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We proposed and developed a small bionic amphibious spherical robot system for tasks such as coastal environment monitoring and offshore autonomous search and rescue. Our third-generation bionic small amphibious spherical robots have many disadvantages, such as the lack of maneuverability and a small operating range. It is difficult to accomplish underwater autonomous motion control with these robots. Therefore, we proposed a fourth-generation amphibious spherical robot. However, the amphibious spherical robot developed in this project has a small and compact design, with limited sensors and external sensing options. This means that the robot has weak external information collection capabilities. We need to make the real time operation of the robot’s underwater motion control system more reliable. In this paper, we mainly used a fuzzy Proportional-Integral-Derivative (PID) control algorithm to design an underwater motion control system for a novel robot. Moreover, we compared PID with fuzzy PID control methods by carrying out experiments on heading and turning bow motions to verify that the fuzzy PID is more robust and exhibits good dynamic performance. We also carried out experiments on the three-dimensional (3D) motion control to validate the design of the underwater motion control system.

The Q × ƒ values of SmNbO4 ceramics had been effectively optimized by MgO doping, and a series of high-Q SmNbO4-x MgO (0.5 ≤ x ≤ 4.0) ceramics had been successfully prepared with conventional solid reaction process. The phase composition, microstructure and microwave dielectric properties had been investigated with different content of MgO addition. Two phases, surrounded by each other which indexed as SmNbO4 and MgO, had been detected in SmNbO4-x MgO ceramics. It was found that the grain growth of SmNbO4-x MgO ceramics could be well promoted by MgO additive, owing to the similar c/a values between the two crystal structures. Based on the structural characteristic of SmNbO4-x MgO ceramics, the variation in dielectric constant of SmNbO4-x MgO ceramics was verified to satisfy with the Lichtenecker logarithmic mixing rule. Importantly, the Q × ƒ values of SmNbO4-x MgO ceramics increased as a function of MgO content, which was analyzed to result from the improved microstructure.

Lithium–sulfur (Li–S) batteries are considered as a next-generation energy storage solution thanks to the dramatic increase in their energy density and the accompanying low fabrication cost. Nonetheless, their practical applications have been hampered by critical challenges such as cycling instability, low sulfur utilisation and efficiency. Here, the interfacial growth of Ni(OH)2-encapsulated sulfur nanoparticles in a reduced graphene oxide free-standing matrix as Li–S cathodes has been highlighted, along with a detailed application investigation of the sandwich foam structure in Li–S batteries. Compared to sulfur composites based solely on a graphene host (S@rGO), this composite foam cathode could provide significant improvements in specific capacity and long-cycle stability with the effective confinement and promoted conversion of lithium polysulfides. Moreover, the sandwich foam composite cathode exhibits a high specific capacity of 1189 mA h g−1 (0.1 C), better rating performance (691 mA h g−1 at 2 C) and remarkable cycling stability, retaining 81% of the initial capacity after 200 cycles of charge–discharge at 0.2 C. Furthermore, Ni(OH)2 wrapping at the cathode–electrolyte interface offers vastly improved polysulfide shuttle suppression, which provides a new cathode encapsulation method for further developments of advanced Li–S cathodes.

This paper designs a novel legged, multi-vectored water-jet composite driving mechanism (LMWCDM) for the amphibious spherical robot (ASRobot) and presents modeling and experimental evaluation of this composite driving mechanism. In order to crawl on land flexibly, the robot was designed in SolidWorks and simulated in ADAMS environment with the sit to stand motion and a crawling gait. Then the simulation results, such as driving torques, guided the selection of servomotors in different joints. In aquatic environment, the dynamic modeling of ASRobot was analyzed by synthesizing the propulsive vectors of four propellers in each workspace of legs. Simplistically, multiple underwater locomotion, such as longitudinal and lateral motion, rotary motion, sinking and floating motion and cruising motion, were proposed. Thus, using a six-axis force/torque sensor at the equivalent mass center, a force and torque measuring mechanism was developed to obtain the direct propulsive effect and validate the modeling of the driving system. To evaluate the robot design and selection of servomotors, experiments of the sit to stand motion and crawling motion were conducted. Underwater testing experiments of LMWCDM were carried out to verify the modeling of rotary motion, sinking and floating motion. Besides, underwater test of the robot prototype also proved the highly flexible and swift motion.

In the narrow, submarine, unstructured environment, the present localization approaches, such as GPS measurement, dead-reckoning, acoustic positioning, artificial landmarks-based method, are hard to be used for multiple small-scale underwater robots. Therefore, this paper proposes a novel RGB-D camera and Inertial Measurement Unit (IMU) fusion-based cooperative and relative close-range localization approach for special environments, such as underwater caves. Owing to the rotation movement with zero-radius, the cooperative localization of Multiple Turtle-inspired Amphibious Spherical Robot (MTASRs) is realized. Firstly, we present an efficient Histogram of Oriented Gradient (HOG) and Color Names (CNs) fusion feature extracted from color images of TASRs. Then, by training Support Vector Machine (SVM) classifier with this fusion feature, an automatic recognition method of TASRs is developed. Secondly, RGB-D camera-based measurement model is obtained by the depth map. In order to realize the cooperative and relative close-range localization of MTASRs, the MTASRs model is established with RGB-D camera and IMU. Finally, the depth measurement in water is corrected and the efficiency of RGB-D camera for underwater application is validated. Then experiments of our proposed localization method with three robots were conducted and the results verified the feasibility of the proposed method for MTASRs.

In order to complete tasks efficiently, multiple robots are usually required to cooperate with each other. This leads to many requirements for the control strategy of multiple robots. In response to these needs, an edge-based event-driven consensus formation control strategy is proposed in this paper. The proposed formation control strategy merges virtual linkage formation control algorithm, edge-based event-driven consensus control algorithm and artificial potential field algorithm together. The virtual linkage formation control algorithm mainly controls the formation of multiple robot formations. The edge-based event-driven consistency control strategy is used to maintain the formation of multiple robots and increase energy utilization. The artificial potential field method is used to ensure the safe distance of each robot. The simulation experiment results prove that the proposed formation control strategy can realize the formation of multiple robots.

