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学者姓名：张立伟
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Abstract ：
Passive vibration isolation techniques with low-frequency characteristics have been a hot topic in the aerospace field. A hydraulic inertial vibration isolator is a highly effective type of isolator for controlling low-frequency vibrations. It typically consists of a main spring, a minor spring, an inertial mass, and a fluid domain. Due to its multi-domain nature, analyzing the isolation mechanism of this type of isolator is challenging. The bond graph method is employed to establish the dynamic model of the isolator. Subsequently, the state equations of the isolator are derived, and the energy equations of both the mechanical and the fluid parts of the isolator are obtained. Based on this, the energy transfer characteristics between the mechanical and fluid domains inside the isolator under external excitation are discussed. The time-domain response of the forces transmitted to the foundation is analyzed. It is shown that the anti-resonance frequency occurs when the forces transmitted to the foundation generated by the main spring and the fluid pressure are equal to that of the minor spring. To verify the proposed method's correctness, a prototype of the isolator is designed and a carefully designed experiment is conducted. The acceleration transmissibility of the isolator is used to conduct a comparative study. The results show that the theoretical results are in good agreement with the experimental results. To depict the dynamic characteristics of the isolator under large amplitude vibration, the nonlinear dynamic model of the isolator is developed, and the corresponding force transmissibility of the isolator is formulated. The energy flow between the mechanical and the fluid domains under this condition is also analyzed. The results indicate that the energy flow responses exhibit a similar change tendency to the force transmissibility. However, the peak of the energy ratio between the mechanical subsystem and the fluid is the same as the linear condition, suggesting that this value is determined by the amplification ratio of the isolator. This research provides enhanced physical insight to understand the dynamic characteristics of this type of isolator and will help to shorten the design cycle of the isolator.
Keyword ：
acceleration transmissibility acceleration transmissibility bond graph bond graph energy transfer energy transfer hydraulic inertial isolator hydraulic inertial isolator multi-energy-domain multi-energy-domain
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| GB/T 7714 | Liu, Niuniu , Li, Cheng , Zhang, Liwei et al. The Bond Graph Modeling and Experimental Verification of a Hydraulic Inertial Vibration Isolator Including Nonlinear Effects [J]. | AEROSPACE , 2024 , 11 (8) . |
| MLA | Liu, Niuniu et al. "The Bond Graph Modeling and Experimental Verification of a Hydraulic Inertial Vibration Isolator Including Nonlinear Effects" . | AEROSPACE 11 . 8 (2024) . |
| APA | Liu, Niuniu , Li, Cheng , Zhang, Liwei , Lei, Zhiyang , Yang, Jing , Lai, Fuqiang . The Bond Graph Modeling and Experimental Verification of a Hydraulic Inertial Vibration Isolator Including Nonlinear Effects . | AEROSPACE , 2024 , 11 (8) . |
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A lever-enhanced negative stiffness isolator (LENSI) is proposed to attenuate the longitudinal vibration of a shaft-plate coupled system in the low-frequency range. The isolator comprises a rigid lever, an isolator mass and a negative stiffness element, installed in parallel with the thrust bearing. The dynamic model of the shaft-plate coupled system is formulated using the Rayleigh-Ritz method. Longitudinal acceleration frequency response of the bearing pedestal and mean square velocity of the plate are used to evaluate the isolation performance of the proposed isolator. By comparing the isolation performance of LENSI with traditional isolator such as dynamic anti-resonance isolator (DAVI) or absorber such as dynamic vibration absorber with negative stiffness (DVANS), the superiority of the LENSI is demonstrated. A parametric study is presented to clarify the influence of the isolator parameters on its isolation performance. It is shown that the LENSI is capable of isolate the longitudinal vibration of the shaft-plate coupled system with a much lower mass ratio in the low-frequency range.
