Manufacturing System Engineering with Mechatronical Units Abstract
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.
This paper describes from good practice experiencehow mechatronical units can be modeled and used within the mechatronical engineering process, how the datadescribing mechatronical units can be structured within tools and exchange formats, and how mechatronical units can be derived to be re-usable within the mechatronical engineering process.
Thereby, this paper gives advices for an efficient and proper application of mechatronical units within engineering processes of manufacturing systems.
1、Motivation
Within the last years the engineering process of manufacturing systems (EP) has drastically changed due to changing economical and technical conditions. The share of cost caused by engineering activities among the overall lifecycle costs of a manufacturing system has increased. Hence, today manufacturing companies are interested in reducing the engineering costs [1]. This reduction can be reached by several ways. One of the most often considered ways is shortening the EP by abridge and interlink the different engineering activities.But this activity is difficult to achieve [2, 3] since the crucial point of EP shortening is the necessity to ensure consistency among the different engineering activities with respect to the applied and developed engineering artifacts.
A second often discussed problem, the EP has to cope with, is the need of more flexible manufacturing systems created within the EP [4]. A maximal flexibility with respect to possible products, applied technologies, and used resources is claimed. But these flexibility requirements contradict the intended shortening of the engineering process as both an increasing product variety and an increased technology flexibility increase complexity of the manufacturing system.
To solve this problem within the last years the well known mechatronic paradigm has been adapted to manufacturing systems [4]. Based on mechatronical units (MU) and a mechatronical engineering process (MEP) it seems to be possible to reduce the engineering efforts and time while enabling manufacturing system flexibility.The MEP considers a distinction between customer projects independent and customer project dependent engineering activities. The project independent engineering activities consider the definition of invariant system building blocks and the definition of interfaces to these invariant building blocks establishing MU.The project dependent engineering steps will use/reuse the MU within engineering discipline crossing
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engineering processes as depicted in the upper part of Figure 1.
Figure 1: Dependencies betw. MEP and MU
But the success of MEP shortening and manufacturing system flexibility increase strongly depends on the way are exploited within the MEP. This use is based on a set of questions (see Figure 1 lower part).
The first set addresses the way engineering information is structured and reflected generally for both engineering process types. It claims a basic concept for the modeling of mechatronical units which has to be mapped to the different tools and exchange format applied within the MEP.This set of questions is considered in section 2,3 and 4 of this paper. The second set of questions deal with the application of MUs within the project dependent engineering process. Here the amount of basic actions supported by the MU information structure and its integration within the overall work flow of the MEP is relevant. Based on them an optimized tool support can be developed. This is addressed in section 5 and 6.The third set of questions consider the application of MUs within the project independent MEP. It asks how reusable MUs can be derived and is drafted in section 7.
2、Principles of modeling MUs The idea of MUs is not new [5]. It has also been considered within manufacturing system engineering [6, 7]. Also this idea has found its way into standardizationdocuments [8]. Within control system engineering a MU will be understood as combination of mechanical, electrical,and control related components.This combination is made with the special purpose to ensure a dedicatedunit behavior which can be provided to an overall system.Thereby,
mechatronical systems are seen as hierarchy of MUs [7]. At the lowest level of the hierarchy so-called basic blocks establish an energetical, material,and informational flow of the controlled system (i.e. the manufacturing process), actuators, sensors, and information processing units. At the higher levels the MUs connect lower level MUs with information processing units of the higher level.
Figure 2: Information structure of the MU 图2: MU的信息结构
Within the MEP MUs are considered as units providing dedicated manufacturing functionalities to the manufacturing system.These functionalities and the conditions required for its provision are the main information modeling paradigm considered within the MEP. Hence, and also following the history of engineering with different independent engineering activities and disciplines, the MU is seen within the MEP as consistent combination of information sets of different engineering disciplines with dependencies among the information while the different involved information can be
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classified. This classification can follow engineering discipline related [9],plant
structure related [20], or data related [13] structures. But all of these approaches are not complete. They have to be combined. The resulting structure is depicted in
Figure 2. (The capital letters within this figure are used to describe the mapping of information to data storing structures described later on.) The named information set consists of 6 main subsets:
? The process control data consists of all control relevant information including control code and control code specifications of any kind (B) and signal information like signal list and variable definitions (A).
? The mechanical data (C) cover all information about the mechanical construction including geometry and kinematics data.
? The electrical, pneumatic, and hydraulic data (D) describe the electrical, pneumatic, and hydraulic construction of the MU including the connections and wiring of the different types and its plugs.
? The topological data (E) cover the hierarchy of MUs
and devices. They give an overview about the structuring and the interfaces within the hierarchy.
? The function describing data will give a functional description of the. This contains relevant functional parameters (F), and technological descriptions
and guidelines (G), and functional models of the uncontrolled (H) and controlled behavior (I) of the MU.
