bluuebunny/crossref_metadata_2025 huggingface dataset:
Robust Layout Synthesis of a MEM Crab-Leg Resonator Using a Constrained Genetic Algorithm
Authors: Fan Zhun , Achiche Sofiane
Published: May 2009

The research work carried out in this paper introduces a robust design method for layout synthesis of MEM resonator subject to inherent geometric uncertainties such as the fabrication error on the sidewall of the structure. The robust design problem is formulated as a multi-objective constrained optimization problem with certain assumptions and treated by a special constrained genetic algorithm. The MEM design used for validation is a crab-leg resonator taken from the literature. The results show that the approach proposed in this research can lead to design results that meet the target performance and are less sensitive to geometric uncertainties than typical designs.
Long Reach Articulated Carrier: Geometric and Elastic Error Calibration of the Flexible Model Followed by Nonlinear Generalized Error Calibration With Ordinary Polynomials
Authors: Chalfoun Joe , Bidard Catherine , Keller Delphine , Perrot Yann
Published: May 2009

The Interactive Robotics Unit of CEA LIST has developed a very challenging robotic carrier (called P.A.C.) which is able to perform high range intervention tasks inside blind hot cells. This long reach multi-link carrier has 11 degrees of freedom (DOF), an operational range over 6 meters of full extension and weighs less than 30 kg. The gravity effect in the manipulator is largely compensated by a special mechanical structure (the parallelogram) that helps to reduce the size of the actuators used to operate the robot. Due to its size and weight, this large robot manipulator holds lots of elastic and geometric deformations. Hence, it presents very low position accuracy. A flexible model is developed to take into account most of the structure deformations. A calibration method of the robot flexible parameters is used to reduce the positioning error of the end effector and the intermediate joints. Then, a second calibration method of the robot using generalized error matrices is applied to further reduce the residual positioning error of the system. These matrices are a polynomial function of the system geometry and joint variables. This method is first tested by simulation to ensure its viability on large manipulators. After encouraging simulation results, an experimental field is made for the calibration of the PAC manipulator. Results show that the adopted flexible model, with the new calibrated parameters, followed by the polynomial model is a good combination to correct and reduce the system errors.
Experimental Airway Smooth Muscle Response to Transverse Oscillations
Authors: Du Y. , Al-Jumaily A. M.
Published: May 2009

This paper presents an in vitro investigation of the stiffness variation of contracted airway smooth muscle subjected to external transverse oscillations. Two stiffness definitions are used to quantify the results, the dynamic stiffness to reflect variations during oscillation and the static stiffness to represent the net effect of oscillation. Under isometric contraction, these two stiffnesses are determined before, during and after oscillations. The results show that the dynamic stiffness has the tendency of decreasing with increasing frequency below 40 Hz; afterwards, the stiffness slightly increases. The static stiffness, however, remains almost unchanged for all frequencies except at 5 Hz where a small reduction is observed. Also it is observed that an increase in the length change ratio leads to a decrease in both stiffnesses. The difference in the behaviour of dynamic and static stiffness changes may be attributed to the effect of elasticity and mass inertia.
Modeling of Electrochemical Double Layer Capacitors by Means of Fractional Impedance
Authors: Marti´n Rodolfo , Quintana Jose J. , Ramos Alejandro , de la Nuez Ignacio
Published: May 2009

The application of the fractional calculus for modeling electrochemical double layer capacitors is a novel way to get simpler and precise models. By means of the method of impedance spectroscopy, experimental results for different values of these have been obtained. In this paper several classical mathematical models are studied and a different method is introduced in order to get a model from electrochemical double layer capacitors. This method is based on distinct models with fractional elements and the fitted of experimental data is realized with few parameters and minimal error. Finally, is proposed a model based in Havriliak-Negami function which achieves an excellent fitted on the over-all frequencies analyzed.
Cane Mounted Knee-Above Obstacle Detection and Warning System for the Visually Impaired
Authors: Balakrishnan M. , Paul Kolin , Garg Ankush , Paul Rohan , Mehra Dheeraj , Singh Vaibhav , Rao P. V. M. , Goel Vishwas , Chatterjee Debraj , Manocha Dipendra
Published: May 2009

There are numerous constraints that visually challenged people face in independent mobility and navigation. They primarily use the white cane as a mobility aid allowing them to detect close by obstacles on the ground. The detection of objects above knee height is almost impossible and is a major hindrance for them. In this work, we have reported the design and implementation of a detachable unit which acts to augment the functionality of the existing white cane, to allow knee-above obstacle detection. This unit consists of an ultrasonic ranger and a vibrator controlled by an eight bit microcontroller to offer an increased detection range of three meters. The distance information is conveyed to the user through non-interfering multi-frequency vibratory stimuli, the frequency of vibration indicating the proximity of obstacles. This unit is also capable of detecting fast moving obstacles. Considerable effort has gone into the electromechanical design of this unit conveying the vibrations effectively and ensuring that it is easily attachable on the existing white cane without sighted assistance. A crucial design optimization goal was cost — the unit has been developed as a “low cost” device which is affordable by the poor in developing countries.
Utilizing the Human Hand for Ergonomics Analyses in a Mobile Augmented Reality Testing Platform
Authors: Radkowski Rafael , Waßmann Helene
Published: May 2009

