Case-based process planning using an object-oriented model representation

This research focuses on the development of a process-planning system. This system utilizes case-based techniques for process selection and sequencing to combine the advantages of the variant and generative approaches to process planning. The case-based process planner utilizes an object-oriented model representation to operate on general three-dimensional prismatic parts, which are represented by a collection of features (e.g. slots, pockets, holes, etc.). Each feature subplan is developed by the case-based planner. Then the feature subplans are combined into the global process plan for the part via a hierarchical plan-merging mechanism. Abstracted feature subplans correspond to cases, which are used in subsequent planning operations to solve new problems. The abstracting and storing of feature subplans as cases is the primary mechanism by which the planner learns from its previous experiences to become more effective and efficient.     

A prototype of a feature-based multiple-alternative process planning system with scheduling verification

The primary objective of this research was to develop a prototype feature-based multiple-alternative process planning system in which the process plan would be generated directly from design and available factory facility information. An overall removable volume is generated by graphically comparing the 3D part and 3D workpiece blank. The manufacturing features are decomposed into a series of general manufacturing features by using a mixed graph-based and rule-based algorithm. The multiple-alternative process plan generation is based on recognized manufacturing features and various production rules. After generating multiple process plans, each process plan is allocated the possible manufacturing scheduling time and the candidate process plans are retrieved based on the required due day. An example problem is presented to illustrate the functionality of the prototype system. This research presents an alternative method that provides useful information to the factory planner and controller to facilitate production.     

Reuse machining knowledge for generating process plans of axisymmetric parts based on case-based reasoning

The basic idea of case-based reasoning (CBR) is to retrieve and modify the most relevant prior case to match new requirements. In this paper, a framework for a process planning system for machining of axisymmetric parts using case-based reasoning is introduced. It is composed of four major components: retriever, modifier, simulator, and repairer. When a desired axisymmetric part is to be machined, the proposed system first retrieves the most relevant case from the case library as a plan candidate. Since the plan candidate is rarely the same as the desired one, the system performs modification, simulation, and reparation on it. The proposed system has been implemented on a Sun workstation using the ACIS geometric modeler and C++.     

Systematic modeling and reusing of process knowledge for rapid process configuration

Rapid product development relies heavily on quick and reliable process planning and knowledge reuse. Process configuration borrows the principles of product configuration and applies them to process planning. It allows the reuse of hierarchical, historical and case-based manufacturing process knowledge to generate process plans efficiently and effectively. This paper presents a systematic knowledge model for manufacturing process cases. The model represents process knowledge at different levels of granularity and to facilitate process configuration. With this knowledge model the process knowledge is categorized into 6 levels: (i) core process skeletons, (ii) process networks, (iii) process routes, (iv) process segments, (v) processes/workplan, and (vi) operations/working step. Based on the systematic knowledge model, this paper also proposes an approach to achieve rapid process configuration by reusing the process knowledge and by performing the involved configuration rules so as to create an appropriate, reliable and effective process plan. The prototype for a graphical process planner based on this knowledge model is developed and an aerospace example is used to validate the proposed process knowledge model and process configuration.     

Design and implementation of a relational data base for automated process planning

The function of process planning in a manufacturing facility is to identify the processes and the machines required to convert a design into its final form. Majority of the process plans are still made manually. The degree of the process plan detail varies with the shop environment. A feature-based process planning system which interacts with the SDRC I-DEAS solid modeling software is presented. The system operates under the UNIX environment. A relational database model which incorporates manufacturing details including the operation selection, machine selection, tool selection, fixture selection, etc. was developed and implemented. This relational database was structured using Microsoft SQL SERVER for the PC multi-user environment. This database is part of an ongoing research project on automated process planning and scheduling and primarily focuses on prismatic parts. The developed routines generate the Overall Removable Volume (ORV) graphically by comparing the desirable design to the blank work piece. The routines then decompose the ORV into various General Manufacturing Features (GMF) based on concave edges. The recognition routine captures geometrical and topological information and identifies the shape of each GMF. An expert system (using CLIPS expert system shell) analyzes the GMFs and determines appropriate operation(s) for the designed part. The developed expert system is capable of recommending the suitable machines, tools, fixtures, etc.     

