Chassis Three-Axis Integration: The Next Phase of Intelligent Electric Vehicles
On December 2 this year, China officially released the mandatory national standard GB17675-2025 "Motor Vehicle Steering Systems — Basic Requirements", which will replace the current 2021 version starting July 1, 2026. One of the most closely watched changes in the new standard is
the formal inclusion of steer-by-wire (SbW) into the regulatory framework, along with the removal of the long-standing mandatory requirement to retain a mechanical connection between the steering wheel and the road wheels
.
In other words, as long as functional safety, redundancy architecture, and fail-safe strategies meet the required standards, the steering wheel and the wheels are allowed to be fully decoupled.
More importantly, this marks a shift in China's role in automotive standard-setting. Chinese OEMs are no longer merely adapting to foreign standards; they are beginning to co-author the rules for next-generation technologies. Among the companies involved in drafting the standard are NIO, Li Auto, XPeng, BYD, and Geely, alongside international automakers such as Toyota and Mercedes-Benz. Steer-by-wire is thus clearly defined as a shared next-generation direction for both the Chinese and global automotive industries.
Viewed together—from whether the technology can be deployed in production vehicles, to whether there is a clear regulatory framework, and ultimately to whether systems can achieve both Chinese and international certification—this progression signals something larger than steering alone. It points to
the next stage of fully by-wire chassis architectures and three-axis integration, with China actively build the construction of new standards for intelligent chassis systems.
We will take this seemingly engineering-heavy topic and break it down into three accessible questions: What is really changing in today's vehicle chassis? Why is the industry moving inevitably toward three-axis integration? And what does this shift mean for the future of intelligent electric vehicles?
1. From the "three major assemblies" to the "three axes": Redrawing the Chassis
In the era of internal combustion engines, the automotive industry traditionally spoke of the "three major assemblies": the engine, transmission, and chassis. With electrification, the powertrain's "three major assemblies" were redefined to battery, motor, and power electronics. In the context of chassis control, however, a new framework—one that aligns more closely with control logic—is gaining consensus: the three axes.
X-axis (Longitudinal): responsible for "moving forward and stopping safely."
This axis covers drive torque control, coordination between regenerative and friction braking, and various brake-by-wire systems.
Y-axis (Lateral): responsible for "how the vehicle turns."
It spans electric power steering (EPS), rear-wheel steering, four-wheel steering, and—now with a clear regulatory foundation—steer-by-wire. The release of GB 17675-2025 Motor Vehicle Steering Systems — Basic Requirements in December 2024 removed the mandatory requirement for a mechanical linkage, clearing institutional barriers to full by-wire implementation of the lateral axis. The standard will take effect on July 1, 2026.
Z-axis (Vertical): responsible for "vehicle posture and ride comfort."
This axis evolves from passive suspension to electronically controlled dampers, air suspension, and ultimately fully active suspension. Across the industry, intelligent/active suspension is widely regarded as the third axis, on par with brake-by-wire and steer-by-wire.
XYZ axes product diagram; photo source: BIBO (Shanghai) Automotive Electronics
A simple analogy helps clarify the picture: the X-axis is like the legs, driving forward motion and braking; the Y-axis is like the waist and shoulders, directing changes in direction; and the Z-axis resembles the knees and ankles, absorbing shocks and maintaining balance.
Historically, these three dimensions were handled by different systems, different ECUs, and often different suppliers—each optimized independently, with compromises made through calibration. Today, with the growing adoption of chassis domain controllers (CDC), they are increasingly treated as a single, integrated control problem: how to make all three axes work together coherently in every scenario, rather than operating in isolation.
This shift toward coordinated control is the core value—and the defining logic—of chassis domain integration.
2. Why integration of the three axes is essential?
From an engineering perspective, three-axis integration is not a "trendy" new idea—it is, in many ways, a long-overdue piece of common sense.
(1) By-wire technologies make the chassis "programmable"
Without by-wire systems, true integration is simply not possible.
In the mechanical and hydraulic era, the interaction between braking, steering, and suspension relied largely on the system's natural mechanical coupling, supplemented by electronic "patches" such as ESP and ABS. Coordination was indirect, reactive, and constrained by hardware linkages.
Once the longitudinal axis adopts brake-by-wire, the lateral axis adopts steer-by-wire, and the vertical axis gains active suspension control, the situation fundamentally changes. The core chassis actuators gradually form a network of motors, valves, and sensors, all of which can be orchestrated by a chassis domain controller. Every action—braking force, steering angle, suspension response—can be scheduled and coordinated at the millisecond level.
At this point, allowing the three axes to operate independently is no longer conservative—it is inefficient.
