Constraint Recognition Research Articles

Motion Constraint Recognition and Its Application Oriented to Multibody Simulation

Adding motion constraints among parts is an important step link in the process of building a multibody simulation model. In order to add motion constraints among parts automatically for a multibody system,degree of motion constraint and its algorithm are put forward.Firstly,the degrees of translational constraints(DOTC)and the degrees of rotational constraints(DORC)are recognized from the position and orientation information among parts.Secondly,the DOTC and DORC of a couple of parts are computed by the constraint merger algorithms.Finally,the motion constraints are recognized through the degree of motion constraint mapping table.This method has been verified in the simulation test of low-voltage circuit breakers,and the results show that it is feasible.

Research on Exact Placement Technology of Virtual Assembly for Large-Scale Products

Due to big structure and complex process for some large-scale products (such as planes and rockets), the workers have to try many times and move around in the products to accomplish the assembly operations for high-precision requirements. Thus, the efficiency is low and the cost is high in the assembly process. To deal with that, the virtual assembly (VA) system for large-scale products is developed in this paper. First a new VA environment considering human activity is set up, and then a hierarchical assembly process list (HAPL) model and a dynamic constraint recognition algorithm is proposed to realize exact placement for large-scale products in VA system. Finally, the method is verified by the development VA system which successfully applied in the process of satellite assembly. Moreover, the method can be used in the common VA systems for assembly planning.

Responding to Activism: An Experimental Analysis of Public Relations Strategy Influence on Attributes of Publics

Experimental methods were used to examine the influence of public relations strategies on attributes of publics. Specifically, public relations strategies derived from Hazleton and Long's (1988) public relations process model were tested to determine strategy influence on problem recognition, involvement, constraint recognition, and goal compatibility toward an organization responding to activism. Results indicate that the attributes of problem recognition and involvement are influenced by public relations strategies. In addition, the findings of this study support the situational theory of publics. Items measuring involvement and goal compatibility were the strongest predictors of information seeking behavior. Findings indicate that goal compatibility is a predictor of strategy effectiveness.

The Roles of Perceived “Shared” Involvement and Information Overload in Understanding How Audiences make Meaning of News about Bioterrorism

This study integrated the situational theory of publics with theories in risk communication to explore reactions to simulated media coverage of food terrorism. Focus group participants, given news scenarios about a terrorist threat on a U.S. food product, discussed problem recognition, level of involvement, constraint recognition, fear, risk, and social connections. Findings revealed a sense of “shared” involvement that influenced how participants perceived risk. When participants perceived the source of information was in “the same boat” as them, they were more likely to pay attention. Also, news coverage increased feelings of “information overload,” which led participants to shut down cognitively and deny the need for protective action.

Assembly process modeling for virtual assembly process planning

Virtual assembly process planning (VAPP) provides a more efficient, intuitive and convenient method for assembly process planning. Previous efforts in this field are concentrated on how to assemble components together and how to analyze this assembly process in a virtual environment. However, how the interactive planning process can be modeled and organized, which is important for VAPP because of its significant influence on data organization and planning efficiency, are mostly not included. Based on analysis of the requirement of VAPP, a hierarchical assembly task list (HATL) model is proposed. In the model, assembly tasks are defined to express component assembling operations and are sequentially and hierarchically organized according to different subassemblies, which can perfectly model the construction process of product. For each assembly task, its major mission is to establish assembly relations, which is realized by an automatic geometrical constraint recognition mechanism. A three-layer virtual part model and a modified collision detection algorithm are firstly put forward to provide basic information for it. Then the automatic constraint recognition algorithm based on assembly intents filtering mechanism including destination intent, design intent and precedence intent, is detailed. All models and algorithms have been verified by a desktop-mode experiment VAPP system. However, it can also be suitable for immersive mode.

An Empirical Analysis of the Influence of Perceived Attributes of Publics on Public Relations Strategy Use and Effectiveness

This study replicates and extends previous research by examining the influence of problem recognition, constraint recognition, involvement, and goal compatibility on use of informative, facilitative, persuasive, and cooperative problem-solving strategies. Members of the Public Relations Society of America (n = 403) were surveyed using direct mail and online modes of administration. The results indicate that perceived attributes of publics significantly influence public relations strategy use in organizations. In addition, attributes of publics were significant predictors of strategy effectiveness. Goal compatibility was found to be the strongest predictor of effectiveness across strategies.

A methodology for solid modelling in a virtual reality environment

This paper presents a methodology for solid modelling in a virtual reality (VR) environment. Solid modelling in the VR environment is precisely performed in an intuitive manner through constraint-based manipulations. A hierarchically structured and constraint-based data model is developed to support solid modelling in the VR environment. Constraint-based manipulations are realized by allowable motions for precise 3D interactions in the VR environment. A mathematical matrix is presented for representing allowable motions. A procedure-based degree-of-freedom combination method for 3D constraint solving is presented for deriving the allowable motions from constraints. A rule-based constraint recognition engine is developed for both constraint-based manipulations and implicitly incorporating constraints into the VR environment. A prototype system has been implemented to testify the feasibility of the presented methodology.

