Dynamic Reaction Forces Research Articles

Ground reaction forces analyses during the gait of healthy individuals with and without the use of a calcaneus insole

The foot forms the base of propulsion and balance during the gait. It is well known that excessive or prolonged pronation and supination changes the gait’s mechanical movement. Hence, the use of corrective insoles is recommended when calcaneus alterations (valgus and varun) are present. Objetive: The main purpose of this article was to analyze the effects of a calcaneus insole on normal individuals on the Ground Reaction Force variables. Method: The experiment used ten adults (31.9 ± 6,7 years, 65.9 ± 15.4 kg and 1.7 ± 0.1 m) and registered no apparent changes in gait or pathologies that have an effect on the locomotor system. The following gait conditions were analyzed and compared: barefoot, using a sport shoe, and using the sport shoe with insole. The variables analyzed were vertical, medial lateral, and anterior-posterior dynamic ground reaction forces. An ANOVA one-way was used in order to compare the three different conditions. Statistically significant differences were revealed between the conditions of barefoot and sport shoe with insole for the vertical GRF during initial contact Fz1 (F2,59 = 3.4; p < 0.0406) and for the GRF anterior-posterior in the terminal stance phase Fy2 (F2,59 = 3.63; p < 0.0332). Results: These results indicated that the use of an insole increased the vertical impact on the locomotor system during the response to load phase, probably because of its greater stiffness compared to the barefoot or sport shoe trials. The insole also changed the GRF anterior-posterior during the terminal stance that corresponded with the acceleration/propulsion gait phase. Conclusion: Just based on the analysis of the dynamic variables, it was concluded that the use of insoles did not induce any significant increase in lateral forces that would indicate the reduction of excessive pronation or supination during the response load phase. The use of an insole produced a significant dynamic effect on the pronation/supination only in the propulsive gait phase.

Gyroscopic Torque Analysis and Dynamic Balance Test of the Vertical Aerostatic Spindle

Ultra-precision flying cutting machining with a vertical milling style is an important means of ultra-precision machining. It has a close relationship between the machining accuracy and the dynamic characteristics of the aerostatic spindle. The film force acting on the spindle rotor is related to the manufacture, installation and static unbalance or dynamic imbalance or other factors. Therefore, it is necessary to analyze the dynamic pressure force caused by these factors in order to study on the rotor posture and quantitative movement of the spindle. This article derived the solution formula for the dynamic pressure reaction force of the ultra-precision machine tool spindle with vertical static film based on the basic theory of the rigid body dynamics. The gyroscopic torque of the spindle has been analyzed under different conditions with the spindle dynamic balancing tests, which provide a reference to the further analysis of the spindle dynamic characteristics.

Fastening ergonomics study based on state-space modelling of hand-arm system

The aim of this study is to model the hand-arm as a rotational single-degree-of-freedom system during fastening operations with shear-type fasteners using state-space representation. The values of the model parameters are estimated by determining the characteristic state-space matrices from the measured tool rotation and torque data collected during the fastening operation and then using a parameter extraction algorithm to derive the model parameters in the state-space matrices. The identified parameter values are used to determine the response and the dynamic reaction force, which are used to assess the dynamic effects of tool operation on the hand-arm. The effect of posture, grip-force and tool-type variation is analysed using the dynamic reaction force. Strong agreements are observed between the predicted and measured responses. The model parameter values increase with an increase in grip force and vary significantly for the two tools and four postures studied. The pistol-grip tool generates larger reaction force than the right-angled tool.

Challenges in relating experimental hip implant fixation predictions to clinical observations

