Flexible Multibody Dynamics Research Articles

Stress and stability analysis of slewing motion for crawler crane mounted on flexible ground

The ground deformation causes the increasing of crawler crane side loading, even leads to the boom stress failure or crane tipping failure during slewing motion. This paper established a flexible multibody dynamics simulation model considering the coupling effects of the crane mechanical structure flexibility, ground deformation, and load's dynamic pendulum motion. The model has been verified by analytical model based on Winkler foundation and experimental data. Then the simulation model has been further used to analyze the influence of different foundation modulus, slewing speeds, and lifting heights on the crane boom max stress and the tipping stability. The result offers the slewing speed threshold, which can prevent stress and tipping failures for the crawler crane mounted on flexible ground. The research provides reference for the design and safe operation of crawler cranes.

Research on the flexible multibody dynamics of lifting mechanism of neutron spectrometer sample table

First, the lifting mechanism of neutron spectrometer sample table was designed. Then, every single part flexible multibody models and all parts flexible multibody model were built using ANSYS and ADAMS. Finally, the single part flexible multibody models and all parts flexible multibody model were analyzed when lifting mechanism reached the highest position and sliding table was moving along the X- or Y-axis with 1 ton load. The results indicate that the average deformation along Z direction is maximum among all directions of sliding table center, which is 30.1 μm. Outer cylinder takes up the largest proportion of the deformation in X direction, which is 75.8%, middle cylinder takes up the largest proportion of the deformation in Y direction, which is 91.32%, and inner cylinder takes up the largest proportion of the deformation in Z direction, which is 89.36%. Among the eight guide rails of lifting mechanism, four guide rails between the inner and middle cylinders are under uniform load, and the other four guide rails between middle and outer cylinder are under non-uniform load. The findings of the research could guide the optimal design of the neutron spectrometer sample table.

Simulation of heavy-duty engine based on flexible multi-body dynamics

For heavy-duty diesel engine, the structural flexibility of the crankshaft and the engine block has an important influence on the dynamic characteristics of the engine. The deformation and modal resonance generated at work must be considered. Therefore, the multi-body dynamic analysis of the crankshaft and the body structure is based on the flexible body model of the crankshaft and the body. In this paper diesel engine dynamics behaviour is analysed based on flexible multi-body method. The dynamic substructure condensation method is used to reduce the he shaft and the bearing block, obtain the flexible body model of the crankshaft and the body, reduce the computational solution scale, and improve the computational efficiency.

Modeling and Simulation of Satellite Attitude Dynamics and Control System using Modelica

The control of attitude of a satellite is difficult to verify since several subsystems of different disciplines, e.g., flexible multibody dynamics, machines, electronics and control, are involved and strongly coupled. A traditional method is to model each single discipline subsystem with a domain specific software, and combine them through interfaces. However, the problems are that lots of interfaces between software have to be developed, and manual decoupling of systems should be considered during modelling process. In this Paper, models of the dynamics and the control system are established in a unified modelling software, MWorks, which is an Integrated Development Environment of Modelica. The model can be used to verify the satellite control strategy, and also provide an effective means for satellite attitude control system design. Moreover, on this basis, the whole satellite was modelled to access state parameters changes under the coupling of the dynamic subsystem, the attitude control subsystem, the power supply subsystem, the propulsion subsystem and the integrated electronic subsystem can be synthetically considered.

Solar ray collection rate fluctuation analysis with Monte Carlo Ray Tracing method for space solar power satellite

