Enrico Pagello

ICRA Conference 2011 Conference Paper

Omnidirectional dense large-scale mapping and navigation based on meaningful triangulation

• Alberto Pretto
• Emanuele Menegatti
• Enrico Pagello

In this work, we propose a robust and efficient method to build dense 3D maps, using only the images grabbed by an omnidirectional camera. The map contains exhaustive information about both the structure and the appearance of the environment and it is well suited also for large scale environments. We start from the assumption that the surrounding environment (the scene) forms a piecewise smooth surface represented by a triangle mesh. Our system is able to infer, without any odometry information, the structure of the environment along with the ego-motion of the camera by performing a robust tracking of the projection of this surface in the omnidirectional image. The key idea is to use a guess of the triangle mesh subdivision based on a constrained Delaunay triangulation built according to a set of point features and edgelet features extracted from the image. In such a way, we take into account both the corners and the edges of the scene imaged by the camera, constrained by the topology of the triangulation in order to improve the stability of the tracking process. Both motion and structure parameters are estimated using a direct method inside an optimization framework, taking into account the topology of the subdivision in a robust and efficient way. We successfully tested our system in a challenging urban scenario along a large loop using an omnidirectional camera mounted on the roof of a car.

ICRA Conference 2010 Conference Paper

Fast operation of anatomical and stiff tendon neuromuscular models in EMG-driven modeling

• Massimo Sartori
• David G. Lloyd
• Monica Reggiani
• Enrico Pagello

The inclusion of robotic systems in physiotherapy allows developing new solutions for the rehabilitation and support of disabled people. Our research addresses the core problem for the advancement of such applications: the availability of a human machine interface offering intuitive control of robotic devices. In this paper we present an EMG-driven model of the human lower limb based on that previously developed by Lloyd et al. We then introduce a set of enhancements that allow reducing time and memory requirements and provide real-time performances for the control of a lower limb powered orthosis.

ICRA Conference 2009 Conference Paper

A visual odometry framework robust to motion blur

• Alberto Pretto
• Emanuele Menegatti
• Maren Bennewitz
• Wolfram Burgard
• Enrico Pagello

Motion blur is a severe problem in images grabbed by legged robots and, in particular, by small humanoid robots. Standard feature extraction and tracking approaches typically fail when applied to sequences of images strongly affected by motion blur. In this paper, we propose a new feature detection and tracking scheme that is robust even to non-uniform motion blur. Furthermore, we developed a framework for visual odometry based on features extracted out of and matched in monocular image sequences. To reliably extract and track the features, we estimate the point spread function (PSF) of the motion blur individually for image patches obtained via a clustering technique and only consider highly distinctive features during matching. We present experiments performed on standard datasets corrupted with motion blur and on images taken by a camera mounted on walking small humanoid robots to show the effectiveness of our approach. The experiments demonstrate that our technique is able to reliably extract and match features and that it is furthermore able to generate a correct visual odometry, even in presence of strong motion blur effects and without the aid of any inertial measurement sensor.

ICRA Conference 2009 Conference Paper

Range-only SLAM with a mobile robot and a Wireless Sensor Networks

• Emanuele Menegatti
• Andrea Zanella
• Stefano Zilli
• Francesco Zorzi
• Enrico Pagello

This paper presents the localization of a mobile robot while simultaneously mapping the position of the nodes of a Wireless Sensor Network using only range measurements. The robot can estimate the distance to nearby nodes of the Wireless Sensor Network by measuring the Received Signal Strength Indicator (RSSI) of the received radio messages. The RSSI measure is very noisy, especially in an indoor environment due to interference and reflections of the radio signals. We adopted an Extended Kalman Filter SLAM algorithm to integrate RSSI measurements from the different nodes over time, while the robot moves in the environment. A simple pre-processing filter helps in reducing the RSSI variations due to interference and reflections. Successful experiments are reported in which an average localization error less than 1 m is obtained when the SLAM algorithm has no a priori knowledge on the wireless node positions, while a localization error less than 0. 5 m can be achieved when the position of the node is initialized close to the their actual position. These results are obtained using a generic path loss model for the transmission channel. Moreover, no internode communication is necessary in the WSN. This can save energy and enables to apply the proposed system also to fully disconnected networks.

