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学者姓名：蔡力钢
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Abstract ：
基于改进VMD和自适应BSA优化LS-SVM的刀具磨损状态监测方法
Keyword ：
振动信号 振动信号 特征优化 特征优化 变分模态分解 变分模态分解 最小二乘支持向量机 最小二乘支持向量机 回溯搜索算法 回溯搜索算法 刀具状态监测 刀具状态监测
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| GB/T 7714 | 蔡力钢 , 李海波 , 杨聪彬 et al. 基于改进VMD和自适应BSA优化LS-SVM的刀具磨损状态监测方法 [J]. | 蔡力钢 , 2021 , 47 (1) : 10-23 . |
| MLA | 蔡力钢 et al. "基于改进VMD和自适应BSA优化LS-SVM的刀具磨损状态监测方法" . | 蔡力钢 47 . 1 (2021) : 10-23 . |
| APA | 蔡力钢 , 李海波 , 杨聪彬 , 刘志峰 , 赵永胜 , 北京工业大学学报 . 基于改进VMD和自适应BSA优化LS-SVM的刀具磨损状态监测方法 . | 蔡力钢 , 2021 , 47 (1) , 10-23 . |
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Abstract ：
为提高加工过程中刀具磨损状态的识别精度,结合改进的变分模态分解算法(modified variational mode decomposition,MVMD)、自适应回溯搜索算法(adaptive backtracking search algorithm,ABSA)及最小二乘支持向量机(least squares-support vector machine,LS-SVM),提出一种刀具磨损快速识别模型.针对传统信号处理方法存在的模态混叠、噪声敏感等问题,采用瞬时频率均值法预先确定最佳分解模态数,引入降噪型变分模态分解算法进行信号分解;为提高优化效率与自适应性,提出一种改进的自适应回溯搜索算...
Keyword ：
振动信号 振动信号 回溯搜索算法 回溯搜索算法 最小二乘支持向量机 最小二乘支持向量机 变分模态分解 变分模态分解 刀具状态监测 刀具状态监测 特征优化 特征优化
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| GB/T 7714 | 蔡力钢 , 李海波 , 杨聪彬 et al. 基于改进VMD和自适应BSA优化LS-SVM的刀具磨损状态监测方法 [J]. | 北京工业大学学报 , 2021 , 47 (01) : 10-23 . |
| MLA | 蔡力钢 et al. "基于改进VMD和自适应BSA优化LS-SVM的刀具磨损状态监测方法" . | 北京工业大学学报 47 . 01 (2021) : 10-23 . |
| APA | 蔡力钢 , 李海波 , 杨聪彬 , 刘志峰 , 赵永胜 . 基于改进VMD和自适应BSA优化LS-SVM的刀具磨损状态监测方法 . | 北京工业大学学报 , 2021 , 47 (01) , 10-23 . |
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Abstract ：
Computer numerical controlled (CNC) machine tools are comprised of numerous parts mainly connected by bolts. Accurate modeling of the contact stiffness of bolted joints is therefore a crucial element in predicting the dynamic performance of CNC machine tools. This paper presents a contact stiffness model of a bolted joint based on multi-scale theory. The model uses a series of stacked three-dimensional sine waves to describe the multi-scale roughness of the contact surface, and each frequency level is considered to be a single layer of asperities, which are stacked on top of each other. A relationship between the contact area ratio and frequency level can be deduced. Moreover, the contact stiffness at each frequency level can be represented within the model as a spring in series, therefore, the total stiffness is obtained by summing the contact stiffness at each frequency level. An experimental setup consisting of a box-shaped specimen was used to validate the numerical model of the bolted joint for the case of equal bolt pre-tightening forces and relative errors between the multi-scale natural frequencies and experimental frequencies were found to be less than 5.91%. This suggests the multi-scale model can be used to effectively predict the dynamic characteristics of CNC machine tools.
