最新刊期
卷 52 ， 期 2 ， 2020
- 摘要：Carrying out large-depth and in-situ condition-holding coring of the moon is an important measure for humans to explore the moon, obtain geological information of the moon, and understand the origin and evolution of the earth-moon system and solar system. Aiming at the existed “no deep” and “unreal” technical bottlenecks during moon coring, this paper started with the geological compositions and properties of the lunar soil/rock, for the first time in the world proposed the idea of large-depth and in-situ condition-holding coring of the moon, on the basis of comprehensive consideration of factors such as drill rod connection in large depth coring, configuration design of coring robot, self-drilling and holding in coring process, in-situ condition-holding coring control, sample in-situ sealing and return, etc., proposed the scheme of a lunar large-depth and in-situ condition-holding coring robot system. According to the proposed scheme, the layout and design of the robot system was implemented, specifically, the design of a multi-segmented corer, a self-drilling coring robot, a cylindrical coordinate coring robot, a pneumatic axial propelling and pneumatic fixing, a turning and ultrasonic shock combining drilling, in-situ condition-holding based on condition-holding film and microfluidics, honeycomb-like sample condition-holding cavity, lunar sample in-situ condition-holding return etc. were implemented. Based on the above schemes and technical designs, this paper systematically summarized the key technical problems and solutions for the design of the lunar large-depth and in-situ condition-holding coring robot system. The research provided a technical reference for humans to carry out large-depth and in-situ condition-holding coring exploration on the moon and other planets. The research results will help humans to truly understand the deep in-situ geological information of the moon, and provide technical support for the scientific exploration of lunar evolution.关键词：moon;large-depth and in-situ condition-holding coring;robot;lunar exploration
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发布时间：2024-01-08 - 摘要：The dammed lake disasters in China are characterized by high frequency, wide distribution, large number of affected people and great economic loss. Hence, promoting the ability of dammed lake disaster prevention, reduction and relief is a major national need. At present, the rapid risk assessment and emergency rescue technology and equipment research of dammed lake in China still remain in the initial and exploration stage. Theoretically, the formation and outburst mechanisms of dammed lakes are not clearly revealed. Technically, the rapid risk assessment method and emergency rescue equipment cannot provide strong scientific and technological support for the emergency rescue of dammed lakes. Modern geology, hydro-sediment dynamics and informatics were integrated in this research to study the risk assessment and emergency rescue of dammed lakes. This research aimed to solve the following two scientific problems: 1) the formation mechanism of dammed lake based on the slope geology condition and sliding process analysis; 2) the outburst mechanism of dammed lake under different structure and environment condition. The following four key technologies were expected to be solved: 1) rapid sensing of multi-source information of dammed lake, dynamic identification and structural detection technology; 2) simulation technology on outburst process of dammed lake based on sand-carrying flow; 3) risk assessment technology of dammed lake disaster considering structural morphological elements; 4) efficient drainage and dredging technology of dammed lake and flow channel control technology. This research aimed to reveal the formation and outburst mechanism, build the risk assessment theory system of dammed lake, and finally develop the emergency treatment technology and equipment of dammed lake via conducting the following studies: 1) formation process of dammed lake and the mechanism and process of dam outburst; 2) fast sensing and detection of multi-source information; 3) emergency monitoring and early warning; 4) risk assessment of dammed lake; 5) emergency disposal technology for dammed lakes with high risk; 6) research and development of key emergency equipment. It is hoped that the collaborative researches in this research can significantly improve the level of emergency disposal and rescue of China’s dammed lakes, and provide science and technology support for the safety of people’s lives and properties.关键词：dammed lakes;outburst mechanism;multi-source information;risk assessment;emergency rescue;equipment development
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发布时间：2024-01-08 - 摘要：Landslide dams are natural dams, which are formed where rivers are blocked by avalanches, landslides, and debris flows. China is a high incidence area of landslide dam disasters. According to the statistics, among the cases of landslide dam in the world, 758 cases occurred in China, accounting for 59%. In recent years, frequent geological tectonic activities and extreme climate disasters (typhoons, rainstorms, snow melting, etc.) have induced a large number of landslide dams, which significantly threaten the lives and properties of upstream and downstream people. The landslide dams caused by landslide or avalanche debris normally have loose structure, poor stability, high breach size and fast breaching velocity, leading to huge breaching flood and catastrophic disaster to the downstream areas. This paper first briefly reviewed the blocking studies of generic landslide dam, and clarified the formation characteristics of landslide dam caused by avalanche and debris. Then, the movement and fragmentation mechanism of debris body and the blocking mechanism of debris body were analyzed, the characteristics of particle separation and accumulation in the process of dam formation were specifically summarized. On this basis, the effects of particle fragmentation and geological conditions on the morphological characteristics, material compositions and dam stability were confirmed with less previous studies. There were usually three dam-forming modes: sliding type, climbing type and reentry type. There were significant differences in the stabilities of different types of dams. The stability of landslide dams was closely related to the dam characteristics (geometric shape, dam structure and material composition) which were jointly determined by the debris colliding and disintegrating during sliding and solid-liquid coupled interacting during debris rushing into river. A research idea was put forward to reveal the internal relationships between the influencing factors of dam formation and the spatial shape, structural characteristics and stability of dams, so as to establish a prediction model of dam characteristics based on the rapid evaluation of dam stability. This research was meaningful in both academic and practical phases to predict the key parameters of landslide dams before its formation, and rapidly assess the landslide dam stability after its formation.关键词：landslide dam;landslide and avalanche debris;collision and fragmentation;landslide dam formation feature;landslide dam stability
