Under the influence of nuclear radiation, the reliability of steam generators (SGs) is an important factor in the efficiency and safety of nuclear power plant (NPP) reactors. Motion planning that remotely manipulates an SG mobile tube-inspection robot to inspect SG heat transfer tubes is the mainstream trend of NPP robot development. To achieve motion planning, conditional traversal is usually used for base position optimization, and then the A∗ algorithm is used for path planning. However, the proposed approach requires considerable processing time and has a single expansion during path planning and plan paths with many turns, which decreases the working speed of the robot. Therefore, to reduce the calculation time and improve the efficiency of motion planning, modifications such as the matrix method, improved parent node, turning cost, and improved expanded node were proposed in this study. We also present a comprehensive evaluation index to evaluate the performance of the improved algorithm. We validated the efficiency of the proposed method by planning on a tube sheet with square-type tube arrays and experimenting with Model SG.

The reliability of the Steam Generator is a key factor affecting the overall efficiency and safety of nuclear power plant reactors. Under the influence of nuclear radiation, remote control robots are currently used for Steam Generator heat transfer tubes inspection. In this paper, a new inspection robot is designed with better structure and higher working efficiency. Structural modeling and kinematic analysis are carried out. A modular control system is designed and applied for system integration. To verify the practicality of the robot, tube sheet motion experiments and performance analysis are undertaken. It results that the proposed inspection robot efficiently moves on the tube sheet and has excellent motion performance.

Abstract This article designs a frog-inspired swimming robot based on pneumatic muscles. The musculoskeletal characteristics of the frog are refined and used as the basis for the design of the robot joint structure and movement mode. The posture adjustment module, joint water seal, and power system are designed to meet the robot’s motion requirements, and the structure optimization design of the robot is completed by combining simulation analysis. The body length of the robot is about 710 mm, and the overall mass is 10 kg. Combining the structural characteristics of the robot, the control system is built to realize the frog-like motion. The robot’s propulsion speed is about 0.6 m/s, the propulsion distance reaches 2.4 m, the turning angle is 30°, and the turning radius is 0.6 m. The prototype experiment verifies the rationality of the frog-inspired swimming robot structure design and the reliability of the control system and water seal.

To expand the future clinic applications of biodegradable magnesium alloy, polymer coatings with excellent biocompatibility are the keys to solve the local alkalinity and rapid hydrogen release. Natural−organic silk fibroin provides an approach to fabricate a protective coating on biomedical Mg−Zn−Ca alloy, however, the adhesion force and mechanical properties of the coating on substrates are ought to be further improved without any chemical conversion/intermediate layer. Hereby, based on VUV/O3 surface activation, a hybrid of silk fibroin and sodium alginate is proposed to enhance the adhesion force and mechanical properties of the composite coatings on hydrophilic Mg−Zn−Ca alloy surfaces. Various mass ratios of sodium alginate addition were investigated to achieve the optimum coating strategy. The nanoscratch test and nanoindentation test confirmed that the adhesion force was tripled and mechanical properties index was significantly improved when the mass ratio of silk fibroin/sodium alginate was 70/30 compared to pure silk fibroin or sodium alginate coatings. Meanwhile, the corrosion rate of the coated Mg−Zn−Ca alloy was significantly delayed with the addition of sodium alginate, resulting in a reaction layer during corrosion process. Furthermore, the mechanisms for both adhesion and corrosion processes were discussed in detail. Our findings offer more possibilities for the controllable surface performance of degradable metals.

Based on a two-step plasma surface activation process (O2 followed by N2 plasma), silk fibroin coating was prepared on Mg-Zn-Ca alloy without conversion layer to retard the corrosion. This method achieved homogenized surfaces with better hydrophilicity and increased functional groups, significantly improving the adhesion force. The corrosion resistance of coated magnesium alloy was significantly enhanced compared to that of bare samples. Nanoscratch combined with corrosion behavior indicated that the remarkably improvement of anticorrosion ability attributed to the protective layer and the increased adhesion force. Our findings provided more possibilities for corrosion protection of degradable metals.

