bluuebunny/crossref_metadata_2025 huggingface dataset:
A Framework for Modeling and Simulation of Tracked Vehicles of High Mobility
Authors: Song Peilin , Melick Pete , Horchner James
Published: June 2012

This paper presents a modeling and simulation framework for tracked vehicles for ride comfort and load prediction analysis. The development began with the identification of the key issues such as formulations, integration schemes and contact (with friction) modeling on which the comparative studies are conducted. Based on the results of the investigations, the framework and process for the modeling and simulation of tracked vehicles are established and appropriate algorithms for contact and friction are developed. To facilitate the modeling and simulation process, a Python-based modeling environment was developed for process automation and design optimization. The developed framework has been successfully applied to the dynamic load predication of a military tracked vehicle. The parameter optimization enabled with the Python-based process automation tool helps improve the design and modification of vehicles for significantly improved fatigue life of suspension component.
Designing a Polymer Gear for Use in the Environment of an Internal Combustion Engine
Authors: Kleiss Rod , Ferfecki Frank J.
Published: June 2012

Much has been written about the advances in polymer gearing over the past few years. After fitful starts in toys and consumer products, the design and quality of these gears have improved dramatically. Materials advances over the past 20 years have been significant as well. This paper describes the methodology of designing a net shape PolyEtherEtherKetone (PEEK) injection molded gear for an automotive mass balance system. The case study referenced (ref 1) shows that, when compared to the high quality ground iron gears in the same system, a net shape injection molded PEEK polymer gear provides a 3db noise reduction, as much as 9% reduction in power consumption, a 69% mass reduction and meets the application durability requirements. The paper describes the design of the injection molded gear’s unique tooth profile, material selection, part design, mold design, and inspection methods. The paper focuses on the differences in gear design and inspection methods between injection molded gears and their metal counterparts.
Supporting Quotation Preparation by Process and Knowledge Modeling – Principles and Concepts for Automation
Authors: Elgh Fredrik
Published: June 2012

Subcontractors are commonly involved in several quotation processes and new requests for quotation are continuously received from clients. To be able to respond with feasible design solutions at competitive price, new ways of working has to be adopted, especially when it comes to quotation preparation. High levels of accuracy of the preliminary design solutions and the cost estimations generated in the quotation process are a necessity. The purpose of this work is to investigate, explore, and develop a computerized method to support quotation preparation. The main objectives are to reveal concepts and principles to support application system development and evaluate the applicability of automated quotation preparation. The results are based on experiences from a case study at a sub-supplier to the car industry. In the case study, a design automation system for quotation preparation of seat heaters was developed. The system supports the pursuit of a valid design solution and the best solution in the individual case enabling the company to respond quickly with a competitive price when receiving a new request. In this paper, principles and concepts supporting system development are introduced and the system’s applicability as a means in quotation preparation explored.
Incorporating Process Architecture in the Evaluation of Stability in Distributed Design
Authors: Devendorf Erich , Lewis Kemper
Published: June 2012

In distributed design processes, individual design subsystems have local control over design variables and seek to satisfy their own individual objectives, which may also be influenced by some system level objectives. The resulting network of coupled subsystems will either converge to a stable equilibrium, or diverge in an unstable manner. In this paper, we study the dependence of system stability on the solution process architecture. The solution process architecture describes how the design subsystems are ordered and can be either sequential, parallel, or a hybrid that incorporates both parallel and sequential elements. In this paper we demonstrate that the stability of a distributed design system does indeed depend on the solution process architecture chosen and we create a general process architecture model based on linear systems theory. The model allows the stability of equilibrium solutions to be analyzed for distributed design systems by converting any process architecture into an equivalent parallel representation. Moreover, we show that this approach can accurately predict when the equilibrium is unstable and the system divergent when previous models suggest the system is convergent.
Fast Electrostatic Force and Moment Calculations in Multibody-Based Simulations of Coarse-Grained Biopolymers
Authors: Poursina Mohammad , Laflin Jeremy , Anderson Kurt S.
Published: June 2012

In molecular simulations, the dominant portion of the computational cost is associated with force field calculations. Herein, we extend the approach used to approximate long range gravitational force and the associated moment in spacecraft dynamics to the coulomb forces present in coarse grained biopolymer simulations. We approximate the resultant force and moment for long-range particle-body and body-body interactions due to the electrostatic force field. The resultant moment approximated here is due to the fact that the net force does not necessarily act through the center of mass of the body (pseudoatom). This moment is considered in multibody-based coarse grain simulations while neglected in bead models which use particle dynamics to address the dynamics of the system. A novel binary divide and conquer algorithm (BDCA) is presented to implement the force field approximation. The proposed algorithm is implemented by considering each rigid/flexible domain as a node of the leaf level of the binary tree. This substructuring strategy is well suited to coarse grain simulations of chain biopolymers using an articulated multibody approach.
Quantifying the Convergence Time of Distributed Design Processes
Authors: Devendorf Erich , Lewis Kemper
Published: June 2012

