Instantaneous Center Research Articles

Sequential damage assessment of the posterolateral complex of the knee joint: a finite element study

BackgroundThe posterolateral complex (PLC), which consists of the popliteus tendon (PT), lateral collateral ligament (LCL), and popliteofibular ligament (PFL), is an indispensable structure of the knee joint. The aim of this study was to explore the functionality of the PLC by determining the specific role of each component in maintaining posterolateral knee stability.MethodsA finite element (FE) model was generated based on previous material property data and magnetic resonance imaging of a volunteer’s knee joint. The injury order of the PLC was set as LCL, PFL, and PT. A combined compressive load of 1150 N and an anterior tibial load of 134 N was applied to the tibia to investigate tibial displacement (TD). Tibial external rotation (TER) and tibial varus angulation (TVA) were measured under bending motions of 5 and 10 Nm. The instantaneous axis of rotation (IAR) of the knee joint under different rotation motions was also recorded.ResultsThe TD of the intact knee under a combined compressive load of 1150 N and an anterior tibial load of 134 N matched the values determined in previous studies. Our model showed consistent increases in TD, TVA, and TER after sequential damage of the PLC. In addition, sequential disruption caused the IAR to shift superiorly and laterally during varus rotation and medially and anteriorly during external rotation. In the dynamic damage of the PLC, LCL injury had the largest effect on TD, TVA, TER, and IAR.ConclusionsSequential injury of the PLC caused considerable loss of stability of the knee joint according to an FE model. The most significant structure of the PLC was the LCL.

Vortex identification methods applied to wind turbine tip vortices

Abstract. This study describes the impact of postprocessing methods on the calculated parameters of tip vortices of a wind turbine model when tested using particle image velocimetry (PIV). Several vortex identification methods and differentiation schemes are compared. The chosen methods are based on two components of the velocity field and their derivatives. They are applied to each instantaneous velocity field from the dataset and also to the calculated average velocity field. The methodologies are compared through the vortex center location, vortex core radius and jittering zone. Results show that the tip vortex center locations and radius have good comparability and can vary only a few grid spacings between methods. Conversely, the convection velocity and the jittering surface, defined as the area where the instantaneous vortex centers are located, vary between identification methods. Overall, the examined parameters depend significantly on the postprocessing method and selected vortex identification criteria. Therefore, this study proves that the selection of the most suitable postprocessing methods of PIV data is pivotal to ensure robust results.

Rattle Dynamic Model and Vibration Behaviors of Noncircular Face Gear

Abstract Noncircular face gear (NFG) is a new type of variable transmission ratio gear mechanism. Based on nonlinear dynamic theory of gear, the rattling behavior of the NFG under multifrequency excitation was studied. The generalized transmission ratio function of the NFG with closed pitch curve was constructed by Fourier series. The nonlinear relative displacement between teeth was described by an analytical expression during the process of time-varying transmission. Considering the factors of time-varying instantaneous center, meshing stiffness, transmission error, and backlash, a nonlinear dynamic model of the gear was established with the rotational angle as the independent variable. The dynamical responses were calculated by Runge–Kutta method to analyze the effects of the input speed, load torque, transmission ratio coefficient, and error on rattling behaviors. The results show that under the action of combined excitation of time-varying instantaneous center and meshing stiffness, the rattle of noncircular gear is more likely to occur. As the increase in input speed, error, and range of transmission ratio variation or the decrease of load, the NFG appears no rattling, unilateral, and bilateral rattle successively and the rattling intensity increases accordingly. The rattling threshold speed can be improved by increasing the accuracy and load of gear or decreasing the range of the transmission ratio.

Algorithmic Workspace Programming of the Collaborative Multi-Robots

In the present study, the Controllable Instantaneous Screw Axes (C-ISA) 1 and C-ISA 2 shape variable angles are modified independently to realize various rule-based work spaces and trajectories for multi collaborative robot control. The toolbox developed previously is used to obtain the algorithm of the workspaces for 2-RR collaborative multi-robots herein. Six collaborative multi-robots are exploited to design the intersecting workspaces with generated trajectories. The classifications of the workspaces are unveiling the boundaries of the collaborations for the six multi-robots of the 2-RR (Revolute Revolute). The recent developments are showing that the multi-robots are embedding into the automation systems to achieve the novel requirements of the challenging technology. Therefore, the workspace algorithms developed herein are prepared to be utilized by these automation systems.

