Two big emerging technologies coming to automotive chassis are steer-by-wire (SBW) and brake-by-wire (BBW). Yes, I realize that those acronyms mean something else if you’re on a website labeled “adult.” So don’t Google them. Unless you’re over 18 and are into that sort of thing. Then it’s none of my business.
Anyway, by-wire systems are nothing new, but they’ve only recently become a probability in future automotive. The systems being used for these by-wire designs are made by suppliers like Bosch, JTEKT, Nexteer, and ZF.
Steer-By-Wire
Back in 2013, not long after I first started writing about automotive, Infiniti announced a steer-by-wire system for the Q50 sports car. It was kinda cool, but people either didn’t know why it was a thing or were unimpressed by its lack of “road feel” for the driver. I was personally fascinated by the technology and, especially, the redundancies used to make it safe.
Newer SBW systems include a host of redundancies in both sensors and actuators to maintain vehicle control if anything fails. This is similar to how SBW systems in aircraft—which have been around for a long time—work. The problem so far is that compared to a physical drive shaft connection, which has been the norm for automotive since the first car, SBW is expensive to implement. Mostly thanks to those redundancies.
This is changing, though. The Q50 didn’t last long with its SBW, but newer production vehicles like the Tesla Cybertruck, Lexus RZ 450e, and the upcoming Mercedes-Benz EQS are embracing this tech once again. The kinks in the wires, so to speak, are being worked out.
The advantages to SBW are plenty. It removes the need for a physical steering column, which adds safety and frees up interior designers from the constraints that placed. It allows for easy implementation of variable steering ratios, allowing for better maneuverability at low speeds and easier lane maintenance at higher speeds. It also makes autonomous driving easier to implement and it could show improved implications for safety overall through redundancies not found in column-only designs.
Brake-By-Wire
Most vehicles today are using mechanical brakes based on hydraulic connections between the brake pedal and the calipers clenching brake pads to rotors. This has been the norm for several decades and was also the norm when drum brakes were more common. BBW systems replace those hydraulic connections with electronics.
The basic idea is that electrical signals and sensors are used to activate actuators on the rotors to apply brakes. This replaces the hydraulics normally used.
Many vehicles today use an Electro-Hydraulic Brake (EHB) system that replaces a mechanical pump with an electric one to produce braking pressure. This is especially common in electrified vehicles.
Fully by-wire braking systems are Electro-Mechanical Brake (EMB) systems, also known as “Dry BbW.” These are fully electronic with the braking being done by electric motors (actuators) instead of brake pumps and fluid. These fully by-wire systems allow for seamless brake regeneration control, stability controls, and anti-lock braking system (ABS) integration.
Safety in a full BBW system is a priority and a reason this technology hasn’t been widely implemented. These systems sometimes employ a backup hydraulic system, but usually use multiple actuators for redundancy instead. Which is why they are generally more costly to implement. Nevertheless, many vehicles, especially in the battery-electric market, use various BBW technologies. Porsche, Toyota, General Motors, and others have implemented various forms of BBW into their vehicles. Full by-wire (EMB) systems are most common in electric vehicles, but are beginning to emerge in combustion models as well.
When Will By-Wire Be the Norm?
The initial rollout will be slow, in terms of models and sales, focusing largely on luxury and upper-end models. It’s likely that within the next decade, market penetration into mainstream models will be high enough to be a notable percentage of the whole. My personal prediction is that by 2040, steer-by-wire will be the norm and brake-by-wire will be close to having that same status.
This article originally published on the AaronOnAutos Substack.