Long-term clinical follow-up studies have shown that radiolucent lines at the cement interfaces of total hip replacement femoral components develop gradually, ultimately leading to loosening. In this experimental study, 32 synthetic femurs implanted with cemented femoral components were cyclically loaded with a dynamic joint reaction force, torque, and muscle force, to assess the relative effects of surface finish and collars on interface fixation. Four each of four otherwise identical straight femoral stems, varying only in surface finish and presence or lack of collars were used. Specimens were tested under two conditions: (1) with intact interfaces simulating immediate post-operative conditions and (2) with a thin-film at the stem–cement interface, simulating conditions several weeks to months post-operative when fibrous tissue has formed with the implant still stable. Micromotion was measured at both interfaces in three directions. Surface finish had a larger relative effect than collars, regardless of whether or not a thin-film was present. For example, a proximal grit-blasted finish enhanced fixation at the stem–cement interface by 7–12 μm per-cycle ( p<0.05) and decreased early cement mantle loosening by 7–13 μm. For straight stems, rougher surfaces provided greater stability than polished, even with a thin film at the stem–cement interfaces, contradicting the theory that once debonded, rough stems are less stable than polished at the stem–cement interface. The findings of this experimental study exemplify the need to take advantage of all available tools for the preclinical evaluation of orthopaedic implants, including long-term clinical observations of related devices, analytical and numeric models, and experimental bench-top simulations.

Development of a tyre traction testing facility

An experimental setup comprising up of an indoor soil bin, a single wheel tester (SWT), a soil processing trolley, a drawbar pull loading device and an instrumentation unit was developed to perform traction tests in the soil bin to study the effect of soil, tyre and system parameters on the performance of tyres. The design of the single wheel tester was such that the dynamic weight reaction force is equal to that measured statically. It is a simple wheeled device, capable of testing tyres of up to 1.5 m in diameter, vertical force up to 19 kN, net pull up to 7.2 kN, torque up to 5.5 kN m, and speed up to 3.5 km/h.

Modelling hermetic compressors using different constraint equations to accommodate multibody dynamics and hydrodynamic lubrication

In this work, the steps involved for the modelling of a reciprocating linear compressor are described in detail. The dynamics of the mechanical components are described with the help of multibody dynamics (rigid components) and finite elements method (flexible components). Some of the mechanical elements are supported by fluid film bearings, where the hydrodynamic interaction forces are described by the Reynolds equation. The system of nonlinear equations is numerically solved for three different restrictive conditions of the motion of the crank, where the third case takes into account lateral and tilting oscillations of the extremity of the crankshaft. The numerical results of the behaviour of the journal bearings for each case are presented giving some insights into design parameters such as, maximum oil film pressure, minimum oil film thickness, maximum vibration levels and dynamic reaction forces among machine components, looking for the optimization and application of active lubrication towards vibration reduction.

An analytical approach to train-induced site vibration around Shinkansen viaducts

This study is intended to establish an analytical approach to evaluate the site vibration caused by the passage of bullet trains over Shinkansen viaducts. In this approach, to simplify the problem the entire train–bridge–ground interaction system is divided into two subsystems: train–bridge interaction and foundation–ground interaction. In the train–bridge interaction problem, the analytical programme to simulate the traffic-induced bridge vibration is developed. Then, the dynamic responses of the viaducts are calculated to obtain the dynamic reaction forces at the bottoms of the piers. Applying these reaction forces as input excitation forces in the foundation–ground interaction problem, the site vibration around the viaducts is simulated and evaluated using a general-purpose programme.

Dynamic Reaction Force of Feet after Unilateral Total Knee Arthroplasty

Objective: The follow-up period before implementing a new concept or technique introduced in a clinical study generally takes a long period. The present study is an attempt to shorten the follow-up period. A prospective study with measuring dynamic reaction force of feet to monitor the relationship between the clinical outcome and gait function in TKA patients following slightly valgus overcorrection was conducted. Theoretically, slightly valgus overcorrection for patients who underwent TKA might achieve more benefits. Methods: A device of the Dynamic Foot Pressure Assessment Unit (DFPAU), which was revised from the Computer Dyno Graphy (CDG), was used to investigate the clinical outcome in patients with unilateral total knee arthroplasty. Thirty-eight knees were overcorrected with slight valgus position (3° on the mechanical axis) and regularly followed for at least 1 year. Evaluation of gait analysis with the described device was performed preoperatively, before discharge, 1 month, 3 months, and 1 year postoperatively. Results: At 1 year, the ratio of force for single leg stance (RFL) and the ratio of impulse for single leg stance (RIL) had significant improvement as compared with the preoperative status. The improvements even reached normal levels as compared with the contralateral knee. In addition, the Knee Society (KS) functional scores also showed significant improvement as compared with the preoperative status (86 versus 52 points). The optimal height of the handgrip of a walker was found to be at the level of the wrist crease when the upper extremity hung down. Conclusions: Assessment of dynamic reaction force of feet might be used to monitor the outcomes of clinical treatment.

