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A fuzzy adaptive sliding mode controller for an air spring active suspension system is developed. Due to nonlinearity, preload-dependent spring force and parameter uncertainty in the air spring, it is difficult to control the suspension system. To achieve the desired performance, a fuzzy adaptive sliding mode controller (FASMC) is designed to improve the passenger comfort and the manipulability of the vehicle. The fuzzy adaptive system handles the nonlinearity and uncertainty of the air suspension. A normal linear suspension model with an optimal state feedback control is designed as the reference model. The simulation results show that this control scheme more effectively and robustly isolates vibrations of the vehicle body than the conventional sliding mode controller (CSMC). [ABSTRACT FROM AUTHOR]

The article offers information on the use of smart distalization technique for Class II treatment in dentistry. It states that the technique, which reduce the need for anchorage, includes superelastic nickel titanium loops, open-coil springs, and smart biomechanics. It argues that the technique could be used to clients to want a less invasive approach than skeletal anchorage.

A microelectromechanical system tunable iris for miniaturized optical systems with a continuous tuning range of 0.45 mm to 1.56 mm is reported. In the proposed design, totally eight blades are combined together to form an octagonal aperture. These blades are evenly arranged in two chips and suspended with T-shaped beam structures, which are specially designed to convert the translatory movement provided by the electrostatic comb drive actuators into in-plane rotation of the blades. When all the blades are simultaneously rotated clockwise or counterclockwise, the aperture size will be increased or decreased accordingly. From experimental results, blade rotation angles of 10 ^\circ and 11^\circ have been demonstrated in the clockwise and counterclockwise directions, respectively. Consequently, a continuous tuning range from 0.45 mm to 1.56 mm for the aperture diameter of the as-fabricated tunable iris diaphragm has been successfully achieved. At the same time, the response time on the order of milliseconds has also been observed with the current device.\hfill[2011-0350] [ABSTRACT FROM AUTHOR]

This paper reports on a novel electrostatically actuated microelectromechanical systems (MEMS) relay for use in power-switching applications. It features a levering and torsional spring to enhance the stand-off voltage and contact endurance by means of an active-opening scheme. The proposed relay is based on a unique stacked-electrode structure and a soft insulating layer under the contact material that make it possible to obtain extremely low contact resistance, resulting in high current driving capability and reliable contact endurance. The fabricated relay demonstrated actuation voltages under 40 V, a switching time of 230 \mu \s, and a maximum stand-off voltage of 360 V, which is the highest level among electrostatically actuated MEMS relays reported to date. The contact resistance was under 5 \m\Omega at 40 V of applied voltage, and more than 1 A could be carried. The contact reliability in a hot-switching condition was investigated for various dc current levels. At a current of 10 mA, the relay operated for more than 10^7 cycles before the test was stopped. In addition, the permanent contact stiction during switching operation at a 200-mA current level was overcome with a pull-off (active-opening) voltage of 90 V by the levering and torsional spring. Using this healing process, a device that failed at about 10^4 switching cycles in the 200-mA hot-switching mode was revived and reoperated with negligible contact resistance variation, lasting up to 4.9 \times 10^5\ \cycles, constituting an order-of-magnitude enhancement in the lifetime even after failure. \hfill[2011-0278] [ABSTRACT FROM AUTHOR]

For tasks that require robot–environment interaction, stiffness control is important to ensure stable contact motion and collision safety. The variable stiffness approach has been used to address this type of control. We propose a hybrid variable stiffness actuator (HVSA), which is a variable stiffness unit design. The proposed HVSA is composed of a hybrid control module based on an adjustable moment-arm mechanism, and a drive module with two motors. By controlling the relative motion of gears in the hybrid control module, position and stiffness of a joint can be simultaneously controlled. The HVSA provides a wide range of joint stiffness due to the nonlinearity provided by the adjustable moment arm. Furthermore, the rigid mode, which behaves as a conventional stiff joint, can be implemented to improve positioning accuracy when a robot handles a heavy object. In this paper, the mechanical design features and related analysis are explained. We show that the HVSA can provide a wide range of stiffness and rapid responses according to changes in the stiffness of a joint under varying loads by experiments. The effectiveness of the rigid mode is verified by some experiments on position tracking under high-load conditions. [ABSTRACT FROM AUTHOR]

Spring brake orthosis (SBO) concentrates purely on the knee to generate the swing phase of the paraplegic gait with the required hip flexion occurring passively as a consequence of the ipsilateral knee flexion, generated by releasing the torsion spring mounted at the knee joint. Electrical stimulation then drives the knee back to full extension, as well as restores the spring potential energy. In this paper, genetic algorithm (GA) and its variant multi-objective GA (MOGA) is used to perform the search operation for the 'best' spring parameters for the SBO spring mounted on an average sized subject simulated in the sagittal plane. Conventional torsion spring is tested against constant torque type spring in terms of swing duration as, based on first principles, it is hypothesized that constant torque spring would be able to produce slower SBO swing phase as might be preferred in assisted paraplegic gait. In line with the hypothesis, it is found that it is not possible to delay the occurrence of the flexion peak of the SBO swing phase further than its occurrence in the natural gait. The use of conventional torsion spring causes the swing knee flexion peak to appear rather faster than that of the natural gait, resulting in a potentially faster swing phase and hence gait cycle. The constant torque type spring on the other hand is able to stretch duration of the swing phase to some extent, rendering it the preferable spring type in SBO. [ABSTRACT FROM AUTHOR]

