Table of Content

04 December 2020, Volume 54 Issue 11 Previous Issue    Next Issue

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Design and Optimization of Three-Dimensional Receiving Coils for Intestinal Robots WEN Yani, YAN Guozheng, WANG Zhiwu, JIANG Pingping, XUE Rongrong, WANG Yiyun 2020, 54 (11):  1117-1123.  doi: 10.16183/j.cnki.jsjtu.2019.179 Abstract ( 1011 )   PDF (3556KB) ( 451 )   Save A novel three-dimensional receiving coil structure is designed to meet the power requirements of intestinal robot and to solve the detuning problem caused by random changes of robot posture in human body. Each dimension of the three-dimensional receiving coil is wound in the same way, and the receiving power of each dimension is relatively stable. The influence of the structural parameters on transmission efficiency and power is analyzed through a series of comparative experiments from core diameter, coil turns, and wire diameter. The attitude stability of the optimized receiving coil is analyzed. The results show that the best receiving coil has a magnetic core diameter of 6mm, a number of coil turns of 80, and a coil wire diameter of 0.12mm. When the driving voltage of the transmitting coil is 10V, the maximum transmission power of the optimized receiving coil is 1216mW, and the transmission efficiency of the wireless power supply system is 6.64%. At different attitude angles, the maximum transmitted power generated by the three dimensions of the receiving coil is almost the same. The three-dimensional coil outputs a minimum power of about 527mW when α=45° and β=45°, which allows the robot to basically maintain normal operation. References | Related Articles | Metrics

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Preventive Maintenance Strategy for Multi-Stage Flexible Manufacturing System with Dynamic Production Planning ZHU Mixin, GE Yaxiong, ZHOU Xiaojun 2020, 54 (11):  1124-1133.  doi: 10.16183/j.cnki.jsjtu.2019.165 Abstract ( 821 )   PDF (1063KB) ( 410 )   Save This paper focused on multi-stage flexible manufacturing systems working in variable loading conditions. Based on the proportional hazards model, a load-dependent degradation model is proposed for components operating in the variable loading condition. Besides, a modified machine-selecting and load-sharing model, considering the virtual age of components and capacity requirement，is proposed to quantify the load condition of components. Moreover, taking degradation of components into account, a hybrid imperfect maintenance model is developed, which is followed by the final objective to determine the best maintenance strategy to minimize the expected maintenance costs of system in the dynamic production planning phase. Furthermore, a greedy algorithm with constraint on preventive maintenance time of system is proposed to solve the problem. The illustrative example shows that this model can dynamically respond to variable system maintenance requirements under the flexible operation condition. It outperforms the full loading model and the expected loading model in cost rate. References | Related Articles | Metrics

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Modeling and Optimization of 3D Assembly Tolerance for Window Lifting Under Flexible Deformation QIAN Peng, WANG Guoliang, ZHU Wenfeng 2020, 54 (11):  1134-1141.  doi: 10.16183/j.cnki.jsjtu.2019.048 Abstract ( 795 )   PDF (2431KB) ( 516 )   Save The automobile body is made of sheet metal stamping parts which are welded and assembled hierarchically. The sheet metal of the automobile body has a great flexibility. The deformation caused by external load will directly affect the transmission and accumulation of assembly deviation and finally affect the assembly accuracy and function. This paper focuses on the problem of inconsistency in the window lifting process, and a 3D assembly tolerance analysis model including finite element deformation is established to reveal the influence of sealing resistance and the rigidity of the inner panel of the door on the assembly state of the lifter. Based on the benefit ratio of tolerance optimization as the evaluation indicator to determine the optimization plan, an optimized tolerance design and an improved lifting consistency are realized. The results show that when the surface profile of the matching surface of guide rail and bracket is tightened to 0.5mm and the position of the mounting hole of glass and bracket is tightened to 0.9mm, the assembly tolerance of the door model conforms to the set goal and meets the requirements of lifting smoothness. References | Related Articles | Metrics

