Sun Han-xu

Beijing University of Posts and Telecommunications, Peping, Beijing, China

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Publications (15)0 Total impact

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    ABSTRACT: To solve the problem of multi-camera calibration, an algorithm is brought forward based on coplanar projection of points. A coordinate system is unified between world coordinates and projective plane ones. After feature patterns projected onto a planar screen and corners extracted from images, each camera is calibrated respectively, from which it can obtain internal parameters and relative poses among cameras. Initial values of spatial points are derived from projective transformation. Then it finds out corresponding points of each image pair by epipolar geometry constraint and calculates spatial points in terms of triangle principle again. Root mean square error between initial values and estimation values are calculated. Furthermore, it eliminates points until errors of all spatial points within threshold. The experimental analyses indicate that the algorithm can reduce computational complexity and manual intervention. Calibration accuracy can meet the need.
    01/2010;
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    ABSTRACT: A spatial position analysis algorithm for multi-target tracking is proposed in multiple views. A target centroid marked is obtained from the zero and the first moments. Data association between a centroid and a trajectory exploits fuzzy C-mean clustering algorithm. Positions of moving targets are calculated by triangle principles in stereo vision. Furthermore, back projections from a three-dimensional point to a camera plane in each view angle are compared to the centroid in order to obtain RMS error. Experimental results indicate the method can reduce computational complexity and also be robust to occlusion, which can meet actual needs.
    01/2010;
  • Chu Ming, Jia Qing-xuan, Sun Han-xu
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    ABSTRACT: In this study, based on differential geometry input-output linearization method, a new robust control approach using global terminal sliding mode (GTSM) was developed for trajectory tracking and vibraton suppression of two-link flexible space manipulator, and the nonminimum phase control problem was solved. Firstly, the system outputs including joint angle and flexible-link vibration were redefined and therefore, the manipulator system was decomposed into input-output subsystem and zero-dynamics subsystem by input-output linearization. Secondly, in order to make the tracking error of input-output subsystem fast convergence to zero in finite time, a GTSM control strategy was designed, which was able to eliminate significantly the chattering inherent in conventional sliding mode control. Moreover, by analyzing the relationship between the eigenvalues of zero-dynamics and the parameters of controller, the zero-dynamics can be quickly and asymptotically stable at equilibrium point by choosing proper parameters. Consequently, the whole original manipulator system was guaranteed to be asymptotically stable. Finally, the presented numerical simulation results demonstrated the effectiveness and feasibility of the proposed control program.
    Intelligent Computing and Intelligent Systems, 2009. ICIS 2009. IEEE International Conference on; 12/2009
  • Jia Qing-xuan, Chu Ming, Sun Han-xu
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    ABSTRACT: The partial dynamics equations (PDE) of space manipulator with flexible-joint and flexible-link are modelled using the second Lagrange method. Then, the unstable quality of the conventional numerical integration methods under Lagrange system are appropriately proved through energy analysis; therefore, the precise integration method (PIM) under Hamilton system is adopted to solve the strictly stiff PDE owing to rigidness/flexibility coupling matter. The difficulty of transformation from Lagrange to Hamilton system is discussed when damping matrix is considered; and then, the state space vector method is introduced in order to obtain the Hamilton's equivalence form. The limitation of traditional PIM is pointed out and then a new dimension expanding PIM is presented, which converts the nonhomogeneous equations to homogeneous ones and avoids the inverse matrix calculation. Finally, the highly precise numerical results are acquired by computor simulation.
    Intelligent Computation Technology and Automation, 2009. ICICTA '09. Second International Conference on; 11/2009
  • Chu Ming, Jia Qing-xuan, Sun Han-xu
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    ABSTRACT: A new combination method for the robust high precision position control of flexible joint with nonlinear friction and uncertainties compensation is proposed in this paper. The global control system is designed based on backstepping like technique in order to suppress the flexibility and disturbance, and the wavelet neural networks approach is utilized especially to estimate the nonlinear terms including friction and uncertainties locally without predicting the upper bound. From the Lyapunov stability analysis, adaptive laws which are used to update the network weights are induced. The stability of the overall closed loop system is proved to be UUB stable. Finally, the computor simulation results show the good position tracking performance and robustness of the proposed control strategy.
