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Publicações

Publicações por Marcelo Petry

2013

Increasing Illumination Invariance of SURF Feature Detector through Color Constancy

Autores
Petry, MR; Moreira, AP; Reis, LP;

Publicação
PROGRESS IN ARTIFICIAL INTELLIGENCE, EPIA 2013

Abstract
Most of the original image feature detectors are not able to cope with large photometric variations, and their extensions that should improve detection eventually increase the computational cost and introduce more noise to the system. Here we extend the original SURF algorithm increasing its invariance to illumination changes. Our approach uses the local space average color descriptor as working space to detect invariant features. A theoretical analysis demonstrates the impact of distinct photometric variations on the response of blob-like features detected with the SURF algorithm. Experimental results demonstrate the effectiveness of the approach in several illumination conditions including the presence of two or more distinct light sources, variations in color, in offset and scale.

2013

IntellWheels: Intelligent wheelchair with user-centered design

Autores
Petry, MR; Moreira, AP; Faria, BM; Reis, LP;

Publicação
2013 IEEE 15th International Conference on e-Health Networking, Applications and Services, Healthcom 2013

Abstract
Intelligent wheelchairs can become an important solution to assist physically impaired individuals who find it difficult or impossible to drive regular powered wheelchairs. However, when designing the hardware architecture several projects compromise the user comfort and the wheelchair normal usability in order to solve robotic problems. In this paper we describe the main concepts regarding the design of the IntellWheels intelligent wheelchair. Our approach has a user-centered perspective, in which the needs and limitations of physically impaired users are given extensive attention at each stage of the design process. Finally, our design was evaluated through a public opinion assessment. A statistical analysis suggested that the design was effective to mitigate the visual and ergonomic impacts caused by the addition of sensorial and processing capabilities on the wheelchair. © 2013 IEEE.

2014

Using Kalman Filters to Reduce Noise from RFID Location System

Autores
Abreu, PH; Xavier, J; Silva, DC; Reis, LP; Petry, M;

Publicação
SCIENTIFIC WORLD JOURNAL

Abstract
Nowadays, there are many technologies that support location systems involving intrusive and nonintrusive equipment and also varying in terms of precision, range, and cost. However, the developers some time neglect the noise introduced by these systems, which prevents these systems from reaching their full potential. Focused on this problem, in this research work a comparison study between three different filters was performed in order to reduce the noise introduced by a location system based on RFID UWB technology with an associated error of approximately 18 cm. To achieve this goal, a set of experiments was devised and executed using a miniature train moving at constant velocity in a scenario with two distinct shapes-linear and oval. Also, this train was equipped with a varying number of active tags. The obtained results proved that the Kalman Filter achieved better results when compared to the other two filters. Also, this filter increases the performance of the location system by 15% and 12% for the linear and oval paths respectively, when using one tag. For a multiple tags and oval shape similar results were obtained (11-13% of improvement).

2013

Intelligent Wheelchair Manual Control Methods A Usability Study by Cerebral Palsy Patients

Autores
Faria, BM; Ferreira, LM; Reis, LP; Lau, N; Petry, M;

Publicação
PROGRESS IN ARTIFICIAL INTELLIGENCE, EPIA 2013

Abstract
Assistive Technologies may greatly contribute to give autonomy and independence for individuals with physical limitations. Electric wheelchairs are examples of those assistive technologies and nowadays each time becoming more intelligent due to the use of technology that provides assisted safer driving. Usually, the user controls the electric wheelchair with a conventional analog joystick. However, this implies the need for an appropriate methodology to map the position of the joystick handle, in a Cartesian coordinate system, to the wheelchair wheels intended velocities. This mapping is very important since it will determine the response behavior of the wheelchair to the user manual control. This paper describes the implementation of several joystick mappings in an intelligent wheelchair (IW) prototype. Experiments were performed in a realistic simulator using cerebral palsy users with distinct driving abilities. The users had 6 different joystick control mapping methods and for each user the usability and the users' preference order was measured. The results achieved show that a linear mapping, with appropriate parameters, between the joystick's coordinates and the wheelchair wheel speeds is preferred by the majority of the users.

2011

Intelligent Wheelchair Simulation: Requirements and Architectural Issues

Autores
Marcelo Petry; António Paulo Moreira; Luís Paulo Reis; Rosaldo Rossetti

Publicação
Robotica2011 - 11th International Conference on Mobile Robots and Competitions, pp.102-107, Lisboa, Portugal

Abstract
Using robotic simulators, researchers are able to improve the algorithms of their robotics platforms before testing them in real environments. In fact, the safe environment provided by simulation is important, especially for robots that are constantly in contact with human beings, such as assistive robots and intelligent wheelchairs. Here, we propose to take advantage of an available general robotics simulator to model the IntellWheel's intelligent wheelchair prototype and its environment, enabling patient's drills and creating a test bed to refine and to experiment new methodologies of autonomous navigation, obstacle avoidance and human-machine interaction. As a result of the evaluation of four general simulators, the USARSim simulator has demonstrated to be more suitable to serve as basis for the IntellWheels simulation prototype. The development of a rough model of the intelligent wheelchair and of an appropriate test environment proved that with some modifications USARSim is able to provide a very realistic simulation platform for Intelligent Wheelchairs.

2011

IntellWheels: A Modular Development Platform for Intelligent Wheelchairs

Autores
Rodrigo Antonio Marques Braga; Marcelo Petry; Luis Paulo Reis; António Paulo Moreira

Publicação
JRRD - Journal of Rehabilitation Research & Development, vol.48, no.9, pp.1061-1076

Abstract
Intelligent wheelchairs can become an important solution to assist individuals suffering from disabilities and are thus unable to perform their daily activities using classic powered wheelchairs. This paper describes the concept and design of IntellWheels, a modular platform to facilitate the development of intelligent wheelchairs through a multi-agent system paradigm. In fact, modularity is achieved not just in the software perspective, but also through a generic hardware framework, which was designed to fit, in a straightforward manner, almost any commercial powered wheelchair. Experimental results demonstrate the successful integration of all modules in the platform, providing a safe motion to the intelligent wheelchair. Furthermore, the results achieved with a prototype running in autonomous mode, in a simulated and mixed reality environments, also demonstrate the potential of our approach. Although some future research is still necessary in order to fully accomplish its objectives, preliminary tests have shown that IntellWheels will be able to effectively reduce user's limitations, offering them a much more independent life.

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