The hotspot temperature of transformers has a direct impact on the reliability and stability of the power grid system. In response to the problems of complex traditional transformer management mode and high cost, low computational efficiency and high computational error in the transformer hotspot temperature prediction methods, a transformer hotspot temperature prediction and warning technology based on digital twin is proposed. Firstly, a six-dimensional digital twin model of the transformer was built to achieve functions such as system data sharing, multi-source fusion and virtual-real interaction. Then, a digital twin system driven by perception-interaction that could support artificial intelligence and machine learning algorithms was constructed. The chaotic adaptive particle swarm optimization (CAPSO) algorithm was adopted to optimize the weights and thresholds of the BP (back propagation) neural network, which accelerated the convergence speed of the original network. Meanwhile, a transformer hotspot temperature prediction model based on CAPSO-BP was established. Finally, the on-site monitoring data of transformers were used for simulation on the virtual engine platform, and the development and application of various functions of the transformer hotspot temperature prediction and warning system were implemented. Concurrently, the feasibility and effectiveness of the prediction model were verified. The research results provide new ideas and theoretical basis for the transformation of the digital twin transformer system from digitalization to intelligence.

Roadway section forming is an important process in coal mine boring process. However, the current roadway section forming operation is mostly carried out through manual control of the roadheader for reciprocating cutting, which restricts the intelligent development of coal mine boring face. Therefore, in view of the problems that the section forming trajectory planning does not consider the characteristics of coal and rock and has a single optimization objective, a trajectory planning method for the roadheader section forming based on the improved grey wolf optimizer (GWO) algorithm is proposed. Firstly, the cutting section environment was divided into four situations according to the location of the gangue, and the corresponding sections were rasterized and the raster maps were established. Meanwhile, the binary expansion method was used to expand the irregular gangue. Then, the GWO algorithm was improved to enhance its optimization performance and convergence speed. Nextly, simulation experiments were carried out to realize the planning of section forming trajectories for roadheader under four environments by using the improved GWO algorithm. Finally, the section cutting experiments were conducted by the roadheader prototype. The simulation results showed that compared with the traditional GWO algorithm, the improved GWO algorithm had a faster convergence speed and higher convergence accuracy. Under the four section environments, the section forming trajectory planned based on the improved GWO algorithm had the shortest length, the smallest under-excavated area and the least number of turns, which made it easier to realize high-precision and high-efficiency trajectory tracking control, thereby ensuring the roadway section forming quality. The experimental results showed that the section forming trajectory planned based on the improved GWO algorithm not only improved the cutting efficiency of the roadheader, but also met the quality requirements of the roadway section forming. The research results can provide new ideas and methods for the development of intelligent boring technology in coal mines.

The stable control of the flowability of 3D printed concrete is significant for improving the forming quality of printed components. The existing approaches to improving printing accuracy mainly focus on the optimization of concrete material properties, the mechanical structure optimization of printing equipment, and the optimization of printing process parameters. But in fact, whether the flowability of concrete is stable or not directly affects the printing quality. Therefore, from the perspective of control, the relationship between the flowability of concrete and the printing accuracy was analyzed first, and the flow stability control system structure for 3D printed concrete was proposed. Then, a PID (proportional-integral-derivative) control strategy based on PSO (particle swarm optimization) algorithm was designed, which could achieve multiple real-time online optimizations of control parameters and improve the stable control performance of 3D printed concrete flowability. Finally, the feasibility and superiority of the designed PSO-PID control strategy were verified through simulation analysis and printing experiments. The simulation results showed that the PSO-PID control strategy could meet the stable control requirements of concrete flowability. The printing experiments indicated that the PSO-PID control strategy could ensure the continuous and uniform extrusion of concrete, effectively improving the forming accuracy of printed components. The proposed method achieves the stable control of concrete flowability by real-time control of mechanical parameters, which can provide technical support for the engineering application of 3D printed concrete technology.

