Simulation provides key to explosive automotive design challenges

6 Pages·0.648 MB·English

by  Teegarden D.A.

SimulAtion ProvideS Key to
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Simulation Provides Key to explosive Automotive design Challenges
ABStrACt
Not only has the typical system design grown in overall size to accommodate ever-increasing demands for
functionality and performance, but these designs must fluently integrate analog and digital hardware, as well as
the software that controls it. Successfully integrating and verifying that system components work in concert with
each other often proves to be costly in terms of time, money and engineering resources. And, at the same time,
there is increased pressure to reduce development cycle time. In order to keep pace with these new realities, new
processes and development tools are required. In particular, the development and intelligent use of computer
models of these complex systems—once considered a luxury—are becoming critical to the success of the overall
development process.
introduCtion
Today’s automotive challenges are similar to those experienced in the telecommunications industry more than ten
years ago. New technologies, such as hybrid-electric and fuel cell vehicles, are hotbeds of research and
development activity comparable to what we saw during the evolution of cell phones into multimedia devices. In
the same way that the telecomm industry faced power and chip size limitations, automotive designers are being
stretched to include more and more technology into what used to be basically a mechanical device.
Electronic, electrical, mechanical, hardware, and software components and the networks that connect them are
densely populating vehicle designs to an ever greater degree. The amount of in-vehicle electronics, currently at
40%, is on the rise with an ever increasing number of electronic control units (ECUs) being distributed across the
system to control sophistication and complexity of new applications. ECUs can have hundreds of software
components; multiplexing among systems is proliferating; and communication requirements are escalating. The
system integration phase is a frequent bottleneck. The very nature of distributed systems--wherein data comes
from different internal resources, ECUs come from different companies, and algorithms from different ECUs must be
synchronized—requires heavy coordination.
Not only has the typical system design grown in overall size to accommodate ever-increasing demands for
functionality and performance, but these designs must fluently integrate analog and digital hardware, as well as
the software that controls it. Successfully integrating and verifying that system components work in concert with
each other often proves to be costly in terms of time, money and engineering resources. And, at the same time,
there is increased pressure to reduce development cycle time.
In order to keep pace with these new realities, new processes and development tools are required. In particular, the
development and intelligent use of computer models of these complex systems—once considered a luxury—are
becoming critical to the success of the overall development process.
ComPuter SimulAtion Key to deSign ProCeSS
Computer simulation (or just “simulation”) is generally recognized as a tool to help automate the design of a
particular aspect of a system. Using specialized algorithms to analyze a model of a system, it provides the ability to
successively verify new designs from concept to implementation. When employed during the beginning of the
design process, simulation provides an environment in which a system can be tuned, optimized, and critical
insights can be gained – before any hardware is built. Useful for many reasons, perhaps the most obvious use of
simulation is to “virtually test” the system model in order to reduce the risks of unintended behaviors—or even
outright failures—in the actual system.
In order to create a system model, each component in the real system needs to have a corresponding “component
model” (although it is often possible to combine the function of multiple components into a single component
model). These component models are then connected together (as would be their physical counterparts), to create
the overall system model. What lies at the heart of any computer simulation, therefore, are the component models.
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Simulation Provides Key to explosive Automotive design Challenges
The “art” of creating the models themselves, and sometimes more importantly, of knowing exactly what to model
and why, are the primary keys to successful simulation.
To create an overall system model out of the component models, you can generate a graphical symbol for each
component model and then connect the pins of the symbols using a schematic capture environment. It is also
possible to construct the system model without a schematic capture environment, by creating a netlist or
testbench using a text editor. The next step is to parameterize the component models, if necessary (typically via
their corresponding symbols). A generalized motor model, for example, may be given explicit parameters so it will
behave as a specific type of motor.
With the system model complete, various simulations can be performed to determine the overall system
performance. To actually debug a real system, several simulations would be performed throughout the design
process and beyond. Example results for both time-domain as well as statistical analyses are given in Figure 1.
Figure 1: Typical system simulation results.
Figure 1 illustrates how simulation-based “virtual testing” can be used to test basic system functions, as shown by
the mixed-analog/digital waveforms in the upper-left quadrant of the figure. It also shows how virtual testing can
be taken to the next level by performing a Monte Carlo analysis and generating scatter plots and histograms that
help correlate performance measures to various component parameters. These are shown in the upper-right and
lower-left quadrants of the figure. Finally, the sensitivity of various performance measures to specific components
can be determined using Sensitivity Analysis, results of which are shown in the lower-right quadrant of the figure.
All of these analyses and more are available once a system model has been developed.
A possible next step is to consider “upgrading” various component models to account for the eventual physical
implementation of the system. After determining that the topology is indeed sound, a choice is required: build the
actual design, or increase the value of the system model even more to reduce risks in the physical system later.
However, it is possible to do both concurrently.
Modeling overall system variation helps prevent designers from optimizing a component at the expense of the
system. For example, the ripple effect of reducing the cost of one component, perhaps by loosening its tolerance,
may ultimately require a more expensive modification to another component, to compensate for overall variation.
