Abstract:For the problem of amphibious robots thrust disturbance caused by the instability and environmental attitude instability, a new kind of water jet propulsion with driving wheels is designed which can be rotated compound propulsion system. In the H amphibious robot configurations application, the tilt angle separation control strategy based on the thrust and the immunity control principle stance was designed, and the asynchronous adjustment mechanism is adopted in the coupling degree of freedom. Finally, Simulink/ADAMS co-simulation platform is used to simulate and verify the attitude stability, and the controller parameters with good effect are determined. The experimental results of the physical prototype show that the h-type amphibious robot can complete the preset motion, and the attitude self-stabilization controller can restrain the attitude jitter of the robot within 5° when it runs underwater.

Abstract:To solve the problem of random distribution paths of precast concrete components, a method of dividing the distribution area into multiple distribution sub-areas is designed by meshing the distribution area. The total length of the path is divided into cloth length and non-cloth length, of which the cloth length is a certain value, and the cloth operation is planned for the sub-areas, and the cloth width corresponding to the number of discharge openings is calculated. Using the enumeration method and dynamic programming algorithm, the distribution path planning model for the set of the discharge port and the distribution sub-area of the auger is established, the decision value in the multi-stage decision-making is calculated, the model with the shortest non-distribution length as the goal is solved, the shortest cloth path is got, and the full coverage path planning of the auger for the cloth area is completed. According to this method, a two-dimensional distribution path planning model is established for a auger and a prefabricated exterior wall siding. The simulation results show that this method can effectively shorten the distribution length and reduce the distribution time, and has certain guidance for the production of precast concrete components.

Abstract:In this paper, density functional theory (DFT) method is used to study the adsorption behavior of As₂O₃ on α-Fe₂O₃(001) surface and the influence of doping Mo, Mn and Ni on the adsorption behavior of As₂O₃ on α-Fe₂O₃(001) surface. The adsorption model of As₂O₃ on the surface of α-Fe₂O₃(001) and the adsorption model of Mo, Mn and Ni doping were established. The adsorption energy of As₂O₃ on the catalyst surface was calculated. The density of bonding states and the charge layout of As₂O₃ on the surface of α-Fe₂O₃(001) before and after doping are analyzed. Electron transfer occurs in the four systems. Mo doping activates As₂O₃ molecules, makes As₂O₃ tend to be adsorbed on Mo active sites, protects Fe active sites, and enhances the anti-arsenic poisoning ability of α-Fe₂O₃. After Mn and Ni doping, the reaction activity of As₂O₃ is lower than before, which inhibits the adsorption of As₂O₃ and increases the poisoning effect of the catalyst, which is not conducive to the subsequent NH₃-SCR reaction.

Abstract:To solve the problem of impediments of production plans and decline of production efficiency caused by potential time-varying effects of the machine condition uncertainty in the semiconductor production process, decision-making methods for wafer production sequence scheduling considering time-changing effects are developed. Firstly, with collecting historical processing time data, the relevance between characteristics of machine condition variation and time-changing effects of wafer processing times is diagnosed to establish parallel machine scheduling model considering time-changing effects. The target is to minimize the makespan. A hybrid search algorithm with optimal scheduling knowledge (HSAOSK) is designed based on optimal single machine scheduling rules and multi-machine scheduling optimization knowledge to reduce the searching space and improve the calculation efficiency. Computational experiments show that the optimal solution of the HSAOSK algorithm is the same as the exact algorithm to solve small-scale cases. As for the large scale cases, comparing to the other algorithms, the optimal makespan of HSAOSK algorithm has 6.17% decrement with the shortest time consumption. The HSAOSK algorithm can meet the needs of constructing a semiconductor scheduling decision-making scheme.

