BMW Motorcycle Traction Control
BMW Announces Motorcycle Automatic Stability Control
BMW has announced the availability of their first
motorcycle "stability control" (looks like traction control
system for street bikes.
The system uses the BMW Motorrad Integral ABS system
and advances it from a stand-alone solution acting only
on the brakes into a fully networked all-around system.
With this new generation of Integral ABS, BMW has
developed a foundation for additional dynamic riding
control systems with a reduction in technical
requirements and features. The new technology also
opens up the option in future for further-reaching rider
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, rather than the R1200R as has been
BMW claims that they are "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".
NOTE From Visitor "B.M.: "The article states
it is the "first system in the world serving to control
drive spin on a production motorcycles". At any
rate, it's wrong. Honda introduced the same thing
on their ST1100 ABS-TCS in 1992, 15 years earlier.
And it works great. It uses the ABS sensors as
does BMW, and it also modulates engine power also, as
does BMW. Seems BMW is 15 years late to the
BMW wanted to choosing the right development partner for both systems,
so they had to focus on that partner's specific competence
in control technology and the networking of functions
within the vehicle.
In recent years, major car
suppliers have become aware of the technical challenges
presented by the motorcycle with its specific riding
dynamics and the growing potential for motorcycle
control systems in the market.
The decisive point
in pre-selection of the development partner was the
willingness and ability to develop specialized 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.
BMW'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. Capitalizing 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. The result is stopping power and very
short stopping distances even without electrical power
assistance on the brakes.
The 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 automotive
applications, this control concept is now able to ensure
a very high standard of all-round comfort and
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 in other BMW
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
is claimed to provide a more direct feeling of the
brakes particularly important to the sports-minded
rider. Also, the rider should no longer have to
get used to any change in control or operation of the
brakes when switching over from a motorcycle without
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 rear brake 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.
Automatic Stability Control
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. BMW's system will allow the
rider 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, claims BMW.
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