This paper presents a novel multi-binocular camera based localization method with panoramic view and high precision for amphibious spherical robots. In our previous work, the proposed approach based on RGB-D camera and inertial measurement unit (IMU) realized a cooperative and relatively close-range localization. While, position drifts caused by the rotation movement and short positioning range of RGB-D camera in underwater environments are the drawbacks of the previous approach. This paper designs a multi-binocular camera system on the amphibious spherical robot, which makes the robot observe targets in a nearly 360-degree visual range without rotation movement. Meanwhile, through the stereo vision model, the robot obtains the position information about the target robot. Then, according to the position information and the relative position of the binocular cameras, the cooperative localization model is established. To validate the proposed approach, experiments were performed in gazebo simulator with varying distances and relative degree. Compared with the previous works, the proposed localization method reveals higher accuracy and robustness.

In order to realize the underwater functions of amphibious spherical robots and complete the task in water, a multi-robot cooperative hunting strategy is proposed. With the global observation of the quadrotor, the robots and the target can be found, which meets the conditions for modeling a composite system. In the target hunting process, multiple robots converge uniformly when they are hunting target, and they form a triangle formation. The cost function evaluates the hunting efficiency and energy consumption of the hunting strategy. Finally, the optimal path of each amphibious spherical robot was calculated. The simulation results show the effectiveness of this target hunting method based on ROS/Gazebo simulation platform.

It is difficult for a rigid formation composed of multiple robots to pass through a narrow waterway, which needs to be realized by formation reshape. The virtual linkage structure is used to solve the problem that the conventional virtual structure is not easy to deform. In order to ensure the robustness of formation control, a discrete information consistency algorithm is added to provide the desire trajectory, then controller will be used to track it. At the same time, due to the difficulty of hydrodynamic modeling and the large overshoot of PID (proportional integral differential) controller, the double loop controller based on ADRC (Auto Disturbance Rejection Controller) include position loop and speed loop is used to adjust the position, and the single loop controller is used to adjust the heading angle and depth. The results of simulation show that the three combined methods of 3D virtual linkage structure, discrete consensus and ADRC realize the formation reshape.

The underwater environment is complex and diverse, and it is difficult to explore the ocean, especially in the deep sea area. The lack of light, high pressure, and lack of oxygen make it difficult for humans to work in such extreme environments. Therefore, people are beginning to hand over the burden of exploring the ocean to underwater robots. The underwater robot's perception of the underwater environment is very important for controlling the motion of the underwater robot. However, in the environment where the light is lacking at night and in the deep sea, and in the narrow space, the robot vision consisting of infrared and camera is traditionally used. The system is difficult to function, so a new sensing system is needed to assist the underwater robot in recognizing the surrounding environment. In nature, real fish use their lateral line system to sense the surrounding environment. Based on the principle of bionics, we have developed an artificial lateral line system on a bionic spherical robot. The basic principle of this artificial lateral line system is to use the pressure sensor to sense the water flow pressure around the robot when the robot swims under water, thus establishing a relationship model between the robot swimming speed and the water flow pressure to realize the relative speed of identifying the underwater robot and the water flow.

Remote-controlled vascular interventional robots (RVIRs) are being developed to reduce the occupational risk of the intervening physician, such as radiation, chronic neck and back pain, and increase the accuracy and stability of surgery operation. The collision between the catheter/guidewire tip and blood vessels during the surgery practice is important for minimally invasive surgery because the success of the surgery mainly depends on the detection of collisions. In this study, we propose a novel sensing principle and fabricate a sensorized RVIR. The proposed sensorized RVIR can accurately detect force and reconstruct force feedback. The performance of the proposed sensorized RVIR is evaluated through experiments. The experiment results show that it can accurately measure static force and time-varying force. Subtle force changes caused by changes of movement direction in surgeries can also be detected. In addition, the proposed sensorized RVIR has higher operation efficiency than our previous prototype.

Borides of chromium, molybdenum, and tungsten are an attractive class of transition-metal light-element compounds with superior mechanical properties. Here, we explore in detail the binary X2B with I4∕m and I4∕mcm symmetry, XB with 141/amd and Cmcm symmetry as well as XB2 with P6∕mmm and P63∕mmc (X = Cr, Mo, W) systems by first principles calculations, especially their mechanical properties under uniaxial strains along the c axis. We report the calculated ideal tensile strength for each structure, which is the minimum stress required to break the material. The elastic constants, bulk modulus, shear modulus, and Young's modulus are calculated at equilibrium and uniaxial strains. For the same structure, W B compounds are more ductile than Cr-B and Mo-B because of their high B∕G ratio, while they fail to possess high hardness at the same time. The structures belong to space group P63∕mmc have the largest hardness, followed by 141-XB. Although with the highest boron content, hardness values for 191-XB2 are much lower than 194-XB2 phases with the same composition. The anisotropy of X-B systems has also been studied, which is rare in previous reports. The underlying mechanism for the high elastic modulus and hardness of X B systems is further discussed by the analysis of electronic density of states.

New ceramics with CoZrTa2O8 formula were prepared by conventional solid-state reaction method. The phase composition of all sintered samples was confirmed as a single phase with monoclinic wolframite structure belonged to the P2/c space group. The grain growth was analyzed through the investigation of relative density and grain size. The dielectric constant (er) was discussed with relative density, polarizability and porosity. The quality factors (Q × f) were analyzed by considering grain growth and atomic packing fraction. The temperature coefficient of resonant frequency (τƒ) had no significant change under different sintering temperature. The typical microwave dielectric properties of CoZrTa2O8 ceramics were er = 23.54, Q × f = 20,100 GHz, and τƒ = −8.72 ppm/°C, sintered at 1250 °C for 4 h. Considering the low dielectric loss and near-zero τƒ value, CoZrTa2O8 ceramics should be good candidates for microwave device application.

