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International audience; This paper investigates a distributed fuzzy adaptive formation control for quadrotor multiple unmanned aerial vehicles under unmodeled dynamics and switching topologies. The unmanned aerial vehicles dynamics model is described by the Newton-Euler formula, and the actuator faults are considered in the system model in the form of multiplicative factors and additive factors. Due to the underactuated characteristics of the unmanned aerial vehicles, two objective attitude commands are generated by designing a virtual control signal, which are transmitted to the attitude subsystem, and then the position controller is solved. By constructing a distributed communication mechanism between unmanned aerial vehicles, an adaptive formation control strategy is proposed, which can enable unmanned aerial vehicles to update their position and speed online according to their neighbor information, and then achieve the required formation. In addition, a fuzzy adaptive sliding mode controller is designed to ensure that the tracking errors of unmanned aerial vehicles converge to the neighborhood of the origin. Finally, the simulation results verify the effectiveness of the proposed control strategy.

This article deals with the problem of decentralized resilient observer-based output-feedback control design for networked control systems (NCSs). The proposed scheme considers both network imperfections and security issues. It is assumed that the NCS is suffering from time-varying network-induced delays and time-varying transmission intervals. Moreover, data transmission is performed over a nonsecure network that suffers from a denial-of-service (DoS) attack. The DoS jamming attack has affected the network by the occurrence of consecutive packet dropouts, which result in attack-induced packet dropouts. Based on the fact that packet dropouts caused by DoS attacks naturally do not follow a specific statistical pattern, the attack-induced packet dropouts are modeled as an extension of time-varying intervals with no probability distribution. Sufficient conditions are provided to guarantee the uniformly globally exponential stability of the NCS in the form of linear matrix inequalities. Finally, the effectiveness and applicability of the proposed method are demonstrated by simulation results.

Human beings perceive the world through the senses of sight, hearing, smell, taste, touch, space, and balance. The first five senses are prerequisites for people to live. The sensing organs upload information to the nervous systems, including the brain, for interpreting the surrounding environment. Then, the brain sends commands to muscles reflexively to react to stimuli, including light, gas, chemicals, sound, and pressure. MXene, as an emerging two-dimensional material, has been intensively adopted in the applications of various sensors and actuators. In this review, we update the sensors to mimic five primary senses and actuators for stimulating muscles, which employ MXene-based film, membrane, and composite with other functional materials. First, a brief introduction is delivered for the structure, properties, and synthesis methods of MXenes. Then, we feed the readers the recent reports on the MXene-derived image sensors as artificial retinas, gas sensors, chemical biosensors, acoustic devices, and tactile sensors for electronic skin. Besides, the actuators of MXene-based composite are introduced. Eventually, future opportunities are given to MXene research based on the requirements of artificial intelligence and humanoid robot, which may induce prospects in accompanying healthcare and biomedical engineering applications.

The problem of finite-time prescribed performance control (PPC) for spacecraft attitude maneuvering is researched. To the best of the authors' knowledge, limited results have been reported. How to achieve the prescribed performance attitude tracking within a preset time interval is still an open problem, especially in the presence of inertia perturbations, external disturbances, actuator saturations, and faults. On account of this, a finite-time performance function is first constructed as the predefined boundary of tracking errors. Second, Chebyshev neural network is utilized to approximate the lumped uncertainties. Then, the Nussbaum gain technique compensating for actuator saturations and faults is incorporated into the backstepping design to develop a new fault-tolerant attitude controller. Both transient and steady-state performances (e.g., the maximum overshoot, steady-state error, and settling time) are guaranteed. Compared with the common PPC or finite-time control achievements on spacecraft attitude tracking, the setting time herein can be set in advance without relying on initial states. Finally, experiments are performed to verify the effectiveness of the solution and comparisons with related works are displayed. National Natural Science Foundation of ChinaNational Natural Science Foundation of China (NSFC) [61773108]; Natural Sciences and Engineering Research Council of CanadaNatural Sciences and Engineering Research Council of Canada (NSERC)CGIAR This work was supported in part by the National Natural Science Foundation of China under Grant 61773108, and in part by the Natural Sciences and Engineering Research Council of Canada.

The parallel connection of DC-DC converters requires the development of an appropriate control strategy that regulates load voltage and shares current amongst participating converters. This paper proposes a resilient and robust cooperative distributed control approach that simultaneously ensures voltage regulation and balanced current sharing in parallel DC-DC converters in the presence of false data injection attacks on control input channels. Based on analytical tools from network control and Lyapunov stability theory, concise stability certificates are derived. The proposed cooperative distributed control strategy guarantees resilience against unknown bounded attacks on the actuators of DC-DC converters and the robustness to uncertainties in load parameters and the physical parameters of converters. Furthermore, the control design for each converter does not require any knowledge about the number of participating converters. The detailed simulation and experimental results verify the satisfactory performance of the proposed method in voltage regulation and balanced current sharing in parallel converters, as well as resilience to bounded false data injection attacks.

Direct ink writing (DIW) of liquid crystal elastomers (LCEs) has rapidly paved its way into the field of soft actuators and other stimuli-responsive devices. However, currently used LCE systems for DIW require postprinting (photo)polymerization, thereby forming a covalent network, making the process time-consuming and the material nonrecyclable. In this work, a DIW approach is developed for printing a supramolecular poly(thio)urethane LCE to overcome these drawbacks of permanent cross-linking. The thermo-reversible nature of the supramolecular cross-links enables the interplay between melt-processable behavior required for extrusion and formation of the network to fix the alignment. After printing, the actuators demonstrated a reversible contraction of 12.7% or bending and curling motions when printed on a passive substrate. The thermoplastic ink enables recyclability, as shown by cutting and printing the actuators five times. However, the actuation performance diminishes. This work highlights the potential of supramolecular LCE inks for DIW soft circular actuators and other devices.