According to the ideal optical design, the spherical concentrator made by the semi-transparent and semi-reflecting thin film is used in SSPS-OMEGA system. To obtain the continuous power, the PV array should rotate around the spherical concentrator to point the sun when SSPS-OMEGA rotate around the earth on GEO. However, considering the in-orbit assembly, the concentrator is assembled by many planar elements to be approximate to the ideal spherical concentrator. The solar ray collection rate fluctuates in certain scope because the original solar ray path is changed. In addition, planar element is deformed easily by the rotating PV array, which also lead to the fluctuation because the position of the planar element is changed. In this paper, the spherical concentrator is divided into many planar elements by using equal latitude and longitude method. It is studied that the relationship between the number of division layers and the collection rate fluctuation by using Monte Carlo Ray Tracing method. The simulation results indicate that with increasing dividing layers, the collection rate increases and the fluctuation amplitude decreases, which ranges 80.72–83.70% (2.98%) of 24-layers concentrator, ranges 88.45–89.91% (1.47%) of 48-layers concentrator, and ranges 92.46–93.80% (1.33%) of 72-layers concentrator. To solve the deformation of the concentrator, the flexible multibody dynamics model of SSPS-OMEGA is established. Combing the deformation and Monte Carlo Ray Tracing method, it is studied that the relationship between the deformation of the concentrator and the collection rate. The simulation results indicate that the stiffness of 72-layers concentrator is better than 24-layers concentrator and 48-layers concentrator, and the reduction of the collection rate of 72-layers concentrator, which is 0.4%, is less than 24-layers concentrator (1.57%) and 48-layers concentrator (0.81%).

Multi-body dynamics modeling and TMD optimization based on the improved AFSA for floating wind turbines

Compared to the onshore or fixed-bottom offshore wind turbines, floating wind turbines experience larger loads and displacements under combined effects of wind and waves. Therefore, it is necessary to control the structural vibration of floating wind turbines. First, a flexible multi-body dynamics model of a spar-type floating wind turbine is established in SIMPACK. Second, to perform the TMD parameter optimization, a simplified model of the wind turbine is constructed, and unknown parameters in the model are estimated using the Levenberg–Marquardt method. Third, the global optimization ability of the artificial fish swarm algorithm (AFSA) is improved to optimize TMD parameters. Fourth, in order to examine the vibration suppression performance of the designed TMD, a new aero-hydro-elastic-servo model of the wind turbine is built to perform simulations. The simulation results show that the optimized TMD system obtained by the improved AFSA has significant vibration control performance for the floating wind turbine.

Flexible multibody dynamics using joint coordinates and the Rayleigh‐Ritz approximation: The general framework behind and beyond Flex

AbstractThis article presents a general framework to set up the equations of motion for flexible multibody system using joint coordinates and Rayleigh‐Ritz approximation. The framework covers in particular the underlying formulation behind the aeroelastic code Flex developed by Øye. This formulation is strongly related to the one used in the module ElastoDyn of the code OpenFAST. The approach results in models with few degrees of freedom thanks to carefully selected shape functions and the direct account of the constraints. The specificities of the method for open‐loop systems and thin beams are presented. The inclusion of torsion and couplings with finite element methods or superelements are discussed. Simple validations cases are used. A four degrees of freedom model of a two‐bladed wind turbine is developed to illustrate the method.

Model order reduction based on successively local linearizations for flexible multibody dynamics

SummaryAn efficient method of model order reduction is proposed for the dynamic computation of a flexible multibody system undergoing both large overall motions and large deformations. The system is initially modeled by using the nonlinear finite elements of absolute nodal coordinate formulation and then locally linearized at a series of quasi‐static equilibrium configurations according to the given accuracy in dynamic computation. By using the Craig‐Bampton method, the reduced model is established by projecting the incremental displacements of the locally linearized system onto a set of local modal bases at the quasi‐static equilibrium configuration accordingly. Afterwards, the initial conditions for the dynamic computation for the reduced model via the generalized‐α integrator can be determined from the modal bases. The analysis of computation complexity is also performed. Hence, the proposed method gives time‐varying and dimension‐varying modal bases to elaborate the efficient model reduction. Finally, three examples are presented to validate the accuracy and efficiency of the proposed method.

Multi-body Dynamic Analysis of the Braking Process for Megawatt Wind Turbine Disc Brake

The dynamic characteristics of brake during the braking process are studied by the method of multi-body dynamics, in order to reduce the vibration of disc brake in the emergency braking process, improving the braking efficiency of the brake of the megawatt wind turbine. The flexible multi-body dynamics model of the mechanical assembly for the whole megawatt wind turbine disc brake is built, including the brake spring, active brake caliper, passive brake caliper and compensatory mechanism. The simulation results under the common working conditions are compared with the test results under the same working condition to verify the model. The influence trends of braking parameters, such as initial braking speed, spring braking force and friction coefficient between the brake pairs, on the dynamic characteristics of the brake are analyzed, which provides the theoretical basis for reducing the severe vibration during the emergency braking process in this paper.