Sophisticated vehicle ergonomics are a relevant factor for the success of a new vehicle model. To support the evaluation of vehicle ergonomics we have developed a mobile Augmented Reality (AR) testing platform in cooperation with Volkswagen commercial vehicle. The mobile AR-based testing platform consists of a Volkswagen Multivan, where roof, pillars, and dashboard have been removed. The missing parts are replaced by new virtual parts. A head mounted display presents the virtual parts to the user of the mobile AR testing platform, that way, enabling visibility analyses. The user can also interact with the virtual components of the vehicle to perform reachability analyses. To support these analyses the user’s hands are recognized by the system. In this paper we introduce a method for tracking the user’s hands in a mobile AR testing platform. Using image processing the hands of the user are detected by checking for the skin color or the color of a glove the user wears. From image processing data we compute the position of the user’s real hand and potential collisions between the hand and virtual vehicle components. We also utilize results from collision detection for the interaction with the virtual objects.
Competing Dynamic Solutions in a Parametrically Excited Pendulum: Attractor Robustness and Basin Integrity
Authors: Lenci Stefano , Rega Giuseppe
Published: May 2009

The competing solutions of a planar pendulum parametrically excited by the vertical motion of the pivot are investigated in terms of both attractor robustness and basin integrity. Two different measures are considered to highlight how the integrity of the system is modified by changing the amplitude of the excitation. Various attractors, both in-well and out-of-well, are considered, and the integrity profiles of each of them are determined. A detailed discussion of the interaction and mutual erosion of the various attractors is performed, by clarifying the role of the two complementary measures, and the most relevant characteristics of the erosion profiles are interpreted in terms of the underlying topological mechanisms involving local or global bifurcations.
Semantic Operators for Handling Shape Sub-Domains in FE Model Preparation
Authors: Ferrandes Rosalinda , Le´on Jean-Claude , Giannini Franca , Falcidieno Bianca , Marin Phillipe
Published: May 2009

The evaluation of the mechanical behaviour of a product through a FE simulation requires an adaptation of the shape represented in its CAD model. During this shape modification process, several shape sub-domains are removed to simplify the subsequent mesh generation and FE solving tasks. The removal of a shape sub-domain is always driven by a specific mechanical criterion. In the proposed approach, the preparation of the simulation model takes place in a software environment based on a mixed geometric representation, which considers as reference polyhedral models but enables to keep the semantics of the input CAD models. We developed efficient complex operators for handling shape sub-domains by combining basic operators acting on the polyhedral model with different kinds of mechanical criteria and semantic information. These operators enable to respect user’s purposes and hypotheses as well as the specifications of the targeted mechanical problem. In this paper, we illustrate the various aspects and information involved in their definition and use.
Spectral Collocation-Based Optimization in Parameter Estimation for Nonlinear Time-Varying Dynamical Systems
Authors: Deshmukh Venkatesh
Published: May 2009

A constructive optimization algorithm using Chebyshev spectral collocation and quadratic programming is proposed for unknown parameter estimation in nonlinear time-varying dynamic system models to be constructed from available data. The parameters to be estimated are assumed to be identifiable from the data which also implies that the assumed system models with known parameter values have a unique solution corresponding to every initial condition and parameter set. The nonlinear terms in the dynamic system models are assumed to have a known form, and the models are assumed to be parameter affine. Using an equivalent algebraic description of dynamical systems by Chebyshev spectral collocation and data, a residual quadratic cost is set up which is a function of unknown parameters only. The minimization of this cost yields the unique solution for the unknown parameters since the models are assumed to have a unique solution for a particular parameter set. An efficient algorithm is presented step-wise and is illustrated using suitable examples.
Vibration Control of Composite Beams Using Adaptive Positive Position Feedback
Authors: Malik Nihal , Neild Simon , Wagg David
Published: May 2009