This paper describes an improved three-dimensional (3D)-printed, low-cost, multi-functional, high-maneuverability, high-concealment, turtle-inspired mobile amphibious spherical robot for environmental monitoring and data collection. The major challenge in developing such a robot lies in its limited physical size and compact structure that allows for only one type of propulsion system to be used both on land and in water. This paper focuses on the optimization of the kinematic and hydrodynamic model of the amphibious spherical robot, so as to improve the control accuracy and stability of the robot. In order to optimize some kinematic and dynamic modeling parameters of the robot, such as the drag coefficient of robot, the angular velocity and swing angle of each joint, a solid model of the 3D-printed robot was built by SolidWorks. Our simulation results and theoretical calculations confirmed the validity of the virtual model and facilitated identification of key parameters in the design. The correctness of the modeling was demonstrated by the stability of consecutive crawling and underwater movements, providing a basis for driving and controlling methods for this amphibious robot, as well as guidance for the robot's gait trajectory. Combining the robot's crawling mechanism with related simulation results, an optimized prototype of the 3D-printed amphibious spherical robot was constructed. A series of crawling experiments on a common floor were performed with the improved robot prototype, which was also done using the previous robot. The results were evaluated by a novel optical positioning system, NDI Polaris. Moreover, several experiments were carried on land crawling and underwater swimming to verify the performance of the improved amphibious spherical robot. Comparison of experimental and simulation results demonstrated the improved robot had better amphibious motion performance, as well as more potentiality and applicability to the real structures.

New microwave dielectric ceramics Mg2CeNbO6.5 were synthesized by solid-state method. The phase, crystal structure, micro-structures and microwave dielectric properties of Mg2CeNbO6.5 ceramics had been investigated in the sintering temperature range of 1225–1325 °C. Two phases were detected by the X-ray diffraction patterns, including the main crystalline phase of CeO2 and the second phase of Mg4Nb2O9. Well-developed microstructures of the well-dense samples were obtained for samples sintered at 1225–1325 °C. As sintering temperature increased, the τf values were stable, however, the significant change in the ɛr values and Q × f values were observed. At 1275 °C, the obtained Mg2CeNbO6.5 ceramics had promising excellent microwave dielectric properties: er = 15.38, Q × f = 17,300 GHz and τf = − 49.71 ppm/°C.

First-principles calculations have been performed to study the structural, elastic, electronic and lattice dynamical properties of Ba 2 InTaO 6 and Ba 2 InNbO 6 double perovskites under hydrostatic pressure. Pressure-induced enhancements of elastic constants, elastic moduli, elastic wave velocities, as well as Debye temperature are observed, without any softening behaviors. Both Ba 2 InTaO 6 and Ba 2 InNbO 6 have a quasi-direct band-gap character at zero pressure, and their fundamental energy gaps vary nonlinearly with increasing pressure. Moreover, the evolution of Roman-active and infrared-active optical phonon frequencies with pressure is analyzed. A pressure-induced softness of low-frequency T 1 g silent modes around the Γ point suggests that Ba 2 InTaO 6 and Ba 2 InNbO 6 becomes dynamically instable beyond a certain critical pressure.

Microwave dielectric ceramics CuO–modified MgZrTa2O8 were synthesized by the conventional solid-state reaction method. The effects of CuO additives on the sintering characteristics and microwave dielectric properties have been investigated. With CuO addition, the sintering temperature of MgZrTa2O8 ceramics can be effectively lowered from 1475 to 1375 °C without decreasing its dielectric properties obviously and the temperature coefficient of the resonant frequency of MgZrTa2O8 ceramics have been optimized to near-zero. The crystalline phase exhibited a wolframite crystal structure and no second phase was detected at low addition levels. The grain growth of CuO–modified MgZrTa2O8 ceramics was accelerated due to liquid phase effect. The relative dielectric constants (er) were correlated with apparent density and were not significantly different for all levels of CuO concentration. The quality factors (Q × ƒ) and temperature coefficient of resonant frequency (τƒ), which were strongly dependent on the CuO concentration, were analyzed by the grain size and the dielectric constant respectively. A best Q × ƒ value of 116400 GHz and τƒ value of −6.19 ppm/℃ were obtained for specimen with 0.05 wt% CuO addition at 1375 °C.

New low-loss NiZrTa2O8 ceramics were prepared by conventional mixed-oxide method with the crystal structure and microwave dielectric properties being investigated. The phase composition of NiZrTa2O8 ceramics presented two-phase coexistence, indexed as NiTiNb2O8 and Ni0.5Ti0.5NbO4. The apparent morphology and grain size were analyzed as a function of sintering temperature. The dielectric constant (er) which changed from 19.02 to 21.38, was mainly dependent on the densities and phase composition. The quality factor (Q × ƒ) was dominated by grain size. In this paper, the optimum performance of NiZrTa2O8 ceramics were er = 20.61, Q × ƒ = 49200 GHz, sintered at 1325 °C.

MgZrTa2O8 ceramics with CaF2 addition were synthesized by solid-state reaction, and the effects of CaF2 addition on sintering behavior and microwave dielectric properties were investigated. The densification of MgZrTa2O8 ceramics could be effectively accelerated with CaF2 addition and the sintering temperature of CaF2-doped MgZrTa2O8 ceramics was lowered from 1475 °C to 1375 °C due to liquid phase effect. The phase composition of MgZrTa2O8 ceramics with CaF2 addition varied from single phase to three phases because of the reaction between MgZrTa2O8 and CaF2. Well-developed microstructure was observed with 0.5 wt% CaF2 addition owing to the single phase. The microwave dielectric properties presented a significant dependence on extrinsic effects. The dielectric constant (er) of CaF2-doped MgZrTa2O8 ceramics had no significant difference for all levels of CaF2 addition. The quality factors Q × ƒ were strongly affected by the content of CaF2 owing to the density, grain size and phase composition. The temperature coefficients of resonant frequency (τƒ) were correlated with the dielectric constant, which could be optimized to −2.86 ppm/°C with CaF2 addition. In this work, the MgZrTa2O8 ceramics could be optimized to the temperature-stable dielectric material for microwave application.

