Under the concept of MaaS (Mobility as a Service), the automotive industry is undergoing a transformation like never before. Steering system technology is evolving from traditional power assistance to supporting autonomous driving and advanced driving assistance functions. As a global leader in steering systems, XEPS has decades of experience in steering technology. For several years, XEPS has been developing and refining advanced steering technologies for autonomous driving. Based on the wide adoption of Electric Power Steering (EPS), XEPS has developed core technologies such as functional safety and Steer-by-Wire (SBW) and provides dedicated solutions for commercial vehicle autonomous driving. This article will review the evolution of steering system technology, key technological breakthroughs under autonomous driving and future development directions, and XEPS’s technical layout and practical exploration in intelligent mobility including various forms of steering system and HMI technology solutions.
Evolution of Steering Systems: From Mechanical Assistance to Electrification
The development of automotive steering systems has always been centered on maneuverability, comfort and adaptability, closely tied to vehicle adoption and market demand.
By the late 1960s, the rapid growth of passenger vehicles in Japan exposed the limitations of traditional mechanical steering, leading to the practical implementation of Hydraulic Power Steering (HPS) which provided drivers with lighter and more comfortable steering. As vehicle usage expanded and demand for light vehicles surged—driven by second-family cars and a rising proportion of female drivers—the limitations of HPS became apparent, particularly in light vehicles, creating a need for new power steering technologies. Notable milestones in steering system innovation include the introduction of HPS, speed-sensitive steering and early electric assist solutions.
In 1997, XEPS achieved a breakthrough with Column Electric Power Steering (C-EPS) for mass production, solving light vehicle steering requirements. EPS also offered fuel economy benefits, aligning with environmental protection needs, and quickly expanded beyond light vehicles to various passenger cars. To meet mid-to-large vehicle demands, XEPS developed Dual Pinion EPS (DP-EPS) and Rack Parallel EPS (RP-EPS) products—different forms of electric power steering technology—extending the technology to buses, MPVs and other non-passenger vehicles, driving global EPS adoption and making XEPS a leader in the steering system industry.
Autonomous Driving Era: Industry Background and Steering System Role
In recent years, the automotive industry has moved from “vehicle manufacturing only” to comprehensive mobility services, aiming to create a safe, reliable and efficient intelligent mobility society. Public transport is a key component of Mobility as a Service (MaaS) solutions, allowing users to combine public transport with other modes for urban mobility. This is changing the way customers access new and innovative mobility services and options.
The CASE technology cluster (Connected, Autonomous, Shared, Electric) is the path to this goal and is getting global attention. Network connectivity is crucial in CASE, enabling advanced mobility services through integration with broader networks for data access and control. This cluster supports various mobility services including private cars, rental fleets, public transport, taxi and shared vehicles.
Two Dimensions of Autonomous Driving Technology
XEPS categorizes the core technologies of autonomous driving society into two:
Autonomous vehicle technology, focusing on vehicle perception, decision making and execution, requires collaboration among sensor suppliers, OEMs and actuator suppliers. These are the foundation of driving automation, defining how vehicles move from basic driver assistance to higher levels of autonomy.
Autonomous driving applications, which leverage vehicle technologies to provide various mobility services including private cars, rental fleets, taxis and three-wheelers, involves cross-industry mobility service providers. The development and deployment of these technologies also requires human interaction among stakeholders to ensure safe and efficient integration into real-world scenarios.
This division and integration of technology is the fundamental ecosystem of autonomous driving society. Together these technologies operate within defined domains to enable the autonomous driving ecosystem.
Autonomous Driving Levels and the Role of Steering Systems
Automated driving is deployed in a stepwise manner, aligned with societal demand, regulatory standards and technology maturity. Automated driving is defined by regulatory standards and safety evaluations, with each level specifying the level of system and driver responsibility. Based on SAE J3016, Level 2–Level 5 driving automation is defined as:
Level 2 (Partial Automation): Driver-led with software backup; widely applied today. Key ADAS features at this level include lane-keeping assistance, forward collision warning and automatic emergency braking which helps to keep the vehicle safe within lanes and at appropriate speeds.Level 3 (Conditional Automation): System-led with hardware redundancy. These systems can operate under certain conditions, such as specific environments or traffic scenarios, allowing the driver to temporarily hand over full control but require the driver to be ready to take back control if needed.
Level 4 (High Automation): Requires full hardware redundancy including power supply. At this level the system can operate autonomously under certain conditions and in defined environments, allowing the driver to hand over full control to the vehicle. This is the emergence of the fully self driving car which can control all driving tasks without human interaction in its operational domain.
Level 5 (Full Automation): Full driverless operation across all scenarios. The vehicle functions as a driverless car, with no need for human interaction or intervention, and the system assumes responsibility for all driving tasks in any environment. The driver hands over full control and the vehicle can operate at various speeds and across all lanes, regardless of conditions.
As automation levels increase, the steering system’s role transforms from power-assisted steering to a core component supporting automated driving by controlling the vehicle during all relevant driving tasks. As a leader in the “execution” domain, XEPS focuses on functional safety, SBW, HMI and vehicle dynamics integration, developing dedicated ADAS steering systems for commercial vehicles and establishing a full-scenario technical framework. System performance is often measured by distance traveled between disengagements and safe operation depends on the system’s ability to operate reliably at different speeds and in various environments.