Take an emergency cornering scenario as an example: if the suspension does not proactively stiffen the outer dampers, and the rear wheels do not apply a small counter-steering angle, even the most responsive steer-by-wire system cannot fully realize its performance potential. The limit is no longer set by a single subsystem, but by how well the three axes work together.
(2) High-level intelligent driving requires "whole-vehicle actions," not isolated enhancements
Consider a typical scenario: a vehicle running urban NOA suddenly encounters a pedestrian darting out from behind an obstruction. How should the vehicle respond?
The traditional approach is straightforward but crude: apply maximum braking first, then steer if necessary. Braking and steering operate largely in isolation, each doing its own job. The result, however, can be suboptimal—either the vehicle fails to stop in time, or excessive steering input leads to instability or loss of control.
The logic of integrated control is fundamentally different. Within milliseconds, the system must decide whether it is better to "brake a little and steer a little"—maintaining a smooth trajectory, or "brake harder without steering"—to avoid lateral instability. At the same time, the suspension proactively stiffens the outer dampers to reduce body roll and preserve tire grip.
This is what "whole-vehicle action" means: at the critical moment, braking, steering, and suspension work in concert. The vehicle's motion—across the longitudinal, lateral, and vertical directions, as well as roll, pitch, and yaw (its six degrees of freedom)—is kept within a controllable envelope.
Academic research on Integrated Chassis Control has repeatedly demonstrated that the coordinated control of driving, braking, steering, and suspension can significantly improve both trajectory-tracking accuracy and vehicle stability, particularly under extreme conditions.
This level of integration could be postponed in the L2 era. But once urban NOA, L3, and higher levels of automation move to the forefront, simply "adding more braking" or "refining steering alone" is no longer sufficient. Three-axis coordination becomes a necessity, not an option.
(3) With the consolidation of the E/E architecture, the vehicle finally has a "unified brain."
In the era of distributed architectures, dozens of ECUs were scattered across the vehicle, each focused on its own narrow task:
The braking ECU cared only about braking force;
The steering ECU focused solely on steering angle;
The suspension ECU managed damping stiffness;
The ESP ECU intervened only to prevent skidding.
Information was exchanged via the CAN bus, but with high latency (10–100 ms) and limited bandwidth (around 1 Mbps). This architecture was fundamentally incapable of supporting high-frequency, tightly coupled control. It was like a group of people all speaking at once—each doing their own calculations, with no unified command.
That situation is now changing. As centralized E/E architectures, chassis domain controllers, and central computing platforms are gradually deployed, the chassis is, for the first time, gaining a true unified "brain."
Take two representative examples:
Bosch's Vehicle Motion Management (VMM) system is explicitly designed to coordinate braking, driving, steering, and suspension, treating the vehicle as a single entity across all six degrees of freedom. By decoupling software from hardware, the same control software can be adapted to different actuator configurations.
ZF's cubiX platform positions itself as a hardware-agnostic vehicle motion control layer, allowing OEMs to reuse a single control logic across different actuator solutions. Whether the vehicle is equipped with Bosch's iBooster or Continental's MKC1, cubiX can orchestrate them under a unified control strategy.
The real breakthroughs lie in three areas:
Communication upgrades
: moving from CAN to in-vehicle Ethernet, with bandwidths of 100 Mbps to 1 Gbps and latencies below 10 ms;
Centralized computing power:
chassis domain controllers now delivering 10–100 TOPS, sufficient to run complex, multi-axis fusion control algorithms;
Data sharing
: real-time access to all relevant sensor data—IMU, wheel speeds, steering angles, suspension travel—so decisions are no longer made in isolated silos.
Without a brain, meaningful integration is nearly impossible.
With a brain in place, not integrating the three axes starts to look irrational.
(4) Standards and regulation: Turning "daring to do" into "rules to follow"
Before the release of GB 17675-2025, steer-by-wire systems around the world largely existed in a state of fragmentation, with OEMs and suppliers effectively each pursuing their own path:
Infiniti Q50 (2013)
: the world's first mass-produced steer-by-wire vehicle. Due to reliability controversies and the absence of a clear regulatory framework, subsequent models reverted to conventional EPS systems.
Tesla Cybertruck (2023):
adopts steer-by-wire, but is sold only in North America; regulatory and vehicle design constraints have so far prevented its introduction into other markets.
NIO ET9 (2024):
equipped with steer-by-wire, yet prior to the new standard could only obtain approval through case-by-case regulatory assessments.
The new national standard GB 17675-2025 fundamentally changes this situation by addressing two critical issues.
First, at the legal and regulatory level:
The standard explicitly recognizes steer-by-wire and full-power steering systems, allowing the removal of mechanical linkages as long as safety requirements are met.