Time is an asset of critical importance in the design process and it is desirable to reduce the amount of time spent developing products and systems. Design is an iterative activity and a significant portion of time spent in the product development process is consumed by design engineers iterating towards a mutually acceptable solution. Therefore, the amount of time necessary to complete a design can be shortened by reducing the time required for design iterations or by reducing the number of iterations. The focus of this paper is on reducing the number of iterations required to converge to a mutually acceptable solution in distributed design processes. In distributed design, large systems are decomposed into smaller, coupled design problems where individual designers have control over local design decisions and seek to satisfy their own individual objectives. The number of iterations required to reach equilibrium solutions in distributed design processes can vary depending on the starting location and the chosen process architecture. We investigate the influence of process architecture on the convergence behavior of distributed design systems. This investigation leverages concepts from game theory, classical controls and discrete systems theory to develop a transient response model. As a result, we are able to evaluate process architectures without carrying out any solution iterations.
Object-Oriented Modeling of Industrial Manipulators With Application to Energy Optimal Trajectory Scaling
Authors: Pellicciari Marcello , Berselli Giovanni , Leali Francesco , Vergnano Alberto , Lennartson Bengt
Published: June 2012

The development of safe, energy efficient mechatronic systems is currently changing standard paradigms in the design and control of industrial manipulators. In particular, most optimization strategies require the improvement or the substitution of different system components. On the other hand, from an industry point of view, it would be desirable to develop energy saving methods applicable also to established manufacturing systems being liable of small possibilities for adjustments. Within this scenario, an engineering method is reported for optimizing the energy consumption of serial manipulators for a given operation. An object-oriented modeling technique, based on bond graph, is used to derive the robot electromechanical dynamics. The system power flow is then highlighted and parameterized as a function of the total execution times. Finally, a case study is reported showing the possibility to reduce the operation energy consumption when allowed by scheduling or manufacturing constraints.
An Improved Risk Based Design Method Based on a Novel Upper Bound Formulation
Authors: Golbayani Hami , Kazerounian Kazem
Published: June 2012

In this work, a novel framework is proposed for the risk based design optimization of engineering systems by minimizing the demand on the system components’ accuracy (which directly relates to their cost). The fundamental development of this work is an analytical upper bound for calculating the probability of failure. This is in contrast with First Order Reliability Method (FORM), where a lower bound is used in calculating the probability of failure. FORM is one of the most popular methods for reliability analysis of engineering systems. In this paper, we show that FORM results in an optimistic measure of risk, hence potentially catastrophic in engineering design. A more accurate measure of failure is proposed by utilizing an analytical upper bound for the distribution of reliability index (the length of the most probable point vector to origin). This distribution is a function of the eigenvalues of the linearized limit state function in the normal space which results in a better understanding of failure phenomenon. The proposed formulation is computationally efficient and straightforward to solve, since it only involves finding eigenvalues in each iteration. This algorithm is applicable to any linearizable continuous limit state function with any type of distribution for the design variables. The method is applied to two examples and its accuracy is compared with the Monte Carlo simulation and FORM, demonstrating its effectiveness and value.
Horizontal Pendulum With Sudden Changes in Platform Tilt
Authors: McGehee Clark C. , Ballard Zach C. , Mann Brian P.
Published: June 2012

The equations of motion for a horizontal pendulum mounted to a rocking platform are developed. Equilibrium conditions are found as a function of the platform tilt angle. The equations are transformed to describe motion about the shifting equilibrium point, and an approximation for the amplitude and phase correction of the solution is developed using the method of averaging. This approximation is used to construct an iterative map that describes the pendulum angle and rotational velocity between each instance of platform rocking. Approximate analytical solutions are compared to numerical and experimental results, and ongoing work is discussed.
Characterizing the Effect of Domain Distance in Design-by-Analogy
Authors: Lopez Ricardo , Linsey Julie S. , Smith Steven M.
Published: June 2012

Design-by-analogy is a powerful tool to generate novel ideas. The present work explores the use of distant-domain analogies. Analogies from distant domains have a greater potential to lead to innovative solutions. This study hypothesizes that distant domain analogies lead to more abstraction resulting in more creative designs. This was evaluated with a between-subjects experiment where 17 engineering students were presented a predetermined set of analogues then asked to solve a design problem. The analogues contained two sets of analogies: one from the problem domain and one from a domain of varying distance. It was observed that although designers deemed analogies from more distant domains as ‘less useful’ and solutions generated using more distant domains ‘less effective’ and ‘less practical’, an analysis of participant’s solutions found distant domains to be at least as useful as close domains. These trends warrant future experimentation with an increased sample size.
Towards a Tool for Characterizing the Progression of Academic Research
Authors: Leong Ming , Bazoune Abdelaziz , Wallace David R. , Tang Victor , Seering Warren P.
Published: June 2012