This paper presents a new method of active vibration control (AVC) of flexible composite cantilever beams. A recursive least mean squares (LMS) based filter is used to perform on-line system identification, updating a positive position feedback (PPF) controller in real-time. With conventional time-invariant PPF control the damping ratio and natural frequency are selected based on the structural response, with the feedback path taking the form of a second-order filter; therefore having performed an off-line system identification of the plant dynamics, this controller is relatively straightforward to implement. Some structures undergo parameter changes over time and actuation in the control sequence can contribute to this change in the system dynamics. PPF control is optimized when an accurate estimation of the natural frequency is available. It is demonstrated that the recursive LMS algorithm can be used to provide a continual on-line estimation of the plant dynamics, for robust control of a slender glass fiber beam. The result is an increase in vibration attenuation, which is robust to variations in the beam properties. It is shown that this controller delivers a high performance settling time when compared with the standard PPF controller for free vibration in the first mode. Robustness of the technique is further demonstrated by altering the fundamental frequency of the beam, via the addition of a lumped mass. The adaptive controller re-tunes itself to this parameter variation, ensuring a high level of vibration suppression is upheld.
Kinematic Analysis and Singularity Representation of 5-RPRRR Parallel Mechanisms
Authors: Tale Masouleh Mehdi , Gosselin Cle´ment
Published: May 2009

This paper presents a novel type of five-degree-of-freedom parallel mechanism generating the 3T2R motion with linear inputs. The kinematic geometry of the mechanism is presented and several important kinematic issues including the inverse kinematic problem, the vector-loop velocity equations, the constant orientation workspace and the singularity configurations are investigated. The principal contribution of this study is the determination of the workspace based on algebraic geometry (Bohemian domes) and the study of the the singularity configurations. Based on the results, some optimization hints are proposed to refine the kinematic properties.
Reduction of Primary Resonance Amplitude of Nonlinear Oscillator by a New Type of Nonlinear Dynamic Vibration Absorber
Authors: Jo Hoonhee , Yabuno Hiroshi
Published: May 2009

The paper proposes a nonlinear dynamic vibration absorber for primary external resonance of system having cubic nonlinearity. A main system with nonlinear spring stiffness and subjected to harmonic excitation is considered. We calculate nonlinear spring stiffness produced by repulsive force of permanent magnets using Coulomb’s law. A damped pendulum system, whose natural frequency is in the neighborhood of twice that of the main system, is nonlinear coupled to the main system by link as a dynamic vibration absorber. This nonlinear dynamic vibration bsorber does not utilize linear coupling to the main system but utilizes nonlinear coupling. Therefore, the attachment of the nonlinear dynamic vibration absorber does not increase the number of degrees of freedom of the main system. Primary resonance amplitude is decreased in the case when pendulum is unlocked and hysteresis of the frequency response curve is disappeared. This means that attachment of dynamic vibration absorber has the same effect that increases directly the damping coefficent of the main system. Experimental results for this type of device are compared with a numerical results obtained from Runge-Kutta method. Comparison of the frequency response curves with and without nonlinear dynamic vibration absorber show validity of the proposed absorber.
Experimental and Theoretical Investigation on the Nonlinear Mathieu Equation Applied to a Belt-Pulley System
Authors: Michon Guilhem , Manin Lionel , Parker Robert G. , Dufour Regis
Published: May 2009

This paper is devoted to the theoretical and experimental investigation of a sample automotive belt-pulley system subjected to tension fluctuations. The equation of motion for transverse vibrations leads to a nonlinear Mathieu equation. The analyzes are performed via either the harmonic balance method for establishing the instability regions or the multiple scales approach for predicting the nonlinear response. An experimental set-up gives rise to non-linear parametric instabilities. The experimental investigation shows that the model is satisfactory.
HLPR Chair: A Novel Indoor Mobility-Assist and Lift System
Authors: Bostelman Roger , Albus James , Chang Tommy , Hong Tsai , Agrawal Sunil K. , Ryu Ji-Chul
Published: May 2009

This paper describes a novel Home Lift, Position, and Rehabilitation (HLPR) Chair, designed at National Institute of Standards and Technology (NIST), to provide independent patient mobility for indoor tasks, such as moving to and placing a person on a toilet or bed, and lift assistance for tasks, such as accessing kitchen or other tall shelves. These functionalities are currently out of reach of most wheelchair users. One of the design motivations of the HLPR Chair is to reduce back injury, typically, an important issue in the care of this group. The HLPR Chair is currently being extended to be an autonomous mobility device to assist cognition by route and trajectory planning. This paper describes the design of HLPR Chair, its control architecture, and algorithms for autonomous planning and control using its unique kinematics.
A Self-Deployment Hexapod Model for a Space Application
Authors: Aridon G. , Al Majid A. , Blanchard L. , Re´mond D. , Dufour R.
Published: May 2009

This paper presents an efficient simulation tool for predicting a self deployment of an on-board deployable hexapod based on the release of stored strain energies provided by six tape-spring actuators. Six restoring force models describe their hysteretic behavior. A formulation of a direct dynamic model developed with a Lagrangian approach is achieved. Furthermore, tensor representation is used to condense and simplify the calculation of Lagrangian partial derivatives. Results are compared with a numerical model that performs the recursive Newton-Euler technique. Finally, the impact of the excitation of the base on the deployment performances is evaluated taking advantage of the proposed restoring force models.
Analysis of the Elastic Wave Behavior in a Cracked Shaft
Authors: LaBerge Kelsen , Adams Maurice
Published: May 2009

