The NavBelt-a computerized travel aid for the blind based on mobilerobotics technology

This paper presents a new concept for a travel aid for the blind. A prototype device, called the NavBelt, was developed to test this concept. The device can be used as a primary or secondary aid, and consists of a portable computer, ultrasonic sensors, and stereophonic headphone. The computer applies navigation and obstacle avoidance technologies that were developed originally for mobile robots. The computer then uses a stereophonic imaging technique to process the signals from the ultrasonic sensors and relays their information to the user via stereophonic headphones. The user can interpret the information as an acoustic “picture” of the surroundings, or, depending on the operational mode, as the recommended travel direction. The acoustic signals are transmitted as discrete beeps or continuous sounds. Experimental results with the NavBelt simulator and a portable prototype show that users can travel safely in an unfamiliar and cluttered environment at speeds of up to 0.8 m/s     

Design and development of a fuzzy agent-based model to measure interest rate expectations

The financial system, which has been investigated by various researchers, is a rather complicated environment. Most research has only been concerned with quantitative factors (technical indexes), though qualitative factors (e.g., political situation, social conditions, international events, government policies, among others) play a critical role in the financial system environment, determining the regulatory policies within an economy. This paper presents a fuzzy knowledge-based model to measure the qualitative aspects related to one of the most important financial instruments used to regulate an economy, the base interest rate. The development and assessment of the proposed model was based on the Brazilian economy. Evaluation of the results obtained indicates that our approach gives good results when compared with real data and statistical-based forecasting tools. The main advantage of our approach is its capability to forecast long term interest rate expectations when combined with a powerful econometric model.     

Methods for the Reduction of Odometry Errors in Over-Constrained Mobile Robots

This paper presents an analysis of odometry errors in over-constrained mobile robots, that is, vehicles that have more independent motors than degrees of freedom. Examples of over-constrained vehicles are the various 6-wheeled Mars Rovers like Rocky-7, Rocky-8, or Fido.Based on our analysis we developed two novel measures aimed at reducing odometry errors. We also developed a novel method that serves as a framework for the implementation of the two new measures, as well as for other, conventional error reducing measures.One of the two new measures, called Fewest Pulses Measure, makes use of the observation that most terrain irregularities, as well as wheel slip, result in an erroneous overcount of encoder pulses. The second new measure, called Cross-coupled Control Measure, optimizes the motor control algorithm of the robot to reduce synchronization errors that would otherwise result in wheel slip with conventional controllers.The novel method that serves as a framework for other measures is based on so-called Expert Rules. In this paper we formulate three expert rules aimed at reducing dead-reckoning errors. Two of these expert rules are related to the foregoing discussion on error reducing measures. The third expert rule adds a gyroscope to the system and we re-examine the effectiveness of the odometry error-reducing measures in the context of this addition.In the work described in this paper we modified a Pioneer AT skid-steer platform by providing it with four independent drive motors and encoders. We implemented our error-reducing measures and the expert rule method on this over-constrained platform and present experimental results.     

The OmniMate: A guidewire- and beacon-free AGV for highly reconfigurable applications

This paper introduces a new automated guided vehicle (AGV) for guidewire-free industrial applications where rapid reconfiguration is required. The AGV, called OmniMate, has full omnidirectional motion capabilities, can correct odometry errors without external references, and offers a large 183 x 91 cm (72 x 36 in) loading deck. A patented, so-called compliant linkage avoids the excessive wheel slippage often found in other omnidirectional platforms. The paper describes the kinematic design and the control system of the platform and explains its unique odometry error correction method, called internal position error correction (IPEC). IPEC renders the OmniMate's odometry almost completely insensitive to even severe irregularities of the floor, such as bumps, cracks, or traversable objects. Dead-reckoning is enhanced further by the addition of a fibre-optics gyroscope. Because of its extraordinary dead-reckoning capabilities the OmniMate can travel over extended distances while following a pre-programmed path fully automatically. The paper describes an implemented 'leadthrough' teaching system, in which an operator guides the OmniMate along a desired path, while the OmniMate records the path to memory. Later, in path execution mode, the OmniMate reproduces the path accurately, observing commanded velocities. With this system it is possible and feasible to program or modify a complete path within minutes.     