Abstract:In view of the long life and slow degradation of RV reducers used in industrial robots, a method is proposed to evaluate the reliability of RV reducers based on the high stress accelerated degradation test and the modeling of transmission accuracy degradation. The maximum loading value of the accelerated test is determined by strength verification of the weak links. To obtain the degradation amount of the RV reducer transmission accuracy, the accelerated degradation test is conducted on three RV reducers under this loading value. According to the degradation characteristics of the RV reducer transmission accuracy, the degradation trajectory of the transmission accuracy of each reducer is modeled by using the maximum likelihood estimation method with sample data separation. The initial performance degradation and drift coefficient in the Wiener degradation model are set as constant values, and the coefficient of variation of the diffusion coefficient is obtained, assuming that the diffusion coefficient obeys normal distribution to find the reliability of the RV reducer. The results show that the high stress accelerated degradation test can provide reliable test data for RV reducer reliability analysis and save test costs. The proposed method can realize the reliability analysis of RV reducer under small sample conditions while reflecting individual differences, and can accurately calculate the failure probability of RV reducer, which is important for improving the working performance of industrial robots.

Abstract:To improve the performance of high specific speed centrifugal pumps and to solve the problem of multi-parameter optimization, an optimal design method based on variable dimensionality reduction and intelligent algorithms was proposed in this paper. The variable dimensionality reduction process was based on the Pearson correlation analysis method, which investigated the influence of eighteen design variables of the impeller on the pump hydraulic performance, and selected eight of them with high influence factors as the final optimization variables. The optimization process was based on the Latin Hypercube Sampling method to generate 160 sets of design samples, and the optimization problem was solved by using artificial neural network and genetic algorithm with maximizing the design working efficiency as the objective. The optimization results are verified by CFD, and the efficiency of the model pump is improved by 3.02% at the design operating point, and the efficient operation zone is broadened; compared with the original impeller, the turbulent kinetic energy distribution in the optimized impeller is improved and the unstable flow structure is reduced.

Abstract:To improve the machinability and surface integrity of magnesium alloys, and optimize the machining parameters, a set of orthogonal experiment with four factors and four levels were carried out based on the method of pseudo-level. Comparative study involved in the influence of three different cooling strategies, namely, dry cutting, liquid carbon and liquid nitrogen coolants, as well as the cutting parameters on the surface integrity of ZK61M magnesium alloy during turning were conducted. The experimental results show that the effect of cutting depth on cutting force is the most significant factor, the feed quantity is the second significant factor, the effect of cutting speed on cutting force is ignorable. Although the effect of cryogenic cutting on cutting force is not significant, it can reduce the cutting force in some extents. The feed rate has a significant effect on the surface roughness and surface residual stress. As the feed rate increasing, the surface roughness increases and the residual stress is introduced on the machined surface. The cooling medium has a sub-significant effect on the surface roughness and surface residual stress. Compared with dry turning, The cryogenic coolants can effectively reduce the surface roughness, refine the surface grain and increase the surface compressive residual stress during cutting. As a cooling medium, the liquid carbon dioxide is more effective than liquid nitrogen in improving the machining-induced surface integrity. Grey relational analysis is used to obtain the optimal process parameters for cryogenic cutting of ZK61M magnesium alloy: v_c=100 m/min, f=0.05 mm/r, a_p=0.4 mm, liquid carbon dioxide is used as the cooling medium. The response prediction model between the process parameters and the machined surface quality was established through the results of the relational analysis, the average error was 7.93%.