Spring brake orthotic swing phase for paraplegic gait is initiated through releasing the brake on the knee mounted with a torsion spring. The stored potential energy in the spring, gained from the previous swing phase, is solely responsible for swing phase knee flexion. Hence the later part of the SBO operation, functional electrical stimulation (FES) assisted extension movement of the knee has to serve an additional purpose of restoring the spring potential energy on the fly. While control of FES induced movement as such is often a challenging task, a torsion spring, being antagonistically paired up with the muscle actuator, as in spring brake orthosis (SBO), only adds to the challenge. Two new schemes are proposed for the control of FES induced knee extension movement in SBO assisted swing phase. Even though the control schemes are closed-loop in nature, special attention is paid to accommodate the natural dynamics of the mechanical combination being controlled (the leg segment) as a major role playing feature. The schemes are thus found to be immune from some drawbacks associated with both closed-loop tracking as well as open-loop control of FES induced movement. A leg model including the FES knee joint model of the knee extensor muscle vasti along with the passive properties is used in the simulation. The optimized parameters for the SBO spring are obtained from the earlier part of this work. Genetic algorithm (GA) and multi-objective GA (MOGA) are used to optimize the parameters associated with the control schemes with minimum fatigue as one of the control objectives. The control schemes are evaluated in terms of three criteria based on their ability to cope with muscle fatigue. [ABSTRACT FROM AUTHOR]

After the use of the bed of nails for removing cavity modes in microstrip circuit packages, we propose herein a new version of this periodic structure, based on helices (springs) instead of nails. This new structure, named bed of springs, is much more compact, and this allows its use at low frequencies where the bed of nails is not suitable as it is too bulky due to the required height of the nails (pins). The bandwidth of the proposed structure turns out to be similar to the case of bed of nails. Parametric studies are presented as a design tool and a demonstrator is manufactured and measured. [ABSTRACT FROM AUTHOR]

The article focuses on an orthodontic treatment technique, anterior torque correction with basketless fixed orthodontics. It informs about the torque correction system that consists of round passive lingual retainer made of deferring elasticity of stainless steel or nickel titanium alloy wires and a spring that bonds to the anchorage tooth along with information on the recession-type defects in the gum

The advanced design of springs with tailored transmission characteristics is proposed. The existence of frequency stop-bands in the transmission characteristics is theoretically predicted and experimentally validated. The underlying mechanism of generating stop-band behavior is the periodic discontinuity of the curvature. The theoretical analysis is performed in the framework of the Floquet theory for an infinitely long spring. Experimental results are obtained for the springs consisting of a small number of repeated periodicity cells. [ABSTRACT FROM AUTHOR]

The article presents a science experiment that combines the topics of force and linear relationships by measuring the stretch of a spring as a function of weight suspended from the spring. It provides a list of procedures and materials including a support rod, a 15 centimeter vertical scale, and a horizontal wire to be used as a distance indicator. It suggests extensions for the spring experiment and notes its alignment with the U.S. Common Core State Standards for Mathematics.

The article presents information on a study which demonstrates that use of multiple strings provides a new means by which the counterintuitive behavior can be enhanced. It depicts that the complex systems which comprises of multiple interacting components can exhibit behavior different from the behavior from the properties of the individual component parts. It describes a mechanical system using rubber bands that have nearly identical measured spring constants and thread.

Purpose: The purpose of this study is to describe the technique and advantages and limitations of spring-assisted cranioplasty for sagittal suture synostosis. Methods: Preliminary data are presented of the first 41 patients treated with this technique at our institution. Results: The cephalic index was 75 after surgery and dropped to 74 one year after surgery. Mean blood loss of both procedures combined was 54 ml. Conclusion: Spring-assisted cranioplasty requires only two small incisions and is at least as effective as other techniques with respect to the cephalic index. Blood loss, operative time, and complication rate are reduced. The most important disadvantage is the need to remove the springs in a second intervention. A second drawback is that the expansion of the spring is not controllable after placement. This can be partially intercepted by adjusting the spring (or the craniotomy) to the patient's specific features. [ABSTRACT FROM AUTHOR]

The article presents a study of the effects of overrunning alternator decoupler (OAD) spring stiffness, torque applied to alternator rotor and moment of inertia (MOI) ratio between the alternator pulley and rotor on the dynamic properties of an engine front end accessory drive (FEAD) system. It describes an optimisation model for rotational vibration of tensioner arm and driven pulleys for FEAD. Results show decrease when the FEAD is equipped with OAD.

