Chengyin Yuan

Sequence Planning for Integrated Product, Process and Automation Design

In order to obtain a unified information flow from early product design to final production, an integrated framework for product, process and automation design is presented. The framework is based on sequences of operations and includes a formal relation between product properties and process operations. This relation includes liaisons (interfaces) and precedence relations, where the precedence relations generate preconditions for the related process operations. From this information a set of sequences of operations (SOPs) is generated. A formal graphical language for hierarchical operations and SOPs is then introduced and defined based on automata extended with variables. Since the operations are self-contained they can be grouped and viewed from different angles, e.g., from a product or a resource perspective. These multiple views increase the interoperability between different engineering disciplines. A case study is performed on a car manufacturing cell, where the suggested modeling framework is shown to give comprehensible SOPs.

Sequence Planning Using Multiple and Coordinated Sequences of Operations

The sequential behavior of a manufacturing system results from several constraints introduced during the product, manufacturing, and control logic development. This paper proposes methods and algorithms for automatically representing and visualizing this behavior from various perspectives throughout the development process. A new sequence planning approach is introduced that uses self-contained operations to model the activities and execution constraints. These operations can be represented and visualized from multiple perspectives using a graphical and formal language called Sequences of Operations (SOPs). The operations in a manufacturing system are related to each other in various ways, due to execution constraints expressed by operation pre- and post-conditions. These operation relations include parallel, sequence, arbitrary order, alternative, and hierarchy relations. Based on the SOP language, these relations are identified and visualized in various SOPs and sequences. A software tool, Sequence Planner, has been developed, for organizing the operations into SOPs that visualize only relevant operations and relations.

From Hardware-in-the-Loop to Hybrid Process Simulation: An Ontology for the Implementation Phase of a Manufacturing System

Hardware-in-the-loop (HIL) is a widely used testing approach for embedded systems, where real components and/or controllers are tested in closed-loop with a simulation model. In this paper, we generalize HIL by combining multiple simulations and real components into a Hybrid Process Simulation (HPS). An HPS is a test setup that contains at least one simulated and one actual component, but may contain many of both. It is implemented such that each simulated component can be swapped out with its real counterpart without making changes to the existing system, and vice versa. In this paper, an ontology which provides a conceptual architecture is developed for an HPS, such that a general interpretation of a manufacturing systems implementation is made possible. A formalized application method is then devised for replacing simulations with real processes and vice versa. A conceptual architecture is put forth that separates the effect of a component from its spatial essence (volume or mass). This separation allows workpieces in a manufacturing process, for example, to go from the physical world into the virtual world (computer simulation) and back again repeatedly. The conceptual architecture is applied to a small manufacturing line in the following scenarios: replacing a real robot with a simulated robot, replacing a manufacturing cell with a simulated manufacturing cell, and adding a new simulated manufacturing cell to the existing system. These applications successfully demonstrate how an HPS can be used to test a manufacturing system setup with multiple regions of real and simulated components.

Formal Specification and Verification of Industrial Control Logic Components

Component-based programming frameworks for industrial control logic development promise to shorten development and modification times, and to reduce programming errors. To get these benefits, it is, however, important that the components are specified and verified to work properly. This work introduces Reusable Automation Components (RACs), which contain not only the implementation details but also a formal specification defining the correct use and behaviour of the component. This formal specification uses temporal logic to describe time-related properties and has a special structure developed to meet industrial control needs. The RAC can be formally verified, to determine whether the implementation fulfils the specification or not. A RAC prototype development tool has been developed to demonstrate this capability. The main difference between the RAC and other frameworks for formal verification of control logic is the specification modeling. In RAC, not only the implementation but also the specification is based on the structure and languages of conventional control logic, aiming at being easy to comprehend for control logic engineers. Several industrial examples are discussed in this paper, showing the benefits and potential of the framework.

A formal specification language for PLC-based control logic

Formal verification, using model checking tools, is promising in developing (IEC 61131) industrial control logic. Formal verification requires a formal specification of the properties to be verified. Specifications in model checking tools are typically expressed using temporal logic. However, the standard temporal logic dialects are not well suited for control engineers who do rarely have a background within computer science. In this paper a new dialect of linear temporal logic, ST-LTL, is introduced that intends to be easier to use for control engineers than the existing dialects. The relation of ST-LTL compared to existing temporal logic dialects is analyzed.

The Origin of Operations: Interactions Between the Product and the Manufacturing Automation Control System

This paper investigates the interaction and relationship between the product design and the control logic design for manufacturing automation system. One important challenge during the development of a manufacturing automation system, is to handle the information related to the manufacturing control system (i.e PLC), since it influences almost every part of the manufacturing design and process. Therefore it is crucial to know when and how this information is created, to be able to increase the development quality and efficiency. This is especially true for the product related information that impacts the design of the control system. This paper studies the liaisons, the interfaces among parts and features in the product design, and its relationship with operations and resources in the manufacturing system. These liaisons must be considered in both product and manufacturing development since the inter-relation between liaisons and operations establishes the direct mapping of constraints and demands between the two domains. This paper further proposes how the manufacturing operations can be described during the development and how they are realized by resources in the manufacturing system. An example from automotive industry is included in this paper, to demonstrate the proposed concept.