Robots capable of both crawling and jumping demonstrate superior adaptability to complex environments compared to those with a single movement mode. Additionally, their soft actuators offer significant advantages such as large deformation and simple structure. Based on the soft actuation method of dielectric elastomer, a crawling-jumping soft robot was designed. Firstly, a bi-stable dielectric elastomer actuator was designed, consisting of a dielectric elastomer membrane, soft electrodes, reinforcing ribs, and a flexible frame. The actuator exhibited bi-stable states in both transverse and longitudinal directions. Through analysis and experiments, the size parameters of the actuator were determined. Secondly, a bi-stable dielectric elastic actuator was fabricated using VHB4910 dielectric elastic membrane. The influence law of pre-stretching rate of membrane on the dynamic response of actuator was studied, and its output torque was tested. The results confirmed that the actuator could enable the robot to jump. Then, based on the dielectric elastomer actuator, a crawling-jumping robot was designed, comprising a crawling module and a jumping module. The robot was capable of moving straight, turning and jumping. Finally, a prototype of crawling-jumping robot was fabricated and tested. The test results showed that the robot achieved a maximum movement speed of 10 cm/s (equivalent to traveling 1.25 body lengths per second), a maximum turning speed of 12(°)/s, a jumping height of approximately 5 mm, and a jumping distance of approximately 3 cm. These findings provide a novel scheme for structural design and actuation of crawling-jumping soft robots.

At present, robotic fish made mainly of rigid materials have good control accuracy and relatively fast swimming speed in water. However, due to the high rigidity of rigid materials, the robotic fish usually cannot adapt well to the narrow passages in water. To solve the above problems, the origami structure was applied to the structural design of robotic fish, and a soft robotic fish that could pass through narrow passages in water and had good swimming performance was designed. This robotic fish was composed of a head, a trunk and a tail. The trunk part adopted the Water Bomb origami structure, and the radial change of the trunk part was achieved by the contraction and expansion of the origami structure. The tail used the bending of the soft origami driver to achieve swing, thereby enabling the forward movement and turning of the robotic fish. The movement of the robotic fish in the water tank was measured through experiments. Its maximum swimming speed was 72.67 mm/s, the fastest turning speed was 10.67 (°)/s, and it could move stably under the condition of a maximum load of 150 g. The results show that the designed robotic fish can not only move flexibly in water, but also utilize the folding characteristics of the trunk part to pass through some narrow passages and obstacles, which provides a new idea for the design and research of soft robotic fish.

In order to improve the jumping height of multi-legged jumping robot, based on the leg structure and jumping mechanism of jumping spider, a composite jumping robot based on fuselage ejection and leg extension was designed. Firstly, based on the jumping mechanism of jumping spider, the leg structure and ejection device of robot were designed, and the overall structure of robot was modeled using UG 3D modeling software. Secondly, the MD-H (modified Denavit-Hartenberg) method was used for conduct kinematic modeling and analysis of the robot's leg, MATLAB software was used to calculate the working space of the robot's leg, and Lagrange method was used to calculate the dynamics of the leg. Then, a ejection device employing ratchet drive and bevel gear drive was designed, and its energy storage spring was designed according to the law of energy conservation and Hooke's law. Next, the motion control system for the robot was established. Finally, ADAMS motion simulation was carried out, and the results showed that the maximum height was 734.117 6 mm when the robot jumped vertically, and the maximum forward distance was 447.641 7 mm when it jumped forward. The whole motion process took 1.5-2.0 s. A physical model was made using 3D printing technology for experimental verification. The research results show that the composite jumping motion of multi-legged jumping robot can effectively improve the vertical jumping height and forward jumping distance, so the robot has better practicality.

Aiming at the problems that the existing window cleaning robots cannot work normally and have poor cleaning effects on curved glass, an adaptive double-sided window cleaning robot for curved glass has been designed. This robot adopted a dual-machine design, with both bodies consisting of multiple articulated mechanisms equipped with magnetic adhesion devices. The cleaning mechanism was composed of multiple articulated section units. During the process of the robot conforming to the curved glass, the articulated structures between adjacent mechanisms and adjacent section units formed included angles under the drive of magnetic adsorption devices, so as to achieve the self-adaptation of the robot to the curvature of curved glass surfaces. On this basis, the magnetic pole arrangement mode of the robot was optimized, and the curved-surface adaptability and motion stability of the robot were analyzed. The adaptive problem of robot caused by the changes in the thickness and curvature of curved glass was solved, and the constraint conditions for the stable operation of the robot in different postures were obtained. Finally, experimental tests were carried out in the actual working environment of the robot. The results showed that the designed robot had a good adaptive conforming effect and reliable motion stability on curved glass surfaces. The research results provide new ideas and solutions for the further development of curved glass cleaning robot technology.

