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Long Z.,Harbin Institute of Technology | Long Z.,Shenzhen Key Laboratory for Advanced Motion Control and Modern Automation Equipments | Yu X.,Harbin Institute of Technology | Yu X.,Huazhong University of Science and Technology | Zhu C.,Harbin Institute of Technology
Zhongguo Jixie Gongcheng/China Mechanical Engineering

Stable and fast switching between displacement and pressure will directly affect precision and velocity of automated equipment. To solve the shortage of direct switching between displacement and pressure, switching control between displacement and pressure was proposed for motion switching of automated equipment, which was based on the velocity damping. The damping was changed with the parameters of velocity ring. So this control can realize stable switching between displacement and pressure. This control can suppress vibration in the process of pressure loading. Compared to direct switching control, the proposed switching control becomes more accurate and faster. The measurement data shows that the amplitude of forces of fluctuations are within the range of ±0.3 N. Source

Wu X.,Harbin Institute of Technology | Wu X.,Shenzhen Key Laboratory for Advanced Motion Control and Modern Automation Equipments | Wen F.,Harbin Institute of Technology | Wen P.,Guilin University of Electronic Technology
Jisuanji Fuzhu Sheji Yu Tuxingxue Xuebao/Journal of Computer-Aided Design and Computer Graphics

To solve the surface reconstruction problem in weak texture or textureless and specular area in multi-view stereo (MVS), a novel hole-filling method is presented for MVS surface reconstruction based on visual hull and depth map fusion. The visual hull and 3D point cloud are taken as input data for fusion. Firstly we extract the voxels that are satisfied the sparsity constraint of 3D point cloud from visual hull, and then in order to get rid of the outer leaf nodes, the constraint of visual hull surface normal and rays is employed. Finally, mean curvature of the surface model is used to eliminate the influence to concave area. The proposed approach has been implemented and the performance of the approach is demonstrated on several real datasets. The results show that it is an effective way to restore the textureless and occluded surfaces of the object. And our algorithm is simple to implement, parameters tunable and robust for different models. Source

Lou Y.,Shenzhen Key Laboratory for Advanced Motion Control and Modern Automation Equipments | Meng H.,Shenzhen Key Laboratory for Advanced Motion Control and Modern Automation Equipments | Yang J.,Huazhong University of Science and Technology | Li Z.,Huazhong University of Science and Technology | And 3 more authors.
IEEE Transactions on Industrial Electronics

Contouring control is crucial in high-speed and high-precision manufacturing. In this paper, a novel task polar coordinate frame (TPCF), moving along the desired contour, is proposed to naturally calculate and control the estimated contouring error by the circular approximation, a second-order approximation. The dynamics in the world Cartesian coordinate frame is transformed into radial and angular dynamics in the local polar coordinate frame. By the feedback linearization technique and an input feedforward compensation, the closed-loop dynamics are decoupled in terms of the estimated contouring error and the angular error, respectively. Proportional-plus- derivative controllers can be assigned to stabilize the individual axis dynamics in the TPCF. By tuning the control parameters, different strengthening on estimated contouring error and angular error can be imposed explicitly and directly. Various experiments on an XY-stage biaxial system with typical contours, a circle and a figure-'8,' were conducted. Comparative studies are carried out for the TPCF- and traditional Frenet frame-based controls. The contouring errors were drastically reduced by the proposed approach, particularly in high-speed and large-curvature contouring cases. © 1982-2012 IEEE. Source

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