基于扫描法在线构造拓扑图的路经规划算法

该文提出了一种基于扫描法在线构造环境拓扑图的路径规划算法。与传统路图法相比,该算法利用扫描的方法搜索障碍物切点,并构造环境拓扑图,降低了计算复杂度,提高了实用性;利用启发式函数选择适当的离开点进行扩展,并逐步完善拓扑图,避免了一次性构造整个环境拓扑图所带来的不必要的大计算量。通过“沿直线行走”和“绕障碍物行走”这两种行为模式的切换,保证机器人顺利地避开障碍物到达目标位置。该算法的计算复杂度低,易于在线实现,并在仿真中得到了验证。     

基于局部协调设计的复杂自由曲面模型拓扑还原技术

针对局部协调设计因引入协调曲面而破坏了模型原有的拓扑结构并同时增加了自由曲面形状造型所需的曲面片数量,提出一种基于局部协调设计的复杂裁剪汇交曲面模型拓扑还原技术。逆向定位汇交点(N面角点)并完整构造出决定还原后N边汇交曲面模型拓扑、几何形状和边界的特征曲线网格。应用自由曲面逼近技术分片逼近经裁剪汇交曲面和协调曲面离散获得的点云数据重建B样条曲面以实现裁剪汇交曲面的拓扑还原。采用自由曲面模型的全局美化技术实现紧公差约束下对点云逼近的N张拓扑还原后汇交曲面的全局美化,保证曲面相邻边界和N面角点处收敛的G1光滑拼接。应用实例表明,该拓扑还原技术不仅较好复现了原始汇交曲面模型的拓扑与几何性质,并且使模型达到整体G1连续。     

基于人工制造约束的三维拓扑优化设计方法

为了更好地解决三维拓扑优化工程实用化的问题,提出了基于人工制造约束的拓扑优化设计方法。该方法在拓扑优化过程中实时地监控拓扑优化结果,并借助设计人员的工程经验,实时地加入符合制造工艺成型的约束条件辅助计算进行机拓扑优化设计。钢结构拱桥算例中以有限元软件ANSYS为平台进行二次开发、以双向渐进结构优化法为核心算法通过人为干预实现了在拓扑优化过程中钢结构拱桥斜支撑向竖直支撑的转变。通过对比发现该方法的优化结果与实际拱桥模型结构相似,表明了该方法是有效的和可行的。     

Scheduling distributed flowshops with flexible assembly and set-up time to minimise makespan

The scheduling problems under distributed production or flexible assembly settings have achieved increasing attention in recent years. This paper considers scheduling the integration of these two environments and proposes an original distributed flowshop scheduling problem with flexible assembly and set-up time. Distributed production stage is deployed several homogeneous flowshop factories that process the jobs to be assembled into final products in the flexible assembly stage. The objective is to find a schedule, including a production subschedule for jobs and an assembly subschedule for products, to minimise the makespan. Such a scheduling problem involves four successive decisions: assigning jobs to production factories, sequencing jobs at every factory, designating an assembly machine for each product and sequencing products on each assembly machine. The computational model is first established, and then a constructive heuristic (TPHS) and two hybrid metaheuristics (HVNS and HPSO) are proposed. Numerical experiments have been carried out and results validate the algorithmic feasibility and effectiveness. TPHS can obtain reasonable solutions in a shorter time, while metaheuristics can report better solutions using more yet acceptable time. HPSO is statistically comparable yet less robust compared with HVNS for small-scale instances. For the large-scale case, HPSO outperforms HVNS on both effectiveness and robustness.     

POD-assisted strategies for structural topology optimization

We propose a new numerical tool for structural optimization design. To cut down the computational burden typical of the Solid Isotropic Material with Penalization (SIMP) method, we apply Proper Orthogonal Decomposition on SIMP snapshots computed on a fixed grid to construct a rough structure (predictor) which becomes the input of a SIMP procedure performed on an anisotropic adapted mesh (corrector). The benefit of the proposed design tool is to deliver smooth and sharp layouts which require a contained computational effort before moving to the 3D printing production phase.     