Aiming at the problem that cracks were prone to occur at the bottom of the self-piercing riveted joint in 2024 aluminum alloy, the crack formation mechanism was analyzed through riveting experiments, and the crack suppression was investigated by combining the annealing and riveting processes of the 2024 aluminum alloy sheet. Meanwhile, the microstructure and mechanical properties of the joints were compared, and the fracture characteristics of the joints were analyzed using scanning electron microscopy (SEM) to explore their failure mechanism, thereby analyzing the influence of heat treatment process on the mechanical properties and failure forms of the joints. The results showed that the plasticity and ductility of the 2024 aluminum alloy sheet increased after annealing treatment at 360 ℃, while the hardness decreased by 23.6%. In the case of riveting the 2024 aluminum alloy sheet without annealing treatment, the crack initiation occurred at the rivet tube leg tip area, and macro cracks appeared along the radial direction at the joint bottom. After annealing treatment, there were no obvious cracks at the joint bottom, which significantly improved the sealing performance and corrosion resistance of the connection point. The grain structure of the joint section in the unannealed group was coarse and irregular, and the deformation at the rivet tube leg tip area was significant. In contrast, the grain structure of the joint section in the annealed group was refined and more uniform. Although the static strength of the joints decreased by 12.93% after annealing treatment, the failure displacement and energy absorption values increased by 27.3% and 19.31%, respectively. The failure mode transformed from complete fracture of the upper plate to tearing of the lower plate, with the bottom of the connection point being pulled through by the rivet clinch. Additionally, the fracture mode changed from brittle fracture to ductile fracture. The research results can provide important references for the application of self-punching riveting process in fields such as automobiles and aerospace.

Insulating materials tend to age, crack and even carbonize in high-temperature environments, resulting in a decline of insulation performance of high-temperature electrical connector and failure to meet the working requirements of equipment. Taking the J58 high-temperature electrical connector of a certain equipment as the research subject, the failure mechanism of its polyimide (PI) insulation part was analyzed and verified.At the same time, the variation of its insulation performance was investigated through high-temperature deterioration test. The results showed that after the PI insulation part was continuously operated at 450 ℃ for 30 minutes, the insulation part showed carbonization trend, and its insulation resistance decreased significantly, but it was still greater than 5 GΩ, which could still meet the working requirements of a certain type of hypersonic missile.The research results provide a basis for the reliability design, selection and later maintenance decisions of high-temperature electrical connector, which is conducive to enhancing the reliability of equipment such as hypersonic missile.

To improve the dynamic response characteristics of high-pressure common rail injectors, a high-pressure common rail giant magnetostrictive injector was designed based on the giant magnetostrictive material rod and the hydraulic reversing mechanism. On the basis of briefly describing the overall structure design and working principle of this injector, considering the nonlinear hysteresis characteristics of its driving part, an electro-magnetic-mechanical-hydraulic multiphysics coupling model was established based on the Jiles-Atherton hysteresis model. Then, a complete simulation model of the injector was constructed. The needle valve signal was selected as the evaluation index for fuel injection response speed, and the optimal preload force of the needle valve spring was determined. Finally, the parameters such as the control piston diameter, the control cavity volume, the oil inlet diameter and the oil outlet diameter were optimized by using the response surface method, and the influence of the optimized parameters on the response time of the injector was analyzed based on the fitting equation. The results showed that compared with before optimization, the opening delay of the needle valve after optimization was reduced by 3.251%, the opening time was reduced by 1.364%, the closing delay was reduced by 9.465%, and the closing time was reduced by 14.848%. The research indicates that the adopted optimization method can effectively improve the response speed of the needle valve, which is conducive to enhancing the small-quantity fuel injection and multiple fuel injection performance of the high-pressure common rail injector.

The deformation characteristics of industrial robot cables are one of the main factors influencing the service lifespan of cables. In order to describe the movement pattern of the cables and mitigate the impact of cable routing on the lifespan of cables, a flexible cable modeling method based on the spring-damper chain equivalent was proposed. The cable was divided through linear springs, linear dampers, torsional springs and torsional dampers, achieving the dynamics description of its particles. And based on the Newton method, the force analysis was conducted for each particle. The cable movement process was discretized into a collection of movements in multiple tiny time intervals. The dynamics parameters at the current moment were obtained through dynamics analysis. After a movement in a tiny time interval, the position of each particle at the next moment could be derived. By iterating the above steps, the dynamic pattern of the cable could be simulated, and the movement simulation of the cable at the joint of industrial robot was realized. Subsequently, the optimal parameters of the cable dynamics model were determined through experiments, and the simulated pattern of dynamics model after parameters optimization was compared with the actual movement pattern of industrial robot cable to validate the accuracy of the dynamics model. Finally, an optimization scheme for the cable layout of industrial robot was obtained, with the objective of minimizing the maximum stress on cable model. The research results provide a theoretical basis for improving the service lifespan of industrial robot cables.