Keyword ：
frequency level frequency level multi-scale theory multi-scale theory dynamic performance dynamic performance CNC machine tool CNC machine tool bolted joint bolted joint
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| GB/T 7714 | Yang, Cheng , Zhao, Yong-Sheng , Liu, Zhi-Feng et al. Stiffness Model of Bolted Joint of Machine Tool Based on Multi-scale Theory [J]. | JOURNAL OF THE CHINESE SOCIETY OF MECHANICAL ENGINEERS , 2020 , 41 (2) : 159-168 . |
| MLA | Yang, Cheng et al. "Stiffness Model of Bolted Joint of Machine Tool Based on Multi-scale Theory" . | JOURNAL OF THE CHINESE SOCIETY OF MECHANICAL ENGINEERS 41 . 2 (2020) : 159-168 . |
| APA | Yang, Cheng , Zhao, Yong-Sheng , Liu, Zhi-Feng , Cai, Li-Gang . Stiffness Model of Bolted Joint of Machine Tool Based on Multi-scale Theory . | JOURNAL OF THE CHINESE SOCIETY OF MECHANICAL ENGINEERS , 2020 , 41 (2) , 159-168 . |
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Abstract ：
Harmonic drive is an indispensable device for robotic joint, and transmission accuracy of harmonic drive is one of its most important performance indexes. Due to the unsystematic research on the accuracy of harmonic drive, the accuracy consistency of harmonic drive is poor, and the prediction accuracy is seriously insufficient. This study focuses on modeling of transmission error system and prediction of transmission accuracy. Through tracing analysis of transmission error of harmonic drive, a transmission error model including manufacturing, assembly and tooth profile error is established. Based on Rayleigh distribution of error sources and considering multi-tooth meshing effect of harmonic drive, the transmission accuracy prediction model is built. Tooth profile error is measured by gear measuring center, dimension error and geometric tolerance are gauged by coordinate measuring machine. The transmission accuracy of three types harmonic drive (SHG14, SHG20 and SHG25) is measured by harmonic transmission error test bench under rated conditions. The comparison results show that the difference between the predicted and experimental values is less than 15%, which proves the validity of the accuracy prediction model. Prediction method play a crucial role for accuracy control of harmonic drive system.
Keyword ：
transmission accuracy transmission accuracy prediction method prediction method harmonic drive harmonic drive sensitivity analysis sensitivity analysis
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| GB/T 7714 | Hu, Qiushi , Liu, Zhifeng , Cai, Ligang et al. RESEARCH ON PREDICTION METHOD OF TRANSMISSION ACCURACY OF HARMONIC DRIVE [C] . 2020 . |
| MLA | Hu, Qiushi et al. "RESEARCH ON PREDICTION METHOD OF TRANSMISSION ACCURACY OF HARMONIC DRIVE" . (2020) . |
| APA | Hu, Qiushi , Liu, Zhifeng , Cai, Ligang , Yang, Congbin , Zhang, Tao , Wang, Guang . RESEARCH ON PREDICTION METHOD OF TRANSMISSION ACCURACY OF HARMONIC DRIVE . (2020) . |
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Abstract ：
During human-robot collaborations (HRC), robot systems must accurately perceive the actions and intentions of humans. The present study proposes the classification of standing postures from standing-pressure images, by which a robot system can predict the intended actions of human workers in an HRC environment. To this end, it explores deep learning based on standing-posture recognition and a multi-recognition algorithm fusion method for HRC. To acquire the pressure-distribution data, ten experimental participants stood on a pressure-sensing floor embedded with thin-film pressure sensors. The pressure data of nine standing postures were obtained from each participant. The human standing postures were discriminated by seven classification algorithms. The results of the best three algorithms were fused using the Dempster-Shafer evidence theory to improve the accuracy and robustness. In a cross-validation test, the best method achieved an average accuracy of 99.96%. The convolutional neural network classifier and data-fusion algorithm can feasibly classify the standing postures of human workers.
Keyword ：
HRC HRC data fusion data fusion convolutional neural network convolutional neural network machine learning machine learning standing-posture recognition standing-posture recognition
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| GB/T 7714 | Li, Guan , Liu, Zhifeng , Cai, Ligang et al. Standing-Posture Recognition in Human-Robot Collaboration Based on Deep Learning and the Dempster-Shafer Evidence Theory [J]. | SENSORS , 2020 , 20 (4) . |
| MLA | Li, Guan et al. "Standing-Posture Recognition in Human-Robot Collaboration Based on Deep Learning and the Dempster-Shafer Evidence Theory" . | SENSORS 20 . 4 (2020) . |
| APA | Li, Guan , Liu, Zhifeng , Cai, Ligang , Yan, Jun . Standing-Posture Recognition in Human-Robot Collaboration Based on Deep Learning and the Dempster-Shafer Evidence Theory . | SENSORS , 2020 , 20 (4) . |
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Abstract ：
The goal of this study was to recognize human standing postures in human-robot collaborations such that the robot can serve the human operator better. An intelligent sensing floor was developed based on a thin-film pressure sensor and a human standing posture dataset was obtained by transforming the pressure data into a pressure image. A human standing posture recognition method based on an improved convolutional neural network is proposed. The results of the experiments demonstrate that a convolutional neural network can be used in the field of pressure images. The proposed method returned a recognition rate of 96.6%. Compared to the traditional neural network, the improved convolutional neural network model has better performance. The study results are expected to be used in standing posture monitoring to provide additional data for a robot in a human-robot collaboration system. © 2020 - IOS Press and the authors. All rights reserved.