Equivalent linkage representation of a railway wheelset for dynamic simulation with kinematic non-linearities

In this work, a four-link serial-chain mechanism which is an equivalent representation of railway wheelset is proposed. Through this representation, it has been shown that the concepts like instantaneous roll centre, dynamically varying link lengths, and shape constraints can be used to account for wheel–rail contact into the existing multibody formulation. An outline of the framework is described for dynamic analysis of a suspended wheelset model. It is possible to conveniently include kinematic non-linearities into the equations of motion. Usually, these terms are overlooked while using elastic approach for wheel–rail contact. Essentially, benefits of two conventionally followed approaches, namely, elastic, and constrained contact, are exploited in this work. Through a parametric study, it was found that such nonlinear terms have significant impact on hunting stability of wheelsets having high conicity.

Analysis of a tumbling motion using a clustering algorithm on dual-piv measurements: application to the in-cylinder flow of a miller cycle engine

This paper aims to study the internal aerodynamics of a Miller cycle gasoline engine. This cycle uses an over-expanded stroke to recover more work, for the same amount of fuel, than the classical Otto cycle. To achieve this, the effective compression stroke is made smaller than the expansion one by closing the intake valves prematurely. The in-cylinder tumble flow then stops being driven by the valve jet before the piston reaches the bottom dead center, which disturbs the movement. The flow is observed here on a motored single-cylinder transparent engine coupled to a dual-PIV system. This system allows two velocity fields per engine cycle to be measured. The temporal evolution of the flow structures could thus be followed, while keeping the high number of instantaneous fields measured by the traditional PIV systems. The data are then well adapted to statistical analysis. A clustering analysis method, using the k-means algorithm and adapted to dual-PIV data, is described here. The first part presents a method defining a criterion on the instantaneous center of rotation of the tumble motion that can improve the rotation rates by 17%. A second analysis classifies the velocity fields into three groups of strong, medium and weak rotation intensity. The evolution of the characteristic quantities of each group shows that the movements with high rotation rates, created upstream of the compression phase, can give high turbulence rates close to the top dead center of the piston.Graphical abstract

Torque- and Muscle-Driven Flexion Induce Disparate Risks of In Vitro Herniation: A Multiscale and Multiphasic Structure-Based Finite Element Study.

The intervertebral disc is a complex structure that experiences multiaxial stresses regularly. Disc failure through herniation is a common cause of lower back pain, which causes reduced mobility and debilitating pain, resulting in heavy socioeconomic burdens. Unfortunately, herniation etiology is not well understood, partially due to challenges in replicating herniation in vitro. Previous studies suggest that flexion elevated risks of herniation. Thus, the objective of this study was to use a multiscale and multiphasic finite element model to evaluate the risk of failure under torque- or muscle-driven flexion. Models were developed to represent torque-driven flexion with the instantaneous center of rotation (ICR) located on the disc, and the more physiologically representative muscle-driven flexion with the ICR located anterior of the disc. Model predictions highlighted disparate disc mechanics regarding bulk deformation, stress-bearing mechanisms, and intradiscal stress-strain distributions. Specifically, failure was predicted to initiate at the bone-disc boundary under torque-driven flexion, which may explain why endplate junction failure, instead of herniation, has been the more common failure mode observed in vitro. By contrast, failure was predicted to initiate in the posterolateral annulus fibrosus under muscle-driven flexion, resulting in consistent herniation. Our findings also suggested that muscle-driven flexion combined with axial compression could be sufficient for provoking herniation in vitro and in silico. In conclusion, this study provided a computational framework for designing in vitro testing protocols that can advance the assessment of disc failure behavior and the performance of engineered disc implants.

