Kinematic Restrictions Research Articles

Personalized alignment in total knee arthroplasty: current concepts.

Traditionally in total knee arthroplasty (TKA), a post-operative neutral alignment was the gold standard. This principle has been contested as functional outcomes were found to be inconsistent. Analysis of limb alignment in the non-osteoarthritic population reveals variations from neutral alignment and consideration of a personalized or patient-specific alignment in TKA is challenging previous concepts. The aim of this review was to clarify the variations of current personalized alignments and to report their results. Current personalized approaches of alignment reported are: kinematic, inverse kinematic, restricted kinematic, and functional. The principle of “kinematic alignment” is knee resurfacing with restitution of pre-arthritic anatomy. The aim is to resurface the femur maintaining the native femoral joint line obliquity. The flexion and extension gaps are balanced with the tibial resection. The principle of the “inverse kinematic alignment” is to resurface the tibia with similar medial and lateral bone resections in order to keep the native tibial joint line obliquity. Gap balancing is performed by adjusting the femoral resections. To avoid reproducing extreme anatomical alignments there is “restricted kinematic alignment” which is a compromise between mechanical alignment and true kinematic alignment with a defined safe zone of alignment. Finally, there is the concept of “functional alignment” which is an evolution of kinematic alignment as enabling technology has progressed. This is obtained by manipulating alignment, bone resections, soft tissue releases, and/or implant positioning with a robotic-assisted system to optimize TKA function for a patient’s specific alignment, bone morphology, and soft tissue envelope. The aim of personalizing alignment is to restore native knee kinematics and improve functional outcomes after TKA. A long-term follow-up remains crucial to assess both outcomes and implant survivorship of these current concepts.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ РАЗБРОСА ДЕЙСТВИТЕЛЬНЫХ РАЗМЕРОВ ЗВЕНЬЕВ НА ПЕРЕДАТОЧНУЮ ФУНКЦИЮ МЕХАНИЗМА СКАЛОЧНОЙ ПОЛУАВТОМАТИКИ

In this work, the analysis of real deviations from the nominal dimensions links, and their cumulative effect on the final movement of the chain linkage element rolling semiautomatic mechanism. The considered mechanism was converted to an equivalent one, consisting of lower translational and rotational kinematic pairs. In the course of the structural analysis, the mechanism was divided into Assur groups in order to simplify further kinematic calculations. The calculation was carried out sequentially for each of the structural groups separately. Based on this, a mathematical model of the kinematics of a rolling semiautomatic mechanism was developed, taking into account the real size of the links, that is, possible deviations of the links size from the nominal values for any combination of them. Using a specific example with the given installation dimensions of the mechanism, the transfer function of the output link (wedge) is built, and the range of its possible change is determined according to the specified dimensional tolerances. Combinations of link sizes for the boundaries of the range of change of the transfer function have been determined It is shown that with the tolerances indicated in accordance with the Unified system of tolerances and fits, the deviation of the position of the output link at the extreme position of the input link (pusher) can reach ±10 of that calculated by the nominal dimensions. This model can be used to solve the problems of optimal selection of tolerances and reduce the cost of manufacturing a product, based on the kinematic restrictions imposed on the functionality of the mechanism. The proposed approach to the construction and analysis of analytical mathematical models can be relevant for a wide variety of industries: machine tool building, engine building, weapons industry and aircraft building, especially where mechanisms are used that form long kinematic chains.

Efficient Path Planing for Articulated Vehicles in Cluttered Environments.

Motion planning and control for articulated logistic vehicles such as tugger trains is a challenging problem in service robotics. The case of tugger trains presents particular difficulties due to the kinematic complexity of these multiarticulated vehicles. Sampling-based motion planners offer a motion planning solution that can take into account the kinematics and dynamics of the vehicle. However, their planning times scale poorly for high dimensional systems, such as these articulated vehicles moving in a big map. To improve the efficiency of the sampling-based motion planners, some approaches combine these methods with discrete search techniques. The goal is to direct the sampling phase with heuristics provided by a faster, precociously ran, discrete search planner. However, sometimes these heuristics can mislead the search towards unfeasible solutions, because the discrete search planners do not take into account the kinematic and dynamic restrictions of the vehicle. In this paper we present a solution adapted for articulated logistic vehicles that uses a kinodynamic discrete planning to bias the sampling-based algorithm. The whole system has been applied in two different towing tractors (a tricycle and a quadricycle) with two different trailers (simple trailer and synchronized shaft trailer).

