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Zhaoqin Wang,Xiaorong Wang,Xiaoqin Liu,Yusen Wang,Chengyu Li,Tiesong Lin,Peng He 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.9
Common 3-axis CNC milling machines are generally equipped with 2D tool radius compensation (2D-TRC), which can realize TRC function for the contours in three basic planes when flat end mills are used. The 2D-TRC function makes engineers to program according to the actual contour of a part, and avoids over-cut phenomenon. Unfortunately, the 2D-TRC is unsuitable for ball end mills (BEMs), especially in the situation of milling complex curves or surfaces. In this work, a new TRC named BEM-TRC is used for milling NURBS curve swept surfaces using BEMs based on 3-axis CNC milling machines. In BEM-TRC, the TRC of a BEM involves radial and axial compensation. The cutting point (CP), which is the tangent point between a BEM and a NURBS curve, is considered as a calculation basis point. After obtaining a CP on a NURBS curve using the equi-arc length bisection interpolation method, the cutter center point of a BEM is calculated through off setting the CP the radius ( r ) distance of the BEM along its normal vector. Then the cutter location point of the BEM can be obtained according to the cutter center point. The CNC finishing program corresponding to the cutter location point can be obtained using Matlab software. The simulation based on VERICUT and machining based on a 3-axis milling machine verifies the effectiveness of the BEM-TRC. The over-cut phenomenon is avoided successfully when the BEM-TRC is used.
A Quasi Single Stage Isolated Buck-Boost Mode Multi-input Inverter
Jiahui Jiang,Zhaoqin Li,Daolian Chen 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
Aiming at shortcomings of single new energy power generation, such as unstable power supply, discontinuity and changing with climate conditions, a quasisingle-stage isolated Buck-Boost mode multi-input inverter and master-slave power management SPWM control strategy with smooth and seamless switching in different power supply modes are proposed. The circuit topology, characteristic of steady principle and power management strategy are fully investigated. The circuit topology is composed of a bidirectional isolated Buck-Boost DC converter with a multi-input selector switch in series, and a polarity inversion bridge. The master-slave power management strategy is consisted of n-1 input voltage control loops, n power distribution circuits and instantaneous output voltage control loop with independent power control, it can realize smooth and seamless switching in different power supply modes. Designed and implemented 500VA 80-110VDC/220V50HzAC prototype has excellent performances such as high conversion efficiency, high quality of output waveforms, strong load adaptability, smooth and seamless switching in different power supply modes, etc.