Abstract:Based on ANSYS, this paper conducts a simulation study on the external pressure buckling of a cylindrical shell with initial defects. First, the eigenvalue buckling analysis of the ideal cylindrical shell is carried out, and the first thirty order linear buckling modes are obtained as the initial geometric defects. Secondly, the single modal defect method and the combined modal defect method are used to establish the model with initial geometric defects. The nonlinear buckling analysis is performed by the non-linear stabilization algorithm and the arc-length method of the finite element method. Then, the critical buckling load is obtained by the static pressure buckling experiment of the cylindrical pressure shell. Finally, the results of nonlinear buckling analysis are compared with the experimental results and the calculation results of pressure-bearing structure engineering design methods. The results show that the arc-length method has higher prediction accuracy than the non-linear stability algorithm. The results obtained by the engineering design method of pressure-bearing structures are conservative, and the critical buckling load is much lower than the experimental results. The first-order modal defect is not the initial defect that has the greatest impact on the critical buckling load, the order of the most unfavorable initial defect is generally low. The amplitude of the initial defect in the model has a great influence on the critical buckling pressure, but it has little influence on the modal order of the most unfavorable initial defect. The above two initial defect construction methods are effective, but the low-order multi-modal combined defect model has higher prediction accuracy with an error of about 3.55%.

Abstract:To solve the problems that humanoid robot design is mainly based on empirical design or motion simulation verification and the initial design method under the requirement of various motion behaviors such as walking, running and jumping with reference to human itself does not exist yet, in this paper, motion capture and plantar force measurements are performed on a variety of human motion behaviors, and joint torque and joint power during human motion are selected as indicators to characterize the ultimate drive capability that a humanoid robot should achieve. The PhaseSpace three-dimensional motion capture system and self-developed integrated force measuring system with range of at least 5 times the body weight were used to conduct the measurement experiment of human motion trajectory and plantar force on 6 adult males under different behaviors. Based on the 149 sets of experimental data obtained, the characteristics of human walking, running and jumping behaviors were obtained and analyzed. The inverse dynamics of each joint of human lower limb was calculated by Newton-Euler method, and the multivariate nonlinear fitting was carried out to obtain the fitting equations of maximum drive torque and power. The design reference guidelines for humanoid robots are summarized to provide a reference for the design of humanoid robots with multiple movements such as walking, running and jumping.

Abstract:To imitate the chameleon skin, a method using microfluidic color-changing system to camouflage films is proposed. By sensing and collecting environmental color change information, the control signal of the microfluidic system can be adjusted in real-time to drive the dyed liquids circulating in the micro channels of the camouflage film to achieve dynamic cloaking and camouflage. The microstructure of the film and the working principle of the microfluidic color-changing system are introduced. The mechanism to generate the color signal by deep learning image completion algorithm and image processing technology is illustrated. “Canny” double-threshold edge detection algorithm and color similarity are used to analyze and evaluate the camouflage. The tested results show that the camouflaged chameleon skin is not obvious and has a relatively high compatibility with environmental backgrounds and the dynamic cloaking effect can be achieved. The camouflage film implemented by the microfluidic color-changing system can be applied to various occasions such as camouflage uniforms for officers and soldiers, robot skins, weapon equipment, and camouflage nets for military facilities.

Abstract:To study the variations of friction torque and gaps during the disengaging process of a wet multi-disc clutch with different spline friction coefficients, a comprehensive disengaging dynamic model is proposed, and the non-uniformity coefficient is employed to characterize the disengaging uniformity. The results show that during the disengaging process, the friction pair gaps first increase slowly, then increase rapidly, finally stabilize after fluctuating. The disengaging process ends when the friction pair gaps stabilize, but the spline friction coefficient has slight effect on the disengaging time. When considering the spline friction, the disengaged gaps are no longer uniform, but decrease from the first friction pair to the sixth friction pair in sequence. Moreover, the increase of spline friction coefficient significantly deteriorates the disengaging uniformity. Finally, with the increase of spline friction coefficient, the initial value and change rate of contact torque decrease, while the final value of hydrodynamic torque increases. Therefore, the decrease of spline friction coefficient promotes the uniform disengaging of friction pairs and reduces the drag torque.

