Global output-feedback path-following control of unicycle-type mobile robots: A level curve approach

This paper proposes a design of global output-feedback path-following controllers for unicycle-type mobile robots based on the recently developed level curve approach. The controllers are designed based on Lyapunov's direct and backstepping methods to force the position of the robot to satisfy the equation of the path and to move along the path tangentially at a desired linear velocity. An interlaced observer, which is a reduced-order observer plus an interlaced term, is designed to estimate the robot unmeasured velocities and disturbances. The observer design is based on a coordinate transformation that transforms the robot dynamics to a new form, which does not contain velocity quadratic terms. The interlaced term is determined during the control design to void difficulties due to observer errors and unbounded reference path derivatives. Simulations are included to illustrate the effectiveness of the proposed concept.