Engineering topics
Karban, Robert
Publications and source records attributed to Karban, Robert.
The OpenSE Cookbook: A Practical, Recipe Based Collection of Patterns, Procedures, and Best Practices for Executable Systems Engineering for the Thirty Meter Telescope
The OpenSE Cookbook is an open-sourced collection of patterns, procedures, and best practices targeted for systems engineers who seek guidance on applying model-based and executable systems engineering (MBSE) using SysML. Its content has emerged from the system level modeling effort on the European Framework Program 6 (FP6) and the Thirty Meter Telescope (TMT). The TMT MBSE approach applied the Executable Systems Engineering Method (ESEM) and the open-source Engineering Environment (OpenMBEE) to specify, analyze, and verify requirements of TMT’s Alignment and Phasing System (APS) and the Narrow Field Infrared Adaptive Optics System (NFIRAOS). In these applications, implicit dependencies are made explicit in a formal model through the use of ESEM, OpenMBEE, and SysML modeling constructs. The value proposition for applying this MBSE approach was to establish precise requirements and fine-grained traceability to system designs, and to verify key requirements beginning early in development. The integration of ESEM and the OpenMBEE tooling infrastructure (providing linked-data and web-operability) is a significant added value for the MBSE approach. The APS is responsible for the overall pre-adaptive optics wavefront quality, using starlight to measure wavefront errors and align the TMT optics. In the formally integrated and executable SysML model, simulations are performed to analyze the impact of changed requirements and verify specified constraints for various operational scenarios. The APS team used several modeling patterns to capture information such as the requirements, the operational scenarios, involved subsystems and their interaction points, the estimated or required time durations, and the mass and power consumption. Adaptive optics systems are designed to sense real-time atmospheric turbulence and correct the telescope’s optical beam to remove its effect. The system model for the adaptive optics operational modes was developed to capture sequence behaviors and operational scenarios to run Monte-Carlo simulations for verifying acquisition time, observing efficiency, and operational behavior requirements. The model is particularly useful for investigating the effect of parallelization, identifying interface issues, and re-ordering sequence acquisition tasks. A former version of the Cookbook (which is now updated to MBSE challenges, goals, and lessons learned) included modeling guidelines and conventions for all system aspects, hierarchy levels, and views, which were developed during for the Active Phasing Experiment (APE), an opto-mechatronical system technology demonstrator for the Extremely Large Telescope (ELT). The Cookbook utilizes the above mentioned system models as real-world case-studies to demonstrate and document the applications of the recipes, providing also instructional examples and addressing the available tooling support. The Cookbook is accompanied by a number of SysML models and aodel libraries which facilitate model authoring and maintenance. The Cookbook covers the different aspects of Systems Engineering such as management of Requirements, Design (behavior and structure), Interfaces, Interdisciplinary Integration, Analysis, Trade Studies, and Technical Resources. This paper presents the background, motivation, architecture, and highlights some key content of the Cookbook. For example, interface management, error budget management, requirements verification, Monte Carlo driven analysis, and timing analysis of operational scenarios. The paper discusses how the capabilities of OpenMBEE contributed significantly to the adoption of executable systems engineering.
Verifying Interfaces and Generating Interface Control Documents for the Alignment and Phasing Subsystem of the Thirty Meter Telescope from a System Model in SysML
This paper presents a novel method for verifying interfaces and generating interface control documents (ICDs) from a system model in SysMLTM. In systems and software engineering, ICDs are key artifacts that specify the interface(s) to a system or subsystem, and are used to control the documentation of these interfaces. ICDs enable independent teams to develop connecting systems that use the specified interfaces. In the context of the Thirty Meter Telescope (TMT), interface control documents also act as contracts for delivered subsystems. The Alignment and Phasing system (APS) is one such subsystem. APS is required to implement a particular interface, and formulates requirements for the interfaces to be provided by other components of TMT that interface with APS. As the design of APS matures, these interfaces are frequently refined, making it necessary for related ICDs to be updated. In current systems engineering practice, ICDs are maintained manually. This manual maintenance can lead to a loss in integrity and accuracy of the documents over time, resulting in the documents no longer reflecting the actual state of the interfaces of a system. We show how a system model in SysMLTM can be used to generate ICDs automatically. The method is demonstrated through application to interface control documents pertaining to APS. Specifically, we apply the method to the interface of APS to the primary mirror control system (M1CS) and of APS to the Telescope Control System (TCS). We evaluate the newly introduced method through application to two case studies.
