Arndt Lüder

AutomationML - the glue for seamless automation engineering

This contribution presents the basic architecture of the neutral data format AutomationML developed by the companies Daimler, ABB, Siemens, Rockwell, Kuka, Zuhlke, netAllied and the universities of Magdeburg and Karlsruhe. AutomationML serves for the data exchange between manufacturing engineering tools and therefore supports the interoperability between them. It covers information about the plant structure (topology and geometry) and the plant behaviour (logic and kinematics). The first version of AutomationML has been presented at the Hannover fair in 2008.

Modeling of PLC behavior by means of timed net condition/event systems

Net condition/event systems (NCES) are a particular representation of the modeling paradigm of condition/event systems introduced by Sreenivas and Krogh (1991). This paradigm allows modular modeling of discrete event systems. In this paper, we use NCES for modeling of PLC programs and their execution. Since the internal behavior of a PLC is time-driven and since we intend to model timers as well, we extend the strictly causal, untimed model of NCES to a timed NCES (TNCES). We demonstrate how this model is used to describe in detail the behavior of a PLC. An automatic translator which uses instruction list as input and which generates a TNCES model of the PLC behavior has been developed. As a result, we achieve very realistic, mathematical models of a PLC which can be used either to simulate the PLC behavior or-together with models of the plant-to verify the control code.

Distributed intelligence for plant automation based on multi-agent systems: the PABADIS approach

To manage the emerging problems of companies in todays economical surroundings a new thinking in control is required. On the level of field control a step to distributed systems based on distributed intelligence is the state of the art. But on the above levels of control, central and therefore inflexible systems are predominant. This leads to rigid control structures unable to react on system changes with respect to machinery and product programme in a fast and cost-saving way. The PABADIS approach aims in solving the mentioned problems by introduction of horizontal as well as vertical flexibility into the control structure. This flexibility is reached by using mobile and residential agents to establish distributed intelligence on the level of manufacturing execution systems and integration of distributed intelligence on the field control level.

A Signal Extension for Petri Nets and its Use in Controller Design

Petri nets have a longstanding history in controller design and implementation, and it is often told that they have the dominating position in this field due to the close relationship between Petri nets and Graphcet or other sequential function diagrams. We want to show that there are some severe problems when Petri nets are used to describe both: the controller and the plant under control. The nature of these problems is the lack of a concept of input and output signals and, moreover, the lack of a formal concept to interconnect systems modeled by Petri nets via signals. Although this is often neglected, it turns out to be a key issue if a model of the closed-loop behavior must be established as a precondition for formal controller verification. We present a signal extension for Petri nets and means for interconnecting an arbitrary number of those extended Petri nets. We come up with the conclusion that the resulting models are suited for controller verification. Although the graphical appearance shows similarities to Petri nets, the resulting models are no longer Petri nets.

Distributed automation: PABADIS vs. HMS

PABADIS |4| deals with plant automation systems in distributed way using mobile agents as a key point of the project HMS is a well-known concept, which have been successfully implemented in industry and deals with the same problems PABADIS aims. We give a description of the PABADIS projects and makes comparison between two concepts showing advantages and disadvantages of both systems.

Manufacturing system engineering with mechatronical units

Within the engineering of manufacturing systems the paradigm mechatronical units is of important interest. To deal properly with mechatronical units within manufacturing system engineering they have to be defined, described and used in an appropriate way establishing a mechatronical engineering process.

Distributed automation: PABADIS versus HMS

Distributed control systems (DCS) have gained huge interest in the automation business. Several approaches have been made which aim at the design and application of DCS to improve system flexibility and robustness. Important approaches are (among others) the holonic manufacturing systems (HMS) and the plant automation based on distributed systems (PABADIS) approach. PABADIS deals with plant automation systems in a distributed way using generic mobile and stationary agents and plug and participate facilities within a flat structure as key points of the developed control architecture. HMS deals with a similar structure, but aims more at a control hierarchy of special agents. This paper gives a description of the PABADIS project and makes comparisons between the two concepts, showing advantages and disadvantages of both systems. Based on this paper, it will be possible to observe the abilities and drawbacks of distributed agent-based control systems.

Aggregation of engineering processes regarding the mechatronic approach

Within the last few years different process structures for the execution of engineering processes in the field of production systems have been developed and partially standardized. These processes have strong similarities and dependencies enabling the development of a generalized engineering process for production systems. In addition the different engineering processes can highlight the use of mechatronical units. This paper will survey existing engineering processes and will make a first attempt to define such a mechatronic oriented generalized engineering process for production systems. Thereby, it intends to provide a starting point for further discussion on this subject.

Mapping of IEC 61499 function blocks to automation protocols within the TORERO approach

The design of distributed control systems (DCS) contains three major parts: (1) the programming of the control application code of the DCS, (2) the functional allocation of the control application code to the specific devices that the DCS consists of, and (3) the mapping of the distributed control application code to the underlying communication platform depending on the distribution. This paper presents an approach for the mapping of event triggered IEC 61499 function blocks to the underlying automation protocols, whereas time triggered and event triggered automation protocols will be considered. This work is part of the research project TORERO, which is funded by the European Commission under the IST program

Controller synthesis for net condition/event systems with a solution for incomplete state observation

The paper presents a method for logic controller synthesis based on net condition/event models of the uncontrolled plant and specifications of forbidden states. Plant models are set up in a structured and modular way. Synthesis is performed by means of a complete symbolic local backward search from the forbidden states to the control inputs. The algorithm is performed over the structure of the model; a generation of the complete state space is only required in the worst case. The result is a logic controller which can be directly implemented. Solutions for incomplete observation of states of the plant are given.