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We consider here a class of compliant mechanisms consisting of one or more flexible beams, the manipulation of which relies on the deflection of the flexible beams. As compared with traditional rigid-body mechanisms, compliant mechanisms have the advantages of no relative moving parts and thus involve no wear, backlash, noises, and lubrication. This paper presents a formulation based on shooting method (SM) and two numerical solvers for analyzing compliant mechanisms consisting of multiple flexible members that may be initially straight or curved. Five compliant mechanisms, which are chosen to illustrate both initially straight and curved members and different types of joint/contact conditions, are formulated to exemplify analyses using the generalized shooting method for a wide spectrum of applications. The advantages of the generalized SM over the finite difference FD and finite element FE methods are demonstrated numerically. Unlike FD or FE methods that rely on fine discretization of beam members to improve its accuracy, the generalized SM that treats the boundary value problem (BVP) as an initial value problem can achieve higher-order accuracy relatively easily, and hence is more efficient computationally. In addition, the computed results were validated experimentally. It is expected that the generalized SM presented here will offer designers a useful analysis tool and will effectively facilitate the process of design and optimization of compliant mechanisms. [DOI: 10.1115/1.2202139] Keywords: shooting method, compliant mechanism, Gauss-Newton method, flexible beam

Optical fibers are drawn from preforms (fused silica glass rods) typically made up of two concentric cylinders (the core rod and the clad tube), which are usually joined in a separate fusion process. The setup time and hence manufacturing cost can be significantly reduced if the two cylinders can be joined in the same furnace in which the fiber is drawn. A good understanding of the transient temperature distribution is needed for controlling the feed rate to avoid thermally induced cracks. Since direct measurement of the temperature fields is often impossible, the geometrical design of the preform and the control of the feed rate have largely been accomplished by trials-and-errors. The ability to predict the transient temperature distribution and the thermally induced stresses will provide a rational basis to design optimization and feed rate control of the process. In this paper, we present an analytical model to predict the transient conductive-radiative transfer as two partially joined, concentric glass cylinders with specular surfaces are fed into the furnace. Finite volume method (FVM) is used to solve the radiative transfer equation (RTE). The specular surface reflectivity is obtained by the Fresnel's law and the Snell's law. The boundary intensities are obtained through the coupling of the interior glass radiative transfer and the exterior furnace enclosure analysis. The model has been used to numerically study the transient conductive-radiative transfer in the advanced melting zone (AMZ) of an optic fiber drawing process. This problem is of both theoretical and practical interest in the manufacture of optical fibers. The computational method for the radiation transfer developed in this paper can also be applied to the simulation of the fiber drawing process and other glass-related manufacturing processes.

Optical fibers are drawn from preforms (fused silica glass rods) typically made up of two concentric cylinders (the core rod and the clad tube), which are usually joined in a separate fusion process. The setup time and hence manufacturing cost can be significantly reduced if the two cylinders can be joined in the same furnace in which the fiber is drawn. A good understanding of the transient temperature distribution is needed for controlling the feed rate to avoid thermally induced cracks. Since direct measurement of the temperature fields is often impossible, the geometrical design of the preform and the control of the feed rate have largely been accomplished by trials-and-errors. The ability to predict the transient temperature distribution and the thermally induced stresses will provide a rational basis to design optimization and feed rate control of the process. In this paper, we present an analytical model to predict the transient conductive-radiative transfer as two partially joined, concentric glass cylinders with specular surfaces are fed into the furnace. Finite volume method (FVM) is used to solve the radiative transfer equation (RTE). The specular surface reflectivity is obtained by the Fresnel's law and the Snell's law. The boundary intensities are obtained through the coupling of the interior glass radiative transfer and the exterior furnace enclosure analysis. The model has been used to numerically study the transient conductive-radiative transfer in the advanced melting zone (AMZ) of an optic fiber drawing process. This problem is of both theoretical and practical interest in the manufacture of optical fibers. The computational method for the radiation transfer developed in this paper can also be applied to the simulation of the fiber drawing process and other glass-related manufacturing processes. [DOI: 10.1115/1.1751426]

The paper addresses the problem of picking up moving objects from a vibratory feeder with robotic hand-eye coordination. Since the dynamics of moving targets on the vibratory feeder are highly nonlinear and often impractical to model accurately, the problem has been formulated in the context of Prey Capture with the robot as a 'pursuer' and a moving object as a passive 'prey.' A vision-based intelligent controller has been developed and implemented in the Factory-of-the-Future Kitting Cell at Georgia Tech. The controller consists of two parts: The first part, based on the principle of fuzzy logic, guides the robot to search for an object of interest and then pursue it. The second part, an open-loop estimator built upon back-propagation neural network, predicts the target's position at which the robot executes the pickup task. The feasibility of the concept and the control strategies were verified by two experiments. The first experiment evaluated the performance of the fuzzy logic controller for following the highly nonlinear motion of a moving object. The second experiment demonstrated that the neural network provides a fairly accurate location estimation for part pick up once the target is within the vicinity of the gripper.

