Apparatus and method for estimating maximum road friction coefficient

A method for determining a maximum friction coefficient between a tire of a wheel and a road, comprising the steps of:

• calculating a reaction force of the road to the tire of the wheel based on a tire model;
• calculating a vertical load of the tire of the wheel;
• calculating as a first ratio a ratio of the reaction force of the road to the vertical load;
• calculating as a second ratio a ratio of variation in the reaction force of the road to variation in a slip ratio of the tire, the slip ratio being calculated based on the tire model;
• and
• calculating a maximum road friction coefficient based on a product of a predetermined coefficient and the second ratio, and the first ratio.

A controller for determining a maximum friction coefficient between a tire of a wheel and a road, comprising:

• a first section that calculates a reaction force of the road to the tire;
• a second section that calculates a vertical load of the tire;
• a third section that calculates variation in a slip ratio of the tire;
• a fourth section that calculates variation in the reaction force of the road to the tire;
• and
• a fifth section that calculates a maximum road friction coefficient based on the reaction force of the road, the vertical load, the variation in the slip ratio, and the variation in the reaction force of the road.