bluuebunny/crossref_metadata_2025 huggingface dataset:
Integrating Finite Element Analysis and Computer Aided Design Into Materials Engineering and Undergraduate Research Projects: Active and Engaged Students
Authors: Kitto Kathleen L.
Published: May 2009

Finite Element Analysis (FEA) and Computer Aided Design (CAD) have been integrated into our Introductory Materials Engineering course and certain undergraduate independent research experiences at Western Washington University. The key idea underlying these modifications to the curriculum is to increase active student interest and involvement in their own learning. Active learning does indeed promote the way students construct their own understanding of materials engineering design solutions. Since a diverse group of students learn in many different ways, delivering curriculum in multiple ways increases the probability of improving student learning. During the past four years, several strategies have been implemented in our Introduction to Materials Engineering course to transform it from a traditional lecture-centric class to an active, “learner-centered” environment. Case studies, problem based learning (PBL), concept questions, stringed musical instrument design, and active, in-class demonstrations have all been integrated into the course during this transformation. Recent additions to this new course strategy have been the integration of Computer Aided Design (CAD) and Finite Element Analysis (FEA) illustrations and animations as in-class dynamic demonstrations and applications. In this course, the students must master the ability to use fundamental materials properties such as: tensile strength, yield strength, modulus of elasticity, Poisson’s ratio, flexural strength, hardness, fatigue limit/life, and creep life, so they can correctly select a material for a simple design case given multiple engineering constraints. Since so much of this course is design and applications based, FEA makes an ideal compliment to the other active and conceptual strategies. This paper, then, describes the new FEA and CAD additions and strategies to the course. In addition, the changes in the Introduction to Materials Engineering course have generated a great deal of student interest in completing independent research projects investigating materials for stringed musical instruments and numerous research projects have been completed. The most impressive of these, the design and production of a carbon fiber composite violin using all computer-based tools and an independent research project on guitar design are described. Finally, the paper provides an initial assessment analysis that shows students improving on classical test problem scores, having an enhanced ability to complete a more complex final design problem, and demonstrating increased interest in engineering design.
Real Time Machinability Analysis of Free Form Surfaces on the GPU
Authors: Lysenko Mikola , Rahmani Keyvan , D’Souza Roshan
Published: May 2009

In this paper a new hardware accelerated method is presented to evaluate the machinability of free-form surfaces. This method works on tessellated models that are commonly used by CAD systems to render three-dimensional shaded images of solid models. Modern Graphics Processing Units (GPUs) can be programmed in hardware to accelerate specialized rendering techniques. In this research, we have developed new algorithms that utilize the programmability of GPUs to evaluate machinability of free-form surfaces. The method runs in real time on fairly inexpensive hardware (<$600), and performs well regardless of the surface type. The complexity of the method is dictated by the size of the projected view of the model. The proposed method can be used as a plug-in in a CAD system to evaluate manufacturability of a part at early design stages. The efficiency and the speed of the proposed method are demonstrated on some complex objects.
Time Delay and Feedback Control of an Inverted Pendulum With Stick Slip Friction
Authors: Campbell Sue Ann , Crawford Stephanie , Morris Kirsten
Published: May 2009

We consider an experimental system consisting of a pendulum, which is free to rotate 360 degrees, attached to a cart which can move in one dimension. There is stick slip friction between the cart and the track on which it moves. Using two different models for this friction we design feedback controllers to stabilize the pendulum in the upright position. We show that controllers based on either friction model give better performance than one based on a simple viscous friction model. We then study the effect of time delay in this controller, by calculating the critical time delay where the system loses stability and comparing the calculated value with experimental data. Both models lead to controllers with similar robustness with respect to delay. Using numerical simulations, we show that the effective critical time delay of the experiment is much less than the calculated theoretical value because the basin of attraction of the stable equilibrium point is very small.
The Mechanism and Solution of Harmonic Gear Whine Noise in Automotive Transmission Systems
Authors: Yoo Jaegon , Kang Koo-Tae , Huh Jin-Wook , Choi Chimahn
Published: May 2009

Since gear noise in automotive is one of the most unpleasant noises for passengers, various solutions, such as gear design optimization, tooth modification and transfer path reformations in the vehicle have been developed. But, these attempts are mainly focused on the fundamental mesh excitation of the gear set without any consideration of their harmonic noise (1st, 2nd or higher). Harmonic gear whine noise is easily audible in the vehicle because of their high frequency characteristics in spite of low sound pressure level. This annoying pure-tone noise is usually issued in the transmission system composed of the gears produced by grinding process. This paper will present the main sources of this harmonic gear whine noise with the test results of gears with identical design parameters but having different surface structure (roughness parameters, wave patterns). Additionally, manufacturing guidelines of gear surface structure will be proposed at the end of this paper.
Optimization of Bicycle Frames Using Genetic Algorithms
Authors: Huang Yuan Mao , Wang Kuo Juei
Published: May 2009

