Compliant Model Research Articles

An improved compliant contact force model using a piecewise function for impact analysis in multibody dynamics

Contact-impact problems have attracted more and more attention in mechanical multibody systems. In the past period of time, a few compliant contact force models have been put forward. However, some compliant contact force models are only applicable to a specific range of coefficient of restitution impact problems. And, some compliant contact force models have large errors with the actual situation. In order to reduce the errors, an improved compliant contact force model is proposed in this paper, which is applicable to the whole range of coefficient of restitution impact problems. In this work, the permanent deformation is taken into account during the contact process. Meanwhile, the method of piecewise fitting is used to reduce the errors in numerical solutions. Therefore, the improved compliant contact force model uses a piecewise function for the whole range of coefficient of restitution. In order to illustrate the situation, six independent contact force models are numerically analyzed by using Matlab codes. The result shows that the improved compliant contact force model in this paper is applicable to both soft and hard impact and nearer to the actual situation.

Economic model predictive control for obstacle-aided snake robot locomotion

Abstract This paper studies the application of economic model predictive control (MPC) to snake robot locomotion. The proposed MPC algorithm integrates the gait pattern creation into the closed loop by maximizing the forward snake velocity. We consider both purely planar locomotion as well as obstacle-aided locomotion. A compliant obstacle-snake contact model is introduced, rendering the interaction dynamics considered in the optimal control problem smooth. We illustrate the efficacy of the scheme by numerical simulations. The emerging gait patterns are undulatory and can make simultaneous use of anisotropic ground friction and obstacles.

A Graphical Toolkit for IEC 62264-2

Among the plethora of industrial standards available in the context of smart manufacturing, one series of standards is consistently being mentioned for dealing with manufacturing operations management: IEC 62264. Its second part provides a conceptual model for the description of production systems and their capabilities, including runtime information such as concrete maintenance schedules or achieved production goals. In this work, we present a concrete graphical syntax and toolkit for the creation and presentation of IEC 62264-2 compliant models, using techniques from model-driven (software) engineering. We have evaluated our tool by conducting a user study for assessing its usability and effectiveness.

A geometrical optics approach to encircled-flux compliant source modeling for multi-mode fiber illumination and connection attenuation

Abstract We construct ray-based encircled-flux compliant sources for multi-mode optical fiber launches using classic geometrical optics. In particular, we make an LP-mode conforming launch that excites only guided rays by distributing the β ¯ ray invariant according to a (scaled) counterpart of the modal power distribution of LP-modes. Propagation of the ray distribution is spatially stable and simulations of attenuation due to fiber connections and 1 mm far-field behavior using this source agree well with measurements. We caution against models that configure ray positions and ray directions independently and show that they are prone to produce unstable ray distributions. Lastly, we show that modal noise due to laterally misaligned fibers can be replicated using geometrical optics by configuring our LP-mode conforming sources to match the radial power distribution of 3000 vectorial full-wave spatio-temporal coherent speckle patterns.

3-Dimensional personalized planning for transcatheter pulmonary valve implantation in a dysfunctional right ventricular outflow tract

BackgroundIdentification of adequate landing zone for transcatheter pulmonary valve implantation (TPVI) is crucial to successfully treat an aneurysmatic native right ventricle outflow tract (RVOT); three-dimensional (3D) patient-tailored digital and physical printed models are available but their actual strengths and weaknesses still not well documented. The aim of the study was to tackle TPVI planning in the dysfunctional and borderline RVOT exploiting both digital and physical printed 3D patient-specific models. MethodsElectrocardiographically gated computed tomography (CT) angiography was segmented and anatomical RVOT geometrical changes dynamically tracked throughout the cardiac cycle using in-house processing. A compliant 3D-printed model was manufactured from the diastolic rest phase to test in vitro the catheter-based procedure feasibility; results were compared against CT-derived in vivo measurements and the actual catheterization outcome. ResultsCT-gated analysis successfully quantified in vivo RVOT dynamic changes corroborating the feasibility of non-conventional pulmonary jailing percutaneous intervention. Clinicians used the 3D-printed model to test the steps of the jailing procedure; yet, the deformable 3D model printed at diastole underestimated the final implant dimensions obtained during cardiac catheterization by the same operators. ConclusionsMultidisciplinary synergy between CT-gated analysis and pre-procedural tests on 3D-printed phantoms can help the interventional team to tackle complex TPVI procedures. To fully exploit 3D-printed models, adequate selection of the still frame to print and tuning of printing material properties is crucial and can be aided by 3D dynamic virtual models.

