Robustification of the modular tracking control system for non-Standard N-Trailers of uncertain kinematics

The paper is devoted to the problem of control performance robustification for the modular cascade-like tracking controller, recently devised for the N-Trailer vehicles equipped solely with off-axle hitching (called the non-Standard N-Trailers). It has been shown that the control performance degradation due to parametric uncertainty of the N-Trailer kinematics can be treated as an effect of an external input-matched disturbance acting on the closed-loop system dynamics. One proposes to suppress this detrimental effect by redesigning of the original cascade-like tracking controller combining it with an additional disturbance observation-compensation loop. It is revealed under which conditions the new robustified control law guarantees uniform ultimate boundedness of tracking errors for arbitrarily small ultimate bounds. Forecasts of a theoretical analysis have been validated by numerical examples and practically verified with a laboratory-scale three-trailer robotic vehicle. The results illustrate control performance improvement achievable with the new robust controller, even in the case of substantial parametric uncertainty of a vehicle model.