Multibody Research Articles

Dynamic responses of a vibro-impact capsule robot self-propelling in the large intestine via multibody dynamics

Abstract In recent years, colonic capsule endoscopy has become available in clinical practice as an alternative modality to colonoscopy. However, it faces challenges such as prolonged examination time and the absence of clinician navigation. Leveraging their pioneering work in the field of vibro-impact self-propulsion technique for gastrointestinal endoscopy, Zhang et al. (IEEE Robot. Autom. Lett. 8:1842–1849, 2023) developed a novel, untethered, self-propelled, endoscopic capsule robot, with the aim of providing a new means of examining bowel cancer in real time. To evaluate and optimize the passage of this capsule robot self-propelling in the large intestine, this work adopts multibody dynamics analysis and experimental investigation to study the robot’s dynamics and its interaction with the intestinal environment. Considering the complex anatomy of the large intestine, containing different sections, e.g., cecum, ascending, transverse, descending, and sigmoid colon, and variations of the haustra, e.g., with various radii, lengths, and heights, the robot was driven by the square-wave excitation of an inner mass interacting with the capsule body and tested on a real porcine colon. The robot’s driving parameters, including the excitation frequency, amplitude, and duty cycle, and the dimensions of the haustra are the two main factors influencing the robot’s progression in the intestine. By comparing with the experimental results, the proposed multibody dynamics model developed using MSC Adams can estimate the movement of the capsule robot and the intestinal resistance quantitatively. Extensive numerical and experimental studies suggest an excitation frequency of 60 Hz and a duty cycle of 0.4 as the optimal parameters for driving the robot, and the longer the haustral length is, the faster the robot passes through. These results ensure the validity of the proposed multibody dynamics platform, which can be used by robotic engineers for developing medical robots for intestinal examinations.

Optimization of Rotary Blade Wear and Tillage Resistance Based on DEM-MBD Coupling Model

To solve the problems of high tillage resistance and the rapid wear of the rotary blade during tillage, this study employed a coupled algorithm of the discrete element method (DEM) and multi-body dynamics (MBD) with Hertz–Mindlin with JKR particle contact theory to establish a rotary blade–sandy soil model. The interaction between the rotary blade and sandy soil was analyzed. The results indicated that the lateral and horizontal resistances of the rotary blade reached the peak values near the maximum tilling depth, whereas the vertical resistance reached its peak earlier. Blade wear predominantly occurred on the side cutting edge, bending zone edge, and sidelong edge, with the most significant wear observed on the sidelong edge, followed by the bending zone edge and side cutting edge, which showed similar wear patterns. To reduce wear and tillage resistance, Box–Behnken optimization was applied to optimize the blade’s local parameters. The optimal parameters—the height of the tangent edge end face was 51 mm, the bending radius was 28 mm, and the bending angle was 116°—reduced wear by 22.4% and tillage resistance by 12%. A soil disturbance analysis demonstrated that the optimized blade performs better in terms of tillage width compared to the unoptimized blade. The optimized rotary blade achieves the effects of reduced resistance and wear, improves the lifespan of the blade, reducing material loss, and meeting the requirements of sustainable agricultural production.

Dynamics Modeling and Suspension Parameters Optimization of Vehicle System Based on Reduced Multibody System Transfer Matrix Method

This study introduces an innovative vehicle-modeling framework based on the Reduced Multibody System Transfer Matrix Method, incorporating wheel–ground contact and friction to analyze dynamic performance metrics, including vertical acceleration, suspension deflection, and angular acceleration. The model is applied to simulate vehicle behavior at 40 km/h on Class D road conditions. To enhance dynamic characteristics, suspension parameters were optimized using the NSGA-II algorithm. The optimization process achieved significant reductions in vertical acceleration (24.12%), suspension deflection (25.98%), and angular acceleration (4.93%). The Pareto frontier facilitated the selection of a representative solution that balances smoothness, stability, and suspension performance. Frequency, PSD, and RMS analyses were performed under different road conditions and speeds to verify the robustness of the optimization results. The application of the transfer matrix method is extended to vehicle suspension modeling and optimization, offering valuable insights into improving ride comfort and stability. Additionally, it highlights the effectiveness of advanced multi-objective optimization techniques in improving vehicle dynamics and provides a robust methodology for practical applications.