Integrated process planning using tool/process capabilities and heuristic search

CAD–CAM integration has involved either design with standard manufacturing features (feature-based design), or interpretation of a solid model based on a set of predetermined feature patterns (automatic feature recognition). Thus existing approaches are limited in application to predefined features, and also disregard the dynamic nature of the process and tool availability in the manufacturing shop floor. To overcome this problem, we develop a process oriented approach to design interpretation, and model the shape producing capabilities of the tools into tool classes. We then interpret the part by matching regions of it with the tool classes directly. In addition, there could be more than one way in which a part can be interpreted, and to obtain an optimal plan, it is necessary for an integrated computer aided process planning system to examine these alternatives. We develop a systematic search algorithm to generate the different interpretations, and a heuristic approach to sequence operations (set-ups/tools) for the features of the interpretations generated. The heuristic operation sequencing algorithm considers features and their manufacturing constraints (precedences) simultaneously, to optimally allocate set-ups and tools for the various features. The modules within the design interpretation and process planner are linked through an abstracted qualitative model of feature interactions. Such an abstract representation is convenient for geometric reasoning tasks associated with planning and design interpretation.     

基于本体映射的零件工艺实例重用方法研究*

针对目前计算机辅助工艺设计中基于实例的工艺相似性重用问题,提出一种基于本体映射的零件工艺实例重用方法。在分析零件工艺实例信息的基础上,建立了新零件工艺知识本体和零件库零件工艺实例本体。基于本体映射的方法,通过本体间相似度计算,完成新零件工艺实例的检索和重用,并以轴类零件来说明该方法的有效性。     

An automated coding and process planning system using a DEC PDP-10

A semi-generative system has been developed to perform automated process planning using DEC PDP-10 computer. The proposed Automated Coding and Process Selection (ACAPS) package makes use of Group Technology concepts to interactivity assign a code number to a part, generate a machining sequence, from part families, and specify operation details for a manufacturing route sheet. Primary consideration is given to rotational components, though others can be accommodated. ACAPS is designed to lead the planner step-by-step toward a complete process plan, with a minimum of confusion. The program could be adapted to any computer system having FORTRAN capabilities.     

On-line predictive model for disassembly process planning adaptation

This paper presents an on-line predictive model for disassembly process adaptation. The prediction enables a planner to adapt the process plan based on the condition of the product (e.g., degree of rustiness, deformation) during process execution. This model tries to correlate the product physical condition, used as an explanatory variable, with the component value and disassembly cost, the response variables. The core of the approach is based on an inference engine that used a kernel regression. A simple methodology for integrating the predictive planner in a disassembly system is presented and exemplified by a case study of the disassembly of a ratio.     

Interactive Case-Based Planning for Forest Fire Management

This paper describes an AI system for planning the first attack on a forest fire. This planning system is based on two major techniques, case-based reasoning, and constraint reasoning, and is part of a decision support system called CHARADE. CHARADE is aimed at supporting the user in the whole process of forest fire management. The novelty of the proposed approach is mainly due to the use of a local similarity metric for case-based reasoning and the integration with a constraint solver in charge of temporal reasoning.     

Feedback method from inspection to process plan based on feature mapping for aircraft structural parts

The feedback from results of computer aided inspection is used by process planners (though a manual process) to improve machining processes to achieve desired quality. Mapping from inspection features to machining features is a practical method to automate this process. In NC machining of aircraft structural parts, composite machining features, surface joining and complex topological adjacency between free-from surfaces make this kind of mapping (one-to-many mapping mostly) much more complicated. In this research, a new feature mapping based feedback method from inspection to process plan is proposed. The geometry of inspection features are categorized into three kinds of basic inspection elements: Axis, Plane, and Surface. Then, the one-to-many mapping is simplified into one-to-one mapping. The correspondence relationships between basic inspection elements and machining features are abstract as mapping rules to obtain the associations between the basic inspection elements and candidate machining features. Through geometric reasoning, the basic inspection elements are mapped into machining features. Then, the measure data as feedback can be transferred to process planner for improving machining process. The optimized machining process will be stored in knowledge base for reusing. A case study is presented in this paper to demonstrate the proposed method. A prototype feature-based on-line inspection system has been developed and applied for machining aircraft structural parts in a large aircraft manufacturer.     