Keyword ：
Lever-enhanced negative stiffness isolator (LENSI) Lever-enhanced negative stiffness isolator (LENSI) Longitudinal vibration transmission control Longitudinal vibration transmission control Rayleigh-Ritz method Rayleigh-Ritz method Shaft-plate coupled system Shaft-plate coupled system
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| GB/T 7714 | Liu, Niuniu , Lin, Fuming , Lei, Xianliang et al. Longitudinal Vibration Control of A Shaft-plate Coupled System with A Lever-enhanced Negative Stiffness Isolator [J]. | PROCEEDINGS OF THE 2024 3RD INTERNATIONAL SYMPOSIUM ON INTELLIGENT UNMANNED SYSTEMS AND ARTIFICIAL INTELLIGENCE, SIUSAI 2024 , 2024 : 193-198 . |
| MLA | Liu, Niuniu et al. "Longitudinal Vibration Control of A Shaft-plate Coupled System with A Lever-enhanced Negative Stiffness Isolator" . | PROCEEDINGS OF THE 2024 3RD INTERNATIONAL SYMPOSIUM ON INTELLIGENT UNMANNED SYSTEMS AND ARTIFICIAL INTELLIGENCE, SIUSAI 2024 (2024) : 193-198 . |
| APA | Liu, Niuniu , Lin, Fuming , Lei, Xianliang , Zhang, Liwei , Yang, Jing . Longitudinal Vibration Control of A Shaft-plate Coupled System with A Lever-enhanced Negative Stiffness Isolator . | PROCEEDINGS OF THE 2024 3RD INTERNATIONAL SYMPOSIUM ON INTELLIGENT UNMANNED SYSTEMS AND ARTIFICIAL INTELLIGENCE, SIUSAI 2024 , 2024 , 193-198 . |
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PurposeIn order to improve the isolation capability of the longitudinal vibration of the shafting system in the low frequency range, a lever-type isolator with negative stiffness (LTINS) was proposed.MethodsThe LTINS arranged in parallel with the thrust bearing to isolate the longitudinal fluctuating force transmitted from the propeller-shaft to its foundation. The Rayleigh-Ritz method is used to establish the longitudinal dynamic model of the propeller-shaft-LTINS system.ResultsThe force transmissibility of the coupled system is formulated, and computed results are compared with those solutions obtained from the finite element method. A stability analysis is carried out based on the equivalent static and dynamic stiffness of the thrust bearing of the shafting system. A comparison study is conducted to compare the isolation performance of the proposed isolator with the traditional isolator such as the dynamic anti-resonance vibration isolator (DAVI), absorber such as the dynamic vibration absorber (DVA), and dynamic vibration absorber with negative stiffness (DVANS). Parametric optimization is carried out to investigate the impact of the parameters of the LTINS on its isolation performance.ConclusionThe results indicated that the proposed control method can achieve a much wider bandwidth than that of the traditional vibration control scheme with a much smaller mass ratio.
Keyword ：
Axial vibration control Axial vibration control Lever-type isolator with negative stiffness Lever-type isolator with negative stiffness Rayleigh-Ritz method Rayleigh-Ritz method Shafting system Shafting system Thrust bearing Thrust bearing
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| GB/T 7714 | Liu, Niuniu , Lei, Xianliang , Lin, Fuming et al. Longitudinal Vibration Transmission Suppression for Propeller-Shaft System by a Lever-Type Isolator with Negative Stiffness [J]. | JOURNAL OF VIBRATION ENGINEERING & TECHNOLOGIES , 2024 , 12 (SUPPL 1) : 949-965 . |
| MLA | Liu, Niuniu et al. "Longitudinal Vibration Transmission Suppression for Propeller-Shaft System by a Lever-Type Isolator with Negative Stiffness" . | JOURNAL OF VIBRATION ENGINEERING & TECHNOLOGIES 12 . SUPPL 1 (2024) : 949-965 . |
| APA | Liu, Niuniu , Lei, Xianliang , Lin, Fuming , Zhang, Liwei , Yang, Jing . Longitudinal Vibration Transmission Suppression for Propeller-Shaft System by a Lever-Type Isolator with Negative Stiffness . | JOURNAL OF VIBRATION ENGINEERING & TECHNOLOGIES , 2024 , 12 (SUPPL 1) , 949-965 . |
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At present, most of the traditional algorithms for mobile robot autonomous exploration in unknown environments use frontier as a guide and adopt greedy strategies for determining the next exploration target. They generate new frontier as new regions of the map, and thus the cycle repeats itself to finally complete the exploration of unknown environments. In this paper, we propose a region clustering-based approach for autonomous exploration of mobile robots in complex environments. Our approach incorporates the concept of region clustering at its global level based on the current advanced hierarchical exploration framework. The robot is more inclined to finish exploring a certain region of the map first, thereby minimizing the robot’s repetitive exploration of explored regions. Mobile robot autonomous exploration experiments were implemented in our college campus. The experimental results show that the average exploration trajectory length was reduced by 14.03%, and the average exploration time was reduced by 16.15%, respectively. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Keyword ：
Mobile robots Mobile robots
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| GB/T 7714 | Zheng, Haoping , Zhang, Liwei , Chen, Meng . Region Clustering for Mobile Robot Autonomous Exploration in Unknown Environment [C] . 2023 : 371-388 . |