A bicycle frame is optimized for the lightest weight by using genetic algorithms in this study. Stresses of five rods in the bicycle frame less than the material yielding strength with consideration of the factor of safety are the constraints. A two-dimensional model of the frame is created. Equilibrium equations are derived and loads acting on rods are determined. A known function is used to verify feasibility of the program generated. Effects of the mutation rate, the crossover rate and the number of generation on the mean and the standard deviation of the fitness value are studied. The optimal solutions with the outer diameters and the inner diameters of the front frame rods to be 0.040 m and 0.038 m, respectively, the outer diameters and the inner diameters of the rear frame rods to be 0.024 m and 0.021m, respectively, and the weight of the bicycle frame to be 0.896 kg are recommended for the bicycle frame.
The Generalized Quasi-Variational Principles of NCS and Its Application in Mechanical Vibration
Authors: Liang Lifu , Dai Liming , Guo Qingyong
Published: May 2009

According to the corresponding relations between generalized forces and generalized displacements, the basic equations of elasto-dynamics in phase space are multiplied by corresponding virtual quantities, integrated and then added algebraically. By considering the character of fellow body and surface forces, the generalized quasi-variational principles of non-conservative systems are established in elasto-dynamics in phase space. By doing inverse Laplace transformation, the convolutional generalized quasi-variational principles of non-conservative systems of elasto-dynamics are established in original space. Applying the generalized quasi-complementary energy principle to the mechanical vibration problem of two kinds of variables, the authors of this paper present a calculation method for solving two kinds of variables simultaneously: the internal force and the displacement of a typical fellow force system.
A Jacobian-Based Algorithm for the Attitude Control of a Rigid Body Undergoing Fully-Reversed Sequences of Rotations
Authors: Koh Sung K. , Chirikjian Gregory S. , Ananthasuresh G. K.
Published: May 2009

Jacobian-based control algorithms for the attitude control of a rigid body undergoing a series of forward and reverse rotations are proposed in this paper. Unlike the Jacobian of conventional systems such as a robot manipulator, the Jacobian of the system manipulated through FR rotations is singular as well as a null matrix at the identity that makes the conventional Jacobian formulation break down. In order to handle the singularities involved in FR rotations, the Jacobian algorithm is reformulated and implemented so as to synthesize the FR rotation for a desired orientation change. We introduce the single-step and multiple-step Jacobian methods in this paper. The single-step Jacobian method synthesizes a specific FR rotation that enables the rigid body to reach a given desired orientation through a single step. The multiple-step Jacobian method synthesizes physically feasible FR rotations on an incremental optimal path to a desired orientation. A comparison with existing control algorithms for FR motions verifies the fast convergence property of the Jacobian-based algorithm and the accuracy of the solutions.
Mobility of Single Loop Linkages: A Final Word?
Authors: Rico Jose´ Mari´a , Cervantes J. Jesu´s , Rocha Juan , Gallardo Jaime , Aguilera Luis Daniel , Pe´rez Gerardo Israel , Tadeo Alejandro
Published: May 2009

Setting aside paradoxical linkages such as Bennett’s, Bricard’s or Goldberg’s, the mobility of single loop linkages seemed, with the developments on mobility analysis carried out in the last five years, a closed chapter in kinematic research. However, recent developments on the mobility of parallel platforms have shed additional insight into the problem. This contribution attempts to unify the results obtained in the last five years in the area of mobility of single-loop kinematic chains to state what appears to be a final word on the subject.
Finite Element Analysis Applied to Ergonomic Design of 2-Piece Aluminum Beverage Cans and Bottles
Authors: Han Jing , Yamazaki Koetsu , Nishiyama Sadao , Itoh Ryoichi
Published: May 2009

This paper has introduced the finite element analysis (FEA) into the ergonomic design to evaluate the human feelings numerically and objectively, and then into the optimization design of beverage containers considering human factors. In the design of the end of can (the lid of can), experiments and the FEA of indenting vertically the fingertip pulp by a probe and the tab of end have been done to observe force responses and to study feelings in the fingertip. A numerical simulation of finger lifting the tab for opening the can has also been performed, and discomfort in the fingertip has been evaluated numerically to present the finger-accessibility of the tab. The comparison of finger-accessibility between two kinds of tab ring shape designs showed that the tab that may have a larger contact area with the finger is better. In the design of beverage bottles served hot drinks, the FEA of tactile sensation of heat has been performed to evaluate numerically the touch feeling of the finger when holding the hot bottle. The numerical simulations of embossing process have also been performed to evaluate the formability of various rib-shape designs. The optimum design has then been done considering the hot touch feeling as well as the metal sheet formability.
Synthesis of Adjustable Linkages for Precise Function Generation Using the Optimal Link Length Adjustment
Authors: Zhou Hong
Published: May 2009

