Virtual Assembly Method Research Articles

A Virtual Assembly Technology for Virtual–Real Fusion Interaction of Ship Structure Based on Three-Level Collision Detection

With the rapid advancement of new-generation information technology, the virtual–real fusion interaction has increasingly become a crucial technique for structural analysis to determine the strength envelope of hulls. A high-precision assembly of the experimental devices in a virtual environment is vital. A virtual assembly method for a structural virtual–real fusion test based on the oriented bounding box (OBB) algorithm, the Devillers and Guigue algorithm, and differential triangle facets algorithm are proposed in this paper. The experiment of the connector in a typical offshore floating platform is performed as a case, which indicates that the virtual assembly method proposed in this paper enables the assessment of assembly virtually prior to the actual experiment, and the assembly accuracy can reach 0.01 mm. The digitalization and virtual–real fusion interaction for the mechanical experiment of hulls are advanced to ensure efficiency, safety, and economy.

Measurement and optimization method for aero-engine rotors based on binocular multi-line laser sensing and virtual assembly

During the assembly of aero-engine rotors, eccentricity and tilt errors along the radial and axial direction result in uneven loading along the mating surface, which significantly impacts the operational lifespan of the rotor. This paper proposes a three-dimensional contour measurement system based on binocular multi-line laser sensing and conducts an aircraft engine rotor stacking virtual assembly technology system, to response the practical requirements of aircraft engine rotor unit production assembly engineering. We combine multi-line structured light active projection device with the binocular stereo vision model to construct the contour measurement system, which enhances the surface features of the projected object by adhering to the common constraint of structured line and stereo vision. Furthermore, the error propagation model for multi-stage rotor assembly to investigate the mechanism of error impact is established aiming to facilitate quantitative research on virtual assembly mechanisms. By manipulating the rotor phases and evaluating the coaxiality under various conditions, effective prediction of phase variation can be achieved, the multi-objective benchmark virtual assembly method based on the error propagation model of multi-stage rotor coaxiality is presented. The experimental results indicate that the proposed measurement system achieves the maximum disparity between the spatial data points procured by the proposed measurement system and the predetermined value of 2.1 μm, and the maximum disparity between the target plane’s average movement distance and the preset value of 3.7 μm. The precision provided by this system effectively meets the objective of assembly phase optimization for multi-stage rotors. In the empirical experiment conducted on the three-stage rotors, both systems yielded identical optimized phases: 0° for the first-stage rotor, 270° for the second-stage rotor, and 120° for the third-stage rotor, thereby validating the efficacy of the proposed measurement and optimization method for aero-engine multi-stage rotors with virtual assembly.

A Mobile Natural Interactive Technique With Bare Hand Manipulation and Unrestricted Force Feedback for Virtual Assembly Tasks

Most existing virtual assembly technologies cannot effectively unify the operating and the feedback areas in both visualization and haptics with a large mobile workspace. Therefore, it is difficult to ensure high interactive naturalness and operational efficiency in a large assembly space. To address these problems, we propose a natural mobile interactive virtual assembly method with bare hand manipulation and unrestricted force feedback (MIVAM-BHM-UFF), covering a mobile interaction method, an unrestricted force feedback method, and a bare hand manipulation method. The mobile interaction method is developed to automatically track and capture the operator’s gestures in a moving way, expanding the interactive space. An unrestricted force feedback method is designed to provide a non-contact electromagnetic feedback force, eliminating the limitation of the traditional force feedback device and improving the interactive naturalness. A bare hand manipulation method is proposed to improve interactive efficiency by unifying the operational area and feedback area. To verify the effectiveness of MIVAM-BHM-UFF, five assembly experiments were performed. Experimental results indicate that compared with four assembly techniques, MIVAM-BHM-UFF show better user experiences in the virtual assembly processes.

Design and Dynamic Analysis of the Recirculating Planetary Roller Screw Mechanism

The recirculating planetary roller screw mechanism (RPRSM) is a transmission mechanism that engages the screw and nut threaded by multiple grooved rollers. In this paper, firstly, the design method of RPRSM nut threadless area is proposed, and the equations related to the structural parameters of nut threadless area are derived. On this basis, the cross-section design method of roller, screw and nut is constructed according to the actual situation of engagements between the screw/nut and the roller. By adjusting the gap between the two beveled edges and that between the arc and the beveled edge, the accuracy of the thread engagements between the screw/nut and the roller can be improved. Secondly, to ensure the engagements of the screw/nut and the roller, the distance equation from the center surface of the different rollers to the end surface of cam ring is given. Thirdly, combined with the working principle and structural composition of RPRSM, the component model is established according to its relevant structural parameters, and the virtual assembly is completed. Finally, the 3D model is imported into the ADAMS simulation software for multi-rigid body dynamics. The dynamic characteristic is analyzed, and the simulated values are compared with the theoretical values. The results show that the contact forces between the screw/nut and the roller are sinusoidal, mainly due to the existence of a small gap between the roller and the carrier. The maximum collision forces between the roller and cam ring are independent from load magnitude. Normally, the collision force between the roller and the carrier increases as the load increases. When RPRSM is in the transmission process, the roller angular speed in nut threadless area begins to appear abruptly, and the position of the maximum change is at the contact between the roller and the convex platform of cam ring. The design of the nut threadless area and the proposed virtual assembly method can provide a theoretical guidance for RPRSM research, as well as a reference for overall performance optimization.

