Atef Fahim

Analytical Modeling and Experimental Validation of the Braided Pneumatic Muscle

Static models of braided pneumatic muscles (BPMs) reported in the research literature fairly accurately predict the muscle-force-carrying capacity. These models, however, rely on experimentally determined parameters that are valid only for the specific muscle configuration under consideration. This paper presents a fully analytical BPM static model that does not depend on experimentally determined parameters. The proposed approach is based on Newtonian mechanics that considers the mechanical and the geometrical properties of the muscle. Distinctively, this paper includes the muscle end-fixture-diameter effect. Results from the developed model are compared with the experimental ones that have been obtained from prototype BPMs.

An Automated Computerized Auscultation and Diagnostic System for Pulmonary Diseases

Respiratory sounds are of significance as they provide valuable information on the health of the respiratory system. Sounds emanating from the respiratory system are uneven, and vary significantly from one individual to another and for the same individual over time. In and of themselves they are not a direct proof of an ailment, but rather an inference that one exists. Auscultation diagnosis is an art/skill that is acquired and honed by practice; hence it is common to seek confirmation using invasive and potentially harmful imaging diagnosis techniques like X-rays. This research focuses on developing an automated auscultation diagnostic system that overcomes the limitations inherent in traditional auscultation techniques. The system uses a front end sound signal filtering module that uses adaptive Neural Networks (NN) noise cancellation to eliminate spurious sound signals like those from the heart, intestine, and ambient noise. To date, the core diagnosis module is capable of identifying lung sounds from non-lung sounds, normal lung sounds from abnormal ones, and identifying wheezes from crackles as indicators of different ailments.

k-out-of-m system availability with minimum-cost allocation spares

An optimization method for determining the number of spare units that should be allocated to a k-out-of-m system to minimize the system-spares cost yet attain the specified system availability is presented. The objective function for optimization is a nonlinear integer type. The optimization method is a variation of the simplex search technique used for continuous functions. The optimization problem is cast in a form that minimizes the system-spares cost, with the required system availability as an inequality constraint. Results obtained by using the proposed optimization technique, as well as the computation time required for optimization, are compared to those for methods developed specifically for dealing with nonlinear integer problems. The method is simple, easy to implement, and yet very effective in dealing with the spare allocation problem for k-out-of-m:F systems. >

Accuracy-speed relationships of a robotic filament winding cell.

Abstract Filament winding is a process in which tensioned resio-impregnated continuous fibers are placed on specified paths of a rotating mandrel to cover the entire surface thus forming a composite component. Traditionally, filament winding is carried out on multi-saris numerically controlled lathe-like machines. This paper describes the evaluation of a robot based filament winding cell consisting of an industrial robot (ASEA IRB 6/2) and an in-house fabricated mandrel drive mechanism, both being coordinated by a personal computer. As in many manufacturing processes, tradeoffs exist between accuracy and speed. The accuracy vs speed relationships of the robotic winding cell were experimentally determined for discrete, fine and medium movement modes while traversing a segmented delivery eye path for a cylindrical mandrel in three configurations (in-line, offset and angled with respect to the axis of rotation). The results show that the robot winding cell is appropriate for very accurate winding of fiber strands if the mandrel axis is concentric with the mandrel drive axis and the discrete mode (i.e. low speed) of the robot is used. For high speed wet winding all three configurations can be accurately wound in the discrete and fine modes.

The UniSet approach for the programming of flexible manufacturing cells

Abstract Flexible manufacturing cells (FMC) may be considered the most significant development in small-batch manufacturing. Setting-up and operating costs of FMC prove to be the most major hindrance to their large-scale implementation and use, particularly by small and medium size industries. Incompatibilities between the different components constituting the cells and the lack of a unified language/approach to programming and coordinating them are cited as the cause of the complexity of setting up and subsequently operating the cells. In order to eliminate these difficulties, a new philosophy for setting-up, programming and control of FMC has been developed. This paper reports the effort to develop this new unified manufacturing instruction set and its environment, called here “UniSet”, its philosophy and some of the components of the UniSet environment. UniSet has been developed as a non-exclusive unified manufacturing instruction set, based on comparisons of the prevailing machine tool and programming primitives. UniSet allows programmers to deal with only one instruction set, if they so desire, in a single coherent environment, rather than numerous machine programming languages. The software system is coded in an object-oriented programming (OOP) language, Smalltalk, and derives its paradigm from the OO philosophy. Test results are also included to demonstrate the applicability of the approach employed.

