Mechanical System Research Papers - Academia.edu (original) (raw)

The ability to improve a disk file's access-time performance is severely limited by an inverse fourth-power increase in actuator-power dissipation. Two areas are germane to the actuator-power problem: the design of the actuator coil and the design of the control trajectory. Design considerations for optimal solutions in both of these areas are presented.

- by
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- Engineering, Computer Science, Design, Optimal Control

This paper presents a hybrid approach to cope with deadzone types of nonlinearities, which are often present in many mechanical systems. If the effect of the deadzone is not directly considered in the control design, it may cause unwanted performance loss and may lead to chattering around the deadzone limits. It will be shown that the deadzone can be naturally modeled using piecewise affine (PWA) models, and that such models are suitable for design of control policies which take the deadzone behavior into account. In this paper, the controller design scheme is based on the so-called minimumtime principle. It is shown that such design task can be formulated as a model predictive control (MPC) problem, where the solution takes a form of a look-up table. It will be presented that such table can be evaluated in real-time, hence allowing to apply the concept of MPC to devices with very fast sampling rates. Experimental results show that the MPC controller based on a PWA description of the deadzone nonlinearity meets the desired goals.

- by Miroslav Fikar
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- Mechanical Engineering, Applied Mathematics, Model Predictive Control, Modeling

Building energy contributes to a significant fraction of the total energy cost during all processes of its life span. Buildings are dynamic, non-linear systems with a large number of components that strongly influence total building energy consumption. Therefore, it is challenging to find an optimal combination of building components to minimize the building life cycle cost (LCC). This paper proposes a framework of building systems optimization designed to minimize life cycle cost by combining optimization algorithms and a comprehensive building life cycle cost model. A case study based on an office building demonstrates that annual energy costs and initial construction costs are major contributors to the whole building life cycle cost. A case study of an office building shows that when the building lifespan is greater than 30 years, the cumulative annual energy consumption cost is projected to be higher than the initial construction cost. Finally, optimal component combinations vary with different lengths of a building's life span. For instance, wood window frames become the optimal component for less energy and maintenance cost when the building lifespan changes from 14 to 60 years.

- by Jelena Srebric
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- Engineering, Energy Efficiency Buildings, Optimization, Mechanical System

In this paper are presented the power losses and sources of their occurrence in worm gear boxes. These are the losses that occur in the coupling of worm teeth and worm gear, losses in bearings, seals and oil churning power losses in the transmission. When the operation of worm gearing is characterized by line contact of coupled elements which is accompanied by significant sliding, the highest value have the power losses in the worm and worm gear coupling compared to other losses in gearing. Among other things, in the paper also presents the expressions that are used for calculation of individual power losses and efficiency of the gearing. The size of the losses primarily depends on the type of coupled material and geometry of worm pair, circumferential velocity (input rotational speed), the type and viscosity of lubricating oil, load, worm shape, and temperature and so on. The paper also deals with the influence of different factors on power losses and efficiency. As the efficiency of the worm pair is significantly lower compared to other types of gear pairs, the appropriate combination of geometric parameters and materials of worm and worm gear, lubrication and working conditions can significantly affect its increase.

- by Blaza Stojanovic
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- Mechanical Engineering, Power System, Tribology (Engineering), Lubrication

Course is intended for Undergraduate Mechanical Engineering students involving on Understanding Kinematics of Mechanisms, simple mechanism study, Velocity and acceleration analysis of mechanisms, Problem solving on Belt drives, Rope drives, Using Graphical analysis of generating Cam Profiles, Study of all types of gear drives and problem solving on spur gears, study on control and regulation of Governors.

- by Kiran K U M A R Kudumula
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- Mechanical Engineering, Robotics, Design, Computational Mechanics
- by Kiran K U M A R Kudumula
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- Mechanical Engineering, Design, Instructional Design, Curriculum Design

All quadruped robots deal with the same challenge of motion generation. A specific architecture of a motion generator for stable gaits is proposed which can be easily adapted to the needs of various four-legged walking machines. Kinematic and dynamic analysis of quadruped robot are realized for walking and running gaits in this study. This paper presents the development of robotic gait pattern for motion of the quadruped robot on natural terrain containing of irregular and rough terrain. The mechanical system consists of an acrylic torso frame and legs. The legs are designed based on the results of kinematic calculations which determine the length of the linkages, capability of each leg to generate force and robotic workspace. The quadruped robot is developed with 3DOF on all its legs. The various dynamic analysis done includes feet force distributions, energy consumption and dynamic stability, considering the inertial effects of the legs on the system. The locomotion of the robot is being controlled by controlling the angular rotation of the servo motors placed on the joints. The Inverse kinematics solutions are derived for the developed structure using analytical method. Computer simulations have been carried out to test the effectiveness of the developed model and to determine the maximum velocity and acceleration by each of the links.