Using mixed-type reasoning in computer-aided process planning for feature interactions

This paper describes a process-planning model using mixed-type reasoning designed for processing prismatic parts on CNC machine tools in a batch manufacturing environment. This mixed-type reasoning handles feature interactions by combining forward chaining for feature sequencing and backward chaining for the construction of a process plan. In such a model, the human problem-solving strategies are decoupled from the tools for analysis and sorting algorithms. Two databases are used to contain the results from forward and backward chaining. The process-planning algorithm combines the processes of modeling the given information in four stages: (1) defining the important information for features and feature-related concerns; (2) interpreting and rearranging the given feature according to the given constraints and sorting guideline; (3) sequencing the features; (4) attaching the needed operations to the features in machine/process/feature/set-up/tool/time/cost format.     

Planning in highly dynamic environments: an anytime approach for planning under time constraints

In this paper, we present a novel and domain-independent planner aimed at working in highly dynamic environments with time constraints. The planner follows the anytime principles: a first solution can be quickly computed and the quality of the final plan is improved as long as time is available. This way, the planner can provide either fast reactions or very good quality plans depending on the demands of the environment. As an on-line planner, it also offers important advantages: our planner allows the plan to start its execution before it is totally generated, unexpected events are efficiently tackled during execution, and sensing actions allow the acquisition of required information in partially observable domains. The planning algorithm is based on problem decomposition and relaxation techniques. The traditional relaxed planning graph has been adapted to this on-line framework by considering information about sensing actions and action costs. Results also show that our planner is competitive with other top-performing classical planners.     

OOPPS: an object-oriented process planning system

This paper presents an object-oriented approach to the development of a generative process planning system—Object-Oriented Process Planning Systems (OOPPS). The system consists of three functional modules: object-oriented product model (OOPM) module, object-oriented manufacturing facility model (OOMFM) module, and object-oriented process planner (OOPP). The OOPM has a hierarchical structure with six classes of objects, class Products, class SubAssembly, class Part, class CSGTree, class Solid and class Feature. It can represent a product with all detailed information. The OOMFM is used to represent a cellular manufacturing system including machine cells, machine tools fixtures, and cutting tools. The OOPP generates process plans for parts using a multi-level hierarchical planning approach with four levels: cell-level planning, machine-level planning, fixture-level planning and tool-level planning. At the cell-level, all required operations are determined based on the feature specifications. Machine cells are then selected, based on the selected operations, for the minimal inter-cell movement. The machine-level planning selects the machines within the chosen cells. The fixtures are also selected on the selected machines. At the fixture-level planning, part setups and their sequences are selected. Finally, the tool-level planning determines all details for the process plans. An automated progamming system was also developed to link the OOPP to Smart CAM to generate CNC programs. An example has been used to illustrate the approach.     

Applying a path planner based on RRT to cooperative multirobot box-pushing

Considering robot systems in the real world, a multirobot system where multiple robots work simultaneously without colliding with each other is more practical than a single-robot system where only one robot works. Therefore, solving the path-planning problem in a multirobot system is very important. In this study, we developed a path-planner based on the rapidly exploring random tree (RRT), which is a data structure and algorithm designed for efficiently searching for multirobot box-pushing, and made experiments in real environments. A path planner must construct a plan which avoids the robot colliding with obstacles or with other robots. Moreover, in some cases, a robot must collaborate with other robots to transport the box without colliding with any obstacles. Our proposed path planner constructs a box-transportation plan and the path plans of each robot bearing the above considerations in mind. Experimental results showed that our proposed planner can construct a multirobot box-pushing plan without colliding with obstacles, and that the robots can execute tasks according to the plan in real environments. We also checked that multiple robots can perform problem tasks when only one robot could not transport the box to the goal. This work was presented in part at the 13th International Symposium on Articifial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

