Pantograph/catenary contact force control

In this paper, a new continuum-based pantograph/catenary model based on the absolute nodal coordinate formulation (ANCF) is proposed and used to develop an effective method to control the contact force which arises from the pantograph/catenary interaction. In the proposed new model, only one ANCF gradient vector is used in the formulation of the pantograph/catenary contact conditions, thereby allowing for using the proposed approach for both fully parameterized and gradient deficient ANCF finite elements. A three-dimensional multibody system (MBS) model of a pantograph mounted on a train is developed using a nonlinear augmented MBS formulation. In order to take into account the catenary large deformation, ANCF finite elements are used. The contact between the pantograph and the catenary system is ensured using a sliding joint constraint whereas the contact between the rail vehicle wheels and the train track is modelled using an elastic contact formulation. In addition to the use of the new MBS approach to model the pantograph/catenary interaction, the contact force between the pantograph and the catenary is computed using a simpler lumped parameter model which describes the pan-head and the plunger subsystem dynamics. In order to reduce the standard deviation of the contact force without affecting its mean value, a control actuator is used between the pan-head and the plunger. To this end, three types of control laws for the control action are designed to improve the contact quality both in the transient phase and in the steady state phase of the pantograph/catenary interaction. The first control law proposed features a feedback structure whereas the second and the third control strategies employ a feedback plus feed-forward architecture. In order to demonstrate the effectiveness of the proposed method, the results of a set of numerical simulations with and without the controllers are presented

Contact force control In multibody pantograph/catenary systems

In this paper, a new continuum-based pantograph/catenary model based on the absolute nodal coordinate formulation (ANCF) is proposed and used to develop an effective method to control the contact force which arises from the pantograph/catenary interaction. In the proposed new model, only one ANCF gradient vector is used in the formulation of the pantograph/catenary contact conditions, thereby allowing for using the proposed approach for both fully parameterized and gradient-deficient ANCF finite elements. The proposed contact formulation can also be considered as a more general sliding joint formulation that allows for the use of the more efficient gradient-deficient ANCF finite elements in modeling very flexible cables. A three-dimensional multibody system (MBS) model of a pantograph mounted on a train is developed using a nonlinear augmented MBS formulation. In order to take into account the catenary large deformation, ANCF finite elements are used. The contact between the pantograph and the catenary system is ensured using a sliding joint constraint whereas the contact between the rail vehicle wheels and the train track is modelled using an elastic contact formulation. In addition to the use of the new MBS approach to model the pantograph/catenary interaction, the contact force between the pantograph and the catenary is computed using a simpler lumped parameter model which describes the pan-head and the plunger subsystem dynamics. In order to reduce the standard deviation of the contact force without affecting its mean value, a control actuator is used between the pan-head and the plunger. To this end, three types of control laws for the control action are designed to improve the contact quality both in the transient phase and in the steady state phase of the pantograph/catenary interaction. The first control law proposed features a feedback structure whereas the second and the third control strategies employ a feedback plus feed-forward architecture. In order to demonstrate the effectiveness of the proposed method, the results of a set of numerical simulations with and without the controllers are presented

Integration of Geometry and Small and Large Deformation Analysis for Vehicle Modelling: Chassis, and Airless and Pneumatic Tyre Flexibility

The goal of this study is to propose an approach for developing new and detailed vehicle models that include flexible components with complex geometries, including chassis, and airless and pneumatic tires with distributed inertia and elasticity. The methodology used is based on integration of geometry, and small and large deformation analysis using a mechanics-based approach. The floating frame of reference (FFR) formulation is used to model the small deformations, whereas the absolute nodal coordinate formulation (ANCF) is used for the large deformation analysis. Both formulations are designed to correctly capture complex geometries including structural discontinuities. To this end, a new ANCF-preprocessing approach based on linear constraints that allows for systematically eliminating dependent variables and reducing the component model dimension is proposed. One of the main contributions of this paper is the development of the first ANCF airless tire model which is integrated in a three-dimensional multibody system (MBS) algorithm designed for solving the differential/algebraic equations of detailed vehicle models. On the other hand, relatively stiff components with complex geometries, such as the vehicle chassis, are modelled using the finite element (FE) FFR formulation which creates a local linear problem that can be exploited to eliminate high frequency and insignificant deformation modes. Numerical examples that include a simple ANCF pendulum with structural discontinuities and a detailed off-road vehicle model consisting of flexible tires and chassis are presented. Three different tire types are considered in this study; a brush-type tire, a pneumatic FE/ANCF tire, and an airless FE/ANCF tire. The numerical results are obtained using the general purpose MBS computer program Systematic Integration of Geometric Modelling and Analysis for the Simulation of Articulated Mechanical Systems (SIGMA/SAMS)

Integration of geometry and small and large deformation analysis for vehicle modelling: Chassis, and airless and pneumatic tyre flexibility.

