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Electroadhesive grippers can be used to pick up a wide range of materials, and those with variable stiffness functionality can increase load capacity and strength. This paper proposes an electroadhesive gripper (VSEAF) with variable stiffness function and a simple construction based on low melting point alloys (LMPAs) with active form adaptation through pneumatic driving. Resistance wires provide active changing stiffness. For a case study, a three-fingered gripper was designed with three electroadhesive fingers of varied stiffness. It is envisaged that these electroadhesive grippers with variable stiffness would extend the preparation process and boost the use of electroadhesion in soft robot applications. [ABSTRACT FROM AUTHOR]

A gripper is a robot end effector that performs the "grasping" function. Primarily, stiff and soft conventional grippers are differentiated. Compared to typical rigid grippers, soft grippers provide more flexibility, the ability to grasp complicated curved surfaces, and the capacity to move delicate objects; nevertheless, their preparation technique is challenging and their fabrication is laborious. With the evolution of multi-material 3D printing technology, multi-material 3D printers are able to manufacture an endless number of material combinations with a simple preparation technique and high precision, and are widely used in the medical equipment, aerospace, and other sectors. This study shows a totally 3D-printed flexible gripper consisting of a flexible electroadhesion (EA) pad, a bio-inspired spiral spring, and an EA fixture in an attempt to solve the limitations of current methods for producing flexible electrodes and soft grippers. For the production of flexible EA pads, two kinds of conductive and non-conductive polylactic acid (PLA) materials are utilized; polylactic acid and thermoplastic polyurethanes (TPU) materials are used for the production of an EA fixture and an adaptable gripper. The breakdown voltage, shear and normal EA forces of flexible EA pads were evaluated, as well as the optimal size configuration was determined. The breakdown voltage, shear force, and normal EA force of the flexible EA pad were evaluated, and the optimal size configuration was determined. The optimal size configuration is rectangular comb electrode 1, with an electrode width of 4 mm, electrode spacing of 4 mm, and a duty cycle of 0.50. Under the optimal size configuration, the breakdown voltage, shear force, and normal EA force are 4.8KV, 1.192 ± 0.006 N, and 0.049 N, respectively; a fixture based on biomimetic spiral springs and TPU fingers was designed and manufactured, and employed as a fixture for flexible EA pads. A novel type of bubble artificial muscle actuator was employed as the driving device for the flexible fixture; finally, the fixture gripped a 215.2 g object (130 mm × 60 mm × 95 mm) in the combined action of EA force and mechanical clamping force. It is hoped that these flexible grippers would broaden the usage of preparation technology and electroadhesion in soft robots. [Display omitted] [ABSTRACT FROM AUTHOR]

Soft robot arms possess such characteristics as light weight, simple structure and good adaptability to the environment, among others. On the other hand, robust control of soft robot arms presents many difficulties. Based on these reasons, this paper presents a novel design and modeling of a fuzzy active disturbance rejection control (FADRC) controller for a soft PAM arm. The soft arm comprises three contractile and one extensor PAMs, which can vary its stiffness independently of its position in space. Force analysis for the soft arm is conducted, and stiffness model of the arm is established based on the relational model of contractile and extensor PAM. The accuracy of stiffness model for the soft arm was verified through experiments. Associated to this, a controller based on the fuzzy adaptive theory and active disturbance rejection control (ADRC), FADRC, has been designed to control the arm. The fuzzy adaptive theory is used to adjust the parameters of the ADRC, the control algorithm has the ability to control stiffness and position of the soft arm. In this paper, FADRC was further verified through comparative experiments on the soft arm. This paper reinforces the hypothesis that FADRC control, as an algorithm, indeed possesses good robustness and adaptive abilities. [ABSTRACT FROM AUTHOR]

A 3-DOF bionic elbow joint actuated by Pneumatic artificial muscle (PAM) was designed in this paper, and its inverse kinematics model was also established. Then, based on the Model-free adaptive control (MFAC) theory and the effects of control parameters to the control system, a Parameter self-adjust Model-free adaptive control (PSA-MFAC) strategy was proposed, and its adaptability for different control objects was also tested in simulation environment. Combined with the inverse kinematics model, motion control experiments of the bionic elbow joint were conducted in semi-physical platform. Compared with conventional MFAC and PID control algorithm, the experiment results strongly verified the improvement of PSA-MFAC control accuracy. The tracking accuracy of conventional MFAC and PID controller were 9.5 % and 15 %, respectively, in contrast, the PSA-MFAC controller was only 3.8 %. Moreover, complex dynamics modelling of the elbow joint and adjusting process of control parameters were neglected in PSA-MFAC control system. [ABSTRACT FROM AUTHOR]