Reduction of traffic-induced vibration of two-girder steel bridge seated on elastomeric bearings

Reinforcing end-cross beam and removing bumps at expansion joints of bridges are proposed to reduce the traffic-induced vibration and to enhance the deck resistance near the expansion joint of a two-girder steel bridge with elastomeric bearings at each support. The reduction effect is investigated by means of a three-dimensional traffic-induced dynamic analysis. This study indicates that traffic-induced acceleration responses as well as dynamic reaction force of the bridge with the elastomeric bearings are greater than those of the bridge with steel pin bearings. It is observed that reinforcing the end-cross beam reduces traffic-induced vibrations regardless of bearing types, and also removing bumps is the most effective in reducing the dynamic reaction force of the bridges. Especially, for the bridge with elastomeric bearings, the maintenance of bumps near expansion joints is very important to improve not only expanding life span of the expansion joint but also the vibration serviceability of bridges.

A new view on visuomotor channels: The case of the disappearing dynamics

A considerable body of kinematic data supports the proposal that independent visuomotor channels are involved in the control of the transport and grip components of reach and grasp. These channels are seen as having separate perceptual inputs, outputs and internal processing and are thought by some to correspond to independent neuroanatomical pathways. The idea that different groups of muscles and biomechanical structures can be controlled independently is attractive, but this kinematically-inspired hypothesis fails to take into account the complexity of the dynamic relationships and their interactions within the neuromusculoskeletal system. Inertial, viscous, centrifugal, coriolis, gravitational and reflex cross couplings exist between efferent drives to muscles and resulting body movements. Rotation at even a single joint generates a complex set of dynamic reaction forces and requires coordinated activation of many muscles throughout the body to maintain posture and balance. In this theoretical paper we present a new view of independent visuomotor channels in the form of an adaptive neural controller that can compensate for the above interactions and decouple the relationships between efferent drives to muscles and resulting body movements. At the same time, the neural controller renders all the dynamics (linear and nonlinear), other than time delays, of the neuromusculoskeletal system, unobservable in the visuomotor relationships. Using the geometry of nonlinear dynamical systems we show that, providing certain constraints on the structure of time delays within the system are satisfied, there exists a neural controller that can render all the dynamics of the neuromusculoskeletal system (except for time delays) unobservable in the responses. The controller simultaneously decouples all the interactive dynamics so that each of the m independent inputs controls one and only one degree of freedom of the response. This means that each degree of freedom in a multi-joint response can be controlled by an independent component of the visual input, a behaviour that has long been observed in visual tracking experiments. The controller effectively establishes m independent visuomotor channels. However, rather than reflecting separate neuroanatomical pathways, the independent channels result from a neural controller with convergent and divergent connections to compensate for the interactive nonlinear dynamics within the neuromusculoskeletal system. This new view of visuomotor channels has implications for neural control processes involved in the acquisition and adaptability of skilled perceptual–motor behaviour in general, as well as for the design of robotic controllers.

