cooperatively uniformly ultimately bounded. Finally, simulation results are presented for verifying the effectiveness of the proposed control method.

120 citations


Journal ArticleDOI
TL;DR: In this paper , a bioinspired phototropic MXene-reinforced soft tubular actuator is reported that exhibits omnidirectional self-orienting ability and is capable of quickly sensing, continuously tracking, and adaptively interacting with incident light in all zenithal and azimuthal angles of 3D space.
Abstract: Endowing artificial advanced materials and systems with biomimetic self‐regulatory intelligence is of paramount significance for the development of somatosensory soft robotics and adaptive optoelectronics. Herein, a bioinspired phototropic MXene‐reinforced soft tubular actuator is reported that exhibits omnidirectional self‐orienting ability and is capable of quickly sensing, continuously tracking, and adaptively interacting with incident light in all zenithal and azimuthal angles of 3D space. The novelty of the soft tubular actuator lies in three aspects: 1) the new polymerizable MXene nanomonomer shows high compatibility with liquid crystal elastomer (LCE) matrices and can be in situ photopolymerized into the polymer networks, thus enhancing the mechanical and photoactuation properties; 2) the distinct hollow and radially symmetrical structure facilitates the actuator with fast photoresponsiveness and phototropic performance through retarding the heat conduction along the radial direction; 3) the MXene‐LCE soft tubular actuator simultaneously integrates sensing, actuation, and built‐in feedback loop, thus leading to a high light‐tracking accuracy and adaptive phototropism like a hollow stem of plants in nature. As a proof‐of‐concept demonstration, an adaptive photovoltaic system with solar energy harvesting maximization is illustrated. This work can provide insights into the development of artificial intelligent materials toward adaptive optoelectronics, intelligent soft robotics, and beyond.

89 citations


Journal ArticleDOI
TL;DR: In this paper , an overview of integrating bistable and multistable structures with soft actuating materials for diverse soft actuators and soft/flexible robots is given, along with a mechanics-guided structural design principles for five categories of basic bistability elements from 1D to 3D (i.e., constrained beams, curved plates, dome shells, compliant mechanisms of linkages with flexible hinges and deformable origami, and balloon structures).
Abstract: Snap‐through bistability is often observed in nature (e.g., fast snapping to closure of Venus flytrap) and the life (e.g., bottle caps and hair clippers). Recently, harnessing bistability and multistability in different structures and soft materials has attracted growing interest for high‐performance soft actuators and soft robots. They have demonstrated broad and unique applications in high‐speed locomotion on land and under water, adaptive sensing and fast grasping, shape reconfiguration, electronics‐free controls with a single input, and logic computation. Here, an overview of integrating bistable and multistable structures with soft actuating materials for diverse soft actuators and soft/flexible robots is given. The mechanics‐guided structural design principles for five categories of basic bistable elements from 1D to 3D (i.e., constrained beams, curved plates, dome shells, compliant mechanisms of linkages with flexible hinges and deformable origami, and balloon structures) are first presented, alongside brief discussions of typical soft actuating materials (i.e., fluidic elastomers and stimuli‐responsive materials such as electro‐, photo‐, thermo‐, magnetic‐, and hydro‐responsive polymers). Following that, integrating these soft materials with each category of bistable elements for soft bistable and multistable actuators and their diverse robotic applications are discussed. To conclude, perspectives on the challenges and opportunities in this emerging field are considered.

79 citations


Journal ArticleDOI
TL;DR: In this paper , the human-in-the-oop leader-following consensus control problem of multi-agent systems with unknown matched nonlinear functions and actuator faults is considered.
Abstract: This paper considers the human-in-the-Ioop leader-following consensus control problem of multi-agent systems (MASs) with unknown matched nonlinear functions and actuator faults. It is assumed that a human operator controls the MASs via sending the command signal to a non-autonomous leader which generates the desired trajectory. Moreover, the leader's input is nonzero and not available to all followers. By using neural networks and fault estimators to approximate unknown nonlinear dynamics and identify the actuator faults, respectively, the neighborhood observer-based neural fault-tolerant controller with dynamic coupling gains is designed. It is proved that the state of each follower can synchronize with the leader's state under a directed graph and all signals in the closed-loop system are guaranteed to be cooperatively uniformly ultimately bounded. Finally, simulation results are presented for verifying the effectiveness of the proposed control method.