A Virtual Environment for the Design and Simulated Construction of Prefabricated Buildings

The construction industry has acknowledged that its current working practices are in need of substantial improvements in quality and efficiency and has identified that computer modelling techniques and the use of prefabricated components can help reduce times, costs, and minimise defects and problems of on-site construction. This paper describes a virtual environment to support the design and construction processes of buildings from prefabricated components and the simulation of their construction sequence according to a project schedule. The design environment can import a library of 3-D models of prefabricated modules that can be used to interactively design a building. Using Microsoft Project, the construction schedule of the designed building can be altered, with this information feeding back to the construction simulation environment. Within this environment the order of construction can be visualised using virtual machines. Novel aspects of the system are that it provides a single 3-D environment where the user can construct their design with minimal user interaction through automatic constraint recognition and view the real-time simulation of the construction process within the environment. This takes this area of research a step forward from other systems that only allow the planner to view the construction at certain stages, and do not provide an animated view of the construction process.

A constraint manager to support virtual maintainability

Virtual prototyping tools have already captivated the industry's interest as viable design tool. One of the key challenges for the research community is to extend the capabilities of Virtual Reality technology beyond its current scope of ergonomics and design reviews. The research presented in this paper is part of a larger research programme that aims to perform maintainability assessment on virtual prototypes. This paper discusses the design and implementation of a geometric constraint manager that has been designed to support physical realism and interactive assembly and disassembly tasks within virtual environments. The key techniques employed by the constraint manager are direct interaction, automatic constraint recognition, constraint satisfaction and constrained motion. Various optimization techniques have been implemented to achieve real-time interaction with large industrial models.

Identification and Characterization of Regular Surfaces from Unorganized Points by Normal Sensitivity Analysis

In this paper, the concept of free motion subspace is introduced and utilized to characterize the special kinematic properties of regular surfaces, including planes, natural quadrics, and regular swept surfaces. Based on the concept, a general approach is developed to automatically identify the surface type and calculate the associated geometric parameters of an unknown surface from unorganized measurement points. In the approach, a normal sensitivity matrix, that characterizes the normal perturbation of surface points under differential motions, is derived. With the normal sensitivity matrix, it is shown that the free motion subspace of a surface can be determined through a regular eigen analysis. From the identified free motion subspace, the surface type of a regular surface can be determined and its geometric parameters can be simultaneously computed. An algorithm that identifies the free motion subspace of an unknown surface from its unorganized sample points has been implemented. Experiments are carried out to investigate the robustness and efficiency of the developed algorithm. The developed algorithm can be used to solve various problems including geometric primitive classification and parameter estimation, regular swept surface reconstruction, geometric constraint recognition and multi-view data registration. Integrated with state-of-art segmentation techniques, the proposed method can be used for object recognition, robot vision, and reverse engineering.

Research of movement navigation based on assembly constraint recognition

The requirements and features of virtual assembly movement navigator are analyzed to help operators flexibly manipulate virtual objects, precisely locate or assemble virtual parts in virtual environment. With the degree-of-freedom analysis, the assembly constraint hierarchical model is constructed and the system's constraints are built dynamically. Thus, all objects in virtual environment can be located reasonally by the navigator. Moreover, the assembly constraint recognition in the process of assembly and movement correction is also discussed.

Research of guidance technology for assembly modeling in virtual environment

Technology of movement and knowledge guidance in virtual assembly is presented. The designer can move the mechanical part precisely under the movement guidance. The movement guidance is implemented based on constraint recognition and assembly degree of freedom analysis. A multi-hierarchy knowledge base is built to represent the assembly knowledge and information. The virtual assembly system judges the requirement of the designer based on the context of design task and searches for the useful knowledge and information, which can be provided to the designer in a natural way.

Correlates of Accuracy and Inaccuracy in the Perception of the Climate of Opinion for Four Environmental Issues

This study examines some of the psychological and social structural correlates of accuracy and inaccuracy in assessments of the climate of opinion about environmental problems using data from a telephone survey of 1,002 adults. News media use, news media influence, and information seeking were associated consistently with accurate assessments of the majority opinion. Situational theory's problem and constraint recognition were associated with accurate estimates of the climate of opinion and provided a means of determining whether or not respondents were actually accurate or were simply projecting their own opinions to the majority. Interpersonal discussions and environmental concern were associated with inaccurate assessments of majority opinion.

