Structured adaptive supervisory control model and software development for a flexible manufacturing system

The present study describes the development of control hardware and software for a mobile welding robot. This robot is able to move and perform welding tasks in a double hull structure. The control hardware consists of a main controller and a welding machine controller. Control software consists of four layers. Each layer consists of modules. Suitable combinations of modules enable the control software to perform the required tasks. Control software is developed using C programming under QNX operating system. For the modularizing architecture of control software, we designed control software with four layers: Task Manager, Task Planner, Actions for Task, and Task Executer. The embedded controller and control software was applied to the mobile welding robot for successful execution of the required tasks. For evaluate this imbedded controller and control software, the field tests are conducted, it is confirmed that the developed imbedded controller of mobile welding robot for shipyard is well designed and implemented.

A new manufacturing control software development methodology called IOPN (integrated object-oriented Petri net paradigm) is presented. The IOPN consists of four phases: (1) static analysis; (2) dynamic analysis; (3) integration; and (4) implementation. In the static analysis phase, all possible object classes required by the manufacturing control software, and the static relationships among these object classes are identified. In the dynamic phase, the objectoriented Petri net (OPN) control model is derived according to both the dynamic behaviour of shop floor operations and the desired control logic. After the control logic specified by the OPN model is analysed and there is proven to be no deadlock, the required control decision/knowledge (e.g. scheduling/ dispatching knowledge) must be included in the OPN model. Finally, the manufacturing control system is implemented directly from the specification of the OPN model by applying a number of transformation rules. Since the IOPN approach not only possesses the characteristics of object-oriented methods and Petri nets, but also provides a straightforward mapping between the high-level specification of the control logic and the code of the control software, the time required for developing a new control software or modifying an existing control software to accommodate to the operational changes will be greatly reduced.

In order to solve the problem that it is difficult to achieve better multi-robot coordination operation using the original control system in multi-robot cooperative systems, this paper conducts system modeling, control framework design and software development and verification experiments for multi-robot cooperative systems. We firstly model the system composed of multiple robots and operated objects. The coordination between any two robots can be divided into two categories: loose coordination and tight coordination according to the constraint relationship between the robots and the objects, based on which the kinematics and dynamics analysis of the multi-robot system is carried out. A multi-robot cooperative control framework is designed, which contains modules for task planning, force and position assignment, sensor information acquisition, position/force control and synchronization clock. On the basis of the multi-robot cooperative control system, the robot cooperative control software is designed and developed, and the software system contains, with excellent characteristics. Finally, an experimental environment containing three large-load EFORT industrial robots was established and experiments were conducted using the developed multi-robot cooperative control software to verify the usability and reliability of the software system.

A development framework for supervisory control software of automated manufacturing systems

With the growing adoption of Industry 4.0 concepts in production systems, new challenges arise in engineering control software. Highly distributed control with tight real-time constraints and safety regulations results in increasingly complex software. Current research focuses on increasing the abstraction with new architectures and modularization of software. The presented PhD research addresses modeling of the interactions between control software components, and of the emergent behavior of these compositions. Such behavior models can support the initial implementation, and facilitate (semi-)automated testing and monitoring of control software. Finally, visualizing behavior in a model can enhance understandability of existing control software, when software developers need not access abstracted hierarchy levels to deduct their functionality. This work aims at optimizing the benefit of behavior models in developing control software: Modeling the expected behavior directly for new software will allow using them throughout the software life-cycle. For legacy software, the initial development effort of behavior models will be minimized by automatically capturing behavior models from the implementation. The approach is evaluated in case studies and user studies to integrate experiences from the industrial domain into this software engineering research.

Flexible manufacturing systems (FMS) consists of a set of numerically controlled machines, material handling systems (MHS), information system and service centres all working towards a common production schedule goal being the achievement of economic product manufacture in short period of time[1]. An FMS is highly versatile production system capable of performing many different operations given the proper tooling, fixtures and materials. Another feature of this system is the short switching time between different operations assigned to its individual workstations. An FMS to function effectively must have an on-line control system capable of reacting quickly to any problem occurring in the system by providing decisions to deal with the problem in a short period of time. The FMS control system thus needs to receive accurate and reliable information from the shop floor. The operational control of an FMS in general involves accessing a large set of static and dynamic data, and requires complex control algorithms. This paper presents a control system developed for real-time operational control of an FMS. The system is organised hierarchically, each level responsible for making decisions according to the operational needs and the time criticality of the particular level. The overall aim of the control system is to optimise FMS performance while meeting the production requirements.

Deadlock prevention plays an important role in the modeling and control of flexible manufacturing systems (FMS). This paper presents a novel and computationally efficient method to design optimal control places, and an iteration approach that only computes the reachability graph of a plant Petri net model once in order to obtain a maximally permissive liveness-enforcing supervisor for an FMS. By using a vector covering approach, a minimal covering set of legal markings and a minimal covered set of first-met bad markings (FBM) are computed. At each iteration, an FBM from the minimal covered set is selected. By solving an integer linear programming problem, a place invariant is designed to prevent the FBM from being reached and no marking in the minimal covering set of legal markings is forbidden. This process is carried out until no FBM can be reached. In order to make the considered problem computationally tractable, binary decision diagrams (BDD) are used to compute the sets of legal markings and FBM, and solve the vector covering problem to get a minimal covering set of legal markings and a minimal covered set of FBM. Finally, a number of FMS examples are presented to illustrate the proposed approaches.