This paper describes a novel small-scale turtle-inspired Amphibious Spherical Robot (ASRobot) to accomplish exploration tasks in the restricted environment, such as amphibious areas and narrow underwater cave. A Legged, Multi-Vectored Water-Jet Composite Propulsion Mechanism (LMVWCPM) is designed with four legs, one of which contains three connecting rod parts, one water-jet thruster and three joints driven by digital servos. Using this mechanism, the robot is able to walk like amphibious turtles on various terrains and swim flexibly in submarine environment. A simplified kinematic model is established to analyze crawling gaits. With simulation of the crawling gait, the driving torques of different joints contributed to the choice of servos and the size of links of legs. Then we also modeled the robot in water and proposed several underwater locomotion. In order to assess the performance of the proposed robot, a series of experiments were carried out in the lab pool and on flat ground using the prototype robot. Experiments results verified the effectiveness of LMVWCPM and the amphibious control approaches.

Amphibious robots are the combination version of underwater and land robots. It is more versatile. Compared with simple land robot and underwater robot, it could adapt to more complex external environment, do some detective works, such as detect soil quality, detect water quality, and it could also be used for coastline patrol in military. It has a very broad development prospect. Compared with quadruped or hexapod robots, amphibious biped robots have simpler structure and easier maintenance. In this paper, a duck-like robot was developed. Firstly, this paper introduced the mechanical structure of swimming-fin of duck-like robot; secondly, introduced the hardware and software platform of the duck-like robot; thirdly, modeled and analyzed leg of this duck-like robot. Then, basic characteristics evaluation of a duck-like Robot has been carried out.

The localization plays an important role in the motion control and trajectory tracking of amphibious spherical robot. However, due to the complex environment in the water, some methods localization on land such as GPS cannot be applied to amphibious spherical robot. Therefore, a new method is needed to locate the amphibious spherical robot. This paper proposes an image recognition method using a global camera to locate the robot. In this method, the global camera is mounted on a platform with a known position, and the computer vision algorithm is used to identify the position of the amphibious spherical robot in the image, then calculate the coordinates and moving speed of the amphibious spherical robot. We applied this method to an amphibious spherical robot and verified it experimentally. In the experiment, the amphibious spherical robot can swim along the set rectangular trajectory by using this localization method, indicating that this localization method is effective.

As limited sensing and working capability of a single robot, multiple robots cooperative accomplishing complex tasks in formation has been a popular topic in recent years. Energy efficiency is the premise and guarantee for underwater robot to complete a wide range of task, especially for the small and bionic amphibious spherical robots with limited energy. This paper analyzed three formation shapes in the view of underwater hydrodynamic drag aiming at decreasing the energy consumption of a multiple robots system. Numerical simulation based on Computational Fluid Dynamic (CFD) is adopted to compute the drag of each individual robot and entire systems. Simulation results show that triangular formation shape can decrease the total drag. When the serial and parallel formation are needed, the longitudinal distance and transverse distance should be short as soon as possible.

Considering the complexity of robot structure and the influence of experimental environment, an Adams and C-based method for multi-step joint simulation of robots was proposed. It is of great significance to the verification control program. Unlike the joint simulation of Adams and MATLAB, the simulation method does not need to build Simulink block diagram and only bases on the programs. After completing the establishment of Adams mechanical motion model, the user subroutine can be written on the basis of the previous control program, and the interface call can be realized. The simulation results show the effectiveness and accuracy of the scheme. In addition, a gait experiment was performed on the robot. It is concluded that the simulation results can present the real situation well.

Although lithium-sulfur batteries have drawn widespread attentions due to their high energy densities at low costs, the scale-up applications are still hindered by issues such as dissolution of lithium polysulfides (LiPSs) and slow oxidation/reduction kinetics. Herein, we report a novel cathode composite composed of “moss-like” P-doped NiSe2 arrays grown on activated carbon cloth substrates (P-NiSe2/ACC). Experiments and DFT calculations together suggest that P-doping enhances the electron transfers between P-NiSe2 and LiPSs, leading to improved chemical adsorptions and catalytic effects towards the redox conversions of the active sulfur species. This effectively inhibits the shuttling of LiPSs and maximizes the utilization of sulfur towards high specific capacities and stable long-term cycling at high sulfur loadings. The strong interactions and effective catalysis of P-NiSe2 on LiPSs also enables three-dimensional growth of Li2S2/Li2S on the P-NiSe2/ACC cathode, realizing effective accommodation of volume expansions and significant alleviation of cathode passivation. As a result, the P-NiSe2/ACC cathode provides a high specific capacity of 1211 mAh g−1 at 0.2 C and an outstanding high-rate performance of 679 mAh g−1 at 3 C. At the high sulfur loading of 9.9 mg cm−2, an area capacity of 8.42 mAh cm−2 is achieved with stable cycling for 100 charge/discharge cycles.

It is a huge challenge for an amphibious robot with a high locomotory performance to locomote in amphibious environments, including crawling on rough terrains, maneuvering underwater, and launching and landing motion between land and water. To deal with such a challenge, a miniature bio-inspired Amphibious Spherical Robot (ASRobot) with a Legged, Multi-vectored Water-jet Composite Driving Mechanism (LMWCDM) has been designed. In this paper, locomotory performance of the robot in amphibious field environments is studied. First, a simplified kinematic model was built to study crawling gaits, and with an online adjustment mechanism, the gaits were adjusted, enabling the robot to climb up slopes more stably. Then, using a dynamic underwater model, a real-time dynamic thrust vectoring allocation strategy is proposed to generate the water-jet thrust and joint angles using desired forces and torques computed by four parallel PID algorithms. Finally, a set of experiments were carried out to evaluate the performance of on land locomotion and underwater locomotion. Further, outdoor locomotion experiments including crawling on various terrains, launching and landing motion, were conducted in field environments. The results demonstrate that the robot prototype possesses the high locomotory performance which endows its wide application of disaster rescue, reconnaissance and resource exploration in amphibious environments.

