Electrical systems’ complexity increases the challenges for OEMs

April 8th, 2014, Published in Articles: EngineerIT

 

This abridged White Paper discusses the rising demand for electrical/electronic (E/E) systems functionality in automotive and military/aero vehicles due to customers and legislative requirements. To deal with these complexities would a systems engineering approach not be better to deal with these new demands?

In a White Paper by Mentor Graphics “Managing electrical complexity with a platform level approach and systems engineering” (www.mentor.com) several of these problematic issues are highlighted and the systems engineering approach offered as a possible solution.

The demand for electrical/electronic (E/E) systems functionality in automotive and military/aero vehicles presents particular challenges for OEMs, including: the high cost of electrical systems development and manufacturing; increasing bulk and weight; electrical malfunction resulting in unreliability or breakdowns; and configuration variability offered to customers, as well as legislative requirements, that greatly increases the complexity of platform electrical systems.

In this context, the electrical distribution system platform plays a unique role. It interconnects all the individual E/E systems to enable this functionality. Although the individual systems work separately as intended, when they are connected, unanticipated properties emerge that can cause problems. These resulting errors and problems often appear late in the design and build process, resulting in delays in the production schedule and costly rework.

Electrical design engineers are inundated with changes made to the many subsystems of the platform throughout the development and manufacturing process. Managing and keeping track of these changes from various engineering disciplines and business domains is an ongoing problematic issue.

More electrical systems add to weight and cost

Cable routing and electrical functions added to a vehicle significantly impacts theoverall weight and cost of production. For example, researchers at G.H. Raisoni College of Engineering report an increasing demand for high-end luxury cars,which contain more than three miles and nearly 100 kg of wiring. The added electrical systems wiring forces electrical platform designers to make the best cost/weight/function trade-offs.

More electronic functionality layers on the complexity

The complexity of design and manufacturing is increased as E/E functionality increases. Today’s modern vehicles contain a large number of electronic modules inside realise a substantial number of functions, and these functions may be distributed among several electric control units (ECUs). Premium cars can have as many as 70 ECUs that are connected to five system busses, realising more than 800 functions. This complexity can cause unanticipated problems such as sneak circuits: where particular combinations of switches and loads can cause the inadvertent operation, or disablement, of an electrical function. This can have a range of outcomes,from bewilderment of the driver to more serious outcomes such as loss of a safety-critical function.

Overwhelming configuration variability

The car is the most sophisticated consumer electronics item available today. Configurations in electrical systems are exploding with the many features offered to customers to raise value and the need to meet safety, reliability, and emissions legislative requirements.

Every step along the electrical design process is multiplied with each configuration. Engineers are presented with a set of requirements associated with the overall platform to be decomposed through several stages; first, into individual features and, then, the functions that implement the features. Those functions are clustered into systems and allocated to physical devices or software. The embedded software in today’s modern automobile can be as much as 100-million lines of code. Then logical designs are associated with a mechanical definition of the overall vehicle and interconnected with a physical wiring system, which is ultimately partitioned into harnesses. Each individual platform configuration has its own unique harness, which can translate into thousands, even millions, of harnesses.

This configuration explosion affects the entire data flow from requirements to service documentation. Once sold, original equipment manufacturers (OEMs) are responsible for enabling efficient vehicle servicing across its life. Laws are increasingly demanding that this data, specific to each unique vehicle configuration, be available to all dealers (not just the OEM network).

Managing design changes

Historically, each stage of vehicle design has been an “island” with its own design tools and a complex local dialect that describes the components, inputs, and outputs of the particular stage. Communication has often been cumbersome, requiring conversions and/or manual data re-entry as the input to each step, resulting in redundancy and delays. These methods simply cannot meet today’s time, cost, and competitive pressures. Electrical design engineers need to be able to share information with each other and with other “islands” to improve cross-team and cross-discipline communication. They need to be able to more easily understand the context and effects of changes so that they can be implemented faster and with fewer misunderstandings.

