Discussion on: 'Trajectory Tracking for a Wheeled Mobile Robot Using a Vision Based Positioning System and an Attitude Observer'

摘要

The authors of the paper consider a tracking problem for a wheeled mobile robot assuming the possibility of measuring its Cartesian coordinates. These coordinates arc fed to a dynamic full information controller together with the orientation of the robot which is estimated through an attitude observer. Theoretical convergence results are proved (under the assumption of perfect measurements) and experimental tests are given in the paper to illustrate the effectiveness of the proposed approach. The observer defined in Proposition 1 belongs to the class of the Immersion and Invariance (I&I) observers [ 1 ], [2] and has been designed to obtain asymptotic convergence of the robot angle Ø (the estimated quantities are (cos(Ø), sin(Ø))) as stated in Proposition 1, where it is assumed that the robot longitudinal velocity u_1(t) is such that there exist a set T = {tk ∈ R ≥ 0 : u_1 (tk) = 0} that is either finite or infinite but countable. Note this assumption implies that the convergence of the estimation error ε(t) is nonuniform.