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Online Weighted Slow Feature Analysis Based Fault Detection Algorithm HUANG Jian, YANG Xu 2020, 54 (11):  1142-1150.  doi: 10.16183/j.cnki.jsjtu.2020.99.012 Abstract ( 804 )   PDF (6166KB) ( 425 )   Save In industrial process monitoring, traditional process monitoring methods fail to extract process dynamic information and the online fault-related information is not fully utilized in feature selection. To solve these problems, a fault detection method based on online weighted slow feature analysis (OWSFA) is proposed. First, the slow feature analysis(SFA)algorithm is utilized to extract the dynamic features. The threshold of slow feature is estimated based on benchmark data. The online features which exceed the threshold based on the slack factor are selected as the suspected fault features. Then, the monitoring statistics are built based on the weighted suspected fault features by introducing the weights. The proposed OWSFA algorithm is applied in a numerical system and the Tennessee Eastman process, which proves that the proposed method has superiorities compared with principal component analysis and the SFA method. According to the faulty information, the OWSFA algorithm generates the online weighted statistics to enhance the fault features in the monitoring model. References | Related Articles | Metrics

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A Two-Level Fault Diagnosis Method for Gyro-Quadruplet Assisted by Support Vector Machine HU Xiaoqiang,ZHONG Xunyu,ZHANG Xiaoli,PENG Xiafu,HE Ying 2020, 54 (11):  1151-1156.  doi: 10.16183/j.cnki.jsjtu.2019.107 Abstract ( 746 )   PDF (1163KB) ( 403 )   Save Aiming at the problem that the traditional parity space method cannot identify fault component in a gyro-quadruplet of the inertial navigation system, a two-level fault diagnosis method assisted by a support vector machine is proposed to ensure fault tolerance of the gyro module. The generalized likelihood ratio method, whose chi-square volume is constructed by parity residuals, is used for real-time fault detection of the four-axis gyro module. Then, a fault classifier composed of a wavelet packet transform and a support vector machine is constructed to analyze the energy characteristics of gyro output and determinate the operating state of gyro component. Finally, combining the detection results of the generalized likelihood ratio method with the output of the fault classifier, the fault source in the gyro module is detected and isolated. The simulation results show that the proposed method can quickly and accurately identify the faulty device, and thus ensure the performance of the gyro module under a minimum redundancy configuration. References | Related Articles | Metrics

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Dynamic Opportunistic Maintenance Model of Multi-Component System Considering Degradation Interaction YU Wenli,ZHOU Xiaojun 2020, 54 (11):  1157-1164.  doi: 10.16183/j.cnki.jsjtu.2019.300 Abstract ( 650 )   PDF (1007KB) ( 332 )   Save Based on the idea of state-rate degradation interaction and state discretization, a multi-component dynamic degradation interaction model is established. Besides, a non-periodic inspection policy is introduced based on the overall degradation condition of the interaction system. Moreover, from the perspective of maintenance, which can decrease the short-term interacted degradation rate of the related components, a dynamic opportunistic maintenance model is established with the goal of minimum maintenance cost per unit time. Furthermore, the non-periodic inspection policy and imperfect preventive maintenance actions are designed as well. The case study shows that the proposed model has cost advantages. References | Related Articles | Metrics

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A New Thermal Error Control Method for Spindle System of High Precision Computer Numerical Control Machine Tools ZHAO Liang,LEI Mohan,ZHU Xingxing,WANG Shuai,LING Zheng,YANG Jun,MEI Xuesong 2020, 54 (11):  1165-1171.  doi: 10.16183/j.cnki.jsjtu.2019.031 Abstract ( 1017 )   PDF (2736KB) ( 614 )   Save In order to solve the problem of thermal errors in the spindle system of high precision computer numerical control (CNC) machine tools, a novel active control method for spindle thermal deformation was proposed. Besides, a helical coil cooler was designed, the influence of silicone grease thickness on the contact thermal resistance between a spindle and a cooler was analyzed, and a thermal resistance model was established. Based on the simplified spindle system, a thermal-fluid-solid finite element model was constructed, and the cooling parameters were simulated. The finite element model was verified by using a temperature control system. The results show that the finite element model can effectively predict the variation of thermal characteristics of the spindle system. The cooler has a high heat exchange efficiency, the thermal equilibration time is reduced by 68%, and the thermal error is reduced by 19%. This study provides a new idea for thermal error control of precision machine tool spindle. References | Related Articles | Metrics

