A FAST assembly simulation analysis method for hull blocks with engineering constraints

In order to effectively improve the assembly efficiency for hull blocks, an assembly simulation analysis method considering engineering constraints is proposed in this paper, and an integrated system of shipbuilding accuracy analysis and assembly analysis considering multi-constraints is developed. The method is divided into pre-matching model and fine matching model. In the pre-matching model, an Improved Coherent Point Drift (ICPD) algorithm is used to obtain more accurate initial matching values. The fine matching model firstly uses the Analytic Hierarchy Process (AHP) algorithm to automatically obtain the constrained weights, then the weights vector is used to add the assembly constraints for hull blocks such as straightness, hard point constraints etc. into the multi-objective optimization function. By solving the function, the optimum positioning location and the most reasonable adjustment scheme are obtained. This method shortens the occupancy time of the equipment used to build the hull, reduces the workload of the staff, and improves the efficiency and quality of shipbuilding. The integrated system adds engineering constraints analysis module and the function of automatically finding and eliminating error measurement points. Through the verification of the examples, the integrated system realizes the automation and intellectualization of the assembly for hull blocks.

Integrated Optimization of Pipe Routing and Clamp Layout for Aeroengine Using Improved MOALO

Pipe routing and clamp layout for aeroengine are NP-hard computational problems and complex engineering design processes. Besides space constraints and engineering rules, there are assembly constraints between pipes and clamps, which usually lead to repeatedly modifications between pipe routing and clamp layout designs. In order to solve the problems of assembly constraints and design coupling between them, an integrated optimization method for pipe routing and clamp layout is proposed. To this end, the MOALO (multiobjective ant lion optimizer) algorithm is modified by introducing the levy flight strategy to improve the global search performance and convergence speed, and it is further used as a basic computation tool. The integrated optimization method takes pipe and clamp as a whole system and then solves the Pareto solution set of pipe-clamp layouts by using improved MOALO, where the pipe path, clamp position, and rotation angle are selected as decision variables and are further optimized. Inspired by engineering experience, a clamp-based pipe path mechanism considering regular nodes is established to deal with assembly constraint problem. The proposed method comprehensively considers engineering rules of pipe routing and clamp layout and realizes the overall layout optimization of pipe-clamp system while guaranteeing the assembly constraints between pipes and clamps. Finally, some numerical computations and routing examples are conducted to demonstrate the feasibility and effectiveness of the proposed method.

A Data-Driven Robust Scheduling Method Integrating Particle Swarm Optimization Algorithm with Kernel-Based Estimation

The assembly job shop scheduling problem (AJSSP) widely exists in the production process of many complex products. Robust scheduling methods aim to optimize the given criteria for improving the robustness of the schedule by organizing the assembly processes under uncertainty. In this work, the uncertainty of process setup time and processing time is considered, and a framework for the robust scheduling of AJSSP using data-driven methodologies is proposed. The framework consists of obtaining the distribution information of uncertain parameters based on historical data and using a particle swarm optimization (PSO) algorithm to optimize the production schedule. Firstly, the kernel density estimation method is used to estimate the probability density function of uncertain parameters. To control the robustness of the schedule, the concept of confidence level is introduced when determining the range of uncertain parameters. Secondly, an interval scheduling method constructed using interval theory and a customized discrete PSO algorithm are used to optimize the AJSSP with assembly constraints. Several computational experiments are introduced to illustrate the proposed method, and these were proven effective in improving the performance and robustness of the schedule.

Aircraft Pipe Geometric Feature Modeling and Error Compensation Based on Assembly Constraints

An error compensation method based on the assembly constraints of aircraft pipe is proposed for solving the problem of frequent failures caused by high assembly stress in the actual assembly process. Firstly, the pipe assembly process’ geometric modeling is carried out using geometric modeling method, and a new modeling method based on axis vector is proposed. On this basis, the Rodrigues formula was used to establish a pipe space pose calculation model based on actual assembly conditions. Then, the assembly constraints are analyzed, and the key constraint features are identified based on the pipe assembly requirements. Subsequently, the pipe assembly scenarios under different constraint forms are analyzed, and the pipe error compensation methods under a single constraint and associated constraint are respectively proposed. Finally, a typical flaring pipe is selected for the test; the pipe assembly error compensation calculation and the pipe installation air tightness test are carried out respectively. The results show that the proposed method could effectively realize the theoretical space pose adjustment and the pipe parameter compensation, and the air tightness of the compensated pipe is better than that of the uncompensated one.