The effects of in-plane biaxial strains on the structural, electronic, elastic and lattice dynamical properties of tetragonal t-BC2N and z-BC2N are investigated using first-principles calculations within generalized-gradient approximation (GGA) and HSE06 range-separated hybrid functionals. We find that all the elastic constants, bulk, shear and Young’s moduli decrease (increase) almost linearly with increasing tensile (compressive) strains. However, strain-induced changes in band gaps are highly asymmetric and nonlinear. t-BC2N undergoes an indirect → direct band-gap transition at exx = −1.36%, whereas z-BC2N is always a direct band-gap material for −2.5%

With continuous improvements being made in science, technology, and production automation, robotics is becoming increasingly popular in the field of automation. Robotics has the potential to improve work efficiency, reduce production cost, protect humans from adverse conditions, and increase production scale. A three-dimensional (3D) printed amphibious spherical robot was designed to operate in various environments with a wide-range of complex conditions over a long period of time. The compact, fully waterproof design has the advantages of a reduced manufacturing time, high efficiency, good mobility, low noise, and reliable stability. This study considers how some of the more critical components of the robot, such as its leg brackets, circular middle plate, and spherical shell, respond to large dynamic stresses, shocks, and vibrations during operation; this can lead to reduced precision of the robot's locomotion and may cause critical components to become damaged or fail. To design the robot with a more rigid structure and improved dynamic characteristics, 3D models of the critical components were constructed with SolidWorks. Using ANSYS WORKBENCH software, these models were incorporated into the robot design to determine the natural frequencies and the associated mode shapes of the first six orders. The procedure and analysis results are described in this paper. The fatigue life of these critical components was examined using the cyclic load spectrum and cyclic stress as a function of number of cycles to failure (S---N curve) of acrylonitrile butadiene styrene plastic, the construction material for the robot. Finite element analysis was used for design optimization relevant to fatigue life, damage, safety, and fatigue sensitivity, and the weak areas in the components were identified. The approach described herein provides a theoretical basis for robotics design optimization.

MgZrTa2O8 ceramics with excellent microwave dielectric properties had been prepared through conventional mixed oxide route. All the sintered samples exhibited a single phase with wolframite structure type belonged to P2/c (C ) space group. The Raman spectrum revealed a similar lattice vibration in all samples with different sintering temperature. Emphatically, the extrinsic effects on microwave dielectric properties had also been investigated. The microwave dielectric properties of MgZrTa2O8 ceramics presented a significant dependence on the sintering condition. The porosity-corrected permittivity (e-pc) was calculated to investigate the influence of the porosity to the dielectric constant (er). For the high-dense MgZrTa2O8 ceramics, the main factors which had influences on quality factors (Q × f) were the grain size and grain-size distribution. The temperature coefficient of resonant frequency (τ f ) was depended on the dielectric constant and pores. The typical microwave dielectric properties of MgZrTa2O8 ceramics were er = 22.76, Q × f = 131,500 GHz, τ f = −33.81 ppm/°C, sintered at 1475 °C.

Two potential superhard monoclinic BC3N structures, namely, m-BC3N-1, and m-BC3N-2, have been proposed through first-principles calculations. The structural, mechanical, and electronic properties of m-BC3N structures are investigated in detail. The phonon dispersions and calculated elastic constants show that two m-BC3N phases are dynamic and mechanical stable. The formation energies of these m-BC3N structures are positive, indicating that they are metastable which similar to most ternary B–C–N compounds. Based on the elastic calculations, both of m-BC3N-1 and m-BC3N-2 behave in brittle character, and show great anisotropy in Young's modulus. In hardness simulation, a microscopic theoretical model is employed, and finally obtained the Vicker's hardness of two m-BC3N structures with 56.38 GPa and 52.96 GPa, respectively. Using a hybrid functional HSE03, we estimate that the two m-BC3N structures are indirect semiconductors with a band gap of 3.77 eV and 3.25 eV. Besides, m-BC3N-2 can be converted from an indirect band gap semiconductor to a direct band gap semiconductor with band gap of 3.45 eV when exposed to a hydrostatic pressure of 30 GPa.

Minimally invasive vascular interventional surgery is widely used and remote-controlled vascular interventional surgery robots (RVIRs) are being developed to reduce the occupational risk of the intervening physician in minimally invasive vascular interventional surgeries. Skilled surgeon performs surgeries mainly depending on the detection of collisions. Inaccurate force feedback will be difficult for surgeons to perform surgeries or even results in medical accidents. In addition, the surgeon cannot quickly and easily distinguish whether the proximal force exceeds the safety threshold of blood vessels or not, and thus it results in damage to the blood vessels. In this paper, we present a novel method comprising compensatory force measurement and multimodal force feedback (MFF). Calibration experiments and performance evaluation experiments were carried out. Experimental results demonstrated that the proposed method can measure the proximal force of catheter/guidewire accurately and assist surgeons to distinguish the change of proximal force more easily. This novel method is suitable for use in actual surgical operations.

A novel polypyrrole nanowires coated by graphene oxide (PPy-NWs/GO) has been successfully synthesized by one-step electrochemical method, whose structure was different from previously reported PPy/GO composites. The microbial fuel cell equipped with PPy-NWs/GO as anode was fabricated and compared with PPy-NWs ones. The SEM images show that the synthesized PPy-NWs/GO materials possess more surface areas than PPy-NWs. The electrochemical analysis indicated that PPy-NWs/GO anode had lower charge transfer resistance, which may be attributed to synergistic effect of them. The MFC equipped with PPy-NWs/GO anode have higher circle voltages and the power density is about 22.3 mW/m(2), which is great higher than that of PPy-NWs about 15.9 mW/m(2). These improvements of the MFCs may be due to more bacteria on the larger biofilms based on GO nanosheets, indicating that the PPy-NWs/GO is more effective anode for improving electricity generation. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1007/s13205-018-1321-0) contains supplementary material, which is available to authorized users.

