Taking the valve control cylinder system controlled by proportional relief valve and proportional speed-regulating valve as the research object, this paper established a dynamics model of hydraulic system. The friction force of propulsion hydraulic cylinder was compensated based on LuGre model. The bristly observer was established to estimate the motion characteristics of the spool and the stability of the observer was proved by Lyapunov first method. The uncertainty of hydraulic system was integrated with external load interference, and the adaptive rate was estimated. Based on the inverse integral adaptive control algorithm, a pressure-velocity compound control strategy was proposed and the stability of the control strategy was verified. Based on the hydraulic cylinder speed control, the pressure error was introduced into the speed expectation to realize the pressure-flow compound control of valve control cylinder system. The co-simulation platform of the valve-controlled cylinder system was established in AMESim and Matlab, and the speed regulation, sudden load and load disturbance of the valve-controlled cylinder system were simulated and analyzed under different error proportions. The simulation results show that the pressure-velocity composite controller has good control performance under the conditions of speed regulation, sudden load and load disturbance of the valve control cylinder system. The overflow control of proportional relief valve effectively reduces the fluctuation and overshoot of system pressure. Overchanging the proportion of pressure error can effectively change the distribution of pressure and velocity error when the formation changes abruptly. In practical engineering, the distribution of compound control error can be carried out by changing the proportion of pressure error according to the need.

30CrMnSiA thin-wall cup-shaped part is a key basic component widely used in the flexible gear of harmonic reducer. Aiming at the problem of the low bearing capacity and short service life of harmonic reducer caused by insufficient strength and toughness of 30CrMnSiA thin-wall cup-shaped parts manufactured by traditional turning method, this paper proposed a plastic deformation-heat treatment process which consists of spinning, quenching, tempering, spinning and aging to manufacture 30CrMnSiA thin-wall cup-shaped parts with less or no cutting and excellent mechanical properties. Through the tensile and impact experiment, by comparing the mechanical properties of each process part, the microorganization of each process part was analyzed. The results show that tempered sorbite microstructure with high strength can be obtained by spinning-quenching and tempering process, but the plasticity was reduced significantly. The fibrous microstructure of spun parts can be further refined by aging heat treatment, and the fine carbides precipitated and uniformly distributed on the ferrite matrix. High strength and good plasticity can be obtained by subsequent aging at 300 ℃ for 6 h. As compared with parts obtained by turning forming after quenching and tempering heat treatment, the yield strength and tensile strength of 30CrMnSiA thin-wall cup-shaped parts manufactured by plastic deformation and heat treatment are improved by 93.65% and 47.88%, respectively. The hardness is increased by 26.87%, and the impact strength is increased by 12.01%. Meanwhile, the elongation and percentage reduction of area are 11.60% and 24.64%, respectively. The thin-wall cup-shaped parts with high strength and toughness can be manufactured by the plastic deformation and heat treatment process of spinning-quenching-tempering-spinning-aging, which provides a new method for manufacturing the thin-wall cup-shaped parts with high-strength and toughness.

In order to overcome the difficulty in accurate prediction of the dynamic wear of tooth profile of precision RV reducer for industrial robot, this paper took BX-40E reducer as an example, obtained the wear coefficients under different position conditions through equivalent experiment based on the generalized Archard wear formula, with the consideration of the influence of different position conditions after the wear evolution in the wear prediction process. According to the deformation coordination theory and Langkali-Nikraves contact force model, the load distribution and contact pressure between teeth were determined. Considering the time-varying tooth profile wear and meshing force excitation, the numerical calculation model of dynamic tooth profile wear of transmission system was established by analytical modeling method. As compared with the tooth profile wear curve with the constant wear coefficient, both the wear value and the tooth surface distribution are significantly different, and the overall difference increases with the increase of wear times. The accuracy and necessity of quantifying the tooth surface wear with the wear coefficient taking into account the difference of contact position conditions were obtained. The wear depth curve of cycloid gear and needle teeth presents an asymmetric and irregular inverted “W” shape along the tooth profile. Due to the wear, the teeth near the tooth root and tooth top first fall off and then mesh, resulting in impact and micro protrusion peak. There is almost no wear at the concave convex transition position of cycloid tooth profile. With the increase of wear times, the wear peak area becomes narrower, and the non-uniform increase of wear rate slows down. There is a functional mapping relationship between the meshing force and the pressure angle. The results of the study provide a theoretical basis for improving the wear reduction and vibration reduction of cycloidal needle gear.