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Product Functional Degradation Assessment Based on Interval Number Prediction ZHAO Zhihua,LI Yupeng,CHU Xuening 2020, 54 (11):  1172-1181.  doi: 10.16183/j.cnki.jsjtu.2020.99.016 Abstract ( 694 )   PDF (1011KB) ( 254 )   Save The dynamics of customer requirement makes product evolution inevitable. The essence of product evolution is the divergence between the function of present product and customer requirements expectation, which is defined as product functional degradation. The identification of degraded function is the precondition for product redesign and evolution. Therefore, a method for assessing the degradation of product function is proposed. First, customer requirements are converted into function requirements based on quality function deployment, and the importance rate of function requirement is calculated by using the rough set theory and Kano index. Then, the predicted value of the value range of future product engineering characteristics is used to represent the expected design range. The difference between the value range of engineering characteristics of existing products and the design range of customer expectation is calculated by using the projection method. The functional degradation index is obtained based on the importance of functional requirements, the difference degree between engineering characteristics, and the weight of engineering characteristics. Finally, a crawler crane is taken as the research object for case analysis. The results show that the functional degradation evaluation obtained by the proposed method is consistent with the actual analysis results, which indicates that the proposed method has a certain effectiveness and practical feasibility. References | Related Articles | Metrics

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Optimal Design for Flexible Basic Warranty Policies Based on Usage Rate of Products SU Chun,ZHAO Jiabin 2020, 54 (11):  1182-1188.  doi: 10.16183/j.cnki.jsjtu.2019.183 Abstract ( 539 )   PDF (761KB) ( 305 )   Save To minimize the warranty cost of manufacturers, a two-dimensional basic warranty optimization model is established based on Copula function. The influence of usage time and usage rate on product failure rate is considered. Moreover, minimal repair and non-equal-strength periodic preventive maintenances are adopted, and the maintenance policies during the warranty period are optimized. By considering the influence of basic warranty period and sale price on product sales, a profit model is established. Considering that manufacturers provide two types of warranty policies, i.e. normative warranty policy and flexible warranty policy, for customers, the basic warranty period and its prices are optimized respectively. The result shows that minimizing warranty cost cannot ensure the maximization of manufacturers’ benefits. However, by increasing the flexibility of warranty policy, customer satisfaction can be promoted, which helps to gain more profits for manufacturers. References | Related Articles | Metrics

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Effects of Short-Term Aging and Creasing Damage on Air Leakage Properties of Airship Envelope Materials ZHANG Yunhao,Alimu·Anwaier,MI Xiang,ZHANG Daxu,CHEN Wujun,LU Guofu,ZHANG Jinkui 2020, 54 (11):  1189-1199.  doi: 10.16183/j.cnki.jsjtu.2019.170 Abstract ( 677 )   PDF (9631KB) ( 322 )   Save Aging and creasing damage of the airship envelope materials would affect the air leakage, which is a key factor in determining the duration of a single flight of an airship. In this paper, Uretek3216-LV, a high barrier property envelope material, was used to conduct a flexural durability test across five different aging timelines (0,1, 3, 8, 12 months) under four different flex conditions (20,270,900,2700 cycles) with an air leakage test in all samples. The data was analyzed using the least square method and the principle of the residual sum of squares. The relationship curves and fitted surfaces between the pressure difference, the number of rubbing times, as well as the above two factors and the air leakage rate were obtained. The influence degree of aging and creasing damage on the air leakage rate of the material was analyzed. The deformation process of the material damage was observed by scanning the material with an electron microscope and the failure mechanism was analyzed. The results show that the short-term aging damage has little effect on the air leakage properties of the envelope materials but the creasing damage will seriously affect the air leakage properties. The air leakage is proportional to the pressure difference, and the relationship between the air leakage rate and the number of flex cycles is changed from the nonlinear positive correlation of the initial segment to the linear relationship. The failure process undergoes three stages, which are the stage of loosening and twisting of fiber, the stage of functional layer failure, and the stage of fiber breakage leading to formation of pin hole. The results obtained can provide reference for the analysis and design of the airship envelope structure. References | Related Articles | Metrics