73 citations


Journal ArticleDOI
15 Apr 2022-Science
TL;DR: Jiang et al. as discussed by the authors used turgor pressure and electroosmosis to realize a strong and fast hydrogel-based actuator, which can break a brick and construct underwater structures within a few minutes.
Abstract: Hydrogels are promising as materials for soft actuators because of qualities such as softness, transparency, and responsiveness to stimuli. However, weak and slow actuations remain challenging as a result of low modulus and osmosis-driven slow water diffusion, respectively. We used turgor pressure and electroosmosis to realize a strong and fast hydrogel-based actuator. A turgor actuator fabricated with a gel confined by a selectively permeable membrane can retain a high osmotic pressure that drives gel swelling; thus, our actuator exerts large stress [0.73 megapascals (MPa) in 96 minutes (min)] with a 1.16 cubic centimeters of hydrogel. With the accelerated water transport caused by electroosmosis, the gel swells rapidly, enhancing the actuation speed (0.79 MPa in 9 min). Our strategies enable a soft hydrogel to break a brick and construct underwater structures within a few minutes. Description Wrap it up Conventional stimuli-responsive hydrogel actuators generally suffer from weak actuation force and slow response speed because of the osmotic-driven actuation mechanism. They are also limited in how much pressure they can endure and will collapse or shatter if pushed too hard. Na et al. significantly increased the actuation stress of a hydrogel wrapping the gel in a relatively stiff but flexible semipermeable membrane, which confined the transverse deformation (see the Perspective by Jiang and Song). This effect is similar to the turgor pressure seen in biological cells. The actuation speed can also be enhanced by adding the electrolyte into the water solution and applying an electric field, which reduces the actuation time from hours to minutes. —MSL A selectively permeable membrane can enhance the strength and actuation speed of a hydrogel actuator.

71 citations


Journal ArticleDOI
TL;DR: In this article , a non-fragile PPC method for WVs is proposed to guarantee the prescribed performance for tracking errors in the presence of actuator saturation, and a low-complexity fuzzy neural control protocols are presented for velocity subsystem and altitude subsystem of WVs, while there is no need of recursive back stepping design.
Abstract: The existing prescribed performance control (PPC) strategies exhibit the fragility and nonguarantee of the prescribed performance when they are applied to dynamic systems with actuator saturation, and moreover, all of them are unable to quantitatively design prescribed performance. This article aims at remedying those deficiencies by proposing a new nonfragile PPC method for waverider vehicles (WVs) such that the quantitative prescribed performance can be guaranteed for tracking errors in the presence of actuator saturation. First, readjusting performance functions are developed to achieve quantitative prescribed performance and prevent the fragile problem. Then, low-complexity fuzzy neural control protocols are presented for velocity subsystem and altitude subsystem of WVs, while there is no need of recursive back-stepping design. Furthermore, auxiliary systems are designed to generate effective compensations on control constraints, which contributes to the guarantee of the desired prescribed performance, being proved via Lyapunov synthese. Finally, compared simulation results are given to validate the superiority.

61 citations


Journal ArticleDOI
TL;DR: In this article , a sliding-mode surface analysis for MIMO underactuated systems is presented, and the asymptotic stability of the system equilibrium point is strictly proven based on the composite surfaces.
Abstract: In the field of modern industrial engineering, many mechanical systems are underactuated, exhibiting strong nonlinear characteristics and high flexibility. However, the lack of control inputs brings about many difficulties for controller design and stability/convergence analysis., some unavoidable practical issues, e.g., plant uncertainties and actuator deadzones, make the control of underactuated systems even more challenging. Hence, with the aid of elaborately constructed finite-time convergent surfaces, this article provides the first solution to address the control problem for a class of multi-input-multi-output (MIMO) underactuated systems subject to plant uncertainties and actuator deadzones. Specifically, this article overcomes the main obstacle in sliding-mode surface analysis for MIMO underactuated systems, that is, by the presented analysis method, the asymptotic stability of the system equilibrium point is strictly proven based on the composite surfaces. In addition, the unknown parts of the actuated/unactuated dynamic equations and actuator deadzones can be simultaneously handled, which is important for real applications. Furthermore, we apply the proposed method to two kinds of typical underactuated systems, that is: 1) tower cranes and 2) double-pendulum cranes, and implement a series of hardware experiments to verify its effectiveness and robustness.