ICRA Conference 2007 Conference Paper

Exploring Different Coherence Dimensions to Answer Proximity Queries for Convex Polyhedra

• Claudio Mirolo
• Stefano Carpin
• Enrico Pagello

Different coherence dimensions can be considered to improve the performances of an algorithm for computing collision translations of pairs of convex polyhedra. The algorithm's peculiar approach, based on convex minimization, is well suited to work without initialization and also endowed with an inherently embedded mechanism to exploit spatial coherence in a broader sense than other related approaches usually do. After a brief outline of the algorithm, we summarize the outcomes of several numerical experiments meant to explore extensively the incremental behavior of the algorithm while controlling the coherence parameters. In order to assess the efficacy and the potential of the approach, the performances are also discussed in the light of the results on H-Walk, an algorithm specifically designed to adapt to variable coherence.

ICRA Conference 2006 Conference Paper

A Performance Comparison of Three Algorithms for Proximity Queries Relative to Convex Polyhedra

• Stefano Carpin
• Claudio Mirolo
• Enrico Pagello

This paper presents a comparative analysis relative to the experimental performances of an asymptotically fast and incremental algorithm, recently developed to compute collision translations for pairs of convex polyhedra. The algorithm may be worth considering because it solves a proximity problem which is less widely addressed than distance, as well as because of its peculiar computation strategy, well suited to work without initialization, but also endowed with an inherently embedded mechanism to exploit spatial coherence. Numerical data characterizing the behavior of the algorithm with respect to the complexity of the polyhedra have already been discussed elsewhere, thus here the main focus is on contrasting its performances with those of two popular algorithms designed to compute distances between polyhedra. Although the considered "yardsticks" answer different proximity queries, and although one of the techniques is meant to deal with general polyhedra, the results presented in this paper should help to assess the efficacy and potential of the approach under analysis. All the three algorithms, indeed, share the same kind of application context; moreover, on the basis of the asymptotic bounds discussed in the literature, distances and collision translations require similar computational efforts. A thorough comparison of the reported query times and, more significantly, of the corresponding trends seems to show that the behavior of the novel algorithm is quite interesting, especially when used without initialization, what should encourage further work on its peculiar approach

ICRA Conference 2005 Conference Paper

Making Collective Behaviours to work through Implicit Communication

• Antonio D'Angelo
• Enrico Pagello

The aim of this paper is to investigate how stigmergic information allow each individual of a group of autonomous robots to take advantages from other individual behaviors. The proposed analysis is based on the roboticle model where sensor data and effector commands are treated as energy exchange between the robot and its environment, eventually populated by other robots. Without explicit communication, the collective behavior of a group of teammates can be forced only if the robot designer makes each robot to become aware of distinguishing configuration patterns in the environment. Usually, the job is accomplished both by evaluating descriptive conditions as macroparameters and an appropriate dynamic role assignment among teammates. Since observed individual behaviors can affect the normal course of operations for each robot propagating to other teammates, we want to address some issues on how a collective behavior is fired and maintained.

IROS Conference 2004 Conference Paper

Testing omnidirectional vision-based Monte Carlo localization under occlusion

• Emanuele Menegatti
• Alberto Pretto
• Enrico Pagello

One of the most challenging issues in mobile robot navigation is the localization problem in densely populated environments. In this paper, we present a new approach for vision-based localization able to solve this problem. The omnidirectional camera is used as a range finder sensitive to the distance of color transitions, whereas classical range finder; , like lasers or sonars, are sensitive to the distance of the nearest obstacles. The well-known Monte-Carlo localization technique was adapted for this new type of range sensor. The system runs in real time on a low-cost pc. In this paper we present experiments, performed in a crowded RoboCup middle-size field, proving the robustness of the approach to the occlusions of the vision sensor by moving obstacles (e. g other robots); occlusions that are very likely to occur in a real environment. Although, the system was implemented for the RoboCup environment, the system can be used in more general environments.

IROS Conference 2003 Conference Paper

How intelligent behavior can emerge from a group of roboticles moving around

• Antonio D'Angelo
• Jun Ota 0001
• Enrico Pagello

The robotic model considered hereafter is an attempt to deal with the problem of mobility for simplified holonomic mobile robots, such as Braitenberg vehicles. The aim is to find out which behavioural constraints are needed to make emerging a collective behaviour in the form of "mobility task". In our model "situatedness" and "embodiment" are defined as in the traditional behaviour-based approaches. The situated body of such a simplified robot is reach enough to be more than a merely symbol manipulating process. The model provides sensor data and effector commands with the same meaning of energy exchange between the robot and its environment, eventually populated by other robots. When a group of robots want to cooperate for a common goal it uses "stigmergy" to allow each individual to take advantage from other individual behaviours. Stigmergy detection is evaluated by the so called "macroparameters" and triggered by a dynamical assignment of "roles", which can force a collective behaviour. The concept of "perceptual perturbation" introduced in our robotic model is a useful abstract tool to figure out collective mobility tasks. This property stems from the "autopoietic loop" shown by each individual and which, under specified conditions, can interact with other ones to form one or more autopoietic loops involving two or more individuals. Collective behaviours eventually emerge as a consequence of a non-linear interaction among behaviours.

