GM backs its hybrid vehicles in spite of losses

　　General Motors, racing to bring hybrid vehicles to market faster, is turning to simulation to lop weeks off the time required to design and develop software control systems for hybrid powertrains.

　　And it goes beyond hybrids. GM is using technology known as model-based design from MathWorks Inc., of Natick, Mass., to develop software control systems for all new GM powertrains around the world.

　　This software, called Simulink, allows GM to simulate the control system for any GM powertrain before committing to the hardware.

　　"I don't think you could do a hybrid control system without model-based design and development," said Kent Helfrich, director of software engineering in GM Powertrain. Hybrid powertrains are far more complex than those built around internal combustion engines and require sophisticated software controls.

　　Hybrid integration

　　"The name of the game in hybrid systems is integration," Helfrich told Automotive News. "You can't make an engine and a transmission separately anymore and then integrate them at the last minute. This has to be conceptualized as a family, as a system. If the system isn't conceptualized well, your end product's not going to work very well."

　　The automaker used MathWorks tools to design and develop its Two Mode hybrid powertrain control system launched in January on the GMC Yukon and Chevrolet Tahoe SUVs. "

　　The Two Mode hybrid control system was done entirely in model-based design, Helfrich said.

　　"That really enabled engineers to do what they needed to do to ensure that the system actually worked, prior to even having hardware available," he said.

　　GM is reducing costs and taking weeks out of the development time of control systems for hybrid powertrains, he said. The automaker also is shortening its cycle time on design changes without affecting quality, he said.

　　"We can now do those iterations virtually, and then commit ourselves to hardware later in the design center," Helfrich said. "It saved us a lot of money in terms of eliminated prototypes and rework."

　　Helfrich declined to quantify the cost and time savings. "It's hard to quantify things that you didn't do," he said. "But we couldn't do it without this. So it's not really a cost avoidance in that it is the only way to achieve what we need to achieve in our integrated powertrain controls."

　　Chain of tools

　　GM is using the same model-based design in engineering centers around the world, he said.

　　"The key is having one tool chain and one software product line globally for all of GM powertrain engineering," Helfrich said. "That's kind of unusual."

　　Just as automakers build a variety of vehicle models on a single platform, Helfrich's team is making those same types of design and architecture choices at a software level, said Jon Friedman, manager of aerospace, defense and automotive industry marketing at MathWorks.

　　MathWorks' competitors in the market for control system design software tools include Wind River Systems Inc., of Alameda, Calif.; and Mentor Graphics Corp., of Wilsonville, Ore.

　　GM also has powertrain control systems that were developed before the availability of model-based design. "That means we've got an interesting combination of old software and new software coexisting," Helfrich said.

　　"But it's good because the old software's validated and high-quality and is in use in millions of vehicles worldwide. We don't want to replace that unless we absolutely have to."

　　Companies such as Toyota Motor Corp., Denso Corp. and Delphi Corp. also use MathWorks tools to provide a common platform for sharing system specifications and development ideas.

　　GM在混合动力汽车走向市场的角逐中显现出较快的势头，正转向此采用仿真方法设计开发混合动力总成的软件控制系统，这种方法可节省数周的时间。

　　且采用仿真方法不只局限于混合动力汽车。GM现在使用业内熟知的基于模型的设计技术，为全球所有的新型通用汽车动力总成开发众多的软件控制系统，这项技术由位于马萨诸塞州纳提克郡MathWorks公司提供。

　　GM可以使用这种名为Simulink的软件在应用于其硬件之前模拟任一GM动力总成的控制系统。

　　GM动力总成软件工程主任Kent Helfrich说：“没有基于模型的设计与开发工具就不可能开发出混合动力控制系统”。混合动力总成远比那些围绕内燃机构建的动力系统复杂得多，并且需要先进的软件控制。

　　Helfrich向Automotive News讲述说，“混合动力系统的实质是整合。不能再单独制作引擎和传动系统，然后在最后时刻两者进行整合。这必须要当作一个关系密切不可分的、或系统的概念来看待。如果这一系统没有很好的概念定义，那么最终产品也不会运行的很好。”

　　GM使用MathWorks工具设计开发其双模式（Two Mode）混合动力总成控制系统，该系统于1月在GMC Yukon 车型和 Chevrolet Tahoe SUV车型上开始使用。

　　Helfrich说：“双模式（Two Mode）混合动力控制系统是完全采用基于模型设计的方法设计的。”

　　“这使工程师真正做他们分内的工作，确保系统实际运行，甚至在不提供硬件之前也可以这样做。”

　　他说：“GM正在降低成本，混合动力总成控制系统的开发时间将减少数周；公司也正在不影响质量的前提下缩短设计变更的周期。”

　　“通用汽车在世界各地的工程中心都在使用相同的基于模型的设计方法。”他说。

　　Helfrich没有给出节省成本和时间的具体数字。他说：“没有做的事情是很难量化的；但不用这个（设计系统）就无法做。这个系统实质上不是为规避成本，而是一种要获得整合动力总成控制中所要达到的结果的唯一方法。”

　　“对于所有的通用汽车动力总成工程而言，关键是有一个工具链和一个覆盖全球的软件产品线，” Helfrich说。“这是与众不同的。”

　　MathWorks公司的航空航天、国防和汽车工业部门的营销经理Jon Friedman说‘正如众多的汽车制造商在一个平台上构建各种车型一样，Helfrich的团队在软件平台上对那些设计和构架类型相同车型做出选择”。

　　在控制系统设计软件市场上，MathWorks的竞争对手有加利福尼亚州阿拉米达的风河系统公司和俄勒冈州威尔逊的Mentor Graphics公司。

　　GM也有动力总成控制系统，这个系统是在使用基于模型的设计之前开发的。Helfrich说：“这意味着我们旧软件和新软件同时结合使用已引起专注。”

　　而且效果很好，因为旧软件仍然有效、质量好并用于世界各地数百万车辆。除非万不得已，我们不想取代它。

　　像丰田汽车、日本电装和德尔福这样的公司也使用MathWorks工具，从而为共享系统规范和开发理念提供了一个共同平台。