Steer-by-wire (SbW) systems are a modern approach in automotive steering technology that replace traditional mechanical connections with electronic controls. This system utilizes sensors and actuators to manage steering inputs, allowing for precise control without the need for physical linkages. SbW systems offer several advantages, including the ability to adjust the steering ratio based on driving conditions, which can enhance maneuverability in urban settings and stability at higher speeds.
In the automotive industry, SbW technology is being integrated into various vehicle types, particularly in the luxury and upper midrange segments. This technology supports the growing trend toward electric and autonomous vehicles, where advanced steering solutions are necessary for improved vehicle dynamics and safety. Additionally, SbW systems can facilitate innovative cockpit designs, as the absence of mechanical components allows for more flexibility in vehicle layout.
Emerging trends indicate that SbW technology will see increased adoption across different vehicle segments by 2035, driven by advancements in electric-vehicle technology and the need for enhanced driver assistance systems. The automotive market is expected to capture a significant share of SbW systems, particularly in regions such as Europe, China and the US, which are at the forefront of these developments.
To learn more, we spoke to Stéphane Cassar, vice president steer-by-wire & core development, ZF.
Key takeaways:
- Flexibility and compatibility: ZF’s cubiX software is designed to be hardware-agnostic, making it adaptable for various architectures, including traditional distributed systems and centralized domain ECUs. This adaptability enables its application in diverse vehicle systems, such as brake control units and potentially in simpler microcontroller units for systems like power steering and semi-active dampers.
- Enhanced vehicle functionality: The transition to centralized electronic control units, facilitated by cubiX, allows for improved coordination of vehicle functions such as steering and braking. This holistic approach enhances ride comfort, dynamic handling, and safety while reducing application costs and development time through centralized tuning.
- Challenges in SbW implementation: Implementing SbW systems involves significant technical complexity, including the need for advanced control algorithms and robust safety measures to ensure reliability. The development costs associated with sensors, actuators and extensive testing are considerable, alongside the challenge of gaining driver acceptance as the driving experience evolves.
- Market adoption and future trends: SbW technology is expected to initially penetrate the luxury and upper midrange vehicle segments, with projections suggesting it could capture around 5 percent of the automotive market by 2030. Regions such as Europe, China and the US are leading in the adoption of this technology, driven by advancements in electric and autonomous vehicles.
The following is an edited transcript of the conversation.
S&P Global Mobility: Can your cubiX software operate exclusively with a chassis domain controller?
Stéphane Cassar: One driver for the development of cubiX is the trend toward centralized architectures in vehicles. Nevertheless, it was clear from the outset that traditional, distributed architectures would remain in the market for a transitional period. For this reason, cubiX was designed to be used in both distributed architectures and domain [electronic control units]. Use in a zone control unit is also possible. In our first production application, for example, the cubiX software runs on the ECU of the brake control system.
Are there specific hardware or base software requirements necessary for running cubiX?
CubiX was developed to be hardware-agnostic. This means that cubiX is highly adaptable both in terms of the actuators to be controlled and the host.
Of course, the ECU must provide the necessary memory space and meet the necessary safety integrity requirements. Last but not least, a sufficiently fast bus connection to the connected chassis actuators is required.
An Autosar environment simplifies integration but is not a requirement. We already have experience with a proprietary interface to the base software in an application project.
Is it feasible to integrate cubiX into a simple MCU that could be installed in power steering systems, ESC units, or semi-active dampers?
Yes, if the control unit meets the requirements, it's not a problem. The mentioned series application in the brake control unit is a good example of this. A semi-active damper ECU might be a bit undersized.
What are the key advantages of using cubiX in automotive applications?
What will change in terms of the software defined vehicle is that more functions will move from the actuators to central electronic control units. For example, in the steering or braking system they will be moved to a central ECU. This trend will accelerate in the coming years. Based on sensor data from the entire vehicle, the vehicle motion control software, cubiX, coordinates steering system, brakes, semi- or active damping, chassis and drive actuators as a holistic system. This optimized networking of the individual actuators results in new functions that increase not only the ride comfort but also the dynamic handling and safety of the vehicle. Also, this leads to a reduction of application cost and time saving through easy, central tuning to original equipment manufacturer DNA. This scalable system is based on a modular design that enables it to be adapted to a wide range of OEMs’ requirements from performance drive, AD [automated driving] and ADAS as well as full VMC [vehicle motion control] safety system and commercial vehicles.
