Patent ID: 6952635

Claim:
An apparatus for estimating a road condition for use in a vehicle having steering control means for actuating a device mechanically independent of a manually operated steering member to steer at least a wheel of front and rear wheels of said vehicle, comprising: actuating signal detection means for detecting an actuating signal for-actuating said device of said steering control means; aligning torque estimation means for estimating an aligning torque produced on said wheel on the basis of the actuating signal detected by said actuating signal detection means; vehicle state variable detection means for detecting a state variable of said vehicle; wheel factor estimation means for estimating at least one of wheel factors including a side force and a slip angle applied to said wheel on the basis of the state variable detected by said vehicle state variable detection means; and grip factor estimation means for estimating a grip factor of at least a tire of said wheel, in accordance with a relationship between the aligning torque estimated by said aligning torque estimation means and the wheel factor estimated by said wheel factor estimation means.