As vehicles employ more electronic systems, design teams will have to take a system-wide approach to design to get to market quickly without sacrificing reliability. More powerful design tools, faster microprocessors, and software standards are a few of the tools that will help make a systems approach possible.
Addressing all aspects of a system design will help improve efficiency by improving synergy between different subsystems. Panelists who discussed vehicle architectures during SAE's Commercial Vehicle Engineering Congress & Exhibition in Rosemont, IL, in early October agreed that both tool providers and system developers need to move to a more holistic environment.
“In an ideal platform, you want to merge system and control engineering efforts,” said Rongjun Zhang, Oshkosh. “You also want to share one simulation environment. You don’t want to go from one environment to another.”
Modeling and simulation are a central part of many new designs, continuing an evolution that has gone from assembly language to C code to model-based design. The next step expands to a broader view of the vehicle.
“To better deal with growing software complexity, we now have to go from the component level to an architectural level, looking at a systems and software architecture,” said Dirk Fleischer, a North American Product Manager at dSPACE.
Engineering teams that have moved to model-based design will see several changes, including an increased focus on doing more up-front planning and trying to find problems as early as possible. Making the change usually saves money long term by reducing errors, but the benefits do not come free.
“When you do modeling and simulation, there’s an upfront effort,” said Sameer Prabhu, Industry Marketing Manager, The MathWorks. “If you’re starting to use those tools today, you should focus on the most painful aspect of a design; then it’s easier to get management’s attention.”
Modeling and simulation may cost more at the beginning, particularly when product specifications are being written. But the payoff comes when errors are found earlier in the development process. Volvo engineers noted that errors that make it into the field and require warranty service cost most companies 1-3% of their margins.
When a growing number of ECUs communicate over networks, it is more important for hardware and software components to work together in a system context. “When two ECUs communicate over a bus, there’s a potential to generate more errors,” Fleischer said.
Making sure these components all work together requires much interaction between many different design environments. Vehicle designs are so complex that many design tools are used, making it difficult for design teams to share data. Though toolmakers continue to improve compatibility, data sharing remains difficult.
“Teams want to traverse different domains—thermal, mechanical, fluid dynamics—so they need to combine different tools,” said Prabhu. “There’s limited sharing. A hydraulic engineer may use one tool, a system engineer may not be able to use the same tool. We’d like to see an integrated modeling environment that covers multiple domains even for difficult problems like the bucket-soil interaction.”
The systems approach will also be important in cabins, where the human machine interface is undergoing a massive transformation. Given the number of functions that operators have to control, it is no longer feasible to design control modules as discrete components. The most productive work environments will include all aspects of the operator interface.
“You need to make the entire cockpit an HMI,” said Tim Newman, Senior Systems Engineer for Delphi Electronics & Safety. “There’s a real struggle for real estate in the cabin, and things like cameras for blind spots are often added on near the end of the design cycle. Engineers must design the whole environment, they can’t do it component by component.”
One way to isolate infotainment and more critical HMI software is with virtualization, which provides a way to isolate functions so a failure in one area cannot cause problems in another area. The HMI control stack and the infotainment control stack can run on separate virtual processors.
These virtual devices run on a single microcontroller, either a multicore device or a chip fast enough to run multiple tasks simultaneously. In virtual systems, these tasks are segmented to ensure that they will not corrupt each other, which is increasingly important as infotainment systems include consumer technologies that have not been tested to the rigorous reliability levels used for vehicle software.
Many of the panelists predicted that AUTOSAR will be one of the tools that simplify this systems approach. The standard lets programmers develop software that is independent from hardware, working with a top-down-design methodology in which the software architecture is set up before the hardware topology is defined.
The two toolmakers, dSPACE and MathWorks, support the standard with many products. On the vehicle side, Volvo expressed strong support. AUTOSAR will soon make its way onto trucks with a new electronics platform that currently is being tested and verified.