Presented in the paper is MES (manufacturing execution system) architecture, which is suitable for managing FMS (flexible manufacturing system) lines under an ERP (enterprise planning system)environment. An IDEF0-model of an 'order handling' shop floor having an FMS line is developed to identify functional requirements of MES, and then a two-tier MES architecture satisfying the functional requirements is proposed. The proposed MES is composed of a Main-MES (for the main shop floor) and an FMS-MES (for the FMS line). A BOP (bill of processes) is used as a means to represent process plans, and a LS-Net (loading schedule network) is used as a mechanism for representing and manipulating loading schedules. Object models of BOP and LS-Net are presented, and the effectiveness of the proposed MES is demonstrated by applying it to two FMS lines, a stamping-die machining line and a mechanical part machining line.

A metamodeling approach for safe control software

Introduction. The “Smart Agroˮ committee of Research and Education Center “Engineering of the Future” has identified a number of tasks relevant for improving the efficiency of precision, soil-protecting and conservation agriculture. One of these tasks is the development of a digital multi-agent system, which provides a number of services for agricultural enterprises, developers and manufacturers of agricultural machinery. The purpose of the present study is to model an autonomous mobile robotic platform, including the development of software and hardware for trajectory control. Materials and Methods. To solve the problem, there are used modern CAx systems and their applications, the methods of 3D and full-body modeling, and the method of numerical solution of problems in solid mechanics. To expand and improve the standard functionality of CAx-systems (SolidWorks) in the software implementation of trajectory control algorithms, the methods and technologies of programming using API SolidWorks, VisualStudio C++ (MFC, ATL, COM) are used, and to build physical full-scale models ‒ Arduino and fischertechnik platforms. Results. The result of the study is a software and hardware module of trajectory control for an integrated (physical and virtual) model of a mobile robotic platform, which can be provided to the consumer as a service for technology autonomation. For the developed integrated model, control algorithms for various types of trajectories were tested. Discussion and Conclusion. The developed integrated software and hardware model of trajectory control can be used by developers and manufacturers of agricultural machinery, and directly by agro-enterprises for implementing typical technological processes. A feature of the implementation is an open hardware and software interface that provides the integration of mobile robotic platforms based on a digital multi-agent system.

The high cost and long development cycle of shop floor controls (SFC) have prevented many small, medium, and even large-size manufacturers from deploying plant-wide, real-time information systems. In order to stay competitive in a make-to-order business model, such systems are essential. In addressing the obstacles to such systems, this article proposes a formal method that ensures that a built SFC can be applicable to a plant-wide, real- time information system. By taking advantage of both the linear growth of the complexity function in a structured adaptive supervisory control model, and the real-time responses of a virtual production line based e-Manufacturing system, a formal method for creating an integration-ready structured adaptive supervisory control model (iSASC) for a discrete manufacturing system is introduced. An iSASC-based SFC prototype system was successfully tested and evaluated in an industrial site.

An FMS is a typical real-time concurrent system composed of a number of computer-controlled machine tools, automated material handling and storage systems that operate as an integrated system under the control of host computer(s). The growing demand for higher performance and flexibility in these systems and the interlocking factors of concurrency, deadline-driven activities, and real-time decision making pose a significant challenge to FMS design, especially in terms of control and scheduling. A formal engineering approach that helps handle the complexity and dynamics of FMS modeling, design and analysis is needed. A real-time architectural specification (RAS) model and its application in the modeling of flexible manufacturing system (FMS) are presented. RAS combines mature operational and descriptive formal methods, in particular time Petri nets (TPN) and real-time computational tree logic (RTCTL), to form an integrated system model for architectural specification and analysis of real-time concurrent systems such as FMS. The contribution of RAS is twofold: First, it provides a formal system to systematically maintain a strong correlation between (real-time) requirements and design and to verify the conformance of the design to the requirements, which helps enhance traceability and thus to help us to achieve high assurance in design. Second, it offers better scalability in modeling and analysis, which provides an effective way to deal with complexity in the application of formal methods. These two features together make RAS a suitable model for the design of FMS.

The modeling of flexible manufacturing systems (FMS) under uncertainty and evaluation of a rule base for online scheduling is considered. To represent uncertain events in FMS, such as failure of machine tools, repair time and processing time, apply continuous-time and discrete-time stochastic Petri nets with hierarchical structure to constructing the FMS model. To obtain an efficient schedule of FMS with on-line real-time basis, the authors construct a rule base and evaluate the performance of the rule base using the FMS simulation system. >

The authors discuss the modeling of flexible manufacturing systems (FMSs) under uncertainty and evaluate a rule base for online scheduling. To represent uncertain events in an FMS, such as failure of machine tools, repair time, and processing time, they develop continuous-time and discrete-time stochastic Petri nets with hierarchical structures for constructing the FMS model. For obtaining an efficient schedule for the FMS with an online real-time basis, they construct a rule base and evaluate its performance using the FMS simulation system proposed. >

Flexible Manufacturing Systems (FMS) provide capabilities to accommodate flexibility requirements in production. Such system due to the levels of flexibility are complex to reconfigure optimally. Simulation is one of the tools that provide a platform for supporting the FMS reconfiguration without breaking optimal production set-up. For the simulation to be successful it is important to appropriately design the simulated environment as well as provide quality data inputs. As FMS are usually driven by production line controllers (PLC), the behaviour of elements in the system can be difficult to be fully understood. The quality of data fed in to the simulation affects the quality of outputs which in consequence translates to the trust that the simulation is reliable source of analysis. This paper presents the approach of data collection from the shop floor aiding FMS simulation in scenarios where it is difficult to understand the system behaviour. Also, case study of a manual handling robot in the FMS is presented to demonstrate obtaining quality data from the production shop floor.