BMW Dynamic Peformance Control in Detail

Press Release

Overview Developing Dynamic Performance Control, BMW has created a drivetrain and chassis control system offering the driver an even more intense and safer experience of sheer driving pleasure. In particular, the car's dynamic performance and lateral acceleration become a genuine, tangible experience thanks to enhanced steering precision and tracking stability at all speeds. Optimum distribution of lateral forces on the rear axle. The term "Dynamic Performance Control" defines a mechatronic system serving to distribute drive forces infinitely to the rear wheels regardless of engine output. To provide this effect the final drive is combined with two superimposed gearsets and two electronically controlled multiple-plate brakes serving to infinitely vary the otherwise symmetrical distribution of drive forces when driving in a straight line. The difference in forces potentially generated in this way of up to 1,800 Nm provides a significant improvement of steering behaviour, steering precision, tracking stability, and traction in general. At the same time the steering responds even more directly and the driver is required far less often to intervene in the steering, just as the electronic control systems are required far less frequently to stabilise the car. Suited for all engines and drivetrains. The special highlight of this unique development by BMW is that for the first time this system is able to actively distribute drive forces not only in the overrun mode and with the clutch disengaged. As a result, Dynamic Performance Control is suited for both standard and all-wheel drive. In all, therefore, Dynamic Performance Control enhances not only active safety, agility and motoring comfort, but also the joy of motoring through an even higher standard of steering precision, tracking stability and traction. Precisely this is why this innovative technology offers the customer genuine benefits in cars with all engines, Dynamic Performance Control giving even the "average" driver tangible benefits in everyday motoring at all speeds and helping him control his car in superior and safe style. Hence, sheer driving pleasure becomes an even more significant issue even in models with a "basic" engine. Dynamic Performance Control and xDrive: the perfect pair. The combination of Dynamic Performance Control and BMW's intelligent xDrive all-wheel drive system varying longitudinal forces infinitely between the front and rear axles forms an ideal team. Together with appropriate distribution of drive forces on the rear axle, this provides an unprecedented standard of driving stability, dynamism and agility re-defining the benchmark in drivetrain and chassis technology. The system also neutralises the inherent inclination of cars with all-wheel drive to understeer, thus ensuring particularly smooth and neutral driving behaviour. And even the less routined motorists will feel the difference, finding it a lot easier also in critical situations to keep his or her car under control. Intelligent all-wheel drive: BMW xDrive. The particular ability of variable all-wheel drive introduced for the first time by BMW in 2004 is that this high-tech system significantly improves both traction as well as dynamism and motoring safety all in one. Under normal driving conditions, permanent all-wheel drive distributes engine power at a ratio of 40 : 60 front-to-rear. BMW xDrive then responds quickly, precisely and variably to any change in road or driving conditions by changing the distribution of drive forces in a longitudinal direction. Incorporating a power divider with an electronically controlled multiple-plate clutch, BMW xDrive directs the power of the engine to where it can be used most effectively. Hence, all-wheel drive acts against any tendency to over- or understeer in a bend at an early point in time, improving driving dynamics in the process. Traction is thus optimised also on difficult terrain, since the system directs drive power instantaneously and variably to precisely the right wheels with a higher frictional coefficient. To distribute drive forces quickly and precisely in the longitudinal direction, xDrive all-wheel drive, DSC Dynamic Stability Control, engine management and, if fitted, Active Steering are all networked with one another by means of Integrated Chassis Management. Making its world debut high up in the north of Sweden. This new technology is not being introduced to the public for the first time at one of the major motor shows, but rather at the BMW Group's newly established Test Centre in the north Swedish town of Arjeplog. Here, 56 kilometres or 35 miles south of the Polar Circle, Dynamic Performance Control in the BMW 530xi with xDrive all-wheel-drive technology can demonstrate convincingly on snowbound country roads and test tracks, as well as prepared ice tracks, to what extent it is able to increase safety and at the same time enhance the car's agility and nimble performance. Cars equipped with Dynamic Performance Control show almost the same behaviour as a go-kart, offering sheer driving pleasure of the highest standard starting at low speeds and with a higher level of safety than ever before. 