This paper presents a performance evaluation of the multi-vectored water-jet propellers system (MVWPS) for the amphibious spherical robot IV (ASR-IV), which will contribute to the real-time dynamic thrust vectoring of ASR-IV. This work extends the 2D modeling into 3D space, which benefits the 4DoFs control of ASR-IV more. The dynamic modeling (forces and moments) of ASR-IV can be obtained by synthesizing the propulsive vectors of four propellers. Thus, a novel experimental mechanism was developed to evaluate the MVWPS. This mechanism was designed with the mass distribution centered for the robot. Using a six-axis force/torque sensor at the equivalent mass center, we obtained the direct propulsive effect of the system for the robot. Experiments of one propeller were conducted to establish the relationship between the pulse width module (PWM) signal and the thrust. Then, experiments of MVWPS were carried out to evaluate the performance of MVWPS.

Silica glasses dispersed with Pt nanoparticles and Ag nanoparticles are derived from solid-state sintering of mesoporous silica SBA-15 encapsulated with Pt nanoparticles and Ag nanoparticles, respectively. Using mesoporous powders for sintering is a facile method to lower synthesis temperature for glass making and to efficiently disperse noble metal nanoparticles in silica glass matrix. The included nanoparticles still play their functional roles in impacting on optical properties of the glass products prepared by this novel method. The glass dispersed with Pt nanoparticles exhibits brown color due to the interband electron transition of Pt nanoparticles. The coloring effect of surface plasmon resonance absorption from Ag nanoparticles colors the glass dispersed with Ag nanoparticles with yellow. Open-aperture and closed-aperture Z-scan methods are applied to measure third-order nonlinear absorption and refraction coefficient of the composite glasses, respectively, under femtosecond laser radiation at 880 nm wavelength. The glass dispersed with Pt nanoparticles behaves intense nonlinear absorption comparing with nonlinear refraction in magnitude, which could be attributed to interband electron transition by monophoton absorption of Pt nanoparticles. The glass dispersed with Ag nanoparticles shows stronger nonlinear refraction than saturated absorption. The dominant contribution to third-order optical nonlinearity of silica glass dispersed with Ag nanoparticles is intraband transition of free electrons near the Fermi surface of Ag nanoparticles. This method may have potential applications for fabricating silica glasses dispersed with ultrafine functional particles, which are potentially applicative in the fields of photonics.

ZnTa2O6 ceramics with various amount of Al2O3 additive were synthesized by a conventional mixed-oxide route. The grain growth of ZnTa2O6 ceramics was accelerated with Al2O3 additive. However, excessive addition (>1.0 wt%) of Al2O3 leaded to abnormal grain growth. With Al2O3 addition, the Al2O3 additive did not solubilized into ZnTa2O6 structure but resulted in forming the second phase. The Al2O3 addition resulted in the lower sintering temperature of ZnTa2O6 ceramics and improved microwave dielectric properties. The dielectric constant (er) of the samples did not change much and ranged from 32.41 to 34.33 with different amount of Al2O3 addition. The optimized quality factor (Q × f) was higher than 70,000 GHz as a result of the denser ceramics. The temperature coefficient of resonant frequency (τ f ) of the doped ZnTa2O6 ceramics could be optimized to near-zero.

Amphibious micro-robots are being developed for complicated missions in limited spaces found in complex underwater environments. Therefore, compact structures able to perform multiple functions are required. The robots must have high velocities, long cruising times, and large load capacities. It is difficult to meet all these requirements using a conventional underwater micro-robot, so we previously proposed an amphibious spherical father---son robot system that includes several micro-robots as son robots and an amphibious spherical robot as a father robot. Our father robot was designed to carry and power the son robots. This paper discusses improvements to the structure and mechanism of the father robot, which was designed to have a spherical body with four legs. Based on recent experiments in different environments, we have improved the father robot by adding four passive wheels, and we have redesigned its structure by means of three-dimensional printing technology, resulting in greatly improved velocity and stability. Moreover, due to the complexity and uncertainty of many underwater environments, it is essential for the father robot to have adequate structural strength. We analyzed the movement mechanisms and structural strength using finite element analysis to obtain the deformation and equivalent stress distributions of the improved robot. The results provide support for further analysis of the structural strength and optimal design of our amphibious spherical father robot.

We describe the novel, multiply gaited, vectored water-jet, hybrid locomotion-capable, amphibious spherical robot III (termed ASR-III) featuring a wheel-legged, water-jet composite driving system incorporating a lifting and supporting wheel mechanism (LSWM) and mechanical legs with a water-jet thruster. The LSWM allows the ASR-III to support the body and slide flexibly on smooth (flat) terrain. The composite driving system facilitates two on-land locomotion modes (sliding and walking) and underwater locomotion mode with vectored thrusters, improving adaptability to the amphibious environment. Sliding locomotion improves the stability and maneuverability of ASR-III on smooth flat terrain, whereas walking locomotion allows ASR-III to conquer rough terrain. We used both forward and reverse kinematic models to evaluate the walking and sliding gait efficiency. The robot can also realize underwater locomotion with four vectored water-jet thrusters, and is capable of forward motion, heading angle control and depth control. We evaluated LSWM efficiency and the sliding velocities associated with varying extensions of the LSWM. To explore gait stability and mobility, we performed on-land experiments on smooth flat terrain to define the optimal stride length and frequency. We also evaluated the efficacy of waypoint tracking when the sliding gait was employed, using a closed-loop proportional-integral-derivative (PID) control mechanism. Moreover, experiments of forward locomotion, heading angle control and depth control were conducted to verify the underwater performance of ASR-III. Comparison of the previous robot and ASR-III demonstrated the ASR-III had better amphibious motion performance.