Analyzing the Operational Behavior of the Alignment and Phasing System of the Thirty Meter Telescope using SysML
The Alignment and Phasing System (APS) of the Thirty Meter Telescope (TMT) is responsible for positioning individual segments of the primary mirror, as well as the secondary and tertiary mirrors. Given its essential role, understanding the as-speci ed behavior and verifying related requirements is vital to the correct operation of the TMT. Analyzing the behavior of APS is challenging due to the variety of interactions with other subsystems. This paper presents results from developing an integrated system model that captures the structure, behavior, and requirements in a formal modeling language to enable automated veri cation using appropriate solvers. Speci cally, demonstrated and discussed are the results of applying a Systems Modeling Language (SysMLTM) based approach in which operational modes, behavior speci cations and use case scenarios are used for the purpose of verifying requirements on timing, power, and pointing error through system-level simulation using a single, integrated model.
Towards a Reference Architecture for Model-Based Engineering Environments
A key aspect of adopting model-based systems engineering as a practice in an organization is the design and development, and adoption of corresponding processes and tools that support the model-based paradigm. In an effort to enable the unified implementation of such processes and tools, this paper introduces a reference architecture model that serves as a specification for a model-based engineering environment. Current systems engineering practices, products, processes and technologies are used as input for continuously refining the architecture model. In the paper, we introduce and report on the current status of this reference architecture model, and present the methodology applied in developing the reference architecture. We conclude that while there are a very large number of domain- or application-specific processes requiring specialized behavior, these can be reduced through abstraction to a small set of core functions that need to be supported by a realization of a model-based engineering environment. Only very few organization-domain- or application-specific aspects require specialized consideration.
The Alignment and Phasing System for the Thirty Meter Telescope: Risk Mitigation and Status Update
Alignment and Phasing System (APS) is responsible for the optical alignment via starlight of the approximately 12,000 degrees of freedom of the primary, secondary and tertiary mirrors of Thirty Meter Telescope (TMT). APS is based on the successful Phasing Camera System (PCS) used to align the Keck Telescopes. Since the successful APS conceptual design in 2007, work has concentrated on risk mitigation, use case generation, and alignment algorithm development and improvement. Much of the risk mitigation effort has centered around development and testing of prototype APS software which will replace the current PCS software used at Keck. We present an updated APS design, example use cases and discuss, in detail, the risk mitigation efforts.
Creating Systems Engineering Products with Executable Models in a Model-Based Engineering Environment
Applying systems engineering across the life-cycle results in a number of products built from interdependent sources of information using different kinds of system level analysis. This paper focuses on leveraging the Executable System Engineering Method (ESEM) which automates requirements verification (e.g. power and mass budget margins and duration analysis of operational modes) using executable SysML models. The particular value proposition is to integrate requirements, and executable behavior and performance models for certain types of system level analysis. The models are created with modeling patterns that involve structural, behavioral and parametric diagrams, and are managed by an open source Model Based Engineering Environment (named OpenMBEE). This paper demonstrates how the ESEM is applied in conjunction with OpenMBEE to create key engineering products (e.g. operational concept document) for the Alignment and Phasing System (APS) within the Thirty Meter Telescope (TMT) project, which is under development by the TMT International Observatory (TIO).
Using Executable SysML Models to Generate System Engineering Products
No abstract available
Ontology and modeling patterns for state-based behavior representation
This paper provides an approach to capture state-based behavior of elements, that is, the specification of their state evolution in time, and the interactions amongst them. Elements can be components (e.g., sensors, actuators) or environments, and are characterized by state variables that vary with time. The behaviors of these elements, as well as interactions among them are represented through constraints on state variables. This paper discusses the concepts and relationships introduced in this behavior ontology, and the modeling patterns associated with it. Two example cases are provided to illustrate their usage, as well as to demonstrate the flexibility and scalability of the behavior ontology: a simple flashlight electrical model and a more complex spacecraft model involving instruments, power and data behaviors. Finally, an implementation in a SysML profile is provided.