61 citations


Journal ArticleDOI
TL;DR: In this article , an adaptive dynamic programming-based data-driven controller for hydraulic servo actuators (HSA) with unknown dynamics is proposed, which requires neither the knowledge of the HSA dynamics nor exosystem dynamics.
Abstract: <p style='text-indent:20px;'>The hydraulic servo actuators (HSA) are often used in the industry in tasks that request great powers, high accuracy and dynamic motion. It is well known that HSA is a highly complex nonlinear system, and that the system parameters cannot be accurately determined due to various uncertainties, inability to measure some parameters, and disturbances. This paper considers control problem of the HSA with unknown dynamics, based on adaptive dynamic programming via output feedback. Due to increasing practical application of the control algorithm, a linear discrete model of HSA is considered and an online learning data-driven controller is used, which is based on measured input and output data instead of unmeasurable states and unknown system parameters. Hence, the ADP based data-driven controller in this paper requires neither the knowledge of the HSA dynamics nor exosystem dynamics. The convergence of the ADP based control algorithm is also theoretically shown. Simulation results verify the feasibility and effectiveness of the proposed approach in solving the optimal control problem of HSA.</p>

58 citations


Journal ArticleDOI
TL;DR: In this article , the authors investigated the tracking control problem of marine surface vessels (MSVs) in the presence of uncertain dynamics and external disturbances, and proposed a novel event-triggered indirect neuroadaptive fault-tolerant control scheme.
Abstract: This paper investigates the tracking control problem of marine surface vessels (MSVs) in the presence of uncertain dynamics and external disturbances. The facts that actuators are subject to undesirable faults and input saturation are taken into account. Benefiting from the smoothness of the Gaussian error function, a novel saturation function is introduced to replace each nonsmooth actuator saturation nonlinearity. Applying the hand position approach, the original motion dynamics of underactuated MSVs are transformed into a standard integral cascade form so that the vector design method can be used to solve the control problem for underactuated MSVs. By combining the neural network technique and virtual parameter learning algorithm with the vector design method, and introducing an event triggering mechanism, a novel event-triggered indirect neuroadaptive fault-tolerant control scheme is proposed, which has several notable characteristics compared with most existing strategies: 1) it is not only robust and adaptive to uncertain dynamics and external disturbances but is also tolerant to undesirable actuator faults and saturation; 2) it reduces the acting frequency of actuators, thereby decreasing the mechanical wear of the MSV actuators, via the event-triggered control (ETC) technique; 3) it guarantees stable tracking without the a priori knowledge of the dynamics of the MSVs, external disturbances or actuator faults; and 4) it only involves two parameter adaptations—a virtual parameter and a lower bound on the uncertain gains of the actuators—and is thus more affordable to implement. On the basis of the Lyapunov theorem, it is verified that all signals in the tracking control system of the underactuated MSVs are bounded. Finally, the effectiveness of the proposed control scheme is demonstrated by simulations and comparative results.

56 citations


Journal ArticleDOI
01 Jul 2022
TL;DR: In this paper , an adaptive fuzzy fault-tolerant control strategy is introduced to deal with the difficulties associated with the actuator faults and external disturbance, and a modified performance function, which is called the finite-time performance function (FTPF), is presented.
Abstract: In this article, finite-time-prescribed performance-based adaptive fuzzy control is considered for a class of strict-feedback systems in the presence of actuator faults and dynamic disturbances. To deal with the difficulties associated with the actuator faults and external disturbance, an adaptive fuzzy fault-tolerant control strategy is introduced. Different from the existing controller design methods, a modified performance function, which is called the finite-time performance function (FTPF), is presented. It is proved that the presented controller can ensure all the signals of the closed-loop system are bounded and the tracking error converges to a predetermined region in finite time. The effectiveness of the presented control scheme is verified through the simulation results.