A new method currently under development for rotating shaft crack detection is presented. The underlying approach is to utilize the impact inherent in the once-per-revolution closing of a shaft crack. The axially traveling elastic compression wave, which is initiated by this impact, propagates to both ends of the shaft at the governing acoustic velocity. Provided suitable measurement near the shaft ends can detect the wave’s arrival, then extracting both the crack location and size is thereby feasible. Proof-of-concept for this new method for shaft crack detection utilizes one-dimensional wave propagation simulations and a newly designed test apparatus, which are presented.
Global Energy Fairing of B-Spline Curves in Path Planning Problems
Authors: Pesterev Alexander V. , Rapoport Lev B. , Gilimyanov Ruslan F.
Published: May 2009

The paper is concerned with path planning for mobile robots. Specifically, the discussion is related to the following problem: Given an ordered sequence of points on the plane, construct a path that fits these points and satisfies certain smoothness requirements. These requirements may be different in different problems and imply basically that the constructed path is to be realizable. Such a problem arises, e.g., when it is required to follow in an automated mode a path stored as a discrete set of points, which, e.g., were collected by a GPS receiver installed on a car when it followed this path for the first time. Due to errors inherent in the data points, the shape of the curve approximating the desired path turns out often inappropriate. The shape of the curve can be improved by applying the so-called fairing, which consists in moving the original data points with the aim to minimize some fairness criterion. Adequate small variations of the data points preserve the proximity of the resulting path to the original data points and make it fairer. In the paper, a new global fairing method is proposed. It reduces the problem of constructing a fair cubic B-spline curve to solving a quadratic programming problem with simple constraints. The fairing criterion is based on minimizing jumps of the spline third derivative. The discussion is illustrated by numerical examples of fairing two actual paths constructed by data points collected by a GPS/GLONASS receiver mounted on a moving vehicle.
Indirect Encoding of Structures for Evolutionary Design
Authors: Nicaise Fabien , Antonsson Erik K.
Published: May 2009

The use of Evolutionary Computations (EC’s) has become one of the primary methods in the field of automated design synthesis. The overwhelming majority of EC’s in use today use a direct encoding, where an individual is described by its gene string. This means that every engineering domain must create its own encoding scheme, making implementation in new fields difficult and slow. Additionally, direct encoding does not produce symmetry or modularity, unless these attributes are written into the encoding scheme ab initio. Direct encoding, however, is not the way that genetic information is used in biological evolution. In nature, each DNA string (genotype) is composed of instructions or rules on how an individual should grow and develop. This has provided nature with a wide array of evolved solutions, based on simple coding blocks. This paper presents a method of indirect (rules-based) encoding for an EC based on the biological analog of development: the gene string no longer describes the individual, but rather contains an instruction set on how to generate the individual. This allows for additional elements to be added by modifying the rule set, rather than re-composing the entire genetic structure. Indirect encoding also can have a built-in response to the environment, and is therefore able to adapt more readily to dynamic situations. Examples are shown to demonstrate the rule-set and its adaptability.
Case-Based Retrieval Approach of Supporting Process Planning in Layer-Based Additive Manufacturing
Authors: Yim Sungshik , Rosen David
Published: May 2009

The process planning task for a given design problem in additive manufacturing can be greatly enhanced by referencing previously developed process plans. In this research, a case-based retrieval method, called the DFM (Design For Manufacturing) framework, that retrieves previously formulated process plans is proposed to support process planning. To support the DFM Framework, we have developed an information model (ontology) of manufacturing process knowledge in the domain of additive manufacturing processes, including design requirements, process plans, and rules that map requirements to plans. Description Logic (DL) is identified as an appropriate mathematical formalism to encode the ontology and realize the computational mapping between the design and manufacturing domains. Storage and retrieval algorithms are presented that, first, structure the repository of previous DFM problems and, second, enable DFM problems to be retrieved.
On the Implementation of Coulomb Friction in a Volumetric-Based Model for Contact Dynamics
Authors: Gonthier Yves , McPhee John , Lange Christian
Published: May 2009

A contact model based on volumetric properties is presented. The model properties are derived assuming the elastic behavior of the contacting objects can be approximated as a modified Winkler elastic foundation model, and that the contact surface between the objects is approximately flat. The resulting model includes friction and features a contact force proportional to the inter-penetration volume. The work shows that the Coulomb friction is affected by the relative motion. The contact model can be used as a general-purpose tool to model contact dynamics for a broad range of object shapes because the volumetric quantities that serve as input to the contact model can be determined for any object shape. A numerical simulation of a Tippe-Top is presented, and the results are shown to be consistent with published data, but with a higher spinning friction torque.
Categories of Visual Quality Cues
Authors: Forslund Karin , So¨derberg Rikard
Published: May 2009

