Marcelo Trevisan

Exploration method using harmonic functions

Abstract Harmonic functions provide optimal potential maps for robot navigation in a previously explored static environment. Here we investigate the performance of an algorithm for exploration based on partial updates of a harmonic potential in an occupancy grid. We consider that while the robot moves it carries along an activation window whose size is of the order of the sensor’s range. The activation window recruits grid points to participate in the potential calculation. By using simulations and experiments with the Nomad 200 robot we investigate the algorithm performance in respect to parameters such as the frequency of updates and the numerical method used to calculate the harmonic potential.

Exploratory Navigation Based on Dynamical Boundary Value Problems

The paper presents a general framework for concurrent navigation and exploration of unknown environments based on discrete potential fields that guide the robot motion. These potentials are obtained from a class of partial differential equation (PDE) problems called boundary value problems (BVP). The boundaries are generated from sensor readings and therefore they change as the robot moves. This framework corresponds to an extension of our previous work (Prestes, E., Idiart, M. A. P., Engel, P. and Trevisan, M.: Exploration technique using potential fields calculated from relaxation methods, in: IEEE/RSJ International Conference on Intelligent Robots and Systems, 2001, p. 2012; Prestes, E., Engel, P. M., Trevisan, M. and Idiart, M. A.: Exploration method using harmonic functions, Robot. Auton. Syst.40(1) (2002), 25–42). Here, we propose that a careful choice of the PDE and the boundary conditions can produce efficient exploratory behaviors in sparse and dense environments. Furthermore, we show how to extend the exploratory behavior to produce new ones by changing dynamically the boundary function (the value of the potential at the boundaries) as the exploration takes course. Our framework is validated through a series of experiments with a real robot in office environments.

Autonomous Learning Architecture for Environmental Mapping

Here we propose an architecture for an autonomous mobile agent that explores while mapping a two-dimensional environment. The map is a discretized model for the localization of obstacles, on top of which a harmonic potential field is computed. The potential field serves as a fundamental link between the modeled (discrete) space and the real (continuous) space where the agent operates. It indicates safe paths towards non-explored regions. Harmonic functions were originally used as global path planners in mobile robotics. In this paper, we extend its functionality to environment exploration. We demonstrate our idea through experimental results obtained using a Nomad 200 robot platform.

Exploration technique using potential fields calculated from relaxation methods

The use of relaxation methods for calculation of harmonic potentials has proved to be a powerful technique for path planning in a known environment. We show that this idea can be successfully extended to exploration of unknown environments. The potential is calculated in a partial version of the map, represented on an occupancy grid, and it indicates safe paths towards the unexplored regions. We demonstrate that a complete relaxation of the potential is not necessary to accomplish smooth performances. Furthermore, we discuss the effect of different relaxation methods in the calculation of harmonic potential.

Technological Capability's Predictor Variables

The aim of this study was to identify the factors that influence in configuration of the technological capability of companies in sectors with medium-low technological intensity. To achieve the goal proposed in this article a survey was carried out. Based on the framework developed by Lall (1992) which classifies firms in basic, intermediate and advanced level of technological capability; it was found that the predominant technological capability is intermediate, with 83.7% of respondent companies (plastics companies in Brazil). It is believed that the main contribution of this study is the finding that the dependent variable named “Technological Capability” can be explained at a rate of 65% by six variables: development of new processes; selection of the best equipment supplier; sales of internally developed new technology to third parties; design and manufacture of equipment; study of the work methods and perform inventory control; and improvement of product quality.

BVP-exploration: further improvements

We propose some techniques to improve the exploration method based on BVP and demonstrate that, at least, for exploration in two dimensional space, we can reduce enormously the computation cost of the harmonic function method for exploration without losing the important properties of the method. Switching between local and global potential calculation and using an adaptive activation window result in a computationally efficient and refined mapping process.

Directing a random walker with optimal potentials

In a two-dimensional discrete environment we obtain numerically the potential surface that minimizes the diffusion time for a particle that is guided toward a goal point, for a given temperature. The optimal potential shape is a branched one from the confluence of three factors that helps direct diffusion: the reduction of the dimensionality of the walk, the optimization of the potential shape in one dimension, and the minimization of the paths. We discuss the possible applications of the result to robotic navigation.

Oriented exploration in non-oriented sparse environments

The use of relaxation methods for calculation of harmonic potentials has proved to be a powerful technique for path planning in a known environment and recently for exploration of unknown environments. In the latter case, the potential is calculated on partial versions of the map represented on an occupancy grid, and it indicates safe paths towards the unexplored regions. Here, we show that exploration based on potentials functions calculated from boundary value problems works fairly well in sparse environments provided that we no longer use harmonic potentials. We propose different families of potentials that improve the exploration process in this kind of environment, while keeping the important property of not having dynamical local minima.

NOSTALGIA, ANTICONSUMO SIMBÓLICO E BEM-ESTAR: A AGRICULTURA URBANA

The establishment of a global consumption culture had as a consequence a growing concern with the impact of consumption practices on the environment, as well as on the general and personal well-being. In this context emerges the urban agriculture (UA) associated to environmental, social and health benefits (SLATER, 2001). The objective of this study is to understand the meaning of the UA phenomenon as a consumption practice, identifying which theories are related to it. In order to reach that goal, a qualitative research used as data collection in-depth interviews. The subjects were experts and practitioners in UA living in 9 neighborhoods in urban areas of a Brazilian city with a population bigger than 1 million inhabitants. Results showed double motivation for the UA practice, extrinsic (example) and intrinsic (well-being), linking the UA to environmental concerns, to health and well-being, and the respect and pride for a nostalgic cultural heritage.

Nostalgia, symbolic anticonsumption and well-being: urban agriculture

The establishment of a global consumption culture had as a consequence a growing concern with the impact of consumption practices on the environment, as well as on the general and personal well-being. In this context emerges the urban agriculture (UA) associated to environmental, social and health benefits (SLATER, 2001). The objective of this study is to understand the meaning of the UA phenomenon as a consumption practice, identifying which theories are related to it. In order to reach that goal, a qualitative research used as data collection in-depth interviews. The subjects were experts and practitioners in UA living in 9 neighborhoods in urban areas of a Brazilian city with a population bigger than 1 million inhabitants. Results showed double motivation for the UA practice, extrinsic (example) and intrinsic (well-being), linking the UA to environmental concerns, to health and well-being, and the respect and pride for a nostalgic cultural heritage.