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. Safe, Superior and Pre-Emptive - BMW xDrive. Never before was BMW able to offer its customers such a wide range of all-wheel-drive cars as in the 2006 model year. Indeed, comprising no less than four model series and almost 30 different models, the choice of all-wheel-drive options offered by BMW is truly outstanding. Precisely this is why BMW is in the lead also in this growing market segment, with BMW xDrive proving its merits in vehicles of all kinds. So it is no surprise that one out of every four BMWs delivered to customers today comes with all-wheel drive. More traction and greater precision for enhanced driving pleasure. Supreme driving characteristics and optimum traction on all roads and surfaces – these are “only� two of the benefits offered by BMW’s intelligent xDrive permanent all-wheel-drive system combining the dynamic performance of rear-wheel drive with the traction benefits of drive power going to all four wheels. The electronically controlled all-wheel-drive system distributes drive forces within fractions of a second, feeding engine power precisely to the right axle where this power can be translated directly into traction and forward thrust on the road. This variable distribution between the front and rear axle means a significant improvement of driving dynamics, agility, driving stability, and motoring comfort in practice. And these substantial benefits of BMW xDrive come out clearly in all of BMW’s all-wheel-drive models. A further point is that BMW xDrive offers its positive effects not only when traction problems have already become evident. Instead, the system is able to determine in advance whether a loss of traction is developing and is therefore able to take appropriate counteraction in good time. Precisely this explains why xDrive sets the standard in all-wheel-drive technology. For while conventional all-wheel drive only responds to the wheels once they have started spinning, xDrive acts in advance, actively withdrawing drive power from the axle with less grip and re-distributing this power to the wheels benefiting from greater traction on the road beneath. The central “brain�: the electronically controlled clutch. Starting at the power divider behind the gearbox or automatic transmission, drive power is initially transmitted to the rear axle via the main shaft. The main shaft incorporates an electronically controlled multiple-plate clutch serving in turn to convey some of the torque via a layshaft to the front axle. When driving in a straight line under normal conditions, 40 per cent of the drive power goes to the front, 60 per cent to the rear axle. As a result, a BMW featuring xDrive is virtually just as agile and dynamic in everyday motoring as a BMW with rear-wheel drive. Whenever necessary, however, drive forces may be transmitted variably and with infinite control to the front and rear axles by way of the multiple-plate clutch. The multiple-plate clutch within the power divider takes only 100 milliseconds to completely open or close, performing this operation so smoothly and gently that the occupants will not notice anything. What the driver will notice, however, is the even more harmonious behaviour of the car in a bend, the reduction of steering forces required and the higher standard of driving comfort, with DSC Dynamic Stability Control cutting in far more rarely than otherwise in controlling the brakes. BMW all-wheel-drive cars do not suffer the disadvantages of permanent all-wheel-drive systems with a rigid, pre-determined distribution of drive forces such as undue tension in the drivetrain and steering under high frictional forces. This, quite simply, is because the axles are completely disengaged from one another in extremely tight bend radii, e.g. when manoeuvring, with the traction potential of all-wheel-drive being used again only when the wheels are subject to excessive slip. Networked system for even greater safety. Establishing a network with DSC Dynamic Stability Control permanently measuring and determining important parameters such as the steering angle, lateral acceleration and the yaw rate of the car, xDrive is able within fractions of a second to respond to any inadmissible deviation from ideal driving behaviour before the driver even notices what is happening. Drive forces are distributed between the front and rear axle in such a way that the car builds up a yaw force counteracting any inclination to under- or oversteer. In most cases, therefore, the car will stabilise without requiring any intervention in the brakes by DSC. To distribute drive forces quickly and precisely, the xDrive all-wheel-drive system, DSC and engine management are all connected to one another by ICM Integrated Chassis Management. The system is therefore able to intervene in the brakes as required parallel to the distribution of drive forces in order to enhance both traction and driving dynamics. And if necessary, engine management may also adjust and vary the drive forces. Through this intelligent network, the xDrive all-wheel-drive system is able to respond quickly and precisely to any change in driving conditions, in the process increasing both safety and driving dynamics by a significant margin. In the new BMW X5 even the optionally available Active Steering is integrated in this all-round network. Whenever the car oversteers, when countersteering forces are required, or in braking manoeuvres on surfaces with a varying frictional coefficient (modal split), appropriate but discreet countersteering is able to prevent the vehicle from serving out of control, ensuring that the car regains its driving stability. Distributing drive forces as required. Under normal conditions, drive power is distributed 40 per cent to the front and 60 per cent to the rear. But under very dynamic conditions or on road surfaces changing substantially, the distribution of drive forces may be varied infinitely as required. The system is designed to completely disengage the front axle in an extreme case or, going to the other extreme, to connect the front axle rigidly to the axle at the rear. The rigid connection of the two axles established when required is the same as a 100 per cent longitudinal lock with conventional all-wheel drive on some models. Superior handling under all driving conditions. BMW xDrive compensates even an abrupt change in gas and engine load so smoothly and gently that the driver will not even notice any change in the distribution of drive forces. In bends xDrive reduces both under- and oversteer by distributing drive power quickly and sensitively between the front and rear axles. Whenever the rear end of the car starts to swerve round (oversteer), the multiple-plate clutch will transmit more drive power to the front wheels, allowing the rear wheels to build up more side support and stabilise the car. And being combined with DSC, BMW xDrive recognises