State space representation of routing flexibility

This paper describes a state space representation for sequencing and routing flexibility in manufacturing systems. Routing flexibility is represented using five different stages as follows: (i) Precedence Graph of Operations; (ii) State Transition Graph of Manufacturing Operation Sequences; (iii) State Transition Graph of Manufacturing Operation Routes; (iv) Disjunctive Normal Form (DNF) Representation of Manufacturing Sequences; and (v) DNF Representation of Manufacturing Routes. Each representation is able to represent sequencing and routing flexibility at different levels of detail. The third representation is capable of enumerating all possible manufacturing operation routes that can be applied to a certain part, being the most complete representation. Bounds for computation of some of the representations are presented to help users select the most suitable for a specific problem context. The efficacy of the representation is demonstrated through its application to problems such as job route selection and routing flexibility measure.     

Auditory guidance with the Navbelt-a computerized travel aid forthe blind

A blind traveler walking through an unfamiliar environment and a mobile robot navigating through a cluttered environment have an important feature in common: both have the kinematic ability to perform the motion, but they are dependent on a sensory system to detect and avoid obstacles. The paper describes the use of a mobile robot obstacle avoidance system as a guidance device for blind and visually impaired people. Just as electronic signals are sent to a mobile robot's motion controllers, auditory signals can guide the blind traveler around obstacles, or alternatively, they can provide an “acoustic image” of the surroundings. The concept has been implemented and tested in a new travel aid for the blind, called the Navbelt. The Navbelt introduces two new concepts to electronic travel aids (ETA's) for the blind: it provides information not only about obstacles along the traveled path, but also assists the user in selecting the preferred travel path. In addition, the level of assistance can be automatically adjusted according to changes in the environment and the user's needs and capabilities. Experimental results conducted with the Navbelt simulator and a portable experimental prototype are presented     

Future considerations in margarine fortification

The present and future nutritional rationale for margarine fortification is discussed. The trend to increase the polyunsaturated fat content of margarine coupled with the newer knowledge of vitamin E requirements suggest that vitamin E fortification of margarine be considered; a practice common in Europe. The composition of current margarine is reviewed with respect to PUFA and vitamin E. The vitamin A content, low cost, wide availability and high caloric value of margarine suggest a possible role in feeding the underprivileged. In this connection, the use of margarine as a carrier of lysine to improve the protein quality of cereal foods with which it is used is suggested.     

Mobile robot positioning: Sensors and techniques

Exact knowledge of the position of a vehicle is a fundamental problem in mobile robot applications. In search of a solution, researchers and engineers have developed a variety of systems, sensors, and techniques for mobile robot positioning. This article provides a review of relevant mobile robot positioning technologies. The article defines seven categories for positioning systems: (1) Odometry, (2) Inertial Navigation, (3) Magnetic Compasses, (4) Active Beacons, (5) Global Positioning Systems, (6) Landmark Navigation, and (7) Model Matching. The characteristics of each category are discussed and examples of existing technologies are given for each category. The field of mobile robot navigation is active and vibrant, with more great systems and ideas being developed continuously. For this reason the examples presented in this article serve only to represent their respective categories, but they do not represent a judgment by the authors. Many ingenious approaches can be found in the literature, although, for reasons of brevily, not all could be cited in this article. © 1997 John Wiley & Sons, Inc.     

Mixed Reversible Covalent Crosslink Kinetics Enable Precise,Hierarchical Mechanical Tuning of Hydrogel Networks

Hydrogels play a central role in a number of medical applications and new research aims to engineer their mechanical properties to improve their capacity to mimic the functional dynamics of native tissues. This study shows hierarchical mechanical tuning of hydrogel networks by utilizing mixtures of kinetically distinct reversible covalent crosslinks. A methodology is described to precisely tune stress relaxation in PEG networks formed from mixtures of two different phenylboronic acid derivatives with unique diol complexation rates, 4‐carboxyphenylboronic acid, and o‐aminomethylphenylboronic acid. Gel relaxation time and the mechanical response to dynamic shear are exquisitely controlled by the relative concentrations of the phenylboronic acid derivatives. The differences observed in the crossover frequencies corresponding to pK_a differences in the phenylboronic acid derivatives directly connect the molecular kinetics of the reversible crosslinks to the macroscopic dynamic mechanical behavior. Mechanical tuning by mixing reversible covalent crosslinking kinetics is found to be independent of other attributes of network architecture, such as molecular weight between crosslinks.