Model-Based System Engineering - Beyond Spreadsheets

Are you relying on Visio, PowerPoint, and Excel to manage your systems engineering documentation?  Many development teams are finding that approach just doesn’t cut it anymore.

Even small teams are dealing with the increased product complexity that comes from adding electronics and embedded software to formerly mechanical designs. 

In response, CAE and PLM vendors are introducing model-based system engineering solutions to help manage development lifecycles like the Systems V.

System Engineering based on document control is inherently fragile

Imagine a Tier 1 supplier that has to integrate autonomous cruise control into an existing lane-change avoidance system.   Currently, the supplier provides two basic architectures for the system – one based on radar and the other on lasers.  Each architecture has a number of variances that support the requirements of individual OEMs.  

Now also imagine that their system engineering process is all document-based.  The original requirements, architecture design, and embedded software specifications are captured in a mix of Excel, Word and Powerpoint.  Designing the new functionality requires manual examination, discovery and reconciliation of the implicated sub-systems and interfaces described in all these documents.  For the team, it’s a fragile and burdensome process that inevitably results in late stage design contradictions.

Complex systems like active safety controls often need multiple concurrent development cycles to manage the mechanics, software and electronics. As these subsystems add up, systems engineering software like the SCADE System from ANSYS can specify the functions, architecture and interfaces of these sub-systems in terms of unambiguous models, then connect them together to verify that key system requirements are met.

Model Based Systems Engineering addresses the challenges that documents present

MBSE has evolved to allow teams to better manage changes to ensure proper updates and traceability.  However, it requires a layer of management software.  As the development of a product progresses from high level system models to component models, system engineers encounter a fragmented set of tools that separately document the mechanical, software and electronic development paths. 

Modeling all the myriad interactions between mechanical, electronic and embedded software systems through multiple iterations isn’t a job for spreadsheets. 

According to Scott Leemans, principal engineer at Advatech Pacific, there are multiple ways to manage System Engineering, “At its heart, MBSE relies on dynamic 3D CAD models that include all of the sub-system definitions. The design starts with a generic model (upper left of the V) that is then better defined as details are fleshed out. The output at the bottom left side of the V are component level functions, dependencies and interfaces that are all described in high-fidelity detailed component models.”

These component models don’t always seamlessly connect to the system level models, although some system management tools for software are able to manage the entire Systems V from concept to validation. 

What a MBSE management system looks like

MBSE software offers multi-level block diagrams and other common toolsets for describing the system functions and architecture.  In addition to designing the system, these tools are used to manage the interfaces between sub-systems and to trace the system requirements down to the design details.  

Because the description is in the form of a dynamic model, if an aspect of the design changes, the implications on other sub-systems or the original requirements are immediately evident.  Moreover, a system model enables automatic verification and optimization of the architecture long before component detail designs are available. 

MBSE solutions are designed to ensure that the system is designed consistently and in-line with requirements and that data is up to date through model checking and model difference comparisons.

Many MBSE solutions, including entry-level offerings, are based on the open standard Systems Markup Language (SysML).  SysML enables the transfer of models up and down the supply chain.  SCADE System from ANSYS is one such SysML-based solution.  It was developed originally for the embedded software industry, so it is particularly adept for complex control and display systems, and it synchronizes with tools for simulating and generating embedded software.   

Other MBSE software features include:

• Diagram creation (Binary Decision & Internal Block Diagrams)
• Allocation/model/data libraries & tables
• Customizable design rules checker (useful for industry specific guidelines like AUTOSAR and IMA)
• Definition and management of data dictionaries
• Prototyping, certification, & verification

“What sets the ANSYS MBSE solution apart from others is that it is integral to our best-in-class engineering simulation tools spanning mechanical, electronics, and embedded software development,” said Todd McDevitt, Marketing Director at ANSYS. “While our competitors started from the PLM backbone and moved down the Systems V into model-based system design, we started at the bottom, developing the most advanced technology in detailed physics simulation and embedded software development.  We’ve then used these as building blocks to provide model and simulation-driven product development solutions across the whole Systems V.”

Simulation has historically been confined to component or sub-system level models, and even then only in the validation stages.  By using a Model Based Systems Engineering approach supported by MBSE software, program managers and system engineers can simulate the entire system to identify likely sources of failure before those problems are designed into the components.

Note: ANSYS has sponsored promotion of their CAE software solutions on ENGINEERING.com. They have no editorial input to this post - all opinions are mine. – Shawn Wasserman