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Liquid crystal elastomer is a type of soft material with unique physical and chemical properties that offer a variety of possibilities in the growing field of soft robot actuators. This type of material is able to exhibit large, revertible deformation under various external stimuli, including heat, electric or magnetic fields, light, etc., which may lead to a wide range of different applications such as bio-sensors, artificial muscles, optical devices, solar cell plants, etc. With these possibilities, it is important to establish modeling and control strategies for liquid crystal elastomer-based actuators, to obtain the accurate prediction and description of its physical dynamics. However, so far, existing studies on this type of the actuators mainly focus on material properties and fabrication, the state of art on the modeling and control of such actuators is still preliminary. To gain a better understanding on current studies of the topic from the control perspective, this review provides a brief collection on recent studies on the modeling and control of the liquid crystal elastomer-based soft robot actuator. The review will introduce the deformation mechanism of the actuator, as well as basic concepts. Existing studies on the modeling and control for the liquid crystal elastomer-based actuator will be organized and introduced to provide an overview in this field as well as future insights.

Liquid crystal elastomer (LCE) is a promising candidate for actuation in light-driven soft robot applications. Due to the fact that LCE has complex hysteretic nonlinearities, which are highly dependent on the environment, modeling of actuators made of LCE is a very challenging issue. In this article, a model is proposed to describe the deformation of the LCE actuator accurately and analytically by considering the dynamic phase transition process of LCE molecules. First, an overview of the physical process of LCE's deformation is presented, and the schematic of the LCE actuator, as well as the modeling scheme are then introduced. Next, a thermodynamic analysis of the system's free energy is performed to establish the model for the LCE actuator, which gives the relationship between the system's deformation and the temperature. Here, to describe the complex hysteretic nonlinearity in the model, the dynamic process of the phase transition of LCE molecules is exploited. To effectively identify the model parameters, a two-step parameter identification strategy based on the differential evolution algorithm and nonlinear least-squares method is utilized. Finally, experimental results verify the validity of the proposed model. This modeling provides an approach to describe LCE's deformation with high accuracy and can fully reflect the physical nature of LCE's deformation, especially hysteresis. It can be utilized as a basis for accurate control over LCE actuators in photoresponsive soft robot applications.

This article proposes a targeting posture control approach with dynamic obstacle avoidance of differential-drive wheeled mobile robot (WMR) systems in the presence of unknown skidding, slipping, input disturbances, model uncertainties, and torque saturation. First, a nonlinear model predictive control (NMPC) scheme is presented to generate a feasible trajectory from a starting posture to a targeting posture where dynamic obstacles in the environment and physical constraints of the robots are considered. Second, a robust virtual control law at the kinematic level is introduced for the robots to follow the trajectory. Third, taking the consideration of the unknown skidding, slipping, input disturbances, and model uncertainties in the dynamic model being lumped as a total disturbance, which is estimated by the linear extended state observer (LESO), a disturbance compensation-based saturation controller is designed to make the real velocity of the robot converge to the virtual velocity command. Finally, the effectiveness of the proposed control strategy is verified by simulation results.

(2S,2′S,6R,6′R)-4,4′-(6-Bromopyrido[2,3-d]pyrimidine-2,4-diyl)bis(2,6-dimethylmorpholine) is a novel organic intermediate having pyrido[2,3-d]pyrimidine. It is synthesized by four steps and confirmed by 1H and 13C NMR and FTIR spectroscopy and MS. Meanwhile, the single crystal of the title compound is subjected to the crystallographic analysis and the conformation determination. Moreover, density functional theory (DFT) is used to calculate the optimized structures of the molecule which are compared with the X-ray measurement. The result of the molecular structure optimized by DFT is consistent with the crystal structure determined by single crystal X-ray diffraction. Finally, in order to further investigate some physical properties of the title compound by the B3LYP/6-311G(2d,p) method, the molecular electrostatic potential and frontier molecular orbitals are calculated. The calculated and experimental data show that the title compound has good chemical stability and nucleophilic reactivity. Hirshfeld surface analyses can explain the atom pair contacts of the crystal and the quantitative analysis of intermolecular interactions is performed.

