Luca Baglivo

Autonomous pallet localization and picking for industrial forklifts: a robust range and look method

A combined double-sensor architecture, laser and camera, and a new algorithm named RLPF are presented as a solution to the problem of identifying and localizing a pallet, the position and angle of which are a priori known with large uncertainty. Solving this task for autonomous robot forklifts is of great value for logistics industry. The state-of-the-art is described to show how our approach overcomes the limitations of using either laser ranging or vision. An extensive experimental campaign and uncertainty analysis are presented. For the docking task, new dynamic nonlinear path planning which takes into account vehicle dynamics is proposed.

A Unified Framework for Uncertainty, Compatibility Analysis, and Data Fusion for Multi-Stereo 3-D Shape Estimation

This paper describes the uncertainty analysis performed for the reconstruction of a 3-D shape. Multiple stereo systems are employed to measure a 3-D surface with superimposed colored markers. The procedure comprised a detailed uncertainty analysis of all measurement phases, and the uncertainties evaluated were employed to perform a compatibility analysis of points acquired by different stereo pairs. The compatible acquired markers were statistically merged in order to obtain the measurement of a 3-D shape and an evaluation of the associated uncertainty. Both the compatibility analysis and the measurement merging are based on the evaluated uncertainty.

Uncertainty Evaluation in Two-Dimensional Indirect Measurement by Evidence and Probability Theories

An improved method for 2-D uncertainty expression and propagation based on the theory of evidence and 2-D random-fuzzy variables (RFVs) is described. A previous 2-D RFV approach and two probability-based approaches are also introduced. The improved RFV approach exploits a new algorithm for the combination of random and systematic effects, trying to overcome a drawback of a 2-D RFV method already disclosed in a previous work. One of the two probability-based methods does not take into account any correlation among uncertainty sources and among different time instants of each source, whereas the other probability method exploits time correlation to take into account the repetitive nature of systematic uncertainty sources. All described methods are applied to the 2-D case of a vehicle position measurement on a plane. The obtained results are compared and show the compatibility of all approaches. The improved random-fuzzy method yields better uncertainty evaluation in case of narrow and elongated confidence regions than the previous method. The new 2-D RFV approach also exhibits a better behavior from a theoretical point of view. Main differences between the two probability-based methods are also presented.

Measurement of momentum transfer due to adhesive forces: On-ground testing of in-space body injection into geodesic motion

In the frame of many scientific space missions, a massive free-falling object is required to mark a geodesic trajectory, i.e., to follow inside a spacecraft an orbit that is determined only by the planetary gravity field. The achievement of high-purity geodesic trajectories sets tight design constraints on the reference sensor that hosts and controls the reference body. Among these, a mechanism may be required to cage the reference body during the spacecraft launch and to inject it into the geodesic trajectory once on-orbit. The separation of the body from the injection mechanism must be realized against the action of adhesion forces, and in the worst case this is performed dynamically, relying on the bodys inertia through a quick retraction of the holding finger(s). Unfortunately, this manoeuvre may not avoid transferring some momentum to the body, which may affect or even jeopardize the subsequent spacecraft control if the residual velocity is too large. The transferred momentum measurement facility (TMMF) was developed to reproduce representative conditions of the in-flight dynamic injection and to measure the transferred momentum to the released test mass. In this paper, we describe the design and development of the TMMF together with the achieved measurement performance.

Four path following controllers for rhombic like vehicles

This paper addresses the path following problem of a wheeled mobile robot with rhombic like kinematics (two drivable and steerable wheels) operating in cluttered environments. Four path following controllers are developed to steer the kinematic model of a rhombic like vehicle (RLV) along a desired path: three are based on feedback laws derived at a kinematic level with geometrical inspiration; the fourth is a nonlinear controller built upon a kinematic model of the vehicle using Lyapunov functions. By fully exploiting the kinematic capabilities of this type of vehicles, all the developed controllers are capable of performing under two situations: when both wheels follow the same path, or when each wheel follows a different path. Simulated and experimental results are presented in the paper to illustrate the performance of the controllers. The main conclusions of these controllers are summarized, leading to a possible application in the vehicles that will operate in the remote handling missions of the International Thermonuclear Experimental Reactor (ITER).

