Manufacturing Cell Control Research Articles

Design and Development of a Flexible Manufacturing Cell Controller Using an Open-Source Communication Protocol for Interoperability

Flexible manufacturing cells provide significant advantages in low-volume mass-customization production but also induce added complexity and technical challenges in terms of integration, control, and extensibility. The variety of closed-source industrial protocols, the heterogeneous equipment, and the product’s manufacturing specifications are main points of consideration in the development of such a system. This study aims to describe the approach, from concept to implementation, for the development of the controller for a flexible manufacturing cell consisting of heterogeneous equipment in terms of functions and communication interfaces. Emphasis is put on the considerations and challenges for effective integration, extensibility, and interoperability. Scheduling and monitoring performed by the developed controller are demonstrated for a manufacturing cell producing microfluidic devices (bioMEMS) that consists of six workstations and a robot-based handling system. Communication between the system controller and the workstations was based on open-source technologies instead of proprietary software and protocols, to support interoperability and, to a considerable extent, code reusability.

Architecture of a flexible manufacturing cell control application

Architecture of a flexible manufacturing cell control application

Design and Implementation of Voice Control System in Flexible Manufacturing Cell

On the voice development platform of Microsoft Speech SDK, speech recognition and speech synthesis modules based on command control mode is built in this paper. Ethernet-based remote voice control system of intelligent flexible manufacturing cell is developed for machine tools and industrial robots. This paper designs an intelligent voice control system based on LabVIEW development environment, which realizes the human-machine voice interaction of flexible manufacturing cell and remote voice control. Experimental studies have shown that intelligent voice control system has high speech recognition rate and system reliability in a relatively quiet environment.

The Research on Modeling of Agile Manufacturing Cell

According to the characteristic of agile manufacturing cell, a modeling method based on multi-agent is proposed. It strengthens rules on the basis of oriented-object method. An agent method of agile manufacturing cell management and control system is established.

Generation of restart states for manufacturing cell controllers

A method for restart of manufacturing systems has recently been introduced. After correction of a fault, the system resumes normal production by returning to a certain restart state in the control function, and from there reexecuting parts of the work schedule. The current paper concerns automatic generation of the restart states, using discrete event systems theory. The generation process finds all possible restart states that guarantee that the execution restrictions are fulfilled during a restart, and that the production goals can be maintained. The number of restart states is minimized to reduce the number of necessary extensions to the control program.

Model Based Design and Implementation of Hierarchical and Distributed Control for Robotic Flexible Manufacturing System Cells Using Petri Nets

This paper deals with the modeling and control of discrete event robotic manufacturing cells using Petri nets, and proposes a methodology of model based design and implementation of hierarchical and distributed control. Hierarchical Petri net models are adopted; conceptual Petri net model and detailed Petri net model. The overall detailed Petri net model is decomposed into local Petri net models which are used by the local machine controllers. The upper level station controller coordinates the distributed local controllers so that the aggregate behavior of decomposed subnets is the same as that of the original Petri net. The overall control system is implemented using multithreaded programming based on Petri net based multitask processing. Simulation experiments show that the distributed Petri net model based control system can perform the overall multitask processing control by coincidence of the behavior of the real system with the local Petri net models.

Coordination of Operations by Relation Extraction for Manufacturing Cell Controllers

A method for generation of the control function for flexible manufacturing cells is presented in this paper. The control function is separated from the rest of the programmable logic control (PLC) program, and partitioned into a high-level part handling the operation sequence and a low-level part defining the execution process of the operations. The program structure enables high-level supervisor synthesis, which alleviates the state-space explosion problem. Information present in earlier steps of the development process is reused and processed, to automatically generate the automata needed for supervisor synthesis. An algorithm for generating automata, from the low-level safety requirements that restrict the high-level behavior, is presented. Algorithms are also presented for extracting the relations between the operations defining the work in the cell, from the synthesized supervisor. These relations give an easy-to-read representation of the control function that makes it interpretable by machine operators and maintenance personnel, an important feature to make the method applicable in an industrial setting. Hence, the control function generated by our method combines the benefits of a traditional supervisor, namely optimality and flexibility, with simplicity and clarity.

