Artificial Anchors

Computer-controlled brakes? Introducing brake-by-wire

by JEZ SPINKS

Geek speak The complicated explained

Computer-controlled brakes? Introducing brake-by-wire

HERE’S no stopping the advance of vehicle technology. Except, ironically, for braking systems, which have remained based predominantly around hydraulics since the birth of the motor car.

By-wire systems have long been prominent in the aerospace industry, and throttle-by-wire and shift-by-wire are now common in the automotive world. Nissan/ Infiniti even gave us steering-bywire more recently.

Yet pushing electrical pulses rather than hydraulic fluid with a brake pedal is an approach that’s struggled to achieve wide adoption beyond Toyota/Lexus hybrids, despite brake-by-wire development beginning in earnest in the ’90s.

Mercedes-Benz tried to move the game on in 2001, when it introduced the first brake-bywire system on a road car with the R320 SL. But the German car maker ended up deleting Sensotronic from other models such as the E-Class in 2006 – reverting to traditional brakes T – after countless customer complaints and a recall of nearly two million vehicles.

More than a decade on, though, and electro-hydraulic braking is back in a mass-production car with Alfa Romeo’s Integrated Braking System (IBS).

As with Sensotronic, but with reduced cost and complexity, IBS severs the mechanical link between the brake pedal and master cylinder – instead using a compact, lightweight digital module to interpret how hard and quick the driver has pressed the pedal for every application.

Multiple advantages are spruiked. Firstly, in an industry obsessed with light-weight, the system saves a useful three to four kilos by dispensing with traditional braking components such as a vacuum brake servo.

It also builds brake fluid pressure notably faster, and combined with the ESC that can react in less than 10 milliseconds, IBS is claimed to shorten brake distances significantly.

Alfa claims benchmark 100km/h-to-screeched-standstill figures for the Giulia: 32 metres for the flagship Quadrifoglio and 38.5 metres for rest of the range.

How long the Alfa remains distinctive among conventionally powered cars remains to be seen.

Technology giant Bosch, which worked with Daimler on Sensotronic, is having another crack with its iBooster braking system, though it’s primarily designed for hybrids and EVs.

It also retains a direct link between the pedal and master cylinder, and essentially would act as a replacement for vacuumbased boosters.

So, no one’s brave enough yet to bleed hydraulics out of the equation. Watch this space. M

No one’s brave enough yet to totally bleed hydraulics out of the equation

Mixed (brake) response

We've tried it and we didn't like it much

FOR AN upcoming comparison we found ourselves in the Alfa Romeo Giulia QV at Winton Motor Raceway – and barrelling down into turn one where, hitting the brakes, the initial response was that there was no response. Or exactly what you don't want to feel when you're doing 200km/h and, in the space of 150 metres, need to be doing 90km/h.

Yet that was exactly Warren Luff's experience the first time he went to hit the Giulia QV’s brakes. The pedal didn’t go dead, but Luffy thought he was about to have a massive accident… before the system did its thing. Brake feel in normal driving wasn’t great, as you need to press fairly hard on the pedal to bring the car to a halt, though without having tested the QV with its standard brakes it’s difficult to gauge whether the brake-by-wire system or the optional carbon-ceramics were the main culprit in this respect. Beyond that slightly disconcerting first sensation under culprit hard braking, we were impressed with IBS. It’s possible that it's great at handling sudden 100 per cent inputs.

But from that point onward the Alfa feels to stop better than any car we’ve ever driven. It’s incredible the rate at which it seems to shed speed.

How it works

Alfa’s Integrated Braking System explained

1 ALL IN ONE

IBS dispenses with the separate master cylinder, vacuum brake booster and stability control hardware, integrating ESC, ABS, brake booster and brake actuation into a single device. Physically, this Franken-unit marries a patchwork of components including both electrical and hydraulic assemblies, brushless DC motor driving a ball screw to create the required hydraulic pressure, and brake fluid reservoir.

2 NATURAL FEEL

The brake pedal is still linked to a traditional tandem pump, though this piston doesn’t directly push brake fluid into the lines as with a conventional system. Instead the computer’s sensors read the driver’s input. A load simulator cylinder is designed to provide the driver with natural pedal feedback, while a linear actuator aims to make pedal feel consistent and predictable. The tandem pump’s connection to the pedal allows it to serve as a sufficient back-up in the case of a system failure (with a similar feel to a traditional system with no vacuum assistance).

3 LACK OF PULSE

Because the system separates the pressure of the brake pedal from the slowing wheels, IBS removes the pulsing effect commonly associated with antilock braking.

4 PIPE MASTERS

Hydraulic brake fluid is still distributed to each wheel’s calipers via brake lines – but capable of performing the process significantly faster. IBS developer Continental – which calls the system MK C1 – says full brake pressure for a twotonne vehicle can be applied after just 150 milliseconds.

5 FIND THE RIGHT MODE

Variable pedal feel and actuation can be tailored via software, and can be programmed differently not just between manufacturers, but also different vehicle modes. Selecting Dynamic on the Alfa Giulia Quadrifoglio’s DNA Pro vehicle setting system, for example, introduces a sharper, more direct braking response than in Normal.