The solution to stopping on icy roads lies first in the vehicle detecting a dangerous situation. Like ABS and other state-of-the-art safety systems, the ICE starts by monitoring the wheel speeds. A controller continually monitors wheel speed sensors looking for a wheel lock up (panic stop) situation. That discovered, it now consults with an accelerometer (button sized electronic device) to determine the rate of negative acceleration. A decision is made relative to a pre-determined threshold and a response signal sent out within a few milliseconds.
The weak link when stopping on a slippery road is under the tires. The solution must take place under those same tires. The abrasive solves slippery conditions. Abrasive pinned under the tire scratches the surface of the ice to raise the coefficient of friction.
Unfortunately we can’t just drop sand in front of the tire. The vertical speed of the abrasive due to the acceleration of gravity is much slower than the horizontal speed of the car at even moderate speeds. The slipstream air will propel the abrasive backwards relative to the vehicle, so that it hits the tire, scatters and is lost before getting to the road.
The delivery solution lies in the capture of a segment of the slipstream air in a small air duct. An elbow is added to turn that stream of air from horizontal to vertical. This creates a unique pneumatic conveying system that is always in place with no moving parts. The unique aerodynamic design delivers the abrasive to the road surface just in front of the tire at any speed.
The Valve Solution
A valve at the elbow of the slipstream air duct controls the abrasive. The valve design accomplishes a number of key objectives:
- It operates smoothly with just one moving part.
- Upon opening, it instantly places the abrasive in the pneumatic air stream.
- It responds very quickly to the controller signal.
- It’s simple and inexpensive.
- It precludes freeze up and thus performs in icy conditions when needed most.
- It positively excludes moisture from the sand reservoir.
- In conjunction with the controller, it meters the proper rate of abrasive for the road speed.
Integrating Antilock Brakes
The pulse of the ABS system allows the tire to roll onto the abrasive path laid down by the ICE. When the wheel again locks up the abrasive is pinned under the tire to give dramatic improvement in control and stopping. Thus ABS is a key component to this technology.
How the ICE Works
- When the brakes are applied on an icy road, the controller compares the expected deceleration with the actual deceleration using data from the accelerometer.
- The controller recognizes a lack of deceleration and sends a signal to the mechanical device.
- The solenoid snaps open the valve.
- Abrasive falls by gravity from the small hopper into the pneumatic air stream.
- The air stream accelerates and propels the abrasive towards the road/tire interface.
- As the tire rolls onto this path of abrasive, the ABS pulses and pins the abrasive under the tire.
- As the vehicle slows, the valve automatically reduces the abrasive flow appropriate for the road speed.
The total elapsed time from when the wheels locked up until sand begins to land on the road is four tenths of a second. The coefficient of friction is thus raised from .08 to nearly .2. The stopping distance and turning radius are both cut in half.