Functional Safety: The Core of Autonomous Driving Steering Systems
Steering systems are safety critical components and their reliability defines the safety baseline for autonomous driving. Functional safety systems are increasingly monitored and managed through a secure network, enabling real-time diagnostics and remote updates. As automation levels increase, functional safety requirements evolve from fail-safe shutdown to fail-operational capability where the system must continue to operate safely even in the event of a fault, driving high-redundancy system designs.
EPS Functional Safety Requirements
EPS as the core of electric steering must comply with ISO 26262 automotive functional safety standards. ASIL-D, the highest safety level, identifies two critical failure modes:
Unintended steering (self-turning)
Steering lock
Since 2008, XEPS has implemented a comprehensive functional safety program for EPS:
Embedding functional safety requirements in R&D and manufacturing stages, ensuring full-process quality control.
Selecting low-failure-rate electronic components to maintain failure probability within safe thresholds.Dual-core microprocessors to monitor system performance; any fault detected triggers a fail-safe mechanism.
These measures ensure zero ASIL-D critical failures in XEPS EPS products. XEPS EPS systems have covered millions of kilometers without a single ASIL-D critical failure, proving high reliability.
SBW Systems: Steering without Mechanical Connection
Steer-by-Wire (SBW) is a revolutionary concept in the autonomous driving era. Various forms of SBW have been developed for different vehicle types, integrating advanced HMI interfaces and touch-based controls. By eliminating the mechanical connection between the steering wheel and the steering gear, SBW enables flexible control, introduces new types of controls for both the driver and the system and allows for functional expansion, becoming a core solution for high-level autonomous driving.
SBW transmits steering commands via electric signals through a dedicated network that connects the steering column unit and steering gear.
SBW operates without mechanical linkage, relying entirely on electronic communication and software to manage steering functions.
SBW vs. Conventional Steering
Traditional EPS connects the steering wheel via a mechanical shaft to the wheels, limiting precision in autonomous scenarios and preventing isolation of unsafe driver inputs. SBW overcomes this by transmitting control signals electrically, consisting of:
Haptic steering column unit (generates steering feedback)
Steering gear
The two communicate via electric signals. SBW can be implemented in different forms, such as fully electronic systems or hybrid setups, offering flexibility in design and integration.
Key benefits:
Adjustable steering feel for different driver preferences.
Support for non-traditional steering wheel designs, optimizing cockpit space and enabling new forms of controls, such as touch screens or advanced HMIs, for enhanced user interaction.
Steering wheel stowage during autonomous driving, enhancing comfort and safety.
HMI Steering Control Transfer: Human-Machine Collaboration
In high-level autonomous driving, control frequently switches between manual and autonomous modes. The steering system is the closest interface with the driver; smooth and safe control transfer is crucial for user experience and safety. Human interaction plays a key role in ensuring these transitions are intuitive and safe, allowing the driver to remain aware and engaged as needed.
Upgraded HMI Steering Requirements
Autonomous driving requires HMI steering functions beyond simple power assistance:
Hands-on/hands-off detection for precise driver state recognition.
Smooth control transfer between manual and autonomous modes.
Shared control without driver intervention.Drivers enjoy various forms of controls like touch screens and integrated HMIs for seamless interaction with vehicle systems.
Conventional torque-triggered lane keeping assistance (LKA) can abruptly interrupt autonomous control, compromising comfort and safety, and may not provide the multiple HMI feedbacks that modern systems offer.
Passenger Car Autonomous Steering: Real-World Applications
Passenger cars prioritize steering precision, response speed and comfort for autonomous driving. Traditional EPS is good in manual mode but lags in autonomous execution and fine control. XEPS developed a high precision Steer-by-Wire EPS system with high performance actuators in the steering column to achieve real-time electronic steering control.
Operation logic: Autonomous control unit sends steering commands → actuator adjusts EPS steering angle → wheels respond precisely. For example, this system is used in sedans, SUVs and MPVs with advanced driver assistance features.
Key benefits:
High precision: Optimized actuator-gear interaction for better steering angle accuracy to maintain lane position and navigate lanes with high reliability.
Fast response: Shorten command-to-action latency to meet L2-L3 autonomous driving requirements across a wide range of speeds at which the system can operate.
Currently this system is used in sedans, SUVs and MPVs and balances driver comfort and safety. It can work in various driving conditions.
Conclusion and Future
The automotive industry is undergoing a historic transformation with rapid technological iteration and deep industry integration. XEPS as a global steering system leader is driving the upgrade from power assisted steering to autonomous driving assistance, leveraging global manufacturing strength to build a full-fledged technology system covering functional safety, SBW, HMI and dedicated passenger car solutions.
XEPS believes intelligent mobility cannot be achieved by one single company. In the future, it will deepen industry-academia collaboration and partnerships, accelerate technology deployment through flexible alliances and integration. The ultimate goal is to create a safe, reliable, convenient and environmental friendly intelligent mobility society, position XEPS as a key player in the society.
