Trajectory tracking control of a four-wheel-steering car based on differential flatness and ADRC

A flatness based robust active disturbance rejection control technique is proposed for the trajectory tracking problem of a special under-actuated system known as four-wheel-steering car. The under-actuated problem of such nonlinear coupled system consisting of three degrees of freedom is settled by exploiting its flatness property to obtain an input-output map. Active disturbance rejection control (ADRC), which shows many advantages in estimating and compensating the lumped effects is then utilized. Several simulations are carried out to show the improvements in vehicle handling and stability of the flat based high-order linear ADRC scheme.