Multibody Dynamics Approach Research Articles

Feasibility in assessing the dipped rail joint defects through dynamic response of heavy haul locomotive

The feasibility of monitoring the dipped rail joint defects has been theoretically investigated by simulating a locomotive-mounted acceleration system negotiating several types of dipped rail defects. Initially, a comprehensive locomotive-track model was developed using the multi-body dynamics approach. In this model, the locomotive car-body, bogie frames, wheelsets and driving motors are considered as rigid bodies; track modelling was also taken into account. A quantitative relationship between the characteristics (peak–peak values) of the axle box accelerations and the rail defects was determined through simulations. Therefore, the proposed approach, which combines defect analysis and comparisons with theoretical results, will enhance the ability for long-term monitoring and assessment of track systems and provides more informed preventative track maintenance strategies.

Performance Analysis of a Self-Propelling Flat Plate Fin with Joint Compliance

Fish fin muscles are compliant and they regulate the stiffness to suit different swimming conditions. This article attempts to understand the significance of presence of compliance in fin muscle with help of a flexible joint flat plate fin model. Blade element method is employed to model hydrodynamics and to compute the forces of interaction during motion of the plate within fluid. The dynamic model of self-propelling fin is developed through multi-body dynamics approach considering the hydrodynamic forces as external forces acting on the fin. The derived hydrodynamic model is validated with experiments on rigid flat plate fin. The effect of the joint stiffness and flapping frequency on the propulsion speed and efficiency is investigated through simulations using the derived and validated model. The propulsion efficiency is found to be highly influenced by the joint stiffness at a given flapping frequency. The fin attained maximum propulsion efficiency when the joint stiffness is tuned to a value at which flapping frequency matches near natural frequency of the fin. At this tuned joint stiffness and flapping frequency, the resulted Strouhal numbers are observed to fall within the optimum range (0.2 to 0.4) for maximized propulsion efficiency of flying birds and swimming aquatic animals reported in literature.

Integration of car-body flexibility into train–track coupling system dynamics analysis

ABSTRACTThe resonance vibration of flexible car-bodies greatly affects the dynamics performances of high-speed trains. In this paper, we report a three-dimensional train–track model to capture the flexible vibration features of high-speed train carriages based on the flexible multi-body dynamics approach. The flexible car-body is modelled using both the finite element method (FEM) and the multi-body dynamics (MBD) approach, in which the rigid motions are obtained by using the MBD theory and the structure deformation is calculated by the FEM and the modal superposition method. The proposed model is applied to investigate the influence of the flexible vibration of car-bodies on the dynamics performances of train–track systems. The dynamics performances of a high-speed train running on a slab track, including the car-body vibration behaviour, the ride comfort, and the running safety, calculated by the numerical models with rigid and flexible car-bodies are compared in detail. The results show that the car-body flexibility not only significantly affects the vibration behaviour and ride comfort of rail carriages, but also can has an important influence on the running safety of trains. The rigid car-body model underestimates the vibration level and ride comfort of rail vehicles, and ignoring carriage torsional flexibility in the curving safety evaluation of trains is conservative.

Physics-Based Deformable Tire–Soil Interaction Model for Off-Road Mobility Simulation and Experimental Validation

A physics-based deformable tire–soil interaction simulation capability that can be fully integrated into the monolithic multibody dynamics computer algorithm is developed by extending a deformable tire model based on the flexible multibody dynamics approach to off-road mobility simulations with a moving soil patch technique and it is validated against test data. A locking-free nine-node brick element is developed for modeling large plastic soil deformation using the multiplicative finite strain plasticity theory along with the capped Drucker–Prager failure criterion. To identify soil parameters including cohesion and friction angle, the triaxial compression test is carried out, and the soil model developed is validated against the test data. In addition to the component level validation for the tire and soil models, the tire–soil interaction simulation capability developed in this study is validated against the soil bin mobility test results. The tire forces and rolling resistance coefficients predicted by the simulation model agree well with the test results. It is shown that effect of the wheel loads and tire inflation pressures is well captured in the simulation model. Furthermore, it is demonstrated that the moving soil patch technique, with which soil behavior only in the vicinity of the rolling tire is solved to reduce the soil model dimensionality, leads to a significant reduction in computational time, thereby enabling use of the high-fidelity physics-based tire–soil interaction model in the large-scale off-road mobility simulation.