A two-phase optimization procedure for integer programming problems

Abstract This paper presents a simple two-phase method for optimizing integer programming problems with a linear or nonlinear objective function subject to multiple linear or nonlinear constraints. The primary phase is based on a variation of the method of steepest descent in the feasible region, and a hem-stitching approach when a constraint is violated. The secondary phase zeros on the optimum solution by exploring the neighborhood of the suboptimum found in the first phase of the optimization process. The effectiveness of this method is illustrated through the optimization of several examples. The results from the proposed optimization approach are compared to those from methods developed specially for dealing with integer problems. The proposed method is simple, easy to implement yet very effective in dealing with a wide class of integer problems such as spare allocation, reliability optimization, and transportation problems.

An optimization method for solving mixed discrete-continuous programming problems

This paper presents a heuristic approach for minimizing nonlinear mixed discrete-continuous problems with nonlinear mixed discrete-continuous constraints. The approach is an extension of the boundary tracking optimization that was developed by the authors to solve the minimum of nonlinear pure discrete programming problems with pure discrete constraints. The efficacy of the proposed approach is demonstrated by solving a number of test problems of the same class published in recent literature. Among these examples is the complex problem of minimizing the cost of a series-parallel structure with redundancies subject to reliability constraint. All tests conducted so far show that the proposed approach obtains the published minima of the respective test problems or finds a better minimum. While it is not possible to compare computation time due to the lack of data on the test problems, for all the tests the minimum is found in a reasonable time.

Development, validation, and parameter sensitivity analyses of a nonlinear mathematical model of air springs

Air springs are highly nonlinear devices. Linear and quasi-linear models of air springs have been developed over the years to analyze and predict their behavior. Such models are shown here to be inadequate to describe the behavior of this highly nonlinear element. A nonlinear mathematical model of air springs has been developed and reported in this paper. The model has been verified experimentally, and has been shown to be effective in predicting the behavior of air springs. The sensitivity of the model to uncertainties in two key parameters is examined.

Hybrid Power Plant Design for a Long-Range Dirigible UAV

Unmanned aerial vehicle (UAV) dirigibles are well suited for surveillance and surveyance missions since they can hover and maintain lift without consuming energy and can be easily deflated for packaging and transportation. The challenge is developing a long endurance system while maintaining a low unit cost. This paper presents a novel hybrid power plant design that addresses both of these requirements. The lightweight design consists of a 4-stroke 14cc gasoline engine in-line with a brushless dc motor/generator and variable pitch propeller capable of producing a maximum power output of 250 W. A method was also developed to compare its performance and endurance to other power plant configurations that could be used in dirigible UAVs. Overall, the proposed hybrid power plant has 674% increase in energy density over that of a purely electric system, thereby proportionally increasing UAV flight time for the same power and weight.

Object-oriented knowledge-based automatic cell programming environment

Abstract This paper describes a cell programming environment that would allow manufacturers to integrate multi-vendor machines into Flexible Manufacturing Cells (FMCs), and deal with problems associated with programming FMCs. The environment consists of the cell programming editor and the automatic generation module. In the cell programming editor, cell programmers can develop cell programs using a Task Level UniSet which supports task-oriented specifications for manipulating cell activities. This approach to cell programming reduces the amount of detail that cell programmers need to consider, and allows them to concentrate on the most important aspects of the task at hand. The automatic generation module is used to transform task specifications into executable programs used by cell constituents. This module is based on efficient algorithms and expert systems which can be used for optimal path planning of robot operations and optimal machining parameters of machine tool operations. The development tool for designing the environment is based on an object-oriented approach which provides simple-to-use and intuitive user interfaces, and allows for the easy development of object models associated with the environment. Test results are illustrated in order to demonstrate the applicability of the environment developed.