What are the primary challenges associated with implementing a SbW system? Are these challenges mainly linked to cost, regulatory requirements, technical complexity or other factors?
Implementing a SbW system comes with several major challenges. One of the main challenges is technical complexity, as SbW systems replace the mechanical connection between the steering wheel and the wheels with an electronic controller. This requires advanced control algorithms to guarantee precise and reliable steering in various driving conditions, while providing accurate feedback to the driver.
The safety and reliability of SbW systems are also of paramount importance, as the system must be fail operational, i.e. it must function safely even in the event of a failure. This includes the development of robust, fault-tolerant architectures as well as redundant systems to ensure steering functionality in case of failure and enable the driver to control the vehicle in certain conditions defined by standards.
The development and implementation of SbW systems therefore require some effort, including the cost of advanced sensors, actuators and ECUs, as well as the cost of extensive testing and validation to ensure safety and compliance.
Finally, gaining driver acceptance can be perceived as a challenge as SbW systems transform the traditional driving experience and replaces traditional mechanical linkage with electronic ones. The experience must be seamless, inspiring trust and enhance the driving experience.
How can a supplier effectively persuade OEMs to transition from traditional electric power steering (EPS) to a SbW system? What key benefits or value propositions would resonate most with them?
From the end customer or driver's point of view, SbW offers several advantages and transforms the driver’s experience within meters. Compared to traditional steering systems, such as EPS, a SbW system adapts the steering ratio individually so that the ratio of the steering wheel angle to the wheel angle is optimally adapted to different driving speeds or situations. When parking or driving in town, steer-by-wire makes steering more direct; a simple half-turn of the wheel can be enough to turn the wheels to the maximum. At high speeds, steer-by-wire makes steering less direct: You no longer need to be very measured in your steering movements to guarantee good stability; the trajectory becomes more comfortable, precise and stable.
In addition, the steering can be individually adjusted from sporty and direct to comfortable and relaxed. However, SbW also enables the use of new, more compact steering wheels, where drivers no longer have to cross hands on the steering wheel while parking or driving.
For OEMs, SbW also offers the advantage of eliminating the mechanical link between cockpit and front axle. This opens up new design possibilities for innovative cockpits. Steer-by-wire transforms the driving experience, even when stationary. It also offers immediate benefits for passive safety. Last but not least, with no mechanical links and a software-variable steering ratio, a single set of steer-by-wire actuators (front axle actuator and torque feedback actuator) can equip several models on the same platform, eliminating the need for numerous mechanical variants previously necessary for the OEM.
Is there a specific target vehicle segment for SbW systems, such as luxury or autonomous vehicles? Or do you foresee SbW technology being adopted across all vehicle types in the near future?
The SbW steering innovation is electric, intelligent, software-based and interconnected — like the cars of future generations. This makes steer-by-wire a groundbreaking system component of tomorrow's mobility and a system that seizes the opportunities of industry transformation. ZF makes it as easy as possible for vehicle manufacturers to switch to steer-by-wire technology. ZF has developed SbW as a scalable and modular system. This means that it meets the requirements of various markets and customers.
While the upper midrange, the luxury segment and SUVs will probably be the first vehicle segments in the first phase of the SbW market launch, the technology will also find its way into the other segments in the future.
What percentage of the automotive market do you predict SbW systems will capture by 2030 and 2035? Are there particular regions or markets that are leading in the adoption of this technology compared to others?
SbW systems are projected to take an increased share of the global automotive market by 2030 — it is expected to reach approximately 5 percent. By 2035, this growth is anticipated to continue, driven by the increasing adoption of electric vehicles and advancements in automotive technology. In terms of regional adoption, Europa, China and USA are leading the way. These regions are at the forefront due to their strong automotive industries and significant investments in electric and autonomous vehicle technologies.
