A method is provided capable of improving the accuracy of estimations of quantities
that represent the state of a vehicle, such as vehicle speed, wheel slip ratio,
wheel speed along the ground, longitudinal wheel force and the vehicle body sideslip
angle, or values related to the quantities that represent the vehicle state, using
a simple and inexpensive method. A tire longitudinal force computing unit 81
calculates longitudinal forces F1 to F4 of each of the
wheels by substituting a coefficient of friction , which is adjusted such
that a deviation between a detected value of a longitudinal acceleration Gx
and an estimated longitudinal acceleration Gxe is zero, an estimated
vehicle speed Ve, slip ratios S1 to S4 of each
of the wheels calculated based on detected values of sensors 11 and 31,
loads W1 to W4 of each of the wheels, calculated based on
detected values of sensors 12 and 61, and lateral forces Y1
to Y4, into an equation related to a predetermined tire dynamics
model. A longitudinal acceleration estimating unit 82 calculates an estimated
longitudinal acceleration Gxe based on the longitudinal forces F1
to F4 and a predetermined movement equation. An integrator 43
integrates with respect to time the estimated longitudinal acceleration Gxe,
and calculates an estimated vehicle speed Ve.