The dynamic rotation axis of ulnohumeral joint during active flexion-extension: an in vivo 4-dimensional computed tomography analysis

BackgroundAs the collateral ligament reconstruction becomes more common to perform, the knowledge between the collateral ligament reconstruction and the elbow rotation axis is still ambiguous. The purpose of this study was to investigate the location of the intersections between the elbow rotation axis and medial and lateral aspect of the humerus.MethodsFour-dimensional computed tomography (4D CT) scan was designed to obtain the images from 8 participants. The instantaneous rotation axis was created according to the trochlea notch of the ulna in the Rapidform XO software. Then the intersections between the instantaneous rotation axis and the medial and lateral aspect of the humerus were identified in the Geomagic Wrap software. Landmark coordinate systems of the distal humerus was created.ResultThe intersections in the medial aspect of the humerus were mostly located in the superior and posterior quadrant and showed the trend from anterior-superior to posterior-superior with the increment of the elbow flexion. The intersections in the lateral aspect of the humerus were mostly located in the middle half of the anterior quadrant and showed the trend from posterior-inferior to anterior-superior with the increment of the elbow flexion.ConclusionThere’s no isometric point for medial collateral ligament (MCL) and lateral ulnar collateral ligament (LUCL) reconstruction. The isometric area for MCL reconstruction should be considered at the superior and posterior quadrant of the medial aspect of the humerus. The isometric area for LUCL reconstruction should be considered at the middle half of the anterior quadrant of the lateral aspect of the humerus.Trial registrationThis work was supported by the National Natural Science Foundation of China [No.81911540488] in 07/01/2019.

Effect of PCV and attitude on the precise orbit determination of Jason-3 satellite

Abstract Satellite attitude modes and antenna phase center variations have a great influence on the Precise Orbit Determination (POD) of Low Earth Orbit satellites (LEOs). Inaccurate information about spacecraft attitude, phase center offsets and variations in the POD leads to orbital error. The Jason-3 satellite experienced complex attitude modes which are fixed, sinusoidal, ramp-up/down and yaw-flip. Therefore, it is necessary to properly construct the attitude model in the process of POD especially when there is no external attitude data. For the antenna phase center correction, the PCO which is the deviation between Antenna Reference Point (ARP) and Mean Antenna Phase Center (MAPC) usually can be calibrated on the ground accurately, but the PCV which is the deviation between Instantaneous Antenna Phase Center (IAPC) and Mean Antenna Phase Center (MAPC) will change greatly with the change of space environment. Residual approach can be used to estimate the receiver PCV map. In this paper, we collected the on-board GPS data of Jason-3 satellite from January 2019 and analyzed the impacts of PCV and spacecraft attitude on the orbit accuracy by performing the reduced-dynamic POD. Compared with the reference orbit released by the Centre National d’Études Spatiales (CNES), using the PCV map can reduce the Root Mean Square (RMS) of orbit differences in the Radial (R), Along-track (T), Cross-track (N) and 3D direction about 0.3, 1.0, 0.9, and 1.4 mm. Based on the estimated PCV map, the orbit accuracy in R, T, N and 3D direction is 1.24, 2.81, 1.17, and 3.29 cm respectively by using the measured attitude data. When using the attitude model, the orbit accuracy in R, T, N and 3D directions is 1.60, 3.54, 1.33, and 4.13 cm, respectively. The results showed that the combination of measured attitude data and modeled PCV map can obtain the better orbit solution. It is essential to build a corresponding model in high-precision orbit determination, when there is no attitude data and PCV map.

Comparison between Helical Axis and SARA Approaches for the Estimation of Functional Joint Axes on Multi-Body Modeling Data

Functional methods usually allow for a flexible and accurate representation of joint kinematics and are increasingly implemented both for clinical and biomechanics research purposes. This paper presents a quantitative comparison between two widely adopted methods for functional axis estimation, that is, the helical axis theory and the symmetrical axis of rotation approach (SARA). To this purpose, a multi-body model was developed to simulate the lower limb of a subject. This model was designed to reproduce different motion patterns, that is, by selecting the active degrees of freedom of the simulated ankle joint. Thanks to virtual markers attached to each segment, the multi-body model was used to generate simulated motion capture data that were then analyzed by instantaneous helical axes and SARA algorithms. To achieve a synthetic representation of joint kinematics, a mean helical axis and an average SARA functional axis were estimated, along with dispersion parameters and rms distance data that were used to quantitatively assess the performance of each method. The sensitivity of each algorithm to different combinations of range and speed of motion, scattering of marker clusters, sampling rate, and additive noise on markers’ trajectories, was finally evaluated.