- by IAEME Publication
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- Gait, Mechanical System, Kinematic Analysis

Air transportation is one of the most preferred types of transportation for many reasons. However, to minimize the risk of accidents with developing technology, investigations and studies are carried out by many organizations. While the main causes of accidents in the first years of aviation were due to mechanical reasons, accidents caused by mechanical reasons have been replaced by an increase in the number of aircraft accidents caused by human-induced errors which depend on the increasing manpower with the developing technology. Nowadays, "Aviation" has become a high level of technical, administrative, and even technological operations. This was made possible by the introduction and production of larger and faster aircraft, which largely includes advanced information management technologies. From an industrial point of view, the fact that aircraft can carry people, cargo, mail, and similar at a more affordable price and in a shorter time has made aviation an important sectoral value. Competition has increased with the increase of aviation companies; therefore, businesses that tend to give overload to employees for the sake of gaining more can cause aircraft accidents. Increased traffic volume and demand for air transportation mean risks and increases in air crashes. In this study, human-induced errors and mechanical system errors, which cause air crashes are mentioned and the statistical analysis of air crashes between the years 1918-2019 is examined.

This work is on the aerodynamics design of the body and frame of a motor tricycle using SolidWorks 2011 modeling system. Its Computational Fluid Dynamics (CFD) feature was used to run simulation tests at a target speed of 150 km/h to evaluate the aerodynamic performance of the tricycle. Simulation results presented shows that lift and drag forces are diminished considerably and that 170 km/h is the maximum speed to be traveled by the tricycle for a smooth and stable ride. Also, the design reduced drastically the effects of lift and drag forces, increased the tricycle’s stability, traction and performance as well as minimized the weight of the tricycle as a result of the use of high performance to mass ratio materials such as carbon fiber for the body and alloy steel for the frame and rims.

- by Giwa R Iziomo
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- Mechanical Engineering, Computational Fluid Dynamics, Fluid Mechanics, Turbulence

Cheetahs and beetles run, dolphins and salmon swim, and bees and birds fly with grace and economy surpassing our technology. Evolution has shaped the breathtaking abilities of animals, leaving us the challenge of reconstructing their targets of control and mechanisms of dexterity. In this review we explore a corner of this fascinating world. We describe mathematical models for legged animal locomotion, focusing on rapidly running insects and highlighting past achievements and challenges that remain. Newtonian body-limb dynamics are most naturally formulated as piecewise-holonomic rigid body mechanical systems, whose constraints change as legs touch down or lift off. Central pattern generators and proprioceptive sensing require models of spiking neurons and simplified phase oscillator descriptions of ensembles of them. A full neuromechanical model of a running animal requires integration of these elements, along with proprioceptive feedback and models of goal-oriented sensing, planning, and learning. We outline relevant background material from biomechanics and neurobiology, explain key properties of the hybrid dynamical systems that underlie legged locomotion models, and provide numerous examples of such models, from the simplest, completely soluble "peg-leg walker" to complex neuromuscular subsystems that are yet to be assembled into models of behaving animals. This final integration in a tractable and illuminating model is an outstanding challenge.

- by Philip Holmes
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- Robotics, Applied Mathematics, Biomechanics, Control

Since the discovery of hydrogen in the 18 th century by Henry Cavendish, Scientists and Engineers have put its properties to the test in every area of our life. But there is one area that seems a little bit under explored, this field is its application in the fuel cell technology. Fueled by this realization, I designed a self-sustaining power plant which generates its power entirely from the world's most abundant element, Hydrogen and solar energy. Solar is the most abundant form of energy the earth receives annually. It is estimated that the African continent receives some 60,000,000 TWh/year of energy from the sun making it the most solar rich continent globally. There are solar farms across Africa but they are as good as the sun is shining, without a practical storage place for the power they generate during the day hence they are not common. There are therefore not practical to sustain the grid. Modern batteries technology can only offer a limited storage capacity. The H.S.P.P stores power in the form of hydrogen liquid which gets used when the sun is not shining. H.S.P.P will have a solar farm which uses the sun's light energy to generate electrical energy in DC form which is transported to the Power Management Unit (PMU) which regulates and stabilizes the DC power such that it can be divided to take two paths. The PMS will make sure that out of the power generated by the solar modules a fixed quantity of energy is channeled to the invertor to covert the DC into AC to feed into the grid. The remaining power will then be carried through high current cables to the Elecrolyser which will break water in hydrogen and oxygen. The hydrogen gas produce will be pumped under high pressure and pass through a Liquefier which will convert it into a liquid which is then directed through pipes to the storage tanks. The PMU will be equipped with the state of the art software which monitors power levels from the solar field against the power its feeding to the grid, such that its always feeding a constant amount of power to the grid. This software is smart enough switch-on the Hydrogen Fuel cells to start generating power when the power from the solar modules drops below a certain threshold. This ensures that the plant is always feeding the grid the required amount of power. The oxygen produced is liquefied and distributed to hospitals and emergency centers and the excess is released into the environment. The PMU is the heart of the H.S.P plant because its responsible for monitoring the electrolysis of water and the safe storage of the Hydrogen gas. Written by T Chigwagwa

- by Talent Chigwagwa
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- Green energy technology, Mechanical System

The dynamics equations governing the motion of mechanical systems composed of rigid bodies coupled by holonomic and nonholonomic constraints are derived. The underlying method is based on a natural orthogonal complement of the matrix associated with the velocity constraint equations written in linear homogeneous form. The method is applied to the classical example of a rolling disk and an application to a 2-dof Automatic Guided Vehicle is outlined.