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发布时间：2024-01-08 - 摘要：On October 10th and November 3rd, 2018, two successive landslides occurred at the same place of Baige village, the border of Sichuan Province and Tibet Autonomous Region, China, which blocked Jinsha River twice. Owing to the rapid rising of water level of the “10·10” dammed lake, on October 12th, the landslide dam breached naturally. Then, the flow channel formed after the breaching of “10·10” dammed lake was blocked by the “11·3” landslide, resulting in an even larger dammed lake. The measures of excavation of drainage channel were taken to decrease the water level of the dammed lake. On November 12th, the dammed lake breached with the peak flow rate of 31 000 m3/s. For the “11·3” Baige dammed lake, the detailed hydrological data were documented, which provided valuable basic data for the study of the breaching process of dammed lake. Based on the breaching mechanism of landslide-formed dam, a numerical model which can consider the hydrodynamic conditions of the lake and the morphological characteristics of dam materials of the landslide dam, was developed. The broad-crested weir equation was adopted to simulate the breach flow discharge, and the variation of water level of the dammed lake was determined according to inflow and breaching flow, as well as the rating curve of water level and surface area of the dammed lake. Based on the shear stress of water flow and the critical shear stress of dam materials, the erosion process was simulated by using the erosion formula for wide-graded dam materials. Under the assumption that the breach slope angles remain unchanged during the longitudinal cutting and transverse broadening processes, the limit equilibrium method is used to analyze the slope instability during the breach evolution process. The coupling process of soil and water during dam breaching was simulated by the time step iterative numerical method. Then, the back analysis of the “11·3” Baige dammed lake was conducted, and the comparison showed that the breach hydrograph, water level variation of dammed lake, and breach morphology evolution calculated by the proposed model are consistent with the measured data. The sensitivity analysis showed that soil erodibility had significant influence on the breaching process, and residual dam height also played a role in the breaching process by affecting the discharged water storage. In addition, the excavation of spillway can reduce the reservoir capacity when the dammed lake breached, thus affecting the breach hydrograph, which is an effective measure to reduce disaster losses.关键词：Baige;dammed lake;dam breach;numerical modeling;sensitivity analysis of parameters
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发布时间：2024-01-08 - 摘要：Landslide-induced disaster chain (LDC) has a complex evolution process, and distinguishing from the landslide disaster itself, the risk of LDC could be enhanced significantly by enlarging the scale in both space and time. Currently, the study on the quantitative analysis of the dynamic characteristics of landslide-induced disaster chain is still lack. Giving an example LDC, i.e., the disaster chain of landslides-barrier lakes-outburst, a coupled model to reflect its multiple-physical processes was adopted. The evolution process of disaster chain which may be caused by Woda landslide located in Jinsha River basin was predicted and quantitative analyzed by numerical modeling. The calculation results indicate that the maximum of landslide velocity could reach 38 m/s and a landslide dam with a height of 69 m and a length of 1.8 km blocked the river course. The area influenced by landslide could reach 2.1 km2. Dambreak could be induced when the elevation of barrier lake exceeded that of the dam crest of landslide dam. A flood with a maximum flux of 1.15×104 m3/s originated from the barrier lake with a maximum depth of 54 m could be formed after dambreak. Furthermore, the relations between each stage of disaster chain were investigated by analyzing the effects of two key factors (the basal frictional coefficient and breach stability coefficient) on the evolution process of disaster chain. It was found that the change of basal frictional coefficient had a directly influence on the mobility of landslide and the characteristics of barrier lake such as water level and breach position. For breach stability coefficient, it affected the speed of dam break as well as the characteristics of flood such as maximum flux and flow depth. It demonstrated that the relation between each stage of disaster chain was a key factor influencing the evolution of disaster chain and should be considered. These results played a supporting role in the prevention and mitigation of LDC.关键词：landslide-induced disaster chain;Woda landslide;evolution process;numerical simulation;quantitative analysis
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发布时间：2024-01-08 - 摘要：Cable-truss tensile structure is one of the most competitive spatial structures of cable-strut tensile structures. The shape determination and algorithm for self-stress modes are two key problems in design. Based on sorting and analyzing of the previous research results, it showed that most of the shape determinations of cable-strut tensile structure were solved according to the equilibrium matrix theory, which was difficult to be mastered due to the necessity of programming. Most of the existed methods to solve the self-stress mode cannot be directly used in the finite element software. To solve these problems, an improved constraints moved method based on reasonable configuration was proposed to determine the rational shape and solve the self-stress mode of cable-truss tensile structures. The method proposed was firstly based on the special topological relation of cable truss structure, and a simple formula for shape determination was derived from the rational shape. Meanwhile the method was proposed based on the idea that is shape determination first and then solving self-stress mode, which could ensure reasonable shape and self-stress mode one time and avoid the defect of solving self-stress mode firstly and then repetitively determining shape of the original method. Besides, the proposed method did not use the life-and-death unit technology of the original method, which ensured the convergence of solution process. The accumulative error caused by the technology of life-and-death unit technology was eliminated and the calculation precision was improved. The coordinate transformation was avoided and the solving process was simplified. The new method could be directly applied to the finite element software. Numerical calculations showed that the proposed method had a systematic solution flow and high convergence accuracy. The proposed method offered a new idea to determine shape and solve self-stress mode of the cable-truss tensile structures.关键词：cable-truss tensile structure;improved constraints moved method;finite element software;shape determination;solving self-stress mode