55 citations


Journal ArticleDOI
TL;DR: In this paper , a water strider-inspired water-walking soft robot is demonstrated through combining superhydrophobic floating surface with hierarchical nanostructures and light-driven soft-actuation legs that are fabricated through in situ embedding of judiciously designed polymerizable miniaturized gold nanorods (MiniGNR nanomonomer) in liquid crystal network-based soft actuators.

Journal ArticleDOI
TL;DR: In this paper , the fundamental principles for controllable deformations and motions of hydrogels, with a focus on the structure designs and responsive functions of corresponding soft actuators and robots.
Abstract: ConspectusNature provides abundant inspiration and elegant paradigms for the development of smart materials that can actuate, morph, and move on demand. One remarkable capacity of living organisms is to adapt their shapes or positions in response to stimuli. Programmed deformations or movements in plant organs are mainly driven by water absorption/dehydration of cells, while versatile motions of mollusks are based on contraction/extension of muscles. Understanding the general principles of these morphing and motion behaviors can give rise to disruptive technologies for soft robotics, flexible electronics, biomedical devices, etc. As one kind of intelligent material, hydrogels with high similarity to soft biotissues and diverse responses to external stimuli are an ideal candidate to construct soft actuators and robots.The objective of this Account is to give an overview of the fundamental principles for controllable deformations and motions of hydrogels, with a focus on the structure designs and responsive functions of the corresponding soft actuators and robots. This field has been rapidly developed in recent years with a growing understanding of working principles in natural organisms and a substantial revolution of manufacturing technologies to devise bioinspired hydrogel systems with desired structures. Diverse morphing hydrogels and soft actuators/robots have been developed on the basis of several pioneering works, ranging from bending and folding deformations of bilayer hydrogels to self-shaping of non-Euclidean hydrogel surfaces, and from thermoactuated bilayer gel "hands" to electrodriven polyelectrolyte gel "worms". These morphing hydrogels have demonstrated active functions and versatile applications in biomedical and engineering fields.In this Account, we discuss recent progress in morphing hydrogels and highlight the design principles and relevant applications. First, we introduce the fundamentals of basic deformation modes, together with generic structure features, actuation strategies, and morphing mechanisms. The advantages of in-plane gradient structures are highlighted for programmable deformations by harnessing the out-of-plane buckling with bistability nature to obtain sophisticated three-dimensional configurations. Next, we give an overview of soft actuators and robots based on morphing hydrogels and focus on the working principles of the active systems with different structure designs. We discuss the advancements of hydrogel-based soft robots capable of swift locomotion with different gaits and emphasize the significances of structure control and dynamic actuation. Then we summarize versatile applications of hydrogel-based actuators and robots in biomedicines, cargo delivery, soft electronics, information encryption, and so forth. Some hydrogel robots with a built-in feedback loop and self-sensing system exhibit collaborative functions and advanced intelligence that are informative for the design of next-generation hydrogel machines. Finally, concluding remarks are given to discuss future opportunities and remaining challenges in this field. For example, miniature hydrogel-based actuators/robots with therapeutic or diagnostic functions are highly desired for biomedical applications. The morphing mechanisms summarized in this Account should be applicable to other responsive materials. We hope that this Account will inspire more scientists to be involved in this emerging area and make contributions to reveal novel working principles, design multifunctional soft machines, and explore applications in diverse fields.

