▲ SbW and BbW systems (Image source: Korea Automobile Research Institute)

Electric vehicles and autonomous driving are leading the system change
It is essential to address issues such as functional safety.

It was reported that the by-wire system (electrical system) that replaces mechanical connections in the steering and braking fields of automobiles has reached the commercialization stage, and that the big trend of electric vehicles and autonomous driving and the realistic goal of a skateboard platform have led to changes.

On the 26th, the Korea Automobile Research Institute released an industry trend report titled “by-Wire Towards Completion,” and said that although the by-Wire steering and braking system still has room for improvement in terms of functional safety and other aspects for commercialization, it is expected to become widespread within a few years thanks to the will of automakers pursuing customized manufacturing methods.

In the past, mechanical connections and hydraulics were used in parts of cars that required a lot of force, but with the development of semiconductor, control, and communication technologies, this has gradually changed to using electricity.

The end point of this change is the so-called 'by-wire' system, which replaces mechanical connections with electrical components. It has already become widespread in many areas of automobiles due to its tendency to be advantageous for sophisticated control and weight reduction and miniaturization.

This system basically consists of a controller (ECU), sensors, motors/actuators, etc., and each componentIt is named by-'Wire' because it is connected by wires.

Between the accelerator pedal and the engine throttle (Throttle-by-Wire), and between the shift lever and the transmission (Shift-by-Wire).
A typical example is the electronic damper (Suspension-by-Wire) of the suspension, which is also included in this category.

In the last two hurdles, steering and braking, commercialization of by-wire systems is also imminent.

In the areas of steering and braking, by-wire has only been partially attempted so far, mainly due to safety concerns.

Although power steering has changed from hydraulic (HPS) to electric (EPS), Steer-by-Wire (SbW), which eliminates the mechanical connection between the steering wheel and rack, has not yet become widespread.

There is also a system that mimics the pressure applied to the brake pedal and controls the amount of braking with an electric signal.
Although it exists, Brake-by-Wire (BbW), which completely excludes hydraulic pressure from actual braking, has not been commercialized.

The Korea Automobile Research Institute reported that recent attempts at commercialization of SbW and BbW in the industry are evident, and that SbW is imminently being applied to mass production models.

In terms of parts, global parts companies such as Mando, Hyundai Mobis, Bosch, Brembo, Continental, Hella, Hitachi Astemo, Nexteer, and ZF are promoting mass production development of BbW or SbW.

Media outlets such as Electrek have reported that Toyota and Lexus have already confirmed the installation of SbW without mechanical connection in their electric vehicles, the BZ4X and Lexus RZ, respectively, and that Tesla will also install SbW soon.

With SbW The commercialization of BbW is closely related to technological advancements in the electric and autonomous driving sectors.

SbW can help improve the interior comfort of electric vehicles and minimize their turning radius, while BbW can improve energy efficiency by eliminating extraneous hydraulic devices from the overall vehicle design.

SbW is expected to be unavoidable as the introduction of all-wheel steering (AWS) is necessary to offset the increase in turning radius caused by the extension of the wheelbase to secure space for mounting the drive battery and improve interior livability.

Most of the latest finished vehicles already equipped with AWS have adopted SbW, which has no mechanical connection, for rear-wheel steering.

BbW can more smoothly implement a hybrid braking system of regenerative braking and friction braking when applied to electric vehicles, and improve energy efficiency by eliminating the hydraulic device, while making brake fluid unnecessary.

The Korea Automobile Research Institute believes that both BbW and SbW enable more precise control in terms of autonomous driving and are also advantageous in terms of coordination with active safety technology.

BbW can perform more precise and faster braking and control in conjunction with active safety functions such as ADAS in autonomous driving situations, and can shorten the physical braking distance to increase response capabilities in emergencies.

SbW can increase steering accuracy by flexibly changing the steering angle according to the situation, and can block unintended steering intervention by the driver or unnecessary vibrations generated from the road surface.

The realistic goal of an electric skateboard platform with increased design freedom also drove the change.

The skateboard platform modularizes the driving-related subsystems and integrates them into the underbody (or chassis), allowing automakers to dramatically increase the design freedom of their vehicles. />
Conceptually, the drive-related subsystems impose fewer constraints on the rest of the vehicle design, which means greater freedom in arranging boarding and loading spaces on the skateboard platform.

To maximize the usability of the platform, the structure should be simplified by freely arranging driving-related parts and eliminating hydraulic devices, etc., so a by-wire system can be helpful.

Although the two systems still have room for improvement in terms of functional safety and consumer acceptance, they are expected to become widespread within a few years thanks to the will of automakers to pursue customized manufacturing methods in response to mobility services.

Only when a satisfactory agreement is reached between automakers, parts manufacturers, and regulatory authorities in terms of functional safety and consumer acceptance can SbW and BbW be fully implemented.

At this point, SbW and BbW need to further improve electrical and electronic system redundancy (E/E redundancy) to prepare for failures, and practical standardization that takes into account various driver reactions in real driving situations is needed.

However, since the will of automakers to meet the demand for vehicles derived from various mobility services is clear, it seems that technical and institutional issues will ultimately be resolved.

Like the PBV (Purpose Built Vehicle) advocated by Hyundai Motor Group, major automakers are planning ‘multi-variety customized manufacturing’ to flexibly respond to diverse vehicle demands.

In this manufacturing method, cost reduction through commonization of parts and securing high design freedom are important, and in the process, the completion of by-Wire through the introduction of SbW and BbW is a natural process.r />
Considering the roadmaps of major automakers and parts companies, the Korea Automobile Research Institute predicted that SbW and BbW will begin to be applied in mass-produced vehicles around 2025.