Electroadhesion is a promising adhesion mechanism widely employed in robotics with advantages including enhanced adaptability, gentle/flexible handling, reduced complexity, and ultralow energy consumption. Currently, all electroadhesion pads are manually fabricated, which limits their applications. In contrast, new, easy-to-implement, cost-effective, and entirely 3D printed flexible electroadhesion pads made of both non-conductive polylactide and graphene conductive polylactide are presented in this paper. Moreover, their statics model for geometric dimensions and flexibility is established via the pseudo rigid body model. Then, normal electroadhesion force measurements and electrostatic simulation of the flexible electroadhesive pads are conducted. Finally, a 3D printed curvature adjustable gripper based on flexible electroadhesive pads that can actively grasp flat, concave, and convex objects is presented. These FEPs are expected to widen the preparation technology and increase the use of electroadhesion in soft robots application. This paper presents easy-to-implement, cost-effective, and fully 3D printed flexible electroadhesion pads (FEPs) made of both non-conductive polylactide and graphene conductive polylactide, and a fully 3D printed curvature adjustable gripper based on FEPs has been also presented, and which can actively grasp flat, concave and convex objects. [Display omitted] • New, easy-to-implement, and cost-effective fully 3D printed flexible electroadhesion pads made of both non-conductive PLA and graphene conductive PLA have be designed. • Pseudo rigid body model used to establish the statics model of geometric dimensions and the flexibility. • Normal electroadhesion force measurements are conducted on electroadhesion pads with different radius of curvature. [ABSTRACT FROM AUTHOR]

McKibben muscles have been shown to have improved stiffness characteristics when operating hydraulically. However when operating pneumatically, they are compliant and so have potential for safer physical human–robot interaction. This paper presents a method for rapidly switching between pneumatic and hydraulic modes of operation without the need to remove all hydraulic fluid from the actuator. A compliant and potentially safe pneumatic mode is demonstrated and compared with a much stiffer hydraulic mode. The paper also explores a combined pneumatic/hydraulic mode of operation which allows both the position of the joint and the speed at which it reacts to a disturbance force to be controlled. [ABSTRACT FROM AUTHOR]

Thermal conductivity is a fundamental material parameter involved in various infrastructure design guides around the world. This paper developed an innovative neural network (NN) aided homogenization approach for predicting the effective thermal conductivity of various composite construction materials. The 2-D meso-structures of dense graded asphalt mixture, porous asphalt mixture, and cement concrete were generated and divided into 2n × 2n square elements with specific thermal conductivity values. A two-layer feed-forward neural network with sigmoid hidden neurons and linear output neurons was built to predict the effective thermal conductivity of the 2 × 2 block. The Levenberg-Marquardt backpropagation algorithm was used to train the network. By repeatedly using the neural network, the effective thermal conductivities of 2-D meso-structures were calculated. The accuracy of the above NN aided homogenization approach was validated with experiment, and various factors affecting the effective thermal conductivity were analyzed. The analysis results show that the accuracy of the NN aided approach is acceptable with relative errors of 1.92~4.34% for the dense graded asphalt mixture, 1.10~6.85% for the porous asphalt mixture, and 1.13~3.14% for the cement concrete. The relative errors for all the materials are lower than 5% when the heterogeneous structures are divided into 512 × 512 elements. Ignoring the actual material meso-structures may lead to significant errors (134.01%) in predicting the effective thermal conductivity of materials with high heterogeneity such as porous asphalt mixture. While proper simplification is acceptable for dense construction composite materials. The effective thermal conductivity of composite cement-asphalt mixtures increases with higher saturation of grouted material. However, the improvement effect of the high-conductive cement paste on the composite cement-asphalt mixtures could be significantly reduced when the cement paste concentrates at the bottom of the mixture. Cracked aggregates and segregation of material components tend to decrease the effective thermal conductivity of construction materials. The NN aided homogenization approach presented in this paper is useful for selecting the effective thermal conductivity of construction materials. [ABSTRACT FROM AUTHOR]