By understanding this impact, this change can be rejected before it becomes irreversible.
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Simulation Provides Key to explosive Automotive design Challenges
With a system model available, “what-if” tradeoffs can be made, performance as a function of component
tolerances can be determined, and many other analyses can be performed. This is the pay-off for the model
development effort. The system model can be used now to anticipate and fix any design issues – before actual
hardware is built.
reSolving the gAP from SimulAtion to PhySiCAl
PrototyPing
Part of the “art” of designing a system is to be able to make the transition from simulation model to physical
prototype at some reasonable point in the design process. Some designers jump as quickly as possible into “real
hardware” and may even forego the use of simulation as a tool altogether. Others tend to put off building the
physical system as long as possible and continue refining the system model. Where should the line be drawn? It
really depends on the amount of risk that is acceptable for the specific design. For safety-critical systems and sub-
systems, highly-refined system models are often used in conjunction with physical prototypes to minimize risks.
On the other hand, non-critical systems do not need to be so rigorously developed, but they still benefit from the
development and simulation of corresponding system models. Such models can help minimize system
performance degradation due to part tolerances stemming from manufacturing variability. Part costs can be
minimized as well. Additionally, having access to a simulatable system model can help to improve overall system
robustness and foster a better understanding of the system in general.
For example, designers can simulate a system operating at excessive voltage or temperature levels, or view current,
flux and other state variables internal to a device. Another example is the ability to exercise an embedded
controller running in the context of its hardware peripherals (e.g. A/D, D/A, timers, etc.). This is similar to using an
in-circuit emulator in the real world, but, in the virtual world, the user can actually stop time at a breakpoint, not
just stop the execution of the code.
The challenge lies in resolving the gap that exists between hardware and software across the stages of design.
Designers need a tool capable of virtual modeling and integration that enables true electronic systems design and
analysis. Such a tool would not only support functional modeling of electronic systems but also virtual integration
and simulation of combined hardware and software to properly verify that the system requirements are met. This
tool is available today in SystemVision from Mentor Graphics.
SystemVision is a design and analysis tool suite comprised of three integrated tools: a schematic capture program, a
mixed-signal simulator, and a waveform viewer. SystemVision also integrates with other tools used for advanced
analytical functions in today’s design flows. SystemVision provides an intuitive and easy-to-use virtual modeling,
simulation, and system integration environment that supports multiple levels of system abstraction across multiple
engineering technology domains. Analog, digital, and mixed-signal circuits can be abstracted and analyzed along
with mechanical, electrical, thermal, and hydraulic systems, along with continuous and sample-data control
systems (and many other engineering effects) in an environment that allows for the fluent, multi-level integration
required for true electronic system-level design and analysis.
Using SystemVision, engineers can quickly and easily create and analyze designs that include all levels of
abstraction from math-based behavior down to circuit implementations. SystemVision can be used as a numeric
analysis engine, providing a very high level of modeling fidelity that helps pinpoint problems through waveform
display of signals, amplitudes, and timing. In this environment, high-level behavioral models can be combined with
lower-level device and effects models, allowing designers to rapidly examine design tradeoffs.
The SystemVision core includes a single-kernel engine that ensures accurate mixed-signal simulation results. The
simulator core accepts multi-language system and circuit descriptions and generates viewable waveforms in a
technology-aware format. Block diagrams and transfer function blocks assist designers with high-level concept
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Simulation Provides Key to explosive Automotive design Challenges
verification. Hierarchical schematics and circuit elements assist them in verifying electronic and mechatronic system
designs.
Figure 2: SystemVision provides powerful design, modeling, analysis, and viewing tools around a core simulation engine.
SystemVision technology gives designers powerful tools for managing mechanics, electronics, software, and
controls all in one system with the capability to integrate the significant intersections between them. Figure 3
illustrates how certain design parts inhabit the intersections of the multiple design domains that SystemVision can
address. For instance, sensors and actuators inhabit the intersection of mechanics and electronics, control circuits
inhabit the intersection of controls and electronics, and microcontrollers inhabit the intersection of electronics,
controls, and software. Using SystemVision, designers enjoy a modeling environment that can handle all of these
disciplines simultaneously.
Figure 3.
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Simulation Provides Key to explosive Automotive design Challenges
During the verification phase of the design, simulation technologies can again be employed to verify intended
system operation. It is a common mistake to completely design a system and then attempt to use simulation to
verify whether or not it will work correctly. Simulation should be considered an integral part of the entire design
phase and continue well into the manufacturing phase.
Virtual system-level integration and verification, with ties back to the original executable specification, is primarily
an exercise in providing a rich tool integration environment. System integration can begin before physical hardware
is available by creating a system model that incorporates a combination of the various technologies. This may
include the mechanical, magnetic, hydraulic, thermal effects or any other technology that can be described using
algebraic or differential equations. Though obviously of high value, these benefits will only accrue for automotive
system design when a large number of designers working at the system and component levels, and across the
spectrum of engineering disciplines, begin to use system modeling techniques.
darrell A. teegarden, System modeling and Analysis Business unit director
[email protected]
Please direct any questions or enquiries to
James Price, Automotive marketing manager
[phone]
[email protected]
or contact your local sales representative
www.mentor.com/automotive
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