Journal ArticleDOI
TL;DR: In this article , the development of soft pneumatic actuators and robots up to the date of publication is summarized and a special emphasis on recent advances such as novel designs, differential simulators, analytical and numerical modeling methods, topology optimization, data-driven modeling and control methods, hardware control boards and nonlinear estimation and control techniques.
Abstract: Soft robotics is a rapidly evolving field where robots are fabricated using highly deformable materials and usually follow a bioinspired design. Their high dexterity and safety make them ideal for applications such as gripping, locomotion, and biomedical devices, where the environment is highly dynamic and sensitive to physical interaction. Pneumatic actuation remains the dominant technology in soft robotics due to its low cost and mass, fast response time, and easy implementation. Given the significant number of publications in soft robotics over recent years, newcomers and even established researchers may have difficulty assessing the state of the art. To address this issue, this article summarizes the development of soft pneumatic actuators and robots up until the date of publication. The scope of this article includes the design, modeling, fabrication, actuation, characterization, sensing, control, and applications of soft robotic devices. In addition to a historical overview, there is a special emphasis on recent advances such as novel designs, differential simulators, analytical and numerical modeling methods, topology optimization, data-driven modeling and control methods, hardware control boards, and nonlinear estimation and control techniques. Finally, the capabilities and limitations of soft pneumatic actuators and robots are discussed and directions for future research are identified.

Journal ArticleDOI
TL;DR: In this paper , a customized 3D-printing process based on fused deposition modeling, printing a fully biodegradable gelatin-based hydrogel (biogel) ink into dimensionally stable, complex objects is presented.
Abstract: Soft robotics greatly benefits from nature as a source of inspiration, introducing innate means of safe interaction between robotic appliances and living organisms. In contrast, the materials involved are often nonbiodegradable or stem from nonrenewable resources, contributing to an ever-growing environmental footprint. Furthermore, conventional manufacturing methods, such as mold casting, are not suitable for replicating or imitating the complexity of nature’s creations. Consequently, the inclusion of sustainability concepts alongside the development of new fabrication procedures is required. We report a customized 3D-printing process based on fused deposition modeling, printing a fully biodegradable gelatin-based hydrogel (biogel) ink into dimensionally stable, complex objects. This process enables fast and cost-effective prototyping of resilient, soft robotic applications from gels that stretch to six times their original length, as well as an accessible recycling procedure with zero waste. We present printed pneumatic actuators performing omnidirectional movement at fast response times (less than a second), featuring integrated 3D-printed stretchable waveguides, capable of both proprio- and exteroception. These soft devices are endowed with dynamic real-time control capable of automated search-and-wipe routines to detect and remove obstacles. They can be reprinted several times or disposed of hazard-free at the end of their lifetime, potentially unlocking a sustainable future for soft robotics. Description A method for 3D printing of biodegradable hydrogels for sensor-clad, omnidirectional actuators is reported.

Journal ArticleDOI
TL;DR: In this article , a low-voltage, high-endurance, and power-dense DEA based on novel multiple-layering techniques and electrode-material optimization is presented.
Abstract: Dielectric elastomer actuators (DEAs) are a special class of artificial muscles that have been used to construct animal-like soft robotic systems. However, compared with state-of-the-art rigid actuators such as piezoelectric bimorphs and electromagnetic motors, most DEAs require higher driving voltages, and their power density and lifetime remain substantially lower. These limitations pose significant challenges for developing agile and powered autonomous soft robots. Here, a low-voltage, high-endurance, and power-dense DEA based on novel multiple-layering techniques and electrode-material optimization, is reported. When operated at 400 Hz, the 143 mg DEA generates forces of 0.36 N and displacements of 1.15 mm. This DEA is incorporated into an aerial robot to demonstrate high performance. The robot achieves a high lift-to-weight ratio of 3.7, a low hovering voltage of 500 V, and a long lifetime that exceeds 2 million actuation cycles. With 20 s of hovering time, and position and attitude error smaller than 2.5 cm and 2°, respectively, the robot demonstrates the longest and best-performing flight among existing sub-gram aerial robots. This important milestone demonstrates that soft robots can outperform their state-of-the-art rigid counterparts, and it provides an important step toward realizing power autonomy in soft robotic flights.