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发布时间：2024-01-08 - 摘要：Green mining of geo-resources is an inevitable demand for sustainable development of mining industry, filling mining method has become an indispensable effective means in the field of mining with the deep underground mining technology improving. The tailings flocculation and dewatering is the core of the filling mining method. The deep cone thickener is used to explore the flocculation and sedimentation law of the unclassified-tailings, which is the most advanced technology in the development of the unclassified-tailings thickening theory. The initial turbulent intensity and truss speed of the feeding well in the deep cone thickening process are the key factors affecting the size and settlement behavior of the unclassified tailing sand floe. The self-made intelligent continuous dense experimental platform was used to simulate the real sedimentation environment in the deep cone thickener. Combined with high-speed camera and particle tracking technology, the flocculation formation process in the feed well and the flocculation sedimentation process in the settling column were studied. The effects of initial turbulence intensity on floc size in feed wells (height 10 cm, cross-sectional diameters of 4, 5, 6 cm) were studied by using the MATLAB and ImageJ analysis software. The flocculation settlements under different shear environments were analyzed. The results show that the cross-section diameters of the feed wells were different under the conditions of solid flocculant unit consumption (20 g/t), feed concentration (10%) and solid flux (0.1～0.3 t/(h·m2)). At 4, 5, and 6 cm, the corresponding maximum initial turbulence intensity is 28.66%, 25.99% and 23.16%, respectively; the floc size increases first and then decreases with the increase of initial turbulence intensity; when the initial turbulence intensity is 25.99%, the size of the unclassified tail sand floe reached a maximum of 6.21 mm. The shearing action could accelerate the sedimentation of the floc. Under the same conditions, when the truss rotation speed was 0, 4 or 8 r/min, the corresponding flocculation settling speed was 1.23 cm/s, 4.92 cm/s and 3.36 cm/s, respectively.关键词：unclassified-tailings floc;initial turbulence intensity;floc size;shear action;flocculation sedimentation
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发布时间：2024-01-08 -
Experimental Study on Detecting Foamed Mixture Lightweight Filler by Acoustic Transmission Method AI导读
摘要：Based on acoustic transmission method, a non-destructive test method for the acceptance of foamed mixture lightweight filler subgrade was explored. Ultrasonic testing experiments were carried out on foamed mixture lightweight filler of different ages, different max ratios, and different crack forms by using the ZBL–U510 ultrasonic detector. Research indicated the detection efficiency is superior when the ultrasonic detector is set as a pulse width of 0.04 ms, sampling length of 512 dot, sampling period of 0.4 μs and detection voltage of 500 V. The wave velocity is positively correlated with filler’s strength and age. The amplitude decreases first and then increases with age and has no significant correlation with filler’s strength. The main frequency is not related to filler’s strength and age. When there is a crack in the test block, detecting vertical crack direction, the waveform is distorted, the spectrum diagram is multi-peak and the main frequency value is attenuated. Detecting parallel crack direction, only the waveform is distorted. When there are cracks in the test block, the more cracks and the more complicated of cracks form, the more disordered the waveform and the lower of the main frequency value. Three compressive strength prediction models were established and the errors between the predicted value and the measured value satisfy the normal distribution. The models were verified through a field test. The non-destructive testing method based on acoustic transmission method can judge the filler’s strength and whether there are cracks in filler by the acoustic parameters. The test method is suitable for the indoor test, and it provides the experimental basis for the application of foamed mixture lightweight filler in the field test of subgrade.关键词：foamed mixture lightweight filler;acoustic transmission method;ultrasonic testing;compressive strength;crack;strength prediction model- 2577
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发布时间：2024-01-08 - 摘要：In order to coordinate the relationship among utilization of flood resources, flood control capacity and downstream ecological water demand, a bivariate limit theory is proposed to evaluate the current and potential of flood resources utilization: 1) Utilizable flood resources quantity is considered as a function of flood control capacity and downstream ecological water demand; 2) Flood resources utilization potential is considered as a function of flood control capacity and downstream ecological water demand. The concept and methods are introduced and the related indexes of the area above Wujiadu hydrological station in Huaihe River basin are calculated. The results show that during 1956—2016 the average utilization rate of flood resources was 24.7%. Although the utilization rate fluctuated greatly, the overall trend is constantly increased. The current and theoretical availability were 72.4×108 m3 and 183.53×108 m3 respectively. The current and theoretical utilization potential were 34.76×108 m3 and 145.89×108 m3 respectively. It shows that under the current conditions, there is a great amount of flood resources that can be exploited and under the ideal conditions there can be more. For every increase of 20×108 m3 of flood control capacity, the utilizable flood resources quantity could increase 15×108 m3 and the flood resources utilization potentiality could increase 16×108 m3. For every increase of 20×108 m3 of downstream ecological water demand, the utilizable flood resources quantity could reduce 5×108 m3 and the flood resources utilization potentiality could reduce 3×108 m3. It shows that utilizable flood resources quantity and flood resources utilization potentiality are mainly controlled by flood control capacity. Improving flood control capacity is the key to increase the utilization level of flood resources in this region. The method to evaluate the current and potential of flood resources utilization by bivariate limit theory can provide reference for flood research and basin management organization.关键词：utilizable flood resources quantity;flood resources utilization potential;downstream ecological water demand;bivariate limit theory;Huaihe basin