Real-time virtual view synthesis technique has been widely used in kinds of 3D television systems. The image distortion is its main problem for lack of reference information in image inpainting process. This paper proposes a new view synthesis method to solve this problem based on DIBR techniques. First, four common real-time hole-filling algorithms are tested and analyzed, the proposed method automatically selects different algorithms depending on the size of the hole to be filled. Then, a process called depth erode is designed to remove the pixels around boundaries between foreground and background in the reference image. These pixels are hard to be correctly segmented and cause artifacts in synthesized views. Finally, a structure called Background Table is proposed to extract and store spatiotemporal background information. The background table is updated simultaneously and gives a quick access to background information. The usage of spatiotemporal background information increases the reference information in image inpainting process and greatly reduces inpainting distortion. Our experimental results show that the proposed method has excellent subjective and objective performance over state-of-art methods.

BACKGROUND:Stroke is the most prevalent neurological disease and often leads to disability. Stroke can affect a person's daily life, for example, its typical feature is the decline in the patient's upper limbs. In order to reduce the sports injury of stroke patients, the best method is to carry out certain rehabilitation training. OBJECTIVE:In this paper, inverse kinematic analysis and trajectory planning of a modular upper limb rehabilitation exoskeleton are proposed. METHODS:The reverse coordinate system method is applied to solve inverse kinematics of the exoskeleton with a non-spherical joint in the wrist. For verifying the effectiveness of the algorithms, the smooth round-trip trajectory movement in joint place is designed and simulated. RESULTS:The reverse coordinate system method can simplify the calculation process compared with the normal coordinate system. Smooth round-trip trajectory planning is simulated to generate a smooth trajectory curve. CONCLUSIONS:The developed inverse kinematics algorithm and trajectory planning method are effective.

Soft modular robots have the advantages of both bionic continuum robots and modular self-reconfigurable robots. They have potential application for working in narrow space and uneven terrain. The outstanding abilities of the soft modular robots are infinite degrees of freedom and a changeable configuration. However, these advantages also incur difficulty in mathematical modeling and continuous motion control, especially for docking, which is the key to realizing a changeable configuration. Therefore, the development of a soft modular robot requires a modeling method to guide the module's motions accurately. In this paper, we design and manufacture a pneumatic soft modular robot with a novel connecting mechanism to achieve docking. A nonlinear dynamic model of our soft module is established. In particular, the analytic solutions of the module plane docking are presented. Based on the nonlinear dynamic modeling, three experiments are performed under different conditions. The experimental results pertaining to module plane bending agree with the theoretical values, which verify the accuracy of the modeling method. Moreover, fixed point docking and two modules docking experiments demonstrate the validity of the modeling method and the docking ability. The modeling method proposed in this paper can well guide the docking of soft modular robots.

In this paper, a new modular upper limb rehabilitation exoskeleton, which is actuated by a parallel mechanical structure, is designed to help stroke patients. For analysing the relationship between motor torque and joint torque of the novel exoskeleton, a conversion algorithm mapping motor motion to joint motion is developed here. Then, to simplify the dynamics model of exoskeleton with parallel actuated joints, the serial equivalence configuration dynamics of the exoskeleton is established to be equivalent to the parallel joints dynamics. Afterwards, a torque controller used for our exoskeleton is designed based on the proposed conversion algorithm and the inverse dynamics of exoskeleton. It should be noted that the controller mentioned above combines both conversion algorithm and joint position decoupling. At last, for verifying the effectiveness of the proposed algorithms, a trajectory tracking simulation is given, and the simulated results show the proposed algorithms are valid.

The combination of lithium niobate (LiNbO3) and glass without an intermediate layer is an essential component of micro/nanofluidics and optical waveguides. Direct bonding is a popular method for joining homo/heterogeneous materials into a single composite. However, direct bonding of LiNbO3 and glass is extremely difficult due to the chemical inertness of LiNbO3 and the large mismatch of the coefficients of thermal expansion of these materials. In this work, we realized direct bonding of LiNbO3 and glass via VUV/O-3 activation at 150 degrees C. Focused ion beam microfabrication tests and observation by scanning electron microscopy and transmission electron microscopy confirmed the strong LiNbO3/glass bonding interfaces. The excellent transmittance and piezoelectric properties of the direct bonded pairs and the single-crystal orientation of the LiNbO3 close to the glass demonstrated that the VUV/O-3 activated direct bonding method was suitable for the fabrication of high-performance surface acoustic wave (SAW)-actuated LiNbO3-based devices. Additionally, we investigated the bonding mechanism through water contact angles, atomic force microscopy, Raman spectroscopy, FTIR spectroscopy, and adhesion measurements.

