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How does the active suspension that sees the holes of the road work?

Just over a year ago, we remembered the history of Bose’s active suspension, which adjusted automatically to reduce the body movements of the car, providing more comfort for the occupants. Unfortunately, the system never passed the prototype stage because it was too expensive at the time of its development and also because its creator, Amar Bose, retired before the technology needed to make this suspension affordable and popular.

This was only happen in 2013, when Mercedes-Benz launched its “Magic Body Control” system. You must remember him because of that ridiculously funny video with hens churning to the sound of Diana Ross’s Upside Down:

Even if you do not know the suspension, the chickens make it clear that it is a system that keeps the body stable regardless of what happens to the wheels. The system has nothing magical, but uses that name because instead of reacting to driver input and external factors, it anticipates what lies ahead and adjusts the suspension before the car goes through a hole or a spine, for example.

The magic is in the stereoscopic camera installed on the top of the car’s windshield. A stereoscopic camera – or simply a stereo camera – uses two or more lenses and the same number of sensors to achieve a stereoscopic effect that allows viewing in three dimensions. It seems complicated, but it is simply the same principle of human vision: with two points of view (our two eyes) we can perceive the depth of field and have the notion of the distance between objects on different planes.

You got the point, is not it? With a stereoscopic camera system a computer can “see” images captured in three dimensions, which means that the system can calculate the distance between the car and the obstacle. By using high definition cameras, the system is able to notice variations of up to 3 mm in height or depth of the surface ahead.

As the system ECU also has the car speed information, it can calculate the time until it reaches the obstacle. With the processed image, the ECU calculates how it will act on each of the shock absorbers and airbags of the suspension, controlling compression and return of the shock absorbers and pressure of the pneumatic springs.

The tilt, steepness, and dip control is a bit different: it uses motion sensors to compensate for weight transfers. If the car makes a right turn, for example, by sensing the change in steering wheel position and a start of roll the system stiffens the left side of the car suspension to contain the body movements by means of a hydraulic system that operates With up to 200 bar of pressure.

Monitoring is done constantly while the system is activated and the controls operate up to 130 km / h – ie in practically all situations of civilized use. The only drawback is that the system that reads the lane does not see in heavy rain or fog (or dust), so the control of the suspension to cancel the effect of the holes and irregularities only works with the clean time.

Another car that uses this hole detection system is the Ford Fusion Sport, the 330-hp V6 biturbo model sold exclusively in the US. The operation on the Ford, however, is a bit simpler and was derived from the system already offered in the Lincoln MKZ. It does not use cameras, but 12 high resolution sensors on the bottom of the front bumper to realize that there is an imperfection ahead.

When this happens, the system sends an electrical signal that retains the compression of the damper, holding the wheel in position and preventing it from falling into the hole. Another difference from the Mercedes system is that because it is based on sensors rather than cameras, it works even under adverse conditions of visibility, and its monitoring is constant.

The latest model equipped with an active system able to read holes is the Audi A8 Sedan. Being of a generation more modern than the other two models, it also uses a more complex system.

The basis of the Audi system are the stereo cameras, as in Mercedes, however they are capable of generating 18 images per second. Another difference is that instead of air bags and hydraulic shock absorbers, Audi is using a high-power electromechanical system (something made possible by its 48-volt electric system) consisting of an electric motor, a mechanical actuator and a rotating tube with A torsion bar attached to the suspension of each wheel.

When the system detects some imperfection in the lane ahead, the electric motor receives the signal from its control module and acts on the suspension also controlling compression and return of the shock absorbers. The reason for using an electromechanical rather than hydraulic system, as in the Mercedes, is the fastest speed of action – including in the roll control of the curves, since its action can be linked to the movement of the steering box. Here’s how it works in practice:

The Audi system still goes beyond comfort and also includes a safety feature: if the cameras and sensors detect the imminence of a T-side collision, the electric motors lift the side that will be reached by 80 mm to protect the occupants.

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