The three-parameter Weibull distribution is widely used to describe product longevity because of the convenience and adaptability of its mathematical processing. The three-parameter Weibull distribution with location parameter is one of the most suitable models for studying the reliability of mechanical components, especially for long-life and high-reliability products. Parameter estimation of three-parameter Weibull distribution has always been the focus of attention. This paper proposed an iterative method based on least squares to estimate the parameters of the three-parameter Weibull distribution. The initial location parameter was set to 0, the initial shape parameter and scale parameter were obtained by using least squares, and the new location parameter was obtained by substituting them into the unbiased estimation of the location parameter, and multiple iterations were performed. In this process, the shape parameters and scale parameters gradually become smaller and the location parameters gradually become larger, and finally the stable shape parameters, scale parameters and location parameters were obtained, which are the final parameter estimates, and the lifetime of 99% reliability was calculated. The method was proved to be convergent by Monte Carlo simulation. Compared with the correlation coefficient method by two metrics including Bias and Root Mean Square Error (RMSE) for different Weibull models with different small and medium sample sizes (10, 15, 20, 25 and 30), the three estimated parameters and the 99% reliability of the lifetime of the proposed method are more accurate. The analysis of two examples shows that the method is feasible and valid. Compared with the correlation coefficient method, the estimation results are more conservative and more suitable for engineering application.

With the development of science and technology and the needs of life, flexible gripper technology has gradually become a research hotspot because of its safety and compliance. As a plant that can realize envelope grasping, the movement characteristics of flytrap grass have strong reference for the grasping movement of flexible grippers. According to the soft mesh structure and the deformation mechanism of the Venus flytrap, this paper proposed a hydraulically driven bionic Venus flytrap flexible gripper structure composed of double bionic blades. Firstly, a mathematical model of the relationship between the bending angle and the pressure of the fully embedded single-column grid was analyzed based on the simulation model, and then the relationship between the bending angle and the pressure of the multi-column grid was analyzed based on the simulation model, and the working pressure of the flexible gripper was determined to be 0.040 MPa. The analysis of simulation results shows that the bending angle change and force of the incomplete edge mesh are greater than that of the complete mesh, which proves that the incomplete mesh is the weak point of the strength of the flexible gripper. The bending experiments and closing force experiments of the hydraulically actuated and pneumatically actuated bionic blades were carried out, and it was proved that the performance of hydraulic actuation was better than that of pneumatic actuation under working pressure, and the ready pressure of the flexible gripper was determined to be 0.010 MPa. Finally, adaptive experiments show that the designed flexible gripper can grasp objects of different shapes, and the maximum load capacity is confirmed to reach 304.3 g. The hydraulically driven bionic Venus flytrap flexible gripper proposed in this paper can provide an effective solution for live insect capture and non-destructive harvesting, as well as a theoretical and technical basis for the research and development of bionic plant robots.