Synthesis of Restart States for Manufacturing Cell Controllers

In earlier work we presented a method for restart of manufacturing systems. After correction of an error, the system resumes normal production by returning to a certain restart state in the control function, and from there reexecuting parts of the work schedule. The current paper concerns automatically finding ( synthesizing ) the restart states. The control function is modeled by finite automata, and properties of the restart states are defined. The synthesis process finds all possible restart states, guaranteeing that the execution restrictions are fulfilled during a restart, and that the production goals can be maintained. The error and the corrective actions preceding the restart need not be modeled; neither is it necessary to know the exact physical states of the machines at the time of the error. The number of restart states is finally minimized to reduce the need for extensions to the control program.

Design and control of agile automated CONWIP production lines

AbstractIn this article, we study the design and control of manufacturing cells with a mix of manual and automated equipment, operating under a CONWIP pull protocol, and staffed by a single agile (cross‐trained) worker. For a three‐station line with one automated station, we fully characterize the structure of the optimal control policy for the worker and show that it is a static priority policy. Using analytical models and extensive simulation experiments, we also evaluate the effectiveness of practical heuristic control policies and provide managerial insights on automation configuration design of the line. This characterization of the worker control policy enables us to develop managerial insights into the design issues of how best to locate and concentrate automation in the line. Finally, we show that, in addition to ease of control and greater design flexibility, the CONWIP protocol also offers higher efficiency and robustness than does the push protocol. © 2008 Wiley Periodicals, Inc. Naval Research Logistics 2009

Modular finite state machines: Development and application to reconfigurable manufacturing cell controller generation

This paper presents a new framework developed for logic control of manufacturing systems based on finite state machines (FSMs) and a method to automatically generate the control logic for manufacturing cell controllers using this framework. The framework is modular; FSMs are encapsulated into modules with well-defined communication between them. Events in the finite state machines are of two types, triggers and responses, allowing FSMs to react to events and to force events to occur. The automatic generation method is based on a library of predefined modules. Its application to and implementation on a manufacturing testbed is described.

Deadlock-free scheduling and control of flexible manufacturing cells using automata theory

This paper presents a novel method for the scheduling and control of flexible manufacturing cells (FMCs). The approach employs automata, augmented by time labels proposed herein, for the modeling of machines, transportation devices, buffers, precedence constraints, and part routes. Ramadge-Wonham's supervisory-control theory is then used to synthesize a deadlock-free controller that is also capable of keeping track of time. For a given set of parts to be processed by the cell, A/sup */ search algorithm is subsequently employed using a proposed heuristic function. Three different production configurations are considered: Case 1) each part has a unique route; Case 2) parts may have multiple routes, but same devices in each route; and Case 3) parts may have multiple routes with different devices. The proposed approach yields optimal deadlock-free schedules for the first two cases. For Case 3, our simulations have yielded effective solutions but in practice, optimal deadlock-free schedules may not be obtainable without sacrificing computational time efficiency. One such nontime-efficient method is included in this paper. The proposed approach is illustrated through three typical manufacturing-cell simulation examples; the first adopted from a Petri-net-based scheduling paper, the second adopted from a mathematical-programming-based scheduling paper, and the third, a new example that deals with a more complex FMC scenario where parts have multiple routes for their production. These and other simulations clearly demonstrate the effectiveness of the proposed automata-based scheduling methodology.

On-line scheduling and control of flexible manufacturing cells using automata theory

An effective flexible-manufacturing-cell (FMC) controller can be synthesized using classical automata and Ramadge–Wonham (R–W) supervisory-control theories. Such a discrete-event-system controller/supervisor would enable or disable (controllable) events for maximum deadlock-free, correct behaviour of the FMC. However, in cases of multiple part-routes, machine redundancy, etc. the R–W supervisor could include states with subsequent multiple controllable events. The question of choice arises at such states necessitating the use of an on-line decision-making agent, which, consequently, would determine the overall performance of the FMC. In the above context, this paper presents a novel methodology for the on-line, deadlock-free scheduling and control of FMCs. A two-phased method is proposed. During the off-line phase, the FMC is first modelled using time-augmented automata and a deadlock-free supervisor is synthesized using R–W control theory. Subsequently, an off-line decision-making plan is constructed. During the on-line phase, based on the latest state of the workcell and the off-line plan, the best-possible scheduling decisions are made using a real-time optimization search technique. The proposed novel approach is illustrated through a typical manufacturing-cell simulation example and compared with a random-based decision-making policy. It is clearly shown that significant improvement is achieved when using the proposed approach.

