Precedence relationship representations of mechanical assembly sequences

Two types of precedence relationship representations for mechanical assembly sequences are presented: precedence relationships between the establishment of one connection between two parts and the establishment of another connection, and precedence relationships between the establishment of one connection and states of the assembly process. Precedence relationship representations have the advantage of being very compact. The problem with these representations was how to guarantee their correctness and completeness. Two theorems are presented each of which leads to the generation of one type of precedence relationship representation guaranteeing its correctness and completeness for a class of assemblies

An assembly oriented design framework for product structure engineering and assembly sequence planning

The paper describes a novel framework for an assembly-oriented design (AOD) approach as a new functional product lifecycle management (PLM) strategy, by considering product design and assembly sequence planning phases concurrently. Integration issues of product life cycle into the product development process have received much attention over the last two decades, especially at the detailed design stage. The main objective of the research is to define assembly sequence into preliminary design stages by introducing and applying assembly process knowledge in order to provide an assembly context knowledge to support life-oriented product development process, particularly for product structuring. The proposed framework highlights a novel algorithm based on a mathematical model integrating boundary conditions related to DFA rules, engineering decisions for assembly sequence and the product structure definition. This framework has been implemented in a new system called PEGASUS considered as an AOD module for a PLM system. A case study of applying the framework to a catalytic-converter and diesel particulate filter sub-system, belonging to an exhaust system from an industrial automotive supplier, is introduced to illustrate the efficiency of the proposed AOD methodology

NASA Center for Intelligent Robotic Systems for Space Exploration

NASA's program for the civilian exploration of space is a challenge to scientists and engineers to help maintain and further develop the United States' position of leadership in a focused sphere of space activity. Such an ambitious plan requires the contribution and further development of many scientific and technological fields. One research area essential for the success of these space exploration programs is Intelligent Robotic Systems. These systems represent a class of autonomous and semi-autonomous machines that can perform human-like functions with or without human interaction. They are fundamental for activities too hazardous for humans or too distant or complex for remote telemanipulation. To meet this challenge, Rensselaer Polytechnic Institute (RPI) has established an Engineering Research Center for Intelligent Robotic Systems for Space Exploration (CIRSSE). The Center was created with a five year $5.5 million grant from NASA submitted by a team of the Robotics and Automation Laboratories. The Robotics and Automation Laboratories of RPI are the result of the merger of the Robotics and Automation Laboratory of the Department of Electrical, Computer, and Systems Engineering (ECSE) and the Research Laboratory for Kinematics and Robotic Mechanisms of the Department of Mechanical Engineering, Aeronautical Engineering, and Mechanics (ME,AE,&M), in 1987. This report is an examination of the activities that are centered at CIRSSE

An intelligent, free-flying robot

The ground based demonstration of the extensive extravehicular activity (EVA) Retriever, a voice-supervised, intelligent, free flying robot, is designed to evaluate the capability to retrieve objects (astronauts, equipment, and tools) which have accidentally separated from the Space Station. The major objective of the EVA Retriever Project is to design, develop, and evaluate an integrated robotic hardware and on-board software system which autonomously: (1) performs system activation and check-out; (2) searches for and acquires the target; (3) plans and executes a rendezvous while continuously tracking the target; (4) avoids stationary and moving obstacles; (5) reaches for and grapples the target; (6) returns to transfer the object; and (7) returns to base

The simulation of automated leading edge assembly

Aircraft manufacturers are experiencing a fierce competition worldwide. Improving productivity, increasing throughput and reducing costs are influencing aircraft manufacturer’s future development. In order to improve competitiveness and provide sufficient and high quality products, it should reduce operations of aircraft assembly,majority of which are still in manual process, which limit production output. In contrast, these processes can be automated to replace manual operations. Much more attention should be placed on automated application. This project aims to propose a methodology to develop the automated assembly based on robotics and use this methodology to develop a new concept of Automated Leading Edge Assembly. The research selects an automated assembly process for further evaluation and brackets assembled on the front spar of Leading Edge are chosen to be automated assembly with robot assistant. The software DELMIA is used to develop and simulate the automated assembly process of brackets based on 3-D virtual aircraft Leading Edge models. The research development is mainly divided into three phases which are: (1) The state of art on Manual Leading Edge Assembly; (2) Automated Leading Edge Assembly framework development; (3) Automated Leading Edge Assembly framework evaluation including automated assembly process simulation based on DELMIA robotics workbench and automated assembly cost estimation. The research has proposed a methodology to develop the automated assembly based on robotics, proposed a new concept of Automated Leading Edge Assembly: using robots to replace workers to finish the assembly applications in the Leading Edge, and proposed a new automated bracket assembly process with laser ablation, adhesive bonding, drilling, riveting, and robot application. These applications can attract more and more engineers’ attention and provide preliminary knowledge for further study and detail research in the future

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 344)

This bibliography lists 125 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during January, 1989. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance

