The paper introduces a novel general feedback control framework, which allows applying the motion controllers originally dedicated for the unicycle model to the motion task realization for the car-like kinematics. The concept is formulated for two practically meaningful motorizations: with a front-wheel driven and with a rear-wheel driven. All the three possible steering angle domains for carlike robots-limited and unlimited ones-are treated. Description of the method is complemented by the formal stability analysis of the closed-loop error dynamics. The effectiveness of the method and its limitations have been illustrated by numerous simulations conducted for the three main control tasks, namely, for trajectory tracking, path following, and set-point regulation.
In this article the cascaded set-point feedback controller has been proposed for kinematics of the articulated mobile vehicle equipped with arbitrary number of off-axle hitched trailers. The concept results from geometrical features of the vehicle model, and from application of the Vector-Field-Orientation method in the outer loop of the cascaded controller. Solution presented in this article is formulated in the original configuration space of the vehicle not involving any auxiliary state or input transformation. It guarantees convergence of the last vehicle segment to the prescribed neighbourhood of a desired posture along with approximate straightening of a vehicle kinematic chain during approaching the destination. Practical limits of the control input amplitudes have been taken into account during the control law derivation by the application of a simple on-line scaling procedure to the nominally computed control functions. Results of numerical simulations illustrate effectiveness of the method for a 3-trailer vehicle.
A general trajectory-tracking control solution is proposed for truly N-trailer robots comprising a unicycle-like tractor and arbitrary number of passive trailers interconnected by sign-homogeneous nonzero hitching offsets. The solution permits either backward or forward motion strategy of a vehicle, preserving location of a guidance point on the last trailer. The presented control law is modular and highly scalable with respect to a number of trailers thanks to employing a cascade-like control structure. Stability and robustness analysis of the closed-loop system provides sufficient conditions for asymptotic and practical tracking for a wide set of the so-called segment-platooning reference trajectories containing both constant-curvature and varying-curvature motion profiles. Efficiency of the controller and its robustness to parametric uncertainty have been illustrated by experimental results obtained for a three-trailer vehicle.
TheVector-Field-Orientation (VFO) method is a control design concept which was originally introduced for the unicycle kinematics to solve two classical control tasks corresponding to the trajectory tracking and set-point control problems. A unified solution to both the tasks was possible by appropriate definitions of the so-called convergence vector field. So far, there has not been a version of the VFO control law for the third classical control task concerning the path following problem, which is particularly meaningful in the context of practical applications. The paper fills this gap by presenting a novel VFO path following controller devised for robots of unicycle-like kinematics with the amplitudelimited control input. Opposite to most path following controllers proposed in the literature, the new control law utilizes the recently introduced level curve approach which does not employ any parametrization of a reference path. In this way, the proposed solution
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