Giovanni Indiveri

Modeling and identification of open-frame variable configuration unmanned underwater vehicles

A lumped parameter model of open-frame unmanned underwater vehicles (UUVs) including the effects of propeller-hull and propeller-propeller interactions is presented. The identification of the model parameters consists of a least squares method using only on-board sensor data without requiring any towing tank tests. The identification scheme is based on separate tests for the estimation of drag and thruster installation coefficients, taking into account propeller-hull and propeller-propeller effects first and inertia parameters subsequently. The scheme has been experimentally implemented on ROMEO, the latest UUV developed by CNR-IAN. Experimental results show both the effectiveness of the proposed method and the relevance of the propeller-hull and propeller-propeller interactions that are usually neglected in standard UUV models.

Swedish Wheeled Omnidirectional Mobile Robots: Kinematics Analysis and Control

Swedish wheeled robots have received growing attention over the last few years. Their kinematic models have interesting properties in terms of mobility and possible singularities. This paper addresses the issue of kinematic modeling, singularity analysis, and motion control for a generic vehicle equipped with N Swedish wheels.

Nonlinear Time-Invariant Feedback Control of an Underactuated Marine Vehicle Along a Straight Course

Abstract A nonlinear, closed-loop, time-invariant controller that globally stabilizes an underactuated marine vehicle on a straight course is proposed- Traditional surface vessel linear course tracking autopilots are designed applying linear control methods on the linearized model, thus yielding only local results. Indeed due to the underactuated nature of the system, the model cannot be feedback linearized thus the most common and perhaps powerful tools of nonlinear control theory are ruled out and an alternative design strategy must be considered. At present no other smooth, time-invariant controller globally achieving the control objective is known to the authors. The overall convergence, stability and robustness to environmental disturbances is addressed and simulations are provided to show the controllers behaviour.

The Null-Space-based Behavioral Control for Mobile Robots with Velocity Actuator Saturations

In this paper we present the application of the Null-Space-based Behavioral (NSB) approach to the motion control of mobile robots with velocity saturated actuators. The NSB is a behavior-based robot control approach that uses a hierarchical organization of the tasks to guarantee that they are executed according to a desired priority: it uses a projection technique to avoid that, in the absence of actuator saturations, low-priority tasks could influence higher-priority tasks. The main contribution of this paper is the extension of the NSB approach to the case where actuator velocity saturation bounds are explicitly taken into account. The proposed solution dynamically scales task velocity commands so that the hierarchy of task priorities is preserved in spite of actuator velocity saturations. The approach has been validated on two specific case studies. In the first case, the NSB elaborates the motion directives for a single mobile robot that has to reach a target while avoiding a point obstacle1 in this case, the mission is composed of two tasks. In the second case, the NSB elaborates the motion directives for a team of six mobile robots that has orates the motion directives for a team of six mobile robots that has to entrap and escort a target1 in this case the mission is composed of four tasks. The approach is validated by numerical simulations and by experiments with real mobile robots.

High Speed Differential Drive Mobile Robot Path Following Control With Bounded Wheel Speed Commands

The great majority of path following control laws for either kinematical or dynamical mobile robot models are designed assuming ideal actuators, i.e. assuming that any commanded velocity or torque (in the kinematical and dynamical cases respectively) will be instantly implemented regardless of its value. Real actuators are far from being ideal. In particular, only bounded velocities and torques can be realized for any given command. With reference to the kinematical model of a differential drive mobile robot, a known path following control law is modified to account for actuator velocity saturation. The proposed solution is experimentally shown to be particularly useful for high speed applications where accounting for actuator velocity saturation may have a large influence on performance.

