Brakes haven’t evolved much since four-wheel electronic antilock became mainstream, but I think I just experienced the next leap in braking tech: Brembo Sensify.
With today’s ABS, when you step on the pedal, pressure is distributed evenly to all four wheels, either directly or by wire via an external pressure source and often with a front/rear proportioning valve. Then, if traction is lost at one or more of the tires, a valve on a central hydraulic controller relieves some pressure to the slipping wheel(s) to regain traction. But today’s best hydraulic valves can only open and close in roughly 20-millisecond increments, relieving about 5 bar (73 psi) of brake pressure each time. Drivers feel pulsations, as does the chassis. Both are happier without them, and Sensify eliminates them.
Brembo Sensify is braking for the centrally controlled software-defined vehicle. It consists of control units that direct braking independently at each corner in response to the driver’s input on the brake-pedal force sensor. It operates “by wire,” but Brembo avoids the terminology to distinguish Sensify from today’s by-wire systems, which still generate pressure centrally then bleed it to control slip.
Brembo reckons Sensify can apply to nearly any vehicle, from city cars and trucks to motorcycles, race cars, and the hypercars already using Brembo brakes. The most elemental systems will employ an electromechanical brake (EMB) at each corner. These use a sliding caliper with a high-precision reversible screw-jack motor rather than hydraulic pistons to squeeze the brake pads. (The parking brake function involves a park pawl engaging to prevent release.) Six EMBs could power a big monobloc caliper, but this would be huge and heavy, so higher-performance applications get a “wet corner,” with a traditional hydraulic caliper and a screw jack pressurizing a master cylinder mounted just inches away.
Precise control of each wheel’s instantaneous brake pressure allows the brakes to help with yaw control in ways that simply bleeding pressure can’t. After decelerating from highway speeds, subsequent gentle stops might use the rear brakes only, allowing the fronts to cool. Rotors can be individually “dried” as needed in wet conditions. Sensify can coach drivers to improve their braking to deliver better mpg, EV range, or lap times. Brake response can be tailored to drive modes, informed by pedal pressure, travel, application rate, or a mix of all three. Installing Sensify on a trailer’s brakes with the tow vehicle controlling them promises unprecedented towing safety and stability. And Brembo or other OEM brands could offer over-the-air upgrades like Track mode programming for a weekend, or forever.
The ability to reverse the electric motors allows spring clips to retract the pads off the rotor, eliminating drag and improving cooling, which boosts efficiency and reduces brake-dust particulate emissions. Never applying more pressure to any brake than precisely what’s needed for the given circumstances further reduces wear, heat, and dust.
At the moment, Brembo doesn’t claim these brakes allow for shorter stopping distances, and back-to-back wet and dry stops in Tesla Model 3 Performance sedans with and without Sensify showed no difference, though further development and integration with smart tires and the like could improve straight-line stops. But steering during a panic stop proved far more accurate, with the brakes helping yaw the car. And finally, Sensify brakes can tell the driver when pads need replacement and potentially refuse a restart once they’re depleted completely.
Cost, Weight, and Availability
Sensify should weigh about the same as a conventional system of equivalent performance, with the mass of today’s brake lines and fluid largely offsetting Sensify’s added equipment. And although there’s additional parts cost, Brembo suggests life-cycle value is also roughly equal, considering simplified development, integration, and assembly of this dry-chassis system and the lower maintenance costs that come with dramatically improved pad life and little or no fluid to replace or bleed.
Some jurisdictions still require a fail-safe fluid link to the front brakes, and Brembo will provide this on its first application scheduled for production in 2024. Note that by equipping its EMB actuators with two sets of electric windings and redundant controls, Sensify qualifies for up to Level 5 autonomy.
My test drive suggests Sensify is to stopping what four-motor electric powertrains are to going. I want both, and so do you.
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