Exploring the technology behind cornering ABS and traction control

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A technological revolution is transforming biking as cornering ABS and lean-sensitive traction control, powered by inertial measurement units (IMUs), become the norm even on mundane models, all thanks to tiny electronic components called Micro-Electro-Mechanical Systems, or MEMS.

These miniscule devices, which look much like a computer chip, are essential for the gyroscopes and accelerometers that the on-board computers on modern bikes’ safety systems rely on. They can detect lean angle, acceleration, and whether your bike is pitching (tilting forwards or back) or yawing (turning in relation to the direction of travel).

With that information, the bike’s on-board computers can tell the ABS and traction control systems exactly when they need to intervene. While computer chips have their origins back in the 1950s, MEMS weren’t mooted until the late 1980s, and have only become widely available in this century.

Motorcycles use two distinct types: accelerometers and gyroscopes. MEMS accelerometers use weights (called ‘seismic masses’) sealed in a vacuum and supported by silicone springs. When the MEMS unit is moved, inertia means the weights try to stay put, so by measuring their position in relation to the rest of the unit, the system can detect the direction and level of acceleration.

The seismic masses feature intricate shapes that interlace with corresponding fixed- position sensors with an electric current flowing through them. As the distances between the masses and the elements change, their electrical capacitance alters, revealing their position.

Gyroscopes are based on the same tech but add an extra element. A spinning gyroscope will keep the same orientation even when it’s moved. That’s not practical on small MEMS, so they use a rapidly vibrating mass – which will also try to keep its orientation – instead.

It looks much the same as an accelerometer’s seismic mass, but measuring the vibrating mass’s position in relation to the sensing elements on the MEMS shows how the unit is turning rather than accelerating.

A six-axis IMU features multiple MEMS units and measures acceleration in three planes – left-right, up-down and forwards-backwards – and rotation in three directions; pitch, roll and yaw. A five-axis IMU misses out the yaw readings as they’re not essential for cornering ABS or TC.

All this technology is squeezed into a tiny, relatively inexpensive unit. Ducati are already fitting cornering ABS to all their bikes, and it’s easy to see that in few years’ time MEMS tech will be used on every bike right down to the cheapest scooters.

Technology explored

A MEMS system compared with a human hair

  • How small? That big brown thing is a human hair, so it’s easy to see how you can fit several MEMS into an IMU that will fit in your bike
  • Vacuum packed In a complete MEMS all this is sealed in a vacuum so air resistance can’t affect the mass’s movement
  • Interlaced combs The comb-shaped structures are the seismic masses, mounted on microscopic springs
  • Tiny package A Bosch MM5.10 IMU is packed with MEMS tech yet measures 80mm x 56mm x 21mm and weighs just 35g

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Ben Purvis

By Ben Purvis