Free vibration analysis of non-cylindrical (conical, barrel, and hyperboloidal types) helical springs with rectangular cross-section is performed. The effects of the warping deformation of wire cross-section on the natural frequencies are first studied in the differential equations of motion for the springs. Improved Riccati transfer matrix method is introduced to solve the first order ordinary differential equations with variable coefficients, which consist of 14 degrees of freedom. The natural frequencies of non-cylindrical helical springs with rectangular cross-section and clamped-clamped boundary condition are calculated to validate the proposed method, and the effects of various parameters on the natural frequencies of the clamped-clamped conical springs with rectangular cross-section are also investigated. Calculations show that the warping effect upon the natural frequencies is prominent, which should be considered in the free vibration analysis of the springs. [ABSTRACT FROM AUTHOR]

This paper presents experimental data about the sources of the quadrature error in a fully decoupled microelectromechanical systems gyroscope and demonstrates the extent of performance improvement by the cancellation of this error. Quadrature sources including mass, electrostatic-force, and mechanical-spring imbalances have been compared by FEM simulations, and spring imbalance has been found as the dominant source of the quadrature error. Gyroscopes have been designed with intentional spring imbalances and fabricated with a SOI-based silicon-on-glass fabrication process, the resulting quadrature outputs of the fabricated gyroscopes have been measured, and their agreement with FEM simulations has been verified. Next, it has been experimentally shown that the electrostatic nulling of the quadrature error with closed-loop control electronics improves the bias instability and angle random walk (ARW) of a fully decoupled gyroscope up to ten times. Moreover, the quadrature cancellation improves the scale-factor turn-on repeatability about four times and linearity about 20 times, reaching down to 119 and 86 ppm, respectively. Finally, the quadrature cancellation allows operating the gyroscope with higher drive-mode displacement amplitudes for an increased rate sensitivity. With this technique, outstanding bias instability and ARW performances of 0.39^\circ/\h and 0.014 ^\circ/\surd\h, respectively, have been achieved. \hfill[2011-0078] [ABSTRACT FROM PUBLISHER]

Tensegrity structures are composed of cables and struts in a prestressed self-equilibrium. Although tensegrity first appeared in the 1950s, it is seldom used in civil engineering. This paper focuses on the design aspects of a deployable tensegrity-hollow-rope footbridge. Deployment is usually not a critical design case for traditional deployable structures. However, for tensegrity systems deployment may be critical due to the actuation required. In this paper, deployment is investigated in a general design framework. The influence of clustered (continuous) cables and spring elements in statics and dynamics is studied. Finally, actuation schemes are explored to identify cases where deployment becomes a critical design case. For this configuration, deployment is a critical design case when the structure has spring elements and continuous cables. [ABSTRACT FROM AUTHOR]

The octopus is a marine animal whose body has no rigid structures. It has eight arms composed of a peculiar muscular structure, named a muscular hydrostat. The octopus arms provide it with both locomotion and grasping capabilities, thanks to the fact that their stiffness can change over a wide range and can be controlled through combined contractions of the muscles. The muscular hydrostat can better be seen as a modifiable skeleton. Furthermore, the morphology the arms and the mechanical characteristics of their tissues are such that the interaction with the environment (i.e., water) is exploited to simplify control. Thanks to this effective mechanism of embodied intelligence, the octopus can control a very high number of degrees of freedom, with relatively limited computing resources. From these considerations, the octopus emerges as a good model for embodied intelligence and for soft robotics. The prototype of a robot arm has been built based on an artificial muscular hydrostat inspired to the muscular hydrostat of the Octopus vulgaris. The prototype presents the morphology of the biological model and the broad arrangement of longitudinal and transverse muscles. Actuation is obtained with cables (longitudinally) and with shape memory alloy springs (transversally). The robot arm combines contractions and it can show the basic movements of the octopus arm, like elongation, shortening and bending, in water. [ABSTRACT FROM AUTHOR]

Low-pressure injection molding ( LPIM) was used to produce helical alumina springs. Three sets of springs were sintered at 1550°C, 1600°C and 1650°C to observe the effects on spring constant and fracture stress. Sintered alumina springs were obtained with densities ranging from 94.0% to 97.5% of the theoretical limit. Spring constants were measured from room temperature up to 1100°C. Fracture stress data were analyzed according to Weibull statistics and the method of maximum likelihood. Upon increase of sintering temperature from 1550°C to 1650°C, the spring constant and the Weibull characteristic strength of the alumina springs increases by 15% and 32%, respectively. On the other hand, sintering temperature has a negligible influence on Weibull's modulus. This is because internal bubbles and surface defects introduced in the production stage of the ceramic springs - more than the reduction in porosity with increasing sintering temperature - are critical in determining the reliability of the ceramic springs. [ABSTRACT FROM AUTHOR]

One-dimensional discrete element model for the ballistic impact is used to determine the depth of penetration of a bullet on a thick target. Discrete Element Method (DEM) is a numerical tool where a continuum is modelled as a network of masses connected by normal springs. A one-dimensional discrete element model is developed to obtain the displacements and forces associated with the ballistic impact on a thick target. The depth of penetration of the penetrator into the target is calculated from these DEM results. The simulated results of depth of penetration are found to be in reasonable agreement with the simulation results of other numerical approaches that are available in the literature. [ABSTRACT FROM AUTHOR]

The rocking motion of a solid block on a moving deformable base is a dynamic problem that, despite its apparent simplicity, involves a number of complex dynamic phenomena such as impacts, sliding, geometric and material nonlinearities and, under some circumstances, chaotic behavior. For this reason, since the first model proposed by G.W. Housner in 1963, a number of alternative models have been proposed for its mathematical simulation. In this work, two new models are developed for the simulation of a rigid body experiencing a 2D rocking motion on a moving deformable base. The first model, the concentrated springs model, simulates the ground as tensionless vertical springs with vertical dampers placed at each of the two bottom corners of the body, whereas the second, the Winkler model, simulates the ground as a continuous medium of tensionless vertical springs with vertical dampers. Both models take into consideration sliding (with the use of both a penalty method and an analytical formulation for friction) and uplift and both are geometrically nonlinear. The models are used for simple free vibrational problems in which the effects of the ground deformability, sliding, and uplift are noted. In addition, the stability diagram for various parameters of the system, under excitation by ground motions that correspond to one full cycle sine pulses with varying amplitude and frequency, is created. The behavior of the two models is discussed and compared with the classic theory proposed by Housner. [ABSTRACT FROM AUTHOR]