The importance of process in successful and effective technology and product development is widely recognized in industry. Tools, such as technology readiness levels (TRLs) and various metrics, have been developed and successfully used to guide and strategically plan R&D processes, allocate resources, and calibrate expectations. Similarly, one might hypothesize that academic research might also benefit from similar tools that would assist both researchers and funding organizations. A research assessment tool should: 1) facilitate planning and communication; 2) effectively gauge progress; and 3) accommodate and capture the diverse scope of academic research. However, the inherent open-endedness and exploratory nature of research makes it difficult to concretely characterize research progress. This paper begins to develop an academic research measurement tool. The proposed Research Maturity Levels (RMLs) tool divides research activities into four main components: 1) background knowledge, 2) problem and question formulation, 3) procedures and results, and 4) resources. Within each component, the RMLs guides researchers through a process of increasing maturity levels. Additionally, each component includes mechanisms to formalize iterations and “eureka” moments—when directions and plans may change based upon new knowledge. Preliminary evaluation suggests that the tool has promise as a comprehensive measurement tool. It is hoped that this work will result in a tool that can facilitate planning, help to measure and communicate research progress, and encompass the diverse scope of academic research goals.
Kinematic Optimization of a Robotic Joint With Continuously Variable Transmission Ratio
Authors: Grenier Martin , Gosselin Cle´ment
Published: June 2012

The range of possible tasks achievable by robots highly depends on the selection of motors and transmissions. For example, variable ratio transmissions surpass single ratio transmissions because they can modify the torque-speed parameters of the actuator and, therefore, maintain the optimal power output state from the motor. Consequently, the use of variable ratio transmissions may expand a robot’s achievable tasks. A robotic joint with continuously variable transmission ratio is presented in this paper. This new type of transmission joint may be used in serial or parallel robots. The transmission consists of a doubly actuated two-degree-of-freedom five-bar parallel mechanism. The main actuator is located at the input revolute joint. The variation of the ratio is achieved with the adjustment actuator located at a second revolute joint. Such a transmission, based on a linkage, may have unde-sired ratio variations for a constant adjustement joint position. Therefore, two different optimization methods are presented to determine the best geometric parameters in order to minimize the undesired ratio variation while maximizing the possible transmission ratio range. The performance indices are either optimal for the entire range or only for the maximum and minimum ratios available. A simulation is presented with the best parameters obtained with the optimization based on the maximum and minimum ratios. Results show a transmission ratio ranging from 0.9:1 to 4.5:1 with a minimal amplification of 3.9:1. The transmission ratio may vary continuously within the working boundaries. The output range of motion may be adapted to a serial robot joint.
Investigations on a Nonlinear Energy Harvesting System Consisting of a Flapping Foil and an Electro-Magnetic Generator Using Power Flow Analysis
Authors: Yang J. , Xiong Y. P. , Xing J. T.
Published: June 2012

A nonlinear energy harvesting system consisting of a flapping foil and an electro-magnetic generator excited by incompressible quasi-steady air flows is investigated. Due to stiffness nonlinearities in pitch and/or heave degrees of freedom, the system behaves a stable limit cycle oscillation when flow velocity exceeds the critical flutter speed, so that the mechanical energy imported from air flow is converted into electricity by the coupled electro-magnetic generator. The power flow equations and variables, including the input, dissipated, transmitted and harnessed powers, of the system are formulated. A fourth-order Runge-Kutta method is used to obtain the system’s dynamical response as well as power flow variables. It shows that increasing the nonlinear stiffness in heave motion or decreasing in pitch motion benefits power generation. The research demonstrates the capability of this nonlinear system to harvest natural energy without extra operation cost. Discussions and planed further research works are given for engineering applications.
Using GPU-Based Computing to Solve Large Sparse Systems of Linear Equations
Authors: Carrigan Travis J. , Watt Jacob , Dennis Brian H.
Published: June 2012