The manipulator with five degrees of freedom (5-DOF) cannot reach any pose, so it is easy to get no solution when the traditional pose description method is used to solve the inverse kinematics. In this paper, a 5-DOF manipulator consisting of four rotary joints and one prismatic joint, which is suitable for cleaning, spraying, welding and other operations, is taken as an example to establish a kinematic model and its inverse kinematic analysis is carried out. Then, an inverse kinematics solution method based on joint angle parameterization combined with the feasible direction of approach vector is proposed based on the end pose description of degree of freedom constraints. In this method, firstly, the motion space of the end executor is reduced from three dimensions to two dimensions through joint angle parameterization. Then, the feasible direction of the approach vector of the end executor at different target positions (distal, middle and proximal) is analyzed by geometric method, so as to avoid blind parameter setting and ensure the existence of inverse kinematics solutions. Thereafter, the optimal solution is selected according to the motion continuity and motion range of each joint. The simulation analysis results of path planning show that the actual path is very consistent with the planned path and the joint motion is stable, which proves the feasibility and accuracy of the proposed solution method. The 5-DOF manipulator studied in this paper is representative to some extent and the proposed solution method possesses the advantage of low computational complexity and simple solving process. Therefore, the solution idea can provide reference for the inverse kinematics solution of the manipulator with less degrees of freedom.

The traditional analysis method is not practical in the power prediction and parameter optimization analysis of low temperature differential Stirling engine. In order to predict the output power of low temperature differential Stirling engine quickly, this paper studied the application of the second order Simple model in the thermodynamic cycle analysis of low temperature differential Stirling engine. It described the simplified structural model of low temperature differential Stirling engine and the temperature characteristics of internal working medium. Based on Simple model, this study derived the actual heat transfer equation of non-ideal heat exchanger in low-temperature differential Stirling engine, and analyzed the heat return loss, pumping loss and actual heat transfer of heat exchanger. The variation of the temperature, pressure and energy of the working medium in the low-temperature differential Stirling engine system with the crank Angle was illustrated by examples, and the theoretical output power of the low-temperature differential Stirling engine was analyzed. The actual output power of low temperature differential Stirling engine at different heating temperatures was compared with the calculated power of Simple model. The comparison results show that the error between the output power calculated by the Simple model and the actual output power is small, indicating that the Simple model is in good agreement with the actual cycle of the low-temperature differential Stirling engine. In order to study the influence of regenerator on engine performance of low temperature difference Stirling engine, the paper optimized the structure of regenerator of low temperature difference Stirling engine. The output power of the regenerator after optimization was compared with that before optimization. The comparison results show that after optimizing the regenerator, the actual output power of the low-temperature differential Stirling engine and the calculated power of the Simple model are both increased by 20%. It is shown that optimizing the structure of regenerator is an effective method to improve the performance of low temperature differential Stirling engine.

Multi-modal data fusion of LiDAR (Laser Imaging, Detection, and Ranging) and binocular camera is important in the research on 3D reconstruction. The two sensors have their own advantages and disadvantages, and they can complement each other through data fusion to obtain better reconstruction results. In order to achieve data fusion, firstly it is necessary to unify the two data into the same coordinate system. The calibration results of the external parameters between the LiDAR and the camera are very important to 3D reconstruction. Due to sparse LiDAR point cloud and its positioning error, it is a challenge to extract feature points accurately for constructing accurate point correspondences when calibrating extrinsic parameters between LiDAR and stereo camera. In addition, most calibration methods ignore that LiDAR works on spherical coordinate system and directly use the Cartesian coordinate measurement results for calibration, which introduces anisotropic coordinates error and reduces the calibration accuracy. This paper proposed a calibration method by minimizing isotropic spherical coordinate error. Firstly, a novel calibration object using centroid feature points was proposed to improve the extraction accuracy of feature points. Secondly, the anisotropic LiDAR Cartesian coordinate error were convert into the isotropic spherical coordinate error, and the extrinsic parameters were solved through directly minimizing the spherical coordinate error. The experiments show that the proposed method has advantages over the anisotropic weighting method. The method ensures that the solution is globally optimal and the number of calibration samples required is greatly reduced on the premise of sacrificing some accuracy. With the optimal calibration error of 2.75 mm, the amount of calibration data can be reduced by about 54.5% by sacrificing 3.6% accuracy using the proposed method.

