INTEGRAL ABS and ASC - NEW RIDING DYNAMIC CONTROL SYSTEMS FOR BMW MOTORCYCLES

1. BMW's new ABS and ASC Riding Dynamic Control Systems. Short Version. 2. Three Generations of BMW Motorcycle ABS. Looking back at a Pioneering Achievement. 3. Function and Technology of the new Generation of Integral ABS. 4. Function and Technology of BMW's new ASC.

Entering its next generation, BMW Motorrad Integral ABS is taking a quantum
leap in the process of evolution, advancing from a stand-alone solution
acting only on the brakes into a fully networked all-round system. Offering the
new generation of Integral ABS, BMW Motorrad provides the foundation
for additional dynamic riding control systems with a reduction in technical
requirements and features. And following the customer's wishes, this new
generation also opens up the option in future for further-reaching rider
assistance functions.

The first step in this direction is BMW Motorrad ASC Automatic Stability
Control available as of 2007. This first system in the world serving to control
drive spin on a production motorcycles is being introduced as an optional extra
on the touring models in the BMW K and Boxer Series.

Once again, therefore, BMW is acting as the pioneer in the introduction of
advanced safety technologies on the motorcycle. This further enhances
the leadership which BMW Motorrad has shown in the area of active safety
for more than 15 years.

Choosing the right development partner for both systems, BMW Motorrad obviously
had to focus on that partner's specific competence in control
tech¬nology and the networking of functions within the vehicle. In recent
years, major car suppliers have become aware of the technical challenges
present¬ed by the motorcycle with its specific riding dynamics and the growing
po¬ten¬tial for motorcycle control systems in the market. The decisive point in
pre-selection of the development partner was the willingness and ability to
develop specialised solutions suitable for use on BMW motorcycles. So taking
this into account, joint development of the new generation of ABS brake
technology started together with Continental-Teves in early 2003.

Integral ABS.
BMW Motorrad's new Integral ABS technology has been developed separately from
the previous system and the entire layout of the system has been newly
conceived from the ground up. Capitalising on progress in technology in both
hydraulics and electronics, the development engineers have succeeded in
simplifying the architecture of the system while at the same time enhancing its
functions to an even higher standard. The result is supreme stopping power and
very short stopping distances even without electrical power assistance on the
brakes.

BMW Motorrad's new Integral ABS is no longer based on the plunger
principle or, respectively, the ram pressure process used on previous
generations, but instead is conceived as a valve system. Carried over from
auto¬motive applications, this control concept is now able to ensure a very
high standard of all-round comfort and convenience in every respect. In
particular, feedback of brake pressure modulation on the brake lever has been
reduced by recent development of the control valves and management to such an
extent that
it no longer has any kind of adverse effect, thus paving the way for
introduction of the new system also in the topmost segment of BMW motorcycles.

The new Integral ABS system applies brake pressure on the front wheel brake
solely by means of a hydraulic circuit, thus acting entirely in response to the
operating forces applied on the hand lever. This, in turn, ensures a more
direct feeling of the brakes particularly important to the sports-minded rider.
And now the rider no longer has to get used to any change in control or
operation of the brakes when switching over from a motorcycle without ABS.

The new system naturally maintains the proven semi-integral function,
that is automatic activation of the rear-wheel brake when operating the
front-wheel brake. Pressing the footbrake alone, however, the rider, as in the
case of a conventional system, activates only the wheel brake at the rear.
As with the previous system, the advantages of this integral brake are ideal
brake force distribution on both wheels under all conditions, naturally
taking load conditions into account, as well as enhanced control enabling the
rider to detect at an early point the risk of the rear wheel lifting off
when applying the brakes all-out, and to take appropriate counter-action.

To provide the desired integral function, brake pressure for the rear-wheel
circuit is generated and built up by an electronically controlled hydraulic
pump. This offers the advantage of pressure management and control completely
independent of the front wheel circuit - which is the prerequisite for dynamic,
adaptive and, ultimately, consistently ideal brake force distribution to
the rear wheel as well as fully independent brake management and control.
In the event of any deficiencies in the hydraulic pump or electrical
components, the rear-wheel brake acts hydraulically as with a conventional
system, overriding the integral function. This has no effect on the proper
operation of the front-wheel brake, the only difference being that the ABS
function is no longer operative in the event of such a deficiency.

ASC.
Automatic Stability Control is a meaningful, additional assistance function
particularly on a high-torque motorcycle and when riding under varying
conditions with slippery surfaces. Indeed, ASC is the logical counterpart to
ABS.
Automatic Stability Control prevents the rear wheel from spinning uncontrolled
when accelerating all-out and thus avoids any loss of side forces and stability
which otherwise would make the rear wheel swerve out of control. Lift-off
detection and intervention serves furthermore to prevent the front wheel from
moving up when accelerating under full power. Acting together, these two
functions enhance riding stability and thus help to ensure a higher standard of
safety on the road. And last but not least, the rider is able to deactivate ASC
at any time, also while riding.

Like ABS, ASC is naturally also subject to certain restrictions in bends due to
the riding physics of a motorcycle. And it is essential to note that ASC is
not able to push forward, let alone override, the physical limits to the
stability
of a motorcycle when leaning over in a bend.

In its basic principles, the system and its various functions are quite
straight forward: The ABS wheel sensors determine the speed at which the wheels
are turning. Registering any sudden change in the difference in
speed front-to-rear, the electronic control unit is able to detect any risk of
the rear wheel spinning, engine management responding immediately by
intervening in the ignition angle to take back engine power. Should this not be
sufficient, that is should a greater reduction of engine power be required,
fuel injection will be cancelled out for a certain time.

This kind of control and management is fast and sensitive, with any effects
on riding comfort and dynamics being virtually negligible.