The invention discloses a
velocity estimation and friction identification method of a four-wheel turning / driving vehicle. The
velocity estimation and friction identification method comprises the steps that firstly, a vehicle body coordinate
system O-XY is established; secondly, a vehicle kinetic equation is established; thirdly, a wheel kinetic equation is established; fourthly, a wheel
velocity equation is established; fifthly, a wheel
slip rate equation is established; sixthly, the longitudinal force and lateral force of a wheel are obtained; seventhly, a friction model is parameterized; eighthly, a kinematical equation describing the relation of the vehicle velocity, the
yaw velocity and the acceleration is established; ninthly, an observer is designed under the situation that detectable signals z comprise the longitudinal acceleration ax, the lateral acceleration ay, the
yaw velocity r, the wheel
angular velocity wj and the
steering wheel rotation angle
delta i; tenthly, persistent excitation conditions are defined. According to the
velocity estimation and friction identification method, the nonlinearity self-
adaptation observer for estimating the vehicle longitudinal velocity and the
lateral velocity is established, the tire
road surface friction parameters are established in real time according to the change of
road surface conditions, and the velocity is estimated more accurately.