Tert-butyl-5-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-1H-indazole-1-carboxylate is a significant intermediate of 1H-indazole derivatives. In this paper, the title compound is acquired through two substitution reactions. The structure is corroborated by FTIR, 1H and 13C NMR spectroscopy, and MS. In the meantime, the single crystal is detected by means of X-ray diffraction, calculated by exerting density functional theory (DFT), and subjected to the crystallographic and conformational analysis. The results of comparing the DFT calculated value with the X-ray diffraction value display that the optimized molecular structure does cohere with the single crystal structure ascertained via the experiment. The 98.28% stable conformer and 1.72% unstable conformers are found in the DFT calculations. Furthermore, to reveal the physicochemical features of the title compound, the molecular electrostatic potential and frontier molecular orbitals are investigated through DFT.

The study on the stabilization of planar underactuated manipulators without gravity is well recognized as a major challenge since the system includes a second-order nonholonomic constraint when the passive link is not located at the first link. It is important to solve this difficulty for applications such as systems working in aerospace or underwater. This article presents a position control method based on bidirectional motion planning and intelligent optimization for this kind of system. The control objective is to move the end effector of the manipulator from its initial position to a given target position. The differential evolution algorithm is applied to solve the target angles of all links corresponding to the target position of the end effector. Then, bidirectional motion planning is performed, which consists of forward and backward motions. Each motion is planned by designing a trajectory for every active link based on their initial and target angles. During the forward motion, all active links except the first one are moved to their target angles, and the first active link and the passive link to the intermediate angles. For the backward motion, the first active link is moved to its target angle, the other active links remain at their target angles, and the passive link will be moved to its target angle at the same time. The planned trajectories are chosen based on the time-scaling method and differential evolution algorithm to make sure that the forward and backward planned motions can be connected smoothly. Finally, the trajectory tracking controllers for all active links are designed based on the sliding-mode control method. The proposed control method is verified on planar four-link underactuated manipulators with different passive joints. This strategy has the advantage that it works for planar underactuated manipulators with a second-order nonholonomic constraint whose passive link can be at different positions. Meanwhile, by combining intelligent optimization with bidirectional motion planning, the control process becomes simpler and more effective.

Liquid crystal elastomers (LCEs) offer promising prospect in applications such as soft robot actuators due to the fact that they can be chemically doped to have photo-responsive deformation characteristics . With the purpose of accurate control of LCE actuators in soft robot applications, the establishment of a model which quantitatively describes the deformation characteristics of LCE becomes essential. However, current models for LCE are very preliminary, which restricts the implementation of LCE actuators. This paper develops a model to describe the deformation of LCE actuators. First, the deformation process is discussed, which is in nature the macroscopic shape change corresponding to the phase change of LCE. Then, the relationship between the deformation and the temperature of LCE is established according to thermodynamic analysis on the free energy, and the phase transition process. Unknown parameters are determined through parameter identification with experimental data based on the non-linear least-squares method. This model has the advantage that it quantitatively describes the deformation characteristics of LCE without the aid of numerical simulation, and it reflects the physical nature of the deformation of LCE. This model lays a basis for the accurate control of the LCE actuators, which leads to future photo-responsive soft robot applications.

Numerous studies have clarified the importance of measuring the impact toughness of titanium alloy drill pipe, however, the influence of heat treatment parameters on the impact toughness of titanium alloy is seldom discussed. Herein, the influence of annealing temperature on notch impact toughness of Ti-6Al-4V-0.5Ni-0.5Nb alloy was investigated by Charpy impact test. Optical microscope and SEM characterized the impact specimens’ annealing microstructure and fracture surface. The results revealed that the primary α phase gradually decreases with increasing annealing temperature, and the impact toughness of the plate increases first and then decreases. The alloy fracture changes from quasi-cleavage fracture to ductile fracture, and with the temperature rising to the phase transformation point, the fracture of the alloy mainly turns into cleavage fracture.