The role of muscles in joint adaptation and degeneration

Muscles are the primary contributors to joint loading. Loading is typically associated with the onset and progression of joint degeneration, and in turn, joint degeneration is known to affect negatively the control of muscle forces and co-ordination patterns. Nevertheless, the role of muscles in joint adaptation and degeneration has been largely ignored. Here, we review some of our research on the in vivo changes in muscular forces and joint loading in animal models of osteoarthritis and in patients with joint injury and disease. We attempt to emphasize the close dependence of muscle forces, joint loading and degeneration and, vice versa, try to point out how joint degeneration affects muscle forces and joint loading. We measured the forces and electromyographic signals in normal and anterior cruciate ligament transected feline knees and measured (1) a consistent decrease in the knee extensor and ankle extensor muscle forces for weeks following intervention; (2) a corresponding decrease in the static and dynamic external ground reaction forces; and (3) a change in the electromyographic signals (in terms of the firing patterns of individual muscles and of the co-ordination of extensors and flexors during locomotion). We introduced results on the biosynthetic response of articular cartilage to controlled, in vivo, loading and discuss preliminary results from an experimental animal model of muscle weakness. In contrast to much of the published literature, loading, in our case, is introduced by controlled nerve stimulation and the corresponding muscular forces that load the joint in its in vivo configuration. We found that short-term loading (30-60 min) in the cat knee produces distinct up-regulation of mRNA of specific metalloproteinases (MMPs) and some of the MMP inhibitors. In our newly developed muscle-weakness model, we confirmed that controlled Botox injections in the rabbit knee extensor muscles cause a 60-80% decrease in muscle force, and that these changes in muscle force are associated with changes in the external ground reaction forces, and most importantly, that muscle weakness seems to be associated with degeneration of the knee in the absence of joint instability or any other intervention. From the results of our research, we conclude that muscle health and muscle rehabilitation are key components for the successful prevention of, and recovery from, joint injury and disease.

진동에서 생기는 동적 하중을 줄이기 위한 능동 최적 제어

Excessive vibration in flexible structures is a problem encountered in many different fields, causing fatigue of structural components. Passive techniques, though sometimes limited in their capabilities, have been used in the past to attenuate vibrations. Recently active techniques have been developed to enhance vibration control performance beyond that provided by their passive counterparts. Most often, the focus of active control methods has been to suppress structure displacements. In cases where vibration results in structure failures, displacement suppression may not be the best choice of control approaches (it can, in fact, increase dynamic loads which would be even more harmful to supports) . This paper presents two optimal control methods for attenuating steady state vibrations in flexible structures. One method minimizes shaft displacements while another minimizes dynamic reaction forces. The two methods are applied to a model of a typical flexible structure system and their results are compared. It is found that displacement minimization can increase loads, while load minimization decreases loads.

Impact Resistant Behavior Of Shear-failure-type RC Beams Under Falling-weight Impact Loading

In this study, to investigate the impact-resistant behavior of shear-failure-type reinforced concrete (RC) beams, fa~ling-weight impact tests were conducted by means of a single loading method. Nineteen simply supported rectangular RC beams were used for these experiments. All RC beams were of 200 mm wide, 400 mm deep, and 2,400 mm long in dimensions, in which shear rebar ratio and impact velocity were taken as variables. An impact load was applied on to the mid-span of each RC beam by dropping a steel-weight (hereinafter, striker) with a 400 kg mass. In these experiments, the impact force excited in the striker, the reaction force and the mid-span displacement were measured and recorded by wide-band analog data recorders. The results obtained from this study are as follows: 1) when the RC beam reaches the ultimate state with shear-failure mode, reaction force vs. mid-span displacement curve forms an isosceles triangle, irrespective of magnitude of shear rebar ratio; 2) at the time, maximum reaction force reaches an absolute value; 3) using the relationship between absolute maximum dynamic reaction force and static shear capacity, an impact-resistant design for shear-failure-type RC beams can be rationally performed using the static shear capacity.

液体水素ターボポンプ用静圧軸受の動的挙動の数値シミュレーション

In the present paper, the dynamic behavior of a rotor supported by externally pressurized liquid hydrogen bearing is theoretically investigated. The bearing treated in this study has 20 recesses arranged in two rows in a staggered manner and will be used in the liquid hydrogen turbopump of rocket engines for space transport systems. The equations of motion for a rotor are numerically solved using predictor-corrector scheme. The dynamic bearing reaction forces are calculated from the numerical solution of unsteady turbulent Reynolds lubrication equation. The transient responses of hydrostatic bearing under several operating conditions are presented. Furthermore, the journal center trajectories with imbalanced moment are examined theoretically.