A systematic study is presented on the modelling, fabrication and measurements of curled micro-bimorph cantilevers, which are composed of a dielectric beam with a metal electrode layer coated on top. The device, having stress-induced upward curvature in the electrical off-state, functions as a vertical electrostatic actuator for nanometre displacements. A detailed analysis is carried out of the resonance frequency of the cantilever as a function of its length, deflection and thickness of the upper electrode layer, including the effect of undercut. A Galerkin-based static model is used to predict the pull-in voltages which are validated by measurements. A dynamic model is used to investigate the shift in resonance frequency by the electrostatic spring softening effect, which is evaluated against experimental data. The measured shift in resonance frequency is further extrapolated to non-destructively predict the pull-in voltages. [ABSTRACT FROM AUTHOR]

This article presents a new and computationally efficient method of analysis of a railway track modelled as a continuous beam of 2N spans supported by elastic vertical springs. The main feature of this method is its important reduction in computational effort with respect to standard matrix methods of structural analysis. In this article, the whole structure is considered to be a repetition of a single one. The analysis presented is applied to a simple railway track model, i.e. to a repetitive beam supported on vertical springs (sleepers). The proposed method of analysis is based on the general theory of spatially periodic structures. The main feature of this theory is the possibility to apply Discrete Fourier Transform (DFT) in order to reduce a large system of q(2N + 1) linear stiffness equilibrium equations to a set of 2N + 1 uncoupled systems of q equations each. In this way, a dramatic reduction of the computational effort of solving the large system of equations is achieved. This fact is particularly important in the analysis of railway track structures, in which N is a very large number (around several thousands), and q = 2, the vertical displacement and rotation, is very small. The proposed method allows us to easily obtain the exact solution given by Samartín [1], i.e. the continuous beam railway track response. The comparison between the proposed method and other methods of analysis of railway tracks, such as Lorente de Nó and Zimmermann-Timoshenko, clearly shows the accuracy of the obtained results for the proposed method, even for low values of N. In addition, identical results between the proposed and the Lorente methods have been found, although the proposed method seems to be of simpler application and computationally more efficient than the Lorente one. Small but significative differences occur between these two methods and the one developed by Zimmermann-Timoshenko. This article also presents a detailed sensitivity analysis of the vertical displacement of the sleepers. Although standard matrix methods of structural analysis can handle this railway model, one of the objectives of this article is to show the efficiency of DFT method with respect to standard matrix structural analysis. A comparative analysis between standard matrix structural analysis and the proposed method (DFT), in terms of computational time, input, output and also software programming, will be carried out. Finally, a URL link to a MatLab computer program list, based on the proposed method, is given [ABSTRACT FROM AUTHOR]

Rubber suspensions are important components in railway vehicles. The offset sandwich mount is a type of rubber spring used on rail vehicles as the primary suspension above the axlebox on a bogie. In this installation, a pair of mounts is arranged within a vee configuration, such that the movements in all planes are controlled by a combined shear and compression displacement. This article evaluates the important aspects in the rubber suspension design when using a higher order material properties in an extreme large deformation. On one hand, using a higher order of material model has enabled prediction of larger deformations that are required for the actual product in the ultimate loading used in rail dynamic environment. On the other hand, using a higher order of material model with full integration elements, however, may mislead the design concept to an incorrect direction. It is important to note that the accuracy of the stress calculation is not guaranteed by a reasonable load–deflection prediction, even validated against a test result. Three methods to check the reliability of the calculated stresses are proposed. The investigation has been validated against a laboratory test. It is suggested that a higher order of material model should be used with reduced integration elements. [ABSTRACT FROM AUTHOR]

A simple benchtop experiment in which a moving cart collides with a fixed spring is described. Force-time and force-distance data recorded during the collision display the transit of compression wave fronts through the spring following impact. These data can be used by students to develop a computational model of the dynamics of this simple mass-spring-sensor system using a simple application of the wave equation and thereby develop an intriguing picture of how a spring realizes Hooke's law approximately in this dynamic physical problem. [ABSTRACT FROM AUTHOR]

This paper proposes a design methodology for the synthesis of statically balanced planar articulated manipulators through direct spring installation. The proposed method can determine all admissible configurations of spring installation with a given planar articulated manipulator. The fundamental principle for gravity balance of a conservative system of spring-gravity is formulated by a stiffness block matrix, wherein each component matrix implies interacting forces among the links. The distribution of nonzero-component matrices can be related to a type of spring configuration. The minimum number of springs that are required for a statically balanced manipulator can be further determined, based on the number of design parameters and the number of simultaneous equations derived from the zero-component matrices of stiffness block matrix. By the representation of conventional adjacency matrix for connectivity of springs among the links, five characteristics are identified to enumerate all admissible spring configurations with a minimum number of springs. Spring configurations for the statically balanced articulated manipulators with up to four degrees of freedom are obtained and illustrated schematically. An index function for the evaluation of the robustness of such a statically balanced articulated manipulator with respect to each spring configuration is also proposed. [ABSTRACT FROM PUBLISHER]