Abstract:To improve the thermal uniformity of liquid cooling system for the battery thermal management, a three-dimensional CFD model for the coupled heat and mass transfer in the liquid cooling system was established, which was consisted of a grooved aluminum vapor chamber and a one-through flow liquid cooling plate. The numerical model was solved by VOF method and verified by experimental data. The results show that the thermal uniformity can be improved by the vapor chamber. The temperature difference of the heating surface can be kept within 2.72 K, which is related to the heat and mass transfer process of working medium in the vapor chamber. With the impact of the temperature rise of the coolant, there is a directional flow of vapor phase in the longitudinal direction inside the vapor chamber. The heat energy of the vapor phase can be transported from the high-temperature region to the low-temperature region. Therefore, the influence of cooling water with large temperature rise on the temperature distribution of surface can be suppressed, and the thermal uniformity can be improved.

Abstract:To study the dynamic characteristics of a droplet impact on a supercooled surface and the influence of different parameters on the spreading process of the droplet, the spreading behavior of a single water droplet impacting on a silicon surface has been experimentally investigated. Various impact velocities and droplet sizes are employed to enlarge the Weber number range. Results show that under the subcooling condition of the surface, the droplet spreading dynamics with the increasing of surface temperature exhibits a complex dependence on the Weber number. For a small Weber number (We<190), the maximum spreading factor shows a monotonic increase with the decreasing of surface subcooling due to a smaller liquid viscosity and surface tension. In the high Weber number region (We>190), the maximum spreading factor first decreases and then increases with the decreasing of surface subcooling. The non-monotonic relationship is ascribed to the competition between the decreased non-dimensional maximum fingering length and the increased maximum interior spreading factor with the increasing of surface temperature. In the case of We=209, the surface temperature increases from -36.6 ℃ to -27.6 ℃, resulting in 5.9% decrease of the maximum spreading factor. A relatively high Weber number leads to the formation of a fingering pattern, and a low surface temperature strengthens the phenomenon attributed to the enhanced deceleration of the liquid film. The moment at the maximum spreading diameter weakly increases with the surface temperature and strongly increases with the droplet size, while it barely increases with the impact velocity.

Abstract:To improve the tribological properties of lubricant oil and enhance the stability and security of mechanical equipment under severe working conditions, the friction reduction and anti-wear performance of nano-calcium borate (CaB) and molybdenum dialalkyl dithiophosphates (MoDDP) composite additives were studied using four-ball tester and block on ring tester. The results showed that the prepared nano-CaB was a nanosheet with irregular shape and the average size was 50-150 nm. After oleic acid modification, it showed good dispersion stability in base oil. Both nano-CaB and MoDDP could significantly improve the lubrication effect of lubricant oil. With the increasing of nano-CaB and MoDDP mass fraction, the friction coefficient and grinding spot diameter firstly decreased and then increased. The optimal adding mass fraction of nano-CaB and MoDDP was 2.0% and 1.5%, respectively. Compared with single addition of CaB and MoDDP, compound CaB/MoDDP could further improve the friction reducing and anti-wear performance of lubricant oil. The optimal mass fraction ratio of MoDDP and CaB is 1.5%∶3.0% that showed the smallest friction coefficient and grinding spot diameter, and the highest maximum nonseizure load. It also showed excellent lubrication effect under low speed and heavy load condition.

Abstract:The bearing monitoring data under different working conditions have different distributions, which affect the accuracy of bearing intelligent diagnosis methods. Aiming at this issue, a multi-domain deep adversarial transfer network is proposed for intelligent diagnosis of bearings based on deep learning and transfer learning. The proposed method treats the datasets under different working conditions as belonging to different domains. In the method, firstly, the deep residual network is used to extract the features from source training data and target testing data. Then, multiple domain adversarial modules are designed to capture multi-mode structures from the source and target domain data, which enable fine-grained alignment of the distribution of the source domain and target domain data. Finally, the fault classifier is trained to transfer fault diagnosis knowledge of source domain to the target domain and ensure the diagnosis accuracy under variable working conditions. The proposed method is verified by using the two bearings dataset under variable working conditions. The results show that the proposed method can capture the multi-mode structures of the bearing data and extract domain invariant features, thus improving the fault diagnosis accuracy under variable working conditions compared with other related methods.

