This is the smart brake system that Brembo has been working on for more than 20 years.

Hey everyone, I'm here to write another brake science post.

From Tesla, the market leader, to domestic new forces such as NIO and Xpeng; overseas brands such as Polestar 2 and Mustang Mach-E to domestic brands such as BYD Tang, these cars have one thing in common: Brembo brake calipers.

I also found that these brake calipers have made many improvements in details to meet the requirements of low carbon and low emissions. Interested students can read the extended reading at the end: "After driving the Mach-E, I wrote a popular science article about brakes."

Okay, now let’s get to the point.

Just last Saturday, December 18, 2021, precisely because of the above article, I had the honor of receiving a test drive invitation from Brembo and went to their base in Nanjing to experience the SENSIFY intelligent braking system.

Since the following content may be quite intense, I will first talk about the results:

Too, too strong... This makes me full of expectations and confidence for the arrival of wire-controlled brakes in the future. I suggest Brembo consider splitting SENSIFY and listing it on the market (let me vote too)!

Next, I will give you a brief introduction on what Brembo's SENSIFY is and whether it is more hype than reality.

Basic knowledge of brake assist system

Before introducing Brembo's SENSIFY, we have to talk about the power-assisting methods of the braking systems currently on the market.

Vacuum Assist

The picture is a bit bad, please bear with it (Source: Auto Brake Network)

The picture above shows the most basic power assistance method currently available.

That's right, although the brakes can be used without power assistance, in that case, if you don't have enough strength, you may not be able to lock the brakes. This is only limited to the field of racing and some low-speed applications.

When you step on the brake pedal, this action will be linked through the lever structure and use the vacuum booster (a vacuum source is required, such as an internal combustion engine) to push the brake oil in the master brake cylinder. This oil will enter the ESP pump and be distributed to the four brake calipers (slave cylinders) through the electronically controlled valve, thereby applying braking force to the brake disc to generate friction and stop the vehicle.

So the question is, now that more and more electric cars are appearing, it means that more and more cars do not have engines, which means that more and more cars cannot generate vacuum, which means that vacuum power assistance cannot be used.

Electronic power

In fact, just like the change of power steering from vacuum hydraulic to electronic power steering, the power steering of brakes has also been following the same development trend in recent years.

Vacuum boost (slightly older fuel vehicles and supercars use this more often)

Electronic power assist (the brakes don’t fail, they just lose power, so you have to think carefully)

Because it does not require a vacuum source, but can be driven by electricity, and the degree of assistance can be changed at will through software, so the advantages of electronic assistance are quite numerous:

1. Adapt to more car models;

2. It can build pressure faster;

3. Can change the feel of the foot;

4. Can be combined with kinetic energy recovery more seamlessly.

One-Box vs Two-Box

Two-box solution

Ordinary electronic power-assisted brakes simply replace the vacuum power-assisted brakes with electronic power-assisted brakes. Because the ESP pump is still in a separate state, with a total of two modules, it is commonly known as the Two-box solution.

One-box Solution

The most advanced brake assist solution currently available on mass-produced vehicles is the One-box solution that integrates ESP.

However, current laws and regulations in our country do not allow you to take your eyes off the road.

It is worth noting that in the current One-box solution, there is no mechanical connection between the pedal and the hydraulic system. In the process of generating braking force and input from the foot, wire control has actually been achieved. In other words, no matter how hard your foot exerts, it only provides a position information, and the pressure in the brake system is entirely established by the motor.

ESP pump, so useless.

Hello everyone, I am a weak chicken...

However, this brings up another problem: in order to meet the dual redundancy requirements of autonomous driving, there will still be an external ESP module to provide backup brake oil circuit pressure.

Moreover, ESP is still in the traditional electro-hydraulic category, and the braking time required is several times that of the current electronic power-assisted braking system. If you often drive fast without turning off ESP, every time ESP intervenes, the plunger pump will heat up and wear out severely, reducing the life of ESP.

The originally streamlined system has been given a redundancy, and it is not a very reliable one. It seems to be putting the cart before the horse, but this is also the regulatory requirement at this stage. Of course, this also indirectly shows that the pure mechanical system is still higher than the electromechanical hybrid system in the industry's cognition. It is really hard to say when the mechanical backup can be removed.

How is SENSIFY different?

Very different.

structure

It looks complicated, but it’s actually very simple

The Brembo brand name comes from the surnames of its two founders: Breda and Bombassei. Similarly, SENSIFY is a combination of Sense and Simplify. In addition to traditional brake calipers, brake discs, and oil circuits, this system is mainly composed of the following:

1. Pedal simulator;

2. Brake control unit;

3. Hydraulic actuator;

4. Mechatronic caliper.

Pedal Simulator

The reason why SENSIFY's pedal is called a "pedal simulator" is because its brake pedal is just a position sensor, just like the one-box system on the market.

Entry-level racing simulator: Logitech G920

In fact, it is nothing more than a racing simulation game pedal with better foot feel, higher cost, more materials and greater reliability.

Brake control unit (I wonder if Brembo is afraid of chip shortage, hahaha.)

The electrical signal generated by this pedal will be transmitted to the brake control unit (which can be understood as the brake domain controller) for processing, and then issue a command to brake the corresponding wheel.

It can be understood as a precise and fast electric pump

If your vehicle is equipped with traditional hydraulic brake calipers, this signal will be transmitted to the hydraulic actuator, which pushes the brake to apply the brake.

Floating calipers can achieve full "dry"

If your SENSIFY system is also equipped with a mechatronic caliper, the brake control unit will directly command the motor on the caliper to clamp the caliper, without the need for brake fluid.

I'm good at noticing details.

If you think this system is the same as the one-box solution mentioned above, and that it will be over if the electronic system fails, then you are totally wrong. Because, from the oil pot on the pedal simulator in the picture above, you can see that SENSIFY retains the oil circuit connection from the pedal to the downstream brake system. We learned from the on-site Brembo factory engineer that this part of the oil circuit will only be opened when the main system fails.

flexibility

Judging from the number of parts, SENSIFY does not seem to live up to the "Simplify" in the second half of its name. However, it has indeed increased the freedom of car manufacturing and made the intelligent braking simpler.

Easy to match

I'm not greasy because I use electricity

SENSIFY has flexible customization options for different models. If you need greater braking force or more advanced caliper configuration, you can still choose a traditional high-performance multi-piston fixed caliper and push it through a hydraulic actuator. However, if the braking force requirements are not high for small vehicles, low-end models, or the rear wheels of electric vehicles, the mechatronic caliper in the picture above can be used to complete the task.

Dry before and after

Dry before and after

Wet before dry

Wet front and wet back

Front wet, rear wet, single brake controller, left and right non-independent

For racing applications with many rules, there is also a more streamlined system that does not require four-wheel independent control. If you are as observant as I am, you will find that there is only one brake controller driving two hydraulic actuators in this system. If four-wheel independent control is required, two brake controllers are used in the picture above.

So here I have a question:

Why can't one controller control all four wheels independently?

But Brembo is an Italian brand after all, capiche? Long live understanding!

Easy layout

Pedal (simulator) can be placed anywhere

As long as the smart cockpit is advanced enough in the future, in theory you can drive in the car while looking at VR or a big screen in any posture.

Control

Foot feel calibration OTA upgrade is no longer a dream

Like the One-box system, the fully decoupled brake pedal can not only maximize the utilization range of kinetic energy recovery, but also simulate and adjust various styles of braking "feel" through software. In comfort mode, you can have a relaxing foot feel like a grocery cart, while in sports mode, you can have precise braking force control like a sports car.