Localizability of unicycle mobiles robots: an algebraic point of view.

International audienceA single landmark based localization algorithm for unicycle mobile robots was provided in [1]. It is based on the algebraic localizability notion and an efficient differentiation algorithm in noisy environment ([2], [3]). Let us stress that this localization algorithm do not need to know the linear and the angular velocities which are reconstructed by this algorithm using the kinematic model. In this paper, a sensibility study leads to a new fusion algorithm in the multi landmark case us- ing as a basis our posture differentiation based estimator. Some simulations and experimental results are presented in order to prove the effectiveness of the proposed method compared to the well known EKF method

A single landmark based localization algorithm for non-holonomic mobile robots

International audienceThis paper proposes a single landmark based localization algorithm for non-holonomic mobile robots. In the case of a unicycle robot model, the localization problem is equivalent to the system observability. Based on this observation, the proposed localization method consists in finding a vector function which depends on the measurement vector and its derivatives. In order to compute estimates of the successive derivatives of the measurement vector, we will use a numerical differentiation method. When the robot is able to only measure the relative angle between itself and the landmark in 2D case, the algorithm estimates the posture of the robot, under the hypothesis that control inputs are known. But, sometimes it is also useful to be able to estimate the control input (for example when the robot slips). This is possible with the proposed algorithm by using a landmark in dimension three. The simulation results will be given in order to show the effectiveness of the proposed algorithm. Moreover, these results are compared with those obtained by an Extended Kalman Filter in order to underline the advantages of the new algorithm

A New Three Object Triangulation Algorithm for Mobile Robot Positioning

Positioning is a fundamental issue in mobile robot applications. It can be achieved in many ways. Among them, triangulation based on angles measured with the help of beacons is a proven technique. Most of the many triangulation algorithms proposed so far have major limitations. For example, some of them need a particular beacon ordering, have blind spots, or only work within the triangle defined by the three beacons. More reliable methods exist; however, they have an increasing complexity or they require to handle certain spatial arrangements separately. In this paper, we present a simple and new three object triangulation algorithm, named ToTal, that natively works in the whole plane, and for any beacon ordering. We also provide a comprehensive comparison between many algorithms, and show that our algorithm is faster and simpler than comparable algorithms. In addition to its inherent efficiency, our algorithm provides a very useful and unique reliability measure, assessable anywhere in the plane, which can be used to identify pathological cases, or as a validation gate in Kalman filters.Peer reviewe

A Stable Nonlinear Switched System for Landmark-aided Motion Planning

To guarantee navigation accuracy, the robotic applications utilize landmarks. This paper proposes a novel nonlinear switched system for the fundamental motion planning problem in autonomous mobile robot navigation: the generation of continuous collision free paths to a goal configuration via numerous land marks (waypoints) in a cluttered environment. The proposed system leverages the Lyapunov based control scheme (LbCS) and constructs Lyapunov like functions for the system’s subsystems. These functions guide a planar point mass object, representing an autonomous robotic agent, towards its goal by utilizing artificial landmarks. Extracting a set of nonlinear, time invariant, continuous, and stabilizing switched velocity controllers from these Lyapunov like functions, the system invokes the controllers based on a switching rule, enabling hierarchical landmark navigation in complex environments. Using the well known stability criteria by Branicky for switched systems based on multiple Lyapunov functions, the stability of the proposed system is provided. A new method to extract action landmarks from multiple landmarks is also introduced. The control laws are then used to control the motion of a nonholonomic car like vehicle governed by its kinematic equations. Numerical examples with simulations illustrate the effectiveness of the Lyapunov based control laws. The proposed control laws can automate various processes where the transportation of goods or workers between different sections is required

Single landmark based self-localization of mobile robots

In this paper we discuss landmark based absolute localization of tiny autonomous mobile robots in a known environment. Landmark features are naturally occurring as it is not allowed to modify the environment with special navigational aids. These features are sparse in our application domain and are frequently occluded by other robots. This makes simultaneous acquisition of two or more landmarks difficult. Therefore, we propose a system that requires a single landmark feature. The algorithm is based on range measurement of a single landmark from two arbitrary points whose displacement can be measured using dead-reckoning sensors. Range estimation is done with a stereo vision system. Simulation results show that the robot can localize itself if it can estimates range of the same landmark from two different position and if the displacement between the two position is known. 1