Intervertebral efforts quantification using a multibody dynamics approach: application to scoliosis

Spine surgery planning involves many decisions for which the surgeon has not enough information, and for which biomechanical models might be helpful This has been illustrated by a study carried out...

Shape Optimization of Low Speed Wind Turbine Blades using Flexible Multibody Approach

It is proposed that the small-size wind turbines can demonstrate the innovative solution for the wind energy conversion for low speed regions. An innovative design, control, and monitoring processes require accurate and validated dynamic model of such turbines. In this investigation, the flexible multibody dynamics approach is used to extend the traditional method of dynamic modeling of small-size wind turbines. A systematic approach is developed based on Floating Frame of Reference formulation (FFR) that includes the dynamics of the flexible blades as well as the aerodynamic loads. A trade-offs procedure to optimize the airfoil geometric shape is introduced of small-size wind turbines for performance and energy conversion. The conclusion figure out the correct size as well as the most optimal airfoil shapes for small-size wind turbines suitable for low wind speed conditions.

Online trajectory generation for wide ditch crossing of biped robots using control constraints

This work proposes a multibody dynamics approach to generate joint trajectories for a five degrees of freedom biped robot crossing a wide ditch whose width is greater than or equal to the robot’s leg length. Trajectories are generated using control constraints that depend on the horizontal distance traveled by the center of mass and are not explicitly dependent on time. Behavior of the biped robot for various initial postures is studied considering dynamic balance, friction, and impact in order to find the preferred initial postures considering the net energy consumption and peak power requirements at various joints. Several cases of friction, zero moment point location, and the center of mass height variation are considered in the study. Using the proposed approach, feasible trajectories for an adult sized biped robot could be generated for a wide ditch of 1.05 m width at coefficients of friction as low as 0.2. The results obtained are useful for designing reference trajectories and actuation systems for biped robots that need to cross wide ditches or take large steps. Time needed for trajectory generation is found to be sufficiently low for online implementation.

Dynamical Analysis of a Cable Manipulator Using Multibody Approaches

This paper deals with the creation of a computational model of a particular cable manipulator composed of a rigid manipulator with three degrees of freedom and a platform driven by four fibers. Each fiber is led over a pulley and is driven by a linear motor, which can be controlled. The multibody dynamics approach is a suitable way in order to create the manipulator model. The most common cable modelling techniques are summarized in this paper and then the computational model of the cable manipulator QuadroSphere is created using MSC.Adams software. The computational model verification is done using the modal analysis of linearized model and the experimental modal analysis on the real set up. Further results of various numerical simulations are presented and their utilization is discussed.

Rail Passenger Vehicle Crashworthiness Simulations Using Multibody Dynamics Approaches

Multibody dynamics approaches have nowadays been an essential part in examining train crashworthiness. A typical passenger train structure has been investigated on its crashworthiness using three-dimensional (3D) models of a single passenger car and multiple cars formulated using multibody dynamics approaches. The simulation results indicate that the crush length or crush force or both of the crush mechanisms in the high and low energy (HE and LE) crush zones of a passenger train have to be increased for the higher crash speeds. The results on multiple cars (up to ten cars) show that the design of HE and LE crush zones is significantly influenced by the number of cars. The energy absorbed by the HE zone is reasonably consistent for train models with more than four cars at the crash speed of 35 km/h. The comparison of simulations can identify the contribution of the number of cars to the head-on crash forces. The influence of train mass on the design of both HE and LE crush zones, and the influence of design of the crush zones on the wheel-rail contacts are examined.