Dynamics Study of Straddle-Type Monorail Vehicle With Single-Axle Bogies-Based Full-Scale Rigid-Flexible Coupling Dynamic Model

The longitudinal drawbar and the lateral stabilizer bar of straddle-type monorail vehicle with the single-axle bogies have relatively long structure size. The multibar system leads to deformation during the driving process due to impact loads, even leads to influence on the dynamic characteristic of the hauling mechanism as well as the riding comfort of the whole vehicle. To evaluate the dynamic behavior of straddle-type monorail vehicle with single-axle bogies accurately, a full-scale rigid-flexible coupling multibody dynamics method is proposed based on multibody dynamics and finite element (FE) theory. The modal synthesis method is adopted to establish flexible multibody dynamics of the single-axle bogies. And then rigid-flexible coupling dynamic model of the straddle-type monorail vehicle is established with the ADAMS software. The validity of the full-scale model is verified. Finally, the influences of vehicle velocity, passenger mass, curve radius and the number of axles on dynamic characteristics are discussed.

A novel 3D variational aeroelastic framework for flexible multibody dynamics: Application to bat-like flapping dynamics

We present a novel three-dimensional (3D) variational aeroelastic framework for flapping wing with a flexible multibody system subjected to an external incompressible turbulent flow. The proposed aeroelastic framework consists of a three-dimensional fluid solver with a hybrid RANS/LES model based on the delayed detached eddy simulation (DDES) treatment and a nonlinear monolithic elastic structural solver for the flexible multibody system with constraints. Radial basis function (RBF) is applied in this framework to transfer the aerodynamic forces and structural displacements across the discrete non-matching interface meshes while satisfying global energy conservation. For the consistency of the interface data transfer process, the mesh motion of the fluid domain with large elastic deformation due to high-amplitude flapping motion is also performed via the standard radial basis functions. The fluid equations are discretized using a stabilized Petrov–Galerkin method in space and the generalized-α approach is employed to integrate the solution in time. The flexible multibody system is solved by using geometrically exact co-rotational finite element method and an energy decaying scheme is used to achieve numerical stability of the multibody solver with constraints. A nonlinear iterative force correction (NIFC) scheme is applied in a staggered partitioned iterative manner to maintain the numerical stability of aeroelastic coupling with strong added mass effect. An isotropic aluminum wing with flapping motion is simulated via the proposed aeroelastic framework and the accuracy of the coupled solution is validated with the available experimental data. We next study the robustness and reliability of the 3D flexible multibody aeroelastic framework for an anisotropic flapping wing flight involving battens and membranes with composite material and compare against the experimental results. Finally, we demonstrate the aeroelastic framework for a bat-like wing and examine the effects of flexibility on the flapping wing dynamics.

Versatile Absolute Nodal Coordinate Formulation Model for Dynamic Folding Wing Deployment and Flutter Analyses

Aircraft performance can be improved using morphing wing technologies, in which the wing can be deployed and folded under flight conditions, providing a wide flight envelope, good fuel efficiency, and reducing the space required to store the aircraft. Because the deployment of the wing is a nonlinear-coupled motion comprising large rigid body motion and large elastic deformation, a nonlinear folding-wing model is required to perform the necessary time-domain deployment simulation, while a linear model is required to perform the frequency-domain flutter analysis. The objective of this paper is to propose a versatile model that can be applied to both the time-domain and frequency-domain analyses of a folding wing, based on flexible multibody dynamics (MBD) using absolute nodal coordinate formulation (ANCF) and unsteady aerodynamics. This new versatile model expands the application range of the flexible MBD using ANCF in time-domain simulation, allowing it to express the coupled motion of extremely large elastic deformations and large rigid body motions that arise in next-generation aircraft. The time-domain deployment simulation conducted using the proposed model is useful for parametric deployment-system design because the model has improved calculation time. In the frequency-domain flutter analysis of a folding wing, the flutter speed obtained from the proposed model agrees with that obtained from an experiment, with an error of 4.0%, showing promise for application in next-generation aircraft design.