Design and Implementation of Emulators for a Real-World Automated Manufacturing Systems Using Scenario

This paper demonstrates how to design and implement the emulators for a real-world automated manufacturing system (AMS). In order to develop and validate system control software for managing AMSs, most laboratories have constructed an experimental test using actual manufacturing equipment. These experimental systems typically occupy a large amount of lab space and require considerable human expertise to operate. In this paper, a scenario-based development environment for the equipment design and implementation are described. The intended advantage of the proposed environment is that, the designer can make an experimental test in a computer and does not need the actual manufacturing equipment. The proposed environment can be used to design and implement a real-world automated manufacturing cell controller at National Taiwan University of Science and Technology (NTUST). We start with a new methodology to model the operation sequences of the system’s equipment (i.e., machine) called scenario. Modeling methodology is the key to the application of scenarios to automated manufacturing systems. The scenarios methodology is able to clearly depict the communication signals for the equipment. And it also can be used to model the resource utilization features within a manufacturing system. Using scenario, we have developed an emulator for an automated manufacturing cell which faithfully replicates the operating characteristics of an ensemble of physical equipment that would typically comprise an AMS.

Serial Agile Production Systems with Automation

To gain insights into the design and control of manufacturing cells with automation, we study simple models of serial production systems where one flexible worker attends a set of automated stations. We (a) characterize the operational benefits of automation, (b) determine the most desirable placement of automation within a line, and (c) investigate how best to allocate labor dynamically in a line with manual and automatic equipment. We do this by first considering two-station Markov decision process models and then studying three-station simulations. Our results show that the capacity of production lines with automatic machines can be significantly lower than the rate of the bottleneck. We also show that automating a manual machine can have a dramatic effect on the average work-in-process (WIP) level, provided that labor is the system bottleneck. Once a machine becomes the bottleneck, the benefits from further automation are dramatically reduced. In general, we find that automation is more effective when placed toward the end of the line rather than toward the front. Finally, we show that automation level increases the priority workers should give to a station when selecting a work location.

Methodology for the design and control of flexible manufacturing cells

The design of a flexible manufacturing system involves a complex process in which it is necessary to take into account many factors, and hence a more simple configuration has been developed as a first step in the global control of a manufacturing system. The configuration is based on cellular concept. Therefore, manufacturing cells are the bases for developing flexible manufacturing systems. In this paper, a methodology for developing flexible manufacturing cells is proposed, which integrates a series of methods and activities that characterise the implementation of manufacturing cells in typical operation systems. Also a deterministic model for batch manufacturing and part selection is proposed.

Automatic logic generation for reconfigurable cell-based manufacturing systems

This paper presents a method to automatically generate the control logic for manufacturing cell controllers, using Modular Finite State Machines (MFSMs). Using the proposed method models can be automatically created upon choice of specifications, and used to run as controllers. They are based on a specified behavior between the cell controller and its supervisor, and are verifiably correct from their construction. The method has been implemented on a small manufacturing test bed at the University of Michigan.

Formal modeling methodologies for control of manufacturing cells: Survey and comparison

Over the last two decades, several formal modeling methodologies have emerged. In the manufacturing cell control domain, these methodologies are directed toward integrating the requirements specification, the design, and the implementation of the cell controller into a consistent process, supported by efficient analysis and development tools. The search for a single methodology powerful enough to span all the stages of the development life cycle of a formal model capable of replacing existing non-formal practices, however, has proven more difficult than expected. This paper presents a survey of several formal modeling methodologies that have been used for manufacturing cell control. Furthermore, the methodologies are classified and compared based on their expressive power, their verification power, their level of abstraction, and their span in relation to the formal model's development life cycle.

