Rigid-flexible Model Research Articles

Development of a multibody model for go-karts considering frame flexibility

AbstractThis study focuses on the optimization dynamics of racing go-karts, which is heavily influenced by the frame's stiffness. Lacking suspensions and differentials, go-karts rely on the frame stiffness for wheel balancing and skid prevention by lifting the inner rear wheel during turns. Utilizing a rigid-flexible model in MSC Software ADAMS View, validated by frame deformation measurements, this research integrates finite element analysis with multibody techniques. The model, leverages computer aided design files for frame geometry and employs finite element analysis for frame validation. It facilitates evaluating go-kart dynamics through simulations, aiding in maneuver testing and design optimization. This approach provides a comprehensive framework for advancing go-kart designs.

Structural Flexibility Effect on Spaceborne Solar Observation System’s Micro-Vibration Response

The spaceborne solar observation system is crucial for the study of space phenomena such as solar flares, which requires high tracking accuracy. This study presents a coupling model that integrates mechanical, electrical, and control models to investigate the structural flexibility effect on the micro-vibration response. We established a rigid–flexible model using mechanical parts. We considered the influence of flexible features while studying the dynamic responses in its operation. The state-space equations of the system showed that modal frequency, damping, and modal participation factors played significant roles. We derived transfer functions using the Laplace transform of the coupling models to better understand this mechanism, and Simulink models were thereby established. We simulated the acceleration responses of the rigid–flexible and rigid models under angle tracking modes, and the results showed significant differences. We also simulated the acceleration responses of the models under various control frequencies, and the optimal control frequency was thus obtained. Finally, we performed experiments, and the results indicated that the rigid–flexible model could better predict the motion and acceleration responses for the spaceborne solar observation system. This study provides valuable information for understanding the role of flexible features in space performance high-tracking accuracy instruments and for micro-vibration suppression research.

Insights into Modeling Approaches in Chemistry: Assessing Ligand-Protein Binding Thermodynamics Based on Rigid-Flexible Model Molecules.

In the field of chemistry, model compounds find extensive use for investigating complex objects. One prime example of such object is the protein-ligand supramolecular interaction. Prediction the enthalpic and entropic contribution to the free energy associated with this process, as well as the structural and dynamic characteristics of protein-ligand complexes poses considerable challenges. This review exemplifies modeling approaches used to study protein-ligand binding (PLB) thermodynamics by employing pairs of conformationally constrained/flexible model molecules. Strategically designing the model molecules can reduce the number of variables that influence thermodynamic parameters. This enables scientists to gain deeper insights into the enthalpy and entropy of PLB, which is relevant for medicinal chemistry and drug design. The model studies reviewed here demonstrate that rigidifying ligands may induce compensating changes in the enthalpy and entropy of binding. Some "rules of thumb" have started to emerge on how to minimize entropy-enthalpy compensation and design efficient rigidified or flexible ligands.

Rigid-flexible coupled modeling of compound multistage gear system considering flexibility of shaft and gear elastic deformation

Compound multistage gearing systems are widely used in rotating machinery to provide high speed-reduction ratios and heavy load capacity. Modeling and characterizing the dynamic behavior of compound multistage gear transmission systems provides valuable insights for the design and fault diagnosis of transmission systems. However, modeling compound multistage gear transmission systems still has some challenges due to 1) the complex interactions among multistage gear systems and 2) the flexibility, e.g., gear elastic deformation related to gear time-varying mesh stiffness (TVMS), which is affected by load and has not yet been addressed in analytical method, and shaft flexibility. In this paper, a multistage rigid-flexible model of compound multistage gear transmission systems is proposed to comprehensively understand their dynamic behaviors. The proposed method concerns the flexibility of gears and shafts and further constructs a dynamic analysis model. By this, the load-dependent TVMS considering gear tooth elastic deformation is calculated and compared with the existing method. After that, the ordinary and partial differential equations of gears and shafts are fused to characterize the coupling behaviors among multistage subsystems. Finally, the proposed model is solved using the variables separation method and modal superposition method. The accuracy of the constructed model is verified by experimental response collected from a wind turbine drive train test rig. All the characteristic frequencies and the coupled dynamic response of the whole system are obtained and analyzed. The modal energy distribution of the proposed model is depicted to illustrate the flexibility and load influence on the system operational modal, which provides a theoretical foundation for the design and fault diagnosis of a compound multistage gear system.