In this paper, the microstructural evolution process and deformation mechanism of annealed Ti-5Al-2.5Sn alloy under a high strain rate of 2700 s−1 were investigated by quasi-in-situ method. The main deformation mechanism is found to be dislocation slip in the strain range from 0 to 0.05, and about 96% of the whole grain is deformed by dislocation slip, and { 1 1 ¯ 00 } < 11 2 ¯ 0 > prismatic slip dominates the plastic deformation. When the strain increased from 0.05 to 0.10, the original slip system continued to move, and 13% of the whole grain activates the new slip system. In the strain range from 0.10-0.20, the number of slip traces does not increase significantly, and the new slip system is difficult to be activated. In the whole deformation process, about 42% of whole the grain activates a variety of slip systems including { 1 1 ¯ 00 } < 11 2 ¯ 0 > prismatic slip and { 1 ¯ 101 } < 11 2 ¯ 0 > pyramidal slip which activated at the same time. Results show that { 11 2 ¯ 1 } twin only appeared in a few grains in the whole observed region, indicating that twinning is not the dominant deformation mechanism of annealed Ti-5Al-2.5Sn alloy at a high strain rate.

Dielectric Elastomer Actuator (DEA) shows the complex characteristics such as the inherent nonlinearity, intricate electromechanical coupling, time-dependent viscoelastic behavior, etc., which make...

A series of novel triazoloquinolinone and imidazoquinazolinone derivatives were designed and synthesised, and their biological activities against SHP2 protein and melanoma A357 cell line were evaluated in vitro. The results show that some target compounds have moderate to excellent inhibitory activity on SHP2 protein and melanoma A357 cell line. Structure-activity relationships (SARs) showed that both imidazoquinazolinone and triazoloquinazolinone derivatives have good SHP2 protein kinase and melanoma cell line A357 inhibitory activity. The results of molecular docking also showed that the cores of imidazoquinazolinone and triazoloquinazolinone have a certain affinity for SHP2 protein at the same time. Compared with SHP244, the target compounds have quite good liver microsomal stability and has more drug potential. The most promising compound B1 has a strong inhibitory effect on the melanoma cell line A357 at 100 µM (76.15% inhibition).

Ti-3Al-2.5V alloy was usually the α phase of HCP structure at room temperature which had obvious anisotropy. During tube rolling, α grain would be influenced by stress-strain state, deformation amount, ‘Q’ ratio to result the preferred orientation and formed texture. In order to obtain radial texture tube by rolling and improve the service quality of tube in the pipeline system, Φ25 mm Ti-3Al-2.5V alloy tubes was selected as billet for the experiment, and four kinds of tubes with outer diameter of Φ16mm was produced by single pass cold rolling with ‘Q’ ratios ranging from 0.65 to 2.0. The effect of ‘Q’ ratio on the texture of Ti-3Al-2.5V tube was studied. The result indicted that the initial texture of the tube is radial-circumferential equally distributed, and the radial basal texture enhances gradually with increasing ‘Q’ ratio. Since the angle between the C-axis of grain and the radial axis of RD decreases, the C-axis of grain distributes to the radial direction, and the more grain orientation from {112X} pyramidal to {0001} basal plane. The different ‘Q’ ratio would lead to different strain along the radial direction, circumferential direction, axial direction, thus affected the crystal orientation and distribution during tube rolling deformation. When ‘Q’ > 1, the tube mainly produced radial basal texture. By comparison with ‘Q’ < 1, the tube mainly produced circumferential basal texture. As a result, when the initial texture of the tube is radial-circumferential equally distributed, the ideal radial texture of the tube can be obtained by choosing rolling process with ‘Q’ > 2.0.