3D human pose estimation model using location-maps for distorted and disconnected images by a wearable omnidirectional camera

We address a 3D human pose estimation for equirectangular images taken by a wearable omnidirectional camera. The equirectangular image is distorted because the omnidirectional camera is attached closely in front of a person’s neck. Furthermore, some parts of the body are disconnected on the image; for instance, when a hand goes out to an edge of the image, the hand comes in from another edge. The distortion and disconnection of images make 3D pose estimation challenging. To overcome this difficulty, we introduce the location-maps method proposed by Mehta et al.; however, the method was used to estimate 3D human poses only for regular images without distortion and disconnection. We focus on a characteristic of the location-maps that can extend 2D joint locations to 3D positions with respect to 2D-3D consistency without considering kinematic model restrictions and optical properties. In addition, we collect a new dataset that is composed of equirectangular images and synchronized 3D joint positions for training and evaluation. We validate the location-maps’ capability to estimate 3D human poses for distorted and disconnected images. We propose a new location-maps-based model by replacing the backbone network with a state-of-the-art 2D human pose estimation model (HRNet). Our model is a simpler architecture than the reference model proposed by Mehta et al. Nevertheless, our model indicates better performance with respect to accuracy and computation complexity. Finally, we analyze the location-maps method from two perspectives: the map variance and the map scale. Therefore, some location-maps characteristics are revealed that (1) the map variance affects robustness to extend 2D joint locations to 3D positions for the 2D estimation error, and (2) the 3D position accuracy is related to the 2D locations relative accuracy to the map scale.

The Effect of Additional Shear Strains Induced by Die Rotation on the Radial Pressing of Metal Powder Billets

The axial pressing of a tubular metal powder billet accompanied by simultaneous rotation of the billet synchronously with the inner rod relative to the outer die wall has been considered. Such a compaction pattern for nonporous compact materials is known as ‘high-pressure tube twisting’ and used to improve the structure and design features of the tubular product by strain accumulation. Unlike a compact material, the behavior of a powder billet is determined both by hardening its solid phase and compaction with a gradual decrease in pores volume. These factors specify the peculiar behavior of porous materials under the formulated above conditions, which requires the plasticity theory for porous bodies to be applied. Additional assumptions concerning kinematic restrictions enabled finding explicit expressions for hardening and compaction pressure in analytical form. The derived analytical solution is multi-parametric and describes the influence exerted on the compaction pressure by hardening constants of the material, initial and final density of the compacts, and degree of mutual die walls rotation. The performed analysis allowed concluding that the short-term application of shear strains induced by the mutual rotation of the die elements reduces, in any case, the value of the current operating pressure during compaction. On the other hand, in the long-term compaction process, the hardening of the solid phase in a porous body caused by additional shear strains can lead to an increase in radial pressure at the same final density. The change from the pressure decrease stage to pressure increase stage significantly depends on how hard the powder material is. Therefore, the die is advised to be rotated for powders produced of a nearly ideal plastic material. In most cases, the rotation of a die throughout the entire pressing process is advisable only for sufficiently porous billets subjected to very insignificant compaction. In the case of billets compacted to small porosities, the die walls should be rotated only at the end of the compaction process.

An anisotropic beam theory based on the extension of Boley’s method

The objective of this contribution is the computation of the Airy stress function for anisotropic beam-type structures. In the first part an iterative procedure is applied for the determination of the stress function by means of Boley’s method. This method was successfully applied by Boley for two-dimensional (2D) isotropic plates under plane stress conditions in order to compute the displacement field and the stress distribution. In this contribution a higher order theory for anisotropic beams is derived with Boley’s iterative procedure and an analytical formula for the Airy stress function is given. In the second part of the paper a beam with rectangular cross section is considered and the derived anisotropic beam model is compared to two-dimensional (2D) finite element results performed in ABAQUS. Two examples are studied: first a cantilever with constant distributed load is investigated, then an axially end-loaded redundant beam that is clamped at the one end and simply supported at the other end is studied. In both cases the analytical results are in perfect agreement with the ABAQUS outcome. Furthermore the effects of different kinematic restrictions for realizing clamped boundary conditions are investigated and compared. For the redundant axially loaded beam it is shown that the Bernoulli-Euler beam theory yields misleading results because it does not take into account shear coupling. This phenomenon is included in our presented solution for anisotropic beams.