Journal ArticleDOI
TL;DR: In this paper , the adaptive neural decentralized two-bit-triggered control problem for interconnected large-scale nonlinear systems in nonstrict feedback forms (NFF) with actuator failures is studied.

Journal ArticleDOI
TL;DR: In this paper , the authors report a bistable domal hydrogel structure capable of spontaneous and reversible snapping under an electric field, where the electric field does not drive the gel directly.
Abstract: Venus flytrap and bladderwort, capable of rapid predation through a snapping transition, have inspired various designs of soft actuators and robots with fast actions. These designs, in contrast to their natural counterparts, often require a direct force or pressurization. Here, we report a bistable domal hydrogel structure capable of spontaneous and reversible snapping under an electric field. Unlike a mechanical force, the electric field does not drive the gel directly. Instead, it redistributes mobile ions that direct the migration of water molecules and bends the polyelectrolyte hydrogel. Subject to constraint from surrounding neutral gel, the elastic energy accumulates until suddenly released by snapping, just like the process in natural organisms. Several proof-of-concept examples, including an optical switch, a speedy catcher, and a pulse pump, are designed to demonstrate the versatile functionalities of this unit capable of articulate motion. This work should bring opportunities to devise soft robotics, biomedical devices, etc.

Journal ArticleDOI
TL;DR: In this paper , an adaptive neural-network command-filtered tracking control scheme for nonlinear systems with multiple actuator constraints is proposed, where the boundedness of all variables is guaranteed and the output tracking error fluctuates near the origin within a small bounded area.
Abstract: This article proposes an adaptive neural-network command-filtered tracking control scheme of nonlinear systems with multiple actuator constraints. An equivalent transformation method is introduced to address the impediment from actuator nonlinearity. By utilizing the command filter method, the explosion of complexity problem is addressed. With the help of neural-network approximation, an adaptive neural-network tracking backstepping control strategy via the command filter technique and the backstepping design algorithm is proposed. Based on this scheme, the boundedness of all variables is guaranteed and the output tracking error fluctuates near the origin within a small bounded area. Simulations testify the availability of the designed control strategy.

Journal ArticleDOI
TL;DR: In this article , a self-adaptive soft gripper, integrating pneumatic actuators and bistable carbon-fiber reinforced polymer laminates, was designed and tested.
Abstract: This study presents the design and test of a novel self-adaptive soft gripper, integrating pneumatic actuators and bistable carbon-fiber reinforced polymer laminates. The morphology was designed using the distinct structural characteristics of bistable structures; and the stable gripping configuration of the gripper was maintained through the bistability without continuous pressure application. The sufficient compliance of bistable structures makes the gripper versatile and adaptable to gripping deformable objects. First, a pneumatic-actuated method was introduced to achieve the reversible shape transition of the bistable structure. Next, three arrangement methods for actuators were analyzed with respect to the bistable transition and curvature, where it was found that the cross-arrangement is optimal. The effects of pneumatic actuators with different geometrical parameters on the response times are discussed, and the results show that the bistable structure can achieve shape transition within milliseconds under low pressure. Furthermore, the numerical and experimental results show good agreement between critical pressures and out-of-plane deformation. Furthermore, the shape retention function of the soft gripper was studied by using it to grasp objects of various sizes even when the pressure was reduced to the initial state. The bistable laminates exhibit sufficient compliance, and the deformed laminates can automatically accommodate the deformation of objects. The relationship between the weight and size of available gripping objects was studied; functional tests confirmed that the proposed soft gripper is versatile and adaptable for gripping objects of various shapes, sizes, and weights. This gripper has immense potential to reduce energy consumption in vacuum environments such as underwater and space.