Onset of wake meandering for a floating offshore wind turbine under side-to-side motion

Wind turbine wakes, being convectively unstable, may behave as an amplifier of upstream perturbations and make downstream turbines experience strong inflow fluctuations. In this work, we investigate the effects of the side-to-side motion of a floating offshore wind turbine (FOWT) on wake dynamics using large-eddy simulation and linear stability analysis (LSA). When the inflow turbulence intensity is low, simulation results reveal that the turbine motion with certain Strouhal numbers$St = fD/U_\infty \in (0.2,0.6)$(where$f$is the motion frequency,$D$is the rotor diameter, and$U_\infty$is the incoming wind speed), which overlap with the Strouhal numbers of wake meandering induced by the shear layer instability, can lead to wake meandering with amplitudes being one order of magnitude larger than the FOWT motion for the most unstable frequency. For high inflow turbulence intensity, on the other hand, the onset of wake meandering is dominated by the inflow turbulence. The probability density function of the spanwise instantaneous wake centres is observed being non-Gaussian and closely related to that of the side-to-side motion. This complements the existing wake meandering mechanisms, that the side-to-side motion of an FOWT can be a novel origin for the onset of wake meandering. It is also found that LSA can predict the least stable frequencies and the amplification factor with acceptable accuracy for motion amplitude$0.01D$. Effects of nonlinearity are observed when motion amplitude increases to$0.04D$, for which the most unstable turbine oscillations shift slightly to lower frequencies and the amplification factor decreases.

Обґрунтування впливу зміни коефіцієнта міжосьового розподілу гальмівної сили на керованість легкового автомобіля

The article considers the change of the radius of the instantaneous center of rotation of a car moving along a curved trajectory during braking, taking into account the lateral input of the wheels of both axles of cars, both equipped with electronic tracking systems and not equipped with such. A criterion for assessing the controllability of cars moving on a curved trajectory in a braked state, by comparing the ratio of the current speed of the car to the longitudinal base with the ratio of the coefficients of lateral tire input to the product of the longitudinal base of the car, mass and cosines. It is established that the radius of instantaneous rotation of the longitudinal axis of the car moving along a curved trajectory during braking depends on the speed of the center of mass of the car, the coefficient of axle distribution of braking force, physical characteristics of applied tires, steering wheel angle and design and weight parameters. As a result, it allows you to set controllability. The authors obtained dependences that will create new algorithms for the operation of modern electronic control systems for stabilizing the longitudinal axis of a braked car, taking into account the speed of the car, its design and weight characteristics, the main characteristics of its braking system (coefficient of axle braking force distribution), physical characteristics used tires on wheels and connect them to the angles of the steered wheels, controlling the deviation of the longitudinal axis, which allows the driver to maintain the possibility of quite sharp maneuvers directly in the braking process, moving along a curved trajectory.

A Screw Theory Approach to Computing the Instantaneous Rotation Centers of Indeterminate Planar Linkages

This paper presents a screw theory approach for the computation of the instantaneous rotation centers of indeterminate planar linkages. Since the end of the 19th century, the determination of the instantaneous rotation, or velocity centers of planar mechanisms has been an important topic in kinematics that has led to the well-known Aronhold–Kennedy theorem. At the beginning of the 20th century, it was found that there were planar mechanisms for which the application of the Aronhold–Kennedy theorem was unable to find all the instantaneous rotation centers (IRCs). These mechanisms were denominated complex or indeterminate. The beginning of this century saw a renewed interest in complex or indeterminate planar mechanisms. In this contribution, a new and simpler screw theory approach for the determination of indeterminate rotation centers of planar linkages is presented. The new approach provides a simpler method for setting up the equations. Furthermore, the algebraic equations to be solved are simpler than the ones published to date. The method is based on the systematic application of screw theory, isomorphic to the Lie algebra, se(3), of the Euclidean group, SE(3), and the invariant symmetric bilinear forms defined on se(3).