Nonadjustable four-bar linkages can only generate the desired functions precisely at a limited number of points. With one link length adjustment, the whole desired function can be generated precisely. This paper uses the coupler or the driven link length adjustment to generate the desired functions precisely. The synthesis model of adjustable linkages is established based on the optimal link length adjustment. For different applications, the desired functions can be generated precisely by using the continuous adjustment or approximately by fixing the adjustable link at an appropriate length after the adjustable linkage is optimally synthesized. The optimal fixed length of the adjustable link is selected by minimizing the maximum absolute structural error between the generated function and the desired function. The synthesis approach proposed in this paper is verified by two demonstrated examples.
Effects of Amplitude and Frequency of Vibration Stimulation on Cultured Osteoblasts
Authors: Shikata Tetsuo , Shiraishi Toshihiko , Tanaka Kumiko , Morishita Shin , Takeuchi Ryohei
Published: May 2009

Mechanical stimulation to bones affects osteogenesis such as decrease of bone mass of astronauts under zero gravity, walking rehabilitation to bone fracture and fracture repair with ultrasound devices. Bone cells have been reported to sense and response to mechanical stimulation at cellular level morphologically and metabolically. In the view of mechanical vibrations, bone cells are deformed according to mechanical stimulation and their mechanical characteristics. Recently, it was reported that viscoelasticity of cells was measured using tensile and creep tests and that there was likely natural frequency and nonlinearity of cells in the sense of structural dynamics. It suggests that there is effective frequency and amplitude of mechanical stimulation on osteogenesis by bone cells. In this study, sinusoidal inertia force was applied to cultured osteoblasts, MC3T3-E1, and effects of frequency and acceleration amplitude of mechanical vibration on the cells were investigated in respect of cell proliferation, cell morphology, bone matrix generation and alkaline phosphatase (ALP) gene expression. After the cells were cultured in culture plates in a CO2 incubator for one day and adhered on the cultured plane, vibrating groups of the culture plates were set on an aluminum plate attached to a exciter and cultured under sinusoidal excitation in another incubator separated from non-vibrating groups of the culture plates. Acceleration amplitude and frequency were set to several kinds of conditions. The time evolution of cell density was obtained by counting the number of cells with a hemocytometer. The cell morphology was observed with a phase contrast microscope. Calcium salts generated by the cells were observed by being stained with alizarin red S solution and their images were captured with a CCD camera. The vibrating groups for the cell proliferation and the calcium salts staining were sinusoidally excited for 24 hours a day during 28-day cultivation. Gene expression of ALP was measured by a real-time RT-PCR method. After the vibrating groups for the PCR were excited for 6 hours, the total RNAs were extracted. After reverse transcription, real-time RT-PCR was performed. Gene expression for ALP and a housekeeping gene were determined simultaneously for each sample. Gene levels in each sample were normalized to the measured housekeeping gene levels. As a result, it is shown that saturate cell density becomes high and bone matrix generation is promoted by applying mechanical vibration and that there may be some peaks to frequency and a certain threshold value to acceleration amplitude of mechanical vibration for saturation cell density and bone matrix generation.
A Monte Carlo Reliability Assessment for Multiple Failure Region Problems Using Approximate Metamodels
Authors: Kuczera Ramon C. , Mourelatos Zissimos P. , Latcha Michael
Published: May 2009

An efficient Monte Carlo reliability assessment methodology is presented for engineering systems with multiple failure regions and potentially multiple most probable points. The method can handle implicit, nonlinear limit-state functions, with correlated or non-correlated random variables, which can be described by any probabilistic distribution. It uses a combination of approximate or “accurate-on-demand,” global and local metamodels which serve as indicators to determine the failure and safe regions. Samples close to limit states define transition regions between safe and failure domains. A clustering technique identifies all transition regions which can be in general disjoint, and local metamodels of the actual limit states are generated for each transition region. A Monte Carlo simulation calculates the probability of failure using the global and local metamodels. A robust maximin “space-filling” sampling technique is used to construct the metamodels. Also, a principal component analysis addresses the problem dimensionality making therefore, the proposed method attractive for problems with a large number of random variables. Two numerical examples highlight the accuracy and efficiency of the method.
Effect of the Actuators’ Location on Vibration Suppression Using Minimum Modal Energy Eigenstructure Assignment
Authors: Aagaah Mohammad Rastgaar , Southward Steve C. , Ahmadian Mehdi
Published: May 2009

