Integration of Rule-based Process Selection with Virtual Machining for Distributed Manufacturing Planning
3.5 Integration Approaches
animated feature generation, which morphs the pre-machining geometry to the post- machining geometry. The workpiece SG shown in Figure 3.20(b) provides an outline of this functionality. As the user starts the animation for virtual machining, the BG of the stock geometry is replaced with the BG pre-machining feature static workpiece geometry and, at the same moment, the morphing in dynamic behaviour is also initiated. An alpha object, which decides the timeframe for the animation is started at this instant. The same alpha object is used in the tool BG and, therefore, coordinates the translation motion of the tool with the changes in workpiece shown using intermediate geometry. This coordinating action is performed inside the dynamic behaviour node by smoothly transforming an intermediate geometry into the next geometry, assigned to that time instant. When the workpiece is completely transformed into its final geometry, a static workpiece geometry BG is replaced with the previous BG, having dynamic behaviour.
virtual world (Drawable3D,AnimPanel, and AnimApplet). The planning object may decide (based on user request or based on the system status) to select a certain level of detail and modify it during the application session.
Figure 3.21. Interactions between ImpObject and visual components
As an example of the virtual world, the contract between the classes AnimPanel andImpObject is specified through the Drawable3D interface as shown in Figure 3.22. AnimPanel is used to display a model and to control the view point, lighting, colour, etc. It relies on ImpObject for provision of the model and data to be displayed in the form of scene graph. The figure illustrates that AnimPanel implements methods setView(),setLight(), and paintComponent(), while ImpObject (and its subclasses) implement getShapeList() and createSceneGrpah() methods.
With all of these methods declared in the Drawable3D interface, the actual display is achieved through cooperation of both AnimPanel and ImpObject instances.
Figure 3.22. Interaction between AnimPanel and ImpObject through Drawable3D interface
3.5.2 Distributed Approach
The distributed approach for integration of 3I-PP process selection module and IMPlanner’s virtual machining module (IVM) is achieved using TCP/IP sockets (see
Figure 3.23). 3I-PP plays the rule of process selection server and IVM acts as a client. Upon receiving a request from IVM, 3I-PP generates corresponding data using the process selection module and sends the summary of results as an XML document (or stream). The XML document is parsed at the client side using a DOM parser and the summary is shown as a list of features or processes in the IVM’s GUI.
The user may select any feature or process to obtain its details. This initiates another request to the 3I-PP server and, at this time, the XML stream with the complete data is retrieved by the IVM. The document is parsed by a SAX parser, and the required process plan model objects are created and displayed as a tree model. Selection of any manufacturing process in the tree triggers its virtual machining in AnimApplet.
N E T W O R K XML
Document Stream XML Parser
Java-XML Document
Java Object Mapper
Java Objects
Process Visualisation Lisp XML
Generator
Process Selection (3I-PP)
Socket Connection
Client Requests
(feature data) CLIENT
Stream
SERVER
Save to File Web
Browser
User Interface
Figure 3.23. Data exchange between 3I-PP and IMPlanner
Figure 3.24. Distributed process selection in 3I-PP and virtual machining in IMPlanner
The integration of both systems consists in displaying both applications visually as shown in Figure 3.24. The IMPlanner GUI, called “Data Exchange Interface” is used for interaction with 3I-PP. This GUI directs the execution of the described procedure. The following tasks have been performed in the snapshot shown in the figure: (a) connect to the 3I-PP server, (b) load 3I-PP (3I-PP interface is shown in the front), (c) load an example (with seven features). The same set of seven features is shown in both modules. From this point, a user selects a feature and directs the request to 3I-PP to execute the process selection routine for that feature and to retrieve a summary. After that, the tree will be expanded and the process may be selected to execute virtual machining (run AnimApplet) for this process. The IVM interface may also be shown as an applet in a Web browser.
3.5.3 Integrated Application
The modular approach in model building and visualisation described in Section 3.5.1 enables rapid development of a tightly integrated application that demonstrates integration of rule-based process selection with virtual machining. The algorithms and procedures described earlier are integrated into the application/applet (see the figures in Section 3.6) that allows the user to perform the procedures described earlier. The application consists of:
Toolbar, which provides the user with buttons to perform a sequence of actions (open model CAD file, open stock CAD file, open/save XML file, load Jess engine, create facts, run engine) on a selected part CAD model to complete the process selection.
Tree model, which provides the user with a hierarchical model of the part with options to select any node in the tree and review/inspect its content.
Information tabbed panel, which provides the user with various views of the part model and its components; by selecting individual tabs, the user is able to inspect feature/process data (in Data tab), verify the geometry of the part, feature, or process (in Wireframe tab), create a virtual machining model of the selected manufacturing process (in Animation tab), or monitor rule engine execution (in Jess Output tab).
The application uses a unified interface to different views for process planning objects defined in Section 3.5.1 and provides a rich user-friendly environment for process planning. The application execution will be described in Section 3.6.
3.5.4 XML-based Web Distributed Application
The distributed application can also be achieved using pure XML data exchange, which provides the benefit of neutral data representation in all phases of process planning. As mentioned in the previous section, IMPlanner provides an XML representation of the hierarchical process plan model that includes parts, features and processes.
Each class in the process plan model implements an XML writer and an SAX parser that allow reading and writing XML streams. The necessary data for each of them is stored in XML format that is modelled in a fashion similar to STEP. At each
stage of the described procedure, the resulting data can be saved into an XML file.
This enables implementation of different applications (or applets) that can be run on separate computers, and even within Web browsers, and passing a partial process plan model between them.
The benefit of such an approach is in utilising underlying tools and applications on individual computers. For example, the feature-mapping task requires that a Unigraphics CAD package be installed and requires a licence for it, the process selection task requires the license and installation of a Jess engine, while virtual machining requires Java 3D as part of the installed Java Runtime Environment (JRE). Also, in practice, problems often arise when incompatible versions of software are run. XML-based data exchange avoids all these troubles by allowing each step of the process planning task run in an agent-based fashion and providing a unified data exchange mechanism, which carries both the data and its interpretation.
The cases of utilising IMPlanner with XML data exchange and Web-based applets are described in [3.21] and [3.22].