Investigating the normal and tangential peeling behaviour of gecko spatulae using a coupled adhesion-friction model

ABSTRACT The present work investigates the normal and tangential peeling behaviour of a gecko spatula using a coupled adhesion-friction model. The objective is to explain the strong attachment and easy detachment behaviour of the spatulae as well as to understand the influence of various parameters on the pull-off forces. Using nonlinear finite element computations, it is shown that during tangentially-constrained peeling the partial sliding of the spatula pad near the peeling front stretches the spatula, thus increasing the strain energy and leading to high pull-off forces. The model is used to investigate the influence of various parameters on the pull-off forces – such as the peeling angle, spatula shaft angle, strip thickness, and material stiffness. The model shows that increasing the spatula pad thickness beyond a certain level does not lead to a significant increase in the attachment forces. Further, the easy detachment behaviour of geckos is studied under tangentially-free peeling conditions. It is found that the spatulae readily detach from the substrate by changing their shaft angle and eventually peel vertically like a tape. Since the present computational model is not limited by geometrical, kinematical, and material restrictions, it can be employed to analyse similar biological adhesive systems.

Restoring the constitutional alignment with a restrictive kinematic protocol improves quantitative soft-tissue balance in total knee arthroplasty: a randomized controlled trial

AimsIt is unknown whether kinematic alignment (KA) objectively improves knee balance in total knee arthroplasty (TKA), despite this being the biomechanical rationale for its use. This study aimed to determine whether restoring the constitutional alignment using a restrictive KA protocol resulted in better quantitative knee balance than mechanical alignment (MA).MethodsWe conducted a randomized superiority trial comparing patients undergoing TKA assigned to KA within a restrictive safe zone or MA. Optimal knee balance was defined as an intercompartmental pressure difference (ICPD) of 15 psi or less using a pressure sensor. The primary endpoint was the mean intraoperative ICPD at 10° of flexion prior to knee balancing. Secondary outcomes included balance at 45° and 90°, requirements for balancing procedures, and presence of tibiofemoral lift-off.ResultsA total of 63 patients (70 knees) were randomized to KA and 62 patients (68 knees) to MA. Mean ICPD at 10° flexion in the KA group was 11.7 psi (SD 13.1) compared with 32.0 psi in the MA group (SD 28.9), with a mean difference in ICPD between KA and MA of 20.3 psi (p < 0.001). Mean ICPD in the KA group was significantly lower than in the MA group at 45° and 90°, respectively (25.2 psi MA vs 14.8 psi KA, p = 0.004; 19.1 psi MA vs 11.7 psi KA, p < 0.002, respectively). Overall, participants in the KA group were more likely to achieve optimal knee balance (80% vs 35%; p < 0.001). Bone recuts to achieve knee balance were more likely to be required in the MA group (49% vs 9%; p < 0.001). More participants in the MA group had tibiofemoral lift-off (43% vs 13%; p < 0.001).ConclusionThis study provides persuasive evidence that restoring the constitutional alignment with KA in TKA results in a statistically significant improvement in quantitative knee balance, and further supports this technique as a viable alternative to MA.Cite this article: Bone Joint J. 2020;102-B(1):117–124

Backward nucleon production by heavy baryonic resonances in proton-nucleus collisions

The production of backward nucleons, $N(180^\circ)$, at $180^\circ$ in the nuclear target rest frame in proton-nucleus ($\mathrm{p}+A$) collisions is studied. The backward nucleons appearing outside of the kinematically allowed range of proton-nucleon ($\mathrm{p}+N$) reactions are shown to be due to secondary reactions of heavy baryonic resonances produced inside the nucleus. Baryonic resonances $R$ created in primary $\mathrm{p}+N$ reactions can change their masses and momenta due to successive collisions $R+N\rightarrow R +N $ with other nuclear nucleons. Two distinct mechanisms and kinematic restrictions are studied: the reaction $R+N\rightarrow N(180^\circ)+N$ and the resonance decay $R\rightarrow N(180^\circ)+\pi$. Simulations of $\mathrm{p}+A$ collisions using the Ultra-relativistic Quantum Molecular Dynamics model support these mechanisms and are consistent with available data on proton backward production.

Device for the study of the friction coefficient in the bolt-chain link joint

The friction which appears in chain drives has an importantinfluence on their dynamic behaviour, wear and lifetime. The most significant friction and also wear is given by the bolt and chain link joint; in most of the cases this led to changes of the chain geometry and failures. Due to this, the study of the friction in the chain joints is required, but also difficult because of some particularities, as bolt and chain link reduced dimension, the oscillate motion in joint, chain link load.The paper presents a device for the friction coefficient study in the chain link-bolt joint, according to the mentioned requirements. First, the device ensemble 3D model is presented; the geometrical and kinematical restrictions between the parts are also defined. Then, the finite element analysis on this model is realized and is achieved for different initial conditions. In the paper final part, the analysis results and conclusions are presented.

