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Real-time Bezier interpolation satisfying chord error constraint for CNC tool path

Science China(Technological Sciences) 2016年第2期59卷 203-213页

作者： FAN Wei LEE ChenHan CHEN JiHong XIAO Yao National NC System Engineering Research Center Huazhong University of Science and Technology Institute of Mechanical Manufacturing Technology China Academy of Engineering Physics Aerospace Engineering Department Zhejiang University

G01 code generated by a computer-aided manufacture （CAM） system is the most common form of tool trajeclory in computer numerical control （CNC） machining. A tool path composed of short line segments has discontinuous tangenc t and curvature, generating large fluctuations of feedrate and acceleration, which in turn produces vibration in a machine tool. To obtain a smooth tool path, many methods on tool-path smoothing have been developed. However, the shortcomings i：1 these methods exist when they are employed in a CNC system. It is difficult to simultaneously to guarantee the following requirements of CNC machining：（1） chord error should be rigidly constrained; （2） G01 points should be interpolated; （3） cur,,ature should be continuous （G2）; （4） machining should be applicable to spatial cases; （5） real-time performance of computaEion is *** on these various requirements, this study proposes an interpolation scheme using CUDlC t^ezler curves anu mciuucb illl adjustment strategy to eliminate deficiencies in the tool path. The tool path generated is G2, chord-elror-constrained, G01-point-interpolated, loop-free, and optimized for both stretch and jerk energy. The method is applicable ：o 3D cases and involves only simple algebraic computations. Thus, the algorithm can be applied to real-time CNC machining. A simulation is conducted to validate the efficiency of the algorithm. In addition, an experiment reveals its advantage over Hermite interpola- tion in surface quality and machining efficiency.

关键词： real-time CNC machining stretch energy jerk energy loop-free chord error

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REDUCING BURST PACKET LOSS THROUGH ROUTE-free FORWARDING

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Journal of Electronics(China) 2010年第3期27卷 363-370页

作者： Ma Hailong Guo Yunfei Cheng Dongnian Zhang Jianwei National Digital Switching System Engineering and Technology Research Center Zhengzhou 450002 China School of Computer Science and Communication Engineering Zhengzhou University of Light Industry Zhengzhou 450002 China

It is well known that today's inter-domain routing protocol, Border Gateway Protocol (BGP), converges slowly during network failures. Due to the distribution nature of Internet routing decisions and the rate-limiting timer Minimum Route Advertisement Interval (MRAI) of BGP, unavoidable convergence latency is introduced in reaction to network changes. During the period of convergence temporarily routing table inconsistencies cause short-term routing blackholes and loops which result in widespread temporary burst packet loss. In this paper, we present ROute-free Forwarding (ROFF) - a novel technique for packet delivering continuously during periods of convergence. With slightly modifications on IP packet header and BGP, route loops and blackholes can be avoided. Our preliminary evaluation demonstrates that ROFF succeeds in reducing the number of Autonomous Systems (ASes) which experience burst packet loss and the duration of packet loss.

关键词： Border Gateway Protocol (BGP) loop-free Blackhole Forwarding

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