In order to enable robot the omni-directional mobility in non-ferromagnetic pipelines, a negative pressure adsorption pipeline robot is designed. Firstly, a mechanical structure was designed for the omni-directional mobile pipeline robot based on negative pressure. A variable adsorption force control method for the robot was proposed by establishing the internal curved surface motion model of the pipeline robot through mechanical analysis. Simulation results show that the robot could steadily adsorb in any arbitrary position of the pipeline, possess the capability of omni-directional mobility and have a significantly improved endurance time.

Based on the embedded computing platform, we propose a visual inertial fusion SLAM system. The software algorithm combines the matching of monocular visual feature recognition and IMU measurement pre-integration algorithms. And the back-end uses tightly-integrated nonlinear optimization algorithms to process data. The hardware uses NVIDIA's Jetson TX1 parallel processing computing platform and low-cost sensors to retrieve data. The robot uses the open source robot operating system ROS as the operating system and the upper computer uses the UBUNUT system. Based on the embedded parallel processing, visual inertial SLAM system has the characteristics of low cost and good stability.

The Stewart platform is a typical parallel manipulator. It is used as a space docking mechanism whose requirement for movement scope is determinate. This article addresses the dimension synthesis of the space docking mechanism. First, this article compares the common indexes used to evaluate the performance of parallel manipulator. These indexes can mainly be divided into two types. The evaluation indexes based on the Jacobian matrix, including the singular value index, the manipulability index, and condition index, are derived from the Jacobian matrix of the manipulator, and the transmissibility indexes, such as pressure angle, transmission angle, and motion/force transmission index, lay emphasis on the power transmission ability of manipulator. This article proposes the global transmission index under determinate constraint of workspace on the basis of the previous transmissibility indexes to evaluate the performance of parallel manipulator whose workspace is determinate and movement is the combination of translation and rotation. And the optimization design of the manipulator is carried out by taking the global transmission index under determinate constraint of workspace into account. The detailed process of determining the optimal configuration for the Stewart manipulator used as space docking mechanism is presented. The optimal result is gotten, which has a large value of global transmission index under determinate constraint of workspace in the required workspace, and a simulation is carried out to verify the validity of the optimal result.

This paper presents a synthetic algorithm for tracking a moving object in a multiple-dynamic obstacles environment based on kinematically planar manipulators. By observing the motions of the object and obstacles, Spline filter associated with polynomial fitting is utilized to predict their moving paths for a period of time in the future. Several feasible paths for the manipulator in Cartesian space can be planned according to the predicted moving paths and the defined feasibility criterion. The shortest one among these feasible paths is selected as the optimized path. Then the real-time path along the optimized path is planned for the manipulator to track the moving object in real-time. To improve the convergence rate of tracking, a virtual controller based on PD controller is designed to adaptively adjust the real-time path. In the process of tracking, the null space of inverse kinematic and the local rotation coordinate method (LRCM) are utilized for the arms and the end-effector to avoid obstacles, respectively. Finally, the moving object in a multiple-dynamic obstacles environment is thus tracked via real-time updating the joint angles of manipulator according to the iterative method. Simulation results show that the proposed algorithm is feasible to track a moving object in a multiple-dynamic obstacles environment.

Now, there is no automatic spraying technology which is used to spray ships with the help of spraying robots, because the outside surface of ships is large and complex. The huge outside surface of ships makes it impossible to determine the absolute position and attitude of the surface in the space, which impedes the application of mobile spraying robots in the ship block spraying. This paper puts forward a positioning technology which can be used for the ship block automatic spraying of the complex surface of large ships: the position and coordinate of ships is the research object, and with the use of the total-station device, the position and attitude of large ship blocks in the space can be determined accurately through the change of spatial points. Meanwhile, according to the calculation principle of the total-station device, the influence of the position of the total station on the positioning accuracy is analyzed, and when it comes to the measuring errors of length and angle, the best angle and distance used to build the total station is obtained through the combination of simulation and theories and the existing conclusion is modified. Finally, this conclusion is verified through the calibration in the experiment and the feasibility of this scheme applied to the positioning of large curved surfaces is also demonstrated.