Design and Control of an Adaptive Knee Joint Exoskeleton Mechanism with Buffering Function.

A knee exoskeleton with an adaptive instantaneous rotation center and impact absorption is used for rehabilitation. Due to the human knee joint’s special physiological structure and motion characteristics, the exoskeleton mechanism needs to be designed for both static and dynamic aspects. Therefore, a novel knee exoskeleton mechanism was designed. To adapt to the rotation center of the knee joint, a mechanism with cross-configuration was designed according to the equivalent degree of freedom and the stiffness of the springs was calculated by its combination with gait motion, so that the average force of the human body was minimized. A dynamic model of the exoskeleton was established. To overcome the uncertainty in the parameters of the human and robotic limbs, an adaptive controller was designed and a Lyapunov stability analysis was conducted to verify the system. A simulation was conducted and experimental results show that the tracking error of the knee joint angle between the actual and desired trajectory was within the range of −1 to 1 degree and indicate the effectiveness of the controller.

Effect of the soft tissue artifact on marker measurements and on the calculation of the helical axis of the knee during a gait cycle: A study on the CAMS-Knee data set

The soft tissue artifact (STA) is a phenomenon occurring when the motion of bones or anatomical segments is measured by means of skin markers: the biological tissues between the markers and the bone produce a relative motion bone-markers that leads to inaccuracies in the estimation of rigid body poses or kinematics. The aim of this study was to quantify the STA by exploiting a recently published gait analysis dataset. The dataset was composed of six adult subjects with a total knee arthroplasty who underwent gait analysis trials. The motion of the knee was concurrently recorded by means of (i) fluoroscopy imaging and (ii) an optoelectronic system and redundant markers attached to the thigh and shank. The STA was studied by comparing the results calculated on the marker sets with the results obtained from the fluoroscopy data. The stance and swing phases were considered separately. Rigid STA motion and local STA deformation were studied separately. In addition to previous studies, the instantaneous helical axis (IHA) of the knee was calculated and the effect of the STA on its calculation was assessed.The largest rigid-motion STA effect was observed on the thigh cluster (~10 deg. and ~ 18 mm). The shank cluster was mainly affected during the swing phase (~7 deg. and ~ 17 mm). The local STA deformation affected differently the markers. The largest effect was ~16 mm and the lowest was ~4 mm. The estimation of the IHA was not reliable when based only on markers, having an estimation error of ~17 deg. and ~ 25 mm. A high variability of results across subjects was observed.

A Cadaver-Based Biomechanical Evaluation of a Novel Posterior Approach to Sacroiliac Joint Fusion: Analysis of the Fixation and Center of the Instantaneous Axis of Rotation.

PurposeThe purpose of this study was to assess the stabilizing effect of a posterior joint fixation technique using a novel cortical allograft implant in unilateral and bilateral fixation constructs. We hypothesize that fixation would reduce the joint’s range of motion during flexion-extension, axial rotation, and lateral bending loads. We also hypothesize that fixation would shift the center of the instantaneous axis of rotation during the predominant flexion-extension motions towards the implant’s location, and that this shift would be correlated with the reduction in flexion-extension range of motion.Materials and MethodsSix cadaveric sacroiliac joint specimens were tested under intact, unilateral fixation, and bilateral fixation conditions. The total range of motion (ROM) of the sacroiliac joint in flexion–extension, lateral bending, and axial rotation were evaluated by an optical tracking system, in a multidirectional flexibility pure moment model, between ± 7.5 Nm applied moment loads. The centers of the instantaneous axis of rotation (cIAR) of the sacroiliac joint were evaluated during flexion-extension loading. A correlation analysis was performed between the ROM reduction in flexion-extension upon implantation and shift of the cIAR to the graft implantation site.ResultsUnilateral and bilateral fixations generated sacroiliac joint ROM reductions in flexion-extension, lateral bending, and axial rotation motions. Fixation shifted the cIAR to the graft implantation site. Reduction in the total range of motion had a moderate correlation with the shift of the cIAR.ConclusionOur novel posterior approach presents a multifaceted mechanism for stabilizing the joint: first, by the reduction of the total range of motion in all planes of motion; second, by shifting the centers of the instantaneous axis of rotation towards the implant’s location in the predominant plane of motion, ensuring little to no motion at the implantation site, thus promoting fusion in this region.

