Flexible architecture facilitates features integration into electric power steering

April 25, 2012 // Christoph Hammerschmidt

Nexteer Automotive has developed an electronic architecture for its electric power steering (EPS) systems that will make integration of new electronic features faster and provide greater functional safety. The architecture gives car manufacturers a single, customizable 12-volt platform for all passenger vehicle types, from low-cost micro-cars to the highest-specification luxury SUVs.

The architecture will enable manufacturers to introduce complex steering functions, claims Nexteer. Bertram Moeller, Network leader Systems Engineering Europe, Nexteer Automotive elaborated: "Instead of using standardized architectures for different vehicles classes, Nexteer's single, flexible architecture adapts to suit individual customer requirements and future-proof platforms. The architecture also allows us to provide more power to the EPS, so that it can steer any passenger vehicle using a standard 12-volt supply.”

Development of electrical architectures for EPS is driven by a number of related factors. The introduction of new functional safety standard ISO 26262 is a major driver with compliance made more important after recent high-profile competitor product recalls. The introduction of the Autosar standardized software architecture also increases CPU memory requirements. At the same time a rise in the number of more complex functions, such as lane-keeping assistance, where multiple systems communicate, has increased the need for new communication structures, such as dual CANbus and FlexRay.

Whereas a few years ago, customer specification sheets contained just two or three steering functions, a list of 20 is now common. To provide the substantial increase in processing power needed, Nexteer is using a new family of ISO 26262-compliant dual-core processors scalable in memory to 10 times than today with much higher processing speed. The first full implementation of the new electrical architecture enters production in 2013.

Steering, along with the brake system, is a safety-related vehicle system. It is also the primary interface with the vehicle and road surface. Nexteer's in-house software expertise enables it to deliver complex functions based on electronic control of the motor and its diagnostics that improve the driving experience and vehicle performance.

"Functions such as pull compensation, which keep the steering straight on crowned roads, and wheel imbalance rejection, which filters uncomfortable wheel vibrations, have significantly reduced warranty issues for Nexteer customers,” added Moeller. “The new architecture provides the processing power, functional safety, robust vehicle communication and standardized software required to introduce further functions such as lane-keeping assistance that coordinate with other vehicle systems. This intelligent approach will make it simpler for OEMs to offer customers new functions throughout vehicle lifecycles.”

The new architecture is widely scalable. At the entry level, a simplified control platform offers a low-cost system for economy cars and emerging markets, with the flexibility to add more sophisticated features for future models. For premium platforms, the modular nature of the architecture allows a high level of feature flexibility to enable a wide range of options and a development path into the future.

The introduction of the new architecture will integrate compliance to the ISO 26262 standard into Nexteer's core development process and hardware design, making the development of new functions and the fulfillment of customer requirements faster.

For more information, visit www.nexteer.com

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