Search results

In the future, large space truss structures will be likely to require on-orbit assembly. One of the several proposed methods includes cooperative assembly performed by pressure-suited astronauts during extravehicular activity (EVA) and space robots. An intelligent planning method was presented to generate optimal assembly tasks.

Firstly, the inherent hierarchical nature of truss structures allows assembly sequences to be considered from strut level and structural volume element (SVE) level. Then, a serial assembly strategy in human-robot environment was applied. Furthermore, a two-level planning algorithm was presented. At the first-level planning, one ant colony algorithm for assembly sequence planning was improved to adopt assembly direction and time as heuristic information and did not consider assembly tasks. And, at the second-level planning, another novel colony algorithm for assembly task planning mainly considered results of the first-level planning, human-robot interactive information, serial assembly strategy and assembly task distributions.

The proposed two-level planning algorithm is very effective for solving the human and robot cooperative assembly of large space truss structures.

In this paper, the case study is based on the following assumptions: each tetrahedron is assembled by two astronauts; each pentahedron is assembled by three astronauts.

A case illustrates the results of the two-level planning. From this case study, because of geometrical symmetry nature of large space truss structures, the optimal assembly sequences are not only one.

The improved ant colony algorithm can deal with the assembly sequence and task planning in human-robot environment more effectively.

The implied assembly constraints of a computer-aided design (CAD) model (e.g. hierarchical constraints, geometric constraints and topological constraints) represent an important basis for product assembly sequence intelligent planning. Assembly prior knowledge contains factual assembly knowledge and experience assembly knowledge, which are important factors for assembly sequence intelligent planning. This paper aims to improve monotonous assembly sequence planning for a rigid product, intelligent planning of product assembly sequences based on spatio-temporal semantic knowledge is proposed.

A spatio-temporal semantic assembly information model is established. The internal data of the CAD model are accessed to extract spatio-temporal semantic assembly information. The knowledge system for assembly sequence intelligent planning is built using an ontology model. The assembly sequence for the sub-assembly and assembly is generated via attribute retrieval and rule reasoning of spatio-temporal semantic knowledge. The optimal assembly sequence is achieved via a fuzzy comprehensive evaluation.

The proposed spatio-temporal semantic information model and knowledge system can simultaneously express CAD model knowledge and prior knowledge for intelligent planning of product assembly sequences. Attribute retrieval and rule reasoning of spatio-temporal semantic knowledge can be used to generate product assembly sequences.

The assembly sequence intelligent planning example of linear motor highlights the validity of intelligent planning of product assembly sequences based on spatio-temporal semantic knowledge.

The spatio-temporal semantic information model and knowledge system are built to simultaneously express CAD model knowledge and assembly prior knowledge. The generation algorithm via attribute retrieval and rule reasoning of spatio-temporal semantic knowledge is given for intelligent planning of product assembly sequences in this paper. The proposed method is efficient because of the small search space.

Presents an integrated approach to assembly planning for manufacturing printed circuit boards (PCBs). The integrated manufacturing assembly planning system (IMAPS) is a system that incorporates knowledge‐based techniques to assist process engineers with the development of assembly plans for building PCBs. IMAPS has been developed in a two‐year project with a multinational telecommunications manufacturer and the Alberta Research Council of Canada. The scope of IMAPS is to develop an integrated environment that takes full advantage of electronic information for assembly planning of PCBs. Several functions in the company can be integrated with IMAPS, including product design, detailed assembly planning, line balancing and generation of shop floor drawings. Information stored in the manufacturing and design databases of the corporation, about a PCB to be assembled, is employed by a knowledge‐based module to generate assembly plans to build the PCB. A line balancing procedure is employed to select the most adequate assembly plan of those generated by the knowledge‐based module. The final assembly plan is then presented to the operators as a diagram with instructions for the assembly of the PCB. IMAPS has increased the speed to generate assembly plans from 120 hours to four hours. The final computer‐aided assembly planning system implemented in the company has taken the concepts developed in IMAPS; they have been implemented in C and C++. Lessons and experiences learned while developing and implementing IMAPS are presented.

The product family assembly line (PFAL) is a mixed model-assembly line, which is widely used in mass customization and intelligent manufacturing. The purpose of this paper is to study the problem of PFAL, a flexible (evolution) planning method to respond to product evolution for PFAL, to focus on product data analysis and evolution planning method.

The evolution balancing model for PFAL is established and an improved NSGA_II (INSGA_II) is proposed. From the perspective of data analysis, dynamic characteristics of PFAL are researched and analyzed. Especially the tasks, which stability is considered, can be divided into a platform and individual task. In INSGA_II algorithm, a new density selection and a decoding method based on sorting algorithms are proposed to compensate for the lack of traditional algorithms.

The effectiveness and feasibility of the method are validated by an example of PFAL evolution planning for a family of similar mechanical products. The optimized efficiency is significantly improved using INSGA_II proposed in this paper and the evolution planning model proposed has a stronger ability to respond to product evolution, which maximizes business performance over an effective period of time.

The assembly line designers and managers in discrete manufacturing companies can obtain an optimal solution for PFAL planning through the evolution planning model and INSGA-II proposed in this paper. Then, this planning model and optimization method have been successfully applied in the production of small wheel loaders.

