A stepped-frequency radar transmission and reception system based on RF direct sampling technology was designed to address the issues of slow switching speed of sub pulses and incoherent phase of transmission and reception signals in stepped-frequency radar. This system performs RF direct acquisition of C-band radar signals, and all signal processing processes were carried out in the digital domain. It also had high integration and low power consumption. It was generated stepped-frequency signals by fast frequency hopping, frequency sweep of 1.8 GHz bandwidth within 7 ms was gotten. The system operates in the frequency range of 200~2 000 MHz with a frequency step of 2 MHz. At the same time, the parameters of the stepped-frequency signal in this system can be changed according to detection requirements. The test results show that the stepped-frequency radar system can achieve one-dimensional ranging function.

To solve the path planning problem of mobile robots in complex orchard environments such as irregular and rugged terrain in hilly and mountainous areas, an improved grey wolf algorithm based 3D path planning method for mobile robots was proposed. By simulating the actual geographical environment, a three-dimensional orchard terrain and obstacle model was established, and a path planning objective function model was structed. By introducing the sparrow search algorithm (SSA) the initialization method, convergence factor, local search ability, and global search ability of the standard grey wolf optimization (GWO) were improved. The simulation experimental results show that the proposed algorithm has the advantages of fast optimization speed, optimal path planning distance, and fast convergence speed compared to other algorithms, indicating the effectiveness and superiority of the proposed method.

In response to the tasks of detection and maintenance in small-diameter pipeline transportation, a small-scale soft pneumatic pipeline crawling robot was designed and developed. The robot employed the technique of analytical implicit triply periodic minimal surface offset to form a solid structure with thickness, and achieved the anisotropy of structural stiffness by adjusting the parameters of implicit equations. Based on this, the radial and linear actuators were designed to meet the flexible motion requirements of the robot inside the pipeline. To optimize the performance of the robot, a joint parameter optimization framework based on MATLAB, Rhino, and ABAQUS was proposed, and an automated parameter optimization process was implemented using Python scripts. Through this framework, the motion performance and adaptability of the robot could be effectively improved. Based on two types of deformation actuators, the overall structure of the pipeline crawling robot was designed, and the manufacturing method and motion control gait were elaborated in detail. Experimental results show that the designed pipeline robot can stably move along the pipeline in two different postures and under certain load conditions, verifying the feasibility of the joint parameter optimization framework. The research results provide valuable references for the parameterized design and optimization research of subsequent pipeline crawling robots, which contributes to the application development of soft robots in the field of small-diameter pipeline detection and maintenance.

The sigmoid iteration ACO(ant colony algorithm) was optimized for the problems of poor environmental adaptability, high number of inflection points and high computational complexity that exist in the traditional ACO(ant colony algorithm)in route planning. Firstly, the Sigmoid activation function distribution strategy was adopted to improve the initial pheromone spread through the position of the mesh nodes, and the initial concentration of the pheromone was assigned by the sigmoid, which reduced the blindness of the algorithm’s pre-search. Secondly, the adaptive factor was introduced to dynamically regulate the heuristic function, which increased the degree of expectation of the ants in choosing the globally optimal node, and reduces the convergence time of the algorithm. Lastly, a statistical analysis was carried out in each generation of the ant, and the three characteristic parameters of ant path optimal, worst and average were extracted in each generation, and the pheromone updating function was dynamically adjusted according to the number of iterations to give full play to the parallelism characteristics of the algorithm. The results prove that the improved algorithm shortens the optimal path length by 2.7%, 3.2%, and 5.4%, reduces the average number of iterations by 42%, 53%, and 62%, and shortens the worst path length by 49%, 62%, and 73%, respectively, when compared with the ant colony system, the elite ranking algorithm, and the traditional ACO. The study prove that the optimized algorithm has stronger global optimality seeking ability and better application value.

To enhance the synchronization performance of multiple clocks in robotic communication systems, a study was conducted on a distributed clock synchronization compensation scheme. Quantitative compensation and dynamic compensation algorithms for clock errors were designed. The synchronization compensation scheme, based on the IgH EtherCAT communication protocol stack, was implemented, and trajectory tracking and communication performance tests were conducted on a six-axis robotic arm. The results show that the application of this synchronization scheme improves the circular trajectory precision of the robotic arm’s end effector compared to non-IgH synchronization schemes. The clock synchronization error is reduced to 54 ns, with the error tolerance within ±200 ns. It is evident that the compensation scheme enhances clock synchronization performance and meets the application requirements of the robotic arm.

The background difference method and cross-correlation method used in the extraction of the bullet position in the images collected by the traditional CCD(charge coupled device) intersection stand-up target have the problems of poor versatility and long time-consuming. By analyzing the problems existing in CCD precision target image projectile extraction, a method for CCD precision target image projectile extraction based on IGWO(improved grey wolf optimizer) algorithm was proposed. The DLH (dimensional learning-based hunting) search strategy was used to update the position of each search factor through the neighborhood. Generate candid ate solutions, increase the diversity of search populations, and jump out of local optimal solutions. The bullet extraction problem was transformed into the problem of finding the minimum connected region of gray value under certain constraints. The minimization area gray value model, the vertical light spot area and the low gray area elimination model were established. Under the same parameter setting, the IGWO, GWO(grey wolf optimizer), MFO(moth-flame optimization) algorithm, cross-correlation algorithm, and background difference method were used to conduct comparative experiments. The experimental results show that the target detection success rate of the IGWO algorithm is much higher than other algorithms, reaching 95%, and the algorithm solution time is much lower than other algorithms, shortening to 12 ms.