Síntesis mediante algoritmos genéticos de mecanismos articulados de seis barras rígidas para prótesis de rodilla

Using the method of genetic algorithms, the synthesis process of a Watt I type six-bar flat mechanism is developed and applied to the design of a polycentric knee prosthesis to guarantee stability in the extension and total flexion phase of the knee during the knee. gait cycle of a person. Six precision points of the trajectory of the instantaneous center of rotation of the coupling link were selected, with a population of one thousand individuals formed with the lengths of links and angles of movement of the mechanism. The fitness function was obtained with the Freudenstein equation applied to two four-bar mechanisms that make up the prosthesis and the design restrictions were: minimum and maximum bar dimensions, Grashof criterion, angular relationships for ternary elements, transmission angle and instantaneous inactive joints.

Defect free optimization of a polycentric prosthetic knee design using imperialist competition-inspired optimization method

The disability of lower limbs is one of the major problems facing human lives. In order to restore the missing functionality and aesthetic feature of the amputee's locomotion, finding the optimal design of the human lower limb knee prosthesis is crucial. This paper focuses the design optimization of a four bar knee mechanism capable to reproduce the complex flexion/extension knee joint motion in the sagittal plane with variable instantaneous center of rotation positions. Thus an optimization approach with appropriate constraints is formulated in order to consider the degree of compatibility between the instantaneous center of rotation trajectories of the human reference knee joint and the four bar knee mechanism. To solve this high nonlinear optimization problem, an algorithm based on multi-objective modified imperialist competitive method is proposed where all the constraints are managed with the penalty method. The results obtained by the multi-objective modified imperialist competitive method showed the capability to reach a small tracking error. The obtained results prove the effectiveness of the proposed optimization approach for the optimal synthesis of the four bar knee mechanism, compared with other literature techniques.

Modjaw® device: Analysis of mandibular kinematics recorded for a group of asymptomatic subjects

ABSTRACT Objective To assess the repeatability and kinematic data of Modjaw® recordings from a group of asymptomatic patients. Methods Modjaw® mandibular kinematic data were recorded for 22 asymptomatic volunteers (DC/TMD questionnaire). Sagittal (SCI at 3 and 5 mm) and transversal (TCI at 4 mm) condylar inclination values of the instantaneous center of rotation were measured over two recording sessions. The repeatability of recordings was determined from the intraclass correlation coefficient (ICC), which is based on a one-way random-effects ANOVA. Results The repeatability of recordings was found to be good to excellent. The mean TCI in mediotrusion was 7.1° ± 5.1, and the mean SCI in protrusion was 51.07° ± 9.43. Conclusion The Modjaw® device reliably records the patient’s real hinge axis kinematics during functional mandibular movements. Data can be transferred with the patient’s personal reference plane and digital casts to the CAD/CAM software.

Instantaneous center/axis of rotation for planar and three-dimensional motion

This article discusses a direct analytical method for calculating the instantaneous center of rotation and the instantaneous axis of rotation for the two-dimensional and three-dimensional motion, respectively, of rigid bodies. In the case of planar motion, this method produces a closed-form expression for the instantaneous center of rotation based on a single point located on the rigid body. It can also be used to derive closed-form expressions for the body and space centrodes. For three-dimensional, rigid body motion, an extension of the technique used for planar motion locates a point on the instantaneous axis of rotation, which is parallel to the body angular velocity vector. In addition, methods are demonstrated that can be used to map the body and space cones for general rigid body motion, and locate the fixed point for the body.