Simulación de Mecanismos

Objectives: In this work we show different simulated mechanisms virtually, their objective is to facilitate the qualitative and quantitative analysis of their kinematics; allowing to determine degrees of freedom, relation of times, mechanical advantage, mobility, positions, speeds and accelerations. Such an objective is achieved by simulating them for different positions using discretization and variable timing. Methodology: It consists of files of mechanisms with the corresponding files of links and electronic spreadsheets. The student must modify the dimensional, geometric and kinematic restrictions; remove them and install new ones; to observe the behavior of the mechanism as a system or of the links as integral parts. Contribution: Simplify the cognitive process of the kinematics of the mechanisms. It facilitates the understanding of the Euler and the Lagrange approaches. It allows to understand and evaluate the positions, speeds and accelerations; absolute, relative and apparent. The files of mechanisms and links are virtual, three-dimensional and allow their animation. Electronic spreadsheets control the restrictions of both the mechanisms and their links.

Minimally Constrained Flight Simulation in Wind Tunnel

Experimental studies on aircraft stability and performance can be enhanced by using a rig in which the aircraft model support approximates free flight within a wind tunnel. Such multi-degree-of-freedom wind tunnel rigs often impose kinematic restrictions on the aircraft model’s translational motion. This study investigates these kinematic effects, with particular attention to a spherical constraint in which the aircraft is held at the end of a fixed-length pivoting arm. Here, the motions of the aircraft and kinematic constraints are derived as differential-algebraic equations and assessed numerically. The impact is found mainly on translational motion with a negligible effect on the aircraft’s rotation. A concept to reduce these kinematic effects on the aircraft’s motion by applying an external force onto the aircraft is proposed. This compensation, which partially accounts for the constraints on the aircraft motion, is shown to reduce the effects of the arm, allowing for improved physical simulation.

Real Time System Design for a Mobile Manipulator

A mobile manipulator is defined as a mechanism composed by a serial manipulator located just above robotic platform. Besides, is a system with kinematic restrictions determined by an independent movement of the wheels and the degrees of freedom of the manipulator arm. The combination of the previous systems increases the advantages in terms of maneuverability, efficiency, range, between others. Another advantage of manipulator robot is the larger working space when it moves over a mobile platform allowing to reach different position on XY cartesian plane. Therefore, the design of a real-time system for a mobile manipulator will be shown in this paper.

Analysis of a single-edge micro cutting process in a hybrid parallel-serial machine tool

This paper presents a novel micro machining process as an alternative to other micro machining processes like micro milling. Its main advantage is the simplicity of the cutting tool geometry compared to other complex micro tools. The basis of this process consists of keeping the cutting tool always tangent to its trajectory. To achieve this goal, an innovative 6 degree-of-freedom parallel machine tool with high stiffness and with the tool tip precisely positioned, has been designed and built. The new machine is based on a hybrid device composed of three PRS (prismatic-revolution-spherical) parallel mechanisms with a linear XY stage and a C rotational axis. In order to determine the cutting load on the machine and consequently, its deformation, a resultant cutting tool force model has been developed which considers all the angles of the cutting process. A machining strategy has also been developed which takes into account the tool geometry and the kinematic restrictions of the machine tool. As a result of the kinematic and dynamic modelling of the machine, it has been possible to establish the level of precision for a given machining strategy. From the tests carried out, it is shown that the proposed machining process combined with the parallel machine tool, is an alternative to micro milling technology.

Analysis of lateral loading of pile groups using embedded beam elements with interaction surface

SummaryThe numerical simulation of soil‐pile interaction problems, by means of full 3D finite element models, involves a large number of degrees of freedom (DOF) and difficulties during the mesh generation process. In order to reduce the unknowns and simplify and properly analyze such class of geotechnical problems, the so‐called embedded beam elements (EBE) have recently been developed. In a preceding contribution of the authors, an improved EBE formulation, which brings into play the soil‐pile interaction surface, was proposed with the aim to localize material plasticity in the soil surrounding the pile. This embedded beam model couples two different finite elements, each described by distinct kinematics (ie, solid and beam). The coupling is incorporated in the formulation by means of kinematical constrains established over the solid and beam displacement fields on the interaction surface. One of the main advantages of the embedded elements is that the addition of beams structural members immersed within the 3D soil model does not represent a constraint for the solid mesh, which can be adopted independently from the beam mesh. In this paper, the lateral loading of pile groups is studied by means of the proposed EBE approach with elasto‐plastic interfaces. In order to represent a rigid cap, a master node and a special set of kinematical restrictions are incorporated into the formulation. The paper presents results obtained by means of the present formulation compared against other well‐established analysis methods and test results published in the literature, for both elastic and elasto‐plastic cases.