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Effect of Low Speed Loading on Failure of Aluminum Alloy-Basalt Fiber Reinforced Polymer Composite Bonded Joint LUAN Jianze,NA Jingxin,MU Wenlong,TAN Wei,CHEN Hongli 2020, 54 (11):  1200-1208.  doi: 10.16183/j.cnki.jsjtu.2019.344 Abstract ( 565 )   PDF (11443KB) ( 201 )   Save In order to provide reference and guidance for the application of bonded structure of aluminum alloy-basalt fiber reinforced polymer composite (BFRP) in the automobile industry, the aluminum alloy-BFRP bonded joints were made, and the quasi-static tensile and shear tests were conducted at the low speed loading rates of 1, 50, and 100mm/min. The aging days of 0, 5,10,15, and 20 at 80℃ was selected in combination with the temperature range in service of automobile. The quasi-static tensile and shear tests at loading rates of 1 and 100mm/min were performed for aged joints, and the quasi-static failure strength on different aging days was obtained. The failure mode of joints was studied by means of macroscopic and SEM analyses. The results show that the failure strength of aluminum alloy-BFRP bonded joints is affected by the loading rate and aging time. In the process of low speed loading, the failure strength at tensile stress and shear stress increases with the increases in loading rate. In the range of loading rate, the increase in failure strength at shear stress is larger than that at tensile stress. In the three low speed loading rate tests, the failure modes at tensile stress and shear stress are fiber tearing and adhesive layer cohesion, respectively. Low speed loading rate has no obvious effect on the macro failure mode of unaged joints. This study is of engineering significance for the quasi-static failure prediction of adhesive structures in high temperature service. References | Related Articles | Metrics

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A Spatial Spectrum Estimation Method Based on Coherent Cumulative Preprocessing YU Huabing,ZHENG Enming,CHEN Xinhua 2020, 54 (11):  1209-1217.  doi: 10.16183/j.cnki.jsjtu.2019.332 Abstract ( 631 )   PDF (1901KB) ( 314 )   Save For the stability problem of spatial spectrum estimation based on the minimum variance distortionless response (MVDR) method, a kind of spatial spectrum estimation method based on coherent cumulative preprocessing is proposed. First, complex analytic data with a certain frequency band is transformed by complex analytic wavelet transform from the collected data of receiving array, and the sub-group data is obtained according to the idea of spatial smoothing from the complex analytic data. Next, making full use of the phase information of sensor data, a group of data with high signal-to-noise ratio is obtained by accumulating the complex analytic data of each sub-group after time delay compensation. Then, the covariance matrix of the new data is constructed via multi-point cumulative processing in time domain. Finally, spatial spectrum estimation is realized according to the orthogonal property of the covariance matrix. The processing results of numerical simulation and measured data show that, compared with the MVDR method and the diagonal loading MVDR method, the data source of constructing the covariance matrix is changed in this method through time domain complex analytic transform and coherent accumulation pretreatment. The full rank covariance matrix is stably obtained by multiple sampling points accumulation in this method. According to the relation of spatial bearing and the phase difference of the sensor data, this method can effectively improve the stability of spatial spectrum estimation via double exponential function addition. References | Related Articles | Metrics

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Solving Method for Dynamic Equations of Mechanical Multibody System by Using Bathe Integration Algorithm JI Lei,QIAN Linfang,CHEN Guangsong,YIN Qiang 2020, 54 (11):  1218-1226.  doi: 10.16183/j.cnki.jsjtu.2019.018 Abstract ( 820 )   PDF (1855KB) ( 394 )   Save Accurate and efficient solving algorithms have always been the key issue in the field of multibody system dynamics. Solving dynamic equations of mechanical multibody system by using Bathe integration algorithm was investigated. The dynamic equations of multibody system were arranged into a general form containing the explicitly generalized damping matrix. Based on Bathe integration algorithm, the solution process according to the form of dynamic equations was derived, and the generalized damping matrix was used in obtaining the initial value of Jacobian matrix during iterative calculation which reduces the number of iterations. In order to reduce the influence of constraint violation, the Baumgarte constraint stabilization items were added to the dynamic equations. The numerical examples show that solving the dynamic equations of multibody system by utilizing the Bathe integration algorithm has a high accuracy, a good stability, and a low numerical dissipation, and the dynamic equation form with an explicity generalized damping matrix obviously makes the solution more efficient. References | Related Articles | Metrics