Keyword ：
Social robots Social robots Metadata Metadata Convolutional neural networks Convolutional neural networks Floors Floors Convolution Convolution
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| GB/T 7714 | Li, Guan , Liu, Zhifeng , Cai, Ligang et al. Human standing posture recognition based on CNN and pressure floor [J]. | Journal of Computational Methods in Sciences and Engineering , 2020 , 20 (2) : 489-498 . |
| MLA | Li, Guan et al. "Human standing posture recognition based on CNN and pressure floor" . | Journal of Computational Methods in Sciences and Engineering 20 . 2 (2020) : 489-498 . |
| APA | Li, Guan , Liu, Zhifeng , Cai, Ligang , Yan, Jun . Human standing posture recognition based on CNN and pressure floor . | Journal of Computational Methods in Sciences and Engineering , 2020 , 20 (2) , 489-498 . |
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Abstract ：
S-shape acceleration and deceleration are the most widely used flexible acceleration and deceleration method in the current CNC system, but its velocity solution equation contains irrational terms, which create a more complicated solution process. When analyzing the solution process of the S-shape acceleration and deceleration directly, using a traditional numerical solution method, the phenomenon of "solving the interval jump" arises, which is the main reason for low efficiency and poor stability of the solution. According to the S-curve profile and solution, the concept of separating the curve profile recognition from the velocity solution was proposed, and a method of quickly identifying the interval of the solution location was introduced. Through the method mentioned above, the complete acceleration and deceleration curve parameters can be obtained through a one-time plan and a one-time solution, and the solution efficiency and stability are guaranteed; solving the Newton problem depends too much on the initial value of Newton velocity, which not only retains the speed advantage of the Newton method but also uses the downhill factor to ensure its convergence. Through the simulation comparison and analysis, the efficiency, stability, and universality of the method are verified.
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| GB/T 7714 | Li, Zhijie , Cai, Ligang , Liu, Zhifeng . Efficient Planning and Solving Algorithm of S-Shape Acceleration and Deceleration [J]. | WIRELESS COMMUNICATIONS & MOBILE COMPUTING , 2020 , 2020 . |
| MLA | Li, Zhijie et al. "Efficient Planning and Solving Algorithm of S-Shape Acceleration and Deceleration" . | WIRELESS COMMUNICATIONS & MOBILE COMPUTING 2020 (2020) . |
| APA | Li, Zhijie , Cai, Ligang , Liu, Zhifeng . Efficient Planning and Solving Algorithm of S-Shape Acceleration and Deceleration . | WIRELESS COMMUNICATIONS & MOBILE COMPUTING , 2020 , 2020 . |
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Abstract ：
The effect of preload relaxation caused by the mechanical vibration on loosening of bolted joints with self-locking capability has been widely observed. This paper proposed a combination testing strategy involving tightening and relaxation to elucidate the loss mechanism of bolt preload. A logarithmic relationship between torque coefficient and tightening torque is reported based on the results of fastening tests. Two types of specimen were designed to evaluate the preload relaxation under axial and transverse vibration. A time-varying model is proposed for predicting the residual preload of bolts. An orthogonal test involving tightening torque, amplitude, and frequency was conducted. The results show that the relaxation evolution of bolted joints subjected to vibration is similar and can be divided into two stages.
