Multi-source uncertainties, such as random loads, manufacturing errors, and installation inaccuracies, influence mechanical system during the service processes, resulting in the deviation of system response, which seriously affects the operation stability and system reliability. In practical engineering, it is very difficult to collect high-quality data of complex mechanical systems on a large scale. For this reason, the sample size of the obtained data is usually small, and its uncertainty is difficult to quantify using probability models. Furthermore, when mechanical systems operate under certain specific conditions, the data may cluster in certain areas, exhibiting distinct clustering characteristics, which leads to challenges for the uncertainty analysis and measurement of mechanical system under these conditions. To address the above issues, an uncertainty analysis method for mechanical systems based on a multi-cluster ellipsoidal model was proposed to accurately quantify the uncertainties of system parameters with clustering characteristics, so as to achieve the rapid evaluation of system response uncertainty. In order to accurately quantify the small sample data with clustering characteristics, the multi-cluster ellipsoidal model was employed for uncertainty modeling. Based on the parameter interval information, the sensitivity analysis of the mechanical system was conducted to determine the main parameters that affected the performance of the mechanical system. The upper and lower boundaries of the mechanical system response were obtained by using multi-cluster ellipsoidal model and the sequential quadratic programming algorithm to achieve the uncertainty propagation of system parameters. The accuracy and effectiveness of the proposed method were verified through three numerical examples and one radar system engineering example. The research results indicate that the hyper-ellipsoidal clustering method has high computational efficiency and accuracy when addressing the uncertainty of mechanical system performance under limited samples.

In order to achieve the unsupported construction of 3D printed concrete spherical shell structures, a structure splitting method based on self-supporting critical angle is proposed. In this method, the structure splitting problem was converted into a single-objective optimization problem, and the relatively simple and feasible spherical shell structure splitting scheme was obtained by the improved genetic algorithm and dynamically optimized splitting strategy. The spherical shell structure could be split into multiple self-supporting printable units based on the obtained splitting scheme, and the whole structure could be assembled after the splitting units were printed one by one. For the concrete spherical shell structure, the number of splitting units increased with the increase of material self-supporting critical angle. To minimize the adverse effects of the number of splitting units on the subsequent connection and overall performance of the spherical shell structure, the self-supporting critical angle of the concrete material should be limited. The results of field forming experiments show that the proposed method can effectively split the 3D printed concrete spherical shell structure and avoid structural formwork during the printing process, thereby enhancing construction efficiency.

Aiming at the difficulty of wind-generator set blade inspection and the poor effect of traditional robot inspection, a wind-generator set blade inspection robot based on legged-and-tracked movement and hybrid adsorption was designed. Firstly, the mechanical characteristics of the robot moving on the blade surface were modeled, the required adsorption forces were calculated under the conditions of slip-free and overturning-free motion, and the equipment components were selected according to the calculation results. Secondly, according to the robot's structural characteristics, the corresponding control system was designed, and its moving gaits on the blade surface were planned and analyzed. Finally, the experiments were conducted to verify the effectiveness of the robot design scheme. The experimental results demonstrated that the robot had flexible moving ability and good adsorption performance, which could meet the actual demand of blade inspection. The research results not only promote the practical application of the robot in wind-generator set blade inspection, but also provide a reference for the progress and popularization of automatic inspection technology in related fields.

Aiming at the problem that traditional wall-climbing robots cannot adapt to the variable curvature wall of wind power towers, taking the fast stability and turning flexibility of the wheeled mobile mechanism as the starting point, the attitude change of the wheeled mobile mechanism moving on the variable curvature wall was analyzed, and on this basis, a new wall-climbing robot adopting split wheeled movement and gap permanent magnetic adsorption technology was designed. Firstly, a multi-state motion model for the wall-climbing robot was established, and the adaptive motion characteristics of the robot moving on the variable curvature wall by using the attitude adjustment of its own split structure were analyzed. Then, the magnetic adsorption module of the wall-climbing robot was optimized, and the optimal structural parameters under high adsorption efficiency were obtained through parametric analysis. The experiment results showed that the structural design of the new wall-climbing robot was reasonable, and it could realize the adaptive and reliable motion on the variable curvature wall. The designed wall-climbing robot can provide an efficient and safe solution for the maintenance of wind power towers, which has important engineering application value.