An industrial design concept can be adapted to manufacture and assembly by striving for visual design properties that are economical and time-efficient to produce according to specifications. One aspect of this is to assess whether the concept will be visually sensitive to distortions in structure, form, colour, gloss and texture. Visual appearance problems are often unrelated to the actual quality or functionality of a product. In the eyes of the customer, they may however serve as intrinsic quality cues, perceptions of quality attributes acquired by observing the product before purchase. Through interviews conducted at an automobile company and a mobile telecom company, factors considered important for the visual quality appearance of their products were identified. These factors are divided into groups, and examples are given. The result is an overview of visual quality appearance aspects, which demonstrates that design for perceived quality can be a trade-off between quality cues as deliberately placed styling features and quality cues stemming from complex assembly variation conditions.
Modal Characterization of the Instantaneous Mobility of Manipulators
Authors: Salgado Oscar , Altuzarra Oscar , Amezua Enrique , Herna´ndez Alfonso
Published: May 2009

In this paper, a computational approach suitable to compute the instantaneous mobility of manipulators in any kind of configuration (either singular or nonsingular) using a general purpose software is presented. Although the procedure is applicable to any formulation of the velocity equation, in this paper authors have used a point-based jacobian formulation of the manipulator. The end-effector’s instantaneous mobility is analyzed, first discriminating among its rotational, translational and passive freedoms, and then computing its principal screws. Then, either its instantaneous screw systems or certain instantaneous pitch surfaces can be depicted. The approach is illustrated with its application to the 3-URU DYMO parallel manipulator.
A Component Based Optimization Approach for Modular Robot Design
Authors: Johansson Bjo¨rn , Pettersson Marcus , O¨lvander Johan
Published: May 2009

In this paper, an approach for modular design of industrial robots is presented. The approach is to introduce an objectoriented simulation model of the robot and combine this with a discrete optimization algorithm. The simulation model of the industrial robot is developed in Modelica, an object oriented modeling and simulation language, and simulated in the Dymola tool. The optimization algorithm used is a modification of the Complex method that has been developed in Matlab and connected to the simulation program. The optimization problem includes selecting components such as gearboxes and motors from a component catalogue and the objective function considers minimization of cost with constraints on gear box lifetime. Furthermore, the correctness of the model has been verified by comparison with an in-house simulation code with high accuracy.
Applications of Virtual Reality in Computer Integrated Manufacturing Systems
Authors: Manesh Hamed Farahani , Bal Mert , Hashemipour Majid
Published: May 2009

The Virtual Reality (VR) is a computer system, which can save time, cut costs and help to improve the learning process in engineering laboratory education by interactive 3D simulation environments. This paper gives an overview on the VR applications in undergraduate engineering laboratory education and presents a VR system tool ‘Virtual CIM Laboratory’ (VCIMLAB), developed for laboratory training on Computer Integrated Manufacturing (CIM) systems. The proposed VR system is a cost-effective and safe approach of teaching the operations of automated manufacturing systems, which deal primarily with the expensive and complex high technology industrial automation equipments. The VCIMLAB allows students to self-experience on these systems without the need to work on actual equipments in the laboratory.
Computational Model for Calculating the Dynamical Behaviour of Generators Caused by Unbalanced Magnetic Pull and Experimental Validation
Authors: Pennacchi Paolo , Frosini Lucia
Published: May 2009

This paper presents the modelling of the unbalanced magnetic pull (UMP) in generators and its experimental validation in a real machine. UMP is one of most relevant effects of electromechanical interactions in rotating machinery and manifests itself when rotor eccentricity causes an imbalance of the electromagnetic forces acting upon rotor and stator surfaces, so that a net radial force is developed. In small and stiff machines, like electrical motors, this phenomenon can be avoided by means of carefully assembling and manufacturing. On the contrary, big generators of power plants, supported by journal bearings, operate above their first critical speed behaving like flexible shafts, therefore the eccentricity of the active part of the rotor with respect to the stator is unavoidable. In the first part of the paper, an accurate model for calculating the UMP force is presented. This model is more general than those available in literature that are limited to circular orbits and is based on the actual position of the rotor inside the stator, therefore on the actual air gap distribution, regardless of the orbit type. The closed form of the non linear UMP force components is presented. In the second part, the experimental validation of the proposed model is presented, by considering a steam turbo generator of a power plant and by comparing the simulated dynamic behaviour in the time domain of the machine to the experimental one, without and with the excitation of the magnetic field in the generator.
Sensitivity of Critical Value of Friction Coefficient for Brake Squeal Analysis
Authors: Huang Jinchun , Krousgrill Charles M. , Bajaj Anil K.
Published: May 2009