Journal ArticleDOI
TL;DR: In this article , an elastomer actuator with sulfonated graphene-based gradient nanostructures is constructed via supramolecular multiscale assembly, and the resulting nanocomposite possesses an ultrahigh toughness of 141.19 MJ/m3 and high room-temperature self-healing efficiency (89%).
Abstract: Integration, being lightweight, and intelligence are important orientations for the future advancement of soft robots. However, existing soft robots are generally hydrogels or silicone rubber, which are inherently mechanically inferior and easily damaged and difficult to integrate functions. Here, inspired by nacre, an elastomer actuator with sulfonated graphene-based gradient nanostructures is constructed via supramolecular multiscale assembly. The resulting nanocomposite possesses an ultrahigh toughness of 141.19 MJ/m3 and high room-temperature self-healing efficiency (89%). The proof-of-concept robot is demonstrated to emphasize its maximum swimming speed of 2.67 body length per second, whose speed is comparable to that of plankton, representing the outperformance of most artificial soft robots. Furthermore, the robot can stably absorb pollutants and recover its robustness and functionality even when damaged. This study breaks the mutual exclusivity of functional execution and fast locomotions, and we anticipate that our nanostructural design will offer an effective extended path to other integrated robots that required multifunction integration.

Journal ArticleDOI
TL;DR: In this article , a cloud-based time-varying formation predictive control method with control input quantization is proposed to actively compensate for those random communication constraints, and a necessary and sufficient condition to achieve the quantized time-changing formation as well as the stability of the resulting closed-loop system is obtained.
Abstract: This brief is concerned with the time-varying formation problem for second-order networked multi-agent systems, which are subject to random communication delays and packet dropouts in the sensor-to-controller and controller-to-actuator channels of each agent. A cloud-based time-varying formation predictive control method with control input quantization is proposed to actively compensate for those random communication constraints. A definition of quantized time-varying formation is given, and then a necessary and sufficient condition to achieve the quantized time-varying formation as well as the stability of the resulting closed-loop system is obtained, which is independent of random communication constraints and quantization errors. Simulation results are provided to verify the effectiveness of the proposed method.

Journal ArticleDOI
Chiyu Fu1, Zhigang Xia, Christopher Hurren1, Azadeh Nilghaz1, Xungai Wang1 
TL;DR: In this paper, a critical review on the recently developed functional textiles as reinforcements, sensors, and actuators in soft robotics has been provided and the future trends and current strategies that can be employed in textile-based actuator manufacturing process have been explored to address the critical challenges in soft robotic manufacturing.

Journal ArticleDOI
TL;DR: In this paper , a critical review on the recently developed functional textiles as reinforcements, sensors, and actuators in soft robotics has been provided and the future trends and current strategies that can be employed in textile-based actuator manufacturing process have been explored to address the critical challenges in soft robotic manufacturing.

Journal ArticleDOI
TL;DR: In this paper , a review of actuator mechanisms and control strategies, including open-loop control, closedloop control and autonomous control, is presented, and the emerging directions are forecasted from the perspectives of interfacing between controller and actuator, underactuated control strategies and implementation of artificial intelligence.
Abstract: Soft robots have recently attracted increased attention because their characteristics of low‐cost fabrication, durability, and deformability make them uniquely suited for applications in bio‐integrated systems. Being fundamentally different from traditional rigid robots, soft robots exhibit properties of infinite degrees of freedom (DOF) and nonlinear materials properties that require innovations in control systems. With the rapid development of materials science, robotics, and artificial intelligence, the diversification of actuator mechanisms and algorithms has enabled a wide range of unique control strategies. This review summarizes the basics of actuator mechanisms and control strategies, including open‐loop control, closed‐loop control, and autonomous control, and discusses their implementation from diversified perspectives. Control strategies are evaluated based on their compatibility with materials sets, application goals, and implementation route. The emerging directions are forecasted from the perspectives of interfacing between controller and actuator, underactuated control strategies, and implementation of artificial intelligence (AI).

Journal ArticleDOI
TL;DR: In this article , a fault-tolerant consensus control of a general nonlinear multi-agent system subject to actuator faults and disturbed and faulty networks is proposed by using neural network (NN) and adaptive control techniques.
Abstract: This article addresses the problem of fault-tolerant consensus control of a general nonlinear multiagent system subject to actuator faults and disturbed and faulty networks. By using neural network (NN) and adaptive control techniques, estimations of unknown state-dependent boundaries of nonlinear dynamics and actuator faults, which can reflect the worst impacts on the system, are first developed. A novel NN-based adaptive observer is designed for the observation of faulty transformation signals in networks. On the basis of the NN-based observer and adaptive control strategies, fault-tolerant consensus control schemes are designed to guarantee the bounded consensus of the closed-loop multiagent system with disturbed and faulty networks and actuator faults. The validity of the proposed adaptively distributed consensus control schemes is demonstrated by a multiagent system composed of five nonlinear forced pendulums.