Control problem of systems actuated by the smart material based actuators are quite challenging, because of its intrinsic hysteresis nonlinear behaviors. This paper deals with such systems preceded with unknown hysteresis actuators. When the actuator with unknown hysteresis is cascaded with the uncertain dynamic system, the output of the actuators is also not measurable. Besides, such systems usually suffer from the disturbances. In this paper, the Prandtl-Ishlinskii (PI) hysteresis model is analyzed. Utilizing the properties raised, the fusion of PI model and Adaptive Robust Control (ARC) approach is provided. The proposed controller is able to deal with actuators with unknown hysteresis, uncertain system dynamics. Also, disturbances are also taken into consideration for such systems. The stability of the closed-loop system has been guaranteed and the simulation is provided to demonstrate the performance of the controller developed.

Planar underactuated mechanical systems are unaffected by gravity and therefore widely used in aerospace robots and underwater vehicles. However, the stable control is quite difficult since any position that the system can reach is its equilibrium point where it is linearly uncontrollable. In this paper, considering a planar three-link passive-active-active underactuated manipulator, a novel control approach using intelligent optimization is developed for its asymptotic stability at a target position. In the first stage, we develop controllers for stabilizing one active link at its target angle obtained by inverse kinematic method and the other two links at their transitional angles obtained by the Genetic Algorithm (GA), where the angles need to satisfy the angle constraint. Meanwhile, the GA is also utilized to optimize controllers’ parameters to ensure this stable control. Then in next stage, under the control of the angle constraint, the remaining two links are moved to the target angles simultaneously. Besides, we also improve the optimization criterion to include the control error, control time and input torque, thereby selecting better parameters of the controllers to obtain better control performance. Four simulations are implemented to prove the validity and feasibility of the proposed control and optimization algorithm.

This paper presents a new control strategy based on Fourier transformation and intelligent optimization for a planar Pendubot with a passive second link, which can be treated as a second-order nonholonomic system whose control has been an open and challenging issue. A controller acting within a time corresponding to the frequency of its fundamental harmonic term is designed to realize the system control objective, which is to move the system from its initial position to the target position. By employing Fourier transformation, a general expression of the controller composed of a constant term and harmonic terms is obtained. Next, the constant term is obtained by the angular momentum theorem, and the particle swarm optimization algorithm is employed to obtain the harmonic terms of the controller. A feedback control strategy based on a nonlinear disturbance observer is then applied to overcome the uncertainties/disturbances in the system. Finally, simulation results prove the validity of this control method.

This paper considers the problem of distributed leader-follower formation control for nonholonomic mobile robots only using local interactions among the robots. First, a distributed estimation strategy is presented for each follower robot to estimate the leader’s state. Then the dynamic equations of the formation tracking errors are formulated and a distributed formation control scheme is designed, which yields globally uniformly ultimately bounded stability for the closed-loop systems without requiring persistent excitation conditions. Finally, a simulation example demonstrates the effectiveness of the proposed approach.

Xinjiang, China is affected by geographical terrain and other factors, and is prone to lightning disasters. In order to effectively carry out lightning protection and disaster reduction work and improve defense capabilities, based on the data of lightning location monitoring in Xinjiang in 2017 and the statistics reports of the lightning disasters from 2015 to 2017, the characteristics of the cloud-to-ground (CG) lightning activities and disasters in Xinjiang were statistically analyzed. The results show that the CG lightning in Xinjiang is mainly the negative one, accounting for 79.7% of the total lightning. In 2017, the distribution of positive, negative and total the CG lightning months mainly focuses on June to August, and the main occurrence period is from 14 to 23 hours. The intensity of total the CG lightning and negative the CG lightning mainly distributes from 20 to 40 kA, and the peak value appears in 30 kA. The CG lightning intensity is mainly distributed in 30 - 70 kA. The distribution of the CG lightning density in Xinjiang is larger in the north than in the south and larger in the west than in the east. Lightning disasters mainly occur from May to August, accounting for 93.2 percent of the total, with the largest number in June. From 2005 to 2017, 44.6% of lightning accidents occurred in farming and pastoral areas, followed by civil electronic equipment damage. In addition, electrical equipment, buildings and factory equipment are damaged by lightning strikes to varying degrees.