Load-bearing capacity and stiffness are key performance indicators for measuring the load-bearing characteristics of hydrostatic guideways, directly affecting the machining accuracy and stability of precision grinding machines. In response to the unclear interaction mechanism of the structural parameters of the opposed oil pads in hydrostatic guideways and the limitation of existing studies focusing on single oil pad analysis, taking the granite hydrostatic guideway of a certain type of precision grinding machine as the research object, the load-bearing characteristic analysis and parameter optimization under the coupling effect of multiple parameters were systematically carried out. Firstly, based on the theory of fluid mechanics, a mathematical model of the load-bearing characteristics of the hydrostatic guideway was established, and analytical expressions for the load-bearing capacity and stiffness of the opposed oil pads were derived. Then, through single-factor analysis, the independent influence laws of oil supply pressure, oil cavity clearance, oil seal edge width and orifice throttler diameter on the load-bearing characteristics of the hydrostatic guideway were revealed. It was found that the oil supply pressure and oil cavity clearance had a significant impact on the load-bearing capacity and stiffness. Finally, 27 groups of experiments were designed using the BBD (Box-Behnken Design) method, and a second-order polynomial regression model was constructed to analyze the interaction mechanism of multiple parameters. Meanwhile, the multi-objective optimization was carried out based on the response surface method, and the optimal solution set of the design parameters was obtained. The results showed that the load-bearing capacity and stiffness of the optimized hydrostatic guideway were improved by 24.99% and 19.62%, respectively. The research results provide a theoretical reference for the enhancement of the load-bearing performance and parameter optimization of hydrostatic guideways in precision grinding machines.

The circular saw blade is the main component for stubble-cutting operation of Salix psammophila, but it suffers from problems such as low cutting efficiency and teeth prone to wear during operation. Therefore, a mechanical analysis was conducted on the sawing process of circular saw blades, and a new biomimetic circular saw blade was designed by extracting the contour characteristic curves of the bamboo rat incisors as the bionic prototype. Subsequently, a finite element model of the circular saw blade imitating bamboo rat incisors was established, and the explicit dynamics software LS-DYNA was employed to simulate the sawing process for analyzing its mechanical performance. Meanwhile, the parametric comparison was made with the ordinary circular saw blade with folded-back teeth. The simulation results showed that the average sawing force of the circular saw blade imitating bamboo rat incisors reduced by 19.17%, among which the tangential force and radial force decreased by 16.67% and 10.68%, respectively. It also exhibited smaller fluctuations in axial force with shorter impact duration and achieved an 18.99% reduction in sawing energy consumption. The sawing test results indicated that the circular saw blade imitating bamboo rat incisors delivered superior sawing performance while reducing pressure and energy consumption on the saw teeth during the cutting process. The newly designed biomimetic circular saw blade provides a novel solution to address the problems of high energy consumption and easy wear of circular saw blades in the mechanized stubble-cutting process for Salix psammophila.

In a high-temperature environment, the elasticity of wave spring will be attenuated due to the spring stress relaxation and material aging, which will affect the sealing effect and even cause the sealing device to fail to operate normally. For this reason, based on the test data of wave spring elasticity decay, a numerical analysis model of wave spring elasticity decay was established by using the creep model. The influence of temperature and initial elasticity on the wave spring elasticity decay was investigated, and a prediction method for the wave spring life was proposed based on the Arrhenius model. The research results showed that the elasticity loss rate of wave spring increased significantly with the increase of temperature. The larger the initial elasticity was, the higher the elasticity loss rate was, and the elasticity decay process was divided into two stages of sharp decrease and slow decrease. The established life prediction model could accurately predict the service life of wave spring. The research results provide a basis for the reliability design and life prediction of wave spring in engineering applications.

In order to achieve precise heat dissipation and component lightweighting for a 2 kW fiber laser, and to ensure its stable and reliable operation, effective thermal management for its pump source is necessary. A phase-change direct cooling plate was designed for a 2 kW fiber laser, using a method of compressor-driven and refrigerant phase-change direct cooling. The internal flow channel of the phase-change direct cooling plate was optimized, and the heat dissipation performance of the cooling plate was analyzed through CFD (computational fluid dynamics) numerical simulation and experimental test. it was determined that adopting the phase-change direct cooling plate with a single flow path and variable diameter of flow channel could maintain the working temperature of (26±0.5) ℃ at the pump source simulation heat source under the maximum heating power of 2.8 kW, while meeting the heat transfer condition. The result indicated that the colding plate could meet the heat dissipation requirements for the stable and reliable operation of a 2 kW fiber laser. The research results provide theoretical support for the production of principle prototype of phase-change direct cooling system.