Survey on assembly sequencing: a combinatorial and geometrical perspective

A systematic overview on the subject of assembly sequencing is presented. Sequencing lies at the core of assembly planning, and variants include finding a feasible sequence—respecting the precedence constraints between the assembly operations—, or determining an optimal one according to one or several operational criteria. The different ways of representing the space of feasible assembly sequences are described, as well as the search and optimization algorithms that can be used. Geometry plays a fundamental role in devising the precedence constraints between assembly operations, and this is the subject of the second part of the survey, which treats also motion in contact in the context of the actual performance of assembly operations.Peer ReviewedPostprint (author’s final draft

Optimization of robotic assembly sequence

The assembly process is combination of several products into a single product. The assembly process affects manufacturing processes very great extent because it is very time consuming and expensive process. The cost of assembly can reach up to 30% of the manufacturing cost. Instability and direction change in assembly process increases the cost of assembly thus the total cost of product is increased very great extent. The production rate decreases with increase in time in assembly process, so the correct assembly sequence is needed to reduce the time and cost of assembly. For the given product assembly model, the sequences and paths of parts is determined by assembly sequence planning (ASP) to obtain the assembly with minimum costs and shortest time. Industries are taking interest in automated assembly system; robotic assembly system comes under category of this assembly system which uses robots for performing the required assembly tasks. This system is one of the most flexible assembly systems to assemble various parts into desired assembly. Robotic assembly systems can handle a wide range of styles and products, so that same product can be assembled different ways, and to recover from errors. Robotic assembly has the ability to switch to different products and styles because robotic assembly is programmable assembly and it has advantage of greater process capability. Robotic assembly is faster, more efficient and precise than any conventional process. It is very important to determine the feasible,stable and optimal assembly sequence for an assembly system. An assembly sequence plan is a high level plan for constructing a product from its component parts. It specifies which sets of parts form subassemblies, the order in which parts and subassemblies are to be inserted into each subassembly,are to be performed. The aim of the present work is to determine stable, feasible and optimal robotic assembly sequence which follows the assembly constraints and reduces the assembly cost.An important feature of this developing process is epresented by the need to automatically determine the assembly plan by recognizing the optimum sequence iv of operations based upon cost and accuracy. Products with large number of parts have several alternative feasible sequences among which optimal assembly sequence is generated. Traditional methods often generate combinatorial explosions of alternatives, with intolerable computational times. A new methodology has been developed to find out the best robotic assembly sequence among the feasible robotic sequences. The feasible robotic assembly sequences have been generated based on the assembly constraints and later, Artificial Immune System (AIS) and particle swarm optimization with mutation operation has been applied to generate feasible and optimal assembly sequences and result is compared with the previous technique. In AIS Clonal selection and Affinity maturation have been implemented to determine the optimal assembly sequence. During the implementation, each assembly sequence and its energy value have been considered as antibody and the antibody affinity respectively. In PSO, each part of the assembled product is considered as the particle (bird) and mutation operation is performed for selected assembly sequence in each iteration to update the position and velocity of each particle. To generate optimal assembly sequence, a fitness function is generated, which is based on the energy function associated with assembly sequence. The sequence which is having the best fitness value followed by all assembly constraints is treated as the optimal robotic assembly sequence. Present research work has been divided into six chapters. The introduction of the topic and the related matters including the objectives of the work are presented in Chapter 1.The literature reviews on different issues of the topic in Chapter 2. In Chapter 3 Steps of assembly sequence generation,assembly constraints, instability is presented Chapter 4 presents generation of stable assembly sequences using Novel immune approach method and Particle swarm optimization with mutation operation for the generation of robotic assembly sequence. In Chapter 5, Result and discussion obtained from different methods are presented. Finally, Chapter 6 presents the conclusion and future work

Evaluation of graphical user interfaces for augmented reality based manual assembly support

Augmented reality (AR) technology is advancing rapidly and promises benefits to a wide variety of applications&mdashincluding manual assembly and maintenance tasks. This thesis addresses the design of user interfaces for AR applications, focusing specifically on information presentation interface elements for assembly tasks. A framework was developed and utilized to understand and classify these elements, as well as to evaluate numerous existing AR assembly interfaces from literature. Furthermore, a user study was conducted to investigate the strengths and weaknesses of concrete and abstract AR interface elements in an assembly scenario, as well as to compare AR assembly instructions against common paper-based assembly instructions. The results of this study supported, at least partially, the three hypotheses that concrete AR elements are more suitable to convey part manipulation information than abstract AR elements, that concrete AR and paper-based instructions lead to faster assembly times than abstract AR instructions alone, and that concrete AR instructions lead to greater increases in user confidence than paper-based instructions. The study failed to support the hypothesis that abstract AR elements are more suitable for part identification than concrete AR elements. Finally, the study results and hypothesis conclusions are used to suggest future work regarding interface element design for AR assembly applications

Aerospace medicine and biology: A cumulative index to a continuing bibliography (supplement 345)

This publication is a cumulative index to the abstracts contained in Supplements 333 through 344 of Aerospace Medicine and Biology: A Continuing Bibliography. Seven indexes are included -- subject, personal author, corporate source, foreign technology, contract number, report number, and accession number