畢業(yè)設(shè)計（外文翻譯）Virtual engineering: an integrated approach to agile manufacturing machinery design and controlP.R. Moore,J.Pu, H.C. Ng, C.B. Wong , S.K. Chong ,X. Chen , J. Adolfsson , P. Olofsgard , J.-O. LundgrenAbstractA virtual manufacturing approach for designing, programming, testing, verifying and deploying control systems for agile modular manufacturing machinery are proposed in this paper. It introduces the concepts, operations, mechanisms and implementation techniques for integrating simulation environments and distributed control system environments so that the control logic programs that have been programmed and veri?ed in the virtual environment can be seamlessly transferred to the distributed control system environment for controlling the real devices. The approach looks to exploit simulation in a much wider range of applications with great advantages in the design and development of manufacturing machine systems. In particular, it facilitates the veri?cation of the runtime support applications using the simulation model before they are applied to the real system. Mechanisms that allow runtime data to be collected during operation of the real machinery to calibrate the simulation models are also proposed. The system implemented delivers a powerful set of software tools for realising agile modular manufacturing systems. 1. IntroductionAgility is widely recognised as one of the most important attributes for manufacturing systems to satisfy the needs of competitive global markets, which are resulting in the need to produce high quality products at low cost with shortening product lives and ever increasing demands for differentiation through customisation[1]. By agility, it can mean that manufacturing systems have to respond to production changes both in volume and variety rapidly, effectively and reliably with low cost. Virtual manufacturing (VM) and virtual engineering have been identi?ed as one of the enabling technologies of agile manufacturing and its related activities [2,3].One de?nition of virtual manufacturing is ‘‘to carry out manufacturing activities with a simulation model of the actual setup, which may or may not exist. It holds all the information relating to the process, the process control and management and product speci?c data. It is also possible to have part of the manufacturing plant be real and the other part virtual’’ [4]. From such a de?nition, it can be inferred that integration of simulation models with process control and management data and possibly with the real system itself is an essential ingredient within such an approach. In the manufacturing sector, simulation packages with three-dimensional modelling and animation capabilities (referred to as 3-D simulation hereafter) are progressively gaining favour. The visualisation capability provided by 3-D simulation packages not only provides much richer, closer-to-reality information for users, but also enables new application domains to be addressed such as rapid prototyping of machine systems. One 畢業(yè)設(shè)計（外文翻譯）example of 3-D simulation is computer aided robotic (CAR)systems [5], which are often utilised for the design and programming of industrialrobot based workcells. Such systems provide facilities for evaluating different cell con?gurations and layouts by allowing the users to choose diifferent robot models from a model library. Moreover, the same environment can be used for off-line programming robots through code generation, thereby shortening system development time, according to experience gained in the European automotive industry (e.g.Volvo, SAAB, etc.), where continuous 3-D simulation tools are used extensively to prepare programs for robot workcells. It should be recognised that the substantial cost of such software packages and the considerable expertise required in building useful models, requires a considered commitment to the use of such tools. However,the most appealing attraction for manufacturers to use CAR systems is that programming and testing stage can commence very early once an order is received,enabling reduced lead-times without disrupting production systems on the shop ?oor. Such orders may arise from the introduction of new equipment, new product types, and/or changes in production volume, etc. In other words, simulation plays a signi?cant role in bringing systems into operation more rapidly and more reliably because more testing and veri?cation can be done earlier in the life cycle in a safeenvironment.Automatic code generation is highly desirable by translating simulation programs to machine control code. However, such a feature is only generally available for conventional and standard machinery such as CNC machines and industrial robots.A general solution for designing and off-line programming special purpose manufacturing machinery is not currently available. Such machine systems are typically built from customisable modular automation equipment that is con?gured from modular components such as sensors, actuators and motion controllers, etc., which are supplied by multiple vendors and typically operate within heterogeneous platforms. In most cases, when graphical simulation has been applied during the design process, this implies that control engineers have to re-implement the control logic described in a simulation model when developing the software for the real control system. Mis-interpretation and sub-optimal implementation can be the result of such a discontinuity in the process [6]. Such shortfalls can also lengthen delivery times and diminish the intended bene?ts from applying simulation.This paper proposes a highly integrated approach to machine system development, whereby design, simulation and distributed control are facilitated. In particular, it focuses on the concepts and implementation techniques for integrating simulation environments and distributed control system environments so that control logic programs that have been designed, tested and veri?ed in the simulation environment can be ‘‘seamlessly’’ transferred to the distributed control system environment for operations of real devices. The proposed approach looks to exploit simulation in a much wider range of applications with signi?cant bene?ts in the design and development of manufacturing machine systems. To this end a number of integration mechanisms are facilitated in supporting processes in a typical machine design and development life cycle. These include: (i) exchanging the control requirement/design information between simulation and the control system design environment; (ii) control logic program transfer from simulation to the distributed control of