Brake squeal has been a major concern throughout the automotive industry. Structural modification is a practical and effective way to reduce brake squeal. However, few if any, systematic techniques exist to guide in this structural modification. In this work, a sensitivity analysis for brake squeal control is presented. The critical value of friction coefficient is used as a measure of squeal propensity. Based on the reduced-order characteristic equation method which can accurately estimate the critical value of friction coefficient, a sensitivity analysis of system stability with respect to lining stiffness and lining geometry is presented for a drum brake system. The sensitivity analysis can be conducted without creating new system models or performing a full complex eigenvalue analysis. Furthermore, the sensitivity analysis reveals the regions of contact area which have strong influence on squeal. It is shown that the separation of elastically coupled frequencies is influenced by the grooves in lining material, and the frequency variation can be related to the mode shapes of the drum and the shoes.
MEMS Optical Force Sensor Enhancement Via Compliant Mechanism
Authors: Roman Gustavo A. , Wiens Gloria J.
Published: May 2009

Although there are capacitive surface micromachined force sensors with adequate resolution for cell manipulation and microneedle injections, it comes with the sacrifice of dynamic range and linearity. In contrast, optical based force sensors can provide the desired resolution and maintain relatively large sensing ranges compared to similar capacitive sensors. Plus, optical interferometry provides a sensing method that uncouples the conflicting design parameters, such as sensitivity and linearity. The current drawback to optical interferometry is the large off-chip equipment that is currently used in the operation of optical sensors. However, innovative techniques are being applied to surface micromachined microphones that allow off-chip components to be integrated onto the sensing chip. These same techniques can easily translate to the force sensor presented in this research, due to the similarities in the sensing methods. The thrust of this work is to explore a mechanism approach for enhancing the performance of a surface micromachined optical force sensor. A new design is presented which introduces a special mechanism, known as the Robert’s mechanism, as an alternate means in which the device is structurally supported. The new design’s implementation is achievable using an equivalent compliant mechanism. Initially, an analytical set of pseudo-rigid-body-model equations were developed to model the compliant design. A more accurate model was then constructed using FEA methods. The geometric parameters of the compliant Robert’s mechanism were then optimized to obtain a sensor with improved linearity and sensitivity. Overall, the force sensor provides higher sensitivity, larger dynamic range and higher linearity compared to a similar optical force sensor that uses a simple structural supporting scheme. In summary, this paper demonstrates the effectiveness of using a mechanism approach for enhancing the performance of MEMS sensors. The expected impact is to improve biomedical experiments and help further advance research that can improve quality of life.
Range of Motion of Upper Limb Joint Angles During Two Tasks for Transradial Prosthetic Design
Authors: Carey Stephanie L. , Highsmith M. Jason , Dubey Rajiv
Published: May 2009

During wartime, the numbers of amputees will likely increase adding to the need for progress in upper limb prosthetic design. Improvement of prostheses often requires knowledge of how the body adapts. Added weight and fatigue are complaints of upper limb prostheses users. Current improvements in the design of a transradial prosthesis include advanced technology in control systems and electronics that improve its functions. However, these improvements often require excess mass distally along the prosthesis. A transradial prosthesis without a dynamic wrist component may cause awkward compensatory motion in the shoulder and elbow. This work analyzes the ranges of joint movement of shoulder and elbow during two tasks: drinking from a cup and lifting a box. The main purpose of this study was to determine if simulating a basic transradial prosthesis by limiting motion of the forearm and wrist using a brace, would cause significant changes in the compensatory motion of the shoulder and elbow during the tasks. The second purpose of the study was to determine if the location of added mass of 96 g (mass of an electrical wrist rotator) would affect shoulder and elbow angles during these same tasks. A group of able-bodied participants were asked to complete the tasks during the following conditions: (1) no intervention (2) while wearing a brace that restricted forearm and wrist motion of their dominant arm (right) (3) wearing the same brace with a 96 g mass added near the elbow, (4) with the same brace and a 96 g mass added near the wrist. Subject movements were captured using a motion capture system and ranges of movement of shoulder and elbow, as well as degree of asymmetry (DoA) during the box lift were calculated for each subject. Three trials were collected for each test condition and were averaged as a representative for each subject. Statistical analysis of the results concluded that during drinking elbow flexion was significantly different in case 1 from the other 3 levels. Statistical analysis of lifting found significant differences in the dominant (right) shoulder and elbow flexion between all 4 levels, while their relative degree of symmetry was found to be statistically different between level 1 and 3–4. The study concludes that bracing limits forearm and wrist affects shoulder and elbow flexion and their relative DoA. The position of a 96g mass did not cause any statistical differences in the movements observed or in their DoA. Further testing will examine the transradial amputee population as well as the effects of position of added mass on joint torques during common tasks.
Static Analysis of Torque and Coupler Driven Spherical Four-Bar Mechanisms With an Applied Load
Authors: Perkins David A. , Turner Michael L. , Murray Andrew P.
Published: May 2009