Simulation of EHD lubrication for heavy-duty journal bearing based on flexible multi-body dynamics

For heavy-duty journal bearing, the structural flexibility of the shaft and the bearing block has an important influence on the dynamic characteristics of bearing behaviour. Therefore, the deformation and modal resonance generated at work must be considered. In this paper a computational method for solving Elastohydrodynamic lubrication based on flexible multi-body dynamics is introduced. The dynamic substructure condensation method is used to reduce the he shaft and the bearing block, obtain the flexible body model of the crankshaft and the body, reduce the computational solution scale, and improve the computational efficiency.

Validations of Rotor Load Analysis Using Flexible Multibody Dynamics with Multiple Wake Panels for Low-Speed Flights

Rotor load predictions of the UH-60A helicopter in low-speed flights are validated using nonlinear flexible multibody dynamic analyses with multiple wake panels. A nonlinear flexible multibody dynamic analysis code, DYMORE II, is used for predicting the blade section airloads and structural loads of the UH-60A rotor in low-speed forward and descending flights at the advance ratio of 0.15. The freewake model with multiple wake panels is integrated implicitly into DYMORE II to represent effectively the BVI (blade–vortex interaction) phenomenon of the rotor in low-speed flights. For both low-speed forward and descending flights, the multiple wake panel and single wake panel models both validate the blade section normal forces (or lift forces) moderately or well with the flight test data; however, they predict the blade section pitching moments moderately or poorly. For blade structural loads, two analyses using the multiple wake panel and single wake panel models validate the oscillatory flap bending moments moderately for both flight conditions; however, they correlate the oscillatory lead–lag bending moments poorly with the measured data. In addition, the multiple wake panel and single wake panel models both validate the oscillatory torsion moment well for the low-speed descending flight; but they predict it moderately or poorly for the low-speed forward flight. Through the present study, the analyses using multiple wake panels show better predictions of the rotor loads in low-speed flights as compared to the results with a single wake panel, along with efficient and reasonable computation resource and time.

Static and dynamic bending behaviors of carbon fiber reinforced composite cantilever cylinders

In this paper a carbon fiber reinforced composite cantilever cylinder under gravity was designed using the cantilever beam theory. The finite element model of the composite cantilever cylinder was established using software ANSYS. The static and dynamic bending responses of the cantilever cylinder were investigated with the aid of the finite element method and theory of flexible multi-body dynamics. The deflection calculated using fully constraints at the root of the cantilever cylinder under gravity satisfies the design requirements. Moreover, the response curves of deflections of the cantilever cylinder with time were obtained in terms of the step motion and sinusoidal motion, respectively, using software ADAMS. The deflections of the cantilever cylinder were also evaluated for various motions. The results indicate that the maximum deflections of the cantilever cylinder for the both motion modes do not exceed the allowable design values. The present models and methods are able to provide a useful reference for design and production of carbon fiber composite cantilever cylinders.

Coupled analysis method of a mooring system and a floating crane based on flexible multibody dynamics considering contact with the seabed

The mooring system keeps the position of a floating body in the ocean under environmental loads. Mooring analysis should be performed based on the accurate mathematical model in order to predict the behaviors of the floating body and the mooring system. For this purpose, the finite element method (FEM)-based model has been widely used in recent years to model the mooring line numerically. However, existing studies were only applicable to a single floating body, and solved the equations of motion for the floating body and the mooring lines separately. For the application to a floating crane, which consists of several bodies connected to each other, the coupling effect due to the relative motion of each body should be taken into account. Therefore, in this study, the FEM-based mooring line model applicable to a multibody system is introduced based on flexible multibody dynamics. Then, to realize the interaction between the mooring line and the seabed, the non-interpenetration and slope constraints are suggested, and the friction model including sticking are adopted. For the verification of the suggested model, comparisons with the analytic solution and the commercial software are performed. Finally, the applications for a floating crane under various environmental loads are simulated. The results show that the suggested model can be properly adapted for mooring analysis.