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发布时间：2024-01-08 - 摘要：The flow structure appears of obviously three dimensional property resulting from flow interactions between main river and tributary river. The confluence of Shenxigou Stream and Baisha River in Dujiangyan region has the complex bathymetry, and the confluence reaches have a strong three-dimensional flow characteristics. Numerical simulation of turbulent water and gas flow was conducted for the flow structure of main stream and tributary stream based on the physical model data. The results showed that water line changed rapidly on the right side at the position of the confluence. The water surface of the right bank downstream was lower than that of the left bank. The larger the tributaries flow is, the larger the flow velocity at the downstream of confluence zone, and the lower the water level. The vicinity of the confluence section did not show significant secondary flow. The left side of the river bend downstream formed a secondary flow counterclockwise, occupying two-thirds of the cross-section. The secondary flow had obvious impact on sediment motion of the river bed. Whether there is a tributary flow or not, a diverse range of separation zone would be formed near the right bank downstream of the confluence, and the top shape of the separation zone would change significantly. The size parameters of the separation zone would be lower with the increase of water level elevation.关键词：river confluence;physical model;numerical simulation;flow structure;separation zone
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发布时间：2024-01-08 - 摘要：The hydrological changes in the Lower Jingjiang reach is related to the complex exchange relationship between Dongting Lake and Yangtze River. After the construction of the Three Gorges Dam (TGD), the change of the base level of lake Exit makes the lake-to-river supporting and falling effect adjustment, which could have an adverse impact on flood control & draught resistance and ecological environmental protection. Based on the variation of water surface slope, the supporting and falling ratio is proposed to characterize lake-to-river effect. The data at Jianli, Luoshan and Qilishan station from 1991 to 2017 are used to analyze the supporting and falling effect and its variation characteristics. The rationality of gradient change before and after impoundment is explained theoretically by using balanced gradient formula. The results showed that: After impoundment, the water surface slope of Jianli—Chenglingji and Chenglingji—Luoshan increased. The minimum monthly slope of Jianli—Chenglingji reach was delayed from 1991—2002 to 2003—2007 to 2008—2017. The corresponding water level in Chenglingji increased, while the confluence ratio decreased, and the supporting effect of lake-to-river was weakened. The lake supported the river comprehensively during 1991—2017 periods. The reason for supporting and falling ratio reduction is the weakening of supporting effect rather than the enhancement of falling effect. After the flood season (September—October) during three periods, the lake showed a falling effect on the river, while from 2008 to 2017, the falling effect of the lake also occurred in the dry season (January—March). Supporting and falling ratio is affected by the confluence ratio during three periods. When the confluence ratio is less than 0.5, the lake is liable to the falling effect on the river. When the confluence ratio is greater than 1, the supporting effect increases. When the discharge in the Yangtze River is less than 6 000 m 3/s, the Dongting Lake acted as a supporting force to the Yangtze River. During 1991—2002, the supporting and falling effects were mainly affected by the Dongting Lake outflow, while during 2008—2017, they were mainly affected by the discharge in the Yangtze River. The research results can provide scientific basis for river regulation, water ecology and water resources utilization in the lower Jingjiang River.关键词：supporting and falling ratio;Dongting Lake;lower Jingjiang River;water surface slope
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发布时间：2024-01-08 - 摘要：Geomechanical model test is one of the important methods to study the stability and safety of dams. It selects a certain overload frequency to carry out step-by-step overloading test to obtain the results of displacement, strain, failure process and failure mode of the model dam, and to evaluate the stability and safety of the prototype dam project. Therefore, the choice of overload frequency directly affects the reliability of the test results and requires in-depth research. Aims at the impact of overload frequency on model test results and the selection of reasonable overload frequency, the geomechanical model tests with different overload frequencies （ΔP=0.2P, 0.5P, 1.0P） are carried out. The influence of overload frequency on the results of geomechanical model test is analyzed. Combined with the numerical calculation and the results of the rigid body limit equilibrium method, the reasonable value of the overload frequency is comprehensively analyzed and determined, that is, ΔP=0.2P. On this basis, the research results are applied to the stability study of the typical dam section of Danba hydropower station, and the geomechanical model test is carried out. Through the test, the displacement distribution characteristics and displacement curve, failure process and failure mode and overload stability safety coefficient of the dam and dam foundation of Danba hydropower station are obtained. The stability of the dam foundation of the typical dam section of Danba hydropower station is evaluated. The research results provide a scientific basis for the loading method of the dam stability geomechanical model test and help to improve the reliability of the test results.关键词：dam stability;geo-mechanical model test;overloading frequency;degree of influence;reasonable value;engineering application
