Dejun Zhang

Quantitative optimization of interoperability during feature-based data exchange

Sharing feature-based computer-aided design (CAD) models is a challenging problem that is frequently encountered among heterogeneous CAD systems. In this work, a new asymmetric strategy is presented to enrich the theory of feature-based interoperability, particularly when addressing a singular feature or singular sketch. This paper analyzes the semantic asymmetry singular feature interoperability (SA-SFI) and parameter asymmetry singular sketch interoperability (PA-SSI) in detail. We pay special attention to the problem of PA-SSI, which is universally significant in collaborative product development (CPD). The objective of PA-SSI is to develop an optimized model to exchange a singular sketch (spline) to ensure that the exchanged model both maintains high geometric fidelity and can be effectively edited in the target CAD system. The proposed method applies the estimation of distribution algorithm (EDA) to automatically solve this problem, and a Gaussian mixture model (GMM) is built according to the promising solutions. Furthermore, Hausdorff distance is adopted to calculate the fitness, and a local optimization operator is designed to enhance the global search capability of the population. Experimental results demonstrate that the proposed approach can maintain a sufficiently high geometric fidelity, and ensure that the exchanged model of the target CAD system can be parametrically edited.

Service-Oriented Feature-Based Data Exchange for Cloud-Based Design and Manufacturing

With the rapid development of service-oriented computing (SOC)/service-oriented architecture (SOA), cloud computing and web services, cloud-based design and manufacture (CBDM) is emerging as state-of-the-art technologies and methodologies to enable collaborative product development (CPD). CBDM-enabled CPD can provide cost-effective, flexible and scalable solutions to collaborative partners by sharing the resources in the applications of design and manufacturing. Feature-based data exchange (FBDE) has been one of the key issues in history of CPD and should be adapted in lasted CBDM-enabled CPD. Firstly this paper presents a service-oriented architecture for data exchange in CBDM. Within this architecture, FBDE was registered as service and FBDE users in the CBDM environment can acquire a set of FBDE services to replace the traditional FBDE functions among heterogeneous CAD systems. Secondly, in order to put the philosophy of FBDE-as-a-Service into practice for CBDM, this paper proposes a peer to peer (P2P) approach for service-oriented FBDE, which revolutionizes the traditional centralized and neutral-file based approach. Thirdly, technique issues of FBDE-as-a-Service in P2P architecture are discussed in details, including constituting of the P2P FBDE service, procedure of service-oriented P2P FBDE, pre-P2P FBDE service, topological entity matching between pre/post-P2P service and post-P2P FBDE service. Finally, a case study of data exchange is tested to demonstrate the proposed idea of service-oriented FBDE for CBDM.

Meta-operation conflict resolution for human---human interaction in collaborative feature-based CAD systems

Conflicts resolution is one of the key issues in maintaining consistency and in supporting smooth human–human interaction for real-time collaborative systems. This paper presents a novel approach of meta-operation conflict resolution for feature-based collaborative CAD system. Although commutative replicated data type (CRDT) is an emerging technique for conflict resolution, it is not capable of resolving conflicts among meta operations for 3D CAD systems. By defining 3 types of meta operations, this work extends CRDT capability to meta operation conflict resolution from 1D to 3D applications. The paper defines the dependency, casuality, conflict and compatible relations specific for 3D collaborative CAD systems. The conflicts of feature-based operations are automatically detected by tracking topological entity changes with the assistance of a persistent data structure, topological entity structure tree (

To Support Human-Human Interaction in Collaborative Feature-Based CAD Systems

TES\_Tree

Feature-based data exchange as Service for Cloud Based Design and Manufacturing

TES_Tree). An efficient commutativity-based confliction combination method is proposed to preserve the design intention of each user in a transparent way and maintains the eventual consistent state of the system. The proposed methods are tested in a prototype system with case studies, time complexity analysis and correctness proof.

Product data exchange of complex shape based on parametric curve

Feature-based data exchange (FBDE) among CAD systems is one of the most important problems in collaborative product development. In this article, we present a procedure recovery-based solution for FBDE. The main difference between our solution and previous approaches is that a peer-to-peer architecture is adopted and the feature modelling procedure is recovered to retrieve the information that exists in the procedure. Our approach is composed of three key steps. First, in a source CAD system, first-order feature information is retrieved from a feature model. Then, the retrieved first-order feature information is used to recover the feature modelling procedure in the source CAD system and second-order feature information is retrieved during the procedure recovery. Finally, in a target CAD system, the feature model is reconstructed by using the retrieved information. The prototype implementation demonstrates that our approach works well for FBDE among various commercial CAD systems and improves the previous approaches in both the architecture and the retrieval of the procedure.

A method for topological entity matching in the integration of heterogeneous CAD systems

This paper discussed several key issues for human-human interaction in a collaborative CAD system. The first issue is to track the changing history of topological entities of a part model. A tree-like structure TES_Tree is adopted to record the tracking results in different topological entity changing scenarios. The second issue is the consistency maintenance mechanism in different topological entity variation situations. The third issue is the group Undo/Redo policy for error recovery which is important to eliminate errors propagated to every collaborative site.

A group Undo/Redo method in 3D collaborative modeling systems with performance evaluation

In 3D collaborative modeling systems, users need a convenient mechanism to repeatedly modify the models they are operating on. In this paper, we contribute a selective undo/redo solution for users to select arbitrary operation to undo. With the consistency maintainence mechanism we proposed, operations need to be re-arranged on each site for after their arriving. Both history buffer and model state stream are adopted to present the arriving sequence of operations and their actual execution sequence. In case of concurrent undo/redo, undo state vector is proposed to make sure that an operation can only be undone once and redone by the designer who undoes it. Based on all the precautions we have made, an undo/redo algorithm is proposed. The algorithm has been verified in the prototype we implemented.