In order to build an uniform coordinate system for a medical robot and its vision system in surgery, an automatic space calibration method is proposed based on the rotational and translational movements of the robot. With this method, both the robot and the NDI vision system can be calibrated to the patient's bones contour, which matches the virtual model built from the CT images. Thus surgical operation can be carried out by the robot following the preoperative design based on the virtual model. The calibration accuracy directly determines the precision of surgical operation. Experiments were carried out to evaluate the effectiveness of this calibration method, and the result showed that the position and posture error can meet the operation requirements. Also the calibration can be executed automatically to decrease the human effect and increase the reliability and stability.

To accurately construct the topographic information of a six-legged walking robot in real time, this study proposes a stereo matching algorithm that can conduct disparity estimation on each pixel by using the Bayesian posterior probability model based on GPU-accelerated parallel processing. In the proposed algorithm, supporting points construct a disparity space to obtain the prior distribution probability density of each pixel and then substitute it into the Bayesian posterior probability model to establish the energy function of the disparity. The estimated disparity value of the unknown pixel can be obtained by minimizing the energy function. By performing a consistency check on the left and right sides of an image, the mismatching pixel can be eliminated. According to the disparity value of the supporting point, the disparity filling of the mismatching area can be achieved by applying the adaptive weight method on the basis of cross extending to obtain the accurate density of the disparity map. Parallel computing in each stage of the proposed algorithm is performed by using the compute unified device architecture to reduce the running time. Experimental results show that the proposed algorithm has good robustness for different illuminations and texture curved surface reconstruction. The algorithm can also adapt to the fast matching of images in different sizes and reconstruct the disparity map of scenes in real time under the resolution ratio of 640 × 480. The stereoscopic vision test board is employed to construct the disparity map of real scenes and verify the practical application effect of the algorithm. Good experiment effect is achieved.

Vision and AHRS (attitude and heading reference system) sensors fusion strategy is prevalent in recent years for the legged robot's SLAM (Simultaneous Localization and Mapping), due to its low cost and effectiveness in the global positioning system. In this paper, a new adaptive estimation algorithm is proposed to achieve the robot SLAM by fusing binocular vision and AHRS sensors. A novel acceleration algorithm for SIFT implementation based on Compute Unified Device Architecture (CUDA) is presented to detect the matching feature points in 2D images. All the steps of SIFT were specifically distributed and implemented by CPU or GPU, according to the step's characteristics to make full use of computational resources. The registration of the 3D feature point cloud is performed by using the iterative closest point (ICP) algorithm. Our GPU-based SIFT implementation can run at the speed of 30 frames per second (fps) on most images with 900 x 750 resolution in the test. Compared to other methods, our algorithm is simple to implement and suitable for parallel processing. It can be easily integrated into mobile robot's tasks like navigation or object tracking, which need the real-time localization information. Experiments results showed that in the unknown indoor environments, the proposed algorithm's operation is stable and the positioning accuracy is high. (C) 2015 Elsevier B.V. All rights reserved.

In order to make full use of the ability of the low impact docking mechanism to reduce the contact force in the docking process, the impedance control strategy is designed. And then a kind of parameter adjusting flow is proposed for the impedance controller based on the influence rules of the target impedance. To perform a low impact docking mission unaware of the initial position error and orientation error, two kinds of control strategies including integral impedance controller (IIC) and distributed impedance controller (DIC) are proposed, and a co-simulation of the control strategies using the MATLAB and ADAMS software are carried out to seek out the advantages and disadvantages of these strategies. The conclusions are drawn that the DIC is superior to the IIC, which lay the theoretical foundation for the subsequent docking experiments.

In order to conveniently obtain topographic information and overcome the draw back of the traditional contact measurement methods ,a 3D terrain reconstruction method based on binocular vision was put forward .Firstly ,image correction was completed .Next ,3D point information of terrain was ob‐tained through an efficient stereo matching algorithm based on supporting point neighbor extending .And then ,a curvature method based on octree principle was used to simplify the point cloud .Finally ,an im‐proved Delaunay triangle subdivision algorithm was used to accomplish the triangulation and rebuild the 3D model of terrain .Experimental results have shown that the proposed methods in this paper can acquire dense disparity map in 1 second and reduce the number of point from 21 841 to 5 463 (25% ) within 0 .7 second .And on this basis ,triangulation of the rough terrain for 3D model rebuilding can be quickly a‐chieved with the details reserved .