A new Eigenstructure Assignment (ESA) method for vibration confinement of flexible structures has been developed. This method is based on finding an output feedback control gain matrix in such a way that the closed-loop eigenvectors are orthogonal to the open-loop ones. Singular Value Decomposition (SVD) is used for finding the matrix that spans the null space of the closed-loop eigenvectors. It is shown that this matrix has a unique property that can be used to regenerate the open-loop system. This method finds a coefficient vector which leads to a zero gain matrix while several coefficient vectors can be found simultaneously which are orthogonal to the open-loop coefficient vector. As a result, the closed-loop eigenvectors are orthogonal to the open-loop ones. It is shown that the modal energy of the closed loop system is reduced. Moreover, the proposed method needs neither to specify the closed-loop eigenvalues nor to define a desired set of eigenvectors. Also it is shown that if the maximum force of the actuators and the consumed energy of the actuators need to be low, actuators have to be relatively close to input. If the amplitude of vibration in isolated area has to be minimized as much as possible, the actuators need to be relatively closer to isolated area. Also the algorithm of the minimum eigenstructure assignment method has been modified to eliminate the effect of the actuators that are located on the nodes of different vibrational modes.
Photoelastic Stress Analysis Under Unconventional Loading
Authors: Dubey Venketesh N. , Grewal Gurtej S.
Published: May 2009

This paper presents use of conventional photoelastic techniques under unconventional loading situations to evaluate their efficacy in sensing applications. The loading is unconventional in the sense that low modulus photoelastic material is deformed under vertical load in the direction of light travel to induce the photoelastic effect. This is atypical of conventional methods where loading is across the light travel. Both RGB calibration and phase shifting techniques have been used to study the characteristics of fringe patterns obtained under vertical and shear loads. The results obtained under these conditions are discussed with their limitations specially when this is applied for sensing applications. Finally a case study has been conducted to analyze the foot image and conclusions drawn from this have been presented.
A Study of the Effect of m and n Coefficients of the Hertzian Contact Theory on Railroad Vehicle Dynamics
Authors: Pascal J. P. , Zaazaa Khaled E.
Published: May 2009

For the wheel/rail contact problem, the Hertz theory for two elastic bodies in contact is commonly used to determine the shape and dimensions of the contact area and the local deformation of the wheel and rail surfaces at the contact region. The shape of the contact area is assumed to be elliptical. The ratio of the contact ellipse semi-axes is equal to the ratio of two non-dimensional contact area coefficients, known as m and n coefficients. Hertz presented a table of these two coefficients, determined as a function of an angular parameter, θ. Most railroad vehicle dynamic codes use this table with online interpolation to determine the contact ellipse semi-axes. Recently, it was found that this original table may be too coarse, and that more data points are needed within the table for solving the wheel/rail contact accurately. This paper discusses the effect of the accuracy of the m and n coefficients in solving for wheel/rail contact, and demonstrates this effect with two numerical examples that show the resulting differences in the dynamic behavior of railroad vehicles dependent on this accuracy. A new table with more data points is presented that is recommended for use in railroad vehicle dynamic codes that employ the Hertzian contact for solving the wheel/rail contact interaction. This modified table was originally derived by Jean-Pierre Pascal as a part of collaborative research between the Federal Railroad Administration (FRA) and the French Ministry of Transportation.
A New Family of Large-Displacement Flexural Pivots
Authors: Yu Jingjun , Zong Guanghua , Yu Zhiwei , Bi Shusheng
Published: May 2009

This paper proposes a new family of large-displacement flexural pivots. The design in this family is derived from the conventional notch-type flexures, which are capable of high rotational precision and a compact structure. However, the proposed new flexural pivots can offer a much larger range of motion (up to 60°) compared with those old flexures. In order to construct the profile of these new flexures, a method based on large-deflection axial buckling theory was introduced to determine their initial flexible curvature profiles. In addition, the characteristic comparisons and optimizations of the proposed flexures were made using Finite Element Analysis.
The Modeling of Leaf-Type Isosceles-Trapezoidal Flexural Pivots
Authors: Pei Xu , Yu Jingjun , Zong Guanghua , Bi Shusheng
Published: May 2009

A Leaf-type Isosceles-trapezoidal Flexural (LITF) pivot can be of great practical use for designing compliant mechanisms. The analysis of load-deflection behavior for such a pivot is essential to the study on the mechanisms which are composed of the pivots. A pseudo-rigid-body model provides a simple and accurate method. Based on the analysis of a single special loaded leaf segment, a four-bar model is presented. The four-bar model is further simplified to a pin-joint model for the simpler applications. The accuracy of both models is demonstrated by comparing results to those of non-linear finite element analysis. At last, the two models are applied to analyze the cartwheel hinge as an example.
Characteristic Signal Detection Based on Re-Scaling Frequency Stochastic Resonance and Its Application in Fault Diagnosis
Authors: Leng Yong-Gang , Guo Yan , Zhou Dao-Kui
Published: May 2009