EMBench: A Rapid Prototyping Environment for Numerical Control Systems

In this paper we describe an environment for performing both mechanical and control design for flexible automation systems. The environment provides a means of layering and encapsulating services so that complex multi-axis numerical control systems can be configured, detailed electromechanical simulations performed and then deployed. The system uses IEC-61499 as a means for modularization and reuse of implemented control services. Using IEC-61499 function blocks and a service-layer architecture, control services ranging for basic servoing of a joint, to kinematic co-ordination of joints of a mechanism, to trajectory interpolation, to language parsing and HMI processing, can be configured for an application. The environment facilitates a modular, component-based design of services for numerical control systems.Copyright

An integrated rapid prototyping environment for reconfigurable manufacturing systems

At the enterprise level, manufacturing organizations are faced with accelerating technological cycles, global competition and an increasingly mobile work force. The flexibility of an enterprise and its ability to respond to new customer demands governs the competitiveness of the enterprise to changes in its market and in the society in which it operates. The flexibility in production processes must be able to accommodate differing product mixes with the changing availability of a skilled work force. It has been recognized for many years that flexibility on the enterprise shop floor can always be achieved if the resulting cost of product, process and system changeovers are not considered. However, with the increasing competitive pressures on today’s manufacturing enterprise; a highly flexible and reconfigurable manufacturing environment must be achieved at relatively low cost and high work-force productivity while maintaining a competitive advantage. To accomplish this goal the manufacturing enterprise must be able to be reconfigured with an increased level of automation that is scalable and flexible to meet diverse product demands. In this paper, we will introduce EMBench as the design and simulation environment for reconfigurable manufacturing systems. This environment provides a universal GUI (Graphical User Interface) that allows user to design, configure and simulate various resources on the shop floor level. In this paper, we present the resource model, workstation model and cell model and explore their characteristics and behaviors. We also propose the general interface for different models using IEC-61499 function blocks that allow scalable expansion and modular design. We use IEC-61499 function blocks and a service layer architecture to integrate various resources on the enterprise shop floor and achieve flexibility at a low cost. This environment facilitates a modular, component-based design of services for enterprise shop floor control.Copyright

Towards Industrial Formal Specification of Programmable Safety Systems

Formal methods for specification and verification are promising in developing programmable logic controller (PLC) programs in manufacturing industry. Particularly this holds for safety PLCs, used to protect humans and equipment from injuries and damages. An important challenge though, is the development of formal specifications, typically a tough task for control engineers. This brief proposes a systematic work procedure that can be used as a first step of developing formal specifications of safety PLC programs in industry. The work procedure intends to facilitate the development of relevant formal properties for safety PLC program components. The formal specifications can be used for automatic formal verification of the components, using model checking techniques. This brief shows how the work procedure has been applied to industrial safety components, resulting in relevant and nontrivial specifications.

An Integrated Environment for the Design and Control of Deadlock-Free Flexible Manufacturing Cells

At the enterprise level, manufacturing organizations are faced with accelerating technological cycles, global competition and an increasingly mobile work force. The flexibility of the enterprise and its ability to respond to various customer demands governs the competitiveness of the enterprise to the changes in its market and in the society in which it operates. It has been recognized for many years that flexibility on the enterprise floor can always be achieved if the resulting cost of product and process changeovers and its operations are not considered. However, with the increasing competitive pressures on today’s manufacturing enterprise, a flexible-manufacturing environment must be achieved at relatively low cost and high work-force productivity while maintaining a competitive advantage. To accomplish this goal, the manufacturing enterprise must be able to be reconfigured and verified with an increased level of automation that is scalable and flexible to meet diverse product demands quickly and economically. In this paper, we will introduce the recent research work on developing an integrated rapid prototyping environment, EMBench [22, 23], which can provide design, control configuration, simulation and deployment services for flexible manufacturing systems. This rapid prototyping environment has its own user-friendly GUI (Graphical User Interface) that allows user to issue various commands to the controller at different layers, from the simple joint servo to the complex manufacturing cell. In this paper, we also propose the implementation diagram for the controller of manufacturing cells that consists of scheduler, dispatcher, real-time database and structural control policy. All these internal components are responsible for storing system configuration, optimizing processing plan, releasing appropriate command, etc. We also present the idea of cell model and explore its characteristics and behaviors as well as the resource and workstation models. All above modules and architecture are developed using IEC-61499 function blocks that support scalable expansion and modular design. To demonstrate our theoretical achievements, we have developed various IEC-61499 function blocks to integrate various resources on the enterprise shop floor and achieve flexibility at a low cost. This software environment facilitates a modular, component-based mechanical and control design, simulating and prototyping tool for shop floor control.© 2004 ASME