Journal ArticleDOI
TL;DR: In this paper , an adaptive neural-network-based fault-tolerant control scheme for a flexible string considering the input constraint, actuator gain fault, and external disturbances was proposed.
Abstract: We propose an adaptive neural-network-based fault-tolerant control scheme for a flexible string considering the input constraint, actuator gain fault, and external disturbances. First, we utilize a radial basis function neural network to compensate for the actuator gain fault. In addition, an observer is used to handle composite disturbances, including unknown approximation errors and boundary disturbances. Then, an auxiliary system eliminates the effect of the input constraint. By integrating the composite disturbance observer and auxiliary system, adaptive fault-tolerant boundary control is achieved for an uncertain flexible string. Under rigorous Lyapunov stability analysis, the vibration scope of the flexible string is guaranteed to remain within a small compact set. Numerical simulations verify the high control performance of the proposed control scheme.

Journal ArticleDOI
01 Feb 2022
TL;DR: In this paper , the actuator failure compensation control problem of robotic systems possessing dynamic uncertainties has been investigated, and the control design method based on barrier Lyapunov function (BLF) is used to strictly guarantee both the steady state performance and the transient performance.
Abstract: The actuator failure compensation control problem of robotic systems possessing dynamic uncertainties has been investigated in this paper. Control design against partial loss of effectiveness (PLOE) and total loss of effectiveness (TLOE) of the actuator are considered and described, respectively, and a disturbance observer (DO) using neural networks is constructed to attenuate the influence of the unknown disturbance. Regarding the prescribed error bounds as time-varying constraints, the control design method based on barrier Lyapunov function (BLF) is used to strictly guarantee both the steady-state performance and the transient performance. A simulation study on a two-link planar manipulator verifies the effectiveness of the proposed controllers in dealing with the prescribed performance, the system uncertainties, and the unknown actuator failure simultaneously. Implementation on a Baxter robot gives an experimental verification of our controller.

Journal ArticleDOI
Geonwoo Hwang1, Jihwan Park1, David Santiago Diaz Cortes1, Kyujin Hyeon1, Ki-Uk Kyung1 
TL;DR: This study demonstrates dynamic picking up and placing tasks with the designed gripper assembled to a robotic manipulator, and maximize the gripper performance by optimizing design factors of the electroadhesion and multilayered DE through experimental and simulation analysis.
Abstract: This article proposes a reinforced soft gripper with a mechanically strengthened electroadhesion pad and a multilayered dielectric elastomer (DE) actuator, for practical robotic application. The reinforcement of the electroadhesion pad is achieved by a metallic electrode pattern printed on a flexible polyimide film, which has a higher elastic modulus than typical soft materials. Moreover, the multilayered DE actuator is used to increase the bending force of the soft gripper. We maximize the gripper performance by optimizing design factors of the electroadhesion and multilayered DE through experimental and simulation analysis. In this study, we demonstrate dynamic picking up and placing tasks with the designed gripper assembled to a robotic manipulator. The gripper can lift and move various shaped objects 100 times heavier than the gripper's mass of 6.2 g. Moreover, the soft gripper with a large area can firmly hold 16.8 kg, with optimized specifications.

Journal ArticleDOI
01 Feb 2022-Carbon
TL;DR: In this article , a core-shell CNTs@LCE fiber soft actuator made of a liquid crystal elastomer (LCE) fiber coating with carbon nanotubes (CNTs) shell is presented.

Journal ArticleDOI
TL;DR: In this paper , a feedback control law is proposed to control the actuator's input current, to significantly attenuate the broadband vibration transmissibility from the base excitation to the bistable actuator mover.