The efficiency of the rapidly exploring random tree (RRT) falls short when efficiently guiding targets through constricted-passage environments, presenting issues such as sluggish convergence speed and elevated path costs. To overcome these algorithmic limitations, we propose a narrow-channel path-finding algorithm (named NCB-RRT) based on Bi-RRT with the addition of our proposed research failure rate threshold (RFRT) concept. Firstly, a three-stage search strategy is employed to generate sampling points guided by real-time sampling failure rates. By means of the balance strategy, two randomly growing trees are established to perform searching, which improves the success rate of the algorithm in narrow channel environments, accelerating the convergence speed and reducing the number of iterations required. Secondly, the parent node re-selection and path pruning strategy are integrated. This shortens the path length and greatly reduces the number of redundant nodes and inflection points. Finally, the path is optimized by utilizing segmented quadratic Bezier curves to achieve a smooth trajectory. This research shows that the NCB-RRT algorithm is better able to adapt to the complex narrow channel environment, and the performance is also greatly improved in terms of the path length and the number of inflection points. Compared with the RRT, RRT* and Bi-RRT algorithms, the success rate is increased by 2400%, 1900% and 11.11%, respectively.

Based on the lightweight characteristics of automotive energy absorption boxes and the requirement of good energy absorption effect, this article first applies the node-enhanced body centered cubic (NBCC) lattice structure to the inner core design of automotive energy absorption boxes. The gradient study of the NBCC lattice structure was carried out using a drop hammer impact and split Hopkinson pressure bar (SHPB). The results indicate that gradient lattice structures have advantages in energy absorption, but there are differences under different gradient strategies. When the impact is not sufficient to compact the structure, the vertical rod diameter gradient node-enhanced lattice structure (RGNBCC) can absorb more energy and improve energy absorption performance by 25%. The vertical height gradient node-enhanced lattice structure (HGNBCC) is more suitable for high-speed impact conditions. Based on the advantages of the RGNBCC in resisting low-speed impacts, it is applied to the inner core design of automotive energy absorption boxes and optimized using multi-objective optimization methods. The optimization results show that the maximum peak impact force is reduced by 45.6% and the specific energy absorption is increased by 30.4%.

With the in-depth development of intelligent manufacturing worldwide, flexible production modes and corresponding production lines for personalized, customized, small-batch, and multi-variety products have become the dominant force in today’s manufacturing industry. To address the challenges of real-time information interaction and visualization monitoring in the flexible production lines (FPLs), this paper conducts in-depth research on the 3D visualization simulation of FPLs based on digital twin (DT) according to the characteristics of FPLs and the demand for intelligent development. Firstly, a five-layer DT framework for 3D visualization monitoring of FPLs is proposed, which is divided into the physical entity layer, twin model layer, twin data layer, application service layer, and connection transport layer. The corresponding DT models of the twin model layer are then organized at the atomic, unit, and system levels and described from four dimensions: geometric physical, attribute information, behavioral logic, and constraint rules. On this basis, the data interconnection mechanism, real-time data-driven twin model mapping, and twin data management methods of the above DT framework are further studied. Finally, a representative machining FPL for mechanical processing is selected as a case study, a virtual simulation system of FPLs for 3D visualization monitoring based on DT is developed and implemented. Through the implementation and application in the field operation, the effectiveness and feasibility of the proposed method and developed system are verified.