In this paper we present a cable mechanism that realizes a nonlinear rotational spring from a linear translational spring. The spring is pulled by a cable wound around a non-circular spool, which is rigidly attached to the joint. The non-circular shape of the spool induces a nonlinear relationship between its angular position and the torque created by the tension of the cable. Depending on the shape of the spool, various torque-angle relationships can be realized. We show that for a given nonlinear torque-angle relationship, there is an explicit expression (closed-form solution) of the shape of the spool that synthesizes this function. First, we present the geometry of the problem. Then, we derive the methodology to calculate the shape of the spool to synthesize a prescribed torque-angle relationship. Finally, we verify the design methodology by experiments with three different spools realizing a constant force spring, an exponential softening spring and a cubic polynomial spring. We discuss the possible sources of errors between the theoretical and experimental results. [ABSTRACT FROM AUTHOR]

Various in-pipe robots used for inspection have been developed as a preventive measure against leakage. To expand the use of these robots in small pipelines, high environmental adaptability via a simple structure must be achieved. One solution, using the screw drive mechanism, has been focused on because it requires only one motor. However, the screw drive mechanism cannot achieve complex motion because of its 1-d.o.f. Therefore, existing screw drive in-pipe robots cannot pass through curved pipes with a small curvature radius. To overcome this problem, the kinematic analysis of the screw drive mechanism has been conducted on the basis of the basic principle of helical motion in curved pipes. From the analysis, the relationship among the spring stiffness, motor torque, robot length and static friction on the inner pipe wall is established for the design of stiffness of the supporting springs. The optimal spring stiffness is, thus, derived for the robot to pass through the curved pipe and to climb up in the vertical pipe. The experimental test has been used to verify the validity of the design. [ABSTRACT FROM AUTHOR]

This paper is motivated from the wider need in system identification studies to identify and interpret the eigenvalues of seismically isolated bridges from field measurements. The paper examines the transverse eigenvalues of multispan bridges which are isolated in both transverse and longitudinal directions at all supports including all center piers and end abutments. The paper shows that regardless of the value of the longitudinal isolation period of the deck, the length of the bridge, and the number of spans, the first transverse (isolation) period is always longer than the longitudinal isolation period of the deck. This result cannot be captured with the limiting idealization of a beam on continuously distributed springs (beam on a Winkler foundation) which yields the opposite result of the first transverse period always being shorter than the longitudinal isolation period. This fundamental difference between the response of a flexural beam supported on distinct, equally spaced springs and that of a beam supported on continuously distributed springs has not received the attention it deserves in the literature of structural mechanics-dynamics. Finally, the paper shows that the first normalized transverse eigenperiod of any finite-span isolated deck follows a single master curve and the solutions from all configurations are self-similar and are not dependent on the longitudinal isolation period or on whether the deck is isolated on elastomeric or spherical-sliding bearings. [ABSTRACT FROM AUTHOR]

Direct current Resistivity (DCR) method was carried out to characterize the hydrogeological connection between the Tabular Middle Atlas (TMA) and the Saïs Basin. The TMA is one of the most important aquifers in northern Morocco that supplies the deep aquifer of the Saïs Basin. Electrical resistivity tomography (ERT) survey was focused on the Bittit area that is one of the most important outlet discharges, and it is representative of the relations between the TMA and the Saïs Basin. The high resolution capabilities of the electrical tomography were used to define the geological draining features in the framework of water paths from the TMA to the karstic springs. The synthetic data were calculated for the similar model expected in field data inversion and inversion result of these synthetic data used as a guide for the interpretation of the inverse data resistivity sections. Joint interpretation of geophysical, geological, structural, and synthetic simulation data allowed identifying a conductive horizontal shallow layer overlying two subvertical families of fractures of NE-SW and NW-SE directions. This result leads to propose hydrological behaviour of water from the Tabular Middle Atlas and the Saïs Basin at the Bittit Spring, which takes into account for both horizontal flows through stratification joints or karst and through subvertical fractures. [ABSTRACT FROM AUTHOR]

This paper proposes a fuzzy TSK controller to control a rotary flexible joint manipulator. The flexibility of joint is performed by means of a solenoid nonlinear spring, which is connected between actuator output and joint input in a bilateral connection form to transfer the produced torque; also the smooth model of frictions is used for modeling the dynamics of flexible manipulator. The effect of coulomb friction and also gearbox backlashes is decreased by a pulsation signal as an extra voltage that is added to the control voltage of actuator. Actuator dynamics is modeled by consideration of saturation mode of armature current. Experimental results demonstrate that the proposed controller has an ability to control flexible joint manipulator with a good performance. [ABSTRACT FROM AUTHOR]

An electromagnetic device, consisting of a pair of permanent magnets and a non-magnetic coil, has shown its linear advantages for inducing parametric stiffness excitation in the laboratory. The electromagnetic device powered by a DC coil current acts like a mechanical spring with constant stiffness. The effects of design parameters upon the electromagnetic stiffness and its linear operating range (referred as the stiffness characteristics) are important and crucial for the design and usage of the device. Thus, a numerical method, based upon the commercial finite element method (FEM) package ANSYS/Emag, was presented for analyzing the stiffness characteristics of the device with DC coil current. The theory foundation for computing the electromagnetic force using FEM was derived and the program realization in ANSYS was introduced briefly. Two typical examples were chosen to verify the accuracy of the numerical analysis method. Based upon these, the restoring force characteristics of the electromagnetic device with various DC coil currents were obtained utilizing the numerical method. Two important indicators (proportional coefficient between linear stiffness and coil current and linear range of the stiffness) were defined for measuring the stiffness characteristics of the electromagnetic device. Then, the effects of the design parameters (both the electromagnetic and structural parameters) on the two indicators were investigated, respectively. The research results provide useful references for the stiffness design of the electromagnetic device in actual practice. [ABSTRACT FROM PUBLISHER]