?Finally, the generic data (J) summarize further organizational, technical, economical and other data.They cover for example article codes and manufacturer identifications and addresses, weight and size of the MU, supply information for electrical and other power, costs for acquisition and maintenance, and user manuals.
Additionally to the data sets the information structure has to ensure consistency among the different data sets. For example, the size information within the generic data has to match the size information in the geometry descriptions and the power supply information has to conform the electric, pneumatic, and hydraulic data.
3.Modeling of mechatronical units within computer aided engineering tools
Among others, one tool supporting the application of MUs within the MEP is the SIMATIC Automation Designer by Siemens AG [10, 11].SIMATIC Automation Designer [AD] follows the vision of digital engineering from transfer of the planning phase CAD data, through configuring of the automation solution, right up to use during live operations. It allows the integrated representation of mechanical components, electrical systems and automation in one mechatronic plant model and enables modular configuration of manufacturing automation projects based on parameterizable engineering templates. By using engineering templates, MUs can be predefined, stored in libraries and used to model multiple manufacturing systems by selection, instantiation, parameterization,extension and interlinking.
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AD offers high flexibility of modeling, reflecting its integration in different MEPs and system environments. For comprehensive modeling and tool support it is necessary to map the information sets of our MUs concept to the AD modeling structures.
Therefore, the following mapping reflects strongly the manufacturing automation relevant parts of the MU without neglecting all others.
The suggested information structuring is based on the idea that MUs will provide functions to the overall system. These functions can be primary functions directly used within the manufacturing process like transportation functions in the case of conveyers, manufacturing functions in the case of machines, cells, or robots, or supporting functions in the case of clam sets. In addition to the primary functions there can be secondary functions required for correct behavior of the MU.Such functions can be maintenance functions or preparation functions like manufacturing parameter adjustment.
Figure 3: Possible modelling of one mechatronical unit in AD
Within the suggested information structuring the internal structuring of the functions should be standardized.Each function is controlled by appropriate control code.This code implements a behavior specification given by a program organization unit (POU).To connect the functions to the underlying MUs and devices and to parameterize them, appropriate interfaces and parameters are defined.
To provide the functions the MU consists of lower level MUs and devices which are given within the devices part.To be used from the higher level MUs each unit has an execution interface with appropriate parameters for the overall. This interface structure of a MU is given in Figure 4.
Figure 4: Interface structure of MU
The behavior of the MU will be described within the sequences part of the information structure.Here models of controlled as well as uncontrolled behavior can be integrated for analysis purposes like virtual commissioning.
Finally there is a separate sub-information set for the geometry and kinematics information. The described structure is given in Figure 3. The capital letters within Figure 2 und 3 give the mapping of the different data sets relevant for the MU to the suggested representation in AD.Thereby, it can be seen, that:
? the MU itself contains functional parameters (F), functional descriptions (G) , and generic data (J), the functions (primary as well as secondary) directly covers the technological descriptions (G), the function sub-structure POU gives the controlled behavior (I),
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? the function substructure Code gives control code (B)
? the function substructure device interface + parameters gives parts of the signal information (A), electrical, hydraulic, and pneumatic data (D), and functional parameters (F),
? CAD data / kinematics gives geometry and kinematics information (C), ? the devices gives the topology information (E),
? the sequences give the controlled (I) and uncontrolled (H) behavior models, and ? the execution interface and parameters gives further parts of signal information (A), electrical, hydraulic, pneumatic data (D), and functional parameters (F). Thus the mapping is complete. 。
4.Modeling mechatronical units within exchange formats One of the recently developed exchange formats applicable for MUs is the AutomationML exchange format.
The project dependent MEP starts with the process planning.Within this step the necessary manufacturing steps, required to establish the intended product resp.products are defined.Beneath the characteristic product parameters especially the manufacturing functions required to manufacture the product are specified.
Within the second engineering step the general layout of the manufacturing system is planned.Therefore, the required manufacturing functions are mapped to manufacturing resources which are sequenced in a corresponding order. This engineering activity starts with a mapping of required manufacturing functions to MUs with the capability to execute the manufacturing functions. These MUs are concretised by necessary dimensioning and control application and placed in the manufacturing system resulting in a general manufacturing system layout afterwards.
In the subsequent realisation by functional engineering all necessary details of the manufacturing system are specified. Within nearly parallel processes the mechanical,electrical, and control system related engineering activities are implemented.
Thus, the general manufacturing system layout is concretised up to the detailed mechanical drawings, wiring planes and control code. Within this step the pre-developed engineering information of MUs is exploited to increase the engineering quality / efficiency while reducing engineering duration.
The final engineering phase is assigned to the final implementation and commissioning of the manufacturing system based on the detailed system specification.
As pointed out, the MU is used in all of these four engineering steps. In the first step
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