Modeling and Simulation of Bifurcation Dynamics of a Double Spatial Pendulum Excited by a Rotating Obstacle

This work focuses on analyzing the dynamical behavior of a mechanical system consisting of a double spatial pendulum in contact with a movable obstacle. The pendulum’s ability to move in space is achieved by the use of special Cardan–Hook joints as the links of the pendulum. The mechanical system is equipped with a special movable obstacle, i.e. a rotating circular plate situated below the pendulum, which limits the space of admissible positions. A significant part of this work is devoted to the modeling of the contact between the pendulum and the obstacle. In this regard, a special class of reduced models is derived with the resultant friction force and moment acting on the finite size of the contact area along with a compliant model of impact based on the Hertz stiffness. Finally, the effective model suitable for fast and realistic numerical simulations is obtained. The contact model is tested numerically and the effect of its parameters on the system bifurcation dynamics is investigated.

Highly integrated workflows for exploring cardiovascular conditions: Exemplars of precision medicine in Alzheimer's disease and aortic dissection

For precision medicine to be implemented through the lens of in silico technology, it is imperative that biophysical research workflows offer insight into treatments that are specific to a particular illness and to a particular subject. The boundaries of precision medicine can be extended using multiscale, biophysics-centred workflows that consider the fundamental underpinnings of the constituents of cells and tissues and their dynamic environments. Utilising numerical techniques that can capture the broad spectrum of biological flows within complex, deformable and permeable organs and tissues is of paramount importance when considering the core prerequisites of any state-of-the-art precision medicine pipeline. In this work, a succinct breakdown of two precision medicine pipelines developed within two Virtual Physiological Human (VPH) projects are given. The first workflow is targeted on the trajectory of Alzheimer's Disease, and caters for novel hypothesis testing through a multicompartmental poroelastic model which is integrated with a high throughput imaging workflow and subject-specific blood flow variability model. The second workflow gives rise to the patient specific exploration of Aortic Dissections via a multi-scale and compliant model, harnessing imaging, computational fluid-dynamics (CFD) and dynamic boundary conditions. Results relating to the first workflow include some core outputs of the multiporoelastic modelling framework, and the representation of peri-arterial swelling and peri-venous drainage solution fields. The latter solution fields were statistically analysed for a cohort of thirty-five subjects (stratified with respect to disease status, gender and activity level). The second workflow allowed for a better understanding of complex aortic dissection cases utilising both a rigid-wall model informed by minimal and clinically common datasets as well as a moving-wall model informed by rich datasets.

Reduced-order modeling of hemodynamics across macroscopic through mesoscopic circulation scales.

We propose a hemodynamic reduced-order model bridging macroscopic and mesoscopic blood flow circulation scales from arteries to capillaries. In silico tree-like vascular geometries, mathematically described by graphs, are synthetically generated by means of stochastic growth algorithms constrained by statistical morphological and topological principles. Scale-specific pruning gradation of the tree is then proposed in order to fit computational budget requirement. Different compliant structural models with respect to pressure loads are used depending on vessel walls thicknesses and structures, which vary considerably from macroscopic to mesoscopic circulation scales. Nonlinear rheological properties of blood are also included, and microcirculation network responses are computed for different rheologies. Numerical results are in very good agreement with available experimental measurements. The computational model captures the dynamic transition between large- to small-scale flow pulsatility speeds and magnitudes and wall shear stresses, which have wide-ranging physiological influences.