An approach to solid modeling in a semi-immersive virtual environment

Researches on using virtual reality (VR) to support computer-aided design are rapidly increasing in recent years. This is because VR techniques are very helpful in improving the interactivity and 3D visualization function of CAD systems. In this paper, we present an approach to solid modeling in a semi-immersive virtual environment. The approach allows users to create, manipulate and visualize a precise solid model by direct 3D manipulations and voice commands in a virtual environment with a 3D input device. In the approach, to make the solid model created and modified by direct 3D manipulations precise, real-time constraint recognition, propagation and solution algorithms are developed and utilized. An extended solid model is also adopted to effectively support the solid modeling by direct 3D manipulations. The experiment shows that the approach enables users to conduct solid modeling intuitively, effectively and accurately, thus can be used for both early stage design and detailed design.

The utility of situational theory of publics for assessing public response to a disaster prediction

The study of public response to disasters is a relatively recent discipline that developed following the passage of the Earthquake Hazards Reduction Act of 1977. Because earthquake prediction is an inexact science, few formal predictions have been issued, which has limited the opportunity to study public response to predictions. The purpose of this study was to examine the utility of public relations theory, specifically situational theory of publics, for assessing response to the New Madrid earthquake prediction. Situational theory demonstrates that there is not a single, general public for disaster predictions as has been assumed in studies of disaster response. Instead, multiple publics develop in response to a prediction based on how members of those publics view the situation. Contrary to previous findings that believability and personalized risk are correlated constructs, high personalized risk was associated with high constraint recognition regardless of belief in the prediction. Based on the findings, suggestions are proposed for the development of more effective messages for communicating with publics at risk.

Direct 3D Manipulation Techniques for Interactive Constraint‐based Solid Modelling

AbstractThis paper presents a novel constraint‐based 3D manipulation approach to interactive constraint‐based solid modelling. This approach employs a constraint recognition process to automatically recognise assembly relationships and geometric constraints between entities from 3D manipulation. A technique referred to as allowable motion is used to achieve accurate 3D positioning of a solid model by automatically constraining its 3D manipulation without menu interaction. A set of virtual design tools, which can be used to construct constraint‐based solid models within a virtual environment, are also supported. These tools have been implemented as functional 3D objects associated with several pre‐defined modelling functions to simulate physical tools such as a drilling tool and T‐square. They can be directly manipulated by the user, and precisely positioned relative to other solid models through the constraint‐based 3D manipulation approach. Their modelling functions can be automatically triggered, depending upon their associated constraints and the user's manipulation manner. A prototype system has been implemented to demonstrate the feasibility of these techniques for model construction and assembly operations.

Grunig's Situational Theory: A Replication, Application, and Extension

Grunig's situational theory segments publics from a larger population based on the activeness or passiveness of communication behavior. This study found support for the Grunig model in a survey conducted during the 1990 governor's race in Kansas. The variables of the theory—problem recognition, level of involvement, and constraint recognition—accurately predicted different levels of communication activity about the election. The theory also predicted the outcomes of communication successfully. In contrast to previous studies using the situational theory, this study found a strong relationship between the situational variables and standard demographic characteristics of age, education, and income—thus suggesting the possibility of using segmentation procedures that include both situational variables and media demographics. Finally, the article suggests that the situational theory could be enhanced by including an energy variable—specifically Hull-Spence's behavior equation—and a media use variable.

Effect of Support and Personal Distance on the Definition of Key Publics for the Issue of AIDS

Situational theory predicts that those with a high problem recognition, high involvement and low constraint recognition will be active information seekers. A telephone survey of 493 individuals in a Southwestern city finds knowledge of AIDS is high among all groups and, as hypothesized, distinguishing audiences according to personal and impersonal levels of problem recognition, involvement and constraint recognition provides a useful extension of James Grunig's situational theory. The addition of valence of support as a predictor is also found to enhance the use of the situational variables in identifying target audiences for communication campaigns.

Improving Mechanical Design Decisions with Alternative Formulations of Constraints

SUMMARY Mechanical design equations which relate performance and functionality to design variables are often highly coupled, non-linear parametric equations. The structure of these interacting equations can be simplified by a reformulation based on the creation of alternative design variables. For many design configurations the reformulations results in highly beneficial improvements in equation monotonicity and complexity. The benefits include convenience and expediency in quantitative evaluations in addition to enhanced physical insight. They facilitate such important design activities as computing satisfactory solutions, active constraint recognition for optimizations, and the decomposition of design decisions. The reformulations can be thought of as alternative views of the design configuration that provide abstractions which can promote design synthesis. In this paper we discuss and illustrate the nature of these benefits with a number of simple design examples.

Audience complexityas a component of campaign planning

This study uses the Minnesota Heart Health Program to examine some of the theoreticalimplications for campaign planning in public relations. Researchers used more than 600 interviews in two Minnesota towns to probe the effectiveness of the heart health campaign. The researchers found evidence that audience complexity affects the outcome of a campaign and thus should be one of the factors taken into consideration in campaign planning, even though it is often neglected. The researchers also suggest that if audience complexity analysis indicates that involvement and constraint recognition are low, campaign messages should be planned to influence these levels to achieve greater campaign success.