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发布时间：2024-01-08 - 摘要：The concrete-rockfill combination dam (CRCD) is mainly composed of the upstream concrete wall and downstream declivitous rockfill. As a new type of dam structure, its dynamic characteristics are not studied thoroughly so far. A physical simulation test of CRCD was conducted utilizing the large-scale shaking table. The displacement, dynamic earth pressure and the distribution of resultant point were analyzed. The results show that: 1) The displacements of CRCD wall were relatively small, and the top displacement of the wall was larger than that of the bottom wall, as well as it owns RBT model (rotation around a certain point under the wall-bottom). 2) The dynamic earth pressure at the bottom of the wall was obviously lagging behind the input seismic wave. 3) The total dynamic earth pressure on the back face of wall increased with the increase of peak ground acceleration (PGA). When PGA ≤ 0.2g, the total dynamic earth pressure was approximately linearly distributed along the wall height. When PGA ≥ 0.4g, the total dynamic earth pressure showed a significant nonlinear distribution. 4) Under the influence of the declivitous rockfill body and the displacement model of the wall, when the seismic intensity was less than 8 degrees, the point of resultant force for total dynamic earth pressure was generally lower than the 0.33H proposed by the Mononobe–Okabe (M–O) theory . But when the seismic intensity was above 8 degrees, the results were higher than 0.33H. The results revealed the dynamic response characteristics of displacement and earth pressure, and provided a reference for the anti-seismic design of CRCD.关键词：hydraulic engineering;concrete–rockfill combination dam;large-scale shaking table;displacement model;dynamic earth pressure
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发布时间：2024-01-08 -
Seismic Fragility Analysis of Gravity Dams Considering the Fuzziness of Damage States Thresholds AI导读
摘要：Since the evolution of the structural damage states is a gradual transitional process and the fuzziness of cognition, the thresholds of damage states of the gravity dams are fuzzy, which will affect the evaluation results of damage states of gravity dams. Fuzzy intervals of damage states thresholds and construction principles of membership function for damage indexes were proposed, and a mathematical model describing the fuzziness of damage states thresholds of gravity dam was built. Based on the nonlinear finite element dynamic analysis of dam-foundation system, Hariri–Ardebili’s quantitative method and the proposed mathematical model, a methodology for fuzzy seismic fragility analysis of gravity dams was proposed. Pine Flat gravity dam was used as a setting for numerical simulations. The 60 seismic waves were selected from ground motion database for incremental dynamic analysis of Pine Flat gravity dam. The damage indexes under different seismic inputs were calculated and the corresponding damage states were defined. The influence of the types of membership function and the sizes of fuzzy intervals of damage states thresholds on seismic fragility was investigated. The results showed that the types of membership function had little influence on seismic fragility of Pine Flat gravity dam, while the influence of sizes of fuzzy intervals on seismic fragility curves was obvious. Due to the distribution characteristics of damage indexes, the fuzziness of the damage states thresholds led to a significant increase in the probability of exceeding of Slight damage, while the probability of exceeding of near collapse decreased. Therefore, the influence of fuzziness of damage states thresholds should be considered in seismic fragility analysis of gravity dams.关键词：gravity dams;seismic fragility;fuzziness of damage states;nonlinear dynamic analysis;dynamic response- 2573
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发布时间：2024-01-08 - 摘要：A quadruped magnetic absorbing wall-climbing robot with omni-directional motion was designed to achieve reliable adsorption and free movement on the iron-based wall with different curvatures. Firstly, the modified Grübler–Kutzbach (G–K) formula was used to analyze the degree of freedom (DOF) of the robot. Then the Denavit–Hartenbery (D–H) method was used to establish the linkage coordinate system of the robot walking legs, and the forward and inverse kinematics of the walking legs were analyzed. Then the robot was regarded as a parallel mechanism, the forward and inverse kinematics of the carrier platform were analyzed, the analytic solution of the inverse kinematics was given, and a numerical algorithm based on Newton’s method was used to solve the redundant equations to obtain the numerical solution of the forward kinematics, the complete kinematics mathematical model of the robot was established. To verify the correctness of the model, the calculation program was compiled in MATLAB according to the model, and the same kinematics simulation was performed in MATLAB and Adams respectively to make comparisons. Finally, the Jacobian matrix of the robot was obtained by the screw theory, and the singularity of the robot was analyzed by combining the Grassmann line geometry theory. A forward kinematics singularity in non-redundant driving was verified. The results of DOF analysis showed that the carrier platform has six-DOF, so it can complete the omnidirectional motion in the space, and the structure design of the robot is reasonable. The simulation results of MATLAB and Adams are consistent and the forward and inverse kinematics can mutually verify each other, which illustrates the correctness of the mathematical model, and provides an a theoretical basis for the motion control, trajectory planning of the robot. The singularity of the robot is obtained, which provides an approach to avoid it. No power consumption still is achieved by utilizing the inverse kinematics singularity.关键词：quadruped robot;parallel robot;kinematics;numerical solution;screw theory;singularity