    Intelligent Computation Technology and Automation, International Conference on. 10/2009; 1:878-883.
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    ABSTRACT: The paper describes a method for compression of geometry data stream in distributed parallel rendering systems. First this paper uses edge collapse method with discrete curvature error metric to construct multi-resolution models, and use variable quantization of precision to compression 3-dimensional models; then models were provided to view-dependent progressive transmission method to deal with, and implement it with a distributed parallel rendering system for virtual manufacturing; While this paper use the parallelogram prediction of vertex coordinates and the angular space within one sextant of normal to compress 3-dimensional models, alleviating network bandwidth bottleneck.
    Industrial Electronics and Applications, 2009. ICIEA 2009. 4th IEEE Conference on; 06/2009
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    ABSTRACT: The paper describes a framework for time-critical rendering of graphics scenes composed of a large number of objects having complex geometric descriptions. An algorithm for mesh simplification both view-independent and view-dependent for original complex model was presented in this paper, First this paper uses edge collapse method with discrete curvature error metric to construct multi-resolution models, then simplified models were provided to view-dependent progressive transmission method to deal with, and implement it with a immediate-mode/retained-mode hybrid distributed parallel rendering system for virtual manufacturing; While this paper use the algorithm called geometry indexing that avoids the redundant geometry transmission by indexing geometry data, alleviating network bandwidth bottleneck.
    Industrial Electronics and Applications, 2009. ICIEA 2009. 4th IEEE Conference on; 06/2009
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    ABSTRACT: Multi-projector virtual environment based on PC cluster has characteristics of low cost, high resolution and widely visual angle, which has become a research hotspot in virtual reality application. Geometric distortion calibration and seamless splicing is key problems in multi-projector display. The paper does research on geometry calibration method and edge blending. It proposes an automatic calibration preprocessing algorithm based on a camera, which projects images to the regions expected in terms of the relation between a plane surface and a curved surface and texture mapping method. In addition, overlap regions, which bring about intensity imbalance regions, may be adjusted by an edge blending function. Implementation indicates that the approach can accomplish geometry calibration and edge blending on an annular screen.
    Informatics in Control, Automation and Robotics, 2009. CAR '09. International Asia Conference on; 03/2009
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    ABSTRACT: The application of virtual environments (VEs) to the product design and development process has intrigued researchers and practitioners in industry, government, and academia in recent years. To meet the characteristics and the requirements of virtual design, VDPR, a distributed parallel rendering software infrastructure, which combines the advantages of immediate-mode frame and retained-mode frame, is put forward in this paper. By transmitting the model operation event rather than the modified model from master node to the render node, the network bandwidth is freed from unnecessary transmission of excessive graphics commands and data, and the mix-mode frame decreases the network communication flux greatly. Furthermore, the application can implement efficient dynamic database updates based on distributed objects and capture the face data of product model for rendering from the client application. The problems including software architecture of parallel rendering systems, alignment of projectors, synchronization of displays in distributed parallel rendering systems and so on are investigated in detail in this paper. Finally, overall display performance is given. The aim of constructing the display system is to build a large-scale, high resolution, immersive virtual environment supporting users' collaboration for virtual design, and it shows great promise for manufacturing industry to raise productivity, improve product quality, shorten lead times, reduce costs and improve competition ability in a global environment.
    01/2009;
  • Jia Qing-xuan, Chu Ming, Sun Han-xu
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    ABSTRACT: In this paper, the operational mode coupled controller analysis theory and method for space flexible-joint flexible-link (FJFL) manipulator is proposed completely, and the coupling problem of control and structure is solved. Firstly, the vibration partial differential equation (PDE) based on the Rayleigh-Ritz method is modelled; then, the complicated boundary condition including joint rigidity and controller gain parameters is obtained via state feedback constraint and bending moment balance modus. In order to solve the operational mode frequency and shape function, the Laplace transform and complex mode approach are both significantly employed. The solution shows that the controller significantly influence the rigidity and damping coefficients and alters the dynamics response characteristic. Especially, the state feedback of the joint velocity introduces extra structure damping into the system, thus it lowers the natural frequency and makes the phase non-zero, which is extremely different from the conventional vibration features. Finally, a large number of numerical simulations are performed to verify the validity and rationality of the proposed programme.
