Page 1: Overview
Page 2: Safety, Agility, Traction, and Driving Pleasure All in One
Page 3: BMW xDrive
Page 4: The Arjeplog Testing Base
BMW Dynamic Performance Control - Greater Safety, Agility, Traction, and Driving Pleasure All in One.
Dynamic Performance Control serves to distribute drive forces precisely as required on the rear axle for a substantial improvement of driving stability and traction. In developing and implementing the underlying concept, BMW’s engineers focused not only on extreme driving conditions and fast bends.
Rather, the primary objective from the beginning was to improve driving safety, agility and nimble performance, as well as driving pleasure as such, particularly under everyday driving conditions. Hence, the less routined motorist will also benefit from all these advantages as soon as Dynamic Performance Control is introduced in series production. The bottom line, therefore, is that Dynamic Performance Control offers even greater safety reserves by providing greater stability.
Modern implementation of an old patent.
The idea behind this concept is not new: Back in the ’30s of the 20th century, Frenchman Pierre-Louis Chassagny registered patents for various concepts using a superimposed gearset. In 1970 Austrian engineer Walter Fleisch patented a similar idea for steering vehicles running on chains. And since modern electronics and mechatronics only available today offers to use all benefits in everyday motoring, the BMW Group and its engineering specialists have once again taken up this principle, applying it for regular use.
The special feature about BMW’s concept is that unlike other technologies, Dynamic Performance Control provides an appropriate distribution of drive forces, not only when accelerating but also in the overrun mode or with the brake disengaged.
In creating this new development now presented to the public for the first time in a BMW 530xi, BMW’s drivetrain and chassis specialists have added two superimposed gearboxes to a conventional final drive. Whenever necessary, therefore, these planetary gearsets may be integrated in the flow of power by way of multiple-plate brakes, distributing brake forces variably to the two rear wheels or applying significantly higher drive forces on the outer wheel in a bend.
Through this solution, BMW Group engineers have succeeded in optimising on the DNA to be found in every BMW: Thanks to this new drivetrain and suspension technology, the 530xi with Dynamic Performance Control is once again significantly better in terms of driving dynamics, handling, traction, and active safety. In addition, Dynamic Performance Control improves traction when setting off, directional stability when accelerating out of bends and, as a result, allows even faster lateral acceleration in a bend.
Enhanced tracking stability by varying the application of drive forces.
The effects of varying drive forces on the rear axle are demonstrated clearly by taking a vehicle running on chains as an example: To steer such a vehicle, the driver applies higher drive forces and, therefore, a higher speed on one of the two chains. The vehicle will then move in the direction of the chain with the lower drive forces and, accordingly, running at a lower speed. The radius achieved in a bend in such a process depends on the difference in forces and speed between the two chains.
Dynamic Performance Control uses this phenomenon inter alia to enhance tracking stability in a bend. The difference in drive forces thus generates a so-called yaw effect enabling the BMW 530xi to follow a circular line defined by the steering lock on the front wheels even more directly and with greater stability. The additional forces applied in this way quite literally “turn�' the car into the bend. Greater safety and driving pleasure in everyday motoring.
The advantages of the new system are obvious for all drivers also under everyday motoring conditions, for example when driving on snowbound roads in winter: Regardless of the road surface, the car follows the course the driver wishes to take far more precisely and at the same time Dynamic Performance Control reduces the steering effort. The steering itself responds more directly and requires far less correction.
The driver benefits from active support even in the most extreme driving situations such as a double lane change or on a tight mountain pass.
The greater steering precision, enhanced steering behaviour and superior tracking stability provided in this way give the driver extra safety and enable him to handle critical situations in greater more safely and with adequate reserves. Quite simply, he is able to anticipate how the car will behave. A particular advantage is that such enhanced tracking stability and superior control – and, as a result, driving safety – come out at all speeds.
In addition, Dynamic Performance Control also improves traction significantly on roads with varying surface grip (modal split) and when accelerating also out of a bend.
This function comparable to that of a limited-slip differential but not requiring any additional components proves its benefits above all under difficult conditions such as snow and ice, but also off the beaten track, when driving on roads without an asphalt surface.
Since, as a result, DSC Dynamic Stability Control is not required so often to give the driver additional safety and protection, a further advantage of Dynamic Performance Control is that the driver benefits from the full power of the engine under most driving conditions.
How Dynamic Performance Control works.
When driving in a straight line under normal conditions without requiring any specific distribution of drive forces, the final drive works in the same way as a conventional differential, drive forces being shared out equally through the differential to the drive shafts leading to the wheels.
Once actuated and with the electronically controlled multiple-plate brake on the superimposed gearbox cutting in, higher forces are automatically transmitted to one of the two drive shafts. Regardless of the drive power generated by the engine, therefore, the system may actively build up a difference in forces between the left- and right-hand rear wheel of up to 1,800 Nm.
In order to ensure optimum distribution of drive forces also under rapid load change and in quick manoeuvres to avoid an obstacle, etc on the road, the mechatronic system is required to generate the maximum force needed within 100 milliseconds. To do this, the control unit processes data and signals from other sub-systems such as the yaw rate of the car, its road speed, the steering angle, and engine torque all considered in complex algorithms. Actuators on the multiple-plate brakes then serve to transmit these control signals quickly and precisely.
When setting off on a surface with varying frictional coefficients (modal split), Dynamic Performance Control builds up locking forces helping to give the wheel with better grip more traction and thrust on the surface below.
This effect is comparable to that of a limited-slip differential.
A big advantage of this system compared with other concepts is that the distribution of lateral forces is masterminded not only under load, but also in overrun or with the clutch disengaged. Wherever there is no need to re-distribute the drive forces, the two planetary gearsets in the axle housing will run as one unit, meaning that the gears remain disengaged, the axle drive system operating like a conventional differential. And with the multiple-plate brakes in the axle drive remaining open, any losses are limited to the friction generated by the additional bearings and seals.
A perfect team: Dynamic Performance Control and xDrive.
BMW Dynamic Performance Control is suited fundamentally for all drive concepts and engines. But the advantages the system has to offer come out particularly in conjunction with BMW’s innovative xDrive, with these two concepts providing a perfect match.
While BMW xDrive distributes drive forces variably between the front and rear axle, Dynamic Performance Control ensures appropriate distribution of drive forces specifically on the rear axle itself in this way eliminating the inherent inclination of an all-wheel-drive car to understeer. So without requiring any concessions in driving dynamics, an all-wheel-drive BMW offers more neutral driving behaviour and makes it easier for even the less experienced driver to keep his car perfectly under control.
Dynamic Performance Control naturally complies in full with the highest European safety standards introduced in the automotive industry so far (ASIL D). To avoid malfunctions, the system, once introduced in series production, will have two redundant control circuits for the electronic control unit permanently monitoring one another. And should a defect occur all the same, the active distribution of drive forces is deactivated and the final drive operates like a conventional differential.
In the current phase of development Dynamic Performance Control does not yet use the great potential of electronically controlled distribution of lateral forces in full. But by networking the system with other control functions in the overall context of Integrated Chassis Management (ICM), Dynamic Performance Control may interact with other sub-systems in the same way as Active Steering, thus paving the way for additional safety and comfort functions.
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