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发布时间：2024-01-08 - 摘要：The position independent geometric errors (PIGEs) of the rotating axes of five-axis machine tools caused by the assembly are the key factor to determine the accuracy of the machine. Quantization analysis of the influence of PIGEs on the accuracy of error vector, the coupling effect and determine the weight coefficient of the compensation value is the key technology of machine tool error compensation technology. In order to reduce the impact of PIGEs on machine tool accuracy caused by the assembly of five-axis machine tools, according to the distribution characteristics of the rotary axes of five-axis machine tool, the geometric error model is established based on multi-body system theory and homogeneous coordinate transformation method, and the mapping relationship between spatial error vector and geometric error terms is characterized. Secondly, by considering the distribution characteristics of geometric error, and Morris global sensitivity analysis method is introduced to quantify the effect of geometric error and coupling strength. The correlation coefficient between the sensitivity coefficient and the error vector is characterized by gray correlation analysis. The weighting factors of the position-independent geometric errors compensation value are determined. Finally, the measurement and identification experiment was conducted on five-axis machine tool with swiveling head is carried out, and the virtual cone-shaped trajectory measurement and error compensation experiment with DBB are carried out by using the identification value. The results show that the direct effect of ten geometric errors on attitude errors is the most obvious, and the error compensation based on the sensitivity analysis is performed, the radius deviation of the virtual cone measuring trajectory is reduced by 65.1%, and the roundness error is reduced by 58.8%. By error compensation based on error analysis, the contour accuracy of S-shaped test workpiece is improved by 49.9% on average. The error compensation results verify the validity of the error analysis results.关键词：five-axis machine tool;rotary axes;position independent geometric errors;error analysis;error compensation
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发布时间：2024-01-08 - 摘要：PD control is widely used in the control of industrial production process, and it is also one of the control strategies with the simplest structure. It focuses on the steady-state performance of the control system, but there is not enough attention paid on the dynamic performance (including the overshoot and the convergence speed, etc.) of the system. Therefore, if the response speed is improved in the traditional PD control, the overshoot would increase and the oscillation response would be intensified. If a small overshoot is wanted, the response speed might be slow down. It seemes that the response speed and overshoot to be parameters of contradictory performance and it is difficult to improve response speed and reduce overshoot by using traditional PD control alone. The prescribed performance control means that the tracking error should converge to a predefined small residual set, with convergence rate no less than a prespecified value. The combined PD control with the prescribed performance control to design the manipulator motion controller using simple PD control structure and the prescribed performance function based on error transform of logarithmic form. The steady-state error can be preset in the design process of the controller, while the control error of traditional ID controller can only be gradually reduced after multiple parameters setting and debugging. Therefore, the design process of the control algorithm proposed was simple and convenient, with more accurate control precision and faster response speed. At the same time, the control algorithm can control the overshoot within a reasonable range. By the analysis of modeling and simulation of spatial three joints manipulator, the results showed that the prescribed performance PD control has the advantage of 40% faster response and 10% less overshoot comparing with the traditional PD control. By the prototype experimental analysis of the 4D of Dobot manipulator, the results showed that the prescribed performance PD control has the advantage of 20% faster response and 5% less overshoot comparing with the traditional PD control, which makes it obvious for the improvement of the dynamic response performance of the control system.关键词：manipulator;prescribed performance function;motion control;PD control
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发布时间：2024-01-08 - 摘要：In the 5-axis flank milling force modeling, the calculation of instantaneous undeformed chip thickness (IUCT) is the key link of milling force prediction, which directly affects the prediction accuracy and efficiency of milling force. In order to improve the prediction accuracy and efficiency of milling force, based on the spatial motion analysis of 5-axis machine tools and considering the radial cutter runout effect, a calculation model of IUCT in 5-axis flank milling process was proposed. First, the law of compound motion of milling cutter with tool rotation, swing and translation in 5-axis flank milling process was analyzed, and the coordinate position of each cutting edge at different tool points were obtained. Then, a efficient calculation method of TUCT considering the radial cutter runout effect was presented. Finally, combined with the idea of parameterized thickness compensation, the calculated IUCT was corrected and an equivalent thickness model was established. The equivalent thickness model proposed in this paper with the existing arc model and linear iterative exact model were applied to the simulation example. The results showed that the result of the equivalent thickness model is closer to the iterative exact values, and the average error rate is only 1.37%, decreased by 8.35% compared to the arc model. Under the premise of ensuring the prediction accuracy, the prediction efficiency of IUCT is increased 10 times compared with the linear iterative model. It has a promising application prospect in the establishment of 5-axis flank milling force model.关键词：instantaneous undeformed chip thickness;5-axis flank milling;cutter runout radial;parameterized error compensation