In current work, we have firstly synthesized 4-(2-chlorobenzyl)-1-(4-hydroxy-3- ((4-hydroxypiperidin-1-yl)methyl)-5-methoxyphenyl)-[1,2,4]triazolo[4,3-a]quinazolin-5(4H)-one (1) by ring-opening, cyclization, substitution, doamine condensation and Mannich reactions. The structural properties of the title compound 1 were explored using spectroscopy (1H NMR, 13C NMR, MS and FT-IR) and X-ray crystallography method. The single-crystal structure confirmed by X-ray diffraction was consistent with the molecular structure optimized by density functional theory (DFT) calculation at B3LYP/6-311G (2d, p) level of theory. The geometrical parameters, molecular electrostatic potential (MEP) and frontier molecular orbital (FMO) analysis were performed by DFT using the B3LYP/6-311G (2d, p) method. Molecular docking has shown favorable interaction between the title compound 1 and SHP2 protein. The inhibitory activity of target compound 1 on SHP2 protein at 10 μM is better than the reference compound (SHP244).

With desirable performances of impressive actuation strain, high degree of electromechanical coupling and high mechanical compliance, dielectric elastomer (DE) materials have been widely used as intelligent actuators and intelligent sensors in the fields of soft robots. However, there are many challenges to characterize the DE materials due to their inherent nonlinearity, complicated electromechanical coupling and time-varying viscoelastic feature. Acting as actuators, most studies focused on the planar DE intelligent actuators (DEIAs). However, the studies on some other functional shapes are scarce. By investigating a conical DEIA with the material of polydimethylsiloxane, we propose a dynamic model based on the principle of the nonequilibrium thermodynamics. When implemented as sensors, most works of the DE intelligent sensors (DEISs) devote to the sensor structure design. However, the studies on the modelling of the DEIS are insufficient. A mathematical model of the DEIS is built to depict its sensing property. Because the DEIS is used to measure the displacement and force synchronously, it can serve as a soft force and displacement intelligent sensor (SFDIS). Then, we identify the parameters of the proposed models by dint of the differential evolution algorithm. The results of the model validations demonstrate the effectiveness of the proposed models.

This paper proposes a dynamic model for dielectric elastomer actuators (DEAs) based on the long-short term memory (LSTM) deep neural network. The fabrication of the DEA and the framework of the experimental platform are introduced firstly. The behaviors of the DEA are analyzed through several sets of experiments, which shows the DEA has obvious memory behavior (i.e., the hysteresis behavior and creep behavior), where the hysteresis behavior is a symmetry and rate-dependence. Considering that the traditional neural network is difficult to describe the memory property, the LSTM deep neural network is constructed as the dynamic model of the DEA. Then, such neural network is trained according to the experimental data. Finally, the comparation results of the experimental data and the model output verify the effectiveness as well as the generalization ability of the dynamic model.

With the desirable physical performances of high strain and low stiffness, a novel soft sensor based on the dielectric elastomer (DE) material shows great potential in the wearable devices and soft robots. Since the DE material has the complex nonlinear characteristics and the electromechanical coupling, most early works only devoted to the sensor structure design. However, the studies on the mathematical modeling of the DE sensor (DES) are insufficient. In this paper, a mathematical model of the soft sensor based on the DE material is built to describe its sensing property. Because the DES is used to measure the displacement and force simultaneously, it can serve as a soft force and displacement sensor (SFDS). Based on the experimental data, the differential evolution algorithm is employed to identify the undetermined parameters of the developed mathematical model of the SFDS. The result of model validation demonstrates the effectiveness of the model.