Wing flexibility effects on the flight performance of an insect-like flapping-wing micro-air vehicle

This study explores the effects of wing flexibility on several characteristics of flight, in this case the trim conditions, power requirements and dynamic stability of an insect-like flapping-wing micro-air vehicle (FWMAV) based on the hawkmoth Manduca sexta. The wing structure is analyzed by the finite-element method. A potential-based aerodynamic model which encompasses the unsteady panel method and the extended unsteady vortex-lattice method is employed to compute the aerodynamic forces. The motions of the FWMAV are obtained using a flexible multibody dynamics program coupled with the potential-based aerodynamic model. The results of this study show that the trim conditions of insect-like flexible and rigid FWMAVs may differ significantly from each other. When the flight speed is less than 3.0 m/s, using flexible wings is favorable, as they help the FWMAV reduce the power requirement and stabilize the lateral dynamics. However, at 3.0 m/s, these advantages are almost unnoticeable, while at 4.0 m/s, the flexible insect-like FWMAV requires even more mechanical power than its rigid counterpart.

Kriging Model Based Optimization of MacPherson Strut Suspension for Minimizing Side Load using Flexible Multi-Body Dynamics

In a MacPherson strut suspension, which is one of the most popularly used vehicle suspension type, the side load is inevitably generated at the damper when wheel moves in the vertical direction. Since the side load causes friction at the damper and reduces riding comfort, it is important to reduce the side load for improving riding comfort. In this paper, an optimal design is performed to minimize the side load by using Kriging model. Before performing the optimal design, a flexible multi-body dynamics (FMBD) analysis, which can consider both multi-body dynamics and finite element method, is performed to verify the side load generated at the top of damper rod. As a result of optimal design, spring setting positions that minimize the side load are obtained and by using optimal spring setting positions, the suspension FMBD model was constructed.

Flexible multibody dynamics modelling of point-absorber wave energy converters

Abstract As an inexhaustible and environmentally-friendly energy resource, ocean wave power, which is extracted from ocean waves through WECs (wave energy converters), is highly valued by coastal countries. Compared to other types of WECs, point-absorber WECs, the main body of which can be fixed on a platform (e.g. ship), save on installation costs and therefore have concentrated significant interest among researchers and technology developers. In the development of point-absorber WECs, it is crucial to develop a reliable structural model to accurately predict the structural dynamic responses of WECs subjected to wave loadings. In this work, a FMBD (flexible multibody dynamics) model, which is a combination of MBD (multibody dynamics) and FEA (finite element analysis), has been developed for point-absorber WECs. The FMBD model has been applied to the structural modelling of the NOTC (National Ocean Technology Centre) 10 kW multiple-point-absorber WEC. The floater arm tip displacement and velocity obtained from the FMBD model are validated against the values obtained from an analytical model, which is also developed in this work. The results from the FMBD model show reasonable agreement with those from the analytical model, with a relative difference of 10.1% at the maximum value of the floater arm tip displacement. The FMBD model is further used to calculate the stress distributions, fatigue life, deformations, modal frequencies and modal shapes of the structure. The results indicate that WECs are prone to experience fatigue failure, with the shortest fatigue life (2 years) observed in the floater arm. The FMBD model developed in this work is demonstrated to be capable of accurately modelling point-absorber WECs, providing valuable information for designers to further optimise the structure and assess the reliability of WECs.

Research on Equivalent Tests of Dynamics of On-orbit Soft Contact Technology Based on On-Orbit Experiment Data

Currently, space robots have been become a very important means of space on-orbit maintenance and support. Many countries are taking deep research and experiment on this. Because space operation attitude is very complicated, it is difficult to model them in research lab. This paper builds up a complete equivalent experiment framework according to the requirement of proposed space soft-contact technology. Also, this paper carries out flexible multi-body dynamics parameters verification for on-orbit soft-contact mechanism, which combines on-orbit experiment data, the built soft-contact mechanism equivalent model and flexible multi-body dynamics equivalent model that is based on KANE equation. The experiment results approve the correctness of the built on-orbit soft-contact flexible multi-body dynamics.