Spherical four-bar mechanisms are classically designed to be driven via a torque applied to the input link. This paper presents a comparison of the resulting statics associated with this method of actuating a spherical four-bar versus actuating the mechanism with the force applied directly to the coupler. A force may be applied in this fashion via a spherical-prismatic-spherical, or SPS, chain mounted between the ground frame and the coupler with the prismatic joint actuated. The spherical four-bar linkage with the SPS chain connected directly to the coupler defines a spatial analogue to the Stephenson III six-bar mechanism. Moreover, this work builds on previously derived static models of spherical four-bars by considering the additional loading issues associated with links at different radii and the forces that arise from an external load on the coupler.
A New Low-Cost System for Tyre-Road Force Measurements: Design and Validation
Authors: Braghin Francesco , Cheli Federico , Giangiulio Emiliano , Mancosu Federico
Published: May 2009

The measurement of tyre-road contact forces is the first step towards the development of new control systems for the improvement of vehicle safety and performances. At present, tyre-road contact force measurement systems are very expensive and modify the non suspended vehicle inertia due to their high mass and rotational inertia moment. Thus, vehicle dynamics is significantly affected. The measured contact forces are therefore not fully representative of the contact forces that the tyres will experience during real working conditions. A new low-cost tyre-road contact force measurement system has been developed that is installable on any type of wheel. Its working principle is based on the measurement of three deformations of the wheel. Through a dynamic calibration of the instrumented wheel it is possible to reconstruct all three contact force and torque components once per wheel turn. These forces are then sent to the vehicle chassis and may be used by on-board active control systems to improve vehicle safety and performances. Validation tests were carried out with a vehicle having all four wheels equipped with the low-cost tyre-road contact force measurement system. It was possible to reconstruct contact forces once per wheel turn in any working condition with a precision that is comparable to that of existing high-cost measurement systems ([1], [2], [3], [4], [5]).
Size and Shape Optimization of a 1.0mm Multifunctional Forceps-Scissors Instrument for Minimally Invasive Surgery
Authors: Aguirre Milton E. , Frecker Mary
Published: May 2009

A size and shape optimization routine is developed and implemented on a 1 mm multifunctional instrument for minimally invasive surgery. The instrument is a compliant mechanism, without hinges, capable of both grasping and cutting. Multifunctional instruments have proven to be beneficial in the operating room because of their ability to perform multiple tasks, thereby decreasing the total number of instrument exchanges in a single procedure. In addition, with fewer exchanges the risk of inadvertent tissue trauma as well as overall surgical time and costs are reduced. The focus of the paper is to investigate the performance effects of allowing the cross-sectional area along the length of the device to vary. This is accomplished by defining various cross-sectional segments along the device in terms of parametric variables (Wi) and optimizing the dimensions to provide a sufficient forceps jaw opening while maintaining adequate cutting and grasping forces. Two optimization problems are considered. First, all parametric segments are set equal to one another permitting all cross-sections to vary uniformly and achieving size optimization. Second, each segment is defined as a separate design variable to allow segments to vary independently and thereby achieving shape optimization. Due to the device’s symmetry, one-half of the mechanism is modeled as a cantilever beam undergoing large deformation. ANSYS’ optimization module is employed using the first order method because it is capable of performing optimization considering non-linear deformation and multiple loading conditions. Finally, prototypes are fabricated using wire EDM and prototype evaluations are conducted to compare size versus shape optimization, and to validate ANSYS as the solution method.
Software for Investigating the Kinematics, Statics and Dynamics of Coupler-Driven Four-Bars for Two Position Synthesis
Authors: Turner Michael L. , Grimm Eric M. , Debrosse Daniel , Kosmac Kevin , Murray Andrew P.
Published: May 2009

The synthesis of a planar four-bar in which a point on the coupler reaches two specified points and orientations generates a six-fold space of solutions. The solution space increases if additional links are added to drive the mechanism, such as the Stephenson III. This paper presents an investigation of a coupler driven four-bar linkage, a Stephenson III six-bar with an RPR chain driving the four-bar sub-chain instead of the classically defined 3R chain. The software allows the designer to specify the problem and quickly scan the solution space. A comparison is constructed between a four-bar driven through a torque at the input link and a coupler-driven four-bar. Changes in branch points, the joint force index and the dynamics are observed.
Singularity Equations of Gough-Stewart Platforms Using a Minimal Set of Geometric Parameters
Authors: Jiang Qimi , Gosselin Cle´ment M.
Published: May 2009