Abstract:Aiming at the problem that the key parameters of rotor modal dynamic balance, which are rotor imbalance and bearing characteristic parameters, are difficult to determine, a method for simultaneous identification of bearing characteristic parameters and rotor distribution unbalance parameters based on the vibration response at the bearing was proposed. This method used a polynomial function to describe the eccentricity curve of the rotor mass for characterizing the continuously distributed unbalanced mass of the rotor; established the motion differential equations of substructures in the system with the finite element method; converted the continuously distributed generalized unbalanced force into the concentrated generalized unbalanced force of nodes through the principle of virtual work and established the relationship between concentrated unbalanced force and eccentric curve coefficients, thereby deduced the simultaneous identifying equation of bearing characteristic parameters and mass eccentricity curve coefficients, and then realized the identification of bearing characteristic parameters and distribution unbalance parameters based on the vibration response of the bearings at different speeds. Taking a rotor-bearing system as an example, the sensitivity of the eccentric curve order to parameter identification was simulated, the results show that the order of the eccentric curve has little effect on the parameter identification results. The first-order modal dynamic balance experiment was carried out with the parameters identified from the response of the measured bearings and vibration at the bearings significantly reduced after balancing, which verifies the proposed identification method and its effectiveness in model dynamic balance.

Abstract:Aiming at the problem of robotic picking in the scenario of stacked cluttered objects, an unordered picking system from target screening, recognition to 6D pose estimation was established. The Locally Convex Connected Patches method was used to segment the stacked cluttered objects collected by Kinect V2 camera into separate subsets of point cloud, and the uppermost unshaded object was selected as the target to be captured by defining the capture fraction, so as to ensure that robot could grasp the object from top to bottom. According to the picking requirements of different kinds of objects, 3d targets are identified and grasping points are located based on matching similarity function. An object 6D pose estimation model is established by combining TEASER(Truncated least squares Estimation And SEmidefinite Relaxation) algorithm and ICP(Iterative Closest Point) algorithm to ensure accurate registration of target point cloud and model point cloud under low coincidence rate. Experiments of 6D pose estimation and robotic unordered picking are carried out on self-collected data. The results show that the proposed 6D pose estimation method can obtain the 6D pose of the target more quickly and accurately compared with several popular methods. The root mean square distance error is less than 3.3 mm and the root mean square angle error is less than 5.6°. The visual processing time is far less than the movement time of robot arm, and the whole process of robotic real-time grasping is accomplished in the actual scene.

Abstract:To meet the quality requirements of "Dead Flat" rectangular section super flat material such as wide electrical steel sheet in the new generation of high-tech tandem cold rolling mill, an integrated simulation model of 6-high tandem cold rolling mill was established by explicit dynamic finite element method. The accuracy of the finite element model was verified by field industrial rolling test data. The influence of different rolling factors on the crown of load roll gap in complete rolling process of electrical steel is analyzed quantitatively. Based on the shape control mechanism of 6-high UCM cold rolling mill and EDW-N(Edge Drop Control Work Rolls for Non-shifting of the Work Rolls) work rolls independently designed by our research group, the bending force mathematical model of rectangular section control of electrical steel in 6-high tandem cold rolling mill was established. The parameters of the bending force mathematical model were determined by finite element simulation and field industrial rolling test data, and its accuracy was verified. The continuous test feedback data of a large 1 420 mm six-high tandem cold mill show that the high precision average C15≤7 μm ratio of electrical steel has been increased from 38.58% to 67.74%, which gives full play to the high precision shape control ability of the 6-high tandem cold rolling mill and can control the shape quality in a wide range. It provides innovative solutions and implementation paths for solving the bottleneck problem of rectangular section control of 6-high UCM cold rolling mill for non-shifting of the work rolls.