Method and apparatus for judging road surface conditions, and program for setting threshold for judging road surface conditions

An apparatus for judging road surface conditions, comprising:

• a rotational information detecting means for periodically detecting rotational information of tires of four wheels of a vehicle;
• a rotational information storing means for storing the rotational information of the respective tires;
• a vehicle velocity calculating means for calculating a vehicle velocity from the rotational information;
• an acceleration/deceleration calculating means for calculating an acceleration/deceleration of the vehicle;
• a slip ratio calculating means for calculating a slip ratio of left-sided front and rear wheels and right-sided front and rear wheels and a slip ratio of front and rear wheels, respectively;
• a fluctuation amount calculating means for calculating an amount of fluctuation in differences between the right and left slip ratios;
• a coefficient calculating means for obtaining a linear regression coefficient and a correlation coefficient between the slip ratio of the front and rear wheels and the acceleration/deceleration of the vehicle;
• and a threshold setting means for setting a threshold for judging road surface conditions on the basis of the linear regression coefficient if the amount of fluctuation is a specified value.

A program for setting a threshold for judging road surface conditions, wherein a computer is made to function as a rotational information storing means for storing rotational information of respective tires;

• a vehicle velocity calculating means for calculating a vehicle velocity from the rotational information;
• an acceleration/deceleration calculating means for calculating an acceleration/deceleration of the vehicle;
• a slip ratio calculating means for calculating a slip ratio of left-sided front and rear wheels and right-sided front and rear wheels and a slip ratio of front and rear wheels, respectively;
• a fluctuation amount calculating means for calculating an amount of fluctuation in differences between right and left slip rates;
• a coefficient calculating means for obtaining a linear regression coefficient and a correlation coefficient between the slip ratio of the front and rear wheels and the acceleration/deceleration of the vehicle;
• and a threshold setting means for setting a threshold for judging road surface conditions on the basis of the linear regression coefficient if the amount of fluctuation is a specified value.