- by Jorge Angeles
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- Mechanical Engineering, Civil Engineering, Aerospace Engineering, Applied Mechanics

| Wafer direct bonding refers to the process of adhesion of two flat mirror-polished wafers without using any intermediate gluing layers in ambient air or vacuum at room temperature. The adhesion of the two wafers occurs due to attractive long range van der Waals or hydrogen bonding forces. At room temperature the bonding energy of the interface is low and higher temperature annealing of the bonded wafer pairs has to be carried out to enhance the bonding energy. In this paper, we describe the prerequisites for the wafer-bonding process to occur and the methods to prepare the suitable surfaces for wafer bonding. The characterization techniques to assess the quality of the bonded interfaces and to measure the bonding energy are presented. Next, the applications of wafer direct bonding in the fabrication of novel engineered substrates such as Bsilicon-on-insulator[ and other Bon-insulator[ substrates are detailed. These novel sub-strates, often called hybrid substrates, are fabricated using wafer bonding and layer splitting via a high dose hydrogen/ helium implantation and subsequent annealing. The specifics of this process, also known as the smart-cut process, are introduced. Finally, the role of wafer bonding in future nanotechnology applications such as nanotransistor fabrication, three-dimensional integration for high-performance micro/ nanoelectronics, nanotemplates based on twist bonding, and nano-electro-mechanical systems is discussed. KEYWORDS | Bonded interface; bonding energy; complementary metal-oxide semiconductor (CMOS); hybrid substrates; layer transfer; micro-/ nano-electro-mechnical systems (M/NEMS); micro/nanoelectronics; silicon-on-insulator (SOI); smart cut; strained silicon-on-insulator (sSOI); twist bonding; wafer direct bonding Manuscript

- by Rajendra Singh
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- Biomedical Engineering, Nanoelectronics, Nanotechnology, Adhesion

- by Talent Chigwagwa
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- Green Technology, Mechanical System

Algorithms for real-time, embedded optimization need to run within tight computational times, and preferably on embedded control hardware for which only limited computational power and memory is available. A computationally demanding step of these algorithms is the model simulation with sensitivity generation. This paper presents an implementation of code generation for Implicit Runge-Kutta (IRK) methods with efficient sensitivity generation, which outperforms other solvers for the targeted applications. The focus of this paper will be on the extension of the proposed tool to the integration of index-1 Differential Algebraic Equations (DAE), and continuous output functions, which are crucial for e.g. performing sensor fusion with measurements provided at very high sampling rates. The new tool is provided with a powerful MATLAB interface. It is illustrated in simulation for the trajectory estimation of a mechanical system modeled by complex Differential-Algebraic equations, using sensor information provided at fast, multi-rate sampling frequencies.

- by Rien Quirynen
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- Optimization, Differential Algebraic Equations, Estimation, Code Generation

The inverted pendulum has been used as a benchmark for motivating the study of nonlinear control techniques. We propose a simple controller for balancing the inverted pendulum and raise it to its upper equilibrium position while the cart displacement is brought to zero. The control strategy is based on an energy approach of the cart and pendulum system.

- by Dan Block
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- Mechanical Engineering, Applied Mathematics, Control Theory, Vibration Control

Rapport de Recherche INRIA N 791, F evrier 1988 1 1 PARALLEL MANIPULATOR 3 1 A lot of calculation (in particular the results presented in the Appendices) has been obtained with the aid of MACSYMA [26], a large symbolic manipulation... more

- by Jean-Pierre Merlet
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- Mechanical Engineering, Robotics, Geometry, Singularity

This paper proposes a new general framework, i.e. hybrid modeling, to model dry friction systems. The proposed hybrid model has two modes (states): one models the system sliding, the second the system sticking. The model's main advantage is the adaptation capability to observable phenomena. It is shown for the most common behaviors encountered experimentally and comparisons with other models presented in the literature are carried out. The models and methods of parameters identification of the literature are generally validated experimentally on system with sensors and actuators of high precision. This paper focuses on modeling and identifying complex mechanical system with low resolution sensors. The presented theoretical work is validated experimentally on a clutchby-wire.