Often thought of as tools for image rendering or data visualization, graphics processing units (GPU) are becoming increasingly popular in the areas of scientific computing due to their low cost massively parallel architecture. With the introduction of CUDA C by NVIDIA and CUDA enabled GPUs, the ability to perform general purpose computations without the need to utilize shading languages is now possible. One such application that benefits from the capabilities provided by NVIDIA hardware is computational continuum mechanics (CCM). The need to solve sparse linear systems of equations is common in CCM when partial differential equations are discretized. Often these systems are solved iteratively using domain decomposition among distributed processors working in parallel. In this paper we explore the benefits of using GPUs to improve the performance of sparse matrix operations, more specifically, sparse matrix-vector multiplication. Our approach does not require domain decomposition, so it is simpler than corresponding implementation for distributed memory parallel computers. We demonstrate that for matrices produced from finite element discretizations on unstructured meshes, the performance of the matrix-vector multiplication operation is just under 13 times faster than when run serially on an Intel i5 system. Furthermore, we show that when used in conjunction with the biconjugate gradient stabilized method (BiCGSTAB), a gradient based iterative linear solver, the method is over 13 times faster than the serially executed C equivalent. And lastly, we emphasize the application of such method for solving Poisson’s equation using the Galerkin finite element method, and demonstrate over 10.5 times higher performance on the GPU when compared with the Intel i5 system.
A Customization Approach for Design Using Commercially Available Laminated Composite Materials
Authors: Nandi Soumitra , Siddique Zahed , Altan Cengiz
Published: June 2012

Composite materials can offer wide range of thermo-mechanical properties when designing load bearing components using them. The wide range of properties can be obtained by varying fiber-matrix volumetric ratio. Another advantage of using composite materials in design is that the directional properties of laminated composite materials can be easily manipulated by varying the angle of orientation with respect to the direction of the load. Theoretically it is possible to design composite laminates with any fiber-matrix ratio, and in any orientation. But in practice, only a selective number of laminates with given fiber volume fraction are produced and sold by the companies depending on their market demands. So, it is necessary for a designer to perform the selection of laminates from a list of available composite laminates to make it commercially viable. The manual selection process of composite laminates can be very cumbersome for the designers when multiple design goals need to be satisfied in the load bearing component that is being designed. This paper presents a new customization approach for design of load bearing components where appropriate unidirectional laminated composites can be selected to satisfy multiple property requirements. In this approach, a laminate customization technique is incorporated with a grammatical method that deals with a shape design technique, and loading analysis for the designed shape. A hip-replacement joint is designed using commercially available composite laminates to illustrate the approach.
Preliminary Design Considerations on Epicyclic Gears in Aircraft High-Lift Systems
Authors: Wang Anngwo , El-Bayoumy Lotfi , Venables Neil
Published: June 2012

Simple and compound planetary gears are extensively used on aircraft high lift applications, which include leading edge and trailing edge actuators. These gears are usually highly loaded and compact in size. Preliminary design considerations that have far-reaching effects on actuator sizing are discussed herein. These include the selection of actuators, the arrangement of planets, the counting of tooth hits, the effect of synchronization or non-synchronization, the instantaneous efficiency, and the ease of assembly.
A Method for Evaluating Manufacturing Change in Engineering Design
Authors: Brooks Christopher , Mocko Gregory M.
Published: June 2012

This paper details a method of change prediction that builds upon the traditional component-component design structure matrix by incorporating manufacturing costs and modeling higher orders of coupling. A coupling index is also created to assess the level of coupling between interfaced features. A BMW X5 headliner assembly and a Ryobi hand-held drill are analyzed using the proposed method to identify the features and components that offer the greatest ease of change. The analysis of the BMW X5 headliner shows that the rectangular slots on the bottom of the adapter plates are the feature that offers the greatest ease of change, while the handles are the component that offers the greatest ease of change. For the Ryobi drill, the battery is identified as the component that offers the greatest ease of change. The proposed method of change prediction proves to be an effective and efficient means of modeling change propagation and assessing change impact.
On Nonlinear Control of Optical Traps Using Pulling Trajectory Tracking for Single-Molecule Experiments
Authors: Cole Daniel G.
Published: June 2012

This article explores nonlinear position plus integral (PI) feedback for controlling an optical trap used in single-molecule experiments. In general, nonlinearities in the spatial dependence of the optical force complicate feedback control for optical traps. Furthermore, the extension of a molecule creates an additional feedback path that puts constraints on the PI control gains. The nonlinear PI control presented here is shown to provide all of the benefits of integral control: disturbance rejection, servo tracking, and force estimation. The ability of nonlinear PI control to lower the measurement SNR is evaluated. Finally, constraints on the pulling rate are given to ensure the system trajectory remains in a quasi-static condition, stable, and the bead remains held in the trap.
Application of the Complex Variable Semi-Analytic Method to the Inverse Determination of Unknown Material Properties
Authors: Jin Weiya , Dennis Brian H.
Published: June 2012