The goal of this study is to propose an approach for developing new and detailed vehicle models that include flexible components with complex geometries, including chassis, and airless and pneumatic tyres with distributed inertia and elasticity. The methodology used is based on integration of geometry, and small and large deformation analysis using a mechanics-based approach. The floating frame of reference (FFR) formulation is used to model the small deformations, whereas the absolute nodal coordinate formulation (ANCF) is used for the large deformation analysis. Both formulations are designed to correctly capture complex geometries including structural discontinuities. To this end, a new ANCF-preprocessing approach based on linear constraints that allows for systematically eliminating dependent variables and reducing the component model dimension is proposed. One of the main contributions of this paper is the development of the first ANCF airless tyre model which is integrated in a three-dimensional multibody system (MBS) algorithm designed for solving the differential/algebraic equations of detailed vehicle models. On the other hand, relatively stiff components with complex geometries, such as the vehicle chassis, are modelled using the finite element (FE) FFR formulation which creates a local linear problem that can be exploited to eliminate high frequency and insignificant deformation modes. Numerical examples that include a simple ANCF pendulum with structural discontinuities and a detailed off-road vehicle model consisting of flexible tyres and chassis are presented. Three different tyre types are considered in this study; a brush-type tyre, a pneumatic FE/ANCF tyre, and an airless FE/ANCF tyre. The numerical results are obtained using the general purpose MBS computer program Systematic Integration of Geometric Modelling and Analysis for the Simulation of Articulated Mechanical Systems (SIGMA/SAMS)

Comparison of endothelial shear stress between ultrathin strut Bioresorbable Polymer Drug Eluting Stent vs Durable Polymer Drug Eluting Stent post-stent implantation: An optical coherence tomography substudy from BIOFLOW II.

BACKGROUND Recent clinical data indicate a different performance of biodegradable polymer (BP)-drug eluting stent (DES) compared to durable polymer (DP)-DES. Whether this can be explained by a beneficial impact of BP-DES stent design on the local hemodynamic forces distribution remains unclear. OBJECTIVES To compare endothelial shear stress (ESS) distribution after implantation of ultrathin (us) BP-DES and DP-DES and examine the association between ESS and neointimal thickness (NIT) distribution in the two devices at 9 months follow up. METHODS AND RESULTS We retrospectively identified patients from the BIOFLOW II trial that had undergone OCT imaging. OCT data were utilized to reconstruct the surface of the stented segment at baseline and 9 months follow-up, simulate blood flow, and measure ESS and NIT in the stented segment. The patients were divided into 3 groups depending on whether DP-DES (N = 8, n = 56,160 sectors), BP-DES with a stent diameter of >3 mm (strut thickness of 80 μm, N = 6, n = 36,504 sectors), or BP-DES with a stent diameter of ≤3 mm (strut thickness of 60 μm, N = 8, n = 50,040 sectors) were used for treatment. The ESS, and NIT distribution and the association of these two variables were estimated and compared among the 3 groups. RESULTS In the DP-DES group mean NIT was 0.18 ± 0.17 mm and ESS 1.68 ± 1.66 Pa; for the BP-DES ≤3 mm group the NIT was 0.17 ± 0.11 mm and ESS 1.49 ± 1.24 Pa and for the BP-DES >3 mm group 0.20 ± 0.23 mm and 1.42 ± 1.24 Pa respectively (p < 0.001 for both NIT and ESS comparisons across groups). A negative correlation between NIT and baseline ESS was found, the correlation coefficient for all the stented segments was -0.33, p < 0.001. CONCLUSION In this OCT sub-study of the BIOFLOW II trial, the NIT was statistically different between groups of patients treated with BP-DES and DP-DES. In addition, regions of low ESS were associated with increased NIT in all studied devices

Words into Action: Nature-based solutions for disaster risk reduction

No abstract available