Nature has provided the inspiration for many robots, leading to the development of biomimetic machines based on stick insects, jellyfish, butterflies, lobsters, and inchworms. Some carnivorous plants are capable of rapid motion, including mimosa, Venus flytraps, telegraph plants, sundews, and bladderworts, all of which are of interest in the design of biomimetic robots that can be activated in a controlled manner to capture prey using trigger hairs. Here, we describe a biomimetic robotic inspired by a Venus flytrap and fabricated using two ionic polymer metal composite (IPMC) actuators. First, we describe the structure of the robotic flytrap, which consists of two IPMC lobes and a proximity sensor, and discuss the design of the control circuitry. We then evaluate the deformation and bending force of the IPMC actuator with various applied signal voltages. We describe a prototype robotic flytrap utilising a proximity sensor to imitate the trigger hairs of the Venus flytrap. We conducted an experiment to assess the feasibility of the biomimetic flytrap. To evaluate grasping ability, we measured the maximum grasping payload with different applied voltages. To enlarge the working area, we integrated biomimetic walking and rotating motion into the robotic Venus flytrap. This paper describes a prototype movable robotic Venus flytrap and evaluates its walking and rotating speeds.

Underwater intervention is a favorite and difficult task for AUVs. To realize the underwater manipulation for the small size spherical underwater robot SUR-II, a father---son underwater intervention robotic system (FUIRS) is proposed in our group. The FUIRS employs a novel biomimetic microrobot to realize an underwater manipulation task. This paper describes the biomimetic microrobot which is inspired by an octopus. The son robot can realize basic underwater motion, i.e. grasping motion, object detection and swimming motion. To enhance the payload, a novel buoyancy force adjustment method was proposed which can provides 11.8 mN additional buoyancy force to overcome the weight of the object in water. Finally, three underwater manipulation experiments are carried out to verify the performance of the son robot. One is carried by swimming motion and buoyancy adjustment; the other two are only carried by buoyancy adjustment. And the experimental results show that the son robot can realize the underwater manipulation of different shape and size objects successfully. The swimming motion can reduce the time cost of underwater manipulation remarkably.

Based on monocular camera, an underwater detection and tracking system for amphibious spherical robot is proposed to realize autonomous cruise of underwater pipelines. Firstly, according to the imaging characteristics of underwater image, the image of pipeline is detected by image binarization, edge detection and Hough transform. And then, the Kalman filter was carried out according to the edge information and the underwater pipeline was tracked. The control scheme of the visual system to the amphibious spherical robot was improved, and the tracking pipe motion of the amphibious robot is controlled by PID algorithm. Finally, we carried out some experiments under different scenes to demonstrate the effectiveness of the proposed underwater pipeline tracking system, and the experimental results showed that the proposed underwater pipeline tracking algorithm has good robustness and real - time performance.

Considering the complicated disturbance in underwater circumstance, usually it is difficult to solve the control problem when the robot changes its motion state or it is subject to ocean currents, its performance deteriorates since the fixed set of parameters is no longer valid for the new conditions. Thus, in this paper, an auto-tune PID (Proportional + Integral + Derivative)-like controller based on Neural Networks is applied to our amphibious spherical underwater robot, which has a great advantage on processing online for the robot due to their nonlinear dynamics. The Neural Networks (NN) plays the role of automatically estimating the suitable set of PID gains that achieves stability of the system. The NN adjusts online the controller gains that attain the smaller position tracking error. The performance of the NN-based controller is investigated in ADAMS and MATLAB cooperative simulation. The velocity of the spherical robot can be controlled to precisely track desired trajectory in body-fixed coordinate system. Additionally, real time experiments on our underwater spherical robot are conducted to show the effectiveness of the algorithm.

Location system is crucial to many intelligent robots, especially for underwater robots. To increase the autonomous ability of amphibious spherical robots in underwater environment, an underwater vision locating system was designed in this paper, and the ToF (time of fly) camera (RGB-D camera) was used and introduced in this system. Through the image capture from the camera in water, two kinds of image information could be acquired, which are include color image and depth image. The theoretical analysis show that the location of objective could be calculate easily from those image information. In underwater environment, the depth information attenuated, a calibration experiment for distance correction was designed. These results were used for the coordinate establishing. The construction of the experimental environment and final results were provided. Through the analysis of experimental results, the feasibility of the vision locating method based the RGB-D camera was verified and this system will be used for providing the location of amphibious spherical robots in the future work.

Robust and performing navigation systems for Autonomous Underwater Vehicles (AUVs) play a discriminant role towards the success of complex underwater missions. This paper presents a new design and development of a low-cost INS (Inertial Navigation System) using Miro-Electro-Mechanical-System (MEMS) inertial sensor and the pressure sensor (PS). The intensive pre-processing and modeling MEMES sensor's primitive, noisy motion data are outline, these techniques transform the erroneous motion data into practical motion indicators illustrated in 3D position, 3D velocity and 3D orientation. INS acts as a dead reckoning device. The pressure sensor is used to detect the depth data of underwater Vehicles. The quality of the filtering algorithm for the estimation of the AUV navigation state strongly affects the performance of the overall system. In this paper, the authors present adapt the Kalman Filter (KF) approach. Experiments were conducted to improve the navigation system performance of the INS and PS installed on the Amphibious Spherical Robot III (ASR III) for motion and attitude estimation. Lastly the experiment results are evaluated and verified using the sensor data from the navigation system.

The motion control of underwater spherical robot is a complicated process, which has the characteristics of high inertia and non-linearity. There are many influencing factors for the underwater spherical robot motion such as ambient temperature and water current, so it is difficult to obtain the real-time kinematic model. Therefore, it is hard for traditional PID to achieve stable motion control of the underwater spherical robot. In this paper, the actual motion control of underwater spherical robot was realized that used fuzzy PID control method. Compared with traditional PID for the underwater spherical robot, fuzzy PID has some advantages, such as good robustness and good dynamic performance. To demonstrate that the fuzzy PID was more suitable to our underwater spherical robot, we carried out some real time experiments. Comparison experimental results demonstrated that the fuzzy PID control method has better dynamic performance than the traditional PID.