There are various engineering applications where it is desired to determine material properties. For example, properties are needed in the development of new functional and composite materials, in non-destructive testing for quality control in manufacturing, and for real-time structural health monitoring. Often it is not possible to measure these properties directly without damaging the samples. However, many properties can be determined inversely using measurements of the sample response to a loading of some type. In this paper, we demonstrate the inverse determination of spatially varying material properties using simulated measurements, finite element modeling, and numerical optimization methods. We consider problems in both heat conduction and linear elasticity. We consider cases where measurements on the interior and boundary are used. The accuracy and efficiency of the inversely determined solution is improved by using accurate sensitivity information provided by the Complex Variable Semi-Analytic Method. The sensitivities also give guidance as to where measurements should be taken on the structure to obtain accurate estimations of the material properties.
Investigation of the Internal Resonance and Regenerative Chatter Dynamics in Nonlinear Milling Process
Authors: Moradi Hamed , Movahhedy Mohammad R. , Vossoughi Gholamreza , Ahmadian Mohammad T.
Published: June 2012

Peripheral milling is extensively used in manufacturing industry. To achieve more material removal rate, high precision and surface quality and increase tool life, chatter vibration must be suppressed. In this paper, an extended dynamic model of the peripheral milling process including both the structural nonlinearity and nonlinear cutting forces is presented. Using the multiple-scale approach, as a perturbation technique, internal resonance of the milling process is investigated. Transfer of the energy between the coupled x-y modes is studied. According to results obtained, it is possible to adjust the rate at which the x-mode (or y-mode) decays by implementation of the internal resonance (arisen from the coupled dynamics of x-y modes with a cubic nonlinearity). Similar to the internal resonance case, it is shown that under regenerative chatter with specific machining conditions, one mode can decay. Therefore, under both internal resonance and regenerative chatter conditions, it is possible to suppress the undesirable vibration of the mode (direction) in which more accurate surface finish is required.
The Dynamic Simulation and Analysis of a Cycloidal Speed Reducer
Authors: Thube Sandeep V. , Bobak Todd R.
Published: June 2012

In industry, digital prototyping has become a valuable tool for the design and subsequent analysis of components for a proposed design. Prior to its maturation as a design tool, it was common to go through repeated physical iterations of a given design to assess form, fit and function. Investments in design time, prototype procurement and subsequent testing yielded long term product incubation periods from initial concept to final production. Current design modeling software allows for part design, unit assembly, loading and dynamic simulation of a component electronically — all without the procurement of a physical prototype. The results from such dynamic simulation can then be analyzed through finite element analysis to assess component functionality in its intended operational environment with an eye towards design optimization. From the perspective of gear design, digital prototyping certainly affords the same advantages as has been described. Indeed, it is common to find electronic examples of 3D gearset with motion and loading condition imposed on them. It is less common, however, to find similar dynamic examples of the operation of a cycloidal type speed reducer where the kinematics of the reduction mechanism is completely different from that of the traditional involute gearing. This paper will explore a method of dynamically simulating a cycloidal type speed reducer where the generated internal loads will be used to assess the stresses acting on the one of the major reduction components contained within — namely, the cycloid disc.
Kinematic Synthesis of Planar, Shape-Changing Rigid-Body Mechanisms With Prismatic Joints
Authors: Zhao Kai , Schmiedeler James P. , Murray Andrew P.
Published: June 2012

This paper presents a procedure to synthesize planar rigid-body mechanisms, containing both prismatic and revolute joints, capable of approximating a shape change defined by a set of morphing curves in different positions. With the introduction of prismatic joints, the existing mechanization process needs to be revisited via a building-block approach. The basic block is the Assur group of class II, and the auxiliary block is a fourbar mechanism, crank slider or binary link. To approximate shape changes defined by both open and closed curves, a single degree-of-freedom (DOF) mechanism is generated by assembling these building blocks. In the case of a large number of morphing curves, a weighted least squares approach is applied to determine center point locations for revolute joints and sliding paths for prismatic joints in individual building blocks. Then, the building blocks are located in an assembly position to regenerate the morphing chain using a numerical optimization method. Because of the additional constraints associated with prismatic joints compared to revolute joints, the size of the solution space is reduced, so random searches of the design space to find solution mechanisms are ineffective. A genetic algorithm is employed here instead to find a group of viable designs within reasonable computational limits. The procedure is demonstrated with synthesis examples of two 1-DOF mechanisms, one approximating five open-curve profiles and the other four closed-curve profiles.
Co-Design of an Active Suspension Using Simultaneous Dynamic Optimization
Authors: Allison James T. , Han Zhi
Published: June 2012