An assembling algorithm for fixture in an assembly process planning system

Three-dimensional assembly process planning is a precondition for achieving full product lifecycle management based on three-dimensional modelling. Information expression and management operations of fixture models are key to three-dimensional assembly process planning systems. To reasonably and efficiently achieve the goal of planning assembly processes with a fixture model, the application of a fixture information model to a three-dimensional assembly process planning system is investigated. First, to manage tooling information, a fixture information model is defined that consists of management information, display information, geometric information, assembly constraints and degrees of freedom. Then, based on the analysis of the degrees of freedom of components and the assembly constraint relationship, a method of solving assembly constraints based on degrees of freedom reasoning is proposed. Finally, by using the method of solving assembly positioning based on geometric constraints, the pose transformation and assembly positioning of parts are achieved. Through the development of a tooling function module, the three-dimensional assembly process planning system is improved. The feasibility of the above method is verified using part of a spacecraft as an example.

Design and Development of Aeroderivative Gas Turbine Lifting and Handling Structures

Gas turbines Lifting devices (such as lifting lugs, eye bolts, trunnions, are provided on large stationary gas turbine parts as an aid in manufacturing, assembly, transport, shipping, test, installation, repair, and serviceability. Trunnions are used to lift the entire turbine including the base during assembly, transportation and installation Similarly, lugs are used to lift major components such as stator tube casings and subassemblies. In some circumstances there are geometric, fatigue, or assembly constraints that make the use of lugs problematic. In these circumstances, other approved lifting devices such as eye bolts, swivel hoist rings, and shackles may be used. Other devices may also be used for parts smaller than stator tube casings. This paper presents the design and development of the Aeroderivative gas turbine lifting and support lug features which are used for lifting, handling and transportation of the full gas turbine. It describes the challenges encountered during development of LPT lifting lugs to meet product requirements. The effects of full engine deformations due to support legs under worst case conditions of full engine handling are presented here. The benefits resulted due change in lug position are explained which is leveraged for the final production design. It also talks about the various design options considered to reduce stresses and simplify the lugs manufacturing.

Exchange of parametric assembly models based on neutral assembly constraints

It is difficult to exchange parametric assembly models using conventional neutral formats such as the standard for the exchange of product model data or the initial graphics exchange specification. These formats only support the boundary representation information that leads to the inability to perform parametric re-evaluation, once a model is exchanged. In order to exchange parametric information along with the design intent, a design history-based macro-parametric approach was proposed. Our method is macro-parametrics approach, however, supported only the exchange of individual part models. As most of the products are manufactured in assemblies, where several components are connected with multiple constraints, it is necessary to exchange the assembly model data. To overcome the issue of post-exchange editability, a collection of neutral assembly commands was introduced to extend the capabilities of the macro-parametric approach. A set of neutral assembly constraints was defined and a system for exchanging the parametric assembly models was implemented. An assembly model consisting of coaxial and incidence constraints was successfully exchanged between two commercial computer-aided design systems: CATIA and NX. It was possible to re-evaluate the assembly model parametrically after the exchange. The method can be further extended to exchange the remaining constraint types in different commercial computer-aided design systems.

Ste5 Membrane Localization Allows MAPK Pathway Signaling in trans Between Kinases on Separate Scaffold Molecules

SUMMARYThe MAP kinase cascade is a ubiquitous eukaryotic signaling module that can be controlled by a diverse group of scaffold proteins. In budding yeast, activation of the mating MAP kinase cascade involves regulated membrane recruitment of the archetypal scaffold protein Ste5. This event promotes activation of the first kinase, but it also enhances subsequent signal propagation through the remainder of the cascade. By studying this latter effect, we find that membrane recruitment promotes signaling in trans between kinases on separate Ste5 molecules. First, trans signaling requires all Ste5 domains that mediate membrane recruitment, including both protein-binding and membrane-binding domains. Second, artificial membrane tethering of Ste5 can drive trans signaling, bypassing the need for native localization domains. Third, trans signaling can occur even if the first kinase does not bind the scaffold but instead is localized independently to the plasma membrane. Moreover, the trans signaling reaction allowed us to separate Ste5 into distinct functional domains, and then achieve normal regulation of signal output by tethering one domain to the membrane and stimulating membrane recruitment of the other. Overall, the results support a heterogeneous “ensemble” model of signaling in which scaffolds need not organize multiprotein complexes but instead can serve as binding sinks that co-concentrate enzymes and substrates at specific subcellular locales. These properties relax assembly constraints for scaffold proteins, increase regulatory flexibility, and can facilitate both natural evolution and artificial design of new signaling proteins and pathways.