CBIMS: Case-based impeller machining strategy support system

Impeller machining strategies cannot be easily formalized due to the complex, overlapping and twisted shapes that form impeller blades. Skilful machining process planners may generate appropriate machining strategies based on their experiences and previous machining data. However, in practice, most shop floor data for impeller machining is not well-structured and it cannot be used effectively by process planners to produce the required machining strategies and process plans. This paper presents the development of a case-based impeller machining strategy support system (CBIMS) that employs case-based reasoning (CBR) to obtain an efficient machining strategy for an impeller by using the existing machining strategies from the shop floor. The CBIMS generates impeller machining strategies through a stepwise reasoning process considering the similarities of the blade shapes and machining regions between existing impellers and a new one. The system can provide a process planner with machining strategies such as tool specifications, machining area partitioning, and the machining parameters including feed rate, depth of cut, RPM and machining tolerance. A case study is provided to demonstrate that the CBIMS can generate useful machining strategies while ensuring that it can be effectively used to support the process planner.     

RALPH static planner: CAD-based manipulator assembly task planning for CSG-modeled objects

This article describes a manipulator assembly task planner that processes the knowledge of the working environment and generates a sequence of general, manipulator independent commands. the planner takes a very high level command, such as “insert PEG into HOLE” without further specifications, reasons about the involved object features using the information from the CAD system, and generates a process plan for the manipulator to automatically perform the task. In this planner, the grasp planning and the path planning are developed and implemented for a static world.     

Developing an energy-saving and case-based reasoning information agent with Web service and ontology techniques

Web service and ontology techniques are presented herein for supporting an energy-saving and case-based reasoning information agent. The proposed system is the first energy-saving and case-based reasoning information agent with Web service and ontology techniques in a cloud environment; the proposed architecture is also the first multi-agent structure of an energy-saving information system in a practical environment. Not only can it explore related technologies to establish a Web service platform, but it can also study how to construct cloud interactive diagrams to employ Web service techniques for extensively and seamlessly integrating energy-saving and a case-based reasoning information agent on the Internet. The complete in depth system development, display, and corresponding experiments and comparisons show that the research results not only attest to the feasibility of the proposed architecture, but are also highly successful; on average, 40% of the data queries can be answered by the proposed system, and its rate of correct data solutions is around 85.1%, leaving about 60% of the queries for the backend system to take care of, which can effectively alleviate the overloading problem usually associated with a backend server. Finally, the system is put into a practical environment; after 8 months of experiments, the total energy-saving is 22.44%.     

A STEP-compliant process planning system for CNC turning operations

Over the last 50 years, there have been many significant enhancements in computer aided systems which have influenced the CNC technology. One area that can be considered as a bottleneck to these CNC enhancements, and in particular to interoperability in CNC manufacturing is G&M part programming (ISO 6983). To overcome this bottleneck, the new standard ISO 14649, known as STEP-NC, is being developed to provide detailed information on component design, process planning and machining strategies to manufacture parts for the next generation of intelligent CNCs. This standard forms the basis of a new paradigm shift in the CNC domain to support digital modelling of CNC manufacturing resources. The research in this paper aims to identify major issues and develop new software tools to demonstrate the feasibility of interoperable CNC manufacturing based on STEP-NC. Besides the literature review on recent research and development on STEP-NC, this paper proposes a Process Planning System (PPS) with surface roughness chosen as the process planning objective. PPS consists of five modules: program reader, process planner, STEP-NC CAD viewer, STEP-NC CAM viewer and program writer. The reader is responsible for interpreting the geometry and the manufacturing data from a STEP-NC text file into a stored data list. The process planner uses this data list and enables users to evaluate surface roughness based on a mathematical model. Through the STEP-NC CAD viewer, the part geometry can be shown and via the STEP-NC CAM viewer the toolpath can be verified. Finally, the writer converts the stored STEP-NC data of the system into an updated STEP-NC file. An example case study component is used to demonstrate the PPS and show the interfacing of the STEP-NC data.