Heating, ventilation, and air conditioning (HVAC) systems are used to condition the indoor environment in buildings. They can be subjected to malfunctioning since they are the most extensively operated buildings' components that account alone for almost half of the total building energy usage. Therefore, fault diagnosis (FD) of the HVAC system is important to maintain the system's reliability and efficiency and provide preventive maintenance. This article presents a supervised FD strategy for single actuator faults in HVAC systems given that actuators, such as dampers and valves, are mostly prone to faults resulting in thermal discomfort and energy inefficiency in buildings. The proposed approach is based on 2-D convolutional neural networks (CNNs) using an efficient 1-D-to-2-D data transformation performed on the time-series signals acquired from the HVAC system. The performance of the CNNs is ensured by an optimal tuning of its significant hyperparameters using the Bayesian optimization algorithm toward maximizing the classification accuracy. The proposed 1-D-to-2-D data transformation approach is computationally efficient and eliminates the use of advanced signals preprocessing. It is performed in two schemes: the static and dynamic schemes to analyze the correlation between the system's variables and consider the temporal effects of the time-series signals without compromising the detection time. The proposed approach is developed and validated using simulation data collected from a three-zone HVAC system simulator using Transient System Simulation Tool (TRNSYS). It demonstrates improved performance compared to the 1-D CNN-based approach and the other standard data-driven approaches for actuator FD in HVAC systems. Scopus

This paper investigates the secure control problem for cyber-physical systems when the malicious data is injected into the cyber realm which is directly connecting to the actuators. Based on moving target defense and reinforcement learning, we propose a novel proactive and reactive defense control scheme. First, the system $(A,B)$ is modeled as a switching system consisting of several controllable pairs $(A,\mathcal{B}_{l})$ to facilitate the construction of the moving target defense control scheme. The controllable pairs $(A,\mathcal{B}_{l})$ can be altered to update system dynamics under certain unpredictable switching probabilities for each subsystem, which can prevent the adversaries from effective attacks. Second, both attack detection and isolation schemes are designed to accurately locate and exclude the compromised actuators from a switching sequence. Third, a reinforcement learning algorithm based on the zero-sum game theory is proposed to design the defense control scheme when there exist no controllable subsystems to switch. To demonstrate the effectiveness of the defense control scheme, a three-tank system under unknown cyber attacks is illustrated.

Soft robotics shows considerable promise for various underwater applications. Soft grippers as end-effectors are particularly useful for compliant and robust grasping compared to rigid mechanisms. In this work, we describe the design, fabrication and operation of a soft robotic hand driven by water hydraulics for underwater grasping. The proposed design has, in addition to the five fingers of a human hand, an extra soft thumb arranged symmetrically in an active soft palm. The soft fingers are designed with four chambers to enable bidirectional bending and deflection motions. We propose a novel elastic fiber reinforced structure to enhance and constrain the flexion movements of three palm actuators. The versatility of the underwater robotic hand is evaluated by implementing the human grasping gestures of the Feix taxonomy. Furthermore, we present a low-cost one-camera-multiple-mirrors imaging approach for capturing the grasps from multiple viewpoints simultaneously.

Soft robotics has attracted great attention owing to their immense potential especially in human-robot interfaces. However, the compliant property of soft robotics alone, without stiff elements, restricts their applications under load-bearing conditions. Here, biohybrid soft actuators, that create their own bone-like rigid layer and thus alter their stiffness from soft to hard, are designed. Fabrication of the actuators is based on polydimethylsiloxane (PDMS) with an Au film to make a soft substrate onto which polypyrrole (PPy) doped with poly(4-styrenesulfonic-co-maleic acid) sodium salt (PSA) is electropolymerized. The PDMS/Au/PPy(PSA) actuator is then functionalized, chemically and physically, with plasma membrane nanofragments (PMNFs) that induce bone formation within 3 days, without using cells. The resulting stiffness change decreased the actuator displacement; yet a thin stiff layer couldnot completely stop the actuators movement, while a relatively thick segment could, but resulted in partial delamination the actuator. To overcome the delamination, an additional rough Au layer was electroplated to improve the adhesion of the PPy onto the substrate. Finally, an alginate gel functionalized with PMNFs was used to create a thicker mineral layer mimicking the collagen-apatite bone structure, which completely suppressed the actuator movement without causing any structural damage. Funding Agencies|Japanese Society of the Promotion of Science, JSPS [BR170502]; KAKENHI [JP20H04534]; Japan Science and Technology Agency, JST; Swedish Research Council [F17603]; Promobilia Foundation [201808330454]; China Scholarship Council [JPJSBP 120209923]; JSPS [MG2019-8171]; STINT; Swedish Foundation for International Cooperation in Research and Higher Education [JPMJFR210X]; [VR2014-3079]

Soft continuum robots are highly flexible and adapt- able, making them ideal for unstructured environments such as the human body and agriculture. However, their high compliance and manoeuvrability make them difficult to model, sense, and control. Current control strategies focus on Cartesian space control of the end-effector, but few works have explored full-body control. This study presents a novel image-based deep learning approach for closed-loop kinematic shape control of soft continuum robots. The method combines a local inverse kinematics formulation in the image-space with deep convolutional neural networks for accurate shape control that is robust to feedback noise and mechanical changes in the continuum arm. The shape controller is fast and straightforward to implement; it takes only a few hours to generate training data, train the network, and deploy, requiring only a web camera for feedback. This method offers an intuitive and user-friendly way to control the robot’s 3D shape and configuration through teleoperation using only 2D hand-drawn images of the desired target state without the need for further user instruction or consideration of the robot’s kinematics.

