On the ZX-10R, KIBS (Kawasaki Intelligent anti-lock Brake System) uses some of the bike's traction control sensor inputs (in addition to wheel speed) to more accurately control braking during a panic stop. On the ZX-10R, KIBS (Kawasaki Intelligent anti-lock Brake System) uses some of the bike's traction control sensor inputs (in addition to wheel speed) to more accurately control braking during a panic stop.

Safety vs. Performance of Rider Aids

Written by  on Thursday, 09 February 2012 00:14

Even though traction control and ABS have only recently become more prevalent on sportbikes, it's been 20 years since those particular riding aids were introduced. Traction control was first used on Honda's ST1100 in the early '90s, while ABS first appeared on BMW's K100 in 1988. Much of that delay can be attributed to the difficulties manufacturers have faced in combining both safety and performance in cost-effective packages. Motorcyclists, as always, are reluctant to accept a safety feature if it impacts performance too much, and it is only recently that the performance of these rider aids has reached an "acceptable" level.

A traction control system designed for safety can be a relatively simple affair, based on an on/off algorithm. On a slippery street or going over a patch of gravel, the goal is to minimize slip, or wheelspin, under acceleration; if the rear wheel spins faster than the front or if engine rpm increases too quickly, power is cut. Designed to intervene at the slightest hint of a traction loss, however, such a system is subject to falsely activating. And if you are trying to get around a racetrack quickly, that false activation slows you down. A performance traction control system, on the other hand, is designed to optimize slip, as some wheelspin can actually improve traction. And at the same time, it must eliminate the false activations that cut power unnecessarily. From details of the various manufacturers' systems, it's evident that just as much effort in their development was focused on minimizing false activations as on managing slip once it is properly detected. On a production sportbike, a single system must account for the extremes of both safety and performance: A street rider may encounter a wet manhole cover on a dry road, and the traction control must manage both transitions (on and off the manhole cover) appropriately. On the racetrack, the system must accommodate a wide variety of weather and pavement conditions in addition to rider skill. It's no wonder that such systems end up with multi-level adjustability.

Turning to ABS, the same compromises must be made: A single system for both performance and safety must maintain traction at all times but not sacrifice stopping distance or distract the rider with false activations. The ABS on Kawasaki's ZX-10R is of particular note here, because the company has incorporated some of the attributes of a performance traction control system into its ABS. The attached graph shows the ZX-10R's KIBS (Kawasaki Intelligent anti-lock Brake System) using "small-increment pressure management" and "minimal intervention" to better modulate front wheel speed for smoother operation - again, optimizing slip rather than a simple on/off approach. And just as with traction control, the system looks at rpm, clutch actuation, gear position and throttle position (in addition to front and rear wheel speeds) for a more complete picture of what is actually happening rather than relying on wheel speed data alone.

The system works. In a test of three ABS bikes I helped conduct for Sport Rider magazine, the Kawasaki showed consistently short stopping distances with little of the feedback or pumping at the lever usually associated with ABS. Part of the credit goes to Bosch and its motorcycle-specific ABS module, but also to Kawasaki for making full use of that module. My article in the February/March issue of Inside Motorcycles covers more details of the system, as well as other electronic rider aids currently available, but looks more at the performance aspects rather than the safety aspects. The good news is that all this development on the performance side of rider aids in helping with safety as well. Motorcycles with ABS today stop quicker than those of a few years ago, and the systems work in a wider variety of situations with fewer distractions to the rider when they activate. Likewise, current traction control systems not only work better on the racetrack, but also they are almost transparent in operation and increasingly effective at keeping the average street rider off the ground.

Sometimes, in the rush to analyze and promote the racetrack performance of a new technology, the safety aspects for the street rider get brushed aside. Luckily, the manufacturers keep both in mind and make progress so that everyone benefits.

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Last modified on Thursday, 09 February 2012 11:54
Published in Andrew Trevitt

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