Slow and steady will no longer win the race

Today’s cycle time is too slow to compete effectively and meet demand. The process of creating a detailed wiring design from the higher-level system design is repetitive and time-consuming, adding months to the design cycle. The issues discussed here are increasing design and manufacturing cycle time while competition is increasing the pressure to build the ideal electrical system faster.

Systems engineering manages complexity better

This increasing electrical content coupled with legislation and supply chain challenges are giving impetus to process change. Systems engineering can offer relief to those overwhelmed by modern vehicle development. Substantial evidence shows the effectiveness of the systems engineering paradigm in managing complexity, with several key characteristics: holism, abstraction, progressive integration, and interconnection.

Holism means that a problem is viewed in its entirety rather than as a set of isolated activities. In the vehicle E/E context, this means linking engineering domains as diverse as embedded software design, electronic component design, electrical distribution system design, and mechanical design.

Using this approach, data at a high level of abstraction is progressively decomposed and enriched to lower abstractions until buildable components (software blocks, electronic components, and wire harnesses, etc.) become fully defined. These components are then progressively integrated, with repeated verification steps until the complete system is assembled. Transitions between abstractions can be automated through machine executable specifications (a process known as synthesis), while full traceability is maintained, from requirement to component implementation.

Systems engineering characteristics include:

  • Consideration of whole problem (multidisciplinary)
  • Navigation through multiple abstractions, ideally via machine-readable executable specifications
  • Importance of requirements
  • Concrete verification procedures
  • Emergent behaviour from integration of sub-elements.

Typically, disciplines have their own work cycle that represents the project life cycle development from their own view. This has made dealing efficiently with configuration variability, requirements, electrical systems complexity, and design changes challenging.

Digital continuity and design automation are crucial to success

The Mentor Graphics Capital tool suite enables this approach and fits well into the systems engineering paradigm. It can be integrated easily with each manufacturer’s design and build systems, tools, and processes. It delivers a whole systems view of the electrical design process, providing platform-level abstraction that:

  • Enables engineering choice, simulation, checking, and other tasks to be undertaken in the context of the overall vehicle;
  • Provides an integrated management environment that seamlessly matures data through multiple abstractions, facilitates design change management, and supports design asset reuse;
  • Uses configurable, rules-driven synthesis functionality that automatically transforms and enriches data as it progresses from one abstraction to another;
  • Features decision support and design verification capabilities; and
  • Includes support for all common approaches to electrical system configuration management, including composite supersets, feature-based configuration, and sequence-based effectivity.

Platform-level abstraction

The Capital tool suite uses a generative approach in which wiring designs are automatically generated from higher level inputs, allowing “correct by construction” design creation. The software can automatically generate accurate wiring designs for all allowable configurations at the platform level.

This approach enables manufacturers to capture and develop their competitive intellectual property. System integration is rapid, accomplishing in a few hours a task that would otherwise take weeks. This reduces electrical design times and costs while enabling the evaluation of alternative architectures. The tool suite is a complete electrical design package that fits into the larger ecosystem and is designed from the outset with an IT architecture that facilitates integration with MCAD, PLM, or ALM tools.

Early detection of problems

Easy-to-use simulation provided by the Capital tool suite means that designs can be tested before the hardware stage and a problem can be identified early, when it is less expensive to fix.

Harness development is a transition point in the vehicle design and manufacturing process. It’s the environment in which critical design data matures into a buildable product.

Manage complexity, avoid costly recalls and delays

Failure to recognise the special role that E/E systems play can lead to catastrophic results such as recalls and delays that cost manufacturers dearly. For example, the Airbus wiring failure in the A380 jumbo jet that led to significant profit loss could fundamentally be described as an inability to manage digital continuity and the flow of information between mechanical and electrical engineers, from concept to manufacturing to assembly. Implementing a systems engineering approach can help vehicle manufacturers maintain quality and profitability into the future.

For the full White Paper go to: http://go.mentor.com/39c88.

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