A Three-row Opposed Gripping Mechanism with Bioinspired Spiny Toes for Wall-climbing Robots

This paper presents a study of a three-row opposed gripping mechanism made of bioinspired spiny toes. An insect Serica orientalis Motschulsky’s tarsal system was first described and studied. A compliant single spiny toe model was established assuming that the contact asperities were spheres. Following the single toe contact model, a spiny toe array’s contact model was then developed using asperity height’s distribution function. By studying the engaging and disengaging process of the single toe, the mechanical behavior of the toe and toe array were addressed. The toes as well as the arrays were manufactured via rapid prototyping. A customized apparatus using displacement-control method has been carried out to measure the pull-in forces and pull-off positions of the single toe and toe array under various compression conditions. Based on the understanding, a three-row opposed gripping mechanism with radial configuration for wall-climbing robots was designed and fabricated according to the mechanical behaviors of the toe and array. Using an opposed spoke configuration with 3 rows of 31 toes on each linkage array, the mechanism designed as a foot of climbing robots can vertically resist at least 1 kg of load on rough inverted surface, while the maximum normal load is as high as 31 N. The findings may provide a way in developing a high payload wall-climbing robot system for practical applications.

DEVELOPING FINTECH AND ISLAMIC FINANCE PRODUCTS IN AGRICULTURAL VALUE CHAIN

To meet the global population needs, it is projected to at least eighty billion dollars in investment per year to support the food security until 2050. It is widely known that the agriculture financing growth has stalled due to many reasons. Islamic finance has potential to spur the growth of agriculture financing to promote global food security. Meanwhile, agriculture in Indonesia is still nowhere to its potential. It is hindered by an inefficient and underdeveloped downstream segment, low access to financial and technology. This is a huge opportunity for Islamic finance in helping to bridge the gap through value chain finance approach as one of the strategies to reduce risk and give socio-economic spill-over effect along the chain. Islamic finance can promote agricultures sustainability and a more efficient process with FinTech enabled platform. The multiple case study proposes a sharia compliant community-based financing model in agricultural value chain practice with FinTech enabled platform. The result is this model integrating all actors from different market segmentation (landowners, suppliers, farmers, brokers, retailers, investor) into an Islamic value chain financing platform. However, determining buying intention, partnership establishment, and technology infrastructure are pivotal for its future implementation.

Multibody dynamics simulation of thin-walled four-point contact ball bearing with interactions of balls, ring raceways and crown-type cage

The dynamic characteristics of thin-walled four-point contact ball bearing with crown-type cage are important to the dynamic performance and motion accuracy of an industrial robot. Considering multi-clearances, dynamic contact and impact relationships of the ball, ring raceway and crown-type cage, a general methodology for dynamic simulation analysis of the bearing is investigated in the proposed work. In accordance with the geometry of torus, the geometric equation of accurate ring raceway is derived and integrated into the three-dimensional ring raceway using user’s subroutines. The parameterized and assembled three-dimensional model of the bearing is established using ADAMS’s macro-programs. Applying a penalty formulation and a unilateral nonlinear spring–damper model to the bearing, the internal contact interaction is represented as the compliant contact force model using IMPACT function. The multibody contact dynamic models of the bearing are solved by HHT algorithm with ADAMS/Solver. The dynamic results of the contact force, impact force and motion stability of the bearing are discussed under the condition of different loads. The static load distribution and cage’s angular velocity of simulation model are verified by the theoretical values. The motion trajectory of outer ring’s center is circular with a whirling motion. The sphere-to-partial torus surface contacts (ball–racetrack contact) are always four contact points in the load zone of the bearing. Applying pure radial load or rotating radial load, the impact force of ball-to-cage small pocket contact is much larger than that of radial and axial load combination in the non-load zone of the bearing. As a result of the large impact force of ball-to-cage small pocket contact, the angular velocities of the ball and cage are varying greatly in the non-load zone. The impact force of ball-to-cage big pocket contact is very small. The angular velocity of the ball is always that of pure rolling in the load zone and varying slightly in the non-load zone. The new method can be applied to investigate dynamic analysis and design of high-precision industrial robots with multi-clearances, multi-ball bearings under complex, time-varying working conditions.