So far, in the derivation of the singularity equations of Gough-Stewart platforms, all research works defined the mobile frame by making its origin coincide with the considered point on the platform. One problem can be that the obtained singularity equation contains too many geometric parameters and is not convenient for singularity analysis, especially not convenient for geometric optimization. Another problem can be that the obtained singularity equation cannot be used directly in practice. To solve these problems, this work presents a new approach to derive the singularity equation of the Gough-Stewart platform. The main point is that the origin of the mobile frame is separated from the considered point and chosen to coincide with a special point of the platform in order to minimize the geometric parameters defining the platform. Similarly, by defining a proper fixed frame, the geometric parameters defining the base can also be minimized. In this way, no matter which practical point of the platform is chosen as the considered point, the obtained singularity equation contains only a minimal set of geometric parameters and becomes a solid foundation for the geometric optimization based on singularity analysis.
Inter-Trial Dynamics of Repeated Skilled Movements
Authors: John Joby , Cusumano Joseph P.
Published: May 2009

In this paper, we develop a class of discrete dynamical systems for modeling repeated, goal-directed, kinematically redundant human movements. The approach is based on a mathematical definition of movement tasks in terms of goal functions. Each goal function can give rise to an associated goal equivalent manifold (GEM), which contains all body states that exactly satisfy the task requirements. A hierarchical control scheme involving in-trial action templates and inter-trial stochastic optimal error correction is included to generate a nonlinear map for the repeated execution of the task. A simple throwing task is used to illustrate the underlying concepts and to develop a model problem for further study. The performance at the goal level, as measured by the root mean square error, is shown to result from factors that are measures of passive sensitivity, the magnitude of body fluctuations, the orientation of fluctuations with the GEM, and the stability properties of the inter-trial controller. The action of the inter-trial controller developed for our model system is simulated and is shown to agree with the mathematically predicted performance.
Assessment and Evaluation of Undergraduate Design Engineering Projects
Authors: Platanitis George , Pop-Iliev Remon
Published: May 2009

Methodologies focused on assessing and evaluating the developed learning outcomes and the students’ ability to adequately combine design engineering project work with the knowledge gained from coursework and integrate these by extending it into practical applications exist and are continually evolving. However, it seems that there is still a lot of room for their improvement. In this research, a universally applicable methodical tool, developed in recent years, that is generally useful in knowledge evaluation exercises, was directly applied to the design engineering field. The efforts were focused on developing a model to evaluate the extent to which students have applied their knowledge in various design engineering projects over their undergraduate education. Each component of the proposed model represents a different level of application starting from one’s basic understanding of a concept, the ability of one to relate knowledge and articulate relationships among elements of the fundamentals, and finally culminating into the ability of one to take knowledge and apply it to a novel situation. Rubrics (charts describing learning at different levels of development) were used to evaluate students’ level of knowledge application. The preliminary results of this study proved that the model is quite useful in evaluating the learning process of students via design projects and methods can be developed to customize and maximize it.
Decision Making and Constraint Tradeoff Visualization for Design Under Uncertainty
Authors: Rangavajhala Sirisha , Messac Achille
Published: May 2009

In design optimization problems under uncertainty, two conflicting issues are generally of interest to the designer: feasibility and optimality. In this research, we adopt the philosophy that design, especially under uncertainty, is a decision making process, where the associated tradeoffs can be conveniently understood using multiobjective optimization. The importance of constraint feasibility and the associated tradeoffs, especially in the presence of equality constraints, is examined in this paper. We propose a three-step decision making framework that facilitates effective decision making under uncertainty: (1) formulating a multiobjective problem that effectively models the tradeoffs under uncertainty, (2) generating design alternatives by solving the proposed multiobjective robust design formulation, and (3) choosing a final design using filtering and constraint uncertainty visualization schemes. The proposed framework can be used to systematically explore the design space from a constraint tradeoff perspective. A tolerance synthesis example is used to illustrate the proposed decision making process.
Nonlinear Contact Parameter Estimation for Robotic Systems With Payload
Authors: Mu Xiuping , Sharf Inna
Published: May 2009

Simulating robotic operations where the robot interacts with its environment remains a challenging task because of the difficulties involved in contact modeling. At present, the basic methodologies for modeling contact are well established and have been integrated into many existing multibody dynamics formulations and software. One popular approach involves modeling the normal contact force as a continuous function of deformation, according to a particular constitutive relation. These models are usually simple in form and are easily integrated into any multibody framework because they provide an explicit relationship between the normal contact force and a geometric penetration variable, with the aid of appropriate contact parameters. One issue that remains ambiguous, however, is the choice of the contact parameters to be ‘fed’ into the force-deformation law. In this paper, the problem of contact parameter estimation is addressed in the context of a nonlinear contact force model proposed by Hunt and Crossley. An offline parameter estimation algorithm is developed which effectively transforms the nonlinear estimation problem into a linear one, it in turn solved using a multi-pass recursive technique. Results of application of the algorithm to simulated and experimental data are presented, the latter obtained with a six-DOF robotic manipulator and a variety of payload materials and geometries. Comparison of the proposed method to the nonlinear curve fitting algorithm from MATLAB demonstrates some advantages and limitations.