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发布时间：2024-01-08 - 摘要：CNC spinning machine is a high-tech machine tool which integrates the spinning system, automatic machinery system, hydraulic servo control system and other advanced technologies. The machining accuracy of CNC spinning machine is depended on the gap between spinning wheels and the core mould. Because of the change of spinning wheels’ positions and postures in manufacturing process, the spinning frame configuration and axis coupling forces will change accordingly, which causes complexity and uncertainty of predicting the spinning machine dynamic characteristics. In order to improve the characteristics of a two-wheels CNC spinning machine, a dynamic finite element model of spinning frame system was constructed based on virtual prototyping technology. The joint coupling forces and dynamic parameters were fully considered during the modeling process. The first order natural frequency was taken as the reference index for dynamic characteristics analysis. Simulated and experimental modal analysis were carried out throughout the whole manufacturing space using finite element model modified method, in order to investigate the dynamic characteristics of spinning frame and its variation with different positions and postures. Simulated and experimental results showed that the values from two different methods agreed with each other well with an average error rate of 2.21%. The first order natural frequencies, vibration modes and damping ratios were changed when the spinning frame was moving along X-axis and Z-axis. The maximum changing of first order natural frequencies was up to 26% comparing two extreme positions. When the coordinate of spinning wheel was larger at Z-axis and more centered at X-axis, the first natural frequency was smaller and the amplitude was higher. This indicated that the spatial positions and postures of spinning frame had great effect on the dynamic characteristics of spinning machine. The results can be used to develop new spinning machine tools, optimize processing routes and design optimal processing positions.关键词：dynamic characteristics of machine tool;spinning frame;generalized manufacturing space;natural frequency
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发布时间：2024-01-08 - 摘要：The measurement result of the force-measurement system (FMS) will be greatly impacted by the stiffness of the force balance when it is used in an impulse combustion wind tunnel. To study this issue, firstly, the FMS is simplified and its dynamic motion equation is given. Secondly, the stiffness matrixes and modal parameters of the FMS–A, FMS–B, and FMS–C with different stiffness are acquired by the virtual calibration and modal analysis. Thirdly, the transient simulations of FMS–A, FMS–B, and FMS–C are conducted to acquire their responses. The results show that the mean measurement accuracies before and after the inertia compensation are higher than 93.00% and 99.60%, respectively. The mean outputs of FMS–A, FMS–B, and FMS–C are close to each other when the same loads are applied on the test model. This proves that the stiffness of the force balance has little influence on the mean measurement accuracies of the FMS. In addition, the transient output histories are approximately consistent with the inputs. The transient measurement accuracies of FMS–A in drag, lift, and pitching moment are higher than 85.13%, 80.14%, and 68.40%, respectively. They are higher than 85.90%, 83.48%, and 69.90% as to FMS–B, respectively and they are higher than 85.91%, 89.05%, and 74.67% as to FMS–C, respectively. This shows that, on a certain range, the transient measurement accuracies are improved with the increase of the stiffness of the force balance.关键词：force-measurement balance;force-measurement system;stiffness;inertia compensation;measurement accuracy
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发布时间：2024-01-08 -
Design and Research of Three-extensible-rod Solar Tracking Drive System for Photovoltaic Panels AI导读
摘要：A solar tracking drive system can significantly improve the efficiency of photovoltaic panels for receiving solar energy. Compared with series-type, parallel-type solar tracking drive systems have great application potential in solar tacking with its high tracking accuracy, low power consumption and material loss. However, related research is still at the beginning stage and can not meet the actual demand. Therefore, based on 3-RPS parallel mechanism, a novel three-extensible-rod solar tracking drive system for photovoltaic panels was proposed. Three extensible rods had the same structure and were arranged as an equilateral triangle. The upper end of each extensible rod was connected to the photoltaic panel by a compound hinge, and the lower end was connected to the base platform by a rotary hinge. The photovoltaic panel could be driven by changing the lengths of three extensible rods, and then the real-time solar tracking could be realized. Firstly, based on the law of solar motion and the characteristics of 3-RPS parallel mechanism, the related mathematical models of sun tracking were established by the knowledge of space geometry. On the basis of this, for given tracking location, date and mechanism dimensions, the system was analyzed by simulation on the summer solstice and winter solstice, respectively. For the problem that the section number of each extensible rod is too much, a new control strategy of the highly movable centroid of the mobile platform was proposed. For the problem that the rotation range of the commercial spherical hinge is insufficient, a structural scheme of the compound hinge with hook and rotation hinge to replace the spherical hinge was adopted. Moreover, the rotation angle of the compound hinge around each axis was obtained. Then, as the process of tracking the sun is slow, the instantaneous static model of the system was established, and the driving force and driving power of the system were obtained. The maximum driving force is 164.65 N, and the total driving power is 2.94×10–3 W. Finally, solar tracking experiments of the system were carried out. The experimental results verified the theoretical and simulation analysis, and the tracking precision of the system is no more than ±0.4°.关键词：photovoltaic panels;three-extensible-rod;solar tracking;drive system- 1921
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发布时间：2024-01-08 - 摘要：In order to accelerate the convergence speed of the traditional DE algorithms for some complex optimization problems, an adaptive bare-bones differential evolution based on cosine (CABDE) was proposed. In the proposed CABDE, a new adaptive mechanism for mutation strategy selection was presented. Moreover, a cosine adaptive factor was introduced to achieve the complementary advantages of the Gaussian mutation strategy and the DE/current-to-best/1 mutation strategy. The Gaussian mutation strategy has excellent global search ability, which is good for maintaining the population diversity; While the DE/current-to-best/1 mutation strategy exhibits good local search ability, which is helpful for accelerating the convergence speed. Therefore, the presented adaptive mechanism can maintain a balance between the exploration and exploitation. In addition, the information of the best individual in both Gaussian mutation strategy and DE/current-to-best/1 mutation strategy was utilized to guide the search directions. During the evolution process, the cosine adaptive factor was adjusted according to the increase of the iterations and then the suitable mutation strategies in the different evolutionary stages were adaptively chosen. As a result, the presented adaptive mechanism can maintain the population diversity as well as accelerate the convergence speed. To test the performance of CABDE, 18 test functions with different characteristics were used in the experiments. The effectiveness of the mutation strategies and the dynamic parameters were discussed. The experimental results showed that the mutation strategies and the dynamic parameters can improve the search performance. Moreover, CABDE was compared with several new variants of bare-bones algorithms, DE variants, PSO variants, and ABC variants. The comparisons indicated that CABDE can achieve better solutions and exhibit faster convergence speed.关键词：differential evolution;bare-bones algorithms;Gaussian mutation;cosine adaptive factor