Bayesian Tactile Exploration for Compliant Docking With Uncertain Shapes

This paper presents a Bayesian approach for active tactile exploration of a planar shape in the presence of both localization and shape uncertainty. The goal is to dock the robot's end-effector against the shape-reaching a point of contact that resists a desired load-with as few probing actions as possible. The proposed method repeatedly performs inference, planning, and execution steps. Given a prior probability distribution over object shape and sensor readings from previously executed motions, the posterior distribution is inferred using a novel and efficient Hamiltonian Monte Carlo method. The optimal docking site is chosen to maximize docking probability, using a closed-form probabilistic simulation that accepts rigid and compliant motion models under Coulomb friction. Numerical experiments demonstrate that this method requires fewer exploration actions to dock than heuristics and information-gain strategies.

STEP-NC compliant data model for freeform surface manufacturing based on T-spline

ABSTRACTSTEP-NC is a new interface standard between CAD/CAM and CNC. Most of the studies focus on the 2.5D features machining using STEP-NC. However, freeform surface is widely used in the field of aerospace, automotive and dies/moulds. Beyond that, due to the drawbacks of NURBS that is the only representation for freeform surface in STEP, the research of STEP-NC for freeform surface is rare. In the paper, STEP-NC compliant data model is proposed for freeform surface manufacturing based on T-spline. We contribute three advantages: (1) a modified STEP data model is constructed that can represent and exchange arbitrary T-spline surface for STEP-NC-based manufacturing, (2) a general framework is proposed for evaluation of arbitrary T-spline surface that can be used for STEP-NC-based freeform surface evaluation, (3) a concept of Manufacturing-Suitable Region is proposed, which can divide T-spline surface into a set of regions for STEP-NC-based manufacturing. Some testing models show that the modified STEP data model is more efficient than the NURBS-based STEP data model for storage, and the feasibility to process arbitrary T-spline surface is verified using the general framework. In addition to this, a case study is researched to demonstrate the advantage of Manufacturing-Suitable Region for STEP-NC-based freeform surface manufacturing.

An in silico study of the influence of vessel wall deformation on neointimal hyperplasia progression in peripheral bypass grafts

Neointimal hyperplasia (NIH) is a major obstacle to graft patency in the peripheral arteries. A complex interaction of biomechanical factors contribute to NIH development and progression, and although haemodynamic markers such as wall shear stress have been linked to the disease, these have so far been insufficient to fully capture its behaviour. Using a computational model linking computational fluid dynamics (CFD) simulations of blood flow with a biochemical model representing NIH growth mechanisms, we analyse the effect of compliance mismatch, due to the presence of surgical stitches and/or to the change in distensibility between artery and vein graft, on the haemodynamics in the lumen and, subsequently, on NIH progression. The model enabled to simulate NIH at proximal and distal anastomoses of three patient-specific end-to-side saphenous vein grafts under two compliance-mismatch configurations, and a rigid wall case for comparison, obtaining values of stenosis similar to those observed in the computed tomography (CT) scans. The maximum difference in time-averaged wall shear stress between the rigid and compliant models was 3.4 Pa, and differences in estimation of NIH progression were only observed in one patient. The impact of compliance on the haemodynamic-driven development of NIH was small in the patient-specific cases considered.

Viscoelastic Snapping Metamaterials

Abstract Mechanical metamaterials are artificial composites with tunable advanced mechanical properties. Particularly, interesting types of mechanical metamaterials are flexible metamaterials, which harness internal rotations and instabilities to exhibit programable deformations. However, to date, such materials have mostly been considered using nearly purely elastic constituents such as neo-Hookean rubbers. Here, we experimentally explore the mechanical snap-through response of metamaterials that are made of constituents that exhibit large viscoelastic relaxation effects, encountered in the vast majority of rubbers, in particular, in 3D printed rubbers. We show that they exhibit a very strong sensitivity to the loading rate. In particular, the mechanical instability is strongly affected beyond a certain loading rate. We rationalize our findings with a compliant mechanism model augmented with viscoelastic interactions, which qualitatively captures well the reported behavior, suggesting that the sensitivity to the loading rate stems from the nonlinear and inhomogeneous deformation rate, provoked by internal rotations. Our findings bring a novel understanding of metamaterials in the dynamical regime and open up avenues for the use of metamaterials for dynamical shape-changing as well as vibration and impact damping applications.