Use of kinematic restrictions in case of parralel spur gearing design

Since 1984 the design of the involute parallel spur gear is normalized by the Romanian standard STAS 12268-84 (Gearing cylinders with evolving teeth). This method of calculation has some drawback and some of its items may even confuse the designer. The present paper analyses the standard design method attempting to establish a set of kinematic limits of the gearing, in order to eliminate the successive modifications of calculated values of some parameters initially determined by using the standard.

Extending DualSPHysics with a Differential Variational Inequality: modeling fluid-mechanism interaction

This work details the coupling of a Smoothed Particle Hydrodynamics (SPH) fluid solver with a general-purpose Differential Variational Inequality (DVI) based non-smooth multibody dynamics solver, allowing for efficient and accurate modeling of fluid-mechanism interactions, an ubiquitous scenario in natural and industrial settings. The SPH fluid model (DualSPHysics) can deal with flow non-linearities, free-surface and intense topological changes, while the non-smooth dynamics model (Project Chrono) deals with discontinuous frictional contacts and kinematic restrictions. An open-source integrated framework to model fluid–structure–structure coupled systems is presented by implementing Project Chrono under DualSPHysics.The model is validated with fluid–structure–structure interaction cases. Both frictional and multi-restriction based behaviors are tested and simple convergence analysis are presented, showing that the model is capable of reproducing complex interactions. Several hypothetical cases are then presented, in order to demonstrate possible applications, showcasing a wide set of options useful for practitioners requiring the use of advanced fluid-mechanism models.

MODELS’ SUPERPOSITION AT MODELING THE SATURATION OF CARGO SPATIAL VIBRATIONS

Introduction. A solution of the problem of moving the load to a given distance is proposed in the article with the fulfillment of the condition for complete quenching of the uncontrollable pendulum spatial oscillations for the plane pendulum dynamical system with oscillations’ damping describing the load oscillations of the bridge crane on a flexible cable suspension in a separate vertical plane. Materials and methods. The recalculation principle of the time dependences of the cargo rope deviation from the dependence of the vertical acceleration, speed and movement of the load suspension on the freight trolley in a separate bridge plane or the freight trolley. The kinematic restrictions on the movement of the cargo suspension point in the form of the maximum achievable accelerations, speeds of the bridge and the truck of the crane are taken into account in the research. Results. The principle hypothesis of the swings’ superposition in the joint cargo movement of two mutually perpendicular vertical planes is confirmed with small deviation angles’ values of the load rope from the vertical position. Discussion and conclusion. The accuracy of the superposition of the bridge crane pendulum system flat models is evaluated in the process of suppressing the spatial cargo swings. The spatial cargo movement in two mutually perpendicular vertical planes could be simulated with sufficient accuracy for practical purposes using a relatively simple flat mathematical model of the loaded bridge crane pendulum system.

Simulation of a Mobile Manipulator on Webots

A mobile manipulator is a mobile platform with a mounted serial manipulator. A Mobile Manipulator is a system subject to its kinematic restrictions and the degrees of freedom of the manipulator arm mounted on it. These systems combine the advantages of mobile platforms and robotic arms, and reduce their disadvantages. For example, a mobile manipulator has larger working space when it has a mobile platform, as it offers more functionality during operation. For the previously mentioned in this work will be shown the implementation in the robotic simulation software Webots, a mobile manipulator that allows to determine its operation in a virtual environment

Optimal mobile robot path planning in the presence of moving obstacles

This paper presents an optimisation method to search for the optimal trajectory of an unmanned mobile robot while avoiding stationary and moving obstacles that may be in collision route. In order to meet the kinematic restrictions of the vehicle, the path is estimated using a finite-dimensional approximating space generated by B-splines basis functions. A penalised continuous functional is used to convert the constrained minimisation problem into an unconstrained one. The optimisation is performed through a genetic algorithm that searches the finite-dimensional space of the B-splines coefficients which determine the trajectory to be travelled. Experimental results with linear and nonlinear moving obstacle fields illustrate the estimated optimal trajectories.