This paper proposes a new design of an event-based dissipative asynchronous controller for the interval type2 (IT2) fuzzy Markov jump systems (MJSs) subject to sensor saturation and actuator nonlinearity. By resorting to a generalized performance index, the $H_{\infty}$, passive, and dissipative fuzzy control problems are solved in a unified framework. The event-based scheme is developed for the IT2 fuzzy MJSs subject to sensor saturation and actuator nonlinearity, and the energy consumption of communication can be reduced. Moreover, the system and controller modes are asynchronous, and a hidden Markov model (HMM) is employed to observe the modes of the original system. The Membership-Function-Dependent (MFD) approach is applied to analyze the stability of the closed-loop system. Finally, two examples are given to demonstrate the effectiveness of the proposed algorithms.

This article proposes a swirling actuator that uses the electromagnetic radial force and mechanical gears to generate rotational torque. The proposed actuator generates a rotating radial force between an inner stator and a swirler. The gears on the swirler and outer rotor convert the circular motion of the swirler to low-speed rotor rotation. Thus, the proposed actuator is aimed at low-speed high-torque applications. In this study, the air-gap radial flux density and electromagnetic radial force are investigated analytically and verified through finite-element analysis. The static radial force and output torque are measured in a prototype of the actuator. The system efficiency and the gear efficiency are evaluated. A peak torque density of 27 Nm/L with a small volume of 0.16 L is realized in the prototype.

This article contrives a neural-adaptive constrained controller of the cable towed air-ground recovery system subject to terrain obstacles, unmeasurable cable tensions, trailing vortex, wind gust, and actuator saturation. In air-ground recovery system modeling, the towed vehicle's nominal 6 DOF affine nonlinear dynamics and the cable system's finite links-joints dynamics are formulated. To achieve accurate air-ground recovery under terrain obstacles, an asymmetric barrier Lyapunov function-based flight controller of the towed vehicle is proposed, by transforming the terrain obstacles into time-varying constraints on the vehicle's trajectory. Then, to approximate the towed vehicle's lumped unknown dynamics caused by the unmeasurable cable tensions and airflows, several echo state network (ESN) approximators are established for velocity and attitude subsystems. By using the state approximation errors-based neural weights learning strategy and minimal learning parameter technique, these ESNs possess better transient behaviors and lower online computational burden. Furthermore, the actuator saturation is automatically monitored and released, by incorporating a specially designed auxiliary compensating system into the angular rate control law for compensation. The stability of the closed-loop system is analyzed. Finally, numerical simulations under two air-ground recovery scenarios are performed to demonstrate the performance of the proposed controller.

In this short paper, development of an adaptive fault tolerant control (FTC) using a virtual actuator framework is presented for one-sided Lipschitz nonlinear systems subjected to time-varying loss of effectiveness and additive actuator faults. The proposed controller does not require to have a separate unit to detect, isolate, and identify a fault, and it is completely independent from the nominal controller. Due to this important property, the virtual actuator can easily added between the faulty plant and the nominal controller and it can guarantee that the deviation of states from the nominal behavior of the system in the presence of actuator faults can be made arbitrary small. Simulation results are provided to show the efficacy of the proposed adaptive fault tolerant controller. Scopus

International audience; This paper proposes an Active Fault Tolerant Control (AFTC) framework for a quadcopter Unmanned Aerial Vehicle (UAV). The proposed framework is capable of achieving trajectory tracking, estimating states, as well as estimating and compensating for all four actuators multiplicative faults. The framework combines two optimization-based nonlinear estimation and control techniques; Nonlinear Moving Horizon Estimation (NMHE) and Nonlinear Model Predictive Control (NMPC). We formulate the NMHE algorithm such that it simultaneously estimates the states and the 4 actuators faults. These estimates are then provided to NMPC to achieve fault accommodation. To validate our proposed framework, we investigate two fault scenarios, where 4 actuators experience an abrupt and time-varying partial Loss Of Effectiveness (LOE) in the presence of noisy measurements. Finally, simulation results show satisfactory performance and prove that the proposed framework is numerically tractable and real-time applicable.

To face the demand for applications in which robots have to safely interact with humans and the environment, the research community developed new types of actuators with compliant characteristics. To embody compliance into the actuator, elastic elements with fixed or variable compliance can be used. Among the variable stiffness mechanisms, a popular approach is based on the agonistic-antagonistic (A-A) layout, where two prime movers are elastically connected to the output shaft of the actuator. Notwithstanding the conceptually simple realization of the A-A layout, one limitation is that, due to the nonlinear torque/deflection characteristic of the elastic transmissions and to the limited spring elongation, the stiffness range achievable at the output shaft reduces as the external torque increases. In this work, a novel layout, based on the A-A principle, is proposed to increase the torque/stiffness capability of the actuator. To achieve this result, we combine elastic transmissions with linear and nonlinear torque/deflection characteristics. The mathematical model of the new layout and a possible implementation are analyzed. Then, the design of a novel variable stiffness actuator is presented and experimental validations are shown to compare the new device with the benchmark.

