J. Mech. Des. 2009;131(11):110201-110201-1. doi:10.1115/1.4000256.

There is an ASME Journal submission type that is frequently a subject of misunderstanding and occasionally a source of ill feelings in authors: the Technical Note or Technical Brief. A note or brief is almost always a shorter contribution than the “full” research paper, and therefore less worthy by implication. I will argue here that this implication is just not true.

Commentary by Dr. Valentin Fuster

Research Papers

J. Mech. Des. 2009;131(11):111001-111001-12. doi:10.1115/1.3149848.

We present a framework for the design of a compliant system, i.e., the concurrent design of a compliant mechanism with embedded actuators and sensors. Our methods simultaneously synthesize optimal structural topology and component placement for maximum energy efficiency and adaptive performance, while satisfying various weight and performance constraints. The goal of this research is to lay an algorithmic framework for distributed actuation and sensing within a compliant active structure. Key features of the methodology include (1) the simultaneous optimization of the location, orientation, and size of actuators (and sensors) concurrent with the compliant transmission topology, and (2) the implementation of controllability and observability concepts (both arising from consideration of control) in compliant systems design. The methods used include genetic algorithms, graph searches for connectivity, and multiple load cases implemented with linear finite element analysis. Actuators, modeled as both force generators and structural compliant elements, are included as topology variables in the optimization. The results from the controllability problem are used to motivate and describe the analogous extension to observability for sensing. Results are provided for several studies, including (1) concurrent actuator placement and topology design for a compliant amplifier, (2) a shape-morphing aircraft wing demonstration with three controlled output nodes, and (3) a load-distribution sensing wing structure with internal sensors. Central to this method is the concept of structure/component orthogonality, which refers to the unique system response for each component (actuator or sensor) it contains.

Topics: Actuators , Design , Stress , Sensors
Commentary by Dr. Valentin Fuster
J. Mech. Des. 2009;131(11):111002-111002-11. doi:10.1115/1.3179145.

The authors present an optimization procedure in designing infinitely variable transmission architectures, which allows them to achieve a significant reduction in power recirculation and, hence, an increase in mechanical efficiency. The focus of this paper is on infinitely variable transmissions used in off-highway vehicles and, in particular, on input and output coupled architectures. The optimized solutions have been analyzed in depth, with particular attention to the power flowing through the infinitely variable unit, which strongly influences the overall efficiency of the transmission. The major result of this study is that the so far neglected output coupled solution, if properly optimized, guarantees very good performance over the entire range of vehicle speed. The analysis then shows that the particular choice of either input or output coupled architecture by itself, or of a mixed solution, strictly depends on the specific application under consideration and that none of them should be discarded a priori.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2009;131(11):111003-111003-8. doi:10.1115/1.3179150.

Complete dynamic balancing principles still cannot avoid a substantial increase in mass and inertia. In addition, the conditions for dynamic balance and inertia equations can be complicated to derive. This article shows how a double pendulum, which is fully dynamically balanced using counter-rotary countermasses (CRCMs) for reduced additional mass and inertia, can be used as a building element in the synthesis of dynamically balanced mechanisms. It is also shown that for these mechanisms, the balancing conditions and inertia equations can be derived quickly. For constrained mechanisms, the procedure is to first write down the known balancing conditions and inertia equations for the balanced double pendula and subsequently substitute the kinematic relations. In addition, new CRCM configurations were derived that have low inertia, a single CRCM, or all CRCMs near the base.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2009;131(11):111004-111004-9. doi:10.1115/1.3184693.

This paper describes a study to understand the use of analogies by design engineers with different levels of experience in an adaptive design domain. Protocol analyses of 12 design engineers have been analyzed to understand the functions and reasoning of the analogies. The protocols are real-world data from the aerospace industry. The findings indicate a significant difference in both the use of analogies by novices and experienced designers and the reasoning from the analogies. Novices were found to predominantly transfer information related to the geometric properties without explicit reference to relevant design issues or to the appropriateness of applying the analogy, whereas experienced designers tended to use analogies for problem solving and problem identification. Experienced designers were found to use the analogy to reason about the function of a component and the predicted behavior of the component, whereas the novices seem to lack such reasoning processes.

Topics: Design , Functions , Engineers
Commentary by Dr. Valentin Fuster
J. Mech. Des. 2009;131(11):111005-111005-13. doi:10.1115/1.3201968.

Design recovery is defined as determining the relevant form and functions and their relationships for a component in order to generate a complete engineering representation. To lead to a more complete model, an integrated approach that assesses the component from different perspectives is presented here, as no one perspective or set of tools can provide a comprehensive engineering representation. There is always the potential for error; hence, the necessity to assess latent design and/or design recovery issues in rigorous manner. A modified failure modes and effects analysis (FMEA) was developed to provide a foundation for the reconstructed model’s design validation. The modified FMEA is designed to interface directly with the design recovery framework. A matrix based procedure, which considers feature functions and relationships, is developed to assist the designer to quickly assess the feature design using a consistent structured approach. The results are plotted, and subsequent testing strategies are suggested based on the characteristics of the features being assessed. Examples illustrate the proposed methodologies and highlight their merits.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2009;131(11):111006-111006-9. doi:10.1115/1.3213529.