- by Damien Koenig and +1
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- Mechanical Engineering, Applied Mathematics, System Identification, Modeling

Fault detection and diagnosis in mechanical systems during their time-varying nonstationary operation is one of the most challenging issues. In the last two decades or so researches have noticed that machines work in nonstationary load/speed conditions during their normal operation. Diagnostic features for gearboxes were found to be load dependent. This was experimentally confirmed by a smearing effect in the spectrum.

- by Walter Bartelmus and +1
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- Mechanical Engineering, Civil Engineering, Signal Processing, Modeling

N ous allons nous interesser dans ce dossier a la conception des humanoides de synthese dans un contexte temps-reel pour la realite virtuelle. On distingue deux grandes classes necessitant la mise en oeuvre d'humanoides en realite virtuelle: ― la representation de l'utilisateur au sein meme de l'environnement virtuel a l'aide d'une entite appelee avatar; ― la representation d'agents autonomes independants de l'utilisateur, necessaires a la simulation d'environnements complexes impliquant plusieurs personnes, voire une population. Un certain nombre de domaines d'application ont besoin d'agents autonomes independants. Citons la simulation d'environnements architecturaux et urbains, la formation professionnelle, le traitement de pathologies en psychotherapie et les applications ludiques, educatives et artistiques. Ces humanoide doivent etre dotes d'une incarnation, de capacites de perception, de traitement de l'information, de prise de decision et d'action. Au plus bas niveau, les humanoides se deplacent, utilisent des objets, interagissent entre eux et avec les elements du decor. Il s'agit ici de generer des modeles de mouvement et de coordonner de facon realiste les differents mouvements possibles: c'est la couche motrice. Au niveau intermediaire, les humanoides jouent la scene qui doit permettre l'accomplissement de l'action. Leurs comportements, leur gestuelle, leur expression physique au sens large doivent etre en adequation avec l'atmosphere, les dialogues, le decor: c'est la couche theâtrale. Au niveau le plus haut, beneficier des avantages de l'autonomie des agents et de leur controle partiel, necessite de definir la notion de chef d'orchestre qui va suivre et influer sur l'evolution du monde virtuel. Il determine entre autre les roles et les actions que doivent effectuer les acteurs, a partir d'un scenario capable, entre autres, de reagir aux actions humaines: c'est la couche orchestrale. Ce dernier niveau n'est pas presente ici car non specifique a l'humain virtuel. Ce dossier se concentre sur les approches de modelisation et de controle temps-reel des mouvements et des comportements d'humains virtuels. D'autres aspects complementaires, tels que le rendu realiste, l'animation des vetements et de la chevelure, ou encore l'animation faciale, sont necessaires pour rendre credibles ces humanoides de synthese mais ne seront pas traites ici. La contrainte du temps-reel est particulierement severe pour un systeme mecanique aussi complexe, c'est pourquoi sa modelisation repose sur de nombreuses simplifications selon l'usage qu'il est prevu d'en faire. Ce dossier est structure de la maniere suivante. Nous rappelons tout d'abord les grandes lignes du standard H-ANIM offrant un ensemble de conventions pour la representation du squelette et du mouvement. Nous presentons ensuite deux grandes familles de techniques d'animation, les cinematiques directe et inverse, avant d'evoquer la capture temps-reel du mouvement et son adaptation pour resoudre de nouvelles contraintes. Une reflexion sur l'integration de la dynamique clot la premiere partie. La seconde partie traite des mecanismes permettant de mettre en oeuvre une autonomie croissante au sein des entites animees. Nous y presentons tout d'abord les modeles de comportements reactifs synthetises par la boucle de perception-decision-action. Suivent les modeles de comportement cognitifs, collectifs et sociaux.

- by Stéphane Donikian
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- Philosophy, Art, Animation, Computer Animation

This paper presents design, modelling and system identification of a laboratory test apparatus that has been constructed to experimentally validate the concepts of anomaly detection in complex mechanical systems. The test apparatus is designed to be complex in itself due to partially correlated interactions amongst its individual components and functional modules. The experiments are conducted on the test apparatus to represent operations of mechanical systems where both dynamic performance and structural durability are critical.

- by Amol M Khatkhate
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- Applied Mathematics, System Identification, Real Time Computing, Time Series

A portable device to quantitatively measure the degree of spasticity in the ankle of patients was developed using a computer-controlled system consisting of a pedal which is rotated through the desired range by a mechanical system driven by a d.c. stepper motor. The resistive torque from the spastic ankle is measured with a sensor system consisting of strain gauges placed in a transducer shaft which rotates the pedal. The data are retrieved by a software triggered An, board, and the results are graphed. This device, which is yet to be clinically tested, will enable therapists to quantitatively measure the degree of spasticity in patients and record small changes in their performance.