Simulation of blood flow past a distal arteriovenous-graft anastomosis at low Reynolds numbers

Patients with end-stage renal disease are usually treated by hemodialysis while waiting for a kidney transplant. A common device for vascular access is an arteriovenous graft (AVG). However, AVG failure induced by thrombosis has been plaguing dialysis practice for decades. Current studies indicate that the thrombosis is caused by intimal hyperplasia, which is triggered by the abnormal flows and forces [e.g., wall shear stress (WSS)] in the vein after AVG implant. Due to the high level of complexity, in almost all of the existing works of modeling and simulation of the blood-flow vessel-AVG system, the graft and blood vessel are assumed to be rigid and immobile. Very recently, we have found that the compliance of graft and vein can reduce flow disturbances and lower WSS [Z. Bai and L. Zhu, “Three-dimensional simulation of a viscous flow past a compliant model of arteriovenous-graft anastomosis,” Comput. Fluids 181, 403–415 (2019)]. In this paper, we apply the compliant model to investigate possible effects of several dimensionless parameters (AVG graft-vein diameter ratio Rgv, AVG attaching angle θ, flow Reynolds numbers Re, and native vein speed Vv) on the flow and force fields near the distal AVG anastomosis at low Reynolds numbers (up to several hundreds). Our computational results indicate that the influences of the parameters Rgv, θ, and Re lie largely on the graft and the influence of Vv lies largely on the vein. In any case, the WSS, wall shear stress gradient, and wall normal stress gradient and their averaged values on the graft are significantly greater than those on the vein.

An in vitro model to explore subchondral perfusion and intraosseous pressure

BackgroundLittle is known about subchondral perfusion physiology. We developed a 3Rs (Replace, Reduce, Refine) compliant in vitro calf foot model to explore perfusion and intraosseous pressure (IOP).MethodsCalf feet were catheterised and perfused with serum. IOP was measured at three sites, the metacarpal diaphysis (MCD), metacarpal subchondral epiphysis (MCS) and proximal phalanx diaphysis (PPD) using intraosseous needles with pressure transducers and digital recorders. Fresh (< 4 h post mortem) and old feet (> 4 h post mortem) were perfused at different pressures, with and without a proximal tourniquet.ResultsThere was a wide range in basal IOP with a mean IOP of 30.0 mmHg, SD 14.4, range 7.6 mmHg to 52.7 mmHg (n = 40 records) in 15 subjects. There was no significant difference between the three sites tested (p = 0.54, 0.12 and 0.051). At each individual site IOP correlated with perfusion pressure (r = 0.993). With a proximal venous tourniquet, IOP increased from 15.1 mmHg (SD 11.3 mmHg) to 44.9 mmHg (SD 24 mmHg), p < 0.0001, n = 9. Filling and emptying curves during perfusion and with using a tourniquet were similar, indicating that the model behaves in an elastic hydrodynamic manner. In fresh feet IOP peaked after about 1 min irrespective of perfusion pressure, possibly due to auto regulation. Older feet showed a continuously rising IOP and became oedematous. There was no significant difference in IOP between fresh and old feet perfused with serum at 150 cms pressure for 1 min.ConclusionThough basal intraosseous pressure varies, IOP behaves predictably. IOP measurements reflect the perfusion microclimate at the individual needle tip. This 3Rs compliant model will be used for further exploration of subchondral perfusion physiology with loading.

