8 Apr 2020

Product Feature Focus: Active Sensor Bearing Technology for Improved Safety

Cars today come with more safety features than ever before. From Adaptive Cruise Control to Lane Departure Warning and Blind Spot Detection, many of these features have made driving safer and have assisted drivers in avoiding or mitigating collisions.

One such system, active sensor bearings (ASB), is a vital part of your vehicle’s wheel hub assembly. As automotive wheel bearings are safety critical components of your vehicle, ASB technology promotes greater efficiency in acceleration and braking, as well as sustains radial and axial loads. It easily helps to correct the functioning of different systems on modern vehicles.

Any failure on the part of ASB technology results in the inability of the vehicle’s electronic control unit (ECU) to capture speed information properly. This can cause stability control issues and involuntary and dangerous speeding. 

History of ASB technology 

In late 1997, SNR, a French bearing manufacturer, developed a new concept which integrated a magnetic seal onto automotive wheel bearings. This new smart sensor technology called “active sensor bearings” was initially put into production for Renault’s Laguna models.

Thanks to SNR licensing ASB technology to other bearing manufacturers, a number of European and Japanese vehicle manufacturers like Honda, BMW, and VW Audi Group have installed ASB technology in many of their new vehicle models. This technology has been extremely helpful in measuring wheel speed down to zero.

A breakdown of ASB technology 

As the name implies, active sensor bearings come fitted with a magnetic encoder. The magnetically encoded seal features a series of north and south poles that deliver data on the rotary speed of the wheel via a digital signal to the vehicle’s on-board computers.

The information sent by the magnetic encoder is essential to the operation of certain computer systems like your anti-lock braking system (ABS), hill start assist, electronic stability control (ECS) or electronic stability program (ESP), GPS and among others.

Difference between passive and active sensors

Vehicles on the road today use two types of wheel speed sensors to determine rotational wheel speed: passive and active. Passive wheel sensors have been around since the 1950s, when ABS systems were first introduced in commercial vehicles.

These types of sensors consist of a magnetic pole pin that’s surrounded by winded copper wire. When the wheel is in motion, the toothed tone wheel inside the wheel bearing hub passes by the magnetic sensor, inducing alternating voltage. 

This AC signal is used to monitor wheel speed information.

Active sensors like the ones in ASB technology use a multi-pole ring seal in place of the toothed tone wheel found in traditional passive sensors. Embedded in the ring is a magnetic encoder that works with the sensor that includes an integrated circuit which delivers a digital signal.

Advantages of active sensors

While both sensors perform the same function, active sensors are advantageous due to the fact that they are capable of signal detection at near-zero speeds or at a standstill, something passive sensors are incapable of doing.

Further, the integration of the magnetic seal enables active sensors to detect the direction of rotation.

The sensors in smart bearing technology like ASB are also smaller and lighter in design, come with a reduced number of parts, standardized components, and simplified wheel installation. All of these result in more precise data acquisition.

This active measurement of individual wheel speeds is used by your vehicle’s on-board systems to control vehicle dynamics. Without accurate interpretation of the speed data, your vehicle’s derivative safety systems (traction control, ABS, etc.) cannot provide corrective action when required.

The safety importance of ASB technology

Since passive sensors are prone to electromagnetic interference, vibrations, and temperature fluctuations, false cycling is more likely to occur.

False cycling describes the condition in which the ABS system is activated despite the road conditions not needing this cycle. Passive sensors typically cause false cycling during non-skid deceleration braking under 10 mph as passive sensors are incapable of signal detection under 7 mph.

False activation incidents involving the ABS system can cause a drop in stability control.

For the driver, false cycling can feel like a sudden drop in the brake pedal, a pulsating feedback, or a drop in power. This can potentially make the vehicle pull in an unwarranted direction or the driver might feel a reduction in braking power, making a longer than normal stop.

A lack of stability control due to a misinterpretation of wheel speed data can reduce vehicle safety.

As the brake pedal becomes less responsive, your vehicle may not be able to stop in an adequately safe manner. If false cycling occurs at an intersection, it may be impossible to steer and avoid an accident.

As active sensors continue to produce digital signal even at a standstill, your ABS system is not as prone to activating a false cycle. 

What’s more, even if a false cycle does occur, the advanced modules to come ASB technology deactivates the ABS system and turns on the ABS warning light, allowing you to brake in a safe manner.

With wheel speed sensors playing a critical role as a control parameter in many of today’s on-board computers, accurate transmission of data ensures multiple systems in your vehicle are able to optimally control vehicle dynamics.

Vehicles equipped with ASB technology not only experience increases performance and reliability, they also optimize for comfort and road safety.

Conclusion

Nowadays, drivers don’t have to look far to have their vehicle equipped with active sensor bearings. Additionally, certain tools such as ASB Sensor card from NTN SNR can easily help you check the magnetized seal likewise, the location to the sensor.

Nearly 90 percent of popular European vehicle models are equipped with ASB technology. If you have an older vehicle model that you’d like to be outfitted with ASB technology, talk to your trusted mechanic or technical service provider today.

As ASB bearings are fitted onto the wheel hub assembly in the same manner as a traditional wheel bearing, they can quickly do the work in no time at all.

If you’re in need of more reliable bearing speed measurements or are simply looking for a safer driving experience, consider installing ASB wheel bearings in your vehicle today.