After a fatal accident involving two tractor-trailer trucks, one of which (vehicle #1) overturned and dumped its load in front of an oncoming tractor-trailer (vehicle #2), it was discovered that two of the leaf springs of the overturned trailer were broken. Forensic Engineering metallurgical examination of the fracture surfaces of the broken springs and other axle evidence, in conjunction with accident reconstruction results, played a key role in determining the overall sequence of events in the accident. [ABSTRACT FROM AUTHOR]

Abstract: The instrument was developed by comprehensively making use of the mechanical, photo and electronic techniques. It controlled by a microcomputer system, can automatically measure nine geometric parameters of a spring bar which needs only one time of installation. Its uncertainty of measurement is by far less than one- tenth of the tolerances of the measured parameters, and it spends only about forty seconds to complete the measurement of a spring bar. This paper introduces the principles of the structure and operation of the instrument, especially presenting the principles of the specially devised mechanical-photo-electronic and photo- electronic sensors used in the instrument. [Copyright &y& Elsevier]

Live-load distribution is an important step in the analysis of bridge superstructures. This paper introduces a new framework to compute live-load distribution for bridge girders. The model uses elastic spring elements to simulate the reaction of main girders to the deck system. The cross-section frame of the superstructure is supported by these elastic springs. Live-load distribution factors are derived according to the maximum reaction of each spring element under random truck loads. Results from the proposed model are compared with those from bridge-design specifications. Engineering practice shows that this model is easy to use and provides results comparable with current design standards. The significance of this framework is that it can be used to compute live-load distribution without limits to parameters such as girder space, span length, and truck-wheel space. This research will provide a convenient tool for engineers to perform bridge design or for researchers to compare research results from other methods. [ABSTRACT FROM AUTHOR]

Most running robots and running models use linear leg springs. Non-linear leg springs have the potential to improve the performance of running robots and models, but it is not clear to what extent. In this paper, the effect of non-linear leg springs on disturbance rejection behavior is investigated. The optimal leg stiffness profile is determined by optimizing the gait sensitivity norm, a measure for disturbance rejection. The results of this optimization show that the optimal leg stiffness profile is strongly non-linear, and that the disturbance rejection is a factor of seven better than it would be with the optimal linear leg stiffness. The cause for this great improvement is that non-linear leg springs allow stable limit cycles that are much further away from the fall modes. [ABSTRACT FROM PUBLISHER]

In this paper, we examine the use of boundary springs as approximate external boundary conditions for the typical soil islands encountered in finite-element (FE) models of soil-foundation interaction problems. We present a set of simple uniformly distributed boundary springs and a set of variable boundary springs that account for the lateral distribution of contact forces between the foundation and the soil. We evaluate the accuracy of the approach for shallow foundations resting on soil islands of different dimensions. It is shown that significantly smaller errors can be achieved with these boundary springs than those obtained when fixed-fixed or fixed-free external boundary conditions are used. We present an iterative approach to determine the boundary springs for cases in which extremely small soil islands are required. Although the approach suggested to determine the boundary springs is best suited to shallow foundations, good results are also obtained for pile foundations. The approach presented applies to a uniform elastic half-space, but extensions to layered media are possible. [ABSTRACT FROM AUTHOR]

Variable stiffness actuators are a particular class of actuators that is characterized by the property that the apparent output stiffness can be changed independent of the output position. To achieve this, variable stiffness actuators consist of a number of elastic elements and a number of actuated degrees of freedom, which determine how the elastic elements are perceived at the actuator output. Changing the apparent output stiffness is useful for a broad range of applications, which explains the increasing research interest in this class of actuators. In this paper, a generic, port-based model for variable stiffness actuators is presented, with which a wide variety of designs can be modeled and analyzed. From the analysis of the model, it is possible to derive kinematic properties that variable stiffness actuator designs should satisfy in order to be energy efficient. More specifically, the kinematics should be such that the apparent output stiffness can be varied without changing the potential energy that is stored in the internal elastic elements. A concept design of an energy-efficient variable stiffness actuator is presented and implemented. Simulations of the model and experiments on the realized prototype validate the design principle. [ABSTRACT FROM AUTHOR]

A new hybrid soft tissue model, which is mainly based on the mass-spring model (MSM) and the 3-D finite strain nonlinear anisotropic elasticity theory, is presented for visio-haptic simulations, such as surgery simulators. One significant difference from conventional MSMs is that the internal forces among mass nodes are derived within the framework of nonlinear continuum mechanics. As a result, the new hybrid model is much more realistic in the sense that it incorporates the typical biological properties and behaviors of living tissue such as nonlinearity, anisotropy, viscoelasticity, and incompressibility. From the implementation point of view, the proposed model can be regarded as a hybrid of finite-element and MSMs, which enables it to maintain largely the advantage of the MSM, such as a simple architecture, low memory usage, and fast computation. The new model is validated in several benchmark problems, and the results show very good agreement with real experimental data reported in the literature. An example simulating a human kidney is given to demonstrate the capabilities of the proposed model in describing the nonlinearity, anisotropy, viscoelasticity, and incompressibility of typical soft tissue. [ABSTRACT FROM AUTHOR]

