[Norsk]

Interesting and precise technical info on the DSC systems in our BMW.

ESC = DSC

DSC is just the marketing term used by BMW.

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ESC utilizes known components

ESC will go down in history as the active safety system to transform the fastest from an optional feature at extra cost to an undeniable element of standard fitment. Thanks to its interactive design, ESC stabilizes the vehicle in all driving situations. No matter whether the car's driving off from a standstill, driving straight, or braking, ESC undeniably helps the driver evade a potential accident. Thanks to ESC, the driver retains control of the vehicle even in critical situations.

The electronic stability program contains the subfunctions of anti-lock braking (ABS) and traction control (TCS) as well as electronic brake-force distribution (EBD), engine-drag torque control (EDC) and active yaw-moment compensation (AYC). The first four systems concentrate solely on rotational wheel slip and vehicle dynamics in longitudinal direction. In this way, ABS reduces wheel lock during braking, TCS reduces the engine output and, in combination with EDC, brakes the wheels as they start to spin when the car drives off and accelerates. Interventions in the braking system like this are based on the physical principle that locked or spinning wheels are practically incapable of transmitting any cornering forces. And yet it's those forces that are needed to keep the vehicle steerable and controllable.

EBD and EDC serve primarily to control longitudinal slip. By means of the ABS sensors EBD determines the slip between wheel speeds at the front axle and at the rear axle, and can then make differentiated adjustments to the braking pressures. Once the degree of slip exceeds a certain amount, EBD keeps braking pressure at the rear axle constant or reduces it accordingly. EBD uses the computed values to provide maximum braking efficiency, even without ABS control. Engine-drag torque control is engaged during ABS braking. Once braking pressure is reduced, the speed of the drive wheels is not increased fast enough because the engine has a braking effect and creates a long-lasting wheel slip. This leads to reduced steer-ability in front-wheel-drive vehicles, and less stability in rear-wheel-drive vehicles. Under EDC, the engine management gets a command from ABS to quickly increase engine speed. The drive wheels are then released from disturbing drag torques and are able to transmit higher cornering forces.

Stabilization of a vehicle's transverse dynamics is only one of the areas intensively monitored by ESC and its affiliated subfunctions. ESC also senses and analyzes the rotary motion of a vehicle around its vertical axis. The driver is assisted in all his driving maneuvers, particularly in the avoidance of obstacles. Stabilization is achieved by decelerating one or more wheels before a dangerous swerving motion arises. Rotary motion of a vehicle around its vertical axis is known among engineers as 'yawing'.

Active yaw control (AYC) is made possible by means of a complicated sensor-device infrastructure. At the heart of the system is a yaw rate sensor found so far only in aviation and aerospace engineering. In the ESC from Continental Teves, the sensor element is shaped like two tuning forks joined together at their base. Emerging vibrations are converted piezo-electronically. During vehicle yaw motion, the tuning forks are deflected perpendicularly to the plane of vibration. The strength of the yaw rate corresponds with the deflection. In addition, the ESC's system electronics determines the car's current driving condition via two central processing units, and a sensor measures the lateral acceleration within a spectrum of +1.7 to 1.7 g (1 g = gravitational acceleration of 9.81 m/s2).

Software recognizes the driver's steering commands

ESC permanently compares the actual driving condition with the steering commands given by the river. The program's electronics recognize the direction in which the driver wishes to go via the ABS sensors and the steering-wheel motion, the latter being measured by another sensor placed directly at the steering-column assembly. If ESC detects any difference between the driver's wish and the current driving condition, the system starts acting up to 150 times a second. If ESC detects an understeer tendency it preferably decelerates the rear inside wheel and takes the vehicle back onto the desired course. If the car oversteers, making the rear end swing out, ESC decelerates the front outside wheel, creating an opposing moment to counterbalance the existing yaw moment, thus bringing the car back into a driving condition that requires only minor adjustment.

ESC intervention takes place within fractions of a second without the driver having to take any action. This is made possible by the ESC pump which, in large vehicles, can be assisted by a special brake boost function. ESC's control activity may, however, superimpose the driver's commands at the braking and accelerator pedals if those commands are recognized by the system as being wrong. In this way, ESC from Continental Teves can, for instance, reduce braking pressure on the inside wheels when the car is braking and cornering at the same time, in order to prevent any oversteering tendency. Like ABS and TCS, ESC pays attention to road surface conditions when it is in action. The system gives substantial safety benefits right up to the limits of physical possibilities not only on dry surfaces, but also in wet, snowy and icy conditions.



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This is how ESC corrects the situation when a vehicle is understeered

If the front wheels of an understeered vehicle drift outwards, braking applied to the rear wheel on the inside of the curve develops a compensating yaw moment which returns the vehicle to the desired course again.

This is how ESC corrects the situation when a vehicle is oversteered

If the vehicle threatens to oversteer with the rear of the car breaking away, braking is applied to the front wheel on the outside of the curve. The compensating moment operating in a clockwise direction turns the vehicle into the desired direction again.

[ONE_slow_m5]

Any idea where the yaw sensor is located on e9x?

[Welcome to NBA Jam]

Gotta love DSC. It is still one of the best stability control systems out there to date. It's so incredibly well integrated into the vehicle. Still blows my mind that it can make steering wheel corrections automatically if you have Active Steering.

Originally Posted by Blown__m3

Any idea where the yaw sensor is located on e9x?

I can't quite remember, but I want to say that it's under the center console. It's going to be located closest to the car's center of mass.

[justpete]

Annnnd exactly the reason it's been completely disabled in my car.

[John 070]

Thank goodness for the $250 repair of the dsc hydro pump. 5DF0 and F1 (aka trifecta) = $3,400 at the dealership.

Edit

"If the vehicle attempts to go 9 yrs without a big ticket repair, the DSC Hydro pump compensates by failing unexpectedly thereby sending the vehicle down BMWNA's desired repair course."

[thakid22]

More DSC90 features:

SoftStop/Comfort Stop - This program releases the rear brakes in the last few inches of a complete stop, making the stop smoother and less jarring.

ADB/ELSD - This program brakes an individual spinning wheel. It allows for more uniform and effective application of power in situations where one rear wheel has more accelerative traction than the other.

Brake Hold - Keeps the brakes applied momentarily after you release the brake pedal. It prevents the vehicle from rolling backwards on inclines during the time you move from the brake to the gas pedal.

Fade Compensation - Applies the brakes stronger for you when the brakes are calculated to be warm enough to experience fade. This is an attempt to maintain consistent pedal feel and response, even when the brakes are overheated due to use.

Brake Drying - Active when the windshield wipers are on, the brakes lightly apply automatically and systematically to wipe moisture from the disc/pad. Dry braking components stop better.

Brake Ready Support - Can't remember the correct name, but that is close. This program moves the brake pads closer to the disc if you quickly release the throttle, in anticipation of an emergency stop. This allows for more immediate breaking when your foot initially touches the brake pedal.

Hill Assist - Xdrive models - applies the brakes to maintain a steady speed down an incline without brake input from the driver.

DSC is truly amazing! And it's getting better with each generation. I just returned a 2016 228i loaner car and DSC there is smoother and less intrusive than the already good systems on my E90 and E60.