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发布时间：2024-01-08 - 摘要：Deniable encryption is an intriguing scheme against the problem of information leakage caused by adversary coercion. Previously proposed deniable schemes cannot resist the attack of quantum computers and there are few implementations of these schemes. Aiming at this problem, a deniable encryption scheme based on learning with errors (LWE) and related implementations were proposed. The scheme can resist the quantum attack, and also can deny the plaintext to any fake plaintext, so that the sender can resist the adversary’s coercive attack. Firstly, by using the indistinguishability of the LWE problem, a subset with low density named “translucent set” was constructed in a uniform space. The “translucent set” was used to construct the ciphertexts of bits 0 and 1, which enabled one-way deniability of a single bit and reduced the error rate. Then, a plaintext coding method was proposed to realize two-way deniability of a single bit so that the sender could deny the original plaintext to any fake plaintext. The theoretical analyses were given to show the deniability, security (IND–CPA), correctness, complexity and ciphertext expansion rate of the scheme. Finally, the scheme was implemented by C++, and experiments had been done for the error rate, ciphertext expansion rate, encryption and decryption efficiency. The experimental results showed that the error rate and ciphertext expansion rate were consistent with the theoretical results. Compared with other deniable schemes based on the quadratic residual problem, the proposed scheme has obvious advantages in anti-quantum attack, efficiency and ciphertext expansion rate. Specifically, the encryption efficiency is improved by 70%, and the ciphertext expansion rate is reduced to 1/3 of above schemes.关键词：anti-quantum attack;deniable encryption;public key encryption;translucent set
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发布时间：2024-01-08 - 摘要：Pin point spots defects appear easily on the surface of Interstitial-free steel during the manufacturing process and badly influence the surface quality. This paper exploited thermal-gravity experiments to investigate the experimental research on the oxidation mechanism of IF steel in air. Results showed that the oxidation degree of IF steel increases with reacting temperature with exponential relationship; and oxidation of IF steel is more sensitive to temperature. In experiments, weight gains per unit area of IF steel were 24.46, 108, 220 and 355 mg/cm2 at furnace temperature 868, 977, 1 087 and 1 200 ℃, steel temperature 868.4, 976.9, 1 087.4, 1 199.5 ℃. By analyzing the morphology and composition of the oxide layer at four different temperatures, it was found that the oxide layer exhibites a jagged inner and outer surface at a temperature of 868.4 °C, the interface is rough, and there is no void inside the oxide layer. When the steel temperature is 976.9 ℃, pores appear inside the oxide layer, and the oxide layer is tightly bonded to the steel matrix. When the steel temperature is 1 087.4 ℃, the inner and outer surfaces of the oxide layer are flat, and no pores appear inside the oxide layer, but the surface of the steel substrate shows obvious oxidation. The inner and outer surfaces of the oxide layer formed at a steel temperature of 1 199.5 ℃ are flat, the oxide layer is dense, and no pores appear inside. The composition of the oxide layer is mainly FeO, and Fe2O3 and Fe3O4 are little.关键词：ultra-low carbon interstitial-free steel;oxidation weight gain;morphological analysis
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发布时间：2024-01-08 - 摘要：In order to study the effect of counterpart surface roughness on tribological properties of nanoparticles filled polyphenylene（PTFE）composites under dry friction condition, cold compression molding and hot sintering were used to prepare nano-SiO2 filled PTFE composites. The tribological properties of nano-SiO2 filled PTFE composites sliding on three kinds of counterpart (GCr15) surface with different surface roughness were evaluated by LSR–2M reciprocating friction and wear tester. The morphologies, microstructures and chemical compositions of the transfer films and debris were characterized by optical microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS), in order to reveal the friction transfer mechanism of nano-SiO2 filled PTFE composites from the microscopic perspective. The experimental results showed that the friction coefficients of pure PTFE and different content of nano-SiO2 filled PTFE composites increased with the increase of the surface roughness of the steel counterpart, while the friction coefficients were relatively small on the counterpart surface with roughness 0.1. The addition of nano-SiO2 effectively reduced the wear volume of PTFE on three different counterpart surface roughness, when the filling ratio was 0.5%, the best tribological property was obtained on the counterpart surface with roughness 1.2, the running-in time was nearly 10 minutes shorter than pure PTFE, and the wear resistance was 33.3% higher than that of pure PTFE. There was a synergistic effect between the content of nano-SiO2 and the counterpart surface roughness, the friction pair that compose of PTFE composites filled with nano-SiO2 and steel discs counterpart with certain surface roughness can effectively promote the friction transfer of composites, therefore the transfer films with high coverage, uniformity, continuity, rough surface and consistent with the direction of friction on the counterpart surface were formed, which is beneficial for reducing the wear of materials.关键词：PTFE;nano-SiO2;counterpart surface roughness;friction transfer;transfer film
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发布时间：2024-01-08
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