Measuring wheel forces and wheel speed on snow and ice to see when a tire slips

Why vehicles are tested on snow

Snow and ice make the road slippery, and a vehicle has to stay safe to drive on them. Manufacturers test and validate their designs on snow and ice before the vehicle reaches the road, and much of this testing is done with wheel force transducers.

Low grip, water and cold at the wheel

The measurement is made at the wheel, the part most exposed to snow, ice and water. The transducer output has to stay stable there, in the cold and in the wet.

Michigan Scientific wheel force transducers are made of stainless steel, sealed to IP67 and temperature compensated. The telemetry version for cars and light duty trucks, the LW12.8-50-TEL, operates from −40 to 125 °C and needs no cable through the hub.

A sealed transducer with a wireless link

The setup is the same as for any wheel force measurement. The transducer takes the place of the wheel center, the signals leave the wheel, and an interface box gives the loads in vehicle axes.

1. 01

   Mount the transducer on the wheel

   It mounts between a rim adapter and a hub adapter made for the vehicle, and measures three forces and three moments.

   LW series wheel force transducers
2. 02

   Send the signals by telemetry

   A wireless transmitter in the wheel package sends the signals. No cable goes through the hub.

3. 03

   Resolve the loads in the interface box

   The CT2 box does the coordinate transformation and the crosstalk compensation in real time, with analog, CAN and Ethernet outputs.

4. 04

   Add the side slip angle if needed

   An optical sensor on a wheel or on the body gives the side slip angle. It works on dry, wet and dry icy roads.

   TrueSlip side slip sensor

How slip shows in the data: speed up, force down

The transducer records the forces on the wheel and the wheel speed together. When the tire starts to slip because the coefficient of friction is low, the data shows an increase in wheel speed together with a decrease in the force on the wheel.

The same signature appears on ice, on snow and even on sand. It marks the moment the tire slips excessively, which is the information needed to judge how the vehicle handles on that surface.

The same data serves tire development

Forces and moments measured at the wheel on the real surface are used in tire testing and validation. They show how the tire interacts with the vehicle and with the surface, and how that affects the handling the driver feels.

Frequent questions