The microstructure variations of machined surface determine the performance of machined components. Accurately predicting the microstructure evolution of machined surface and thus enhancing surface hardness of machined components is an effective way to improve the service performance and realize the controllable machining of components. Machining is one the fundamental manufacturing techniques of TC4 components and the severe plastic deformation during machining process induces the complex evolutions of microstructure for TC4 machined surface. For the grain refinement phenomenon during TC4 cutting, this paper studied the multi-scale distribution characteristics of microstructure, evolution mechanisms of grain refinement and its effect on the material hardness under different cutting speeds (100 ~ 500 m/min). The results show that grain refinement degree at meso-scale (10^-6 ~ 10^-5 m) increases first and then decreases with the increasing of cutting speed. At cutting speed of 300 m/min, grain refinement degree of machined surface is 69.7% and the grains in the shear bands of chips are refined to 2 ~ 6 μm. Complex dislocation patterns and nano twining are the features of microstructure at micro-scale (10^-8 ~ 10^-7 m). The deformation twinning type is mainly characterized as {10\bar{\mathrm{1}}1} compression twinning and it is generated at higher cutting speed (> 200 m/min). Grain refinement during machining of TC4 was predicted based on the modified Z-H grain refinement model and nano twining volume fraction prediction model. The hardening effect of grain refinement was also considered in the prediction model. The evolution of grain sizes and the work hardening was predicted. The relation between grain refinement and material hardness was established, and the hardness of TC4 machined surface was predicted with directional controlling the grain refinement degree and formation of nano twinning. And the hardening mechanism in micro-scale of TC4 machined surface was revealed.

With the development of modern technology, the automotive and aerospace fields are pursuing the lightweight of materials, and the high strength and high toughness of materials is the basis of lightweight. 7000 series aluminum alloys (Al-Zn-Mg-Cu series aluminum alloys) have the advantages of high strength, high hardness, good corrosion resistance, et al. Among all aluminum alloys, 7055 aluminum alloy has the highest strength. The common preparation method of 7055 aluminum alloy is spray forming process. Stable growth of the aluminum ingot during deposition is the basis for the preparation of large-size ingots with uniform deposition quality by the spray forming process. Due to the variation of numerous process parameters during the jet forming process, the existing theoretical model is difficult to meet the requirements of quality control in the actual production process. This paper built a GA-BP neural network prediction model for the diameter and a model for regulating the growth rate of the ingot billet based on the correlation analysis between the historical data of the injection molding process and the diameter of the deposited surface of the ingot billet, by combining BP neural network and genetic algorithm. Based on the real-time fluctuation of process parameters, the diameter variation was calculated and used as an input layer into a trained velocity regulation neural network model to optimally regulate the lifting speed of the deposition substrate, resulting in a uniform and stable deposition growth profile of the ingotst. Finally, this method was used to regulate the growth rate of ingots. The results show that the deviation of large-size ingot diameter is within 5%, which verifies the feasibility of growth rate regulation.

Micro-Electro-Mechanical System (MEMS), also known as microsystem or micro-electro-mechanical system, is a high-tech micro device or system developed on the basis of microelectronic technology. MEMS integrates photolithography, corrosion, LIGA, silicon and non-silicon surface micromachining, precision machining and other technologies, and its size is on the micron scale. The microsensors produced by micromachining technology are widely used in engineering practice because of their simple structure, high sensitivity and stable operation. The microsensor usually uses electrostatic excitation and capacitance detection to detect the signal, that is, the displacement change of the resonator during vibration leads to the change of the distance between two electrodes, so as to change the capacitance between electrodes, thus the detected capacitance change frequency is the frequency of resonantor vibration. A cross microresonator was proposed to solve the problem of weak capacitance signal and low detection accuracy of microsensor. To study the multi-field coupling effect of microresonator, the multi-field coupling nonlinear dynamics equation of harmonic oscillator was established considering Van der Waals force and electric field force. The dynamic displacement of nonlinear vibration was obtained by using Linz Ted-Poincare method, and the influence of multiple physical field parameters on mean vibration displacement and capacitance variation of the harmonic oscillator was analyzed. The cross microresonator was fabricated by micro-nano machining, and the capacitance variation resulted from resonant frequency and vibration displacement was measured by electrostatic excitation-capacitance detection method. The results show that the cross microsensor increases the plate area, thereby aggrandizing the capacitance variation, and thus the signal intensity becomes stronger. When the plate area increases by 75%, the capacitance change is 4.2 times of the original, and the signal intensity increases by 5.0 times, so it is more convenient for capacitance detection.