Research on Dynamic Characteristics of Flap Actuation System Considering Joint Clearance and Flexibility

The flight control effects and flight quality of the aircraft are influenced by the flap actuation system directly. The main motivation of this research is to develop a rigid-flexible model of the flap actuation system with clearance and to explore the coupling effects of clearance joints and flexible bodies on the system’s dynamic characteristics. A modified contact force model is used to a joint with small clearance, heavy load, and large contact area. Then, the effectiveness of an embedded modeling method of this modified model is verified. Based on this method, a rigid-flexible coupling model of the flap actuation system with multi clearance joints is established. Moreover, the influence of system parameters, such as clearance size and clearance joint position, and coupling effects of the flexibility and joint clearance on dynamic responses, are analyzed. The results show that: (1) flexible bodies act as a suspension to reduce negative effects of joint clearance on dynamic responses of a clearance-contained system; (2) one flexible body can reduce the oscillation phenomenon of joint clearances, yet the suspension effect will be gradually weaken with the increase of the clearance joint number; (3) coupling effects of the elastic deformation owing to multi flexible bodies and the collision interaction between multi clearance joints make the system tend to chaos, and the system stability is reduced. This study can contribute to predicting the collision characteristics of the aircraft transmission system and improving the transmission accuracy, response speed, and stability of the aircraft.

A novel rail corrugation suppressor using synergistic mechanism of vibration absorption and damping

Rail corrugation increases the intensity of interaction between the wheel and the rail, make the vehicle and track vibrate more strongly, and increase the rolling noise. Based on the fixed corrugation wavelength mechanism, this paper determines the required corrugation wavelength to be controlled using field investigations. A new type of corrugation suppressor is developed that combines a dynamic vibration absorber and a labyrinth damper. The purpose of the suppressor is to realize wide-band vibration resistance and energy consumption, and to control the vibrations in a specific frequency band. By analyzing the vibration transmission characteristics of a typical small-radius curved subway track, it is verified that the device can flatten the rail dynamic response function, suppress the pinned-pinned resonance of rail, and increase the transmission attenuation rate of rail vibrations. A coupled rigid-flexible model of vehicle and curved track is established. The rail vibration and corrugation growth rate before and after installing the suppressor are compared. The suppressor can reduce the 1000 Hz vibrations by 10.1 dB and decrease the medium and high frequency vibrations of the rail by 5.6 dB. At the same time, it can attenuate the rail corrugation growth rate near 500 Hz and between 700-1000 Hz. A field tracking test showed that the suppressor can effectively inhibit the initiation of 15-30 mm wavelength corrugation.

Comparison of the Satellite Attitude Control System Design using the H∞ Method and H∞/MLI with Pole Allocation Considering the Parametric Uncertainty

This paper presents the comparison of the Attitude Control System (ACS) design for a rigid-flexible satellite with two vibrations mode, using the traditional H∞method and the H∞/LMI with pole allocation considering the parametric uncertainty. In the ACS design is important take into account the influence of thestructure’s flexibility, since they can interact with the satellite rigid motion, mainly, during translational and/or rotational manoeuvrer, damaging the ACS. Usually the mathematics model obtained from the linearization and/or reduction of the rigid flexible model loses information about the flexible dynamical behaviour and introduces some uncertainty. The satellite model is represented by a flexible beam connected to a central rigid hub considering a setof parametric uncertainties. Simulations results have shown that the control law designed by the H∞/LMI method has better performance and it is more robust than H∞method since the first was able to support the action of the uncertainty perturbation and to control the rigid flexible satellite attitude and suppressing vibrations.

Analysis of the Protection Performance of Face Guard for Large Mining Height Hydraulic Support