Stochastic resonance (SR) has been considered as a useful means for signal processing. However, under the condition of large parameters, for example, frequency and/or amplitude and/or noise level can be much larger than one, it is impossible to detect a weak characteristic signal submerged in strong noise or in complicated interferential components through SR. This is because SR is generally fit for small parameter signals. To realize the large parameter SR (SR-like), a new approach of re-scaling frequency stochastic resonance (RFSR) is proposed by means of a nonlinear bistable system, and hence the weak characteristic signal can be extracted. The RFSR can be considered as the observation of the SR phenomenon in different frequency-scale fields through the map of frequency-scale ratio. For non-SR status, the parameter property of two approaches of creating SR by adjusting system parameter and re-scaling frequency are investigated comparatively. The result of the investigation presents that, for large noise level, the two methods can both realize the recovery of SR status; but for large signal frequency, only the approach of re-scaling frequency can be used to recover SR status. However, if both approaches are combined to use, we can obtain a better SR effect. The experimental study of fault diagnosis for rolling bearing further demonstrates the effectiveness of the bistable RFSR approach.
An Improved Nonlinear Dynamic Model of Gear Transmission
Authors: Tang Jinyuan , Chen Siyu , Zhou Changjiang
Published: May 2009

This paper develops a new nonlinear dynamic model of gear transmission on the basis of combining friction, gear mesh stiffness and backlash. In calculating friction force, the dynamic distribution of the load along the actual line of action is taken into consideration. A new period-enlargement method is proposed to set up a friction force model and a gear meshing stiffness model. The non-linear dynamic model is a non-autonomous system. Compared with the former models, the damping coefficient and stiff coefficient in this model developed by the period enlargement method is a periodic function with the same period. Thus it is easier to apply EM (energy method) or other methods for finding the approximate analytical solution of the gear transmission dynamic equations combining with time-varying damping and stiffness. Frequency response function of the nonlinear dynamic model is obtained by using harmonic balance method. Compared the analytic and numerical results of the improved nonlinear model with that of the nonlinear models in the published papers, it is shown that: (a) the former numerical simulation techniques may not work or may result in misleading answers; (b) the coexistence of several different periodic solutions and various impacts are the same with the results in formerly published papers when gear parameters are the same. Finally, the accurate solutions of all three regimes are combined to obtain the overall frequency response of the gear pair.
Spatial Exact Actuation of Flexible Deep Double-Curvature Shells
Authors: Yue Hong-Hao , Gao Xiao-Ying , Ren Bing-Yin , Tzou Horn-Sen
Published: May 2009

Deep double-curvature shells are commonly used as key components in many advanced aerospace structures and mechanical systems, e.g., nozzles, injectors, horns, rocket fairings. Spatially distributed micro-actuation of a laminated flexible deep double curvature shell is investigated and its control effectiveness is evaluated in this study. Dynamic equations of the smart double curvature shell system are presented and modal control forces of spatial segmented piezoelectric actuators are carried out based on a new set of assumed mode shape functions with free boundary condition. Using these assumed mode shape functions, mode shapes of a free-floating deep shell are illustrated. Finally, via numerical simulation, control effectiveness of distributed actuator patches with respect to various natural modes, actuator locations and other factors which influence precision control and active actuation behavior of flexible deep double curvature shell structronic systems is evaluated.
Non Contact Precision Actuation and Optimal Actuator Placement of Hybrid Photostrictive Beam Structronic Systems
Authors: Yue Hong-Hao , Deng Zong-Quan , Tzou Horn-Sen
Published: May 2009

Non-contact wireless actuation offers many advantages to precision control, as compared with conventional hard-wired actuation mechanisms. High-energy laser or ultraviolet lights irradiating on photostrictive materials can induce a photodeformation process involving two fundamental effects: 1) the photovoltaic effect and 2) the converse piezoelectric effect. This photodeformation process transforms photonic energy to mechanical strain/stress that can be directly used for actuation and control applications. With specific design configurations, the photodeformation process of photostrictive actuators can induce various control forces and moments applied to precision manipulation and control of mechatronic and structronic systems. In this study, fundamental photodeformation coupling mechanisms among photo-thermo-electromechanical/control fields are investigated and parametric evaluation of various design parameters of a hybrid photostrictive/elastic beam is conducted. A mathematical model for a laminated beam with segmented photostrictive actuators is defined, followed by photodeformation induced modal control forces and moments of segmented actuators. Characteristics of actuation and control effectiveness of distributed photostrictive actuators at various locations, natural modes and illumination intensities are analyzed in case studies. The most effective actuator location(s) for controlling the first four beam modes are illustrated. Finally, with scheduling light irradiations on various photostrictive actuators, one can control multiple beam modes, allowed by control electronics and material response.
The Effect of High Order Non-Linearities on Sub-Harmonic Excitation With Parallel Plate Capacitive Actuators
Authors: Trusov Alexander A. , Shkel Andrei M.
Published: May 2009