The soft wall-climbing robot with flexible materials as the main body can change its shape through passive deformation or active deformation to adapt to the complex wall environment. However, due to the low stiffness and lag of flexible materials, the existing soft wall-climbing robots generally suffer from insufficient driving force and poor motion stability, which seriously restricts their practical applications. Aiming at this problem, a flexible pneumatic wall-climbing robot based on the Kresling origami structure was designed. This robot composed of anchoring modules and telescopic modules. The anchoring module achieved anchoring on the wall by the adsorption effect of suction cups under negative pressure. The telescopic module adopted a soft continuum structure with Kresling origami structure and plastic film cover as the main body, achieving extension and contraction. The experimental results indicated that the designed robot could achieve stable crawling at a speed of 25-28 mm/s on the smooth wall with a slope of 0°-90°, and had good adaptability to walls of different materials. The results show that the pneumatic wall-climbing robot based on the Kresling origami structure can not only crawl bidirectionally on walls of different slopes and materials, but also flexibly turn on walls based on the flexibility of the telescopic module, which can provide new ideas for the design and optimization of soft wall-climbing robots.

Spatial parallel multi-stable mechanism (SPMM) is a mechanism that can switch to different stable equilibrium states under external forces. It is a combination of traditional spatial rigid parallel mechanisms and compliant mechanisms, which is more stable and can save energy. The 6-DOF 3-PSPS SPMM with eight kinds of steady-state configurations was innovatively designed by using the rigid body substitution method. By moving three branches, eight kinds of steady-state configurations of the mechanism could be switched. Firstly, the SPMM structure was analyzed, the mechanism statics analysis was carried out, the energy-kinematic differential equation was established to determine the steady-state of the mechanism, and the energy diagram of the mechanism's motion process was obtained by MATLAB software. Secondly, using the energy method based on Lagrange-Dirichlet principle, eight steady-state configurations of the mechanism were determined, and the switching paths between the steady-state configurations were analyzed. Finally, the 3D printed SPMM model was used for experimental verification. The SPMM can realize steady-state configuration control and can be widely used in the design of motion platform and buffer mechanism.

In order to solve the problems of small displacement magnification, low output stiffness and excessive motion coupling displacement of flexible precision positioning platform, a two-dimensional precision positioning platform based on piezoelectric ceramic drive is proposed. Firstly, the statics modeling for the precision positioning platform was carried out by using the module method, elastic beam theory and flexibility matrix method, and the dynamics modeling was conducted by using the Lagrange equation. Then, the finite element simulation on the displacement magnification, output stiffness, coupling displacement and natural frequency of the precision positioning platform was carried out by ANSYS Workbench software. Finally, the performance parameters of the precision positioning platform were tested by constructing an experimental device, and comparative analyses were conducted with finite element simulation results and theoretical calculation results. The simulation and experimental results verified the accuracy of the statics model and dynamics model of the precision positioning platform, which showed that the designed precision positioning platform had advantages of large displacement magnification, high output stiffness and strong decoupling performance. The research results provide some theoretical guidance for the flexible precision positioning platform to realize large stroke displacement output and excellent decoupling capability.

In order to improve the machining accuracy of machine tools, the target of guide rail error is determined during the machine tool design stage, and the mapping relationship between guide rail errors and workpiece errors was studied. Firstly, based on Hertz contact theory, the coordination relationship between rolling element deformation and load was constructed, as well as the static equilibrium equation of the guide rail pair considering the structural stiffness of the slider. On this basis, the potential energy function for the guide rail pair was constructed. The equivalent stiffness model of the guide rail pair was established through the potential energy decomposition, and the finite element simulation verification was carried out. Then, based on the finite element model of the slider fastener, a stiffness matrix of the slider fastener facing the slider position nodes was constructed. Based on the principle of minimum potential energy and combined with the equivalent stiffness model of the guide rail pair, the error mapping relationship between the guide rail and the motion pair in the multi-slider system considering the structural stiffness of the slider fastener was established, and the finite element simulation verification was also carried out. Next, based on the multi-body system theory, a geometric error transfer model for machine tools was established to obtain the tool pose error. Finally, by employing the principle of geometric kinematics, a prediction model for workpiece machining errors was established by performing Boolean operations on the three-dimensional discrete points of the workpiece and the geometric boundaries of the tool, thereby establishing a mapping model between guide rail errors and workpiece errors. Taking a certain type of machine tool as an example, the influence of guide rail error and turntable error on workpiece error was compared and analyzed, which verified the feasibility of the proposed method. The research results can provide theoretical guidance for the precision design of machine tools.