real devices; (iii) runtime support application veri?cation using simulation; and (iv) 畢業(yè)設(shè)計（外文翻譯）collection of runtime data to calibrate simulation models. Such an integrated approach has been successfully applied to the design and development of real industrial demonstrator cell for assembly of cylinder-head valves, within an installation at Euromation (a Volvo group company), Sweden.The research described in this paper is based on the outcome of a major European Commission funded project VIR-ENG. A brief introduction to this research project is given in the following section. The paper is organised as follows, Sections 3 and 4 introduce the key elements of the proposed approach; integration mechanisms and their implementation are addressed in Section 5; Section 6 brie?y summaries successful application examples of the approach.2. VIR-ENGThe concepts and corresponding tools addressing machine systems design presented in this paper were ?rst devised and implemented in the European Commission Framework IV ESPRIT research project ‘‘Integrated Design, Simulation and Distributed Control of Agile Modular Manufacturing Machine Systems’’ (VIR-ENG),which concluded successfully in June 2001. The project objective was to develop highly integrated design, simulation and distributed control environments for building agile modular manufacturing machine systems which offer the inherent capacity to allow rapid response to product model changes and feature variants [7]. Fig. 1 illustrates the organisation of the project and the associated work packages and their inter-relationships. Among these work-packages, the modular machine design environment (MMDE) and the distributed control system environment (DCSE) are the two major environments that support different facets in the machine system life cycle. Although VIR-ENG has identi?ed two distinctive environments, the end-user will not necessarily see two separate environments at all and will employ both as a seamless whole.2.1. VIR-ENG manufacturing machine system modelIn VIR-ENG, a four-layer manufacturing machine system model is devised to serve as a reference model for both MMDE and DCSE to ensure integrity in analysis, design and implementation in building machines and their associated control systems. The four layers in the model are illustrated in Fig. 2.2.2. MMDE––the design and simulation environmentThe MMDE supports the design/virtual engineering of the physical elements and control logic of component-based manufacturing machine systems. From the viewpoint of end users, MMDE consists of two major environments: (i) the design/simulation environment and (ii) the programming environment. These environments together with a number of specialist tools, constitute the MMDE. The simulation environment in MMDE is where virtual models of the machine system are produced,tested and evaluated. The programming environment of MMDE provides the programming interface that allows users to de?ne the control logic for driving the virtual machine system. One of the unique features introduced by VIR-ENG, the control logic to drive the simulation entities is described using programming languages de?ned in IEC1131 Part 3 (IEC1131-3) [8]. Further description of 畢業(yè)設(shè)計（外文翻譯）MMDE can be found in Refs. [9,10].CSDE provides the tool-set to comprehensively support the activities in the design and development of control systems. These include tools for users, particularly electrical and control engineers to: (i) design and specify the control architecture using standard UML notation [11]; (ii) generate the machine/machine system control components based on the control logic that are de?ned and veri?ed in MMDE; (iii) mechanisms for mapping the interfaces of control components to corresponding ?eld devices; and (iv) recon?gure or modify existing control systems. CSDE tools can be further structured into two major tool-sets; namely, (i) control architecture design environment (CADE), and (ii) control system programming environment (CSPE). DRE provides a framework and associated runtime support component library for creating network-enabled runtime support applications for machine systems. DRE-developed runtime support are featured with distributed human machine interfaces (HMI) with embedded functionality including con?guration and monitoring, alarm handling, diagnostics and maintenance for supporting the operation of the manufacturing machine system and associated production facilities.All VIR-ENG environments are designed and implemented to support and encourage reusability of machine components (hardware/software). In particular, the underlying information infrastructure (IIS) delivers a component library, which serves as a structured repository for components designed in VIR-ENG environments. The IIS also provides a component manager for users to manage the components in the library. Furthermore, the CDE within the DCSE de?nes theunderlying reference model for supporting the activities in CSDE and DRE.Since VIR-ENG has introduced a number of important concepts addressing a wide range of machine system developments, a detailed review of the project and individual environments is beyond the scope of this paper. The paper goes on to focus on the integration between MMDE, CSDE and DRE, which provides a reference for integrating simulation and distributed control design and operating environments. It is important to point out that, even though the concepts andimplementation techniques presented were ?rst devised and applied in VIR-ENG, the authors believe that they can be more generally applied in integrating simulation environments and distributed control environments without necessarily conforming to the overall speci?c architecture described here. Nevertheless, for the sake of brevity and clarity, the acronyms adopted within VIR-ENG will be used throughout the paper. Conceptually, the readers may generally relate MMDE to the design and simulation environment that produces the simulation model of the machine system; CSDE to the design environment that generates the control software components for real devices; DRE to the design environment that produces the runtime support applications for machine systems.3. Elements for integration in machine system designFig. 3 illustrates the key elements in each environment and the process associated with integration of simulation and distributed control. Each element of the approach is described in this section before considering the integration process in Section 4.