Examination of existing joint designs for robot wrist applications has indicated that a spherical wrist motor offers a major performance advantage in trajectory planning and control as compared to the popular three-consecutive-rotational joint wrist. The tradeoff, however, is the complexity of the dynamic modeling and control. This paper presents the dynamic modeling and the control strategy of a three degree-of-freedom (DOF) variable-reluctance (VR) spherical motor which presents some attractive possibilities by combining pitch, roll, and yaw motion in a single joint. The spherical motor dynamics consist of the rotor dynamics and a torque model The torque model is described as a function of coil excitations and a permeance model in terms of the relative position between the rotor and the stator. Both the forward dynamics which determine the rotor motion as a result of activating the electromagnetic coils and the inverse model which determines the coil excitations required to generate the desired torque are derived in this paper. The solution to the forward dynamics of the spherical motor is unique, but the inverse model has many solutions and therefore an optimization is desired. Experimental results verifying the dynamic model are presented. The control of a VR spherical motor consists of two pans; namely, the control of the rotor dynamics with the actuating torque as system input, and the determination of the optimal electrical inputs for a specified actuating torque. The simulation results and implementation issues in determining the optimal control input vectors are addressed. It is expected that the resulting analysis will serve as a basis for dynamic modeling, motion control development, and design optimization of the VR spherical motor.

The cost of feeding parts to a robot for either machine loading or for assembly has been recognized as excessively expensive. The lack of a cost-effective generic part-presenter has presented the flexibility of the overall manufacturing automation to be fully exploited. For this reason, the design concept of an integrated microprocessor-controlled vision system based on retroreflective vision sensing has been developed at the Material Handling Research Center in Atlanta. Where the orientation of a part can be characterized by its silhouette, outline, or structured 'engineering landmarks,' the concept of using retroreflective materials in vision-guided part-presentation system has been proven to have significant potential for improving reliability, reducing computation, and lowering implementation cost. This paper presents optic design concepts for collocated illumination for cost effective part-presentation. The design concepts are illustrated with practical applications and experimental results. The uniformity of the image irradiance across the sensor surface, in general, depends on several factors such as the intensity distribution of the light source, the reflectance characteristics of the object and background, and the geometrical relationship between the imaging sensor, the illumination source, and the target. The trust of this paper focuses on the analytical model which characterizes the influences of these factors for optic design of retroreflection. This engineering basis is not only necessary for developing practical yet potentially cost-effective optic design concepts, but also provides a useful tool for performance prediction to drive the design for vision-guided part-presentation.

A method of modeling the radiative energy transfer, which takes place during the transient of joining two concentric, semitransparent glass cylinders, is presented. The transient temperature field is computed using both the Discrete Ordinate Method (DOM) and the widely used Rosseland's approximation.

The development of a grating interferometer with application to the angular measurement of a hard disk drive actuator arm for application to the servo-track writing process is presented. First, the theoretical background related to the linear type grating interferometer is presented, and this theory is extended to the measurement of the angular displacement of a hard disk drive actuator arm using a linear grating. A vector based diffraction technique has also been developed as a tool for visualization and analysis of the grating interferometer design. Finally, experimental setups and results from a prototype grating interferometer design are presented and discussed to demonstrate the feasibility of the grating interferometer measurement system. [DOI: 10.1115/1.1360694]

In machine vision applications, accuracy of the image far outweighs image appearance. This paper presents physically-accurate image synthesis as a flexible, practical tool for examining a large number of hardware/software configuration combinations for a wide range of parts. Synthetic images can efficiently be used to study the effects of vision system design parameters on image accuracy, providing insight into the accuracy and efficiency of image-processing algorithms in determining part location and orientation for specific applications, as well as reducing the number of hardware prototype configurations to be built and evaluated. We present results illustrating that physically accurate, rather than photo-realistic, synthesis methods are necessary to sufficiently simulate captured image gray-scale values. The usefulness of physically-accurate synthetic images in evaluating the effect of conditions in the manufacturing environment on captured images is also investigated. The prevalent factors investigated in this study are the effects of illumination, the sensor non-linearity and the finite-size pinhole on the captured image of retroreflective vision sensing and, therefore, on camera calibration was shown; if not fully understood, these effects can introduce apparent error in calibration results. While synthetic images cannot fully compensate for the real environment, they can be efficiently used to study the effects of ambient lighting and other important parameters, such as true part and environment reflectance, on image accuracy. We conclude with an evaluation of results and recommendations for improving the accuracy of the synthesis methodology.

Design for manufacturing of equipment (that handles deformable objects) and disposable medical devices (such as medical needles, optic fibers, and catheters for inserting into the human body) involves solving mechanical contact problems. Unlike rigid component manufacturing, which has been relatively well established, the handling of deformable bodies remains a challenging research. This paper offers an adaptive meshless method (MLM) for solving mechanical contact problems, which automatically insert additional nodes into large error regions identified in terms of mechanical stresses. This adaptive MLM employs a sliding line algorithm with penalty method to handle contact constraints. The method does not rely on small displacement assumptions; thus, it can solve nonlinear contact problems with large deformation. We validate the method by comparing results against those computed by using a commercial FEM software and analytical solution for two different situations, namely, large deformation and contact. Four practical applications are illustrated: large deflection of a compliant finger, mechanical contact, snap-fit assembly, and surgical needle insertion. Keywords: deformable contact, adaptive meshless method, finite element, sliding line, partition unity