The superplastic tensile test was carried out on SP700 (Ti-4.5Al-3V-2Mo-2Fe) titanium alloy sheet at 760 °C by the method of maximum m value, and the microstructure characteristics were investigated to understand the deformation mechanism. The results indicated that the examined alloy showed an extremely fine grain size of ~1.3 μm and an excellent superplasticity with fracture elongation of up to 3000%. The grain size and the volume fraction of the β phase increased as the strain increased, accompanied by the elements’ diffusion. The β-stabilizing elements (Mo, Fe, and V) were mainly dissolved within the β phase and diffused from α to β phase furthermore during deformation. The increase in strain leads to the accumulation of dislocations, which results in the increase in the proportion of low angle grain boundaries by 15%. As the deformation process, the crystal of α grains rotated, and the texture changed, accompanied by the accumulation of dislocations. The phase boundary (α/β) sliding accommodated by dislocation slip was the predominant mechanism for SP700 alloy during superplastic deformation.

The N-(3-((1-(5-bromo-2-(pyrrolidin-1-yl)phenyl)-5-oxo-[1,2,4]triazolo[4,3-a]quinazolin- 4(5H)-yl)methyl)phenyl)-2-thiomorpholinoacetamide is a novel compound having the [ 1 , 2 , 4 ]triazolo[4,3-a]quinazolinone. It was synthesized by nine steps and confirmed by 13C NMR, 1H NMR, FT-IR and MS spectroscopies. Meanwhile, the single crystal of the title compound was subjected to crystallographic analysis and conformation determination. Moreover, density functional theory (DFT) was used to calculate the optimized structures of the molecule, which was compared with the X-ray measurement. The result of the molecular structure optimized by DFT is similar to the crystal structure determined by X-ray single crystal diffraction. In order to further investigate some physical properties of the title compound, by using the B3LYP/6-311+G(2d, p) method, molecular electrostatic potential and frontier molecular orbitals was calculated. Furthermore, the binding mode of the title compound and SHP2 protein (PDB: 6BMR ) was analyzed by molecular docking. Finally, hirshfeld surfaces analyses can explain the atom pair contacts of the crystal and the quantitative analysis of intermolecular interactions.

In current work, we have firstly synthesized 4-(2-chlorobenzyl)-1-(4‑hydroxy-3- ((4-hydroxypiperidin-1-yl)methyl)-5-methoxyphenyl)-[1,2,4]triazolo[4,3-a]quinazolin-5(4H)-one (1). The structural properties of 1 were explored using spectroscopy (1H NMR, 13C NMR, MS and FT-IR) and X-ray crystallography method. The single-crystal structure confirmed by X-ray diffraction was consistent with the molecular structure optimized by density functional theory (DFT) calculation at B3LYP/6–311 G (2d, p) level of theory. The geometrical parameters, molecular electrostatic potential (MEP) and frontier molecular orbital (FMO) analysis were performed by DFT using the B3LYP/6–311 G (2d, p) method. Molecular docking may suggest a favorable interaction between 1 and SHP2 protein. The molecular dynamics (MD) simulation results shown that there are hydrogen bonds, electrostatic interactions and Pi interactions between compound 1 and SHP2 proteins. The inhibitory activity of 1 on SHP2 protein at 10 μM is better than the reference compound (SHP244).

Achieving a precise diagnosis of the pulp status of traumatized teeth is difficult. The time to interfere through endodontic treatment for these teeth is greatly dependent on the doctor's experience. A 24-year-old male patient suffered a traumatic injury to tooth #9 that resulted in an apical root horizontal fracture 3 days before he came to the hospital. The injured tooth showed no response to pulp sensitivity testing at the first visit and was discolored 1 week later. Tooth #9 was immobilized to its adjacent teeth for 4 weeks by a composite splint. The patient was asked to make regular follow-up appointments for 72 weeks. The changes in the pulp microcirculation of tooth #9 after the injury were recorded using laser Doppler flowmetry (LDF) and a tissue oxygen monitor (OXY). The LDF was used to directly measure the pulpal blood flow, and the OXY was used to detect the tissue oxygen saturation and total hemoglobin at each appointment. Tooth #9 survived a period of pulp infarct that started at week 4 and showed complete revascularization within 10 weeks. The color of the tooth returned to normal after revascularization. The tooth responded to sensitivity testing at week 58, and radiographic examinations confirmed its hard tissue was healing. Without other clinical signs besides tooth discoloration and an absence of response to pulp sensitivity testing, the complete self-repair of pulp can be expected in teeth with pulp infarct after a horizontal root fracture, and more than 1 year of follow-up is recommended. The use of LDF combined with OXY monitoring has great value in the timely and precise reflection of changes in pulp status after dental trauma.