Electrostatic actuation of motion is commonly used in resonant MEMS. Drive signal feed-through is undesirable as it masks the detection signal. This paper reports analysis and demonstration of a resonant motion excitation scheme, which uses a combination of a DC bias with a sinusoidal AC voltage, frequency of which is twice of the mechanical resonant frequency. This configuration is experimentally demonstrated to excite a gyroscope with a parallel plate drive capacitor into high amplitude periodic vibrations. The feed-through has a frequency higher than the main motional harmonic and thus can be eliminated by simple low pass filtering. Full nonlinear dynamics along with several higher-order approximations are considered. Analysis of the effect of the approximation order on the frequency response accuracy shows that the complete nonlinear equation should be used for modeling of high amplitude actuation. Two distinct types of frequency responses are examined as functions of driving AC and DC voltages and damping.
Application of Broadband Nonlinear Targeted Energy Transfers to Seismic Mitigation
Authors: Nucera Francesco , McFarland D. Michael , Bergman Lawrence A. , Vakakis Alexander F.
Published: May 2009

We show that it is possible to successfully apply the concept of nonlinear targeted energy transfer (TET) to seismic protection of structures. We consider a three-story shear frame structure under seismic excitation, modeled as a three degree-of freedom (DOF) system. We consider four historic earthquakes as seismic excitation. The seismic mitigation is achieved by connecting a vibro-impact attachment (termed a vibro-impact NES – VI NES) applied to the top floor of the structure. In order to assess the robustness of the VI NES, the NES parameters were optimized for a specific seismic excitation (Kobe), and then tested against the three other seismic excitations to demonstrate effectiveness of the NES for these cases as well.
Spring-Mass Jumping of Underactuated Biped Robots
Authors: Tamaddoni Seyed Hossein , Alasty Aria , Meghdari Ali , Sohrabpour Saeed , Salarieh Hassan
Published: May 2009

In many types of fast animal and human locomotion an almost sinusoidal pattern is observed for the ground reaction force; therefore, a simple spring-mass model can approximate the generally observed force pattern. The adjustment of the leg during running, jumping or hopping is addressed using a spring-mass model with a fixed landing angle of attack with the objective of obtaining periodic movement patterns. We found that this self-stabilizing spring-mass model can be applied as a movement criterion for biped joints’ trajectory generation in jumping. To create desired velocity and stride-to-stride length, a synchronization method was applied between biped nonlinear dynamics and spring-mass dynamics as slave and master dynamics, respectively. The results of performed simulations show that while our model lacks the flight phase and impact model for a complete cycle of jumping process, this technique might become of great use in the future’s biped path planning which we call it “dynamic path planning”.
Adjoint Fractional Differential Expressions and Operators
Authors: Podlubny Igor , Chen YangQuan
Published: May 2009

In this article we present the notions of adjoint differential expressions for fractional-order differential expressions, adjoint boundary conditions for fractional differential equations, and adjoint fractional-order operators. These notions are based on new formulas obtained for various types of fractional derivatives. The introduced notions can be used in many fields of modelling and control of real dynamical systems and processes.
Correspondences Matching on 3D Mesh Models
Authors: Li Samuel Sai-Man , Wang Charlie C. L. , Hui Kin-Chuen
Published: May 2009

This paper presents an approach to match correspondences on 3D meshes, which is an important step for the design automation of customized freeform objects. For a given template model with a set of anchor points defined (knots of semantic features), we identify the corresponding points on the target model by minimizing the sum of differences by a series of transformation regardless of their differences in postures, scales and/or positions. The basic idea of our algorithm is to transform the target model to the template model iteratively. Once the correspondences between the surface points on the target model and the template are determined, we have essentially found the semantic features on the target model. We achieve this goal by four major transformations: 1) Multi-Dimensional Scaling (MDS), 2) Orientation Alignment, 3) Anchor Points Based Matching, and 4) Matching Refinement. The proposed method has been tested on a series of real human bodies to re-locate feature anchor points that are defined on the template model.
Mechanical Fourier Series Generator: Theory and Practice
Authors: Bucher Izhak , Avivi Gal
Published: May 2009

In this paper the theory behind a Mechanical device that lends itself to producing periodic response patterns under small excitation levels is described. It turns out that certain symmetry features that are presented here are useful in the design of the desired Mechanical device. It will be shown mathematically that the compliance of the structure can be made high at frequencies that are integer multiples of a basic frequency while the compliance is zero at other frequencies where no energy is to be conveyed the oscillating element. As a result, this structure lends itself to producing periodic oscilations under small excitation levels.
Overlapped Grouping Genetic Algorithm for Optimization of Reels Cutting Planning Problems
Authors: Abd El-Hady Waleed M. A. , Metwalli Sayed M.
Published: May 2009