Keyword ：
Torque coefficient Torque coefficient Vibration Vibration Bolted joint Bolted joint Preload relaxation Preload relaxation
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| GB/T 7714 | Li, Ying , Liu, Zhifeng , Wang, Yuezhen et al. Experimental study on behavior of time-related preload relaxation for bolted joints subjected to vibration in different directions [J]. | TRIBOLOGY INTERNATIONAL , 2020 , 142 . |
| MLA | Li, Ying et al. "Experimental study on behavior of time-related preload relaxation for bolted joints subjected to vibration in different directions" . | TRIBOLOGY INTERNATIONAL 142 (2020) . |
| APA | Li, Ying , Liu, Zhifeng , Wang, Yuezhen , Cai, Ligang , Zheng, Mingpo . Experimental study on behavior of time-related preload relaxation for bolted joints subjected to vibration in different directions . | TRIBOLOGY INTERNATIONAL , 2020 , 142 . |
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Abstract ：
Computer numerical controlled (CNC) machine tools are comprised of numerous parts mainly connected by bolts. Accurate modeling of the contact stiffness of bolted joints is therefore a crucial element in predicting the dynamic performance of CNC machine tools. This paper presents a contact stiffness model of a bolted joint based on multi-scale theory. The model uses a series of stacked three-dimensional sine waves to describe the multi-scale roughness of the contact surface, and each frequency level is considered to be a single layer of asperities, which are stacked on top of each other. A relationship between the contact area ratio and frequency level can be deduced. Moreover, the contact stiffness at each frequency level can be represented within the model as a spring in series, therefore, the total stiffness is obtained by summing the contact stiffness at each frequency level. An experimental setup consisting of a box-shaped specimen was used to validate the numerical model of the bolted joint for the case of equal bolt pre-tightening forces and relative errors between the multi-scale natural frequencies and experimental frequencies were found to be less than 5.91%. This suggests the multi-scale model can be used to effectively predict the dynamic characteristics of CNC machine tools. © 2020, Chinese Mechanical Engineering Society. All right reserved.
Keyword ：
Bolted joints Bolted joints Computer control systems Computer control systems Machine tools Machine tools Stiffness Stiffness Bolt tightening Bolt tightening
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| GB/T 7714 | Yang, Cheng , Zhao, Yong-Sheng , Liu, Zhi-Feng et al. Stiffness Model of Bolted Joint of Machine Tool Based on Multi-scale Theory [J]. | Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao , 2020 , 41 (2) : 159-168 . |
| MLA | Yang, Cheng et al. "Stiffness Model of Bolted Joint of Machine Tool Based on Multi-scale Theory" . | Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao 41 . 2 (2020) : 159-168 . |
| APA | Yang, Cheng , Zhao, Yong-Sheng , Liu, Zhi-Feng , Cai, Li-Gang . Stiffness Model of Bolted Joint of Machine Tool Based on Multi-scale Theory . | Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao , 2020 , 41 (2) , 159-168 . |
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Abstract ：
介绍了一种高架桥式重型龙门加工中心横梁从初始构型设计到最终确定板件具体尺寸的优化设计方法,首先针对高架桥式重型龙门加工中心横梁承受随动载荷的工况,以及焊接工艺及操作空间的制造限制条件,建立基于变密度法SIMP插值的拓扑优化数学模型,采用启发式调整法对变量进行迭代更新的优化准则法(optimality criteria,OC)算法,利用灵敏度过滤技术抑制棋盘格、增强网格独立性,借助MATLAB编程进行结构拓扑优化,得到横梁初始构型;再以横梁主要板件厚度为设计变量,建立响应面模型,计算刚度和固有频率对板件厚度的灵敏度;采用带有精英策略的第二代非劣排序遗传算法NSGA-II对响应面模型进行多目标优化,在Pareto解集中选出最优解,并基于灵敏度分析对设计变量进行取整修正,优化后的横梁动静态性能满足工程要求,目前已经应用到工程实践中,具有很强实用性.
Keyword ：
高架桥式 高架桥式 多目标优化 多目标优化 变密度法 变密度法 优化设计 优化设计 龙门横梁 龙门横梁 响应面模型 响应面模型
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| GB/T 7714 | 李志杰 , 蔡力钢 , 刘志峰 et al. 高架桥式重型龙门加工中心横梁优化设计 [J]. | 北京工业大学学报 , 2020 , 46 (5) : 440-447 . |
| MLA | 李志杰 et al. "高架桥式重型龙门加工中心横梁优化设计" . | 北京工业大学学报 46 . 5 (2020) : 440-447 . |
| APA | 李志杰 , 蔡力钢 , 刘志峰 , 郭铁能 . 高架桥式重型龙门加工中心横梁优化设计 . | 北京工业大学学报 , 2020 , 46 (5) , 440-447 . |
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