A Natural Bare-Hand Interaction Method With Augmented Reality for Constraint-Based Virtual Assembly

Traditional virtual assembly methods have a high requirement in hand-eye coordination because of the separation of feedback and operation regions. These methods are inconsistent with human interaction habits and lack of naturalness because of limited interaction space and indirect interaction mode. Therefore, we propose a natural bare-hand interaction method for virtual assembly, enabling operators to interact with virtual objects by using natural gestures even while in motion. The Leap Motion controller (LMC) fixed on the Augmented Reality (AR) glasses is used to track hands of the operator and the mobility of the interactive device relieves the location limitation of assembly processes. Furthermore, AR allows operators to perform bare-hand assembly in a realistic situation. The interval Kalman filter (IKF) is applied to estimate hands’ positions to improve the accuracy of measured gesture data. Moreover, constraint assisted technology is introduced to aid operators in learning and completing assembly tasks quickly and accurately, and the assembly sequence is generated to assist the decision-making process during the interaction. Experimental results show that the proposed method can be used by non-professional operators for assembly tasks and can potentially improve assembly efficiency. Based on operator ratings about assembly experience and significant difference analysis, the proposed method performed better at providing better interactive experiences.

AN ACCURATE DIGITAL RESTORATION METHOD BASED ON ARCHITECTURAL SITE INFORMATION – A CASE STUDY OF THE JIUJING SANSHI HALL IN CHANGCHUN GARDEN

Abstract. Using records, documents, and research on Jiujing Sanshi Hall in Changchun Garden as an example, this paper showcases a method to digitally restore lost constructions to the maximum level of precision in their size, scale, architectural design, and structure using digital technology. The digital restoration can also be dynamically adjusted based on latest data. Information used to form such restorations include historical records, measurement data, and unknown data, which were then analyzed and recombined. This method fulfills the technical gap in high-precision digital restoration in China. The paper proposes an evaluation standard that involves "triple-evidence verification chain" and restoration accuracy, which can be used for most unmovable cultural relics, especially large ruins with few, scattered remains. The standard can provide a qualitative basis for the whole field of restoration research. The resulting restoration method is useful in cooperation and research between multiple cross-discipline organizations, as well as improving work efficiency and information sharing. Moreover, this restoration plan has integrated various virtual assembly methods and improved the integrity and authenticity of the site remains. It made breakthroughs in display methods of lost constructions and ruins such as enhanced showcasing of vanished ruins and changes over time. The plan also was able to enrich cultural connotation and existing contents of the ruins. The resulting restoration can be updated, and the information can be shared and used in open research.

Haptic Interaction in Virtual Reality Environments for Manual Assembly Validation

Based on an increased level of product complexity in product development processes new technologies and validation approaches are researched and applied in industry to validate assembly processes. Especially technologies that are focusing on Mixed or Virtual Reality environments are getting very popular in the field of assembly validation, because of a huge potential to reduce the necessary number of physical prototypes. Therefore costs and time within product integration phase can be saved. These technologies can provide a high level of immersion for pick-and place or assembly tasks and allow a scale 1:1 interaction with the future product or production system. Still plenty of limitations for a complete substitution of physical prototypes exist due to the lack of physical and haptic behavior of these virtual prototypes. Within this paper, a development method and applications for haptic interaction with force-feedback devices for assembly validation is presented. Focusing especially on the development process of a mixed prototype with virtual and physical elements, so called hybrid prototypes, a hard- and software framework is presented. Nowadays virtual assembly methods for Virtual Reality and computer haptics are still based on a high level of expertise in providing technology and testbeds. To keep a high level of flexibility regarding virtual validation models, easily applicable procedures for modelling, im-/exporting and configuration of the prototype are needed for a virtual assembly use case. In this paper, a new and connected processing pipeline is presented that describes and guides a non-expert user from CAD environment to the implementation and configuration of prototypes for haptic interaction.