With the increase of mining height, the problem of coal wall spalling in the working face gradually worsens. Hydraulic support and its face guard structure are the key pieces of equipment to restrain the coal wall spalling. However, at present, the hydraulic jack is mostly considered as rigid in the analysis of protection mechanism. This simplification cannot effectively reflect the true bearing state of the face guard. In order to improve the accuracy of analysis, this study considers the face guard jack as a flexible spring and establishes a rigid-flexible coupling analysis model of the face guard mechanism. First, based upon the multibody dynamics software ADAMS®, the multibody numerical model of the face guard of the hydraulic support was established. The influence of the two kinds of structures on the coal wall disturbance was analyzed and compared. Then, the rigid model was meshed. The hydraulic jacks were equivalent to the spring system, and the rigid-flexible coupling model was established. Based upon the application load on different positions of the rigid-flexible model, the load-bearing characteristics and hinge point force transfer characteristics of the two face guards were analyzed. The results show that the support efficiency of the integral type was higher than that of the split type. In the vertical support attitude, the dynamic disturbance of the coal wall, produced by the two kinds of face guards, was small. The four-bar linkage effectively improved the ultimate bearing capacity of the integral face guard. The results provide theoretical support for the design and optimization of the face guard.

Dynamics analysis of a spatial rigid-flexible linkage model subjected to optimized programmed constraints

The article presents a spatial linkage composed of rigid and flexible links subjected to work dependent programmed constraints. The key tool used for the spatial linkage dynamics derivation is an automated computational procedure for constrained dynamics generation. It serves systems subjected to holonomic and first order nonholonomic constraints and proved its effectiveness to open chain models. The procedure results in final motion equations that are in the reduced state form, i.e., constraint reaction force are eliminated during derivation. This is the essential advantage of the procedure application since it provides the smallest set of dynamic equations, which may serve motion analysis and control. The article presents extension of the procedure on linkages composed of flexible links with closed-loop kinematics, for which a spanning tree can have a serial or tree structure. Also, a new optimization procedure is proposed for constraints that are imposed upon the linkage motion. The optimization procedure aims selection of the constraint ranges due to the additional system work regimes, e.g., available power sources or energy consumption. The theoretical development of automated generation of constrained dynamics as well as the constraint optimization procedure is illustrated by the linkage model example.

Coupled rigid-flexible modelling and dynamic characteristic analysis of electromechanical brake (EMB) units on trains

The electromechanical braking is a novel braking mode, which is the development direction of the electrification and intelligent train braking system. In this paper, a coupled-rigid-flexible model of the EMB unit is developed, and dynamic characteristics of the EMB unit are analysed based on the model. Firstly, assumed mode method is used to describe the axial and torsional vibration of the screw in nut-screw assembly, and lumped mass method is used to describe motions of other components in the EMB unit. Secondly, the EMB unit model is established and simulated in Matlab/Simulink software based on electro-mechanical and rigid-flexible coupling characteristics. Then the model parameters are calibrated by experiment. Finally, the simulated model is studied to analyse the influence of various factors on the dynamic characteristics of the EMB unit. The results indicate that an increment in viscous damping flats the fluctuation of the pushout force. The maximal pushout force decreases and the changing trend of force is different along with the rotational structure damping increases. The flexible vibration of the screw results in higher pushout force, meanwhile the fluctuation of the force is greater with higher braking instruction current value. When the ratio of the screw length to the screw cross-sectional diameter is 30, the pushout force varies along with the friction pairs wear under vibration. The study can provide references for structure design, control design and fault diagnosis of EMB units.

Collaborative Optimization of Nonlinear Hydropneumatic Suspension Dynamic Characteristics

Abstract Vehicle handling stability and ride comfort play important roles in a vehicle’s performance. This article proposes a new concept for vehicle handling and ride optimization. The proposed method combines the handling optimization object and design variables with the ride optimization object and design variables. This optimization is based on a rigid-flexible model of a dump truck used for mining and equipped with nonlinear hydropneumatic suspension. The truck model is a composite of a flexible main-chassis and other rigid parts. Optimization is realized using the response surface model because it is based on the design of experiment (DOE) method, and then the DOE results are calculated in the rigid-flexible model. The proximate model is then optimized using Isight software. The optimized results are compared with the numerical results that are calculated in the dynamic model in the ADAMS software, the results of which indicate that the optimized dynamic performance is enhanced, including the handling and ride characteristics. The proposed method can provide a balance for vehicle performance optimization.