    01/2009;
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    ABSTRACT: In order to reduce the difficulties and hazards of astronaut's extra vehicular activities(EVA), it's essential for virtual human(VH) software to apply in the studies of kinematics and dynamics simulation for EVA. Jack which used generally cannot realize the dynamic solution for VH motion at the state of weightlessness, and its costliness also reduces the interactive capacity. A concept of VH motion analysis software on VC platform is presented in this paper to solve the above problems. In this software, VH modeling is established on the basis of relative robotics, the algorithms for VH kinematics and dynamics analysis are implemented by standard C programs, and the visual simulation interface is developed by OpenGL on VC platform. The present software can realize the trajectory-planning and joint force/torque solution along the path for VH motion at the state of weightlessness, therefore, it provides reference data applied in digitized analysis of EVA accordingly, furthermore, the lower cost and friendly interface of VC software demonstrate its applicability and interactive capacity to meet the requirements.
    Industrial Electronics and Applications, 2008. ICIEA 2008. 3rd IEEE Conference on; 07/2008
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    ABSTRACT: Binocular stereo vision algorithm is an effective method to position for intra-vehicular robot system(IVRS) quickly and exactly, however, large number of image data and much time cost have brought difficulties to solve the real-time applications of IVRS for the general vision system presently. Therefore, a binocular stereo vision system is designed and developed in this paper for extensive application of space position. Through the establishment of mathematical model, system calibration and homonymy points matching, the high precision object's 3D coordinate for robot system can be acquired. An improved fast matching algorithm is presented for the system. In this algorithm, the aim matching region is greatly reduced through using epipolar constraint mutually between two images, which not only saves the calculate time, but also advances the matching precision, and then the high precision matching solution can be realized by the use of reference difference gradient rule. Finally, design feasibility of binocular stereo vision system is validated by IVRS, meanwhile, the vision system is optimized through error analysis. According to the experiment, it demonstrates the applicability and significance of the system for IVRS positioning.
    01/2008;
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    ABSTRACT: Considering space manipulator modular joint using permanent magnet synchronous motor (PMSM) is easy to be influenced by unknown nonlinearities, external disturbances and parameter perturbations in practical servo control system. In order to improve accuracy of trajectory tracking, integral backstepping sliding-mode control system was designed to compensate the uncertainties. To confirm the upper bound of uncertainties in sliding-mode control system, general Radial Basis Function Network (RBFN) was adopted to estimate the value of upper bound based on the stability of Lyapunov theorem. The results of simulation demonstrate that this method improves the performances of trajectory tracking and enhances the robustness to friction nonlinearities and external disturbances.
    Information Acquisition, 2007. ICIA '07. International Conference on; 08/2007
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    ABSTRACT: The research on geckos' adhesion states that the force of geckos' foot hairs adhering to the substrate is van der Waals force. Based on the research of the geckos' hairs, we assure two of models: single gecko spatula adhesive dynamical model and single gecko spatula pulling-off adhesive surfaces' dynamical model. These theoretical models contribute to the synthetic geckos' foot hairs manufacturing and provide the theoretical instruction to the manufacturing. Using design of the robot foots which are used by the synthetic geckos' adhesion technology, the climbing performance for the robot will be improved greatly
    Robotics, Automation and Mechatronics, 2006 IEEE Conference on; 01/2007
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    ABSTRACT: This paper presents a method for modular robot joint that integrates mechanical part and control system. After the analysis of stress and distortion, it sets up a matrix model with errors. At the same time, PCI adapter and DSP servo controller are designed. The characteristics of the module are tested and analyzed. The main characteristics meet the design target.
    01/2006;