- by Cecil Hershler
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- Biomechanics, Transducers, Muscle, Mechanical systems

In this paper, experimental investigations are carried out by end milling process on hardened tool steel, Impax Hi Hard (Hardness 55 HRC) a newly developed tool steel material used by tool and die making industries. Experiments are performed with an aim to study performance investigations of machining parameters such as cutting speed, feed, depth of cut and width of cut with consideration of multiple responses viz. volume of material removed, tool wear, tool life and surface finish to evaluate the performance of PVD coated carbide inserts and ball end mill cutters. It has been observed through scanning electron microscope, X-ray diffraction technique (EDX) that chipping and adhesion are active tool wear mechanisms and saw-toothed chips are formed while machining of Impax Hi Hard steel. It is also noticed out that tool life is not enhanced while machining with minimum quantity lubricant than dry machining. From the investigations, it is observed that hard machining can be considered as an alternative to grinding and EDM, traditional methods of machining difficult-to-machine materials i.e. hardened steel with hardness greater than 50 HRC with a scope of improved productivity, increased flexibility, decreased capital expenses and reduced environmental waste.

- by Bala Murugan
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- Tool wear, Mechanical System, Tool Development, Scanning Electron Microscope

This paper focuses on the primary development of novel analytical and numerical studies for the smart plate structure due to the effects of point mass locations, dynamic motions, and network segmentations. Instead of the alternative capabilities in active and passive control systems, the technical application of the present work can also be found in the energy harvesting system. The simplified theoretical studies have shown the simultaneous derivations with full variational parameters. In particular, these parameters consist of the mechanical and electromechanical systems, the mixed series-parallel electrode segment connection, and the harvesting circuit. The mechanical system parameters include elasticity with stress-strain relation, internal damping stress, air damping, and dynamics of the integrated physical system. The electromechanical system parameters include electrical displacement, electrical stress and electric-polarity field of the piezoelectricity. For the analytical approach, the governing equations of motion based on the Gram-Schmidt iterative process have been derived using the extended Hamiltonian principle and Ritz method-based weak form system. For validation, the elec-tromechanical finite element equations reduced from the extended Lagrange's equations have been developed using electromechanical discretisation and coupling transformation techniques. As a result, the two theoretical models have shown distinct frequency response equations for the dynamic solutions of the integrated physical system. In parametric studies, the two theoretical models of the smart plates with variable geometrical aspect ratio and different locations of point mass are discussed, giving good agreement. The strain mode analysis is utilised to identify the shape patterns at the region of the smart plate due to the change of strains. As a result, it can affect the electric power productions at the frequency domain. At certain cases, the appearance of asym-metric strain mode shapes may occur, resulting in the electric power reductions. To alleviate such condition, the activation of arbitrary electrode segments using the network connection can be implemented. Moreover, the smart structural model with different point mass locations is also subjected to the base excitation and the dynamic force. The proposed technique can adaptively and accumulatively generate the optimal power outputs and shift the resonance frequencies. All results of the parametric studies quantitatively show the dynamic system behaviours.

New work on the dynamics of preload nonlinearity in a single degree of freedom mechanical system is described in this article. Significant computational issues that are encountered in the application of direct harmonic balance method are avoided by flipping over the force-displacement nonlinear relationship. An indirect multi-term harmonic balance method is then proposed. Unlike the traditional direct harmonic balance method, our effort is targeted toward the determination of periodic solutions of nonlinear force instead of displacement. The indirect method also allows us to evaluate the stability of periodic solutions by employing the Hill's scheme. The primary harmonic responses as exhibited by the preload nonlinearity are validated by the describing function method. Results show that, in general, the nonlinear responses depend on the value of mean load and they differ considerably from those based on linear system analysis. Primary resonance typically shows the hardening spring effect. Unstable solutions are observed in the vicinity of primary resonance as the oscillator makes a transition from a linear to a nonlinear system. Super-harmonic resonances are found under the light mean load conditions. A new instability, in the form of quasi-periodic or chaotic responses at or near the antiresonances, is also found in our work. Finally, we successfully compare our analysis with one specific experiment that is reported in the literature. r

- by Chengwu Duan
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- Engineering, Modeling, Dynamic Analysis, Oscillator

Recent years have witnessed the use of wind as renewable energy source. This rapid growth has tremendously developed since the growing concern of the environmental pollution and also oil crisis. The size of the blades is a major factor in the power output of a wind turbine and as a result, blade length has tremendously increased in line with the growth of the wind turbine industry. However, the rapid expansion in use and size of wind turbines contribute its problems. Among the problem is maintaining the shape control at high load especially which substantially affect the aerodynamic efficiency of the airfoil of the wind blade. The structure of the wind blade is made of glass fibre reinforced plastic (GFRP) which is not only has high strength -to-weight ratio and also good rigidity. Nevertheless, it can't resist the shape upon operational air loading such as deflection from root to tip. The higher stress levels acting on the blade root will also contributes to the accumulation of fatigue damages and consequently catastrophic failures. This study intends to experimentally investigate the application of smart materials in composite wind turbine blades like structures. Nickel-Titanium (NiTi) wire which is classified as Shape Memory Alloy (SMA) has been embedded in the core of a graded beam to alleviate the load at the fixed. This corrective action relieves the high stress concentration at blade root and as a consequence minimizes fatigue damages to the blade. The study closely look at the heat load needs to be applied, the transformation temperatures, the recovery stress of NiTi. The recovery stress is very important in structural application for SMA as the recovered stress could be purposely for actuation and damping control in composite blades. A mathematical model has been developed on commercial finite element software ABAQUS for comparison.