Magneto-elastic abrasive is magnetic and has low elastic modulus as well as excellent grinding performance. It can improve the quality and efficiency of process. Firstly, the magnetic edge preparation mechanism was analyzed based on the theory of magnetic field and magneto-elastic abrasive characteristics. Secondly, secondary development for discrete element software EDEM was carried out based on magnetic force of magneto-elastic abrasive in magnetic field, and a simulation model of dual-disk magnetic edge preparation process was established. The effects of particle size, magnetic susceptibility and disk spacing on the number of edge collisions and abrasive rotation velocity were studied. Finally, Matlab software was used to reconstruct the edge contour and an improved shape factor characterization method based on preparation area was proposed. The influence of particle size, magnetic susceptibility and disk spacing on edge preparation value was studied by orthogonal experiment, and the feasibility of proposed improved shape factor characterization was verified. The results show that, the number of edge collisions and the rotation speed of abrasive increase with the increase of particle size, the increase of magnetic susceptibility and the decrease of disk spacing. In addition, the degree of influence of preparation parameters on the preparation amount of the cutting edge in descending order is particle size, disk spacing and magnetic susceptibility, and the optimal preparation parameter groups are particle size 40 mesh, magnetic susceptibility 0.1, and disk spacing 15 mm. The maximum relative error of preparation area between simulation and experiment is 16.33% and the minimum relative error is 0.42%. Simulation can better predict preparation morphology of the cutting edge, and the improved edge shape factor can better characterize the preparation morphology of the cutting edge.

Sliding bearings in mixed lubrication state are prone to wear due to deformation or misalignment under low-speed conditions. In order to analyze the influence of journal misalignment and wear on the mixed lubrication characteristics of sliding bearings, this study established a coupled model of average flow equation, G-T contact equation and Archard wear equation considering journal misalignment and elastic deformation. The bearing characteristic parameters and time-varying wear parameters under mixed lubrication were calculated by finite difference method and over-relaxation iteration method. The lubrication performance of bearings before and after journal misalignment or wear was compared, and the effect of roughness and boundary friction coefficient on various performance parameters was analyzed. A friction and wear test rig was built to test the lubrication characteristics of bearings in misaligned state, which verified the correctness of the theoretical model. The theoretical analysis and experimental results show that, when heavy load and large eccentricity occur, the bearing will change to mixed lubrication state. The greater the journal tilt, the more likely the bearing to have mixed lubrication. When the bearing is misaligned, the peak pressure and the shape of contact area will change, resulting in a difference in wear and the distribution of wear depth is tilted either axially or circumferential. The wear reduces the fluid hydrodynamic effect and decreases the film thickness ratio, leading to a decrease of about 20% in the hydrodynamic pressure peak, a decrease of about 90% in the contact pressure peak, and a maximum decrease of about 19.71% in bearing capacity. By comparing the bearing morphologies before and after wear, it finds that the journal tilts leads to that the wear concentrates on the end where the clearance reduces. This research provides theoretical basis for sliding bearing design in practical engineering.