Automated de novo molecular design by hybrid machine intelligence and rule-driven chemical synthesis

Chemical creativity in the design of new synthetic chemical entities (NCEs) with drug-like properties has been the domain of medicinal chemists. Here, we explore the capability of a chemistry-savvy machine intelligence to generate synthetically accessible molecules. DINGOS (design of innovative NCEs generated by optimization strategies) is a virtual assembly method that combines a rule-based approach with a machine learning model trained on successful synthetic routes described in chemical patent literature. This unique combination enables a balance between ligand-similarity-based generation of innovative compounds by scaffold hopping and the forward-synthetic feasibility of the designs. In a prospective proof-of-concept application, DINGOS successfully produced sets of de novo designs for four approved drugs that were in agreement with the desired structural and physicochemical properties. Target prediction indicated more than 50% of the designs to be biologically active. Four selected computer-generated compounds were successfully synthesized in accordance with the synthetic route proposed by DINGOS. The results of this study demonstrate the capability of machine learning models to capture implicit chemical knowledge from chemical reaction data and suggest feasible syntheses of new chemical matter. Artificial intelligence approaches can aid medicinal chemists to creatively look for new chemical entities with drug-like properties. A rule-based approach combined with a machine learning model was trained on successful synthetic routes described in chemical patent literature. This process produced computer-generated compounds that mimic known medicines.

Research on Remote Virtual Assembly Technology of Plug Valve Based on VRML

In this paper, three-dimensional plug valve was created. The function of virtual assembly was achieved using virtual reality modeling language. Network virtual assembly can operate, browse and assemble plug valve remotely by embedding virtual assembly in web pages. The virtual assembly method presented in this paper can be easily extended to deal with many other problems in complex engineering system if control parameters are modified properly.

Three-Dimensional Virtual Assembly of Automatic Fuel Measuring Device of Diesel Engine Test Bed Based on VRML

In this paper, three-dimensional automatic fuel measuring device of diesel engine test bed was created. The function of virtual assembly was achieved using virtual reality modeling language. Network virtual assembly can operate, browse and assemble automatic fuel measuring device remotely by embedding virtual assembly in web pages. The virtual assembly method presented in this paper can be easily extended to deal with many other problems in engineering system if control parameters are modified properly.

Research on Knowledge-Based Virtual Assembly Planning

In order to find an optimum assembly sequence in engineering design domain, a knowledge-based virtual assembly approach was put forward. Virtual assembly design environment was also introduced, and knowledge representation models for virtual assembly rules and cases are introduced and studied respectively. A side-center virtual assembly method was applied to avoid the occurrence of assembly interference. Finally, a case was employed to demonstrate the practicality of knowledge-based virtual assembly planning.

Industry case studies in the use of immersive virtual assembly

In this paper, we report on two engineering case studies that have been conducted as part of a Virtual Assembly Technology Consortium. The objectives of the case studies were to determine if immersive virtual assembly capabilities allow industry assembly situations to be modelled and studied realistically, and to demonstrate the downstream value of the virtual assembly capabilities in areas such as ergonomics, assembly installation, process planning, installation, and serviceability. What is of special significance is that instead of modelling simplified problems or perceived representative situations, the case studies were constructed from actual assembly floor projects and situations encountered at industry member sites and with considerable participation from industry engineers and manufacturing shop floor personnel. Based on the success of the case studies, the consortium members inferred that virtual assembly methods are poised to move out of the realm of special projects and test scenarios to deployment in the actual design and manufacturing cycle. However, in order to be truly accepted in industry, there are still issues to be addressed in terms of ease of use, portability of the applications, and preparation of the models for the evaluations. Thus, the case studies added a new dimension to the exploration and understanding of how this new technology could be of practical value in industry.

Collision Detection and Part Interaction Modeling to Facilitate Immersive Virtual Assembly Methods

Realistic part interaction is an important component of an effective virtual assembly application. Both collision detection and part interaction modeling are needed to simulate part-to-part and hand-to-part interactions. This paper examines several polygonal-based collision detection packages and compares their usage for virtual assembly applications with the Voxmap PointShell (VPS) software developed by the Boeing Company. VPS is a software developer’s toolkit for real-time collision and proximity detection, swept-volume generation, dynamic animation, and 6 degree-of-freedom haptics which is based on volumetric collision detection and physically based modeling. VPS works by detecting interactions between two parts: a dynamic object moving in the virtual environment, and a static object defined as a collection of all other objects in the environment. The method was found to provide realistic collision detection and physically-based modeling interaction, with good performance at the expense of contact accuracy. Results from several performance tests on VPS are presented. This paper concludes by presenting how VPS has been implemented to handle multiple dynamic part collisions and two-handed assembly using the 5DT dataglove in a projection screen virtual environment.