Fatigue failure analysis of express freight sliding side covered wagon based on the rigid-flexibility model

PurposeThe car body stiffness of express freight sliding side covered wagon decreased for the sliding and the resonance vibration based on the flexible car body has affected the dynamics performances. Dynamic loading will cause fatigue cracks and eventually lead to fatigue failure of the car body. This paper aims to investigate the influence of car body flexibility on the evaluation of the failure.Design/methodology/approachIn this paper, the railway vehicles random analysis procedure (RVRAP) is employed to study the fatigue failure of the rigid-flexibility model. Following the analysis process, the rigid-flexibility model is established and four contrastive schemes for simulation analysis are designed. To verify the results, an experimental test using the real car body structure on the vibration test plant is carried out; the RMS of dynamic stress is obtained and compared with the simulation results.FindingsThe results show that the flexibility of the car body has a crucial influence on the fatigue life.Originality/valueThe reliability is verified regarding the use of RVRAP at an appropriate stage on the antifatigue design of the vehicle.

Analysis of Vertical Vibration Mechanism of Reciprocating Compressors considering Flexibility of Piston Rod and Crosshead Subsidence

This paper is targeted on the vertical vibration of the crosshead in a reciprocating compressor, taking into consideration the crosshead subsidence. The traditional model of the compressor is usually a crank-slider mechanism system without considering the abrasion loss for any parts, thus neglecting the influence of the piston rod flexibility. A rigid-flexible model of slider-crank is described theoretically, in which the crank, connecting rod, and crosshead are treated as rigid bodies, while the piston rod connected to the crosshead is considered as a flexible body. Lagrange equation was adopted to establish the kinetic equation of the system, considering the mass of the crank, the linkage, and the crosshead. After modeling the mechanism, the simulation shows that the dynamic response of the crosshead will be greatly influenced if crosshead subsidence is considered. Additionally, the influence of the crosshead subsidence is also investigated, and some new phenomena arise especially the vertical vibration of crosshead.

Modeling of flexible reciprocating compressor considering the crosshead subsidence

Crank-slider mechanisms are important parts of heavy duty machines, including reciprocating compressors, combustion motors. This paper targets on the dynamic response of the crosshead in a reciprocating compressor, taking into consideration the crosshead deviation from the original level. The traditional model of the compressor is usually a slider-mechanism system without considering the deflection of the crosshead, thus neglecting the influence of the piston rod, which has some flexible features. In this paper, a rigid-flexible model of slider-crank is described theoretically, using the commercial software MATLAB, where the crank, connecting rod and crosshead are treated as rigid bodies, while the piston rod connected to the crosshead is considered as a flexible body. The dynamic response of the mechanism with the crosshead subsidence is discussed detailedly in this paper. After calculated theoretically, the MATLAB simulation showed that the dynamic response of the crosshead will be greatly influenced if the crosshead subsided from the original level. Also, the influence of the crosshead subsidence was also investigated, and some extra vibration of the crosshead arises.

Thermal-structural analysis for an attitude maneuvering flexible spacecraft under solar radiation

A coupled thermal-structural analysis for an attitude maneuvering spacecraft under solar radiation is conducted and the interaction between the thermally induced vibration and attitude maneuver is studied. The spacecraft consists of a rigid hub and a solar array composed of honeycomb panel. By considering the thermal stress of solar panel, the system's rigid-flexible-thermal coupling dynamic model is established in terms of the Hamiltonian Principle and non-constrained modes. Based on the finite difference method, an explicit recursive algorithm is developed to compute the transient cross-sectional temperature distribution of solar panel which is modeled as a three-layer laminated structure. The coupled thermal-structural analysis reveals that the torque, which can maneuver the spacecraft to the desired attitude in the simulation of rigid-flexible model, cannot accomplish the attitude maneuver mission for a spacecraft under solar radiation even though the desired attitude is small. In the case of large final incident angle of heat flux (the sum of initial incident angle and the maneuver attitude angle), the thermally induced vibration of a spacecraft with small damping may be unstable and the thermal flutter may occur. Moreover, the thermally induced vibration decays with time in the case of large damping.

Natural frequency analysis and experiment for 3SPS+1PS parallel hip joint manipulator based on rigid-flexible coupling theory