Aiming at vision applications of our amphibious spherical robot, a real-time detection and tracking system adopting Gaussian background model and compressive tracking algorithm was designed and implemented in this article. Considering the narrow load space, the limited power resource and the specialized application scenarios of the robot, a heterogeneous computing architecture combining advanced Reduced Instruction-Set Computer (RISC) machine and field programmable gate array was proposed on the basis of Zynq-7000 system on chip.Under the architecture, main parts of the vision algorithms were implemented as software programs running on the advanced RISC machine-Linux subsystem. And customized image accelerators were deployed on the field programmable gate array subsystem to speed up the time-consuming processes of visual algorithms. Moreover, dynamic reconfiguration was used to switch accelerators online for reducing resource consumption and improving system adaptability. The word length of accelerators was optimized with simulated annealing algorithm to make a compromise between calculation accuracy and resource consumption. Experimental results confirmed the feasibility of the proposed architecture. The single board tracking system was able to provide an image processing rate of up to 89.2 frames per second at the resolution of 320 × 240, which could meet future demands of our robot in biological monitoring and multi-target tracking.

Using first-principles calculations, the structural, elastic, and electronic properties of a potential superhard material h-C 6 under external forces, including hydrostatic pressure and biaxial strain, are investigated in detail. For both types of applied force, the satisfaction of elastic criteria and the positive phonon frequencies in the first Brillouin zone confirm the mechanical and dynamical stability of the material. Considerable values of the elastic moduli and elastic constants are obtained under equilibrium conditions, especially for Young’s modulus (992 GPa) and shear modulus (463 GPa). Meanwhile, all of these quantities increase (decrease) in value with increasing pressure and compressive (tensile) strain. In the Vickers hardness simulation, a microscopic model of the covalent crystal is used for each type of bond as well as for the crystal, based on a 3 × 3 × 3 supercell. The hardness of h-C 6 (69.96 GPa) exceeds that of cubic boron nitride and can be enhanced by the application of pressure or compressive strain, indicating the potential of h-C 6 as a novel superhard material. The infrared spectra of h-C 6 are also simulated. A hybrid HSE06 functional is employed in calculations of electronic properties, which show that h-C 6 is an indirect semiconductor with a bandgap energy of 2.993 eV and can be slightly modulated by external forces.

In our previous work, ions liquids and distilled water were separately used as electrolyte for electrochemical exfoliation of graphite rods to synthesize CDs with excellent behaviors. However, the expensive price of ions liquids and consuming time for distilled water both limit CDs' large-scale preparation using electrochemical exfoliation. Herein, cheap and common salt is dissolved in distilled water as electrolyte to exfoliate graphited rods for synthesis of CDs, which is able to break the above-mentioned bottleneck perfectly. The obtained CDs show similar properties with previous ones in morphology, size, surface groups, and optical behaviors. When tuning applied voltages or concentrations of electrolyte, the obtained CDs do not show obvious varies in properties and behaviors. Besides, it is found that only anode was corroded in reaction, so it is reasonably speculated that the same anions wound obtain similar results, and this hypothesis was also proven to be correct by the measured results. The solution of salt as electrolyte provide a practical way for large-scale preparation of CDs by electrochemical method due to cheap and easy-access raw material, plain equipment and convenient operation, rapid reaction and shorter consuming time.

Aiming at exploration tasks in complex amphibious environments, quadruped gaits were designed, implemented and evaluated for our amphibious spherical robot to enhance its adaptabilities to various terrains. A simplified locomotion model of the robot was established to analyze the walking process. Then three types of walk gait were implemented on the robotic platform using FPGA, which provided different stability and adjustable motion speeds to adapt various terrains. Furthermore, the attitude of the robot was estimated online using an inertial measurement unit. And the adopted gait was adaptively adjusted with the acquired compensation value, which ensured that the robot was able to walk on a slope no larger than 20 degrees. Evaluation experiments on robotic motion performance indicated that the amphibious spherical robot was capable of moving stably at different speeds in multiple environments, which enhanced its mobility and viability.

Developing efficient movement gaits for quadruped robots has intrigued investigators for years. Trot gait, pace gait, as fast and stable dynamic locomotion gaits, have been widely used in robot control. Therefore, the purpose of this paper is to control an amphibious spherical quadruped robot to achieve these two gaits. Firstly, this paper references the trot gait and pace gait pattern of quadruped creature and identifies the order and the law of quadruped bionic robot. Secondly, based on the virtual leg techniques and the Spring-Loaded Inverted Pendulum (SLIP) model, a simplified dynamic analysis model is established, and the relationship between force and motion is obtained by using Lagrange dynamics equation. Thirdly, by adjusting the force and moment of the joint of robot, continuous and stable trot gait and pace gait motion are simulated in ADAMS platform. Finally, a comparison of theoretical calculations and simulation results demonstrated the robot's potential and its feasibility of trot gait and pace gait.

As a critical important function for autonomous mobile robots, visual tracking is a challenge work in the field of computer vision, for the reason that factors like illumination variance, partial occlusions and target appearance changes shall be carefully considered. Focus on applications of our amphibious spherical robots, an adaptive visual tracking algorithm was proposed on the basis of compressive tracking. A feature selection method was designed to choose random Haar-like feature templates in various scales by calculating Fisher's criterion functions of features. On this basis, a random feature pool, which tried to preserve discriminative features at different frames, were constructed and then maintained on-line to provide candidate appearance model of the target. Moreover, an adaptive update mechanism was adopted for selectively updating feature templates and classifier parameters of the improved compressive tracking algorithm, which alleviated the drift problem. Experimental results with various image sequences demonstrated the effectiveness and robustness of the proposed tracking algorithm, which can meet practical application requirements of the amphibious spherical robots.