Electroadhesion is a promising adhesion mechanism for robotics and material handling applications with advantages over existing technologies including enhanced adaptability, gentle/flexible handling, reduced complexity, and ultra-low energy consumption. Current electroadhesive (EA) grippers, however, require extra components and their associated electronics to make them sensorially capable. In addition, current planar EA grippers have difficulty adhering to non-planar surfaces and picking up non-flat objects. We present a monolithic, shape-adaptive, and self-sensing EA composite with integral dielectric elastomer actuation (DEA). This new EA-DEA composite gripper is not only proprioceptive (it can sense internal deformations) and exteroceptive (it can sense and differentiate between surfaces that it touches) but can also actively morph and adapt to curved surfaces. By integrating a high voltage self-sensing unit with the EA-DEA composite, coupled gripping and sensing capabilities can be achieved. This is because combined actions of membrane deformations by the Maxwell force and surface attraction by the EA force can be obtained by using only one voltage source due to the employment of a dual-mode parallel-and-coplanar electrode pattern. The proposed approach has the potential to significantly improve the intelligence of EA gripping technologies and increase their use in intelligent material sorting, grasping, and manipulation applications. [ABSTRACT FROM AUTHOR]

Smart fabrics offer the potential for a new generation of soft robotics and wearable technologies through the fusion of smart materials, textiles and electrical circuitries. Conductive and stretchable textiles have inherent compliance and low resistance that are suitable for driving artificial muscle actuators and are potentially safer electrode materials for soft actuation technologies. We demonstrate how soft electroactive actuating structures can be designed and fabricated from conducting textiles. We first quantitatively analyse a range of stretchable conductive textiles for dielectric elastomer actuators (DEAs). We found that conductive-knit textiles are more suitable for unidirectional DEA applications due to the largest difference (150%) in principle strain axes, whereas isotropic textiles are more suited to bidirectional DEA applications due to the smallest (11.1%) principle strain difference. Finally, we demonstrate controllable breathability through a planar e-textile DEA-driven skin and show thermal regulation in a wearable prototype that exploits soft actuation and kirigami. [ABSTRACT FROM AUTHOR]

This paper proposes a new type of circular ring traveling wave linear ultrasonic motor with incomplete teeth. The motor's movable slider is pressed against the end face of the tooth structure on the outer surface of the circular ring vibrator under a certain pre-pressure, four piezoelectric ceramic plates are evenly distributed at 90° intervals on the inner side of the circular structure, and four sets of driving teeth are arranged at 45° intervals from the position of the piezoelectric ceramic plates.When the motor is in operation, only one driving tooth works, and the life of the ultrasonic motor can be increased by rotating the different working teeth. The motor operates in two in-plane third-order bending modes that are orthogonal to each other at the same frequency. The dynamic design and simulation of the vibrator was carried out using ANSYS finite element software to analyze the effect of the structure on the mode. The principle prototype was fabricated, and the operating mode of the vibrator was measured using a laser Doppler vibrometer (LDV), and the vibration characteristics and output performance of the prototype were tested. Experimental results show that the motor runs smoothly at the excitation voltage of 240 V peak-to-peak, the excitation frequency of 30.459 kHz and the pre-pressure of 0.6 N, with the maximum output force of 90 mN and the motor no-load speed of 102 mm/s. [ABSTRACT FROM AUTHOR]

A new, optimal thermal-based adaptive frequency control (OTC) for a bidirectional DC–DC converter with full-range zero-voltage switching (ZVS) is presented in this paper. The proposed OTC achieves ZVS for a bidirectional DC–DC converter without any zero-crossing detection (ZCD) circuit or current sensor. In order to ensure a ZVS over a wide voltage and load range, the optimal switching frequency was adjusted by detecting and tracking the lowest junction temperature of the semiconductor device. Because the proposed OTC does not need a ZCD circuit, the complexity of the circuit and the susceptibility of the sampling noise are reduced. Additionally, compared with the expensive current sensor, the proposed method of temperature detection by the NTC thermistor decreases the cost. In addition, the proposed OTC does not need accurate circuit parameters and voltage or current sampling results, so the dependence on the parameters is reduced. Moreover, the temperature of the switch is directly monitored in the proposed OTC, which can effectively protect the device. A prototype with 16–32 V input and 48 V output was built, and the experiment results prove the effectiveness and feasibility of it. [ABSTRACT FROM AUTHOR]