ICRA Conference 2002 Conference Paper

Using Omnidirectional Vision within the Spatial Semantic Hierarchy

• Emanuele Menegatti
• Enrico Pagello
• Mark Wright

Reports the steps undertaken in our work aimed to demonstrate the effectiveness of an omnidirectional vision sensor when conjugated with the spatial semantic hierarchy. The spatial semantic hierarchy was proposed by Kuipers (2000) as a method for map building with robots. In our work, a robot builds a topological map of an unknown environment, using the spatial semantic hierarchy and an omnidirectional vision system as the only sensor. We present a new omnidirectional mirror and a new robot. The new mirror was expressly designed for this application, the robot's chassis was designed to create a synergy with the omnidirectional vision sensor. A complete description of our project is reported, underlying the strict link it is possible to create between omnidirectional vision and the spatial semantic hierarchy. Experiments in simulated environments and in real environments produced positive results.

ICRA Conference 2001 Conference Paper

Flexible Exploitation of Space Coherence to Detect Collisions of Convex Polyhedra

• Claudio Mirolo
• Enrico Pagello

The paper presents a fast algorithm to compute collision translations for pairs of convex polyhedra with some interesting features. From a theoretical viewpoint, besides the novelty of the approach, the polylog asymptotic trend in the average case is as good as that of the best algorithms proposed to solve the similar problems. On the other hand, the measured performances to detect possible collisions from scratch are satisfactory, and this is especially true in cases where the bodies do not collide. However, the most peculiar feature is a simple and flexible mechanism to exploit spatial coherence in a continuous range, which distinguishes this algorithm from all the other proposals we know. Furthermore, the nature of the approach is such that the self-tuning capability is attained at negligible additional costs even for unrelated collision tests. After a brief outline of the main ideas characterizing the approach, a set of numerical results are summarized. The proposed algorithm may be appropriate to plan collision-free paths, both online and off-line, on the basis of fine-grain descriptions of the objects in the workspace.

ECAI Conference 2000 Conference Paper

Can Representation be Liberated from Symbolism: Modeling Robot Actions with Roboticles

• Antonio D'Angelo
• Federico Montesello
• Enrico Pagello

IROS Conference 2000 Conference Paper

Fast convex minimization to detect collisions between polyhedra

• Claudio Mirolo
• Enrico Pagello

The subject of the paper is a fast algorithm for detecting collisions of two convex polyhedra translating in space. A major feature is the novelty of the approach: collision detection for two convex bodies is reduced to collision detection for pairs of planar sections and minimization of a bivariate convex function; furthermore, most of the subproblems are solved using two-dimensional geometry. As proved by previous theoretical work, on this basis it is possible to design an algorithm, which runs in O(log/sup 2/n) time in the average and O(log/sup 3/n) in the worst case, where n is the total number of vertices. Here the focus is on a more practical version of the algorithm, which is particularly suited to plan collision-free paths on the basis of fine-grain descriptions of the objects in the workspace, as it is the case for the systems supported by sophisticated geometric modelers. After explaining the main ideas underlying the approach, a set of experimental results are presented and discussed in some depth.

IROS Conference 2000 Conference Paper

Using collision avoidance algorithms for designing multi-robot emergent behaviors

• Roberto Polesel
• Robert Rosati
• Alberto Speranzon
• Carlo Ferrari
• Enrico Pagello

We discuss how to induce a set of collective emergent behaviors into a team of real robots used for soccer robotics. The activation of robot behaviors is organized according to a multi-level control architecture. The emergent cooperative abilities, like exchanging a ball, are achieved through the use of efficient collision avoidance algorithms implemented by a small set of robots able to frequently swap their roles. Our algorithms have been tested on a couple of real robots, Bart and Homer, which played the final game with the middle size league, at RoboCup'99, in Stockholm. This approach can be generalized to allow multi-robot systems to perform various kind of collective tasks in the entertainment field.

