July 8, 2006 BMW’s announcement of its next generation Integral ABS this week could easily be overlooked as just another slightly better mousetrap, as anti-lock braking is not new. Indeed, in terms of function, the new ABS is not nearly as significant as the underlying technology and what it will mean for the future. The new Integral ABS incorporates the braking system into a fully networked system and provides the foundation for additional dynamic riding control systems. The first step in this direction will be known as BMW Motorrad ASC (Automatic Stability Control) and will be introduced on both K and R series motorcycles as an option next year. The idea behind ASC is to prevent the rear wheel from “spinning up” when accelerating on slippery surfaces or the front wheel from getting airborn under acceleration. ASC is the logical counterpart to ABS. 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. The immediate response is to interrupt the ignition to reduce engine power. If this is insufficient to restrict wheel slip, fuel injection is also interrupted. Of course the rider is able to deactivate the ACS at anytime, even on the move. Acting together, these two functions enhance riding stability and thus help to ensure a higher standard of safety on the road.
ASC will be the first system in the world to control driven wheel spin on a production motorcycle, and will be introduced as an option on touring models in the BMW K (four cylinder in-line motor) and R (horizontally opposed twin cylinder AKA Boxer) Series motorcycles.
Work developing the new motorcycle system began in 2003, with BMW Motorrad working closely with Continental-Teves, which has worked on automotive braking and traction systems for many years.
The new Integral ABS technology has been developed separately from the previous motorcycle ABS system with the entire layout conceived and built in its entirety. Capitalising on progress in technology in both hydraulics and electronics, the development engineers were able to simplify the system while at the same time enhancing its functionality. The result is claimed to be “supreme stopping power” and very short stopping distances even without electrical power assistance for 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 based on a valve system. The new control concept is a development of the system used in motor cars. In particular, brake pressure modulation feedback at the brake lever has been reduced by the development of the control valves and management, removing unpleasant effects.
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 force applied by the brake lever. Sports riders will enjoy this new level of control and feedback response. It also means riders who switch between machines with and without ABS should notice no difference in braking operation.
The new system naturally maintains the proven semi-integral function. This provides automatic activation of the rear-wheel brake when the front brake lever is operated. Depressing the footbrake alone activates only the rear brake.
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. It also gives early warning of the rear wheel lifting when braking harshly, allowing the rider 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 independently 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.