In real-world applications, a nominal model is usually used to approximate the practical system for design and control. This approximation may make the traditional robust design less effective because the model uncertainty still affects the system performance. In this paper, a novel robust design approach is proposed to improve the system robustness to the variations in design variables as well as the model uncertainty. The proposed robust design consists of two separate optimizations. One is to minimize the variation effects of the design variables to the performance based on the nominal model just as what the traditional deterministic robust design methods do. The other is to minimize the effect of the model uncertainty using the matrix perturbation theory. Through solving a multi-objective optimization problem, the proposed design can improve the system robustness to the uncertainty. Simulation examples have demonstrated the effectiveness of the proposed design method.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2009;131(11):111007-111007-8. doi:10.1115/1.4000238.

The failure due to accidental drop of magnetic recording disks made of brittle or ductile materials is of great interest in the design of small form factor hard disk drives. In this study, fracture of glass disks (brittle material) and plastic deformation of aluminum disks (ductile material) at very high shock levels caused by accidental drop are investigated using finite element analysis. It is found that failure inception for both disk types occurs at the inside perimeter of the disk. For glass disks, cracks are found to propagate toward the outer perimeter of the disk along distinct radial lines associated with the largest bending moment of the disk. The critical shock level at which failure originates increases with an increase in the clamp diameter, a reduction in the disk diameter, and an increase in the thickness of the disk. Some experimental results are presented to validate the numerical model.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2009;131(11):111008-111008-11. doi:10.1115/1.4000251.

This paper presents a new paradigm of system reliability prediction that enables the use of evolving, insufficient, and subjective data sets. The data sets can be acquired from expert knowledge, customer survey, inspection and testing, and field data throughout a product life-cycle. In order to handle such data sets, this research integrates probability encoding methods to a Bayesian updating mechanism. The integrated tool is called Bayesian Information Toolkit. Subsequently, Bayesian Reliability Toolkit is presented by incorporating reliability analysis to the Bayesian updating mechanism. A generic definition of Bayesian reliability is introduced as a function of a predefined confidence level. This paper also finds that there is no data-sequence effect on the updating results. It is demonstrated that the proposed Bayesian reliability analysis can predict the reliability of door closing performance in a vehicle body-door subsystem, where available data sets are insufficient, subjective, and evolving.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2009;131(11):111009-111009-8. doi:10.1115/1.4000239.

Thermally conductive filled polymers enable the creation of multifunctional structures that offer both anchoring points for the embedded actuators, as well as heat-dissipation functions, in order to facilitate the miniaturization of devices. However, there are two important challenges in creating these structures: (1) sufficient thermal management to prevent failure of the actuator and (2) the ability of the actuator to survive the manufacturing process. This paper describes a systematic approach for design of multifunctional structures with embedded heat-generating components using an in-mold assembly process to address these challenges. For the first challenge, the development of appropriate thermal models is presented along with incorporation of in-mold assembly process constraints in the optimization process. For the second challenge, a simulation of the molding process is presented and demonstrated to enable the determination of processing conditions ensuring survival of the in-mold assembly process for the embedded actuator. Thus, the design methodology described in this paper was utilized to concurrently optimize the choice of material, size of the structure, and processing conditions in order to demonstrate the feasibility of creating multifunctional structures from thermally conductive polymers by embedding actuators through an in-mold assembly process.

Commentary by Dr. Valentin Fuster

Technical Briefs

J. Mech. Des. 2009;131(11):114501-114501-8. doi:10.1115/1.3211094.

A mathematical model of a horizontal wind turbine drivetrain is developed by applying the flexible multibody dynamics theory based on the Lagrange formulation. The proposed model accounts for the variation in the number of teeth in contact and support bearing elasticity, which are known to influence the dynamic behavior of drivetrain significantly. The derivation of the system governing equation by Lagrange equations requires the formulations of the kinetic energy terms of both orbiting and rotating gears, the potential energy terms of time-varying tooth stiffness and bearing compliance, and the work from input torque. From the resultant governing equations, the natural frequencies and modes of interest are calculated, and the effect of bearing stiffness on those modes is examined. The rotational vibrations of the sun gears as well as the tooth contact forces between the sun and planet and the ring and planet are analyzed in detail. Result of the dynamic transmission error as a function of gearbox speed is also predicted to understand the overall dynamic behavior of the drivetrain system.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2009;131(11):114502-114502-3. doi:10.1115/1.3211095.

Manipulators of high accuracy and flexibility call for very strict requirements when their actuating mechanisms are downsized at the millimeter scale, which opens up the investigation of several novel actuator technologies such as those relying on piezoelectrics and shape memory alloys. In order to implement the precise and flexible operations, a new manipulator driven by a traveling wave ultrasonic motor and two inserted shape memory alloy actuators is presented. The structure and mechanism of the manipulator is introduced. After suitable material is selected, the prototype of the manipulator is fabricated. Finally, the experiments of the prototype are carried out to prove the property of the manipulator.

Commentary by Dr. Valentin Fuster
J. Mech. Des. 2009;131(11):114503-114503-6. doi:10.1115/1.4000215.

This paper attempts to establish unified topological models and corresponding mathematical representations for planar simple joint, multiple joint, and geared (cam) kinematic chains. First, the conventional topological representation models of kinematic chains are introduced. Then, new topological models of multiple joint and geared (cam) kinematic chains, which are derived from the topological model of simple joint kinematic chains, are presented. The characteristics of the new topological graphs and their associations with the topological graph of simple joint kinematic chains are also addressed. The most important merit of the new topological graphs is that it makes it much easier to undertake unified structure synthesis and further to establish conceptual design platform for various planar mechanisms. Synthesis examples of both multiple joint and geared chains are given, which show the effectiveness of the unified topological models.

Topics: Chain
Commentary by Dr. Valentin Fuster

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