Design of physical systems and associated control systems are coupled tasks; design methods that manage this interaction explicitly can produce system-optimal designs, whereas conventional sequential processes may not. Here we explore a new technique for combined physical system and control design (co-design) based on a simultaneous dynamic optimization approach known as direct transcription, which transforms infinite-dimensional control design problems into finite dimensional nonlinear programming problems. While direct transcription problem dimension is often large, sparse problem structures and fine-grained parallelism (among other advantageous properties) can be exploited to yield computationally efficient implementations. Extension of direct transcription to co-design gives rise to a new problem structures and new challenges. Here we illustrate direct transcription for co-design using a new automotive active suspension design example developed specifically for testing co-design methods. This example builds on prior active suspension problems by incorporating a more realistic physical design component that includes independent design variables and a broad set of physical design constraints, while maintaining linearity of the associated differential equations.
On the Impedance of Statically-Balanced Mechanisms
Authors: Lu Qi , Xiu Wenwu , Ma Ou
Published: June 2012

Statically-balanced technology is often used to compensate partial or full gravity force exerting on a mechanism in order to reduce the effort of driving the mechanism. Since such compensation is static, when a statically-balanced mechanism is used for dynamic applications, it will still have impedance (mechanical resistance to input motion) because the mechanism still subjects to the inertia forces although the gravity force has been compensated. Such a dynamic effect is undesirable for many applications, especially for those required to physically interact with humans and hence, the impedance property needs to be fully understood and possibly minimized in the design and/or operation of a statically-balanced mechanism. This paper studies the impedance property of passive statically-balanced mechanisms. Based on the study result, optimization strategies are proposed in order to optimize the operation of a statically-balanced mechanism. The strategies are then applied to a spring-based reduced-gravity simulation mechanism to figure out an optimal set of configurations in the workspace where the mechanism has the lowest impedance and the highest zero-gravity simulation fidelity.
Design of a Drive Mechanism for a Rectilinear-Gait Based Snake-Inspired Robot
Authors: Hopkins James K. , Gupta Satyandra K.
Published: June 2012

Snake-inspired locomotion is much more maneuverable compared to conventional locomotion concepts and it enables a robot to navigate through rough terrain. A rectilinear gait is quite flexible and has the following benefits: functionality on a wide variety of terrains, enables a highly stable robot platform, and provides pure undulatory motion without passive wheels. These benefits make rectilinear gaits especially suitable for search and rescue applications. However, many previous robot designs utilizing rectilinear gaits were slow in speed. In this paper, a snake-inspired robot design and rectilinear gait capable of high speed locomotion are introduced. Our results from an initial prototype indicate that this concept is capable of achieving high speed. The developed prototype successfully demonstrated forward and turning motion.
Modeling and Design of a Linkage-Based Suspension for Tracked-Type Climbing Mobile Robotic Systems
Authors: Kumar Padmanabhan , Hill Tristan W. , Bryant D. Andrew , Canfield Stephen L.
Published: June 2012

Skid steer tracked-based robots are popular due to their mechanical simplicity, zero-turning radius and greater traction. This architecture also has several advantages when employed by mobile platforms designed to climb and navigate ferrous surfaces, such as increased magnet density and low profile (center of gravity). However, the suspension design plays a critical and unique role in track-based climbing systems relative to their traditional counterparts. In particular, the suspension must both accommodate irregularities in the climbing surface as well as transfer forces to the robot chassis required to maintain equilibrium. Furthermore, when properly designed, the suspension will distribute the climbing forces in a prescribed manner over the tractive elements. This paper will present a model for analysis and design of a linkage-type suspension for track-based climbing robot systems. The paper will further propose a set of requirements termed “conditions of climbing” that must be met to ensure stable (no falling) climbing for a given robot design over a range of climbing surface geometries. A recursive strategy is proposed to implement these conditions and yield a factor of safety in the current climbing state. This model will be compared through empirical testing with several prototype climbing robot systems. A method will also be demonstrated to use this model in the design of a preferred suspension system.
Identification of Mass Distribution of Nominally Identical Microresonator Arrays in the Presence of Measurement Noise
Authors: Ryan Teresa J. , Judge John A. , Vignola Joseph F.
Published: June 2012

The use of micro- and nanoscale mechanical resonators for mass detection is a maturing concept. Recently, researchers have begun to consider coupled arrays of resonators and the notion of examining system eigenmodes as well as resonant frequencies to extract information about the system. This paper describes a method for the use of measured eigenmodes of a linear chain of nominally identical oscillators to identify the masses of the individual oscillators. This allows characterization of initial mass variation as well as changes due to the presence of one or more target analytes. This work uses numerical simulation to explore the sensitivity of this method to measurement noise. Mass identification is shown to be more accurate on oscillators with significant vibration amplitude in a given eigenmode. We discuss various averaging techniques for combining results from multiple eigenmodes to reduce sensitivity to noise.
Runner Optimization for In-Mold Assembly of Multi-Material Compliant Mechanisms
Authors: Bejgerowski Wojciech , Gupta Satyandra K.
Published: June 2012

