Advanced Materials Research Vol. 1039

Abstract: Measurement method of joint angle for underwater manipulator is studied in this paper. The swing of a manipulator can be described as a circular motion in spatial. Therefore this paper proposes a spatial circle fitting algorithm. The points for spatial circle fitting come from multiple stereo vision system. At first, attach the designed target to the robot arm, then proposes algorithm to track the target in real time. Then three-dimensional coordinates of target’s movement in space at each location can be obtained by using stereo reconstruction techniques. At last, the center and radius of the circle can be calculated by spatial circle fitting. Through the theory of analytic geometry, the manipulator’s joint angle can be calculated. Experiments show that the algorithm proposed in this paper is well used in manipulator’s joint angle measurement.

Abstract: In order to solve the difficulty of low contrast feature extracting between labeled features and background, a new method combined the Hough transform and Canny algorithm is put forward for tensile test using the video extensometer, and a new algorithm edge detection is also obtained based on Canny an feature region tracking as well. The algorithm has proved to be a high positioning accuracy and computational efficiency in the test.

Abstract: In this paper, the light field is modeled from four fundamental factors and the spatial multiplexing of light field is analyzed. The relationship between the light field and the pixel in raw image is described for one typical light field camera. Then, the light field data is adopted in refocus and all-focus imaging. In the aspect of refocus, the hill-climbing algorithm is designed to found the highest value of the image clarity, which is evaluated with the second order gradient square function. On all-focus, the divide and conquer algorithm is adopted to find the optimal path in a gird. The experiment results confirm that the light field model is valid. The proposed refocus method is robust in comparisons with other four clarity measures. Our all-focus method can greatly eliminate the block artifact.

Abstract: The paper proposes an improved adaptive Gaussian mixture model (GMM) approach with online EM algorithms for updating, which solves the video segmentation problems carried by busy environment and illumination change. Different learning rates are set for foreground district and background district respectively, which improves the convergence speed of background model. A shadow removal scheme is also introduced for extracting complete moving objects. It is based on brightness distortion and chromaticity distortion in RGB color space. Morphological filtering and connected components analysis algorithm are also introduced to process the result of background subtraction. The experiment results show that the improved GMM has good accuracy and high adaptability in video segmentation. It can extract a complete and clear moving object when it is incorporated with shadow removal.

Abstract: The key of wavelet image threshold de-noising is the choice of the threshold function and the threshold value. To overcome the shortcomings of constant deviation existing between estimated wavelet coefficients and decomposition coefficients in the soft threshold function and discontinuity of the hard threshold function, a new threshold function based on wavelet shrinkage in image de-noising is presented in this paper. Threshold values of images with different edges and texture degrees are fine-tuned when the threshold value is set. Furthermore, a self-adaption optimal threshold which is fit to all scale levels is designed based on features of multiscale and multiresolution of wavelet transform. Simulation results show that the proposed methods are efficient to reduce the noise while preserving the detail information of the image.

Abstract: The problem being faced is that the current target recognition method based on color feature can’t filter objects that have the same color as the target object. In this paper, a new target recognition algorithm based on the object’s color and size is introduced. To achieve the goal of object recognition, the HSV color space conversion, the threshold method and seed growth method are used together to implement image segmentation. The size feature has been used to filter the image regions that have been extracted by image segmentation. The method is proved by experimentation to be effective in regular shape object recognition.

Abstract: Wind energy is one of the fast growing sources of renewable power production currently and there is a great demand to reduce the cost of operation and maintenance to achieve competitive energy price in the market especially for offshore wind farms. An offshore wind farm usually comprises a large number of turbines and thus needs a number of service vessels for maintenance. It is already a complicated task to plan the schedule and route for each of the vessels on a daily basis, dealing with several constraints, such as weather window and maintenance demand, at the same time. Even more challenging is to find an optimal solution. This paper propose a method, i.e. Duo Ant Colony Optimization (Duo-ACO), to improve the utilization of the maintenance resources, specifically the efficient scheduling and routing of the maintenance fleet and thus reduce the operation and maintenance (O&M) cost. The proposed metaheuristic method can help operator to avoid a time-consuming process of manually planning the scheduling and routing.

Abstract: In this paper, we discuss consensus problems for a network of dynamic agents with fixed topologies. A consensus algorithm for multi-agent systems with time-varying delay is presented. With the consideration of the effects of network conditions, such as network-induced delays, packet dropouts, mis-sequence, etc., a communication buffer is introduced for avoiding agents’ communication error, and a method for choosing buffer length is proposed. Using this buffer design, received data is rearranged and transferred in the original order. With the presented consensus algorithm, agents’ consensus is well-performance, and all the agents match the average speed finally. Simulation oriented results verify the effectiveness of the proposed algorithm.

Abstract: To solve the problems of low efficiency and inaccurate positions of artificial trial teaching with industrial robots, a path method is developed to precisely control the robots. Based on a study of general and specific DXF file formats and developed in C # programming language, this method proposes a file format converting algorithm to extract the primitive information and optimize the primitives. The set of points optimized will then be transmitted to the robots through Ethernet and conduct the space coordinates calibration to finally generate robot path codes. Simulations and welding experiments prove that the method will greatly reduce the artificial trial teaching time, improve the working efficiency of robots, and it is adapted to the robots welding, cutting, coating and other trajectory path problems,etc..

Abstract: Considering the contradiction of detection speed and detection accuracy of incremental encoder, a novel digital velocity detection N/S algorithm is proposed in this paper. The algorithm of velocity detection mainly consists of two parts: the pulse sliding counting and velocity synchronous updating. In order to reduce the pulse-detection time delay, the pulse-sliding-counting method is used to count the encoder pulses during the sampling period, and the pulse-pattern sequences are obtained sequentially. In order to improve the accuracy of velocity detection, synchronization of velocity updating and pulse-mode alternation is applied, which reduces the calculation error caused by asynchronization of velocity updating. The experimental results are shown to demonstrate that the measurement speed and measurement accuracy are improved simultaneously by using of the proposed algorithm.