Assessment of Linearization Approaches for Multibody Dynamics Formulations

Formulating the dynamics equations of a mechanical system following a multibody dynamics approach often leads to a set of highly nonlinear differential-algebraic equations (DAEs). While this form of the equations of motion is suitable for a wide range of practical applications, in some cases it is necessary to have access to the linearized system dynamics. This is the case when stability and modal analyses are to be carried out; the definition of plant and system models for certain control algorithms and state estimators also requires a linear expression of the dynamics. A number of methods for the linearization of multibody dynamics can be found in the literature. They differ in both the approach that they follow to handle the equations of motion and the way in which they deliver their results, which in turn are determined by the selection of the generalized coordinates used to describe the mechanical system. This selection is closely related to the way in which the kinematic constraints of the system are treated. Three major approaches can be distinguished and used to categorize most of the linearization methods published so far. In this work, we demonstrate the properties of each approach in the linearization of systems in static equilibrium, illustrating them with the study of two representative examples.

Development of a telescopic boom lift for nursing care: design and optimization using a multibody dynamics approach

Recently, several types of nursing care equipment to aid the lifting and transfer of aged persons have been developed. Especially, rotational boom-type care lifts are used widely because of their simplicity and usefulness. However, such lifts sometimes provide a feeling of uneasiness because during lift-up, the center of the human body moves backward relative to the position of the heel. Hence, in this paper, we first propose a telescopic boom-type care lift to approximate the trajectory of the lift-up motion of a human standing up naturally. By using a multibody dynamics approach, we show that the proposed mechanism can achieve nearly natural standing-up motion and requires a smaller force for lift-up than that required by the conventional-type lift. Next, we develop a prototype telescopic boom-type care lift and verify experimentally that the proposed lift can reduce mental and physical burden compared with the conventional lift. To compare mental burden, we conduct a sensory evaluation by administering a questionnaire. To compare physical burden, we estimate muscle activation based on users' electromyographic signals. These results show the effectiveness of the proposed telescopic boom-type lift. Finally, we consider the optimal design of the proposed care lift structure. We propose an algorithm to seek optimal design parameters that minimize the error between the tip trajectory of the lift and the human chest trajectory measured using a motion capture system.

マルチボディダイナミクスによるテレスコピックブーム型介護リフトの最適設計

マルチボディダイナミクスによるテレスコピックブーム型介護リフトの最適設計

Optimization and Verification of a Telescopic Boom Lift for Nursing Care Using a Multibody Dynamics Approach

Optimization and Verification of a Telescopic Boom Lift for Nursing Care Using a Multibody Dynamics Approach

Coupled computational fluid dynamics/multibody dynamics method for wind turbine aero-servo-elastic simulation including drivetrain dynamics

A high-fidelity simulation framework is presented to investigate wind turbine aero-servo-elastic behavior, coupling dynamic overset computational fluid dynamics (CFD) and multibody dynamics (MBD) approaches. The Gearbox Reliability Collaborative (GRC) project gearbox was up-scaled in size and installed in the NREL 5-MW offshore wind turbine to demonstrate drivetrain dynamics. Generator torque and blade pitch controllers were implemented to simulate operational conditions of commercial wind turbines. Interactions between wind turbulence, rotor aerodynamics, elastic blades, drivetrain dynamics at the gear-level and servo-control dynamics were studied. Results show that gear contact causes dynamic transmission error within the drivetrain, and results in a decreased turbine thrust and rotational speed. The generator torque controller optimizes efficiency below rated wind speed, while the blade pitch controller properly regulates the turbine near rated power and generator speed at higher than rated wind speed under both uniform and turbulent winds. The pitch controller effectively reduces turbine thrust, blade tip deflections, and velocity deficit of the wake, benefiting both stand-alone turbines and wind farms. The tool and methodology developed show promise to study complex aerodynamic/mechanic systems, being the first time a complete wind turbine simulation includes CFD of the rotor/tower aerodynamics, wind turbulence, elastic blades, gearbox dynamics and feedback control.