Most robotic systems consist of heavy machine elements that help reduce the vibrations generated by motion and that support good positional accuracy. Large-sized actuators are needed for such systems. Energy consumption significantly increases in oversized robotic systems. The proposed solution to which is to design robotic systems in lightweight and flexible forms. This makes possible smaller overall structure and actuator sizes. However, such systems suffer from residual vibrations. One well-known control solution to residual vibration problem could be input shaping techniques. In this study, a new Fuzzy Logic-based intelligent input shaping selection technique has been proposed. With this proposed approach, it is possible to set optimum settling time, positioning accuracy of robotic systems, and minimum residual vibrations by implementing the crucial open-loop control approach. Comprehensive experience is needed to overcome design issues on command shaping and system modeling. Based on these design criteria constraints and extensive knowledge requirements, the recommended solution is a Fuzzy Logic-based intelligent input shaping technique for accurate modeling and parameter estimation of the systems. The proposed approach is a Fuzzy Logic-based intelligent input shaper selection and input shaper setting determination algorithm. The applicability of the proposed method was verified on the Quanser Flexible Link experimental setup.

We present the design and development of a non-linear series-elastic element based on repelling magnets. Progressive stiffness offers the transparency advantages of a low-stiffness elastic actuator at low load levels, and the high torque tracking bandwidth of a high-stiffness actuator at high loads. The design space of this magnet-based concept is thoroughly analysed, for both box- and arc-segment magnets. A proof-of-concept prototype is presented which is experimentally validated. A gain-scheduled torque controller is used to exploit its non-linear dynamics. Simulation and experimental results demonstrate the viability of the concept.

Passive and active exoskeletons have been used over recent decades. However, regarding many physiological systems, we see that the majority explore both active and passive elements to minimize energy consumption while retaining proper motion control. In light of this, we propose a design that combines compliant mechanisms as passive support for gravity balancing of the hand's weight and soft actuators as active support for wrist flexion-extension. Our approach offers a safe, lightweight solution that intrinsically complements and supports the wrist's degrees of freedom. We hypothesize that the proposed soft wearable device is able to increase the range of motion and reduce muscle fatigue while being energy-conservative by balancing of the passive and active subsystems. In this work, we perform a design feasibility study for such soft wrist exoskeletons, particularly focused on wrist flexion-extension rehabilitation. Through optimization, geometries for the required functionality of the compliant beam and soft actuator are obtained, and their performance as separate subsystems is evaluated by simulations and experiments. Under the appropriate inputs, we show that the system can introduce a controllable bifurcation. Through experiments, we investigate such bi-stability and explore its usefulness for rehabilitative support of wrist flexion-extension. In short, the proposed wearable can offer a viable, energy-efficient alternative to traditional rehabilitation technologies.

Development of high-performance flexible surgical instruments is important to simplify and enable new minimally invasive surgical procedures. New actuation technologies are necessary to produce flexible instrumentation that is capable of accessing difficult-to-reach anatomy and performing laborious tasks without damaging delicate tissues. Recently, concentric McKibben muscles and dual-chamber pneumatic artificial muscles (PAMs) have been proposed for use in miniature flexible robotic surgical instrumentation. In this study, several varieties of a hybrid concentric dual-chamber PAM design are built and their force generation and stroke length are compared to a contractile McKibben muscle. The concentric dual-chamber PAM is designed to provide surgical access for large diameter (1.5–2.0 mm) instruments to be delivered to the surgical site in a pneumatically sealed actuator suitable for miniaturization and integration into surgical devices used in fluid environments (fetal applications in particular). Force output of the concentric dual-chamber PAM is modeled and compared to experimental results. Initial results suggest that the newly introduced design produces a higher actuation force per unit length than traditional McKibben muscles. The prototype dual-channel PAM produced a maximum 15.25 N of force and 8.39 mm of stroke, in comparison to 13.31 N of force and 19.3 mm of stroke produced by a traditional contractile McKibben muscle of the same length, outer diameter, and materials. ispartof: Journal of Medical Robotics Research vol:7 issue:2 status: published

Bidimensional (2D) materials are nowadays being developed as outstanding candidates for electronic and optoelectronic components and devices. Targeted applications include sensing, energy conversion, and storage. Phosphorene is one of the most promising systems in this context, but its high reactivity under atmospheric conditions and its small-area/lab-scale deposition techniques have hampered the introduction of this material in real-world applications so far. However, phosphorene oxides in the form of low-dimensional structures (2D POx) should behave as an electroresponsive material according to recent theoretical studies. In the present work, we introduce electrospraying for the deposition of stoichiometric and large-area 2D POx nanoflakes starting from a suspension of liquid-phase-exfoliated phosphorene. We obtained 2D POx nanostructures with a mean surface area two orders of magnitude larger than phosphorene structures obtained with standard mechanical and liquid exfoliation techniques. X-ray spectroscopy and high-resolution electron microscopy confirmed the P2O5-like crystallographic structure of the electrosprayed flakes. Finally, we experimentally demonstrated for the first time the electromechanical responsivity of the 2D P2O5 nanoflakes, through piezoresponse force microscopy (PFM). This work sheds light on the possible implementation of phosphorus oxide-based 2D nanomaterials in the value chain of fabrication and engineering of devices, which might be easily scaled up for energy-harvesting/conversion applications.

Micro Transdermal Interface Platforms (MicroTIPs) will combine minimally invasive microneedle arrays with highly miniaturized sensors, actuators, control electronics, wireless communications and artificial intelligence. These patch-like devices will be capable of autonomous physiological monitoring and transdermal drug delivery, resulting in increased patient adherence and devolved healthcare. In this paper, we experimentally demonstrate the feasibility of controlled transdermal drug delivery using a combination of 500 μm tall silicon microneedles, a commercial micropump, pressure and flow sensors, and bespoke electronics. Using ex-vivo human skin samples and a customized application/retraction system, leak-free delivery of volumes ranging from 0.7-1.1 mL has been achieved in under one hour. Clinical Relevance — This work experimentally confirms the feasibility of combining micropumps with microneedle arrays for applications in transdermal drug delivery.