In order to analyze the interaction between the vibration of vibrating screen and the movement of particles and reveal the influence of vibration parameters on the dynamic characteristics of the system, this paper establishes a model for the coupling of vibration sieve system dynamics and particle dynamics. By using this model, real-time bi-directional coupling simulation of screening process can be realized, and the accuracy of the simulation model is effectively improved. The steady-state particle distribution at each layer of screen is obtained based on the actual screening yield which is calculated in terms of screen test. As compared with the uncoupled model, the model considering the coupling of vibrating screen and particle dynamics can obtain more accurate force analysis, and enhance the material throwing of the sieve body, avoiding the particle accumulation of each layer in the traditional simulation, which is more consistent with the actual screening situation. Meanwhile, the coupling analysis also indicates that the maximum impact force of materials does not decrease as the number of screen layers decreases. Finally, the variation law of material impact force with the main parameters of vibrating screen is studied. The results indicate that the impact force of the particles not only varies as the proportion of screen surface area, but also relies on the residence time of the particles on the screen; the impact force of the particles decreases with the increase of the inclination angle of screen surface. When the vibration direction angle is within 57°to 90°, the magnitude of the impact force shows an inverted V-shape. The results provide a theoretical guidance for the dynamic optimization design and noise reduction of vibration screen.

In-mold hot-pressing is a common drying method in the production of pulp moulded tableware. The wet paper mold embryo obtained after moulding is heated under the condition of extrusion and vacuum. Heating plate is the heat source of hot-pressing machine, and the temperature uniformity of its working surface affects the drying quality of products. Aiming at the temperature non-uniformity of the heating plate in the process of pulp molding hot pressing, this paper proposed an optimization method which combined simulation and orthogonal experiment. Firstly, the working process of heating plate was analyzed and the heat transfer model of heating plate was established. Then, based on Fluent, the temperature field was simulated numerically. According to the results of temperature field distribution, the high-temperature area and low-temperature area in the oil circuit structure were staggered as far as possible, and four new labyrinth oil circuit structures were designed. Finally, an orthogonal test with 4 factors and 4 levels was designed based on the structure of oil circuit, the plane height of oil circuit, the thickness of heating plate and the section diameter of oil circuit, and the range analysis and variance analysis were carried out. The results show that during the actual drying process, the maximum temperature and minimum temperature of the working surface are 224.47 ℃ and 209.92 ℃, respectively, and the temperature range is as high as 14.55 ℃ and the temperature standard deviation is 3.01 ℃. The thickness of heating plate and the diameter of oil passage have a significant influence on the temperature difference, and the structure of oil passage has a significant influence on the temperature standard deviation. Based on the above analysis, the structure of heating plate was improved. Compared with the original design, the temperature range of the working surface of heating plate has been reduced to 7.27 ℃ and the temperature standard deviation has been reduced to 1.09 ℃, which ensures the uniformity of temperature of heating plate and improves the quality of pulp molded products.

The processing difficulties of UHMWPE caused by the wall slip can be solved effectively by the eccentric rotor extruder, which make the melt conveyed in positive displacement. To reveal the melt flow characteristics of UHMWPE in the conveying section of the eccentric rotor extruder, the model parameters of wall slip were determined by the combination of experiment and numerical simulation, and the flow field of UHMWPE melt was numerically simulated by ANSYS Polyflow. The results show that the UHMWPE melt in the cavity formed by the meshing of the rotor and the stator can be conveyed in positive displacement, and the change in the cross-sectional size of the cavity leads to the elongation flow field in the melt. When the meshing gap exists, the positive pressure and negative pressure formed around every inlet and outlet respectively, will lead to the counterflow and leakage of the melt in the cavity and make the average flow rate at the outlet of the cavity lower than the theoretical flow rate. When UHMWPE is processed by the eccentric rotor extruder, the instantaneous flow rate and average flow rate of the melt at the outlet of the cavity are proportional to the rotor rotation speed, while the pulsation rate of the flow rate remains unchanged. Reducing the meshing gap between the rotor and the stator increases the average flow rate of the melt at the outlet of the cavity and decreases the pulsation rate of the flow rate, which enhances the positive displacement conveying of the melt in the eccentric rotor extruder.

