The recently-formed NTN / SNR Roulements association has produced its first jointly-developed bearing -- a wheel bearing hub assembly unit offering dramatically higher wheel speed data resolution.

With high-resolution magnetic Hall-effect sensors, the new hub units can provide automakers an electronic interface offering far more precise rotation and positioning signals.

The higher resolution signals allow today's advanced electronics to sense and react more quickly to changes in vehicle speed, cornering and braking.

In the past, going for a higher resolution has meant each individual signal had to be proportionately weaker in order to avoid interfering with each other. As the magnetic triggers get closer together, they tend to overlap.

hub unit (courtesy NTN)

NTN said its breakthrough in offering higher resolution, "was made a reality by blending SNR’s magnetic sensor technology where it’s magnetic encoder achieved resolution 40 times that of conventional types." In addition, NTN's encoder can distinguish whether a wheel is turning forward or backward.

All are components of increasingly sophisticated vehicle braking and dynamic stability control systems. These systems can also provide control over power or braking available at each wheel individually, as well as control differential lockup, torque distribution, and a wide variety of other active drivetrain controls.

In order for the next-generation electronic stability aids to work to their potential, however, the key piece of information is each wheel's rotation speed. Higher resolution sensors provide more accurate wheel speed measurements, and at a higher sampling frequency (more signals per wheel revolution).

Early electronic and ABS systems had slow, rudimentary sensors sending a wheel speed reading once or twice every revolution. Today's most advanced systems, such as used in racing cars and high-end sports cars, offer up data several hundred to several thousand times for each wheel revolution.

Advancements in on-board computer speed and sensitivity allow the processors to make full use of the data, allowing microsecond-to-microsecond control over the vehicle's stability profile.

An automotive electronics engineer recently told eBearing he expects wheel bearing hub units will soon have to include electronics not just for high-resolution wheel speed sensors but also potentially to measure strain and lateral loading. Future generations of wheel bearings are already expected to include active data monitoring to sense when the bearings are reaching the end of their service life (via noise and vibration measurements, for example, likely accessed through the OBD II port).

Last year, NTN and SNR came to an agreement that will give NTN controlling interest in SNR. This agreement will yield a hub bearing world market share of 22%. NTN’s goal is to increase its world market share to 26% by March 2010. (Market share value is NTN’s estimation)

article: NTN will acquire SNR Roulements