Internal vibration of the valve spring is a critical factor in determining the dynamic characteristics of high-speed valve train systems. Because precise prediction of the spring surge amplitude is a difficult problem, especially for nonlinear variable-pitch springs, the development stage requires a process of trial and error. In the present study, a new method that considers the variable natural frequency and variable damping ratio is proposed to predict the spring surge amplitude. First, the change in the natural frequency and damping ratio caused by compression is predicted from the initially given pitch curve at the free height. Second, the spring surge amplitude is estimated by solving the wave equation with nonlinear variable coefficients. The surge amplitudes of typical valve springs are also measured using a motoring test rig and are compared with theoretical results predicted by the spring drawing and cam profile data. [ABSTRACT FROM AUTHOR]

The problem of active fault-tolerant control for vehicle active suspension systems in finite-frequency domain is investigated. First, a linear model of vehicle active suspension systems is given. With an observer-based fault estimator, a new H∞ controller in generalised internal model control architecture is proposed. By using the Kalman-Yakubovich-Popov lemma, sufficient conditions ensuring simultaneous finite-frequency estimation and control performance are derived. In terms of the linear matric inequalities, fault compensation is also proposed. Finally, simulation results are given to illustrate the effectiveness of the proposed results. [ABSTRACT FROM AUTHOR]

Abstract: In the precision manufacturing field, the major structural components are often made of rigid and massive elements. Those mechanisms are so fluctuated by swaying of building and resonating of ground floor that the precision gets lower. As a result, quality of products is declined. So far, to minimize the influences of result from external irregular vibration, various technical methods of the absorbing vibration are used. For example, vibration isolation table which use air damper and heavy granite surface plate are used. But, these devices need high cost and low mobility. In this paper, our target is to analyze the external vibration and then to develop a mechanism which is able to reduce the effect. It is also able to be produced at a lower cost. Firstly, a silicone support is proposed as a simple vibration isolating mechanism. Swaying and resonating of a building have 2∼4Hz vibrating frequency when a person is running on a treadmill, similar phenomena happen. Therefore, the supports are mounted under the running pad of a treadmill. This is a passive vibration isolator. The support is designed to have low stiffness and high deformation to isolate and absorb the vibration. As a result, it reduces the peak amplitude of vibration by about 80%. Secondly, a dynamic vibration absorber is developed to minimize the repetitive vibration. The absorber has a fundamental resonating frequency by its spring and mass. The resonating frequency is designed to have close value to the vibrating frequency of the treadmill. The length of beam can be adjusted to have variable resonance according to the external vibration. This absorber also reduces vibration by 84%. The passive vibration isolator and dynamic vibration absorber can be applied to precision equipments with repetitive motion or with disturbance of swaying of building. [Copyright &y& Elsevier]

The article presents a research paper which presents a method for investigating the integral abutment behavior of non-symmetrically loaded bridges. It is said that integral abutment bridges (lABs) are used for building single-span bridges and restraint of the frame corner differentiate them from conventional bridges. The discussed paper presents a new approach to separate the superstructure from the sub-structure, which is based on division of the non-linear springs into two linear springs.

The load-deflection behaviors of constant force spring are analyzed and discussed systematically by using the principle of potential energy subsections. Then, an example is given for comparing their load-deflection behaviors when constant force spring is frontwound and backwound respectively. In addition, the effects of the diameter of drum on the spring's characteristics are obtained. The results show that the principle of potential energy subsections can cause a result quite accurately and be used as a guide for designing a constant force spring. [ABSTRACT FROM AUTHOR]

Lower-limb amputees expend more energy to walk than non-amputees and have an elevated risk of secondary disabilities. Insufficient push-off by the prosthetic foot may be a contributing factor. We aimed to systematically study the effect of prosthetic foot mechanics on gait, to gain insight into fundamental prosthetic design principles. We varied a single parameter in isolation, the energy-storing spring in a prototype prosthetic foot, the controlled energy storage and return (CESR) foot, and observed the effect on gait. Subjects walked on the CESR foot with three different springs. We performed parallel studies on amputees and on non-amputees wearing prosthetic simulators. In both groups, spring characteristics similarly affected ankle and body center-of-mass (COM) mechanics and metabolic cost. Softer springs led to greater energy storage, energy return, and prosthetic limb COM push-off work. But metabolic energy expenditure was lowest with a spring of intermediate stiffness, suggesting biomechanical disadvantages to the softest spring despite its greater push-off. Disadvantages of the softest spring may include excessive heel displacements and COM collision losses. We also observed some differences in joint kinetics between amputees and non-amputees walking on the prototype foot. During prosthetic push-off, amputees exhibited reduced energy transfer from the prosthesis to the COM along with increased hip work, perhaps due to greater energy dissipation at the knee. Nevertheless, the results indicate that spring compliance can contribute to push-off, but with biomechanical trade-offs that limit the degree to which greater push-off might improve walking economy. [ABSTRACT FROM PUBLISHER]