In order to explore the application of metal nanoparticles to the repair of microcircuits with multi-conducting elements and to analyze the motion trends during the dielectric serial assembly of nanoparticles, the dielectrophoretic serial assembly behavior of nanoparticles in a non-uniform electric field is investigated based on a multi-gap nanoelectrode system. In the investigation, first, the particle dielectrophoretic assembly experiments of the conductive island microelectrode system were conducted, finding that the molten nanoparticle wires obtained from the assembly could enhance the circuit conductivity. Then, a comparative experiment of dielectrophoretic serial assembly was conducted for the double-gap and the multi-gap serial nanoelectrode systems, finding that, with the increase of the number of conducting islands in the system, a body assembly phenomenon occurs in all nano-gaps, which helps realize the connection of conducting elements within the multi-gap serial nanoelectrode system. Finally, a simulation analysis was carried out not only for the electric field distribution but also for the dielectrophoretic force, alternating current electrothermal flow and their combined force during the dielectrophoretic assembly of nanoparticles. The results show that the average values of the dielectrophoretic force and the alternating current electrothermal flow inside the gap are both higher than those outside the gap at a frequency of 150 kHz; and that nanofluid pumping occurs in any gap of the multi-gap serial nanoelectrode system and the nanofluid pumping is not affected by the number of gaps. Moreover, the emergence of nanofluidic pumps indicates that metal nanoparticles in non-uniform electric field have an tendency of bulk and surface assembly during the dielectric serial assembly, and this tendency may directly affect the quality of generated nanoparticle wires.

Aluminum alloy materials are widely used in the fields such as aerospace, automotive manufacturing and shipbuilding. However, the load stress and residual stress during the manufacturing and equipment process directly affect the mechanical properties and fatigue life of aluminum alloy components. In this paper, for the purpose of evaluating the internal stress of aluminum alloy and on the basis of acoustic elasticity principle, the phased array longitudinal-wave detection technology was studied, and an internal stress detection method of aluminum alloy was set up based on the time difference during longitudinal wave propagation. Then, an experimental system for phased array longitudinal-wave ultrasonic stress detection was set up, and calibration experiments were carried out to reveal the linear relationship between the internal stress of aluminum alloy and the time difference during longitudinal wave propagation, with the correlation equations being also formulated. The results show that, within the tensile stress range of 0~286 MPa, the absolute calibration errors of 5 mm and 3 mm aluminum alloy plates are respectively less than 2.85 MPa and 10.82 MPa, the corresponding relative errors are respectively not more than 2.36% and 13.93%, and the maximum relative errors of both specifications occur within the stress range of less than 28.58 MPa, meaning that it is necessary to improve the resolution and accuracy of ultrasonic measurement in small stress detection. The phased array longitudinal-wave system was then used to detect the stress 5 mm aluminum alloy plate specimens, and an average stress error of (1.174±4.567) MPa, an absolute error of less than 9.42 MPa as well as an estimated initial residual stress of 3.329 MPa was obtained. The experimental results show that the proposed phased array longitudinal-wave ultrasonic method is effective in detecting the average stress of 5 mm aluminum alloy plate; that the method based on the time difference during longitudinal wave propagation can be used to detect the stress type, stress size and residual stress; and that the proposed method is effective in improving the detection accuracy and efficiency of the internal stress detection of aluminum alloy.