| MLA | Zheng, Haoping et al. "Region Clustering for Mobile Robot Autonomous Exploration in Unknown Environment" . (2023) : 371-388 . |
| APA | Zheng, Haoping , Zhang, Liwei , Chen, Meng . Region Clustering for Mobile Robot Autonomous Exploration in Unknown Environment . (2023) : 371-388 . |
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The processing of 3D point clouds from laser scanning is still challenging in self-driving perception and positioning community. Ground segmentation is the key topic, splitting out the ground point cloud effectively reduces the amount of data and increases the speed of subsequent point cloud clustering and feature point extraction. The ground points segmented in SLAM can be used as constraints for back-end optimisation, improving the accuracy of map building and localisation. After the ground segmentation is completed, it can be used as a passable area for vehicle path planning. Existing approaches are based on the assumption that the ground is plane, but unfortunately the ground is not a plane, with a large number of slopes, roadsides, and parts of the ground even rugged and full of obstacles. In order to solve the ground segmentation problem, this paper proposes a ground segmentation method based on polar grid. The main contributions of this paper include: (1) We divide a frame of point cloud space into several regions, each of which is divided into several grids, based on the scanning characteristics of the LIDAR. (2) The plane was fitted based on the improved RANSAC algorithm for each of the previously divided grids. Experiments with KITTI and campus real environment datasets show that the sensitivity of our proposed method can reach more than 98% and the specificity is below 10%. The proposed algorithm can effectively and correctly separate the ground from the point cloud, even on slopes and the ground with many obstacles. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
Keyword ：
Motion planning Motion planning Optical radar Optical radar
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| GB/T 7714 | Zhou, Jiyang , Zhang, Liwei . Polar Grid Based Point Cloud Ground Segmentation [C] . 2023 : 632-643 . |
| MLA | Zhou, Jiyang et al. "Polar Grid Based Point Cloud Ground Segmentation" . (2023) : 632-643 . |
| APA | Zhou, Jiyang , Zhang, Liwei . Polar Grid Based Point Cloud Ground Segmentation . (2023) : 632-643 . |
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Abstract ：
本发明涉及一种激光SLAM的回环检测方法，步骤1：获取单帧三维点云数据及其同步IMU信息；步骤2：将当前帧点云分割为个单元空间，将单元空间数据分别存入矩阵，以此构建第一描述符；将分割后的点云数据与IMU信息存入B向量，以此构建第二描述符；步骤3：用步骤2所述历史帧的第二描述符构建KDTree；步骤4：用第二描述符进行最近邻搜索，从KDTree中找出n个候选相似帧；将候选相似帧与当前点云根据第一描述符进行匹配，根据匹配结果是否符合阈值判断候选相似帧中是否存在闭环，若存在，得出当前帧与回环帧的相对旋转变化。本发明实现移动机器人在室外场景以及局部路段相似性程度高的场景中精度更高、鲁棒性更强的回环检测以及地图构建方法。
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| GB/T 7714 | 张立伟 , 刘洁琳 , 徐光进 et al. 一种激光SLAM的回环检测方法 : CN202110775299.8[P]. | 2021-07-08 . |
| MLA | 张立伟 et al. "一种激光SLAM的回环检测方法" : CN202110775299.8. | 2021-07-08 . |
| APA | 张立伟 , 刘洁琳 , 徐光进 , 何炳蔚 . 一种激光SLAM的回环检测方法 : CN202110775299.8. | 2021-07-08 . |
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本发明提出基于并行树搜索的桁架装配序列规划方法，包括以下步骤：步骤S1：根据目标桁架结构生成无向图，对各个杆件赋予相应的权重，存储于并行树搜索的主模式中；步骤S2：根据桁架结构建立若干个子模式及对应的根结点，各子模式分别扩展多叉树，逐层生成叶子结点；步骤S3：判断各子模式的最优解是否产生冲突，并由主模式中的判别机制进行选择决策；步骤S4：各子模式将得到的最优叶子结点信息返回主模式，主模式将已连接的杆件对应的序列号设置为不可读状态；步骤S5：子模式逐步扩展到无可扩展的杆件列表时，由主模式判断目标桁架结构是否被完全扩展，由此判断是否结束搜索程序；本发明能够快速有效的获取符合稳定性要求的桁架并行装配序列。
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| GB/T 7714 | 张立伟 , 林晓丹 , 陈睿函 et al. 基于并行树搜索的桁架装配序列规划方法 : CN202110767902.8[P]. | 2021-07-07 . |
| MLA | 张立伟 et al. "基于并行树搜索的桁架装配序列规划方法" : CN202110767902.8. | 2021-07-07 . |
| APA | 张立伟 , 林晓丹 , 陈睿函 , 何炳蔚 . 基于并行树搜索的桁架装配序列规划方法 : CN202110767902.8. | 2021-07-07 . |
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Barcode detection is a key step before decoding so that achieving a fast and accurate detection algorithm is of significant importance. In the present study, we propose to guide the pruning of channels and shortcut layers in YOLOv4 through sparse training to obtain the compressed model ThinYOLOv4 for barcode detection. Then a binary classification network is established to remove the prediction boxes that do not contain a barcode, thereby obtaining a fast and accurate barcode detection model. In order to evaluate the performance of the proposed method, a barcode dataset consisting of 16,545 images is provided. This dataset contains common types of barcodes in the market and covers different practical scenarios. Furthermore, interference factors such as blur, low-contrast are considered in the dataset purposefully. Obtained results show that the proposed method achieves a recall rate of 93.8% on the provided dataset, Meanwhile, parameters of YOLOv4 are reduced from 63,943,071 to 400,649, and the model size is reduced from 250,037 KB to 1,587 KB, while the corresponding detection speed is increased to 260% of YOLOv4. When the experiment is performed on the 1050Ti GPU, a detection speed of 23.308 ms/image is achieved. © 2021, Springer Nature Singapore Pte Ltd.
