Wheel grip factor estimating apparatus and vehicle motion control apparatus

A vehicle motion control apparatus comprising:

• a steering factor detecting unit that detects at least one of steering factors including a steering torque and steering effort applied on a steering system extending from a steering wheel to a suspension in a vehicle;
• a longitudinal force estimating unit that estimates a driving or braking force of the wheel;
• a self-aligning torque estimating unit that estimates self-aligning torque generated in the wheel on the basis of the steering factor detected by the steering factor detecting unit, estimates a quantity of influence of the driving or braking force estimated by the longitudinal force estimating unit on the self-aligning torque, and estimates a value obtained by removing the quantity of influence from the self-aligning torque as new self-aligning torque;
• a vehicle state variable detecting unit that detects a state variable of the vehicle;
• a wheel factor estimating unit that estimates at least one of wheel factors including side force and slip angle applied on the wheel on the basis of the state variable detected by the vehicle state variable detecting unit;
• a grip factor estimating unit that estimates a grip factor of the wheel on the basis of change of the self-aligning torque newly estimated by the self-aligning torque estimating unit relative to the wheel factor estimated by the wheel factor estimating unit;
• and
• a control unit that controls at least one of braking force, engine output and gear shift position of the vehicle to reduce a speed of the vehicle when the grip factor estimated by the grip factor estimating unit is lower than a predetermined value.