Bearing is one of the most widely used rotating parts in industrial equipment. If the bearing runs in fault condition for a long time, it will cause huge economic loss and threaten personal safety, so that the investigation of bearing fault diagnosis is of great significance. Fault diagnosis technology based on deep learning is becoming more and more mature, but there are problems such as over-fitting, unstable effect and low accuracy in the case of small samples. In order to solve these problems, this paper proposes a Transformer variant model MDT (Multi-Head Convolution and Differential Self-Attention Transformer) to realize end-to-end few-shot fault diagnosis. This model combines the new data embedding algorithm of MC (Multi-Head Convolution) and the DSA (Differential Self-Attention) mechanism. The MC algorithm performs multi-path one-dimension convolution on the sample, extends the sample from one dimension to two dimensions by multi-channel output, and extracts rich fault information in each frequency domain in the original sample through multiple convolution kernel sizes. As compared with the original dot product self-attention in Transformer, the DSA mechanism obtains the corresponding attention weight vector for each feature through the difference, so as to extract deeper fault features from the sample. MDT inherits the powerful ability of Transformer to process sequence data, which can extract richer fault information from time-domain signals and avoid the overfitting problem common in small-sample models. Experimental results show that the proposed method can stably obtain more than 99% test accuracy in the bearing fault diagnosis task with only 100 training samples per fault type, and has strong anti-overfitting ability and strong robustness.

As China’s nuclear industry enters the third 30 years of development, the maintenance need for nuclear equipment is becoming increasingly urgent. The internal structure of the nuclear steam generator is complex, and the key structure, namely the heat transfer tube, has the restrictions like small diameter, long pipeline and difficult disassembly and installation, which make traditional repair methods extremely difficult in implementation. In order to solve the problem of corrosion damage of small-diameter nuclear heat transfer tube due to long-term high temperature and high pressure condition, an all-position automatic TIG welding gun for liner repair was designed in this paper, and the gun reliability verification and welding repair test were carried out. Firstly, the overall structure design of the welding gun was presented, and the advantages of the designed welding gun comparing with the traditional tungsten electrode TIG welding gun were described. Next, the design and verification of the welding gun transmission system with small size and high space utilization were completed. Then, the stiffness of the key part of the welding gun, namely the conductive shaft, was modelled, analyzed and calculated, and the reliability of the theoretical model was verified by finite element solution. On this basis, an optimization method of the welding gun structure was proposed. Moreover, the field test of deflection and the welding test were carried out, finding that the stiffness of the conductive shaft satisfies the field welding conditions. Finally, linear regression equations and deflection correction formulas were used to quantitatively predict the deflection of the welding gun, and the results verify the rationality of the designed structure. Welding tests results show that the rotation speed of the transmission system is stable and controllable in working condition of welding gun, and the welding seam is well formed. The developed liner welding gun can satisfy the requirements of liner welding repair of the stainless-steel heat transfer tube inside the nuclear steam generator.

The position control of robot manipulators has been recognized as the most fundamental and simplest objective in the robotic control field. For the high-precision position control problem of the multi-axis robot system, this study proposed a simple output feedback nonlinear PD plus gravity compensation (PD+) synchronization position controller combining with the cross-coupling techniques. The global finite-time stability of closed-loop systems was strictly demonstrated by applying Lyapunov stability theory and geometric homogeneity techniques. Compared with the asymptotic stable full-states feedback control schemes, the presented controller ensures the finite-time stability of the robot manipulators with position measurements only; compared with the output feedback asymptotic stable controllers, the proposed controller ensures the finite-time convergence of robot’s states; compared with the output feedback controllers without synchronization term, the proper introduction of nonlinear synchronization control items enables the proposed controller to take into account the synchronous and coordinated motion between the axes on the premise of ensuring the high-precision position control of the multi-axis robot system. The proposed controller has the advantages of simple structure, easy implementation, faster response speed and better overall system performance, which meets the high precision requirements of actual production for the robot system. Numerical simulation results demonstrate the effectiveness of the proposed control algorithm and the expected performance of the system. The proposed control method not only ensures the global output feedback finite-time stable synchronization control of multi-axes robot systems, but also provides an effective alternative approach for the output feedback synchronization position stabilization of a large class of nonlinear second-order systems.