Keyword ：
Bar codes Bar codes Cognitive systems Cognitive systems Signal processing Signal processing
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| GB/T 7714 | Zhang, Liwei , Sui, Yuzhao , Zhu, Fuwei et al. Fast Barcode Detection Method Based on ThinYOLOv4 [C] . 2021 : 41-55 . |
| MLA | Zhang, Liwei et al. "Fast Barcode Detection Method Based on ThinYOLOv4" . (2021) : 41-55 . |
| APA | Zhang, Liwei , Sui, Yuzhao , Zhu, Fuwei , Zhu, Mingzhu , He, Bingwei , Deng, Zhen . Fast Barcode Detection Method Based on ThinYOLOv4 . (2021) : 41-55 . |
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Rapidly-exploring Random Tree (RRT) algorithm is widely used in path planning, while the RRT is inefficient for robotic exploration in large-scale environments with multi-obstacles and narrow entrances. Here, we propose a Hybrid Frontier Detection (HFD) strategy for autonomous exploration which incorporates a variable step-size random tree global frontier detector, a multi-root nodes random tree frontier detector, and a grid-based frontier detector algorithm. The proposed strategy enables a robot to quickly search for the frontier in real-time. Compared with the traditional RRT-based strategy, the exploration time and traveling length of the proposed HFD strategy are respectively decreased by over 15% and 12% in the simulation environment and decreased by over 14% and 11% under the same experimental conditions in the experimental environment. The results indicate that the HFD strategy effectively solves the problem of autonomous exploration in the environment with multi-obstacles and narrow entrances. © 2021 IEEE.
Keyword ：
Motion planning Motion planning Robotics Robotics Robot programming Robot programming Robots Robots Trees (mathematics) Trees (mathematics)
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| GB/T 7714 | Xu, Guangjin , Zhang, Liwei , Chen, Meng et al. Hybrid Frontier Detection Strategy for Autonomous Exploration in Multi-obstacles Environment [C] . 2021 : 1909-1915 . |
| MLA | Xu, Guangjin et al. "Hybrid Frontier Detection Strategy for Autonomous Exploration in Multi-obstacles Environment" . (2021) : 1909-1915 . |
| APA | Xu, Guangjin , Zhang, Liwei , Chen, Meng , He, Bingwei . Hybrid Frontier Detection Strategy for Autonomous Exploration in Multi-obstacles Environment . (2021) : 1909-1915 . |
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The key of robots operating autonomously in dynamic environments is understanding the dynamic characteristics of objects. This paper aims to detect dynamic objects and reconstruct 3D static maps from consecutive scans of scenes. Our work starts from an encode-decode network, which receives two range maps provided by a Velodyne HDL-64 laser scanner and outputs dynamic probability of each point. Since the soft segmentation produced by the network tends to be smooth, a 3D fully connected CRF (Conditional Random Field) is proposed to improve the segmentation performance. Experiments on both the public datasets and real-word platform demonstrate the effectiveness of our method.
Keyword ：
CRF CRF Dynamic objects detection Dynamic objects detection Encode-decode network Encode-decode network Robot vision Robot vision Static maps reconstruction Static maps reconstruction
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| GB/T 7714 | Zou, Cheng , He, Bingwei , Zhu, Mingzhu et al. Encode-decode network with fully connected CRF for dynamic objects detection and static maps reconstruction [J]. | SIGNAL PROCESSING-IMAGE COMMUNICATION , 2021 , 95 . |
| MLA | Zou, Cheng et al. "Encode-decode network with fully connected CRF for dynamic objects detection and static maps reconstruction" . | SIGNAL PROCESSING-IMAGE COMMUNICATION 95 (2021) . |
| APA | Zou, Cheng , He, Bingwei , Zhu, Mingzhu , Zhang, Liwei , Zhang, Jianwei . Encode-decode network with fully connected CRF for dynamic objects detection and static maps reconstruction . | SIGNAL PROCESSING-IMAGE COMMUNICATION , 2021 , 95 . |
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