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Transformations and non-degenerate maps

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Science China Mathematics 2005年第Z1期48卷 195-205页

作者： li baokui & WANG Yuefei Institute of Mathematics, Academy of Mathematics and System Sciences, Chinese Academy of Sciences, Beijing 100080, China Graduate School, Chinese Academy of Sciences, Beijing 100080, China Institute of Mathematics Academy of Mathematics and System Sciences Chinese Academy of Sciences Beijing China Graduate School Chinese Academy of Sciences Beijing China

We shall prove the equivalences of a non-degenerate circle-preserving map and a M(o)bius transformation in ^Rn, of a non-degenerate geodesic-preserving map and an isometry in Hn of a non-degenerate line-preserving map and an affine transformation in Rn. That a map is non-degenerate means that the image of the whole space under the map is not a circle, or geodesic or line respectively. These results hold without either injective or surjective, or even continuous assumptions, which are new and of a fundamental nature in geometry.

关键词： M(o)bius transformation, circle-preserving map, non-degenerate map.

Real-time Path Planning and Control of the Unmanned Surface Vessel for Target Tracking and Obstacle Avoidance

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Real-time Path Planning and Control of the Unmanned Surface ...

第43届中国控制会议

作者： baokui li Xiaobo Shi Qing Fei Jiahua li School of Automation Beijing Institute of Technology

In the scenario of tracking the target in vast sea areas by the unmanned surface vessel, a new target tracking method is proposed by combining the pure pursuit method, the improved interfered fluid dynamic system, and model predictive ***, the second-order response model and the steering gear model of the unmanned surface vessel are established. Then, to complete the task of tracking the moving target while avoiding static or dynamic obstacles, adaptive parameters are introduced into the traditional interfered fluid dynamic system. Furthermore, the improved algorithm is combined with the pure pursuit method to plan a collision-free path. Finally, the external disturbances suffered by the unmanned surface vessel are simplified as disturbances at the steering gear, and a disturbance observer is introduced based on model predictive control to improve the antidisturbance ability of the system. Numerical simulation experiments verify the effectiveness of the proposed method.

关键词： Pure Pursuit method Interfered Fluid Dynamic System algorithm Disturbance Observer Model Predictive Control

Path Tracking Control for the Docking of Unmanned Surface Vessel

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Path Tracking Control for the Docking of Unmanned Surface Ve...

第43届中国控制会议

作者： Xiaobo Shi baokui li Qing Fei Yijia Zhang School of Automation Beijing Institute of Technology

Avoiding collision between the unmanned surface vessel(USV) and the compartment of the mother ship is an important issue during the process of autonomous docking of the USV. To address this challenge, a new path-tracking control strategy utilized for the USV docking is proposed in this paper. Firstly, a geometric constraint model based on the lateral and yaw angle tracking errors is established for the docking scenario, and both the path curvature and the distance from the USV to the docking compartment are introduced to the design of the surge velocity. Then, the unmeasurable velocities and the lumped disturbances are estimated by using an extended state observer, and an adaptive super-twisting sliding mode controller is designed to improve the path-tracking accuracy and anti-disturbance ability. Finally, the effectiveness and the robustness of the controller are verified through numerical simulation.

关键词： USV Docking Extended State Observer Super-twisting Sliding Mode Control Path Tracking Control

Vision Based Real-time High-accuracy Automatic Counting with Applications for Smart Pharmacy

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Vision Based Real-time High-accuracy Automatic Counting with...

第40届中国控制会议

作者： Haotian Wu YuRan Wang Hongbin Ma baokui li Ying Jin Beijing Institute of Technology

At present, many industrial applications urgently need a real-time high-accuracy automatic counting algorithm to realize the counting function of various objects. Some scholars are studying the use of deep learning algorithms to count objects in industrial applications. However, facing closely arranged and different objects, deep learning algorithms cannot achieve this function. Aiming at the application background of regular cuboids counting with a wide range of requirements, this paper provides a real-time high-accuracy automatic counting algorithm based on a deep understanding of the scene and a comprehensive use of multiple computer vision technologies. The algorithm can meet the stringent requirements of industrial applications and realize real-time high-accuracy automatic counting of closely arranged cuboids. And there is no requirement for whether the surfaces of the cuboids are the same, and there is no need to prepare the template pictures of the cuboids in advance. The algorithm mainly uses the characteristics of gaps between cuboids, and adopts improved Hough line detection to identify gaps,and finally realizes the counting function. The algorithm proposed in this paper has been verified on the counting of pillboxes in the industrial application of smart pharmacies. Compared with the deep learning algorithm, it has the characteristics of good interpretability, good generalization, fast speed and high accuracy.

关键词： Computer vision Real-time high-accuracy automatic counting Improved Hough line detection Smart pharmacy

Research on Unmanned Surface Vessel for Meteorological Detection

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Research on Unmanned Surface Vessel for Meteorological Detec...