In this paper, taking the advantage of the properties of Prandtl-Ishlinskii (PI) hysteresis model, an adaptive controller is developed for actuators dominated by unknown hysteresis nonlinearities, which are used in the dynamic systems with the uncertain parameters, where the cascaded plant can be expressed as parameterized form. By employing the construction of the inverse PI model and the adaptive control techniques, the new controller can guarantee the stability and good tracking performance with unknown hysteresis actuator, uncertain system dynamics, and the immeasurable actuator outputs. The simulation results validate the proposed controller and illustrate the performance.

A one-stage control strategy is proposed for planar underactuated manipulators, which have a passive link not located at the first link. The control objective is to control the end-effector from an initial position to a given target position. To achieve the control objective, a general form of controllers for the active links is proposed. To ensure that the system can be stabilized at its target state, parameters of the proposed controllers are calculated using the differential evolution algorithm. Simulations on specific systems are performed to show the validity of the proposed control strategy.

This paper investigates dynamic balance optimization and control of quadruped robots with compliant/flexible joints under perturbing external forces. First, we formulate a constrained dynamic model of compliant/flexible joints for quadruped robots and a reduced-order dynamic model is developed considering the robot interaction with the environment through multiple contacts. A dynamic force distribution approach based on quadratic objective function is proposed for evaluating the optimal contact forces to cope with the external wrench, and fuzzy-based adaptive control of compliant/flexible joints for quadruped robots is proposed to suppress uncertainties in the dynamics of the robot and actuators. The dynamic surface control approaches and fuzzy learning algorithms are combined in the proposed framework. All the signals of the closed-loop system have proven to be uniformly ultimately bounded through Lyapunov synthesis. Simulation experiments were performed for a quadruped robot with compliant/flexible joints. The benefits of its tracking accuracy and robustness indicate that the proposed framework is promising for the robots with payload uncertainties and external disturbances.

Near alpha titanium alloys have been widely used in the aerospace industry owing to their high special strength, low-density and excellent corrosion resistance. Ti–3Al–2.5V is a typical near alpha titanium alloy that was usually used in the form of a tube in aircraft due to its excellent cold workability. In the present study, the microstructural evolution and detwinning behavior of cold-rolled Ti–3Al–2.5V alloy tubes during annealing were investigated. Upon annealing, the microstructure evolution strongly depends on the annealing temperature and holding time, which play important roles in the kinetics of the static recovery and recrystallization. In addition, there are two independent detwinning mechanisms involved during annealing. The first one is that detwinning occurs along the twin shear direction at grain boundaries, resulting in a shortening effect. The second one is that detwinning occurs in the center of twins, resulting in a thinning effect of twins. The understanding of the detwinning behavior and microstructural evolution during annealing helps with the tube processing and their applications in aircraft.

The fracture-behaviors of two Ti-Al-Sn-Zr-Mo-Nb-W-Si alloys with different slow-diffusing &beta, stabilizing elements (Mo, W) were investigated through in-situ tensile testing at 650 &deg, C via scanning electron microscopy. These alloys have two phases: the &alpha, phase with hcp-structure (a = 0.295 nm, c = 0.468 nm) and the &beta, phase with bcc-structure (a = 0.332 nm). Three-dimensional atom probe (3DAP) results show that Mo and W mainly dissolve in the &beta, phase, and they tend to cluster near the &alpha, /&beta, phase boundary. Adding more slow-diffusing &beta, stabilizing elements can improve the ultimate tensile strength and elongation of the alloy at 650 &deg, C. During tensile deformation at 650 &deg, C, microvoids mainly initiate at &alpha, interfaces. With increases in the contents of Mo and W, the &beta, phase content increases and the average phase size decreases, which together have excellent accommodative deformation capability and will inhibit the microvoids&rsquo, nucleation along the interface. In addition, the segregation of Mo and W near the &alpha, interface can reduce the diffusion coefficient of the interface and inhibit the growth of microvoids along the interface, which are both helpful to improve the ultimate tensile strength and plasticity.