Formal modeling methodologies for control of manufacturing cells: Survey and comparison : Ignacio Castillo, Jeffrey S. Smith, v21, n1, 2002, pp40–57

The invaluable health, economic and social impacts of vaccination are hard to exaggerate. The ability to stabilize vaccines is urgently required for their equitable distribution without the dependence on the ‘cold-chain’ logistics. Herein, for the first time we report biomimetic-mineralization of live-viral vaccines using metal-organic frameworks (MOFs) to enhance their storage stability from days to months. Applying ZIF-8 and aluminium fumarate (Alfum), the Newcastle Disease Virus (NDV) V4 strain and Influenza A WSN strain were encapsulated with remarkable retention of their viral titre. The [email protected], [email protected] and [email protected] composites were validated for live-virus recovery using a tissue culture infectious dose (TCID50) assay. With the objective of long-term stabilization, we developed a novel, trehalose (T) and skim milk (SM) stabilized, freeze-dried [email protected] composite, [email protected]+T/SM. The thermal stability of this composite was investigated and compared with the control NDV and non-encapsulated, freeze-dried NDV+T/SM composite at 4 °C, RT, and 37 °C over a period of 12 weeks. We demonstrate the fragility of the control NDV vaccine which lost all viability at RT and 37°C by 12 and 4 weeks, respectively. Comparing the freeze-dried counterparts, the MOF encapsulated [email protected]+T/SM demonstrated significant enhancement in stability of the NDV+T/SM composite especially at RT and 37 °C upto 12 weeks.Vaccination is undoubtedly one of the most effective medical interventions, saving millions of lives each year. However, the requirement of ‘cold-chain’ logistics is a major impediment to widespread immunization. Live viral vaccines (LVVs) are widely used vaccine types with proven efficacy and low cost. Nonetheless, their complex composition increases their susceptability to thermal stress. Several LVV thermostabilization approaches have been investigated, including their complex engineering and the facile addition of stabilizers. Still, the lack of a universal approach urgently requires finding a stabilization technique especially when additives alone may not be sufficient. Herein, we demonstrate MOF biomimetic-mineralization technology to encapsulate LVVs developing an optimised composite which significantly preserves vaccines without refrigeration for extended periods of time.

A generic architecture of manufacturing cell control system

The depiction of an agile manufacturing cell includes a synopsis of some of the agilities obtained by the configuration. The agile configuration here brings additional values, such as rapid new product introduction, accommodation to unpredictable demand, longer equipment applicability, etc. To achieve agile configuration, the cell-control system for agile manufacturing must be rapidly and efficiently generated or modified. The high reconfigurability of cell-control software, such as modularity, reusability and maintainability, must be considered. The aim of this paper is to propose an objectoriented generic architecture that efficiently supports the design and implementation of highly reconfigurable control systems for agile manufacturing cells. The generic architecture is composed of resource objects, informational objects and control object. The structure of resource objects is proposed in detail. To develop cell-control software rapidly, the OPN model is established so as to describe the dynamic behaviour of a resource object, control logic, as well as exchanging with other objects.

Design, analysis and implementation of a real-world manufacturing cell controller based on Petri nets

The primary function of a flexible manufacturing cell controller is to coordinate equipment within a cell to perform a sequence of manufacturing operations required by flexible production. In this paper, we present the modelling, analysis and implementation of a real-world cell controller. A Petri net-based development environment for cell controller design and implementation is described. The intended advantage of the proposed environment is that, users can define and/or change operation flow directly on the modelled Petri net, without programming efforts, otherwise required for general cell controller implementation. The proposed environment is used to design and implement a real-world flexible manufacturing cell controller at National Taiwan University of Science and Technology (NTUST). A scenario-based approach is adopted to model the operation flows in the cell, and from the scenario, we construct its Petri net model. To our knowledge, this is the first work that formalizes the conversion of scenarios to Petri nets. The resultant net is an augmented marked graph (Chu and Xie, 1997, IEEE Trans. Robotics Automat., 13(6), 793 - 804), whose liveness and reversibility are related to empty siphons. For qualitative analysis, after we reduce the net, we are able to generate all minimal siphons and traps, and show that the cell model is live and reversible.