- by Eris Supeni
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- Biomechanics, FEA, Smart Materials and Structures, Mechanical System

Background Health care workers incur frequent injuries resulting from patient transfer and handling tasks. Few studies have evaluated the effectiveness of mechanical lifts in preventing injuries and time loss due to these injuries. Methods We examined injury and lost workday rates before and after the introduction of mechanical lifts in acute care hospitals and long-term care (LTC) facilities, and surveyed workers regarding lift use. Results The post-intervention period showed decreased rates of musculoskeletal injuries (RR ¼ 0.82, 95% CI: 0.68-1.00), lost workday injuries (RR ¼ 0.56, 95% CI: 0.41-0.78), and total lost days due to injury (RR ¼ 0.42). Larger reductions were seen in LTC facilities than in hospitals. Self-reported frequency of lift use by registered nurses and by nursing aides were higher in the LTC facilities than in acute care hospitals. Observed reductions in injury and lost day injury rates were greater on nursing units that reported greater use of the lifts. Conclusions Implementation of patient lifts can be effective in reducing occupational musculoskeletal injuries to nursing personnel in both LTC and acute care settings. Strategies to facilitate greater use of mechanical lifting devices should be explored, as further reductions in injuries may be possible with increased use.

- by Laurie Wolf
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- Ergonomics, Long Term Care, Prevention, Workplace

Friction-induced vibration due to mode coupling is a major concern in a wide variety of mechanical systems. Though there are numerous papers on both linear and non-linear stability analyses of dynamical systems with friction-induced vibrations, the effects of damping on the evolution of the stable–unstable regions is not yet fully understood. The purpose of this work is to study a pin-disc model describing a typical friction-induced vibration due to a geometric constraint in order to illustrate the effects of damping on linear stability analyses. The results not only illustrate the influence of damping for determining the stable and unstable zones, but they also indicate that the “most efficient damping factor of the coupling modes” is an important factor to be taken into account. The physical mechanism causing this change in instability as a consequence of the damping factor is also suggested to help avoid bad design.

- by Jean-Jacques Sinou
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- Engineering, Modeling, Vibration, Mathematical Sciences

The unifying idea for most model-based control approaches for parallel mechanism is to derive a minimal-order dynamics model of the system and then design the corresponding controller. The problem with such a control approach is that the controller needs to change its structure whenever the mechanical system changes its number of degrees-offreedom. This paper presents a projection-based control scheme for parallel mechanism that works whether the system is overactuated or not; it does not require derivation of the minimal-order dynamics model. Since the dimension of the projection matrix is fixed, the projection-based controller does not need to change its structure whenever the mechanical system changes its number of degrees-of-freedom. The controller also allows to specify lower and upper bounds on the actuator forces/torques, making it suitable not only for the control of parallel manipulators with limited force/torque capability of the actuators but also for backlash-free control of parallel manipulators as well as for control of tendon driven parallel manipulators. The stability of the projection-based controllers is rigourously proved, while the condition for the controllability of parallel manipulators is also derived in detail. Finally, experimental results obtained from a simple parallel mechanism, which changes its degrees-of-freedom, are appended. The results also demonstrate that the maximum actuator torque can be reduced by 20% if the actuator saturation is taken into account by the controller.

- by Farhad Aghili
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- Parallel Robots, Redundancy, Mechanical System, Projection Method

Purpose -This paper aims to develop a simulating model of a journal porous metal bearing under elastohydrodynamic conditions and combined (radial, friction and thermal) load distribution and to carry out structural optimization. Design/methodology/approach -The structure analysis is carried out for each kind of load separately and for the combined load distribution of the bearing, where a dynamically loaded porous metal bearing is simulated. This simulating model is developed by finite elements method using the structure analysis module of the CATIA V5 software. Further, a parameter optimization of a porous metal bearing is presented considering the elastic deformations of the bearing shell. Findings -It is revealed that the bearing, even at points with maximum displacements, could not reach the mounting clearance value during its operational life. Relatively small bearing dimensions produce very high values of eigenfrequency response (over 150 kHz) and common dynamic loads met in all sorts of sliding bearing are not dangerous for bearing damage compared with static loads. In the stage of structural optimization based on the correlation between stress and geometric bearing parameters like wall thickness and outer diameter, the influence of finite element dimension on calculated results can be also analyzed and a proper choice of the latter is achieved.