Robot manipulator control considering parameter uncertainty and velocity estimation is address in this paper. An adaptive controller using state estimation feedback is provided in this paper, which can adapt the dynamic parameters and estimate the velocity with imprecise system model simultaneously. The stability of the proposed controller is discussed and a 2-links robot manipulator is adopted as an example to illustrate and validate the provided control scheme. In the simulation, all the observer performance, parameter adaptation, and the trajectory tracking are validated.

In this paper, a developed multi-fingered dexterous hand with flexible tactile skin is described. The dexterous hand has 5-fingers with 6-DOFs and each finger is equipped with a small harmonic drive gear and a fine high-power mini actuator. To achieve the goal of grasping with high accuracy, each fingertip is covered with the tactile array sensors for determination of the force between the finger and the grasped object. Some preliminary experiments are conducted to illustrate the performance of the grasping of the developed dexterous hand.

A facile, moderate, and environment-friendly method for in-situ preparation of SnO 2 /graphene nanocomposites (SnO 2 /GNs) was proposed. The structures and morphology as well as electrochemical behaviors of SnO 2 /GNs with varied proportions of SnO 2 and graphene were characterized by X-ray diffraction, Fourier transform infrared spectrometry, transmission electron microscopy and relevant electrochemical property tests. The results reveal that the ratios of SnO 2 to graphene have a significant effect on the structures and properties of SnO 2 /GNs. SnO 2 /GN-50 containing 50% SnO 2 delivers a high specific capacity of 540 mAh g −1 even after 90 cycles at a current density of 100 mA g −1 , which is attributed to the synergistic effect of a unique combination of SnO 2 nanoparticles and graphene sheets, indicating that SnO 2 /GNs might have a promising future as anode material in Li-ion batteries.

In this paper, adaptive fuzzy-based motion generation and control are investigated for nonholonomic mobile manipulators with an under-actuated dyanmics model, in the presence of parametric and functional uncertainties. It is well known that the constraints of this kind of system consist of kinematic constraints for the mobile platform and dynamic constraints for the under-actuated manipulator with a passive joint. Through using dynamic coupling property of nonholonomic mobile manipulators, we can decouple the dynamics into a fully actuated subsystem and an unactuated subsystem. Then adaptive control is employed for the fully actuated subsystem using fuzzy logic approximation. Since the non-actuated subsystem cannot be directly manipulated by torque inputs but can be indirectly affected by the motion of the actuated subsystem, the reference trajectory of the actuated subsystem is planned by the fuzzy logic system based motion generator. Rigorous theoretic analysis has been established to show that the proposed trajectory generation and control are able to achieve dynamic stability, motion tracking and optimized dynamics. Simulation studies have further validated the efficiency of the developed scheme.

In this paper, adaptive control is proposed for hybrid position/force synchronization of master-slave teleoperation systems with time-varying delays in communication channels. Different from previous works on bilateral teleoperation systems, we investigate position/force control of bilateral teleoperation systems subject to time-varying delays and dynamical uncertainties. Using partial feedback linearization, the dynamics of both master and slave are transformed into two subsystems: local master/slave position/force control with unmodeled dynamics and delayed position/force synchronization. An adaptive control is proposed to deal with the dynamical uncertainties and robust against time delays, which guarantees the position/force synchronization trajectories converge to the desired manifolds with prescribed performance. The stability of the closed-loop system and the boundedness of synchronization tracking errors are proved using linear matrix inequalities based on Lyapunov stability synthesis. The position/force tracking error up to an ultimately bounded error is achieved. The proposed adaptive controls are robust against relative motion disturbances, parametric uncertainties, and time delays, and are validated by experimental studies.