Transversal vibration of a multi-span axially moving beam with multiple elastic supports

Using the transfer matrix method for multibody systems (MSTMM), this paper presents a dynamical model of a multi-span axially moving system with multiple elastic supports under different boundary conditions. The complex transfer matrices of an axially moving beam and a spring-damping supporting element are derived. According to the system topology, the overall transfer equation is acquired for vibration characteristic analysis. However, when dealing with multi-span systems that involve a large number of components, numerical instability may arise due to the instability of the corresponding boundary value problems. To address this issue, the reduced complex transfer matrix method (RCTMM) is developed. The state vector is artificially partitioned corresponding to the boundary condition of the system input. Numerical simulation results show that the developed method has the same computational accuracy as the MSTMM. More importantly, the RCTMM exhibits superior numerical stability, as indicated by the condition numbers of the system transfer matrix. It will provide an efficient tool for the design of mechanical multi-span axially moving systems.

A dynamic analysis model for high-altitude steep slope jointless turnouts under the coupling effect of extreme temperature and actual vehicle load

This paper focuses on the difficulty in characterising the complex mechanical behaviour and deformation characteristics of jointless turnouts at high altitudes. Considering its unique characteristics of large altitude differences, large temperature variations, frequent traction actions, vast uninhabited regions, and high failures risks, a rigid-flexible coupling dynamics model of the vehicle-jointless turnout on steep slope under the combined effects of extreme temperatures and actual vehicle loads is established. The model considers the flexible deformations of the turnout along the longitudinal, lateral, and vertical directions, enabling precise representation of temperature loads and the elastic-plastic characteristics of the longitudinal resistance of fasteners within the multi-body dynamics. The research indicates that the coupling effect of extreme temperature and vehicle impact loads can cause the longitudinal resistance of fasteners to exhibit oscillatory effects during the plastic stage, leading to a significant increase in the peak values of longitudinal creep force, shear stress, and wear index of wheel rail, exacerbating rail damage and deterioration. Extreme temperature increases can induce an advancement in the wheel load transition position, with a forward shift value reaching 0.49 m when the temperature increases by 45°C, thereby intensifying wheel-rail impacts.

Fluid-conveying pipes in the floating frame of reference formulation

Abstract This work presents a new formulation for flexible fluid-conveying pipe elements based on the widely used floating frame of reference formulation. The elements can be used as a tool for the analysis of flexible multibody systems that contain fluid-conveying pipes, as it is well known that the movement of the fluid can influence the behavior and stability of such systems. The pipe defines a control volume through which the fluid, which is considered to be a moving mass, axially flows. The velocity of a material point of the fluid is therefore a material derivative of its position, representing the large rigid movement and small elastic deformation of the pipe along with the velocity of the fluid with respect to the pipe. The equations of motion are derived through the principle of virtual work, spatial discretization by finite element interpolation functions, and model reduction. A simplification of the consistent equations of motion is proposed, which avoids the use of inertia shape integrals and reduces the effort required to implement the developed fluid-conveying pipe elements in existing multibody software. The developed elements are validated by simulation of a straight cantilevered pipe and a curved pipe constrained on one end by a hinge. A simulation of a concrete printing system illustrates the straightforward incorporation of the elements in larger multibody systems.

Hanging on the cliff: Extreme mass ratio inspiral formation with local two-body relaxation and post-Newtonian dynamics

Extreme mass ratio inspirals (EMRIs) are anticipated to be primary gravitational wave sources for the Laser Interferometer Space Antenna (LISA). They form in dense nuclear clusters when a compact object is captured by the central massive black holes (MBHs) as a consequence of the frequent two-body interactions occurring between orbiting objects. The physics of this process is complex and requires detailed statistical modelling of a multi-body relativistic system. We present a novel Monte Carlo approach to evolving the post-Newtonian (PN) equations of motion of a compact object orbiting an MBH. The approach accounts for the effects of two-body relaxation locally on the fly, without leveraging on the common approximation of orbit-averaging. We applied our method to study the function S(a_0), describing the fraction of EMRI to total captures (including EMRIs and direct plunges, DPs) as a function of the initial semi-major axis a_0 for compact objects orbiting central MBHs with M_ M M sun . The past two decades have consolidated a picture in which S(a_0)→ 0 at large initial semi-major axes, with a sharp transition from EMRIs to DPs occurring around a critical scale a_ c. A recent study challenges this notion for low-mass MBHs, finding EMRIs forming at a≫ c which were called `cliffhangers'. Our simulations confirm the existence of cliffhanger EMRIs, which we find to be more common then previously inferred. Cliffhangers start to appear for M_∙ M and can account for up to 55% of the overall EMRIs forming at those masses. We find S(a_0) ≫ 0 for a ≫ c M much higher than previously found. We test how these results are influenced by different assumptions on the dynamics used to evolve the system and treatment of two-body relaxation. We find that the PN description of the system greatly enhances the number of EMRIs by shifting a_ c to larger values at all MBH masses. Conversely, the local treatment of relaxation has a mass-dependent impact, significantly boosting the number of cliffhangers at low MBH masses compared to an orbit-averaged treatment. These findings highlight the shortcomings of standard approximations used in the EMRI literature and the importance of carefully modelling the (relativistic) dynamics of these systems. The emerging picture is more complex than previously thought, and should be considered in future estimates of rates and properties of EMRIs detectable by LISA.