The use of Printed Circuit Boards (PCBs) has seen a remarkable growth over the last decade, with applications in engineering, medicine, biology, chemistry, etc [...]

To improve the perception of haptic feedback, materials and sense-modifier effects should be examined. Teflon, Nylon mesh, and Silicone overlays were tested in combination with lateral vibrations to study their impact on the tactile sense. A feelable point moving along a line was implemented through the use of a dynamically moving interference maximum generated via the offset actuation of four haptic exciters affixed to corners of a Gorilla Glass surface. This feedback was presented to eight participants in a series of randomized experiments. Both the Nylon mesh and Teflon covering revealed a statistically significant (p < 0.05) impact of improvement to the user performance in the task of dynamic haptic virtual straight lines localization. While Silicone covering, having three times greater friction than Gorilla Glass, has less or no impact on both decision time, the number of task repetitions, and error rate (p > 0.05). The lateral vibration modifier (60 Hz) can also successfully be used with an increase in performance by about twofold, at least that was demonstrated for both the Nylon mesh and Teflon covering. publishedVersion

The evolution toward “more electric” aircraft has seen a decisive push in the last decade due to growing environmental concerns and the development of new market segments (flying taxis). Such a push has involved both the propulsion components and the aircraft systems, with the latter seeing a progressive trend in replacing traditional solutions based on hydraulic power with electrical or electromechanical devices. Flight Control Systems (FCSs) are one of the aircraft systems affected the most since the adoption of Electromechanical Actuators (EMAs) would provide several advantages over traditional electrohydraulic or mechanical solutions, but their application is still limited due to their sensitivity to certain single points of failure that can lead to mechanical jams. The development of an effective and reliable Prognostics and Health Management (PHM) system for EMAs could help in mitigating the risk of a sudden critical failure by properly recognizing and tracking the ongoing fault and anticipating its evolution, thus boosting the acceptance of EMAs as the primary flight-control actuators in commercial aircraft. The paper is focused on the results of the preliminary activities performed within the CleanSky 2/Astib research program, dedicated to the definition of the iron bird of a new regional-transport aircraft able to provide some prognostic capabilities and act as a technological demonstrator for new PHM strategies for EMAs employed in-flight control systems. The paper is organized as follows. At first, a proper introduction to the research program is provided, along with a brief description of the employed approach. Hence the simulation models adopted for the study are presented and used to build synthetic databases to inform the definition of the PHM algorithm. The prognostic framework is then presented, and a preliminary assessment of its expected performance is discussed.

Robotics and intelligent systems are key technologies to promote efficient and innovative applications in the most diverse domains (industry, healthcare, agriculture, construction, mobility, etc.), performing and supporting activities that are not suitable to be performed by humans. Such activities are frequently time-consuming, repetitive tasks with low added value, physically demanding, and/or dangerous. Nevertheless, robotics and intelligent systems face several scientific and technological challenges related to their integration and interoperability with other systems, safety, flexibility, reconfigurability and autonomy. These challenges are especially relevant when robots operate in real unstructured environments and share the workspace with humans and other equipment. This Special Issue collects research achievements, ideas, and applications of advanced intelligent robotic systems, covering diverse technologies and application domains. Generally, the contributions cover optimal path planning strategies and innovative designs for mobile manipulators, the integration of robotic and intelligent systems, grasping, manipulation, teleoperation, haptics, user experience approaches for collaborative robots, and multi-agent systems. All issue:https://www.mdpi.com/journal/applsci/special_issues/Control_Robotics

To mitigate the effects of the lack of IoT standardization, including scalability, reusability, and interoperability, we propose a domain-agnostic monitoring and control framework (MCF) for the design and implementation of Internet of Things (IoT) systems. We created building blocks for the layers of the five-layer IoT architecture and built the MCF’s subsystems (monitoring subsystem, control subsystem, and computing subsystem). We demonstrated the utilization of MCF in a real-world use-case in smart agriculture, using off-the-shelf sensors and actuators and an open-source code. As a user guide, we discuss the necessary considerations for each subsystem and evaluate our framework in terms of its scalability, reusability, and interoperability (issues that are often overlooked during development). Aside from the freedom to choose the hardware used to build complete open-source IoT solutions, the MCF use-case was less expensive, as revealed by a cost analysis that compared the cost of implementing the system using the MCF to obtain commercial solutions. Our MCF is shown to cost up to 20 times less than normal solutions, while serving its purpose. We believe that the MCF eliminated the domain restriction found in many IoT frameworks and serves as a first step toward IoT standardization. Our framework was shown to be stable in real-world applications, with the code not incurring a significant increase in power utilization, and could be operated using common rechargeable batteries and a solar panel. In fact, our code consumed so little power that the usual amount of energy was two times higher than what is necessary to keep the batteries full. We also show that the data provided by our framework are reliable through the use of multiple different sensors operating in parallel and sending similar data at a stable rate, without significant differences between the readings. Lastly, the elements of our framework can exchange data in a stable way with very few package losses, being able to read over 1.5 million data points in the course of three months.

Haptic technology that provides tactile sensation feedback by utilizing actuators to achieve the purpose of human–computer interaction is obtaining increasing applications in electronic devices. This review covers four kinds of electromechanical actuators useful for achieving haptic feedback: electromagnetic, electrostatic, piezoelectric, and electrostrictive actuators. The driving principles, working conditions, applicable scopes, and characteristics of the different actuators are fully compared. The designs and values of piezoelectric actuators to achieve sophisticated and high-definition haptic effect sensations are particularly highlighted. The current status and directions for future development of the different types of haptic actuators are discussed. Agency for Science, Technology and Research (A*STAR) Published version The author from IMRE acknowledges partial supports by A*STAR, Singapore, RIE2020 Advanced Manufacturing and Engineering (AME) Programmatic Fund, (Grant No. A20G9b0135).

