Dariusz Pazderski

Practical Stabilization of a Skid-steering Mobile Robot - A Kinematic-based Approach

This paper presents kinematic control problem of skid-steering mobile robot using practical smooth and time-varying stabilizer. The stability result is proved using Lyapunov analysis and takes into account both input signal saturation and uncertainty of kinematics. In order to ensure stable motion of the robot the condition of permissible velocities is formulated according to dynamic model and wheel-surface interaction. Theoretical considerations are illustrated by simulation results

Trajectory tracking of underactuated skid-steering robot

This paper considers problem of approximation of admissible trajectory for skid-steering mobile robot at kinematic level. Nonholonomic constraints at kinematic and dynamic level are taken into account. The trajectory tracking control problem is solved using practical stabilizer using tunable oscillator with novel method of tuning. The stability result is proved using Lyapunov analysis and takes into account uncertainty of kinematics. In order to ensure stable motion of the robot the scaling method is used. Theoretical considerations are illustrated by simulation results.

Trajectory tracking for a mobile robot with skid-slip compensation in the vector-field-orientation control system

Trajectory tracking for a mobile robot with skid-slip compensation in the vector-field-orientation control system The article is devoted to a motion control problem for a differentially driven mobile robot in the task of trajectory tracking in the presence of skid-slip effects. The kinematic control concept presented in the paper is the Vector Field Orientation (VFO) feedback approach with a nonlinear feed-forward skid-slip influence compensation scheme. The VFO control law guarantees asymptotic convergence of the position tracking error to zero in spite of the disturbing influence of skid-slip phenomena. The paper includes a control law design description, stability and convergence analysis of a closed-loop system, and practical verification of the proposed control concept. The experimental results illustrate control quality obtained on a laboratory setup equipped with vision feedback, where the Kalman filter algorithm was used in order to practically estimate skid-slip components.

A Comparison Study of Discontinuous Control Algorithms for a Three-Link Nonholonomic Manipulator

The paper is focused on selected discontinuous methods which are adapted to control of a three-link nonholonomic manipulator equipped with ball gears. The considered control solutions defined at the kinematic level are based on discontinuous transformations using the so-called sigma process or polar representation. In order to improve robustness to measurement noise a hybrid technique is introduced. The comparison of the algorithms is based on simulation results and takes into account their robustness to measurement errors, convergence rate as well as control effort.

Motion Control of Vehicles with Trailers Using Transverse Function Approach

This paper is focused on analysis of the control solution using the transverse function approach. The controller considered here is designed for a nonholonomic vehicle with on-axle passive trailers. The main problem investigated is the optimal parametrization of the transverse functions in order to ensure low sensitivity to the measurement noise and high tracking accuracy. Theoretical analysis referring to transverse function scaling using dilation is illustrated by results of extensive numerical simulations. Taking into account these results the controller properties are considered. Finally, possibility of the controller implementation is discussed.

Vector-Field-Orientation Tracking Control for a Mobile Vehicle Disturbed by the Skid-Slip Phenomena

The paper is devoted to the trajectory tracking control task for a differentially-driven vehicle moving on a plane surface under conditions of the persistent skid-slip phenomena. The Vector Field(s) Orientation (VFO) control strategy, presented originally for undisturbed case in Michałek and Kozłowski (IEEE Trans Control Syst Technol 18(1):45–65, 2010), has been reformulated here to the new disturbed motion conditions. The extension of the VFO strategy relies on introduction of the nonlinear skid-slip influence compensator in the feed-forward loop, which in practical implementation involves the real-time estimation of the skid-slip velocities and their time-derivatives. The approach considers the skid-slip effects solely on the kinematic level avoiding the need of modeling a complicated phenomenon of the wheels-ground interaction. Theoretical analysis shows the asymptotic tracking ability for the position trajectory with boundedness of the orientation error. Experimental results included in the paper reveal substantial tracking quality improvement resulting from the utilization of the proposed skid-slip influence compensator.

Trajectory tracking control of Skid-Steering Robot – experimental validation

Abstract In this paper authors consider the problem of practical stabilization of wheeled mobile robot equipped with skid-steering drive (also know as SSMR). The kinematic model of SSMR is approximated by kinematics of unicycle including small perturbation term which describes limited skidding effect. It is justified that SSMR can be regarded as a system with non-stationary first order nonholonomic constraint. Based on this result smooth control scheme robust to limited skidding is developed. The control law ensures practical stabilization in regulation and trajectory tracking case, i.e. position and orientation errors are bounded to the assumed but nonzero values. The effectiveness of control solution is justified and illustrated by experimental results.

Experimental verification of SMC with moving switching lines applied to hoisting crane vertical motion control

In this paper we propose sliding mode control strategies for the point-to-point motion control of a hoisting crane. The strategies employ time-varying switching lines (characterized by a constant angle of inclination) which move either with a constant deceleration or a constant velocity to the origin of the error state space. An appropriate design of these switching lines results in non-oscillatory convergence of the regulation error in the closed-loop system. Parameters of the lines are selected optimally in the sense of two criteria, i.e. integral absolute error (IAE) and integral of the time multiplied by the absolute error (ITAE). Furthermore, the velocity and acceleration constraints are explicitly taken into account in the optimization process. Theoretical considerations are verified by experimental tests conducted on a laboratory scale hoisting crane.

Practical stabilization of two-wheel mobile robot with velocity limitations using time-varying control law

This paper presents a new time-varying kinematic algorithm ensuring practical stabilization for the regulation and trajectory tracking (for both admissible and non-admissible trajectories) problem applied to control of two-wheel mobile robot. This proposition is based on work done by W. Dixon et al. (2003) and P. Morin and C. Samson (2003). The significant part of the paper concentrates on choosing suitable accuracy of tracking in order to limit frequency of control signal and to improve quality of transient stage. Theoretical results are verified for regulation problem by extensive experimental work using real mobile robot and vision localization system with respect to the different values of input saturation.

Posture Stabilization of a Unicycle Mobile Robot — Two Control Approaches

State feedback control issues for nonholonomic systems are still very challenging for control researchers. Among the group of nonholonomic systems one can number wheeled mobile vehicles, manipulators with nonholonomic gears, free-floating robots, underwater vessels, nonholonomic manipulator’s grippers, dynamically balanced hopping robots and others [4, 10, 15]. Difficulties in designing effective stabilizers arise from nonintegrable kinematic constraints imposed on system evolution. These constraints impose restriction on admissible velocities of controlled dynamic systems, preserving however their controllability. Moreover, lower dimensionality of the control space U ⊂ ℝm in comparison to the configuration space Q ⊂ ℝn (n > m) causes difficulties in control design, especially for stabilization task problems [5]. Despite the problems mentioned, many different feedback control strategies for nonholonomic kinematics in automatics and robotics literature have been proposed - see for example [7], [18] or [8]. Still, some important problems, like robustness to control signals limitations existance, intuitive contoller parameter tunning and good control quality during transient stage seem to remain open issues and involve further research. In this paper two different stabilization approaches to the mentioned problems, with alternative solution in comparison to existing strategies, are described. The presented approaches are applied to derive two stabilizers to solve the stabilization task for a unicycle mobile robot, taking into account control limitations.