In this paper, we construct Hamilton-Jacobi equations for a great variety of mechanical systems (nonholonomic systems subjected to linear or affine constraints, dissipative systems subjected to external forces, time-dependent mechanical systems...). We recover all these, in principle, different cases using a unified framework based on skew-symmetric algebroids with a distinguished 1-cocycle. Several examples illustrate the theory.

- by David Martín de Diego
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- Applied Mathematics, Mathematical Physics, Mechanics, Hamiltonian dynamics

Mechanical systems with time-varying topology appear frequently in natural or humanmade artificial systems. The nature of topology transitions is a key characteristic in the functioning of such systems. In this paper, we discuss a concept that can offer possibilities to gain insight and analyze topology transitions. This approach relies on the use of impulsive constraints and a formulation that makes it possible to decouple the dynamics at topology change. A key point is an eigenvalue problem that characterizes several aspects of energy and momentum transfer at the discontinuous topology transition.

- by Josep M Font-Llagunes
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- Dynamical Systems, Supply Chain Management, Topology, Dynamics

There has been increasing interest in a type of underactuated mechanical systems, mobile-wheeled inverted-pendulum (MWIP) models, which are widely used in the field of autonomous robotics and intelligent vehicles. Robust-velocity-tracking problem of the MWIP systems is investigated in this study. In the velocity-control problem, model uncertainties accompany uncertain equilibriums, which make the controller design become more difficult. Two sliding-mode-control (SMC) methods are proposed for the systems, both of which are capable of handling both parameter uncertainties and external disturbances. The asymptotical stabilities of the corresponding closed-loop systems are achieved through the selection of sliding-surface parameters, which are based on some rules. There is still a steady tracking error when the first SMC controller is used. By assuming a novel sliding surface, the second SMC controller is designed to solve this problem. The effectiveness of the proposed methods is finally confirmed by the numerical simulations.

- by Toshio Fukuda
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- Mechanical Engineering, Modeling, Robust control, Controller Design

This paper presents the analytical solutions for the temperature distribution in cross-flow plate heat
exchanger under uniform temperature boundary conditions. The heat transfer channel is in a form of an
isosceles triangular geometry. The governing equations are based on the conservation of energy principle.
The mathematical models, for both unmixed fluid, are solved by Laplace Transform leads to the developed
analytical solution that is in the form of modified Bessel function of the first kind and zero order.

Contact geometry is the odd-dimensional analogue of symplectic geometry with certain manifolds of odd dimension. It is close to symplectic geometry and like the latter it originated in questions of classical and analytical mechanics. Contact geometry has, as does symplectic geometry, broad applications in mathematical physics, geometrical optics, classical mechanics, analytical mechanics, mechanical systems, thermodynamics, geometric quantization and applied mathematics such as control theory. On the other hand, one way of solving problems in classical mechanics is with the help of the Euler-Lagrange and the Hamilton equations. In this
study, Euler-Lagrange mechanical equations as representing the motion of the body were found on contact 5-manifolds. Also, closed solutions of the differential equations found in this study are solved by symbolic computation program.

Numerous linearizations of mechanical systems feature non-normal operators. This is particularly the case in follower force systems, gyroscopic systems and models for squealing brakes. In this paper, it is shown that a pseudospectral analysis can illuminate features of these systems including dissipation-induced destabilization and high eigenvalue sensitivity to parameter variation.

- by Oliver O'Reilly
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- Engineering, Modeling, Physical sciences, Sound and Vibration

The tribological loading of forging tools is caused by the relative motion between the plastically deformed work piece and the die. In comparison to many other forming processes, hot forging has an especially disadvantageous tribological system, combining thermal, mechanical and chemical loadings. The advantages of hard coatings, which are well known for cutting tools, are to a much lesser extent explored for casting, extrusion, moulding and forging tools. Increasing the lifetime of these tools is an important task in surface engineering because of the complex loading conditions and the often complicated tool geometry, with the plasma-assisted chemical vapour deposition (PACVD) technique being well suited to the depositing of hard coatings onto large dies and moulds.

- by Bojan Podgornik
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- Materials Engineering, Mechanical Engineering, Wear, Tribology

- by Philip Holmes
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- Robotics, Applied Mathematics, Biomechanics, Control

Tujuan penelitian ini adalah melakukan analisis kekuatan mekanis knuckle, dibuat dari material FCD 50, dengan menggunakan analisis statis pada pembebanan maksimal. Beban maksimal ini diperoleh dari perhitungan pembebanan pada poros depan kendaraan dalam kondisi operasi kendaraan yang direm pada saat berbelok di jalan menurun. Pada analisis pembebanan poros kendaraan sebelumnya diperoleh beberapa nilai pembebanan pada beberapa nilai kecepatan dan deselerasi. Akhirnya, diperoleh nilai deselerasi dan nilai kecepatan maksimum kendaraan dimana kendaraan aman dioperasikan pada saat direm di jalan menurun dan berbelok. Sebagai perbandingan juga dilakukan perhitungan pembebanan poros depan kendaraan pada kondisi operasi kendaraan yang direm pada saat berbelok di jalan mendatar, karena deselerasi yang berbeda untuk masing-masing kondisi operasi, yaitu 0,5g untuk kondisi operasi di jalan mendatar dan 0,2g untuk kondisi operasi di jalan menurun. Hasil perhitungan tetap menunjukkan pembebanan maksimum pada kondisi operasi di jalan menurun. Studi statika diarahkan pada deskripsi kuantitatif dari gaya-gaya yang bekerja pada struktur teknik dalam kesetimbangan.