Aim: The purpose in this study was to evaluate the degradation force of conventional synthetic orthodontic elastics and synthetic orthodontic elastics with memory properties. Methods: Specimens of each material (Plastic chain, Memory chain and Closed spring NiTi) were stretched and adapted to the test specimens composed of resin plates and orthodontic wires, simulating retraction units. Degradation force was verified in an Instron universal test machine at the following intervals: 1, 2, 18, 24, 48 h; 7, 14, 21, and 28 days. Data (gF) were analyzed statistically using Friedman and Kruskal-Wallis tests at 5% significance level. Results: It was observed a significant force reduction of Plastic chain and Memory chain after 2 h (p<0.05). For NiTi spring significantly force reduction was observed after 18 h, but no significant change was showed up to 21 days. NiTi spring showed force significantly higher than synthetic elastomeric materials (p<0.05). There was no significant difference between Memory chain and Plastic chain up to 24 h. However, from 48 h to 21 days Memory chain showed force significantly higher than Plastic chain. Conclusions: There was higher force degradation in the synthetic elastomeric materials in comparison with NiTi springs, which allows the preferential indication of these space closure jigs for clinical use. [ABSTRACT FROM AUTHOR]

Dancer systems are typical equipment for attenuation of tension disturbances. The two kinds of dancer, active dancer and passive dancer, are distinguished by an external actuator. In the active dancer, the position of the dancer roll is measured and the roll is forced by the external actuator to regulate tension disturbances. However, the passive dancer, composed of a spring, damper and roll has no external actuator. Tension disturbance generates movements of the roll of the passive dancer and the displacements regulate the tension variation. However, the hybrid dancer, which is a mixture of passive and active dancer, is applied for the roll-to-roll systems. It regulates tension disturbances indirectly in the manner of keeping a constant position for the roll by changing the velocity of the driven roller adjacent to the dancer roll. It has different characteristics from those of the passive or active dancer. In this paper, the modeling of the pendulum dancer is derived. The dynamics of the hybrid dancer, which feedbacks the position of the dancer roll, and the PI control of a driven roll are analyzed. The matching logic for tuning gains is developed and experimentally verified. [ABSTRACT FROM PUBLISHER]

Current treatments for gait pathologies associated with neuromuscular disorders may employ a passive, rigid brace. While these provide certain benefits, they can also cause muscle atrophy. In this study, we examined NiTi shape memory alloy (SMA) wires that were annealed into springs to develop an active, soft orthotic (ASO) for the knee. Actively controlled SMA springs may provide variable assistances depending on factors such as when, during the gait cycle, the springs are activated; ongoing muscle activity level; and needs of the wearer. Unlike a passive brace, an active orthotic may provide individualized control, assisting the muscles so that they may be used more appropriately, and possibly leading to a re-education of the neuro-motor system and eventual independence from the orthotic system. A prototype was tested on a suspended, robotic leg to simulate the swing phase of a typical gait. The total deflection generated by the orthotic depended on the knee angle and the total number of actuators triggered, with a max deflection of 35°. While SMA wires have a high energy density, they require a significant amount of power. Furthermore, the loaded SMA spring response times were much longer than the natural frequency of an average gait for the power conditions tested. While the SMA wires are not appropriate for correction of gait pathologies as currently implemented, the ability to have a soft, actuated material could be appropriate for slower timescale applications. [ABSTRACT FROM AUTHOR]

The mechanical behavior of superelastic springs is investigated in this study. The goal is to evaluate the device response and to exploit the material superelastic behavior, main concerns being material and geometrical response nonlinearity. The investigation is made of two parts, i.e., an experimental campaign and a numerical model proposal. Experimental tests have been performed on superelastic SMA coil springs considering load history in tension and compression for three different spring geometrical configurations. Tested specimens experience a maximum elongation larger than the original spring axis length. The response is not symmetric and under compression it is affected by buckling instability. Nevertheless, experimental results show a very good superelastic behavior with no damage and with negligible residual displacements. Numerical analyses have been performed to reproduce the experimental campaign results. A simple finite element model is proposed. Experimental and numerical result agreement is very good. The numerical model turns out to be a powerful design tool even for the very complex geometrical and material nonlinear conditions under investigation. Hence, it is proposed as a useful tool for spring design validation and response prediction. [ABSTRACT FROM AUTHOR]

People often grasp objects with an awkward grip to ensure a comfortable hand posture at the end of the movement. This end-state comfort effect is a predominant constraint during unimanual movements. However, during bimanual movements the tendency for both hands to satisfy end-state comfort is affected by factors such as end-orientation congruency and task context. Although bimanual end-state comfort has been examined when the hands manipulate two independent objects, no research has examined end-state comfort when the hands are required to manipulate two physically-coupled objects. In the present experiment, kinematics and grasp behavior during a unimanual and bimanual reaching and placing tasks were examined, when the hands manipulate two physically-connected objects. Forty-five participants were assigned to one of three groups; unimanual, bimanual no-spring (the objects were not physically connected), and bimanual spring (the objects were connected by a spring), and instructed to grasp and place objects in various end-orientations, depending on condition. Physically connecting the objects did not affect end-state comfort prevalence. However, it resulted in decreased interlimb coupling. This finding supports the notion of a flexible constraint hierarchy, in which action goals guide the selection of lower level action features (i.e., hand grip used for grasping), and the particular movements used to accomplish that goal (i.e., interlimb coupling) are controlled throughout the movement. [ABSTRACT FROM AUTHOR]