Variation Simulation and Diagnosis Model of Compliant Block Assembly Considering Welding Deformation

This article proposes a variation simulation and diagnosis model for ship block assembly processes considering the effects of welding distortion. The welding process and the deformation pattern affecting the final shape of a block assembly are diagnosed. Prior studies on welding distortion mainly focused on mitigation methodologies. In this research, welding distortion is regarded as the main cause of geometric variation in parts. In addition, how geometric variations are accumulated throughout multiple assembly processes is mathematically modeled. The variation simulation model is based on a state space equation, where variations of previous stages are propagated to the current stage. The diagnosis model predicts the quantitative effect of each variation source on the final assembly's geometrical variation, based on a normal equation and designated component analysis. The proposed model is simulated with FEM (Dassault Systèmes Americas Corp., Waltham, MA) and MATLAB (Mathworks (https://www.mathworks.com/), Massachusetts, United States) replicating a realistic block assembly process for validation. The model can effectively simulate the propagation of welding distortion and quantitatively diagnose variation patterns and welding processes. 1. Introduction Analysis, management, and variation diagnostics are some of the important aspects of the production process. These have been mainly studied in mass production processes such as in the automobile industry. Mantripragada and Whitney (1999) and Whitney (2004) proposed a tolerance analysis method for the multistage rigid body assembly using a state space equation. Huang et al. (2006a, 2007) proposed a ship block tolerance model for the single and multiple stage variation propagation of a rigid body model. Liu and Hu (1995,1997) proposed a compliant assembly model using FEM, called the method of influence coefficients (MIC). Govik et al. (2012) proved MIC using an FEM simulation. Variation propagation in a multiple stage process while considering a compliant assembly has been proposed by Camelio et al. (2003, 2002a). Variation propagation models considering the location of data such as in key control characteristics, key product characteristics, and a local coordinate system of parts were proposed by Qu et al. (2016).

Performance analysis of the transcatheter aortic valve implantation on blood flow hemodynamics: An optical imaging-based in vitro study.

Cardiac implants may have a strong influence on the hemodynamics of the circulatory system. In this study, we aimed at investigating the impact of transcatheter aortic valve implantation (TAVI) devices on blood flow patterns that develop in the ascending aorta under physiological flow conditions in vitro. For this purpose, a noninvasive optical measurement tool, three-dimensional particle tracking velocimetry (3D-PTV), was used in a realistic compliant silicone aortic model. The performance and the influence of two TAVIs and one surgical valve on the aortic flow were investigated. Our results showed that valve design and materials may have a distinct influence on relevant hemodynamic properties, namely kinetic energy, production of turbulence, and shear stresses in the ascending aorta. All properties varied considerably between the different valve models. We found that the total aortic regurgitation composed of the closing volume, transvalvular and paravalvular leakages varied for the three valves investigated. Furthermore, peak mean kinetic energy (MKE) ranged from 61 to 116 J/m3 , whereas peak turbulent kinetic energy (TKE) ranged from 23 to 36 J/m3 . The analysis of shear showed that all the three studied devices had minimal overall risk for thrombus formation. We conclude that the characteristics and material designs of TAVI devices have strong influences on the hemodynamics in the ascending aorta.

CDK inhibitors reduce cell proliferation and reverse hypoxia-induced metastasis of neuroblastoma tumours in a chick embryo model

Neuroblastoma is a paediatric cancer with a poor prognosis. This is in part due to widespread metastasis at time of presentation, which is refractory to current treatment modalities. New therapeutic agents that can control not only tumour growth but also metastasis are urgently needed. The differentiation therapy, retinoic acid, is currently used in clinic, leading to terminal differentiation of neuroblastoma cells thus reducing tumour growth in the primary tumour as well as at metastatic sites. However, retinoic acid only works in a subset of patients. We investigated the potential of CDK inhibitors, Palbociclib and RO-3306, on neuroblastoma cell differentiation, tumour progression and metastasis by utilising a 3R compliant cost effective preclinical chick embryo model. In both SK-N-AS and BE(2)C cell lines, when engrafted on the chorioallantoic membrane of chick embryos, we observed a reduction of tumour cell proliferation as well as a reduction in hypoxia preconditioning-driven metastasis by 60%. In addition, the expression of a panel of genes with known roles in metastasis, which increased upon hypoxia-preconditioning, was largely reduced by a CDK1 inhibitor. These results provide a promising alternative to currently existing therapies and might aid the development of new treatment protocols for retinoic acid-resistant patients.