- by Tresna Priyana Soemardi
- •
- Biomechanics, Solid Mechanics, Mechanical Engineering Design, FEA

The problem of assigning structural properties of a linear system through sensor selection is, for a given pair (A, B), to find an output pair (C, D) such that the resulting system (A, B, C, D) has the pre-specified structural properties, such as the finite and infinite zero structures and the invertibility properties. In this paper, by introducing the notion of infinite zero assignable sets for the pair , we establish necessary and sufficient conditions for the assignability of a given set of infinite zeros and a set of structural properties which includes the left invertibility property. In establishing these conditions, we develop a numerical algorithm for the construction of the required (C, D).

- by Xinmin Liu
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- Engineering, Mathematical Sciences, Automatica, Mechanical System

This paper addresses the time-optimal control problem for a class of control systems which includes controlled mechanical systems with possible dissipation terms. The Lie algebras associated with such mechanical systems enjoy certain special properties. These properties are explored and are used in conjunction with the Pontryagin maximum principle to determine the structure of singular extremals and, in particular, timeoptimal trajectories. The theory is illustrated with an application to a time-optimal problem for a class of underwater vehicles.

- by Eduardo D. Sontag
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- Robotics, Applied Mathematics, Lie Algebra, Optimal Control

- by Monika Jenko
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- Materials Engineering, Mechanical Engineering, Wear, Tribology

This paper presents a short review of the state-of-the-art methods to identify bridge deck flutter derivatives and proposes a new algorithm to simultaneously extract the aeroelastic coefficients from free-vibration section-model tests, which is based on the improvement of the unifying least-squares ͑ULS͒ method and is therefore called modified unifying least-squares method. The advantages with respect to ULS are the faster and better convergence and the improvement in accuracy due to the introduction of weighting factors in the unifying error function. The method has been validated through numerically simulated noisy signals and experimental heaving and pitching time histories for two different bridge deck cross sections: a single-box and a multiple-box girder section model. The analysis of the artificial signals shows that a few system parameters are very difficult to be identified due to the fact that the problem is strongly ill-conditioned. Nevertheless, all the diagonal and off-diagonal components of the stiffness and damping matrices which significantly contribute to the output of the system are correctly estimated. The improvement with respect to other methods is extensively discussed. For the wind-tunnel test cases the accuracy of the identification procedure is evaluated through the comparison between measured signals and those simulated through the estimated mechanical and aerodynamic system parameters with very satisfactory results. With respect to many previous attempts of validation, this approach clearly shows the degree of accuracy that can be expected from the identification algorithm. Finally, for the considered test cases the linear model which stands behind the method seems to be an acceptable approximation of the physics of the phenomenon.

- by Claudio Mannini and +1
- •
- Mechanical Engineering, Civil Engineering, Engineering Mechanics, System Identification

A method for modal analysis of non-linear and non-conservative mechanical systems is proposed. In particular, dry-friction non-linearities are considered although the method is not restricted to these. Based on the concept of complex non-linear modes, eigensolutions are written as generalized Fourier series and the eigenproblem is then formulated in the frequency-domain. An alternating frequency-time domain method is used for the calculation of implicit non-linear forces. A two degrees-of-freedom example featuring dry-friction illustrates the method and highlights the effects of dissipation on modal parameters. The stabilizing effects of friction in presence of negative damping in the system are also addressed.

- by Fabrice Thouverez
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- Engineering, Modeling, Modal Analysis, Physical sciences

This paper investigates the effects of undercompensation and overcompensation of friction in PD controlled 1DOF mechanical systems. The friction force that is acting on the mechanical system and the friction compensation term in the feedback loop are described by a class of discontinuous friction models consisting of static, Coulomb and viscous friction, and including the Stribeck effect. Lyapunov's stability theorem and LaSalle's invariance principle are applied to prove that undercompensation of friction leads to steady-state errors and the properties of the-limit set of trajectories of a two-dimensional autonomous differential inclusion are used to show that overcompensation of friction may induce limit cycling. Furthermore, the analysis also indicates that the limit cycling effect can be eliminated by tuning the PD controller gains.

- by Devi Putra
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- Engineering, Modeling, Mathematical Sciences, Automatica