The optimization of Reel-Cutting Planning Problem “RCPP” is concerned with finding the best selection of a strategic reel set and the corresponding tactical cutting lengths “sheets set”, from a wide feasible space, to be used in producing a set of blanks. The problem is classified as a weighted multi objectives two-staged guillotine two-dimensional Cutting Stock Problem “CSP” of Dyckoff’s type 2/V/D/M. This paper presents a tailored metaheuristic solution using grouping genetic algorithms (GGAs). Overlapped Chromosome representation is newly developed for optimization. Developed also an especial database to create the cutting patterns of resulting solution. The objective in this application is to minimize the total cost, which includes the total material cost required to achieve a lot size, the cost of selecting reels set size, and the cost of cutting lengths from these reels “sheet set size”. An industrial case study is considered. The attained optimum cutting plan provides an overall improvement of 4.3% over the current professional cutting plan. The reduction in the reel set size is from five to an optimum of three reels. The developed procedure also provides reduction of trim loss of 4% over the current plan. The developed approach also proved to be faster than the currently used techniques.
Formulation of Three-Dimensional Rigid-Flexible Multibody Systems
Authors: Garci´a-Vallejo Daniel , Escalona Jose´ L. , Mayo Juana M. , Domi´nguez Jaime
Published: May 2009

Multibody systems generally contain solids the deformations of which are appreciable and which decisively influence the dynamics of the system. These solids have to be modeled by means of special formulations for flexible solids. At the same time, other solids are of such a high stiffness that they may be considered rigid, which simplifies their modeling. For these reasons, for a rigid-flexible multibody system, two types of formulations co-exist in the equations of the system. Among the different possibilities provided in bibliography on the material, the formulation in natural coordinates and the formulation in absolute nodal coordinates are utilized in this article to model the rigid and flexible solids, respectively. This article contains a mixed formulation based on the possibility of sharing coordinates between a rigid solid and a flexible solid. In addition, the fact that the matrix of the global mass of the system is shown to be constant and that many of the constraint equations obtained upon utilizing these formulations are linear and can be eliminated. In this work, the formulation presented is utilized to simulate a mechanism with both rigid and flexible components.
A Novel Optimization Approach to Generate Physiological Human Walking Patterns
Authors: Ackermann Marko
Published: May 2009

Dynamic simulation of the musculoskeletal system is increasingly being used to study human normal and pathological walking. The common approach to predict walking patterns is based on the assumption that the central nervous system minimizes an intrinsic performance criterion. For instance, during walking, the energy expenditure per unit of distance traveled was shown to play a key role. The resulting optimal control problem is almost exclusively solved by the so-called dynamic optimization. Dynamic optimization relies on the parameterization of neural excitations using nodal values serving as optimization variables. The reconstructed neural excitations are then used to numerically integrate the differential equations describing the dynamics of the musculoskeletal system. This approach has been successfully applied to predict salient normal walking patterns, including muscle coordination and energy expenditure. In spite of the growing use of dynamic optimization, the extremely high computational effort arising from the several numerical integrations of the large-scale state equations required prevents it from being more widely applied, e.g., for bioassistive devices. Approaches based on inverse dynamics have the potential to reduce the high computation effort by avoiding the necessity of numerically integrating the state equations, but have been poorly explored in biomechanics. The development of an inverse dynamics-based approach to generate near-optimal human walking patterns that deals with the overdeterminacy of muscle actuation in conjunction with Hill-type muscle models widely used in biomechanics is proposed in this paper. The approach is based on the parameterization of the motion and muscle forces. The neural excitations are obtained by inverting the muscle contraction and activation dynamics. The compatibility between motion and muscle forces is guaranteed by checking the fulfillment of the equations of motion of the skeletal system at control points. The approach is implemented and human normal and pathological gaits are generated and applied to the design of transtibial prostheses.
Chaos Control of a Sprott Circuit Using Non-Linear Delayed Feedback Control Via Sliding Mode
Authors: Sadeghian Hoda , Merat Kaveh , Salarieh Hassan , Alasty Aria
Published: May 2009

In this paper a nonlinear delayed feedback control is proposed to control chaos in a nonlinear electrical circuit which is known as Sprott circuit. The chaotic behavior of the system is suppressed by stabilizing one of its first order Unstable Periodic Orbits (UPOs). Firstly, the system parameters assumed to be known, and a nonlinear delayed feedback control is designed to stabilize the UPO of the system. Then the sliding mode scheme of the proposed controller is presented in presence of model parameter uncertainties. The effectiveness of the presented methods is numerically investigated by stabilizing the unstable first order periodic orbit and is compared with a typical linear delayed feedback control. Simulation results show the high performance of the methods for chaos elimination in Sprott circuit.
On the Synchronization of a Class of Sprott Circuits Using Variable Structure Controller
Authors: Merat Kaveh , Sadeghian Hoda , Salarieh Hassan , Alasty Aria
Published: May 2009

In this paper the synchronization of a class of nonlinear chaotic circuits known as Sprott Circuits is studied. The Synchronization is obtained using a variable structure method based on sliding mode control with time varying sliding surface and variable boundary layer in presence of external disturbance and parametric uncertainties. The simulation is presented to show the effectiveness of this method. The results show the high quality and good performance of the method presented in the paper for synchronization of different drive-response chaotic Sprott circuits.
Optimal Configuration of a 4-DOF Dual-Arm Cam-Lock Manipulator
Authors: Ghaemi Osgouie Kambiz , Meghdari Ali , Sohrabpour Saeed , Salmani Jelodar Mehdi
Published: May 2009