畢業(yè)設(shè)計（外文翻譯）3.1. Simulation modelsAs the key output of MMDE, simulation models refer to the 3-D graphical simulation models that encapsulate information such as: (i) list of machine components and their CAD models; (ii) machine layout; (iii) kinematics properties (e.g.maximum allowable velocity); (iv) kinematics relationships; (v) application task logic (e.g. sequence, timing and synchronisation), etc.3.2. Control architecture speci?cationsControl architecture speci?cations are the major output of the CSDE, which contain important information that must be referenced by all three environments for the remaining phases of the machine design and development process. Such speci?cations, represented using UML-based diagrams and data tables, specify the following information:? A list of control components, and their inter-relationships––this is the result of decomposing the system using methodologies based on task decomposition and a components, responsibilities and collaborations (CRC) method.? Speci?cations of the control component interfaces. These provide detailed information about the types and data semantics for each interface item of the control components.? Speci?cations of the control component services, which de?ne the required functionality.? Speci?cations for exception handling.The control speci?cation forms the basis for developing the control logic programs in the MMDE to drive the simulation model. The de?ned speci?cation also acts as a contractual agreement covering DRE requirements, which allows the runtime support/HMI developed in the DRE to be veri?ed using the simulation model developed in MMDE. In summary, the control architecture speci?cation is the core mechanism for integration of MMDE, CSDE and DRE.3.3. Control logic programsControl logic programs refer to the programs that specify the behaviour of individual machine components and their interactions. As a unique feature of the proposed solution, control logic for the virtual machines is described using IEC1131-3 programs rather than any native simulation language. Therefore, control logic programs exist in the form of program organisation units (POUs) de?ned in IEC1131-3, which may include programming constructs like function blocks and functions that support the development of well-structured programs and reuse of code. In order to facilitate the use of the same control logic programs to drive both the virtual machines and the real machines, three concepts are introduced, namely:(i) Virtual I/O––Communication between the control logic programs and the simulation is accomplished by exchanging data synchronously through a shared data block. In order to facilitate the seamless program transfer, the data to be exchanged (e.g. control signals and virtual device status) should resemble the I/O of the real system. The data block and its corresponding mechanism is thus termed virtual I/O . Other simulation-speci?c data such as the simulation clock time is also updated to the virtual I/O when the simulation is executing.畢業(yè)設(shè)計（外文翻譯）(ii) Virtual component controllers––These are a set of generic software units that control the objects in the simulation which are developed using the native simulation languages. Having close association with virtual I/O, they are responsible for reading data from the shared data block and then generate the corresponding state change and graphical update. They also update the virtual I/O with the current status of the simulated machines.(iii) Motion function blocks (FBs)––A list of user-de?ned IEC1131-3 FBs have been de?ned for representing the motions required by machine designers. These blocks possess the same meaning across both MMDE and CSDE. The effect of such blocks produced on the virtual model should be reproduced in the real control system designed in CSDE. However, contrary to other POUs, the actual implementations of the same block within the two environments are different,only the interfaces of the motion FBs are agreed across the environments. While the FB in MMDE contains the code to drive the virtual actuators, the same block in the CSDE encapsulates the code to generate the motion of the real device. Such a concept can also be applied generally to hide complexity behind interfaces to control any complex machinery. For example, two FBs are designed for controlling the AGV in the VIR-ENG demonstrator (see Section 6).In ideal cases, the same control logic programs developed to drive the virtual models can be transferred seamlessly to drive the real machines/devices with only minimal modi?cation to re-map the interfaces from virtual I/O to real I/O. Nevertheless, it can be appreciated that in practice not all physical aspects can be considered in the virtual environment. Certain additional information may be needed when creating the control logic components for real machine systems. These could include:? Hardware-speci?c initialisation: Most control devices require certain initialisation routines to be executed before operation. Such initialisation logic has not usually considered in the simulation environment and therefore needs to be speci?ed in the CSDE.? Exception handling: Some exceptions like sensor failure can be injected into the simulation model in order to test the control logic in handling such errors. Nevertheless, there exist some types of failure mode (e.g. timing related) that are largely impractical to test in the virtual environment. Extra exception handling logic has to be added to contend with these issues.It should be emphasised that such modi?cations involve only supplementary code and do not invalidate the original logic generated in the virtual environment. It should also be appreciated that much of the exception handling logic can be generated and validated in the virtual environment.3.4. Runtime support and runtime dataAs mentioned earlier, DRE-developed runtime support features a distributed HMI with embedded functionality such as con?guration and monitoring, alarm handling, diagnostics and maintenance, for supporting production related activities. Runtime data refers to data that is collected by the monitoring and logging functions of the runtime support from the real machine system in operation. Depending on the runtime support design, this data might include ‘‘raw’’ data from the machinery (e.g. analogue sensor readings) and/or ‘‘high-level’’ production data/information.畢業(yè)設(shè)計（外文翻譯）4. Processes within the integrated approachWith reference to Fig. 3, the integration process typically starts by transferring the simulation models, which describe the mechanical design/layout, kinematics properties, kinematics relationships and application task logic to the CSDE as the blueprint for the control system design process. In return, the control archit