To study the wind pressure distribution characteristics of long-span roofs of airport terminals at different mountain heights in mountainous areas, a rigid model wind tunnel pressure measurement test of airport terminals roofs at mountain heights of 0 m, 30 m, 60 m, and 90 m was conducted to compare and analyze the effects of the heights on the surface mean and pulsating wind pressure, non-Gaussian characteristics of pulsating wind pressure, peak factor, and extreme wind pressure of the roof surface. The results show that the increase in mountain height significantly increases the mean and fluctuating wind pressure coefficient at the windward leading edge of the roof, and also intensifies the degree of flow separation at the leading edge of the roof. This causes the skewness, kurtosis, and probability density function of the fluctuating wind pressure at the windward leading edge of the roof to deviate significantly from the standard Gaussian distribution, exhibiting strong non-Gaussian characteristics. At the same time, the Hermite moment model was used to calculate the peak factor, and it was found that the peak factor of most measuring points on the roof surface was mainly distributed in the range of 3.5~4, which was much higher than the recommended value of 2.5 in GB 50009—2012. The extreme wind pressure value at the front edge of the roof also increased with the increase of the mountain height, and there was a similar variation pattern at the edge of the roof under all wind directions. Among them, the most unfavorable extreme negative pressure on the roof surface at a mountain height of 90m decreased by 44.9% compared to the 0m mountain height. Research can provide useful suggestions and references for the design and construction of terminals in similar airports.

The creep of wood under the action of long-term load will increase the deformation of wooden beams or wooden columns, and bring hidden safety risks to the building structure. In order to improve the creep performance of wood components, an aluminum wood composite columns (AWC) was designed to make AWC with 0,2%, 3%, 3% and 4% respectively. The creep test of 0.25 stress ratio of the lower column lasted 30 days. The creep strain-time curve and creep coefficient-time curve were obtained and the AWC creep pattern was analyzed. Burgers model was used to fit the creep strain-time curve to explore the influence of aluminum alloy content on AWC creep, and analyze the causes of AWC int creep inhibition from AWC material characteristics and load transfer. The results show that, compared with AWC 1 with aluminum alloy content of 0, the creep deformation of AWC 2 ~ AWC 4 decreases to different degrees, that is, aluminum alloy can effectively enhance the creep deformation ability of wood; The four AWC creep strain-time curve correlation coefficient based on burgers model are greater than 0.95, and the creep prediction model constructed by this model can predict the AWC creep.

In order to improve the problem of easy cracking in the negative moment zone of the composite beam, the UHPC(ultra-high performance concrete)-narrow steel box composite beam structure was proposed, and the shear load capacity calculation method of UHPC-narrow steel box composite beam was obtained based on the ultimate equilibrium method and the sub-stacking method. In order to verify the accuracy of the calculation method, one normal concrete narrow steel box composite beam and three UHPC-narrow steel box composite beam specimens were designed with the thickness of UHPC layer and steel fiber as variables, and the test beams were subjected to mid-span reverse loading test to obtain the shear resistance of the composite beam under negative bending moment. The test results show that compared with the normal concrete narrow steel box composite beam, when the UHPC material is used in the wing slab, the crack distribution in the wing slab was more regular, and with the increase of the thickness of the UHPC slab, the crack distribution gradually shows the characteristic of vertical equidistant distribution, and when the thickness of the wing slab was kept constant and the thickness of the UHPC layer was increased by 50 mm, the yield load increases by 12.5% and the ultimate load increases by 8.3%, and the deflection value corresponding to the ultimate load is reduced by 22%. By analyzing the yield deflection as well as the ultimate deflection of each specimen, it can be seen that the yield deflection tends to increase gradually with the increase of UHPC airfoil thickness, and the proportion of the elastic phase of the combined beam keeps increasing. The comparison of the test data with the theoretical calculation results shows that the calculation results obtained by the sub-stacking method can more effectively reflect the contribution of UHPC layer, ordinary concrete layer, steel box, reinforcement and filled part of concrete to the shear load capacity, and the results are more accurate.

To investigate the impact of polymer polyvinyl alcohol (PVA) and polypropylene fiber on the composite enhancement of loosely piled sandy soil in Southeast Xizang, unconfined compressive strength tests and direct shear tests were conducted. The the effects of the improved sandy soil was understood and the optimal mixing ratio of the improved materials was determined. Additionally, the change in the strength of the improved sandy soil under water erosion after dry and wet cycles was analyzed, and the reinforcement mechanism was investigated. The results demonstrate that the dosage of PVA and polypropylene fibers has a significant effect on the unconfined compressive strength. The best improvement effect is achieved with a dosage ratio of 12% PVA + 0.25% polypropylene fibers, resulting in an unconfined compressive strength of 1 716 kPa. This is 67 times higher than that of sandy soil with an unconfined compressive strength of 25.46 kPa. The shear strength of the improved specimens with different fiber contents increased with the increase of PVA doping. After 10 dry and wet cycling processes, the 12% PVA + 0.25% polypropylene fiber specimen exhibited an unconfined compressive strength of about 748.66 kPa, which was still 91.8% of the strength at 7 days and 1.47 times that of the same age maintenance period of 28 days. Polyvinyl alcohol solution formed a polymer film that adhered to and wrapped the sandy soil, while polypropylene fiber wound and filled the sandy soil. The combination of these two materials improved the stability of the sandy soil, effectively enhancing the bonding strength between soil particles and increasing the compressive strength of the soil body.