The planning of modern assembly lines with Human-Robot-Collaboration (HRC) for complex technical products with a large number of process steps and involved resources leads to a large number of possible assembly scenarios. The integration of cobots in manual assembly workplaces and the consideration of the Safety-related aspects, aspects of the design of HRC workplaces, and aspects of HRC process planning lead to an increased complexity in the development and planning of assembly processes.
The model-based system development approaches using SysML offer a promising potential to master the complexity in planning and performing upstream analyses to evaluate different assembly scenarios of the HRC assembly lines. Nevertheless, performing only cross-discipline analysis at system level, without downstream studies in integration with the virtual twin of the assembly line is not sufficient for validating all aspects, in particular the production-specific aspects of the HRC assembly line.
For the detailed specification of the assembly scenario as well as for its comprehensive validation, the integration of the assembly scenario into a manufacturing specific CAD/CAM simulation environment like Delmia is required. However, there is still no suitable integration solution to import the desired contents of the SysML model into Delmia environment.
WHAT?
In order to overcome the challenges highlighted, a concept was developed that is carried out in three main steps with the following tool chain.
In the first step (left side) a concept for model-based design and early analysis of different assembly scenarios using SysML in Cameo systems Modeler is presented. The analysis provides the most suitable assembly process according to the selected criteria such as expected costs and lead times. In the second step (middle part), a concept for a model transformation is presented, which is used to transform the assembly scenarios defined and analyzed cross-disciplinarily in SysML into the Product-Process-Resource (PPR) format, which is the established data format of Delmia for the planning of production processes. By converting the assembly scenario from SysML to PPR, each individual work step of the assembly scenario can now be assigned to the corresponding 3D CAD model from the MBOM of the product, which is consumed in this work step (right side). Furthermore, each work step can be assigned to the 3D CAD model of the resource from which it is being executed. The developed concept is carried out in three main steps using the following tool chain.
HOW?
Step 1: Trade-off analyses on system level using SysML
In order to perform system-level trade-off analyses, different assembly scenarios are first modeled each in a SysML activity diagram. SysML compartments represent the resources involved in the production processes, such as cobots and workers. Each action in the activity diagrams have evaluation criteria assigned as constraints so that their impact on the overall assembly scenario can be examined in the trade-off analyses. The evaluation criteria for such trade-off analyses include, for example, expected costs or production-related criteria such as lead time.
Step 2: Transformation of SysML models into the PPR format
The model transformation is based on transformation rules defined in the Enterprise Knowledge Language (EKL) that map elements from the SysML metamodel to the Delmia PPR metamodel. Using Enterprise Knowledge Language (EKL), one can search for objects in the database, navigate through different structures, create Products and PLM Objects in general, Instantiate templates, set or read attributes and export data into Excel and XML. The XML Metamodel Interchange (XMI) data format is used as output format for the SysML model and serves as input format for the model transformation. The main idea of the concept for model transformation is to parse through the XMI file and uniquely identify the elements, which needs to be transformed, and cache each type of them in a separate list. Each SysML element is stored in the exported XMI file in a well-defined way with specified XMI tags, attribute names as well as attribute values. These three characteristics are used to uniquely identify and cache the desired SysML elements when parsing the XMI file. Then, the cached lists containing the desired elements are each to be looped and their contents mapped to the semantically compatible PPR elements in DELMIA. The model transformation provides the possibility to map the actions of the SysML activity diagram to different types of PPR work steps such as general, transfer, load and unload work steps. Not only the actions, but also the relationships between these elements such as flows as well as their attributes such as the duration of the respective work step or the assignment of the work steps to the resources are transformed into PPR.
Step 3: Linking the PPR process scenario with the MBOM of the product
In order to exploit the production-specific simulation possibilities in DELMIA, the work steps transformed into the PPR format need to be linked to the product models. For this purpose, the assembly sequence captured in the transformed assembly scenario is assigned to the corresponding MBOM elements of the product, which are already linked to the 3D CAD models of the product (EBOM). This determines which part or assembly of the product is implemented by which work step, which is a fundamental prerequisite for the production-specific simulation activities. As a result, the continuously linked PPR data structure, starting from EBOM, on to MBOM, processes and resources, has been achieved. This can serve as the basis for various production simulation options such as process flow simulations, ergonomic evaluations of the workers as well as simulations to assess the feasibility of the planned work steps.
Values
- taking advantage of upstream simulation capabilities in Cameo to narrow down the possible assembly scenarios before going down to production-specific simulations
- automatic model transformation of assembly process from SysML to PPR (without need for re-modeling in Delmia)
- flexibility and extensibility of the model transformation for different use cases
- enabling downstream analysis for comprehensive validation of the assembly scenario in Delmia with respect to production-specific aspects
If you have any questions or are interested in a more detailed description of the solution, feel free to reach out to me or comment this post or even better: Join me at the "Day of Systems Engineering 2022" (TdSE2022) in Paderborn, Germany on November 17 (09:45 - 10:30 in HNF S3), where I will present this solution.
Special thanks to @SL, @SP and @PG for their great support.