Uncertainty analysis for multi-stereo 3d shape estimation

It is described the uncertainty analysis performed for the reconstruction of a 3D shape. Multiple stereo systems are employed to measure a 3D surface with superimposed colored markers. The described procedure comprises a detailed uncertainty analysis of all the measurement phases, and the evaluated uncertainties are employed to perform a compatibility analysis of points acquired by different stereo pairs. The compatible acquired markers are statistically merged in order to obtain a measurement of a 3D shape and an evaluation of the associated uncertainty. Both the compatibility analysis and the measurement merging is based on the evaluated uncertainty.

Real-Time Uncertainty Estimation of Autonomous Guided Vehicle Trajectory Taking Into Account Correlated and Uncorrelated Effects

This paper presents the description of a novel uncertainty estimation method employed for the navigation of autonomous guided vehicles. In the proposed algorithm, the uncertainty of the odometric navigation system is estimated as a function of the actual maneuver being carried out, which is identified by navigation data themselves. The result is a recursive method for estimating the evolution of spatial uncertainty, which takes into account unknown systematic effects and uncorrelated effects due to kinematic model uncertainty. The method is explained starting from the measurement models and its parameters as a function of the actual maneuvers. A verification of covariance propagation estimate due to systematic effects was carried out by means of a Monte Carlo simulation method. Experimental verification was carried out using an autonomous vehicle. Compatibility between a reference environment-referred system and the uncertainty estimated by the proposed method was achieved in 95% of the trials

A method for asteroids 3D surface reconstruction from close approach distances

We present a procedure for asteroids 3D surface reconstruction from images for close approach distances. Different from other 3D reconstruction scenario from spacecraft images, the closer flyby gave the chance to revolve around the asteroid shape and thus acquiring images from different viewpoints with a higher baseline. The chance to have more information of the asteroids surface is however paid by the loss of correspondences between images given the larger baseline. In this paper we present a procedure used to reconstruct the 3D surface of the asteroid 21 Lutetia encountered by Rosetta spacecraft on July the 10th of 2010 at the closest approach distance of 3170 Km. It was possible to reconstruct a wider surface even dealing with strong ratio of missing data in the measurements. Results show the reconstructed 3D surface of the asteroid as a sparse 3D mesh.

Description and application of a new method for uncertainty evaluation in two-dimensional indirect measurement

It is described an improved method for two-dimensional uncertainty expression and propagation based on the theory of evidence, employing 2D random-fuzzy variables (RFVs) as the main tool. The improved approach exploits a new algorithm for the combination of random and systematic effects, trying to overcome a drawback of a 2D RFV method already disclosed in a previous work. Uncertainty evaluation in multi dimensional measurements is usually carried out using a probabilistic approach which relies on Monte Carlo simulations or on the GUM formula with covariance matrices for propagation, while a random-fuzzy approach for multi dimensional applications is almost completely new. The described improved method is applied to the 2D case of vehicle position measurement on a plane. The obtained results are compared with those obtained by the probabilistic approach with Monte Carlo simulations and by the previous 2D RFV method already disclosed. The results show that the confidence regions obtained by all three approaches are compatible and that the improved random-fuzzy method yields a better uncertainty evaluation in case of narrow and elongated confidence regions than the previous one. The new 2D RFV approach exhibits a better behavior also from a theoretical point of view.

Reactive Simulation for Real-Time Obstacle Avoidance

This chapter provides a new approach to the dynamic path planning and obstacle avoidance in unknown and dynamic environments. The system is based on the interaction between four different modules: the Path Planner, the Graph which memorizes all the local target, the “Sentinel”, and the module which computes the Reactive Simulation every time an obstacle is detected along the path. The Reactive Simulation takes in account the kinematics model of the vehicle and the actual state conditions to make a real-time simulation in order to predict the trajectory of the differential drive robot that would allow the safe reaching of the local target.