Vehicle state variable estimator of host vehicle and rack target position determiner for rear wheel steering system using the same

A device for estimating a vehicle state variable to determine a rack target position of a rear wheel steering system of a host vehicle, the device comprising:

• a first sensor configured to detect a first yaw rate of the host vehicle;
• a second sensor configured to detect a velocity of the host vehicle;
• and
• a controller connected to the first sensor and the second sensor, and configured to estimate the vehicle state variable,
• wherein the controller is further configured to:
• estimate a second yaw rate of the host vehicle;
• calculate a first gain for correcting a difference between the first yaw rate and the second yaw rate;
• calculate an interpolation ratio that changes with the velocity;
• calculate a second gain by applying the interpolation ratio to the first gain;
• and
• estimate the vehicle state variable based on the second gain.