Nexteer & Continental Joint Venture Company Develops ‘Brake-to-Steer' Technology for Autonomous Vehicles

author: FutureCar Staff    

CNXMotion, a joint venture between global auto supplier Continental and Michigan-based automotive motion control developer Nexteer Automotive, has announced the development of a new "Brake-to-Steer" (BtS) technology for autonomous vehicles or those equipped with advanced driver assist systems (ADAS).

The BtS technology adds another layer of redundancy by using a vehicle's electronic brake system to safely steer the vehicle while simultaneously controlling its speed. 

CNXMotion's BtS technology offers a cost-effective way for automakers to achieve a high level of safety in an autonomous vehicle by leveraging the vehicle's existing braking and steering systems. The joint venture company is also focused on development of electronic steering systems which are referred to as "steer-by-wire" systems.

Continental's joint venture partner Nexteer specializes in electric and hydraulic steering systems, including steering columns and driveline systems, as well as ADAS and automated driving technologies for OEMs around the world. Nexteer's automotive customers include BMW, Fiat Chrysler Automobiles, Ford, General Motors, Toyota and Volkswagen. 

These steer-by-wire systems use electronic controllers instead of hydraulically operated systems to steer a vehicle, which offers more precision, but more importantly the ability to integrate with other electronic vehicle motion controllers, such as those used for acceleration and braking in self-driving vehicles.

"Cross-domain functionalities such as Brake-to-Steer are enabled by, and housed on, existing hardware, like, eliminating the need for additional, costly components," said Hiren Desai, Head of Strategy, Autonomous Mobility and Safety, Continental North America. 

For autonomous vehicles, the steering system will be critical. It must include some level of redundancy in case anything goes wrong, especially in Level-3 and higher systems that won't rely on a driver to take over. 

In the event of an emergency, BtS technology can electronically control the steering of a vehicle even if it has no steering wheel, maintaining control until the vehicle can be safely pulled over or stopped.

How Brake-to-Steer Works

The BtS function is intergrated with the vehicle's Motion Control System (MCS), which acts as an intermediary between the vehicle's path planner (the automated driving system) as well as the actuators (steering, brakes and powertrain) to determine the best path forward.

BtS can activate the brakes to cause the vehicle to yaw and follow the curvature commanded by the vehicle's motion planner. The BtS functions are Integrated with a performance manager that checks the vehicle's intended path and compares it to the vehicle's ability to navigate it based on the upcoming curvature route. If the vehicle is unable to navigate the commanded path, the BtS system performs an alternative safety maneuver.

In the event that BtS needs to engage, it reacts in one of three ways. First, it checks to see if there is a safe path forward. If not, the BtS system performs a minimum risk maneuver, such as slowing and braking. If slowing the vehicle down isn't enough, the BtS can steer the vehicle to the side of the road or bring it to a complete stop.

"While steering traditionally manages the lateral control of a vehicle, Brake-to-Steer enables braking to contribute to lateral control as well," said Robin Milavec, Senior Vice President, Executive Board Director, Chief Technology Officer (CTO) and Chief Strategy Officer (CSO), Nexteer Automotive. 

The technology was originally developed for steering redundancy in Level 4+ autonomy that requires no human intervention. However Nexteer said the feature can be adapted to assist a driver in a vehicle equipped with ADAS that provides lower levels of automation, such as automatic lane keep assist and automatic emergency braking (AEB). 

"While steering traditionally manages the lateral control of a vehicle, Brake-to-Steer enables braking to contribute to lateral control as well," said Milavec. "When combined with advanced steering systems like Nexteer's High Availability Electric Power Steering or Steer-by-Wire, Brake-to-Steer gives an additional layer of redundancy – further enhancing the safety net."

Since the technology integrates with other vehicle systems, it can be added to existing vehicle hardware, such as Continental's MK C1 brake-by-wire system. The MK C1 integrates a tandem brake master cylinder (TMC), brake booster and control systems for anti-lock brakes (ABS) and electronic stability control (ESC) into a single compact unit. 

The CNXMotion joint venture between Continental and Nexteer was established in 2017. The company is headquartered in Grand Blanc, Michigan and focuses on R&D of motion control systems, including evaluation design and prototyping for the respective parent companies. 

Nexteer and Continental hold an equal 50-50% ownership in the joint venture. 

FutureCar Staff