The Dual-Arm Cam-Lock (DACL) robot manipulators are reconfigurable arms formed by two parallel cooperative manipulators. Some of their joints may lock into each other. Therefore, the arms normally operate redundantly. However, when higher structural stiffness is needed these two arms can lock into each other in specific joints and loose some degrees of freedom. In this paper, the dynamics of the DACL robot is discussed and parametrically formulated. On the other hand, the criteria and implementation of genetic algorithm (GA) to optimize the configuration of DACL robot manipulators at a specific point with the objective to maximize the cooperatively applicable task-space force in a desired direction are addressed. To obtain a more efficient process, an initial population is generated satisfying the geometrical constraints of the planar arms.
Knee Joint Modeling
Authors: Caruntu Dumitru I.
Published: May 2009

This is a review paper on human knee joint biomechanics modeling. Dynamic models and quasi-static models reported lately in the literature are included in this survey. Anatomical surface representation, contact modeling, ligament structure, and solution algorithm of these models are reviewed.
Transverse Vibrations of Rectangular Plates of Linearly Varying Thickness
Authors: Caruntu Dumitru I. , Stroe Ion
Published: May 2009

This paper presents an approach for finding the solution of partial differential equation describing the motion of transverse vibrations of rectangular plates of unidirectional linear varying thickness. The original partial differential equation consists of three operators: fourth-order spatial-dependent, second-order spatial-dependent, and second-order time-dependent. Using the method of multiple scales, the partial differential equation has been reduced to two simpler partial differential equations which can be analytically solved and which represent two levels of approximation. The first partial differential equation was a homogeneous equation and consisted of two operators, the fourth-order spatial-dependent and second-order time-dependent. The solution of this equation was found using the factorization method. This solution was zeroth-order approximation of the exact solution. The second partial differential equation was an inhomogeneous equation. The solution of this equation was also found and led to first-order approximation of the exact solution of the original problem. This way the first-order approximations of the natural frequencies and mode shapes are found. Various boundary conditions can be considered. The influence of Poisson’s ratio on the natural frequencies and mode shapes could be further studied using the approximations reported here. This approach can be extended to nonlinear, and/or forced vibrations.
Enforcing Constraints in Multibody Systems: A Review
Authors: Bauchau Olivier A. , Laulusa Andre´
Published: May 2009

A hallmark of multibody dynamics is that most formulations involve a number of constraints. Typically, when redundant generalized coordinates are used, equations of motion are simpler to derive but constraint equations are present. While the dynamic behavior of constrained systems is well understood, the numerical solution of the resulting equations, potentially of differential-algebraic nature, remains problematic. Many different approaches have been proposed over the years, all presenting advantages and drawbacks: the sheer number and variety of methods that have been proposed indicate the difficulty of the problem. A cursory survey of the literature reveals that the various methods fall within broad categories sharing common theoretical foundations. This paper summarizes the theoretical foundations to the enforcement in constraints in multibody dynamics problems. Next, methods based on the use of Lagrange’s equation of the first kind, which are index-3 differential algebraic equations are reviewed. Methods leading to a minimum set of equations are discussed; in view of the numerical difficulties associated with index-3 approaches, reduction to a minimum set is often performed, leading to a number of practical algorithms using methods developed for ordinary differential equations. Finally, alternative approaches to dealing with high index differential algebraic equations, based on index reduction techniques, are reviewed and discussed. Constraint violation stabilization techniques that have been developed to control constraint drift are also reviewed. These techniques are used in conjunction with algorithms that do not exactly enforce the constraints. Control theory forms the basis for a number of these methods. Penalty based techniques have also been developed, but the augmented Lagrangian formulation presents a more solid theoretical foundation. In contrast to constraint violation stabilization techniques, constraint violation elimination techniques enforce exact satisfaction of the constraints, at least to machine accuracy. Finally, as the finite element method has gained popularity for the solution of multibody systems, new techniques for the enforcement of constraints has been developed in that framework. The goal of this paper is to review the features of these methods, assess their accuracy and efficiency, underline the relationship among the methods, and recommend approaches that seem to perform better than others.
Nonlinear Dynamics in Drilling and Boring Operations Assisted by Low Frequency Vibration
Authors: Moraru George F.
Published: May 2009

The nonlinear dynamics of the drilling process assisted by self-excited axial vibrations is analyzed. Models are developed and discussed, including regenerative effect and various phenomena contributing to the process damping in drilling and boring operations. Stability and bifurcation analysis, using several assumptions on the damping in the cutting process, are carried out using linear analysis tools or simulations. A simple predictive model based on a harmonic balance method is presented. Behavior charts are constructed using simulations. Hypothesis on the nature of the process damping and nonlinear behavior of the machining system are proved by experiments. A possible application to the gundrilling boring process in aircraft drilling and assembly process is presented.