Using high fidelity discrete element simulation to calibrate an expeditious terramechanics model in a multibody dynamics framework

Using high fidelity discrete element simulation to calibrate an expeditious terramechanics model in a multibody dynamics framework

Multibody System Dynamics Analysis Method Approach to Determine Dynamic Roll Early Warning and Control Thresholds of Tractor Semi-Trailer Vehicles

Multibody System Dynamics Analysis Method Approach to Determine Dynamic Roll Early Warning and Control Thresholds of Tractor Semi-Trailer Vehicles

Railway track buckling evaluation using rigid-flexible multibody dynamic model and machine learning

Railway track buckling poses a significant challenge in railway engineering, necessitating a rapid and reliable method for evaluating buckling risks to aid in its prediction and prevention. This study introduces an innovative surrogate model using a multilayer perceptron algorithm to streamline this evaluation process. The model offers an efficient alternative to time-consuming and computationally demanding three-dimensional track simulations while effectively incorporating the complexities of track dynamics data. The primary objective of this study is to reduce the evaluation process time while maintaining high accuracy of predictions. The methodology involves the generation of comprehensive track dynamics data derived from 3D track multibody dynamics model simulations and training the multilayer perceptron algorithm on this data. The dynamics model is a multibody system that includes a mixture of rigid bodies, flexible bodies, and nonlinear friction. Results indicate that the proposed surrogate model reduces the evaluation time by ∼98% while maintaining similar prediction accuracy, achieving 99.44% accuracy in replicating buckling scenarios identified by the 3D model. This demonstrates a significant improvement in computational efficiency without compromising prediction reliability. The study concludes that the developed model is a viable alternative tool for faster evaluation of buckling risks, laying the groundwork for advancing toward real-time evaluation of buckling risks.

Fatigue life evaluation of bulk cement tank trailer frame based on hot spot stress approach using the combined fe/mbd method

The bulk cement tanker trailer frame is the main load-bearing component, and it is manufactured by the welding method. Therefore, it is necessary to evaluate the fatigue strength of the trailer frame. In this study, the fatigue stress of this structure is determined by using the hot spot stress approach. First, a combined method of finite element (FE) analysis and multi-body dynamics (MBD) simulation is used to analyse the structural stress. Considering the factors of speed and road surface class in operating conditions in Vietnam, MBD simulation is used to determine the dynamic load acting on the trailer frame when the trailer is excited by an uneven road surface. The nodal stress in the time domain is determined by structural dynamic analysis of the trailer frame with this dynamic load. The linear extrapolation of stress at the reference points is then used to determine the structural hot spot stress of the critical locations. Finally, the selected fatigue curve that corresponds to the related fatigue class (FAT) is used to calculate the fatigue life. In the fatigue analysis model, the cumulative fatigue damage value is chosen taking into account the durability degradation due to the thermal influence of the welded structures

"Simulation Approach to Investigate the Influence of the Steering Wheel Angle and Vehicle Speed on the Rollover of a 4-Axle Truck Vehicle during Turning Maneuvers"

The article aims to investigate the influence of vehicle speed and steering wheel angle on the rollover condition of a 4-axle truck vehicle. A 30-degree-of-freedom (DOF) dynamic model of a 4-axle truck is established using the Multibody System Method and the Newton-Euler equation system. The vehicle body is described with 6 DOFs. Additionally, 2 DOFs are used to describe the roll motion of the front and rear masses of the vehicle body, taking into account the influence of the torsional stiffness of the vehicle frame on vehicle dynamics. The Burckhardt tire model calculates the interaction forces between tires and the road, using experimental coefficients corresponding to the road with a maximum adhesion coefficient of 0.8. The simulation uses MATLAB-Simulink, with a 5 to 65 km/h speed range and a steering wheel rotation angle ranging from 25 to 300 degrees. The results have determined the vehicle rollover conditions based on the signs of the load transfer ratio of the axle and the entire vehicle. Together with the results of lateral acceleration, yaw rate, and roll angle of the vehicle. This result can be used to propose dynamic thresholds for designing early warning systems and anti-rollover control systems for multi-axle truck vehicles.