Shape memory alloys (SMA) are excellent candidates for implementation in actuator systems due to their ability to recover their original shape after high-strain loading through a thermally-induced phase transition. In this work, we propose and develop a novel SMA-metamaterial actuator which is capable of exhibiting a reversible, global elongation in multiple directions induced by the unidirectional contraction upon heating of a single SMA component. This actuator consists of (a) an SMA component, (b) a bias component and (c) the metamaterial geometry, with each component having a distinct function: (a) actuation activation, (b) reversibility of actuation upon deactivation and (c) amplifying and re-directing the uni-directional SMA actuation globally throughout the actuator, respectively. A prototype actuator was designed and tested in various configurations over multiple activation/deactivation cycles in order to demonstrate the functionality and reusability of this system. Furthermore, a theoretical model which predicts the actuation stroke of the system on the basis of the material properties of the SMA and bias components as well as the geometry of the metamaterial system was developed and validated. The findings of this work demonstrate the considerable potential of SMA-metamaterial actuators for implementation in systems requiring a multi-axial actuation output.

Although exosuits have several advantages compared to exoskeleton type of wearable robots, they have limitations, such as bulkiness and low control performance. This study addresses the design and evaluation of a compact, lightweight, and highly responsive actuator to be used for exosuits, based on the Quasi-Direct Drive (QDD) actuation. The design requirements of the actuator were set based on the actuation system used in the state-of-the-art exosuit from Harvard University (HE) so that it could be an improvement compared to HE. Several design concepts were comparatively evaluated to select the optimal design, and a design for the pulley embedded QDD (PEQDD) actuator was selected. The PEQDD was fabricated using mechanical components selected based on the design constraints or designed through mechanical analysis. Using a dynamometer, the efficiency map of the PEQDD was drawn. The control bandwidth comparison test with the motor originally used for HE showed improved bandwidth from 6.25 Hz to 20 Hz. Preliminary testing was done in walking and running conditions using an exosuit utilizing PEQDD. The test results showed that the actuator performance met all the design requirements.

The gold standard for the partial restoration of sensorineural hearing loss is cochlear implant surgery, which restores patients’ speech comprehension. The remaining limitations, e.g., music perception, are partly due to a gap between cochlear implant electrodes and the auditory nerve cells in the modiolus of the inner ear. Reducing this gap will most likely lead to improved cochlear implant performance. To achieve this, a bending or curling mechanism in the electrode array is discussed. We propose a silicone rubber–hydrogel actuator where the hydrogel forms a percolating network in the dorsal silicone rubber compartment of the electrode array to exert bending forces at low volume swelling ratios. A material study of suitable polymers (medical-grade PDMS and hydrogels), including parametrized bending curvature measurements, is presented. The curvature radii measured meet the anatomical needs for positioning electrodes very closely to the modiolus. Besides stage-one biocompatibility according to ISO 10993-5, we also developed and validated a simplified mathematical model for designing hydrogel-actuated CI with modiolar hugging functionality.

We have faced the preparation of fully water-soluble fluorescent peptide substrate with long-term environmental stability (in solution more than 35 weeks) and, accordingly, with stable results in the use of this probe in determining the activity of enzymes. We have achieved this goal by preparing a co-polymer of the commercial N-vinyl-2-pyrrolidone (99.5% mol) and a fluorescent substrate for trypsin activity determination having a vinylic group (0.5%). The activity of trypsin has been measured in water solutions of this polymer over time, contrasted against the activity of both the commercial substrate Z-L-Arg-7-amido-4-methylcoumarin hydrochloride and its monomeric derivative, prepared ad-hoc. Initially, the activity of the sensory polymer was 74.53 ± 1.72 nmol/min/mg of enzyme, while that of the commercial substrate was 20.44 ± 0.65 nmol/min/mg of enzyme, the former maintained stable along weeks and the latter with a deep decay to zero in three weeks. The ‘protection’ effect exerted by the polymer chain has been studied by solvation studies by UV–Vis spectroscopy, steady-state & time resolved fluorescence, thermogravimetry and isothermal titration calorimetry., "La Caixa" Foundation, under agreement LCF/PR/PR18/51130007. We also gratefully acknowledge the financial support provided by FEDER (Fondo Europeo de Desarrollo Regional) through Programa Operacional Factores de Competitividade (COMPETE), and the Spanish State Research Agency (PID2020-113264RB-I00/AEI/10.13039/501100011033). Centro de Química de Coimbra acknowledges Fundação para a Ciência e Tecnologia for financial support (Projects UIDB/00313/2020, UIDP/00313/2020). E.D.-P. thanks the “Concurso de Estímulo ao Emprego Científico” for the junior contract CEECIND/04136/2018.