For analyzing natural frequency of a 3SPS+1PS parallel hip joint manipulator, a rigid-flexible coupling theory is proposed. 3SPS denotes that the PHJM has three legs and each leg type is SPS. 1PS denotes that the PHJM has one constrained leg and the constrained leg type is PS. The rigid finite element method and flexible finite element method are the base of the rigid-flexible coupling theory. Firstly, the basic element models of the PHJM are established based on the rigid-flexible coupling analysis. Secondly, the elastic dynamic models of the flexible legs are established based on the Lagrange equation and flexible finite method. Finally, the rigid-flexible coupling model of the PHJM is assembled by building the relationship between the rigid and flexible elements. Based on the rigid-flexible model, the natural frequency of the PHJM is analyzed. In addition, the effect parameters of the natural frequency are analyzed. The analysis results of the natural frequency show that the natural frequency is symmetric distribution in the working space, and the minimum value of the 1st order natural frequency is 2.3 Hz. The operating frequency (1 Hz) is much lower than the 1st order natural frequency, so the PHJM will not generate resonance and can operate stably. The analysis results of the parameter show that the PHJM has the minimal sensitivity with the effect parameter E and has the maximal sensitivity with the effect parameter H, so the length of the middle leg has the biggest impact on the natural frequency. Natural frequency analysis results have been checked by the hammer test, which verifies the feasibility of the rigid-flexible coupling theory. At the same time, the regression analysis is carried out based on the hammer test results. Using the rigid-flexible coupling theory to solve the natural frequency of the parallel manipulator, the physical meaning is explicit and the modeling process is clear, so the rigid-flexible coupling theory is a universal method.

Dynamic analysis of a planar slider-crank mechanism with clearance for a high speed and heavy load press system

In dynamic analysis of a slider-crank mechanical with clearance for a closed high speed and heavy load press, elements are generally assumed to be rigid. The dynamic response is considerably changed as joint clearance and flexibility are introduced. Considering the actual features such as clearance, flexibility and friction, a rigid–flexible model is developed into ADAMS. With energy loss taken into account, the IMPACT function is employed by the contact–impact model to describe the contact response between the journal and bearing. The acceleration experiments of the slider-crank at different driving speeds are carried out. We conduct the dynamic simulations of the slider-crank mechanism and compare the numerical results with experimental data. The results reveal that the rigid-flexible coupling model, compared with the rigid model, is more effective to reflect the dynamic response of the mechanical. Meanwhile, the occurrence of motions can be divided into three types: a free flight, a continuous contact motion, and an impact motion. Furthermore, influence of the linkages flexibility, size of joint clearance, and driving speed of crank shaft on the dynamic behavior of the mechanism are studied.

Active Vibration Control and Coupled Vibration Analysis of a Parallel Manipulator with Multiple Flexible Links

This paper addresses the active vibration control and coupled vibration analysis of a planar parallel manipulator (PPM) with three flexible links. Multiple piezoelectric ceramic transducers are integrated with the flexible links to constitute the smart beam structures, and hence the vibration of the flexible link can be self-sensed and self-controlled. To prevent the spillover phenomena and improve the vibration control efficiency, the independent modal space control combined with an input shaper is developed to suppress both the structural and the residual vibration of the flexible links. The coupled vibration features between rigid and elastic motions and the interaction effects among three flexible links are theoretically analyzed based on the one-pass rigid-flexible dynamic models. Numerical simulation and experiment results show that the vibration of the three flexible links is coupled through the moving platform and the vibration suppression efficiency is getting improved with the number of controlled flexible links increased.

Dynamics Research of rigid-flexible model of crank-rocker mechanism with Multi Clearance

This paper takes the crank-rocker mechanism as the research object, purposed for the simulation of the motion pair with clearance utilizing the contact force model and the coulomb friction model, we build the virtual prototype of four-bar mechanism with clearance joints in the ADAMS. The article mainly contrasts the influence dynamics characteristics towards the mechanism multi-joint clearance between the rigid rocker and the flexible rocker. Considering the jointed arm’s flexibility, the four, five and six order modal of the rocker, generated by ANSYS as a neutral document, were imported into ADAMS for simulation. The result shows that Mechanism with four joint clearance increased the impact on the speed and the acceleration appeared greater fluctuation, the flexible rod has a buffer effect to the contact-impact forces, and the dynamic characteristics of fluctuations are improved.

A Modeling Research of Wind Tunnel Test Based on ADAMS with Rigid and Flexible Body

A new wind tunnel test bed based on the parallelogram institution was chosen to be studied in this paper. In the first way the 3D model was built in detail in the SolidWorks, and then the model was imported into ADAMS to build a rigid model and a rigid-flexible model, finally got the curves of the barycenter position’s parameters through carrying out the simulation separately, which would lay the foundation for the simulation of kinematics and dynamics of the wind tunnel test bed.