ICRA Conference 1997 Conference Paper

A practical motion planning strategy based on a plane-sweep approach

• Claudio Mirolo
• Enrico Pagello

We discuss a practical motion planning strategy based on a two-step approach. First, an approximation of the C-space is built by a plane-sweep algorithm. Then, the search for a solution path drives the necessary refinement steps. Our claim is that an approach based on the incremental characterization of the C-space can be competitive with the best proposed motion planning techniques. We substantiate this claim in the simple case of planning translations of a convex body in the plane. Since the shape of the free space is incrementally recognized by probing the space via collision detection, every item of geometric information is obtained from the analysis of contact configurations involving convex bodies. At any stage the probes provide a partial characterization, represented by a simple cell subdivision and a suitable set of chains approximating the boundaries of the grown obstacles. The cells and their adjacencies do not change during the refinement step, so that the search strategy is straightforward. Although the performances are not optimal in theory, the planning algorithm shows a good behaviour, as demonstrated by a few experiments where it is compared with a quadtree-based strategy.

IROS Conference 1996 Conference Paper

A framework for robust multiple robots motion planning

• Carlo Ferrari
• Enrico Pagello
• Jun Ota 0001
• Tamio Arai

This paper is focused on solving the multiple robots motion planning problem in a robust way, whereas we say that a motion plan is robust if it can be used in spite of small variations in the motion context. After a critical review of their previous research on generating multiple robots motion plans (1995), the authors classify several "sources of instability" useful for establishing criteria for robustness. These sources include variations of the environment model, variations in the number of robots and paths, and variations in the motion parameters of the moving items. We define various "impact factors", that evaluate how much a variation affects a given plan. For example, a new path (for a robot) can be associated with a collision impact factor, that estimate how many collisions among moving objects may occur along that path. Hence, to evaluate the motion plan robustness, we define how quality values for motion plans are modified by the impact factors.

IROS Conference 1995 Conference Paper

Planning multiple autonomous robots motion in space and time

• Carlo Ferrari
• Enrico Pagello
• Jun Ota 0001
• Tamio Arai

We address the problem of planning the motion of multiple autonomous robots, by analysing their behaviour in space and time. Proper representations have been studied for both domains, with a particular emphasis on the definition of some performance indexes to weight the goodness of a path concerning motion and time performances. Sublinear algorithms have been used for planning in space while reasoning in the temporal domain is based on a proper subdivision of the time axis that leads to polynomial algorithms.

ICRA Conference 1994 Conference Paper

On the Scenario and Heuristics of Disassemblies

• Wen-Han Qian
• Enrico Pagello

A general scenario of disassembly is figured out, starting from the authors' past study of the internal structures of machines and devices, based on a mechanical engineer's point of view. The authors argue that among all data relevant to assembly, the key data for generating assembly sequences are the liaison type and the assembly direction. From these data many important geometrical, topological and technological constraints can be inferred that can be used as criteria for reducing the user's input data and the information to be extracted from the CAD database. These criteria minimize the possible decompositions at each stage of disassembly, and may even guide the search towards the best plan. A fast planner has been implemented in PROLOG, giving a user friendly system capable of generating optimal assembly plans very quickly, with a computational cost roughly proportional to the number of parts in the final assembly. >

IROS Conference 1991 Conference Paper

Local geometric issues for spatial reasoning in robot motion planning

• Claudio Mirolo
• Enrico Pagello

Starting from their (1989) past work on geometric modelling, the authors discuss various techniques for the robot motion planning problem and suggest further work in this field. The efficiency of any approach to motion planning is strongly related to the ability of getting relevant information from a small subset of the geometric items. Considering a restricted portion of the configuration space around the current configuration of the introduces some local issues. So, a spatial reasoning system is defined by the interactions between local focusing and a global view of the planning process. >

ECAI Conference 1988 Conference Paper

A Multiagent Planner for Reasoning with Incomplete Knowledge in a Distributed Environment

• Antonio D'Angelo
• Claudio Mirolo
• Enrico Pagello

MFCS Conference 1976 Conference Paper

Programs, Computations and Temporal Features

• Marco Colombetti
• Enrico Pagello

Abstract Predicate Logic is a natural support to computing systems: computation and deduction are closely related. The way to describe proof strategies can clarify the theoretical soundness of programming. This description involves the clarification of the role of control statements. A semantic analysis of program statements can suggest useful restrictions to the interpreter. These find a natural representation in a temporal framework.