Class of 2010: Traction Control Systems - Guardian Angels

Understanding the electronics that keep your tires in line

By Ari Henning, Photography by BMW, Ducati

While no traction-control system can redefine the laws of physics, the electronics packages we sampled in this year's sportbike shootout certainly feel like they do. The premise underlying traction control is straightforward: The bike's onboard computer detects wheelspin and momentarily reduces power in order to regain traction. In reality, even the simplest systems involve multifarious sensors and complex response matrixes, and must make hundreds of nearly instantaneous computations and commands in order to keep the rear contact patch from slipping out from under you when you get greedy with the throttle. The fact that this intervention is almost imperceptible from the seat-all the TC-equipped bikes we tested have some sort of visual display to notify you when it's in action-is a testament to how advanced and finely tuned these systems are.

BMW was the first manufacturer to offer traction control on a production bike, although the Automatic Stability Control available on the 2007 K and R-bikes was never officially described as such. The Dynamic Traction Control on the S1000RR is properly named, and here's how it works. The first step is determining and comparing wheel speed, for which the S1000RR uses the anti-lock brake system's sensor rings. As such, DTC is only available on bikes equipped with the optional Race ABS. Engine rpm, throttle position and gear position are also sampled, as well as lean angle and rate of acceleration as determined by a pair of gyroscopes contained within a "sensor box" located under the seat. An updated BMSK-P (German for ECU) contains the microprocessors and software required to analyze the data, and references the selected drive-mode parameters before making a decision regarding when and how to curb power output.

Factoring lean angle into the equation is what separates DTC from ASC and makes BMW's latest system dynamic. As you toggle through the four drive modes from Rain to Slick, the DTC not only increases the amount of permissible wheel slip, but also adjusts power delivery (via the bike's E-gas fly-by-wire throttle) depending on lean angle and the amount of throttle being applied, and also limits wheelies. The Race ABS settings are incorporated into that arrangement as well, one advanced feature of which is anti-lift control for the rear wheel under braking. The result is a beautifully integrated and flexible stability package.

So what happens when the rear starts to spin, and how does the computer reign in the S1000RR's 174 horses? When tire slip is detected, the ECU curtails engine output by first retarding spark and, if needed, by adjusting the throttle butterflies and fuel flow. While the Ducati 1198S and MV Agusta F4 rely solely on altering the ignition angle and fuel flow to curb power, the BMW can actually close the throttle ever so slightly to arrest a slide and keep the tires in line.

Ducati's traction-control system (also dubbed DTC, for Ducati Traction Control), introduced on the '08 1098R, monitors wheel speed and controls power in much the same manner. Developed through the MotoGP and World Superbike teams, DTC was the first competition-grade traction-control system available to the public. The upgraded setup on the 1198S (and current 1098R, Multistrada 1200S and Streetfighter S) is exponentially smarter than that first system, and is destined to improve further as the race teams continue to refine the software.

Ducati's system uses a separate, dedicated ECU that resides in the bike's tail and contains an accelerometer that registers lean angle and acceleration rate. Like the S1000RR, the 1198S also polls throttle-position, gear-position and engine-speed sensors. For every 100-rpm increment, there are hundreds of possible data combinations and corresponding digital responses. That sophistication is why the system functions so flawlessly; the only telltale sign is a slight backfire when the system is engaged.

DTC works wonderfully to control mid-corner slides, but also allows you to wheelie out of turns. David James, Ducati Superbike Family Manager, explains this dichotomy: "The ECU contains data gathered during thousands of hours of track and road testing, and it knows what the bike's situation is [wheelying versus spinning the tire] based on that criteria, and responds accordingly." If that sounds like the ECU has been blessed with artificial intelligence, dig this: Under certain circumstances, such as when Level 7 or 8 is selected and the rider is leaned over in a low gear and calls for a lot of throttle, the computer will actually predict wheelspin and intervene by limiting power in anticipation of a slide.

The traction control on the MV operates on the same principle as the BMW and Ducati-by monitoring the rate of change in wheel speed-but the technical arrangement is much simpler. "Our aim was to introduce a reliable traction aid without adding a lot of components or technical complications," allows Chief Electronics Engineer Mauro Marelli. "We built the system using existing sensors with only the addition of software to the ECU." The ECU relies on the crank-position sensor to monitor rpm and detect wheelspin, and then references the selected TC level, gear position and throttle position to determine the proper ignition and/or fueling reduction. Despite its relative simplicity, the MV's TC system (which doesn't even have a fancy acronym) performs much like the others.

If MV's method is any indication, it won't be long before the majority of motorcycles come with some form of traction control. As more motorcycles adopt ride-by-wire throttle assemblies, the final component of the traction-control puzzle will be put in place. From there, all that's needed is a savvy software engineer, and every bike will come with an electronic guardian angel.

Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!

*Please enter your username

*Please enter your password

*Please enter your comments
Not Registered?Signup Here
(1024 character limit)
  • Motorcyclist Online