The purpose of this paper is to develop an automatic disassembly navigation approach for human interactions in the virtual environment to achieve accurate and effective virtual assembly path planning (VAPP).

First, to avoid the error-prone human interactions, a constraint-based disassembly method is presented. Second, to automatically provide the next operable part(s), a disassembly navigation mechanism is adopted. Finally, the accurate assembly path planning can be obtained effectively and automatically by inversing the ordered accurate disassembly paths, which are obtained interactively in the virtual environment aided with the disassembly navigation matrix.

The applications present that our approach can effectively avoid the error-prone interactive results and generate accurate and effective VAPP.

There are several works that could be conducted to make our approach more general in the future: to further study the basic disassembly direction deducing rules to make the process of determining disassembly direction totally automatic, to consider the hierarchy of the parts in virtual reality system and to consider the space for assembly/disassembly tools or operators.

The approach has the following characteristics: a new approach to avoid the error-prone human interactions for accurate assembly path planning obtaining, a new constraint deducing method for determining the disassembly semantics automatically or semi-automatically is put forward and a new method for automatically identifying operable parts in VAPP is set forward.

This paper aims to investigate automatic assembly planning for robot and manual assembly.

The octree decomposition technique is applied to approximate a computer‐aided design model with an octree representation which is then used to generate robot and manual assembly plans. An assembly planning system able to generate assembly plans was developed to build these prototype models.

Octree decomposition is an effective assembly planning tool. Assembly plans can automatically be generated for robot and manual assembly using octree models.

One disadvantage of the octree decomposition technique is that it approximates a part model with cubes instead of using the actual model. This limits its use and applications when complex assemblies must be planned, but in the context of prototyping can allow a rough component to be formed which can later be finished by hand.

Assembly plans can be generated using octree decomposition, however, new algorithms must be developed to overcome its limitations.

This paper has proved that the octree decomposition technique is an effective assembly planning tool. As a result, an assembly planning system has been developed. Assembly plans for automatic and manual assembly can be generated automatically by the proposed system, which is a novelty since there are no fully automatic assembly planning systems for manual assembly reported in the literature.

The purpose of this paper is to develop a planner for finding an optimal assembly sequence for robots to assemble objects. Each manipulated object in the optimal sequence is stable during assembly. They are easy to grasp and robust to motion uncertainty.

The input to the planner is the mesh models of the objects, the relative poses between the objects in the assembly and the final pose of the assembly. The output is an optimal assembly sequence, namely, in which order should one assemble the objects, from which directions should the objects be dropped and candidate grasps of each object. The proposed planner finds the optimal solution by automatically permuting, evaluating and searching the possible assembly sequences considering stability, graspability and assemblability qualities.

The proposed planner could plan an optimal sequence to guide robots to do assembly using translational motion. The sequence provides initial and goal configurations to motion planning algorithms and is ready to be used by robots. The usefulness of the proposed method is verified by both simulation and real-world executions.

The paper proposes an assembly planner which can find an optimal assembly sequence automatically without teaching of the assembly orders and directions by skilled human technicians. The planner is highly expected to improve teachingless robotic manufacturing.

This study aims to present a new haptic-enabled virtual assembly system for the automatic generation and objective assessment of assembly plans. The system is intended to be used as an assembly planning tool along the product development process.

The generation of product assembly plans is based on the analysis of the assembly movements and operations performed by the user during the virtual assembly execution, and the objective assessment of product assembly is based on the definition and computation of new proposed assembly metrics.

To evaluate the system, a case study corresponding to the assembly of a mechanical component is presented and analyzed. The results demonstrate that the proposed system is an effective tool to plan and evaluate different product assembly strategies in a more practical and objective approach than existing assembly planning methods.

Although the virtual assembly execution time is larger than the real assembly execution time, the assembly planning and evaluation results provided by the system are valid. However, the development of higher performance collision detection algorithms is needed to reduce the simulation time.

The proposed virtual assembly system is able to not only simulate and automatically generate assembly plans but also objectively assess them from the virtual assembly task execution. The introduction and use of several assembly performance metrics to objectively evaluate assembly strategies in virtual assembly also represents a novel contribution.

The ever‐increasing demand for rationalization of manufacturing activities requires closer co‐operation and integration between design and production planning. Since the impact on the overall cost of production of designing a product for ease of assembly was realized, feedback from assembly planning to the design process has become important for improving the design. Traditionally, planning for assembly takes place after the design of the product has been completed. Often it proves necessary to modify a design, because some aspect is not particularly convenient or efficient under the available assembly facilities. However, considerable time and cost savings can be made by making assembly‐planning information available to design engineers, so that they can take account of assembly factors when designing a product.

Assembly planning and scheduling are two major functions in circuit board manufacturing. Currently, assembly plans are developed in the absence of information about the state of the shop floor at the execution time of the assembly operation. In effect, these assembly plans may impose unnecessary restrictions on scheduling. As a result, scheduling conflicts, bottlenecks, imbalance in assembly lines and machine congestion that lead to lateness and excessive production and shipping costs are inevitable. Compares the performances of the traditional method of isolated planning and scheduling with a proposed method of simultaneous generation of assembly plans and schedules in electronic assembly operations. Simulated scenarios indicate the potential superiority of the integrated system.