Stretchable electrodes are more suitable for dielectric elastomer transducers (DET) the closer the mechanical characteristics of the electrodes and elastomer are. Here, a solvent-free synthesis and processing of conductive composites with excellent electrical and mechanical properties for transducers are presented. The composites are prepared by in situ polymerization of cyclosiloxane monomers in the presence of graphene nanoplatelets. The low viscosity of the monomer allows for easy dispersion of the filler, eliminating the need for a solvent. After the polymerization, a cross-linking agent is added at room temperature, the composite is solvent-free screen-printed, and the cross-linking reaction is initiated by heating. The best material shows conductivity σ = 8.2 S cm–1, Young's modulus Y10% = 167 kPa, and strain at break s = 305%. The electrode withstands large strains without delamination, shows no conductivity losses during repeated operation for 500 000 cycles, and has an excellent recovery of electrical properties upon being stretched at strains of up to 180%. Reliable prototype capacitive sensors and stack actuators are manufactured by screen-printing the conductive composite on the dielectric film. Stack actuators manufactured from dielectric and conductive materials that are synthesized solvent-free are demonstrated. The stack actuators even self-repair after a breakdown event., Macromolecular Rapid Communications, 43 (6), ISSN:1022-1336, ISSN:1521-3927

An actual problem on an IoT adaptive systems is to manage user preferences and local actuators specifications. This paper uses a multi agent system to achieve a Smart Environment System, that supports interaction between persons and physical spaces, that users smartly adapt to their preferences in a transparent way. This work proposes also a set of security customization’s to secure the actuators and users on space, that has been developed using a multi agent system architecture with different features to achieve a solution that achieve all the proposed objectives. info:eu-repo/semantics/publishedVersion

International audience; Digital Twin (DT) is one of the pillars of modern information technologies that plays an important role on industry's digitalization. A DT is composed of a real physical object, a virtual abstraction of the object and a bidirectional data flow between the physical and virtual components. This paper presents a DT-based tool, called TaS, to easily test and simulate IoT environments. The objective is to improve the testing methodologies in IoT systems to evaluate the possible impact of it on the physical world. We provide the conditions to test, predict errors and stress application depending on hardware, software and real world physical process. The tool is based on the DT concept in order to detect and predict failures in evolving IoT environments. In particular, the way to prepare the DT to support fault injection and cybersecurity threats is analyzed. The TaS tool is tested through an industrial case study, the Intelligent Transport System (ITS) provided by the INDRA company. Results of experiments are presented that show that our DT is closely linked to the real world.

Jumping is an important locomotion function to extend navigation range, overcome obstacles, and adapt to unstructured environments. In that sense, continuous jumping and direction adjustability can be essential properties for terrestrial robots with multimodal locomotion. However, only few soft jumping robots can achieve rapid continuous jumping and controlled turning locomotion for obstacle crossing. Here, we present an electrohydrostatically driven tethered legless soft jumping robot capable of rapid, continuous, and steered jumping based on a soft electrohydrostatic bending actuator. This 1.1 g and 6.5 cm tethered soft jumping robot is able to achieve a jumping height of 7.68 body heights and a continuous forward jumping speed of 6.01 body lengths per second. Combining two actuator units, it can achieve rapid turning with a speed of 138.4° per second. The robots are also demonstrated to be capable of skipping across a multitude of obstacles. This work provides a foundation for the application of electrohydrostatic actuation in soft robots for agile and fast multimodal locomotion., Jumping is an important locomotion function to extend navigation range, overcome obstacles, and adapt to unstructured environments. Here, authors demonstrate legless soft robot capable of rapid, continuous, and steered jumping based on a soft electrohydrostatic bending actuator.

In this article, a recently proposed at basic level novel suspension for road vehicles, the parallel active link suspension (PALS), is investigated in the realistic scenario of a sport utility vehicle (SUV) full car. The involved rocker-pushrod assembly is generally optimized to maximize the PALS capability in improving the suspension performance. To fully release the PALS functions of dealing with both low- and high-frequency road cases, a PID control scheme is first employed for the chassis attitude stabilization, focusing on the minimization of both the roll and pitch angles; based on a derived linear equivalent model of the PALS-retrofitted full car, an H∞ control scheme is designed to enhance the ride comfort and road holding; moreover, a frequency-dependent multiobjective control strategy that combines the developed PID and H∞ control is proposed to enable: 1) chassis attitude stabilization at 0-1 Hz; 2) vehicle vibration attenuation at 1-8 Hz; and 3) control effort penalization (for energy saving) above 10 Hz. With a group of ISO-defined road events tested, numerical simulation results demonstrate that, compared to the conventional passive suspension, the PALS has a promising potential in full-car application, with up to 70% reduction of the chassis vertical acceleration in speed bumps and chassis leveling capability of dealing with up to 4.3-m/s² lateral acceleration.

Highly compact and geometrically complex piezoceramics are required by a variety of electromechanical devices owing to their outstanding piezoelectricity, mechanical stability and extended application scenarios. 3D printing is currently the mainstream technology for fabricating geometrically complex piezoceramic components. However, it is hard to print piezoceramics in a curve shape while also keeping its compactness due to restrictions on the ceramic loading and the viscosity of feedstocks. Here, we report a gravity-driven sintering (GDS) process to directly fabricate curved and compact piezoceramics by exploiting gravitational force and high-temperature viscous behavior of sintering ceramic specimens. The sintered lead zirconate titanate (PZT) ceramics possess curve geometries that can be facilely tuned via the initial mechanical boundary design, and exhibit high piezoelectric properties comparable to those of conventional-sintered compact PZT (d33 = 595 pC/N). In contrast to 3D printing technology, our GDS process is suitable for scale-up production and low-cost production of piezoceramics with diverse curved surfaces. Our GDS strategy is an universal and facile route to fabricate curved piezoceramics and other functional ceramics with no compromise of their functionalities., Fabricating geometrically complex piezoceramics in compact sintered bodies has been difficult to achieve. Here the authors demonstrate a gravity-driven sintering strategy where high-temperature viscous behavior of piezoceramic allows for forming of complex shaped sintered bodies.