This means the steering wheel no longer needs to be physically connected to the road wheels via a steering column. It opens the door to new possibilities such as retractable steering wheels, unconventional steering interfaces, and even the long-term prospect of vehicles without a traditional steering wheel.
Second, at the technical level
：
The standard replaces vague acceptance with clear and enforceable safety thresholds, moving away from a "design-it-any-way-you-like" approach.
Key requirements include:
Energy storage and redundant power supply
: backup power sources are mandatory to ensure steering capability is maintained in the event of primary system failure.
Degradation strategies
: explicit performance requirements under degraded states, including timelines for deceleration onset and specified deceleration levels.
Warning signals
: system failures must be promptly communicated to the driver through clear alerts.
Functional safety
: electronic steering control systems must comply with international standards such as ISO 26262.
Practical impact: Taking the NIO ET9 as an example, its steer-by-wire system adopts a fully redundant architecture, achieving a loss-of-steering probability of just 4.5 FIT—that is, only 4.5 failures per billion operating hours. This represents a 2.2× improvement in reliability compared with conventional electric power steering (EPS) systems.
In essence, regulation has shifted from a phase of "no standards, only case-by-case approvals" to one of "clear thresholds and hard safety boundaries." The signal to the industry is unambiguous: by-wire architectures and three-axis integration are no longer fringe experiments—they are now validated technical pathways toward mainstream adoption.
3. What does three-axis integration feel like in real driving?
After laying out the technical logic, it is worth returning to the most intuitive question: when the three axes truly begin to work in concert, how does a vehicle actually feel different?
Using the NIO ET9 as a representative example—alongside practices emerging across mainstream intelligent EVs—we can break this down into three tangible changes.
(1) "Smarter steering": Steer-by-Wire combined with rear-wheel steering
With the combination of steer-by-wire and rear-wheel steering, the ET9 achieves an exceptionally flexible steering ratio at low speeds. In tight U-turns, underground garages, and parking maneuvers, drivers no longer need frequent hand-over-hand steering. Small steering-wheel inputs translate into large wheel angles, making low-speed maneuvering noticeably easier and more intuitive.
At higher speeds, the system automatically increases the steering ratio. The steering wheel feels more deliberate and stable, reducing over-sensitivity to small inputs and improving straight-line stability during cruising.
This balance—agile at low speed, composed at high speed—is no longer achieved through mechanical compromise. Instead, it is realized entirely through software-defined control of the Y-axis, dynamically adapting steering behavior to driving conditions.
(2) "Smoother ride": Active suspension and body motion control
With active suspension and integrated body motion control, the Z-axis is no longer limited to passively absorbing impacts. It gains the ability to anticipate and counteract disturbances.
When driving over speed bumps or rough surfaces, pitch and vertical body motions are significantly reduced. During high-speed lane changes or emergency avoidance maneuvers, active roll suppression helps prevent occupants from being thrown side to side, improving both comfort and perceived safety.
Many automakers describe this capability using marketing terms such as "Magic Carpet" (Mercedes-Benz), "Cloud Ride" (Li Auto), or "Intelligent Chassis" (XPeng). Despite the different names, they all point to the same underlying shift: the Z-axis is no longer purely a matter of mechanical tuning—it has become a software-controlled, programmable dimension of vehicle dynamics.
(3) "More sophisticated braking": Not just stopping, but how to stop
In traditional AEB logic, safety often comes at the cost of refinement. Once a hazard is detected, the system applies maximum braking as quickly as possible. The result is a harsh deceleration, pronounced nose dive, and in extreme cases, loss of stability due to tire lock-up.
With the foundation of three-axis integration, the industry is exploring more advanced strategies:
X-axis (braking): braking force is applied progressively rather than instantaneously.
Y-axis (steering): within safe distance constraints, steering angles are adjusted to help avoid obstacles.
Z-axis (suspension): active support is provided to reduce pitch during braking and maintain tire contact and grip.
Partial implementations of such integration already exist in the market. For example: BYD and Bosch's jointly developed dTCS (distributed Traction Control System) enables coordinated control between the braking system and the powertrain on the Han EV. Voyah's "Tianyuan Intelligent Chassis" combines steer-by-wire and brake-by-wire to achieve millisecond-level X–Y axis coordination.
Full three-axis integrated AEB, however, is still under development, as it requires deep integration across sensor fusion, decision-making algorithms, and coordinated actuator control. The core insight here is that the breakthrough does not come from a "stronger braking system," but from X, Y, and Z axes working together in service of safety, rather than any single system bearing the entire burden.