In order to analyze the root of shearer rocker arm shell failure and ensure the safe and stable operation of shearer, the influencing factors of shearer rocker arm shell deformation were analyzed, and the shell deformation law was studied.Firstly, the mechanical model of the rocker arm shell was constructed, and the load factors affecting the deformation of rocker arm shell were sorted out, including the external forces generated by coal rock on the drum and the internal loads formed by gear transmission system when the shearer was cutting. Secondly, Solidworks software was used to establish the three-dimensional model of the rocker arm, and EDEM-ADAMS software was used to build the elevation working condition model of shearer cutting 4 types of gangue coal rocks, containing aluminous rock, gray rock, limestone and siltstone, to simulate the deformation of the rocker arm shell. Finally, the shell deformation test platform was set up, and the experiment of shearer cutting silt-containing gangue coal was carried out. The simulation results showed that the mean value of drag traction resistance was less than the mean value of cutting resistance, and both were greater than the mean value of lateral force. After the shell was subjected to external loads, its deformation was complex, at the joint of the rocker arm shell and the drum planetary reducer, the deformation was large, and the risk of instability was large. The deformation of rocker arm shell at the position of gear shaft exhibited a nonlinear, approximate normal distribution with multiple peaks. The experimental results showed that the closer to the drum planetary reducer, the greater the deformation, which was highly consistent with the simulation results. The research clearly shows the deformation law of the rocker arm shell under complex loads providing a robust theoretical support for the improved design of the rocker arm shell, and is helpful to optimize the shearer design scheme, reduce the shell failure risk, and effectively improve the reliability and stability of the shearer in actual production.

Esophageal stenosis is one of the main symptoms of esophageal cancer. Currently, the drug-carrying esophageal stents are widely used in the clinical treatment of esophageal stenosis. At present, the main preparation methods of drug-carrying esophageal stents are dip coating method and spray coating method, but the materials of the drug-carrying layer of esophageal stent prepared by these methods were limited and the coating accuracy is not high. To solve the above problems, a method for preparing the drug-carrying layer of esophageal stent based on piezoelectric inkjet printing technology is proposed. Firstly, the finite element simulation method was used to design the temperature control box for the piezoelectric inkjet printing platform and optimize the temperature control parameters, so as to promote the solidification of printing materials and broaden the materials used in the drug-carrying layer. Then, the influence of voltage amplitude, slope parameter and pulse width of the driving waveform for piezoelectric inkjet heads on the droplet diameter was deeply explored, and the driving waveform parameters were optimized to improve the coating accuracy of drug-carrying layer. Finally, the printing experiment for drug-carrying layer was conducted to verify the accuracy and effectiveness of the simulation design of temperature control box and the optimization of driving waveform parameters. The results showed that the GelMA (gelatin methacryloyl) hydrogel had a good forming effect at -4 to 4 ℃. The droplet diameter was positively correlated with the voltage amplitude and slope parameters of the driving waveform, but there was an optimal pulse width. Under the premise of ensuring printing accuracy, the rising edge voltage amplitude was determined to be 30 V, the rising edge slope and the falling edge slope were both 7 V/ms, and the pulse width was 1.5 ms. Using this driving waveform, a uniform drug-carrying layer of esophageal stent with good curing and forming effect and high accuracy was successfully printed, which could provide a new idea for the preparation of drug-carrying esophageal stents.

hydrodynamic rotary spray dust reduction device has the advantages of only hydrodynamic drive and good atomization effect, and has been widely used in coal mine underground working face. In order to realize safe, accurate and efficient dust reduction, its performance was analyzed systematically based on dynamic grid technology. The 3D model of the dust reduction device was established by DesignModeler software, and the influence rules of the water axis outlet angle on the outlet speed of water flow and the rotational speed of water axis were analyzed by using the dynamic grid technology. The programming technique of UDF (user-defined function) and the VOF (volume of fluid method) model were used to analyze the variation rules of the axial velocity of fog particles at the mixing outlet and the axial velocity of wind flow in the wind flow inlet with the water axis outlet angle. The results showed that with the increase of water axis outlet angle, the maximum outlet velocity of water flow decreased from 63.19 m/s to 24.97 m/s, and the rotation speed of water axis gradually increased to 1 786.4 r/min; the maximum axial velocity of fog particles at mixing outlet decreased from 39.178 m/s to 10.637 m/s, then to 12.854 m/s, and finally to 8.014 m/s, the velocity uniformity increased firstly and then decreased; the maximum axial velocity of wind flow firstly increased from 0.804 m/s to 1.524 m/s and then decreased to 1.272 m/s, and the velocity uniformity was unchanged firstly and then decreased. When the water axis outlet angle was 45°, the atomization performance of the dust reduction device was the best. The test platform of water axis rotation speed and wind flow axial speed was set up, the correctness of simulation results was verified by experiments. The dust reduction device was applied in the field. The results showed that the reduction rates of total dust and respirable dust in the feed port area of the transfer machine were significantly increased after the adoption of the hydrodynamic rotary spray dust reduction device, both of which reached more than 75%, and the mass concentration of respirable dust in the working place was reduced to 6.31 mg/m³. The research results provide a new idea for creating a safe, healthy and green coal mine production environment.