MARIS: A national project on marine robotics for interventions

The MARIS project arises as initiative of four Departments of Universities which are members of the Inter-University Centre ISME (“Integrated Systems for the Marine Environment”), legally represented by the University of Genoa, and the research unit of Genoa of CNR-ISSIA (”Institute for Studies on Intelligent Systems for Automation?) of the National Council of Research of Italy, with headquarter in Bari. The two institutions qualify for their long-term research experience in the application of ICT to the marine environment, with particular interests directed toward Underwater Robotics, intended in all its methodological, technological and applicative aspects. The initial research consortium has been then enriched by the inclusion of two additional University Departments, which have selected for the highly qualified contributions they can provide to the MARIS project. In this framework, the proposing institutions ISME and CNR-ISSIA have established, as general strategic objective of the project, the one of studying, developing and integrating, technologies and methodologies enabling the development of underwater robotized systems employable for manipulation and transportation activities; within underwater scenarios which are deemed progressively becoming typical for the off-shore industry, for search-and-rescue operations, as well as for underwater scientific missions. Within such ambitious objective, the proposing institutions also intend to demonstrate the achievable operational capabilities, in a proof-of-concept form, by also integrating the results within prototype experimental systems. In fact, on the basis of the knowledge and experiences owned by the consortium; of its available logistic structures, laboratories and equipment; as well on the basis of already available advanced-stage designs for the experimental systems; the consortium is confident on the possibility of coordinately develop all the necessary technological and methodological aspects; while also converging toward their final integration on the mentioned prototype systems; to be in parallel realized; starting from the sub-systems and advanced-stage.

Line following guidance control: Application to the Charlie unmanned surface vehicle

A line following guidance solution for underactuated marine systems is presented. The approach differs from other ones known in the literature in the definition of the error variables to be stabilized to zero. The proposed guidance technique has been applied to the Charlie USV (Unmanned Surface Vehicle), developed by CNR-ISSIA Autonomous robotic systems and control group, and experimental results are presented.

Prioritized closed-loop inverse kinematic algorithms for redundant robotic systems with velocity saturations

Standard kinematics prioritized task based motion control solutions do not take into account the physical limitations in terms of maximum actuator speed of robots. In this paper, a prioritized task based kinematics control solution is presented that, under given conditions on the kind of concurrent tasks to be pursued, guarantees task error stability and convergence. Moreover the joint velocities are guaranteed to be bounded by a desired threshold. As for other a null-space projection techniques known in the literature, joint speed commands are computed in such a way that lower priority tasks do not interfere with higher priority ones in the assumption that joint speeds can be arbitrarily large: in addition, if joint speeds are to be bounded by a desired value, joint velocity commands are limited by dynamically chosen values depending on the task priority. As a result, joint velocities are always bounded such that, if necessary, higher priority tasks are executed first.

An Entropy-Like Estimator for Robust Parameter Identification

This paper describes the basic ideas behind a novel prediction error parameter identification algorithm exhibiting high robustness with respect to outlying data. Given the low sensitivity to outliers, these can be more easily identified by analysing the residuals of the fit. The devised cost function is inspired by the definition of entropy, although the method in itself does not exploit the stochastic meaning of entropy in its usual sense. After describing the most common alternative approaches for robust identification, the novel method is presented together with numerical examples for validation.

An application of mobile robotics for olfactory monitoring of hazardous industrial sites

Purpose – The purpose of this paper is to present a mobile robot with an olfactory capability for hazardous site survey. Possible applications include detection of gas leaks and dangerous substances along predefined paths, inspection of pipes in factories, and mine sweeping.Design/methodology/approach – The mobile sentry is equipped with a transducer array of tin oxide chemical sensors, compliant with the standard interface IEEE 1451, which provides odour‐sensing capability, and uses differential drive and spring‐suspended odometric trackballs to move and localize in the environment. The monitoring strategy comprises two stages. First, a path learning operation is performed where the vehicle is remotely controlled through some potential critical locations of the environment, such as valves, pressure vessels, and pipelines. Then, the robot automatically tracks the prerecorded trajectory, while serving as an electronic watch by providing a real‐time olfactory map of the environment. Laboratory experiments a...