The quick estimation and prediction of lithium-ion batteries' (LIBs) state of charge (SoC) are attracting growing attention, since the LIB has become one of the most essential power sources for daily consumer electronics. Most deep learning methods require plenty of data and more than two LIB parameters to train the model for predicting SoC. In this paper, a single-parameter SoC prediction based on deep learning is realized by cleaning the data for lithium-ion battery parameters and constructing the feature matrix based on the cleaned data. Then, by analyzing the feature matrix's periodicity and principal component to obtain two kinds of the original eigenmatrix's substitution matrices, the two substitutions are fused to obtain an excellent prediction effect. In the end, the minimization method is verified with newly measured lithium battery data, and the results show that the MAPE of the SoC prediction reaches 0.96%, the input data are reduced by 93.33%, and the training time is reduced by 96.68%. Fast and accurate prediction of the SoC is achieved by using only a minimum amount of voltage data. [ABSTRACT FROM AUTHOR]

This article investigates the problem of model-free tracking control for a class of continuum manipulators. A new type of robust control strategy is provided to address the problem, which primarily consists of two parts. First, to achieve output tracking with the desired accuracy, an error transformation scheme is constructed. Moreover, because of the robustness of the error transformation scheme against model uncertainties, no knowledge of the manipulator model is required, leading to a model-free control solution. Then, a tuning function is used to modify certain error variables to relax the requirements on the initial conditions of the error transformation scheme. In this way, the global stability of the closed-loop system can be guaranteed. Finally, both simulation and experimental results validate the expected performance of the presented control method. [ABSTRACT FROM AUTHOR]

The safety and reliability of inverters play a significant role in stable power electronic system operations. Considering a railway vehicle air-conditioning inverter as a case study, this paper presents a generic open-circuit fault diagnosis method that can be applied to various inverter and control schemes. First, a detailed model of three-phase output currents under both normal and fault status is derived, and then the concept of space trajectory is introduced based on the three-phase output currents. The open-circuit faults of the inverter lead to output phase current distortion. Therefore, different types of faults have different space trajectories, and the corresponding shape of the space trajectory is considered to be a fault feature. Then, the fault is located by the direction vector and center-of-mass coordinate. The effectiveness and reliability of the diagnosis method are verified and analyzed using a hardware-in-the-loop test platform. [ABSTRACT FROM AUTHOR]

Background: During the process of cell micro operation, the contact force between the entry needle and the cell membrane is usually a very small area to be tested.Objective: These two features have been utilized to design a high precision micro force sensor to provide a force feedback in the process of cell micro operation.Methods: However, PVDF (Polyvinylidene Fluoride) has continued to display both a wide range of frequency response and a highly sensitive transform between force and electricity. In this paper a charge signal is obtained. In order to transform the charge signal into a voltage signal, a signal processing circuit was designed. The data acquisition card PCI-6221 (National Instruments) was used. It was employed to collect the voltage signal.Results: The resultant micro force sensor was calibrated by using a rating test.Conclusions: The experimental test results demonstrated that the sensitivity and linearity of the designed micro force sensor were higher than the sensitivity and linearity of a traditional piezoelectric sensor. [ABSTRACT FROM AUTHOR]

Continuous monitoring of human physiological signals is critical to managing personal healthcare by early detection of health disorders. Wearable and implantable devices are attracting growing attention as they show great potential for real‐time recording of physiological conditions and body motions. Conventional piezoelectric sensors have the advantage of potentially being self‐powered, but have limitations due to their intrinsic lack of stretchability. Herein, a kirigami approach to realize a novel stretchable strain sensor is introduced through a network of cut patterns in a piezoelectric thin film, exploiting the anisotropic and local bending that the patterns induce. The resulting pattern simultaneously enhances the electrical performance of the film and its stretchability while retaining the mechanical integrity of the underlying materials. The power output is enhanced from the mechano‐electric piezoelectric sensing effect by introducing an intersegment, through‐plane, electrode pattern. By additionally integrating wireless electronics, this sensing network could work in an entirely battery‐free mode. The kirigami stretchable piezoelectric sensor is demonstrated in cardiac monitoring and wearable body tracking applications. The integrated soft, stretchable, and biocompatible sensor demonstrates excellent in vitro and ex vivo performances and provides insights for the potential use in myriad biomedical and wearable health monitoring applications. [ABSTRACT FROM AUTHOR]