The runner system in injection molding process is used to supply the polymer melt from injection nozzle to the gates of final part cavities. Realizing complex multi-material mechanisms by in-mold assembly process requires special runner layout design considerations due to the existence of the first stage components. This paper presents the development of an optimization approach for runner systems in the in-mold assembly of multi-material compliant mechanisms. First, the issues specific to the in-mold assembly process are identified and analyzed. Second, the general optimization problem is formulated by identification of all parameters, design variables, objective functions and constraints. Third, the implementation of the optimization problem in Matlab® environment is described based on a case study of a runner system for an in-mold assembly of a MAV drive mechanism. This multi-material compliant mechanism consists of seven rigid links interconnected by six compliant hinges. Finally, several optimization approaches are analyzed to study their performance in solving the formulated problem. The most appropriate optimization approach is selected. The case study showed the applicability of the developed optimization approach to runner systems for complex in-mold assembled multi-material mechanism designs.
Optimal Scheduling of Parabolic Heliostats Aim Targets in a Mini-Tower Solar Concentrator System
Authors: Hamza Karim , Gandhi Umesh , Saitou Kazuhiro
Published: June 2012

Solar tower with heliostat mirrors is an established technology for utility-scale solar energy harvesting. The setup has several advantages such as the capability to reach high temperature, modularity and ease of maintenance of the heliostats, containment of the high temperature zone, as well as overall low cost per harvested energy. Downscaling to medium and small scale applications is a desirable goal in order to attract more users of the technology. However, the downscaling often does not turn out economically feasible while using flat mirror heliostats, which are the norm in utility-scale systems. This is mainly due to the need to preserve the number (typically several hundred) of mirrors in order to maintain the solar concentration ratio. Use of parabolic mirrors instead can significantly reduce the required number of mirrors for smaller scale systems, but comes with new challenges. Unlike flat mirrors, the effective focal length of parabolic mirrors changes with the incidence angle causing undesirable variations in the concentration ratio and/or flux distribution at the receiver. To overcome this issue, we propose adjustment of the aim targets of the heliostat mirrors. Instead of aiming at the center of the receiver, aim targets are set as design variables and optimized to reduce undesirable peaks in the flux distribution. A special implementation of genetic algorithm is developed and applied to a case study of a nominal 10kW solar concentrator. Results of the study show significant improvement in flux distribution.
VR-SMART: A Virtual Reality System for Smart Home Environments
Authors: Darnall Nathan D. , Mishra Vinay , Jayaram Sankar , Jayaram Uma
Published: June 2012

Virtual reality (VR) technologies and systems have the potential to play a key role in assisting disabled inhabitants of smart home environments with instrumental activities of daily living (IADLs). While immersive environments have useful applications in the fields of gaming, simulation, and manufacturing, their capabilities have been largely untapped in smart home environments. We have developed an integrated CAD and virtual reality system which assists a smart home resident in locating and navigating to objects in the home. Using the methods presented in this paper, a room modeled in a CAD system is imported into a virtual environment, which is linked to an audio query-response interface. The user’s head and room objects are fitted with the sensors which are part of a six DOF motion tracking system. Methods have been created to allow the inhabitant to move objects around in the room and then later issue an audio query for the location of the object. The system generates an audio response with the object’s position relative to the person’s current position and orientation. As he approaches the object, information is derived from the virtual models of both the room and the objects within the room to provide better guidance. The ability of the VR-SMART system to guide a resident to an object was tested by mounting a head mounted display (HMD) on a user located in a room. This allowed the user to navigate through the virtual world that simulated the room he occupied, thereby providing a way to test the positional accuracy of the virtual system. Results of the testing in the immersive environment showed that although the overall system shows promise at a 30% success rate, the success of the system depends on the accuracy and calibration of the tracking system. In order to improve the success of the system, we explored the precision of a second motion capture system, with more accurate results. Results confirmed that the VR-SMART system could significantly improve the assistance of disabled people in finding objects easily in the room when implemented only as an assistive system without the head-mounted display.
Towards Physics-Based Interactive Design for Manufacturing of Cast Parts Using Smoothed Particle Hydrodynamics on GPUs
Authors: Komarov Ivan , Alberts Samuel T. , D’Souza Roshan M.
Published: June 2012