The notch shapes of existing flexure hinges are primarily limited to conic sections and their combinations, which tend to fail due to excessive stress under complex loads and large angular movements. Therefore, a novel nested cosine function type multi-axis flexure hinge is designed. Firstly, based on the finite beam compliance matrix modeling (FBMM) method, the compliance and precision models of the novel flexure hinge were established. Compared with the finite element simulation results of ANSYS Workbench software, the relative errors of compliance and precision were less than 4.89% and 4.97% respectively, which verified the validity of theoretical models. Then, the effects of structural parameters on the compliance, precision and compliance-precision ratio of the novel flexure hinge were discussed, and compared with elliptic type, arc type and sinusoidal type multi-axis flexure hinges. The results indicated that the designed flexure hinge had the characteristics of high flexibility and low stress. Finally, an experimental platform for flexure hinge was built to test the deformation. The relative error between the measured results and the theoretical results was less than 8%, which further verified the validity of the compliance model. The nested cosine function type multi-axis flexure hinge can provide reference for the design of large-stroke compliant precision positioning stages.

To address the issues of low mechanical drilling speed, severe wear, and high drilling costs of PDC (polycrystalline diamond compact) bits in the hard sandstone strata of the Shaximiao Formation in eastern Sichuan, a comprehensive study was conducted on the rock-breaking performance of special-shaped PDC cutters in the Shaximiao Formation hard sandstone strata. Aiming at the high abrasiveness and hard-plastic characteristics of the sandstone strata in Shaximiao Formation, four types of special-shaped PDC cutters were designed, including axe-shaped cutter, circular-arc curved-surface cutter, axe-shaped curved-surface cutter, and inclined axe-shaped cutter, and a comprehensive rock-breaking specific energy evaluation method combining PDC cutter breaking rock by cutting and pressing was established. Then, using the rock-breaking simulation model, the optimization design for structural parameters of these special-shaped PDC cutters was conducted, and the rock-breaking performance of the optimized PDC cutters was simulated and analyzed. The results showed that the axe-shaped cutter with a blade angle of 130° and the circular-arc curved-surface cutter with a arc radius of 25 mm had the lowest comprehensive rock-breaking specific energy. The final determined arc radius and blade angle of the axe-shaped curved-surface cutter was 25 mm and 130°, and the blade angle and inclination angle of the inclined axe-shaped cutter was 130° and 70°. Four types of special-shaped PDC cutters exhibited significantly lower comprehensive rock-breaking specific energy and blade temperature compared to conventional PDC cutters, with a clear positive correlation between comprehensive rock-breaking specific energy and wear height. The laboratory rock-breaking test results indicated that the axe-shaped cutter and the axe-shaped curved-surface cutter had superior rock-breaking performance. The research results provide a theoretical foundation for the customized design of PDC bits tailored for the hard sandstone strata of the Shaximiao Formation.

The sheer wave vibroseis vibrator baseplate is a key component in shale gas exploration, and its fatigue life directly affects the service life of vibroseis and the exploration accuracy. However, traditional optimization methods for vibrator baseplate fatigue life ignore the welding residual stress between the baseplate and the baseplate teeth, resulting in poor performance in anti-fatigue optimization design for the baseplate structure. Therefore, the local sensitivity method was used to conduct a sensitivity analysis for the fatigue life of the baseplate, and the welding residual stress was determined as the key factor affecting the fatigue life. Subsequently, mathematical models between the maximum welding residual stresses in all directions of the baseplate and the welding speed and interlayer temperature were established. Meanwhile, with the maximum welding residual stresses in all directions as the constraints and the fatigue life as the optimization target, the corresponding optimization model was constructed. Finally, the NSGA-Ⅱ (non-dominated sorting genetic algorithm-Ⅱ) was used to obtain the Pareto solution set, and the best optimization scheme was determined by combining the entropy weight method and the TOPSIS (technique for order preference by similarity to ideal solution): the welding speed was 10.23 mm/s and the welding interlayer temperature was 105 ℃. The results showed that the fatigue life of the optimized baseplate was 10.23 years, which was 17.72% higher than that before optimization. The research results can provide scientific and effective theoretical methods and engineering guidance for the fatigue life optimization of the sheer wave vibroseis vibrator baseplate.