Influence of Elastomeric Bearings on Traffic-Induced Vibration of Highway Bridges

Elastomeric bearings (rubber bearings) have been used in highway pseudo-continuous bridges without joints changed from simple girders to reduce the environmental influence of traffic-induced vibration. In addition, elastomeric bearings have been adopted in simple girder bridges for base isolation systems of earthquakeproof structures. Three-dimensional analysis of dynamic response of bridges under moving vehicles is carried out to examine the change of dynamic response in bridges caused by replacing steel bearings with elastomeric bearings. Analytical results are compared with experimental results in urban highway bridges. It is not shown clearly in experiments that natural frequencies are changed slightly in analysis by replacing steel with elastomeric bearings. Although vertical displacements of main girders at the span center do not almost change between steel and elastomeric bearings, horizontal displacement in the bridge axis direction becomes larger with elastomeric bearings. For the evaluation of the experimental acceleration of the ground motion, the dynamic reaction force is analyzed and the dynamic influence is investigated.

Numerical simulation of submarine pipelines in dynamic contact with a moving seabed

The dynamic response of submarine pipelines to earthquake-generated vertical seabed motions is examined with the aid of a finite element model. A relaxation algorithm is adopted in order to overcome the problem of unknown dynamic seabed reaction forces. Rotational rigidity is assumed at the boundary points, which are allowed to move vertically in unison with the random seabed oscillations. For the interior nodes, the description of the kinetic energy loss, resulting from pipeline-seabed impact, is approached through the use of a restitution coefficient of 0.5, which represents an intermediate collision mode between a perfectly elastic and an inelastic one. Fundamental system frequencies are determined by the use of support positions obtained from a static analysis of the unilaterally constrained structure. The structural damping matrix is approximately evaluated according to Rayleigh's method. Response spectra to a strong motion vertical acceleration earthquake record provide an initial guideline into the pipeline stability. Peak dynamic and static bending stresses are calculated for a case study involving two submarine pipeline crossings. Complete, partial and lack of pipeline gravel cover is assumed in the analysis. A seabed profile alteration, due to probable soil liquefaction, is furthermore imposed, in order to investigate the subsequent effect upon the dynamic pipeline stresses.

A Study of Dynamic Reaction Force on A Cylinder Ejected to Uniform Flow

A Study of Dynamic Reaction Force on A Cylinder Ejected to Uniform Flow

On the Design of Zero Reaction Manipulators

In a number of industrial, space, or mobile applications, reaction forces and moments transmitted by a manipulator to its base are undesirable. In this paper, we analyze the problem of force and torque transmission in robotic systems, and propose design and planning methods that can eliminate it, or reduce it. Based on force and moment transmission analysis, a three DOF redundant manipulator design is selected. Dynamic reaction forces are eliminated by force balancing. Reaction moments are eliminated by following reactionless paths, whose planning is simplified by rendering the dynamics configuration-invariant. Reactionless Workspaces are defined in which any end-effector path can result in zero dynamic reactions. An example is used to demonstrate the usefulness of the proposed methods. An important advantage of these methods is that the manipulator can be used either as a redundant, or as a reduced DOF reactionless system.

Dynamic Design Analysis of Looped Flexible Printed Circuit.

A new design process is developed for a flexible printed circuit (FPC) that picks up the head signals of a magnetic disk unit, and can optimize the FPC loop shape. The head can be positioned by consideration of dynamic reaction force of FPC. In the process the dynamic treatment of a FPC is regarded as a vibration structure. A calculation method is proposed equivalent bending rigidity (EI) of a complex FPC. The evaluated EI is further used to determine the influence of the dynamic reaction force. A dynamic FEM model and the servo model are used to determine the residual vibration force just after bang-bang seek. Evaluated dynamic reaction force agrees very well with the experimental data. It is clear that the dynamic reaction force is very similar to the shock spectrum of a single degree of freedom. The optimization of FPC jointed to carriage and base for both ends is achieved. The optimum shape is very close to semicircular.

Rotordynamic Analysis of Submerged Motor Pumps : Influence of Long Seal on the Stability of Fluid Machinery

he influence of dynamic fluid reaction forces and moments of a long annular seal on the stability of fluid machinery was investigated. The stability analysis was carried out by using a submerged motor pump in a circulation boiler, in order to explain the effect of the long seal. In the stability analysis, the individual contributions of the fluid forces and moments due to rotor conical and cylindrical whirl movements were evaluated according to logarithmic decrements. As a result, the individual contributions depend on the mode shapes of the vibration. Fluid forces acting on the long seal due to conical and cylindrical whirl movements should not be ignored because they play an important role in the stability.