Kammova circle adhesion

Good driving stability and maneuverability of the vehicle in critical situations is the main prerequisite for sufficient active vehicle safety. The basic requirement is the same time grip on the road, or adhesion. Bonding conditions can be easily visualized using the Kammovy adhesion (friction) circle.

Directional stability is determined by the wheel circumferential forces, you are limited to road tire adhesion - adhesion. Maximum size of the adhesion force depends on the value of the product of the normal forces of adhesion and coefficient of f. Operates in the tire circumferential track forces (driving or braking) and power side at the same time, their sizes are geometrically cumulative.

1 - a driving force, 2 - the braking force (counteracting the driving force), 3 - guiding force (lateral force), 4 - weight
forces in the tire tracks

To illustrate the instantaneous adhesion properties can be used so-called Kammova circle whose diameter is proportional to the tire grip the road (the better the adhesion, the larger the diameter of a circle). To prevent loss of adhesion between tire and road, not the resultant of the longitudinal and lateral forces exceed the radius R friction circle. In reality, however, have tires more grip in the longitudinal direction, so the actual Kammova circle is rather elliptical shape.

1 - tire 2 - Kammova circle

If the braking force B equal to the maximum transmitted power of R, then it must be under the upper lateral force image with zero. In this case, round zero lateral line. If the braking force B even larger than the maximum possible braking force B _MAX, then there is a wheel lock and the tire gets into a skid. If the steering axle wheels without lateral shear line, the vehicle becomes uncontrollable!