Active–reactive power approaches for optimal placement of charge stations in power systems

Electric Vehicles (EVs) have been suggested as alternatives to conventional vehicles for reducing petrol consumption and carbon dioxide (CO₂) emissions. When a large number of EVs connect to the grid, they can cause a large amount of power loss. Where to install multiple charge stations in the grid, so as to mitigate losses caused by EVs when providing energy to those EVs, is becoming vitally important. In this paper, a distribution test-network model is described. A new analytical method is proposed, using the stations’ cooperation in terms of optimal active and reactive power dispatch as well as power flow analysis for locating the optimal placement of charge stations, so as to reduce power losses. This method is compared with the previously developed current density method for single charge stations using system simulation results. It was demonstrated that the methods proposed in this paper are more accurate than the current density method, and that 17% of the average active power loss can be saved for three different types of load profile. In addition, 27% of the average active power loss was saved by installing two charge stations rather than no charge stations in the test-line. It is shown that this could represent a 2.6% annual yield above inflation for investing in installing and running such charge stations.     

Multi-Cohort Intelligence algorithm: an intra- and inter-group learning behaviour based socio-inspired optimisation methodology

ABSTRACT

A Multi-Cohort Intelligence (Multi-CI) metaheuristic algorithm in emerging socio-inspired optimisation domain is proposed. The algorithm implements intra-group and inter-group learning mechanisms. It focusses on the interaction amongst different cohorts. The performance of the algorithm is validated by solving 75 unconstrained test problems with dimensions up to 30. The solutions were comparing with several recent algorithms such as Particle Swarm Optimisation (PSO), Covariance Matrix Adaptation Evolution Strategy, Artificial Bee Colony, Self-Adaptive Differential Evolution Algorithm, Comprehensive Learning Particle Swarm Optimisation, Backtracking Search Optimisation Algorithm, and Ideology Algorithm. The Wilcoxon signed-rank test was carried out for the statistical analysis and verification of the performance. The proposed Multi-CI outperformed these algorithms in terms of the solution quality including objective function value and computational cost, i.e. computational time and functional evaluations. The prominent feature of the Multi-CI algorithm along with the limitations is discussed as well. In addition, an illustrative example is also solved and every detail is provided.     

Efficiency optimisation of the thermal energy storage unit in the form of the ceiling panel for summer conditions

The thermal energy storage unit in the form of the ceiling panel made of the gypsum‐microencapsulated phase change material composite with internal U‐shaped channels was optimised applying previously developed 1D‐3D numerical simulator. Calculations were carried out for variable inlet velocities of air, different properties of the composite expressed by enthalpy‐temperature curves, and summer climatic conditions in Central Poland (Warsaw). Optimal working temperature ranges of the composite were determined. Moreover, studies showed that for Central Poland, composites with wide ranges of the working temperature are preferred due to significant daily variations of ambient temperature during the whole summer.     

Grey filter functions for suppression of grey-scale elements

To solve the problem of the presence of grey-scale material in optimization results and improve convergence efficiency during the optimization procedure caused by those intermediate densities, three kinds of simpler filter functions were proposed for the variable density method according to S-curve models. First, the feasible range for the parameters of the filter functions was determined by studying Messerschmitt–Bölkow–Blohm beam with the solid isotropic micro-structure with the penalization (SIMP) method. Then, the filter functions were applied to three classic examples to verify their validity and feasibility. The results showed that higher convergence efficiency, clearer structure boundaries, and better feasible solutions were obtained compared with that without the filter function. Finally, the filter functions were also compared with one existing method to demonstrate its effectiveness and validity.     

Topology optimization for crashworthiness of thin-walled structures under axial crash considering nonlinear plastic buckling and locations of plastic hinges

Although topology optimization is established for linear static problems, more effort is required for solving nonlinear plastic problems. A new topology optimization approach with equivalent static loads (ESLs) is suggested to find the optimum topologies and locations of plastic hinges of thin-walled crash boxes by considering crash-induced deformation, the main crash energy-absorbing mechanism. Together with finite element method crashworthiness analyses, considering all nonlinearities with rate-dependent plasticity, the method was developed using an appropriate time-incremental scheme of ESLs without removing any high values of loads. Analyses show that the crash boxes with optimum topologies have energy-absorbing capabilities equivalent to the original structure. The proposed method is evaluated for two crashes: a crash box at low speed and a double cell subjected to high-speed collision. The results indicate that this method captures nonlinear crushing behaviours and accurate locations of plastic hinges where, if proper reinforcements are made, energy absorption can be enhanced.