第40届中国控制会议

作者： Changwen Wu baokui li Qing Fei Xiaosong Huang Xuyang Fang School of Automation Beijing Institute of Technology Institute of Atmospheric Physics Chinese Academy of Sciences

Marine meteorology information is important for weather-sensitive marine activities while it is difficult to collect meteorological data in harsh environments. The objective of this paper is to design an unmanned surface vessel（USV） system,which consists of several subsystems, for marine meteorological data acquisition. Taking into consideration the reliability of the self-driving subsystem, a redundant autonomous driving module is designed to remove the broken controller. The stability and reliability of data transmissions are guaranteed by a multi-mode communication subsystem composed of radio and Beidou satellite communication modules. For the sake of the vessel safety, a navigation obstacle avoidance subsystem is employed in combination with vision sensors. The power subsystem including diesel generators and batteries is designed to extend the working time of meteorological monitoring. Moreover, an adaptive circular LOS guidance law is proposed to reduce the overshoot caused by the disturbance due to wind and wave. Finally, several experiments are conducted to validate the effectiveness of the system. The results show that the USV with designed system is able to sail across the tough marine area while showing important advantages for the acquisition and transmission of marine meteorological data in real time.

关键词： Unmanned Surface vessel Control System Marine Weather Data Acquisition Guidance Law

High Precise Attitude Updating Algorithm for SINS using Angular Rate

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High Precise Attitude Updating Algorithm for SINS using Angu...

第24届中国控制与决策会议

作者： Nan li 1 , Qingbo Geng 1 , baokui li 1 , Qing Fei 1 1. School of Automation, Beijing Institute of Technology, Beijing 100081

In strap-down inertial navigation system (SINS), the attitude updating algorithms using angular rate have superior performance than conventional ones using angular increment for modern-day gyro whose output is angular rate. However, most of them are obtained by omitting the higher order cross product in the rotation vector differential equation, which leads to degrade the accuracy of algorithms inevitably and cannot restrain noncommutativity error in the high dynamic condition. Due to the limitation on the computer performance and modern-day gyro technology, it is impossible to increase sample numbers and update frequency infinitely for the purpose of improving the attitude accuracy. To solve this problem, the new algorithm deducted by adding the higher order cross item is proposed. Simulations are carried on under coning motion. While angular rate is used as algorithm input, the accuracy and stability of attitude computation can be improved effectively as compared with conventional ones and others using angular rate.

关键词： Algorithm Attitude Rotation Vector SINS

20CrMnMo钢渗碳后端淬试验的硬度分析

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金属热处理 2019年第5期44卷 210-214页

作者：王鑫李宝奎顾敏李双喜郑州机械研究所有限公司河南郑州450001 河南工程学院机械工程学院河南郑州451191

运用端淬曲线模型对渗碳端淬试样的硬度场进行了模拟分析,首先拟合出不同碳含量下的端淬硬度曲线,然后通过温度场的分析得到特定温度区间的冷却曲线,最终实现了渗碳端淬试样硬度的分层模拟和云图显示。通过与试验结果对比,硬度分析结果... 详细信息

运用端淬曲线模型对渗碳端淬试样的硬度场进行了模拟分析,首先拟合出不同碳含量下的端淬硬度曲线,然后通过温度场的分析得到特定温度区间的冷却曲线,最终实现了渗碳端淬试样硬度的分层模拟和云图显示。通过与试验结果对比,硬度分析结果具有较好的准确性,尤其是在端淬距离较小时,其余位置最大误差在5. 6 HRC以内。

关键词：渗碳端淬试验端淬曲线温度场分层模拟

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基于有限元分析的大型渗碳齿轮轴畸变控制

金属热处理 2019年第4期44卷 239-242页

作者：王鑫李宝奎顾敏李双喜郑州机械研究所有限公司河南郑州450001 河南工程学院机械工程学院河南郑州451191

针对传统油淬工艺不能满足大型齿轮轴畸变要求的情况,运用有限元分析手段找到畸变原因。然后通过改进加热方法和使用盐浴分级淬火工艺,使齿轮轴的畸变大大减小,轮齿中部凹陷量减小至1.41 mm,翘曲减至0.9 mm,能够满足齿轮轴渗碳淬火畸变... 详细信息

针对传统油淬工艺不能满足大型齿轮轴畸变要求的情况,运用有限元分析手段找到畸变原因。然后通过改进加热方法和使用盐浴分级淬火工艺,使齿轮轴的畸变大大减小,轮齿中部凹陷量减小至1.41 mm,翘曲减至0.9 mm,能够满足齿轮轴渗碳淬火畸变的技术要求,改善了后期精加工的齿面渗层不均匀现象,大大减少了精加工成本。

关键词：齿轮轴畸变控制盐浴凹陷量

温度和表面粗糙度对40CrNiMo钢离子渗氮的影响

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金属热处理 2019年第6期44卷 201-203页

作者：李双喜李宝奎李晓丹顾敏郑州机械研究所有限公司

对相同预处理状态、不同表面粗糙度的40CrNiMo试样进行不同温度的离子渗氮,然后对渗氮层厚度及渗层组织进行测评。结果发现:渗氮温度≤550℃,其它渗氮条件相同时,渗速、白亮层厚度、渗氮层疏松都随着粗糙度的增加而稍有增加;当渗氮温度... 详细信息

对相同预处理状态、不同表面粗糙度的40CrNiMo试样进行不同温度的离子渗氮,然后对渗氮层厚度及渗层组织进行测评。结果发现:渗氮温度≤550℃,其它渗氮条件相同时,渗速、白亮层厚度、渗氮层疏松都随着粗糙度的增加而稍有增加;当渗氮温度为570℃时,粗糙度为0.2μm的试样渗氮效果最好,渗速、白亮层厚度达到最大,渗氮层疏松为1级;而后,渗速、白亮层厚度随着粗糙度的增加而降低,渗氮层疏松却不断增加,在R_a=3.2μm试样上出现大量疏松层脱落现象。

关键词： 40CrNiMo钢离子渗氮粗糙度疏松