내부 유체 슬로싱 효과를 고려한 부유이송 해상풍력 기초의 동적 안정성 해석

부유 이송식 해상풍력 기초를 목표 지점에 설치하기 위해서는 내부의 중공부에 해수를 주입하여 착저 시키게 되는데, 그 과정에서 중량 및 무게 중심과 부력중심이 변하게 되어 부유식 기초가 불안정해 질 수 있다. 부유 이송식 기초의 동적안정성 해석은 기초 외부의 수력학적 하중과 6-자유도 운동을 하게 되는 기초에 작용하는 파도와 조류 하중 및 설치 과정에서 기초 내부의 중공부로 투입되는 해수의 무게중심 이동까지 동시에 고려해야 하는 복잡한 문제이다. 따라서 본 연구에서는 3차원 비정상 CFD 기법과 다물체 동역학 기법을 연성 (coupling)한 정밀 해석기법을 적용하여 부유 이송식 기초 내부 물의 슬로싱 운동까지 고려한 동적안정성 해석을 수행하고 특성을 분석하였다. In order to install the floating transport type wind-turbine foundation, water pumping is used to sink the foundation. During this process, its mass and center of gravity, and buoyancy center become continuously changed so that the dynamic stability of the floating foundation become unstable. Dynamic stability analysis of the floating foundation is a complex problem since it should take into account not only the environmental wave, wind, and current loads but also its weight change effect simultaneously considering six-degree-of-freedom motion. In this study, advanced numerical method based on the coupled computational fluid dynamics (CFD) and multi-body dynamics (MBD) approach has been applied to the dynamic stability analysis of the floating foundation. The sloshing effect of foundation internal water is also considered and the floating dynamic characteristics are numerically investigated in detail.

How does implant distribution affect 3D correction and bone-screw forces in thoracic adolescent idiopathic scoliosis spinal instrumentation?

BackgroundOptimal implant densities and configurations for thoracic spine instrumentation to treat adolescent idiopathic scoliosis remain unknown. The objective was to computationally assess the biomechanical effects of implant distribution on 3D curve correction and bone-implant forces. Methods3D patient-specific biomechanical spine models based on a multibody dynamic approach were created for 9 Lenke 1 patients who underwent posterior instrumentation (main thoracic Cobb: 43°–70°). For each case, a factorial design of experiments was used to generate 128 virtual implant configurations representative of existing implant patterns used in clinical practice. All instances except implant configuration were the same for each surgical scenario simulation. FindingsSimulation of the 128 implant configurations scenarios (mean implant density=1.32, range: 0.73–2) revealed differences of 2° to 10° in Cobb angle correction, 2° to 7° in thoracic kyphosis and 2° to 7° in apical vertebral rotation. The use of more implants, at the concave side only, was associated with higher Cobb angle correction (r=−0.41 to −0.90). Increased implant density was associated with higher apical vertebral rotation correction for seven cases (r=−0.20 to −0.48). It was also associated with higher bone-screw forces (r=0.22 to 0.64), with an average difference between the least and most constrained instrumentation constructs of 107N per implant at the end of simulated instrumentation. InterpretationLow-density constructs, with implants mainly placed on the concave side, resulted in similar simulated curve correction as the higher-density patterns. Increasing the number of implants allows for only limited improvement of 3D correction and overconstrains the instrumentation construct, resulting in increased forces on the implants.

