We propose a simple control design allowing a mobile robot equipped with a camera to track a line on the ground. The control algorithm, as well as the image-processing algorithm, are very simple. We discuss the existence and the practical stability of an equilibrium trajectory of the robot when tracking a circular reference line. We then give a complementary analysis for arbitrary reference lines with bounded curvature. Experimental results confirm the theoretical analysis.

Realistic wheeled mobile robots do not satisfy the ideal kinematic constraints because of slipping effects at the wheel/ground contact zones, The slow manifold approach allows us to design feedback control laws taking into account these dynamics and ensuring the tracking error of the closed-loop system to converge toward zero.

This paper is devoted to the dynamic analysis of real redundant mobile robots, for which, two types of constraints characterizing ideal redundant robots, are not satisfied: kinematic constraints related to the contact conditions between the wheels and the ground, and the geometric constraints related to the coordination of the wheel orientation angles. In order to assure a good trajectory tracking, an output feedback linearizing control law is derived and illustrated by simulation results.

This paper is devoted to the kinematic analysis of mobile robots equipped with centred orientating wheels. The problems of mobility and directionality are addressed and it is shown that such robots are omnidirectional. A state space formulation is proposed allowing it to describe the robot motion, even in the neighbourhood of singular configurations.

Typical mobile robot structures (e.g. wheelchair or car-like) do not have the required mobility for common applications such as displacement in a corridor, hospital and office. New structures based on the "universal wheel" (i.e. a wheel equipped with free rotating rollers) have been developed to increase mobility. However these structures have important drawbacks such as vertical vibration and limited load capacity. This paper presents a comparison of several types of universal wheel performances based on the three following criteria: load capacity, surmountable bumps and vertical vibration. It is hoped that this comparison will help the designer in the selection of the best suitable solution for his/her application.

The structure of the kinematic and dynamic models of wheeled mobile robots is analyzed. It is shown that, for a large class of possible configurations, they can be classified into five types, characterized by generic structures of the model equations. For each type of model the following questions are addressed: (ir)reducibility and (non)holonomy, mobility and controllability, configuration of the motorization, and feedback equivalence.

A hybrid strategy for the control of nonholonomic mobile robots is proposed and assessed, using both theoretical arguments and simulation experiments. The control law is a discontinuous state feedback that combines the advantages of time-invariant smooth feedback control far from the target and of time-varying smooth feedback control close to the target, while avoiding their respective drawbacks.>

Smooth time-varying laws can solve the stabilization problem of nonholonomic mechanical systems. The authors show that by means of dynamic state feedback, it is possible for three-wheeled mobile robots to track arbitrary fast trajectories not reduced to equilibrium points. Dynamical modeling of nonholonomic mechanical systems for the case of three-wheeled mobile robots is considered. Dynamic feedback allows solution of the tracking problem for an omnidirectional mobile robot with less motors than degrees of freedom. This is possible by choosing output functions depending on the mass repartition of the robot.>

An original procedure for the estimation of the barycentric parameters of a robot is presented. This procedure requires only the processing of measurements provided by an external experimental set-up (reactions at the bedplate, and position, velocities, and accelerations). The procedure is based on the property that the relations between the robot motion and its reactions on its bedplate are completely independent of the internal joint forces. Some identifiability issues are discussed, and a validation experiment is reported.>

A general dynamical model is derived for three-wheel mobile robots with nonholonomic constraints by using a Lagrange formulation and differential geometry. It is shown that a static state feedback allows one to reduce the dynamics of the system to a form in which stabilizing input-output linearizing control is possible.>