As chassis domain controller computing power continues to rise (10–100 TOPS) and in-vehicle Ethernet becomes mainstream (latency below 10 ms), fully integrated three-axis AEB is steadily moving from theoretical possibility toward real-world deployment.
4. Three-axis integration is reshaping value distribution across the industry value chain.
If the past decade of China's automotive industry was defined by competition in battery technology, smart cockpits, ADAS, and autonomous-driving chips, then the next decade's battleground is clearly shifting toward the intelligent chassis. From an industry perspective, three-axis integration is not about adding a few new features—it opens up a new foundational battlefield. One that reshapes automakers' technological identity, redraws value distribution across the supply chain, and even influences China's voice in the global automotive standards system.
(1) For automakers: The chassis moves from "supporting role" to technical signature
In the past, when OEMs talked about flagship models, the focus was usually on the three electrics, computing power, or lidar configurations.
Going forward, the deepest points of differentiation in high-end intelligent EVs are increasingly likely to lie in questions such as:
Does the vehicle support full by-wire capability across all three axes?
Is there a unified Vehicle Motion Control (VMC) platform coordinating the chassis as a whole?
Can the system pass the most stringent global safety and certification regimes?
NIO ET9's exploration—spanning dual China–Europe certification, full steer-by-wire, and fully active suspension—essentially puts the chassis back at the center of the flagship narrative. The chassis is no longer a background component; it becomes a visible expression of core engineering capability.
(2) For the supply chain: from component suppliers to platform-level players.
Three-axis integration is transforming the chassis from a collection of multiple components and subsystems into a unified hardware–software platform.
Behind brake-by-wire, steer-by-wire, and intelligent suspension lies a platform-level reconfiguration of capabilities spanning actuators, electric motors, sensors, and power semiconductors. At the same time, the emergence of Vehicle Motion Control (VMC) software is pushing Tier 1 suppliers beyond the role of mere component vendors, positioning them instead as providers of a "chassis operating system."
In this wave of restructuring, leading European suppliers have already moved early to secure positions around VMC and X-by-Wire architectures. Meanwhile, Chinese Tier 1 players are accelerating their transition from components to platforms.
For example, Bethel has used brake-by-wire as an entry point to expand steadily toward system-level capabilities; Tongyu Automotive, GLB, BWI, JiongYi Electronic, MouXing Technology, LEEKR Technology, Orient Motion, NASN, and Watson Rally have been rapidly building mass-production experience in electronic braking and integrated control, emphasizing tight coordination between actuators, control algorithms, and vehicle-level strategies; and Tuopu, Baolong, and KH Automotive Technologies have entered Z-axis control through intelligent suspension, gradually evolving suspension from a comfort-oriented component into an active actuator that participates in overall vehicle motion control.
Ultimately, those that can establish a solid position across the combined domains of hardware, software, and functional safety within three-axis integration will be the ones best positioned to reshape their role in the chassis industry over the coming decade.
(3) For China's automotive industry: From "technology follower" to co-author of the rules
The significance of GB 17675-2025 goes beyond granting steer-by-wire a formal "license to operate," and beyond clearing the path for any single model. It serves as a broader signal.
In highly engineered domains such as intelligent chassis systems—where functional safety and regulation are paramount—China is beginning to build its own standards framework and regulatory voice. Companies are no longer simply translating and adapting foreign specifications; through mass-production experience, test data, and validation methodologies, they are actively participating in rule-making itself.
For China's intelligent EV industry, this marks an essential transition—from being able to build advanced technology, to being able to help write the standards that govern it.
5. The next stage of competition is about who can truly "walk"
Over the past decade, China's automotive story has been defined by two keywords: electrification made cars "able to run," and smart cockpits plus intelligent driving made them "able to think." In the decade ahead, a more fundamental question is becoming increasingly decisive: can the vehicle truly "walk"? Across diverse road conditions and real-world scenarios, are its every launch, lane change, brake event, and bump crossing smart enough, stable enough, and refined enough?
Three-axis chassis integration is one of the most important technical answers to that question.
As
brake-by-wire, steer-by-wire
, and
intelligent suspension
move toward mainstream adoption—and as Vehicle Motion Control (VMC) becomes the "brain" of the intelligent chassis, forming a third software pillar alongside the cockpit OS and the autonomous-driving OS—while national standards such as GB17675-2025 continue to mature, the real era of the intelligent chassis is only just beginning.
Seen from this perspective, the seemingly "engineering-heavy" news at the beginning of this article is far more than a simple change in standard numbering—from 2021 to 2025. It is a statement of direction:
in the next foundational transformation of intelligent electric vehicles, China is no longer merely following—it is increasingly qualified to help write the new rules.
Written by Xiaoying Zhou — CEO and Editor-in-Chief, Gasgoo International