Numerical simulation of active track tensioning system for autonomous hybrid vehicle

One of the most important components of a high speed tracked vehicle is an efficient suspension system. The vehicle should be able to operate both in rough terrain for performance of engineering tasks as well as on the road with high speed. This is especially important for an autonomous platform that operates either with or without human supervision, so that the vibration level can rise compared to a manned vehicle. In this case critical electronic and electric parts must be protected to ensure the reliability of the vehicle.The paper presents a dynamic parameters determination methodology of suspension system for an autonomous high speed tracked platform with total weight of about 5 tonnes and hybrid propulsion system. Common among tracked vehicles suspension solutions and cost-efficient, the torsion-bar system was chosen. One of the most important issues was determining optimal track tensioning - in this case an active hydraulic system was applied. The selection of system parameters was performed with using numerical model based on multi-body dynamic approach. The results of numerical analysis were used to define parameters of active tensioning control system setup. LMS Virtual.Lab Motion was used for multi-body dynamics numerical calculation and Matlab/SIMULINK for control system simulation.

Investigation of bearing clearance effects in dynamics of turbochargers

Turbochargers are modern and very interesting dynamical systems used in various engines in order to increase their power. They are operated at hundreds of thousands revolutions per minute and tend to be fatigue and stability prone. For this reason, a turbocharger rotor has to be designed carefully with respect to its dynamic properties. The following article deals with effects of radial bearing clearances on the dynamical response of the turbocharger rotor. The influence of a bearing clearance on stiffness and damping of a single-film journal bearing is well known and documented. Turbochargers, however, are often supported by floating ring bearings. Such bearings have two bearing clearances—between a journal and a floating ring and between a floating ring and a housing—which are determined by different temperatures of oil films. Turbocharger analysed in the article is modelled by means of flexible multibody dynamics approaches. Bearings’ behaviour is described using Reynolds equation, which is solved numerically. It is shown, but not mathematically proved, how the outer clearance and the ratio between the inner and the outer clearance affect amplitudes of sub-synchronous components in rotor's response.

Dynamic modelling and experimental validation of small-size wind turbine using flexible multibody approach

The wind energy is observed as an essential and powerful energy resource for the socio-economic development. It is proposed that the small-size wind turbines can demonstrate the innovative solution for the wind energy conversion for low speed regions. An innovative design, control, and monitoring processes require accurate and validated dynamic model of such turbines. In this investigation, the flexible multibody dynamics approach is used to extend the traditional method of dynamic modeling of small-size wind turbines. A systematic approach is developed based on floating frame of reference formulation (FFR) that includes the dynamics of the flexible blades as well as the aerodynamic loads. Beam element is used to model the blade structure with variable twist angle. In order to counteract the effect of the geometric stiffening, which comes due to high speed rotations, the coupling terms in the expression of axial strain energy are taken into account. In the other hand, the circulation theory is used to calculate the pressure coefficient difference along the blade, and the generalized aerodynamic forces are established. An experimental test-rig equipped with wind generator is used for the FFR model validation. The equipment gives a maximum discharge flow of 10 (m/s) in a 500 (mm) diameter duct. The dynamic effect of the twist angle of 30 (cm) diameter of rotor blades is studied based on the measured rotor speed of the wind turbine. The comparison of experimental results and numerical solution shows a very good agreement and consequently the wind turbine model obtained is suitable for stress analysis, structural and control design. It is concluded that the FFR formulation is best suited for large rotation and small deformation problems, which coincide with the operational conditions of small-size wind energy systems.

Development and Optimal Design of a Telescopic Boom Lift for Nursing Care Using a Multibody Dynamics Approach

Recently a number of nursing care equipments to aid lift and transfer for aged person have been developed. Especially, rotational boom type care lifts are widely used due to its simplicity and usefulness. However, this type of lifts sometimes provide a feeling of uneasiness since while lift-up human body center moves backward than the position of the heel. Hence, in this paper, we propose a telescopic boom type care lift in order to approximate lift-up motion to a natural human standing-up trajectory. By using a multibody dynamics approach, we show that the proposed mechanism can achieve nearly natural standing-up motion and is able to reduce required force to lift-up than conventional type lift. Then, we develop a prototype telescopic boom type care lift and verify its effectiveness through experiments. Finally, we also consider the optimal design problem of the proposed care lift structure.