The current state-of-the art interactive Design for Manufacturing (DFM) for casting is limited to checking designs for correct draft angles and undercuts. DFM for mold filling is limited to finding thin sections in the part. Efforts towards developing an interactive physics-based DFM tool to check design for mold fillability at the detailed design stage are described in this paper. The presented approach incorporates a numerical simulation of the flow of the melt into part geometry. The Smoothed Particle Hydrodynamics (SPH) method, a mesh-free, particle-based, technique, is used to handle free-surface flows. The highly parallel nature of discrete particle methods makes SPH an excellent candidate for optimization through parallelization. Novel algorithms and data-structures for executing SPH methods on graphics processing units (GPUs) were designed. The presented preliminary implementation, which executes on a consumer GPU, achieves a 30× speedup over a serial implementation on a high end CPU. With further algorithmic optimizations, and given the rapid growth in computing capabilities of GPUs, the authors believe the novel method reported here will provide interactive DFM for mold filling within the next 2 to 3 years.
DEXML: A First Step Toward a UML Based Implementation Framework for PLCS
Authors: Krima Sylvere , Bertucat Roch , Lubell Joshua , Rachuri Sudarsan , Foufou Sebti
Published: June 2012

Data exchange specifications not only must be broad and general to achieve acceptance, but also must be customizable in a controlled and interoperable manner to be useful. The Product Life Cycle Support (PLCS) suite of data exchange specifications (known as DEXs) uses templates to enable controlled customizability without sacrificing breadth or interoperability. DEXs are business context-specific subsets of ISO 10303 Application Protocol (AP) 239, subject to additional constraints imposed by the templates. A PLCS template defines how AP239 entities and their attributes will be instantiated using an externally-defined controlled vocabulary defined in a Reference Data Library. Template instantiations are defined using an Instantiation Path (IP) specified using an arcane syntax that must be manually written by the template developer. The PLCS information model is formally defined in the ISO 10303 EXPRESS language, but there is no formalism used at the template level. A challenge for newcomers to PLCS is to dive into and understand all the bespoken, non-standardized and PLCS-specific technologies (domain-specific languages and software) used to develop and implement the templates. DEXML presents an approach based on the Unified Modeling Language (UML) enabling the use of mainstream software and technologies to develop and implement DEXs, reducing the need for nonstandard and unfamiliar languages and tools.
Nonlinear Dynamics of an Imperfect Microbeam Under an Axial Load and Electric Excitation
Authors: Ruzziconi Laura , Younis Mohammad I. , Lenci Stefano
Published: June 2012

This study is motivated by the growing attention, both from a practical and a theoretical point of view, toward the nonlinear behavior of microelectromechanical systems (MEMS). We analyze the nonlinear dynamics of an imperfect microbeam under an axial force and electric excitation. The imperfection of the microbeam, typically due to microfabrication processes, is simulated assuming the microbeam to be of a shallow arched initial shape. The device has a bistable static behavior. The aim is that of illustrating the nonlinear phenomena, which arise due to the coupling of mechanical and electrical nonlinearities, and discussing their usefulness for the engineering design of the microstructure. We derive a single-mode-reduced-order model by combining the classical Galerkin technique and the Pade´ approximation. Despite its apparent simplicity, this model is able to capture the main features of the complex dynamics of the device. Extensive numerical simulations are performed using frequency response diagrams, attractor-basins phase portraits, and frequency-dynamic voltage behavior charts. We investigate the overall scenario, up to the inevitable escape, obtaining the theoretical boundaries of appearance and disappearance of the main attractors. The main features of the nonlinear dynamics are discussed, stressing their existence and their practical relevance. We focus on the coexistence of robust attractors, which leads to a considerable versatility of behavior. This is a very attractive feature in MEMS applications. The ranges of coexistence are analyzed in detail, remarkably at high values of the dynamic excitation, where the penetration of the escape (dynamic pull-in) inside the double well may prevent the safe jump between the attractors.
Hybrid Power Generation System Design Optimization Based on a Markovian Reliability Analysis Approach
Authors: Lu Shen , Kim Harrison M.
Published: June 2012

The optimal design of hybrid power generation systems (HPGS) can significantly improve the economic and technical performance of power supply. Due to the intermittent nature of renewable energy sources, as well as the application of energy storage techniques, the efficacy and efficiency of reliability assessment have become vital for successful HPGS design optimization. This paper proposes a sizing optimization method for HPGS based on a Markovian approach for long term reliability assessment. A multi-scenario formulation is considered to minimize the system cost while guaranteeing acceptable reliability across all the representative scenarios. The presented reliability analysis approach employs a Markov chain to model the state of charge of the energy storage based on probabilistic resource and load models. With this treatment, the loss of load probability of the HPGS can be tracked with relatively low computation, making it suitable for optimization applications. The effectiveness of the reliability analysis approach is tested through a comparison with Monte Carlo simulation; then the optimization approach is demonstrated with a numerical case study.