the risk of oversteering at a very early point in time, intervening before the driver even notices what is happening. When understeering the car “pushes� out of a bend over its front axle. In this case the drive power conveyed to the front axle is consistently reduced, with up to 100 per cent of the drive power being conveyed to the rear wheels in an extreme case. So only if over- or understeer cannot be compensated by variable power distribution alone will DSC be activated in addition, intervening in the brakes and, if necessary, reducing engine power. BMW cars featuring xDrive are particularly agile and nimble on fast but winding mountain roads. Because with the rear wheels easily tending to spin when accelerating dynamically out of a bend or hairpin, BMW xDrive instantaneously diverts some of the drive power from the rear axle to the front axle. BMW’s Test Centre in Europe’s “Refrigerator� - The Arjeplog Testing Base. To ensure that new cars and components are able to meet global requirements in all climate zones, they also have to be tested under the extreme conditions of Arctic winter, with all the specific requirements and demands involved in such a situation. And to give BMW’s engineers and mechanics optimum working conditions at all times during the winter months, the BMW Group opened its own Test Centre in Arjeplog, northern Sweden, in March 2006. Located only about 56 kilometres or 35 miles from the Polar Circle and involving an investment by the BMW Group of approximately Euro 16 million, the Arjeplog Test Centre now concentrates all the winter testing activities of the BMW, MINI, and Rolls-Royce brands at one central location. Specialists from various divisions as well as employees working for BMW system suppliers enjoy optimum conditions here in harmonising, say, the drivetrain, chassis and ancillary units and putting them through their paces in the car. Driving on iced-over lakes and snowbound roads is not only an extremely tough test under extreme conditions in the coldest weather, but also a particular challenge to new chassis and drivetrain systems such as Dynamic Performance Control. Optimum working conditions in the coldest weather. BMW’s ultra-modern test centre boasts spacious offices equipped with the most advanced technical features, as well as two workshops with 50 vehicle workbays. A heated garage is available for 25, an unheated hall for 60 test vehicles, in addition to 164 outdoor parking spaces, 80 of which feature an engine warmer connection. And should the winter weather not be cold enough even in Arjeplog, 18 climate chambers are available to cool down the cars being tested to – 30 °C. A filling station and a washing hall as well as various measuring and testing circuits are also provided on-site. In laying out and building the test centre, particular consideration was also given to the special demands made in testing and servicing vehicles with hydrogen drive. And last but certainly not least, a secure network line integrates the Arjeplog Test Centre into the BMW Group’s data and information network at the Research and Innovation Centre in Munich. 740 metres (2,427 feet) circuit, 3.2 kilometres (1.98 miles) of heating pipes.< /b> Covering an area of 28 hectares or 69 acres, Arjeplog also offers a 740-metre-long test circuit, a driving dynamics track measuring 660 metres (2,165 feet) in length, asphalt surfaces which may be either heated or cooled, a hill-climb section with gradients between 10 and 25 per cent, a mountain pass section as well as a modal split and chessboard track for driving and brake tests on varying surfaces. To control the temperature of the test tracks, no less than 3.2 kilometres (1.98 miles) of heating and 1.8 kilometres (1.1 miles) of cooling lines have been fitted into place. From November to April, specially prepared ice test tacks are available in the immediate vicinity on Lake Kakel sufficiently frozen over during this time of the year and therefore offering the opportunity to conduct driving tests on the lake under the most demanding conditions. An important economic factor for the region. The BMW Group has been conducting tests in Arjeplog for many years, making a significant contribution to the development of this small town, which in the meantime has become the most significant winter test centre for the entire automotive industry. Apart from climate conditions and the local geography, the low population density in the Arjeplog region is also an advantage for testing cars in this area. In this part of Sweden with the sparsest population density throughout the entire country, temperatures between November and April generally remain relatively consistent at an average of – 10 °C, although from time to time the thermometer may drop to – 40 °C and even lower. The almost innumerable lakes in the region are frozen over from October until May, with ice up to one metre thick able to take the weight of a passenger car and even a truck. All kinds of test tracks with varying frictional coefficients can be prepared on the ice and subsequently used for a relatively long period. And on account of the sparse population density, the noise emissions caused by testing cars hardly give rise to any criticism. All buildings at the Arjeplog Test Centre, where 11 employees from the region are employed by the BMW Group for the whole year, were built on behalf of the BMW Group by Swedish companies in typical local style. The test teams are accommodated and receive all their supplies from local service providers, who also take care of and prepare the test tracks. So again for this reason alone, the new Test Centre is an important economic factor for Arjeplog and the entire Province of Norrbotten. Between November and March an average of 100, in peak times up to 200, BMW Group engineers and mechanics work at the Test Centre, most of them spending two weeks at the location. The ongoing presence and integration of nearly all system suppliers on the spot also helps to facilitate testing operations by the BMW Group and streamlines the process of development.