Kinks can appear along the contour of semiflexible polymers (biopolymers or synthetic ones), and they affect their elasticity and function. A regular sequence of alternating kink defects can form a semiflexible nanospring. In this article, we theoretically analyze the elastic behavior of such a nanospring with a point magnetic dipole attached to one end while the other end is assumed to be grafted to a rigid substrate. The rod-like segments of the nanospring are treated as weakly bending wormlike chains, and the propagator (Green’s function) method is used in order to calculate the conformational and elastic properties of this system. We analytically calculate the distribution of orientational and positional fluctuations of the free end, the force-extension relation, as well as the compressional force that such a spring can exert on a planar wall. Our results show how the magnetic interaction affects the elasticity of the semiflexible nanospring. This sensitivity, which is based on the interplay of positional and orientational degrees of freedom, may prove useful in magnetometry or other applications.

Electroactive polymer(EAP) is a “smart material” with high energy density, high electromechanical energy conversion efficiency, simple structure, good adaptability to the working environment, etc. It can be made into various shapes to realize flexible drivers. At present, the common EAP actuator is mainly composed of EAP film wound on a spring, and the output performance of this type of actuator is related to the spring stiffness, film prestretching rate, voltage, and other factors. Its working process is actually an electromechanical coupling process. In this paper, two types of cylindrical actuators are designed and tested. The electromechanical coupling mathematical model is constructed to simulate the driver. According to the experimental and simulation results, the relationship between the output displacement and elongation strain of EAP actuator and voltage, spring stiffness, and tensile rate is analyzed. It provides a reference and basis for the design of similar actuators.

Torque calculation is essential for selecting the appropriate motor to achieve the required torque at each joint of a hybrid exoskeleton. In recent years, the combined use of functional electrical stimulation (FES) and robotic devices, called hybrid robotic rehabilitation systems, has emerged as a promising approach for the rehabilitating of lower limb motor functions. Specifically, the implementation strategy of functional electrical stimulation walking aid combined with the design of the exoskeleton part is the main focus of our research team. This work copes with issues of the design process of a robotic exoskeleton. The importance of robotic exoskeletons for providing walking aid to people with mobility disorders or the elderly is discussed. Furthermore, the approaches to calculating the joint torques are investigated, and the mathematical models and parameters of interest are identified. This further includes the comparative data for servo motors: robotic exoskeleton characteristics and actuator analysis in the robotic exoskeleton. The aforementioned is used to propose a mathematical model based on previous models (Zatsiorsky BSP and Dempster BSP body segment parameters models, forward kinematics models), which was extended to include added adjustable parameters such as length, area, volume, mass, density, the centre of mass, human body characteristics, and considering both static and dynamic parameter extraction. Then, an analytic method is presented, exploiting the results from the mathematical model to select the appropriate motor for each joint of the lower extremities. The detailed description of the method is followed by examples, experimental measurements, and statistical analysis of qualitative and quantitative characteristics. The results showed deviations from typical calculation methods, offering a better understanding of the motor requirements for each joint of the exoskeleton and avoiding selections of marginal functionality features of the motors. In addition, researchers are offered a tool for replicating the results of this work, allowing them to configure the parameters associated with the servo motor features. The researcher can either use the embedded library developed for this work or enter new data into it, affecting the calculated torques of the model joints. The extracted results assist the researcher in choosing the appropriate motor among commercially available brushed and brushless motors based on the torques applied at each joint in robotic articulated systems.

Cable-Driven Parallel Robots (CDPRs) use cables arranged in a parallel fashion to manipulate an end-effector (EE). They are functionally similar to several cranes that automatically collaborate in handling a shared payload. Thus, CDPRs share several types of equipment with cranes, such as winches, hoists, and pulleys. On the other hand, since CDPRs rely on model-based automatic controllers for their operations, standard crane equipment may severely limit their performance. In particular, to achieve reasonably accurate feedback control of the EE pose during the process, the length of the cable inside the workspace of the robot should be known. Cable length is usually inferred by measuring winch angular displacement, but this operation is simple and accurate only if the winch transmission ratio is constant. This problem called for the design of novel actuation schemes for CDPRs; in this paper, we analyze the existing architectures of so-called servo-winches (i.e., servo-actuators which employ a rotational motor and have a constant transmission ratio), and we propose a novel servo-winch concept and compare the state-of-the-art architectures with our design in terms of pros and cons, design requirements, and applications.

9 p.-4 fig., Current microtechnologies have shown plenty of room inside a living cell for silicon chips. Microchips as barcodes, biochemical sensors, mechanical sensors and even electrical devices have been internalized into living cells without interfering their cell viability. However, these technologies lack from the ability to trap and preconcentrate cells in a specific region, which are prerequisites for cell separation, purification and posterior studies with enhanced sensitivity. Magnetic manipulation of microobjects, which allows a non-contacting method, has become an attractive and promising technique at small scales. Here, we show intracellular Ni-based chips with magnetic capabilities to allow cell enrichment. As a proof of concept of the potential to integrate multiple functionalities on a single device of this technique, we combine coding and magnetic manipulation capabilities in a single device. Devices were found to be internalized by HeLa cells without interfering in their viability. We demonstrated the tagging of a subpopulation of cells and their subsequent magnetic trapping with internalized barcodes subjected to a force up to 2.57 pN (for magnet-cells distance of 4.9 mm). The work opens the venue for future intracellular chips that integrate multiple functionalities with the magnetic manipulation of cells., This study was financed by the Spanish Government through project MINAHE6 (TEC2017-85059-C3), MINAHE7 (PID2020-115663GB-C3) and FEDER funding. M.I.A. thanks the MCIU for the pre-doctoral Grant (BES-2015-075932) and the University of Granada for the guidance and support within the doctoral program.