Dynamic reliability estimation of onshore wind turbine tower based on frequency-domain method

With the upscaling of wind turbine, the issue of dynamic reliability of wind turbine towers has become increasingly evident. However, the complexity and nonlinearity of wind turbine dynamics present significant challenges in evaluating their dynamic reliability under stochastic loads, requiring substantial computational resources. In this paper, a computationally cost-effective frequency-domain method is proposed as a means of estimating the dynamic reliability of an onshore wind turbine tower. An analytical approach is employed to obtain the power spectral density (PSD) of the rated wind speed and load on the rotating blades. Secondly, a dynamic model of onshore horizontal axis onshore wind turbine is established using flexible multi-body dynamics (MBD). The linear time-varying dynamic equation is transformed into a linear time-invariant form through the application of statistical linearization method. Subsequently, complex modal analysis is used to employ the displacements and internal forces of the tower. Moreover, the first-passage reliability and fatigue reliability of the wind turbine tower are determined through power spectral analysis. A numerical example of a 5-MW wind turbine is presented to demonstrate that the proposed method yields results in good agreement with Monte Carlo simulations (MCS), thereby demonstrating its effectiveness. The reliability analysis of the 5-MW wind turbine reveals that over a 20-year design life, the first-passage reliability is 0.9997 when adopting fore-after displacement at the tower top as the failure criterion, and the fatigue reliability of the tower base is 0.9445.

Train-bridge interaction under correlated wind and rain using machine learning

The stochastic response of the high-speed train running along the bridge is susceptible to significant effects of wind and rain simultaneously. In this study, an efficient probability method for simulating the train-bridge interaction (TBI) was developed by combining wind-rain and train-bridge interaction (WRTBI) models with machine learning methods. The high-speed train was defined as multibody system (MBS) and the bridge was described over finite element method (FEM). The wind load was modeled based on the standard turbulent model and the rain load was defined according to Euler multi-phase model. The WRTBI was solved using a co-simulation method between finite element analysis and multibody system (FEA-MBS). A machine learning consisting of support vector machine (SVM) and Latin hypercube sampling (LHS) was introduced to substitute further FEA-MBS simulations, to overcome time-consuming issue. The results show that when the train runs along the bridge at the speed range of 260 km/h to 300 km/h, the maximum error is 12% in the case where the wind and rain loads are considered with the case where only the wind load is considered. The maximum displacement of the bridge in z direction increase to around 33.33%. from 25 to 100 years return period.

Analysis and Verification of a Slope Steering Model of TRVs in Hilly and Mountainous Environments

Compared to wheeled vehicles, tracked robotic vehicles have less ground pressure, greater traction adhesion, and stronger climbing and obstacle crossing capabilities, making them suitable for agricultural production in hilly areas. Good steering performance directly relates to the mobility performance and operating efficiency of tracked robotic vehicles. Affected by the ground slope, the ground pressure distribution of the vehicle’s two tracks is uneven, leading to changes in its steering performance. Therefore, analyzing and researching the steering performance of a tracked robotic vehicle under sloped conditions is of great significance. This study establishes a slope steering model for tracked robotic vehicles based on a ground pressure model of the multi-peak varying amplitude cosine distribution and the shearing displacement relationship between the track and the ground, and analyzes the impact of vehicle structural parameters, road surface parameters, and steering parameters on steering performance. To verify the proposed theoretical model, multi-body dynamics software is utilized for simulation modeling and analysis. Turning tests on different slopes are conducted on a “soil–machine–crop” integrated experimental platform. The relative error between the numerical analysis results and the virtual simulation software’s results is less than 12%, and the relative error between the numerical analysis results and the experimental results is less than 10.3%; the good consistency between the theoretical results and the simulation’s results and the experimental results indicates that the model is, indeed, correct and effective. The established steering model can provide a theoretical basis for the design and control of new steering mechanisms for agricultural tracked robotic vehicles.

Hybrid Laplace-time domain model for coupled dynamic analysis of multibody mating system in topside float-over installations

The mating operation is the most critical phase during the topside float-over installation for jacket platforms, involving complex load transfer process and nonlinear couplings among the topside, float-over barge, jacket, and other buffering devices. It is very important and yet challenging to accurately and efficiently capture the coupled dynamics of the multibody mating system, as the time domain (TD) model requires a sufficiently small time interval to clearly capture the strong impacts on the buffering devices, resulting in a worse computational efficiency. This paper innovatively proposes a hybrid Laplace-time domain (HLTD) model to improve the computational efficiency in the coupled dynamic analysis while the computational accuracy is remained. The HLTD model computes the coupled dynamics by the time-domain iterative operations, mixing the Laplace-domain pole-residue operations for computing the motion responses in each iteration. Since the tedious differential and integral solutions in the TD model are replaced by the simple algebraic pole-residue calculations, the HLTD model has much higher computational efficiency with the same computational accuracy as the TD model. By comparing with the commercial software OrcaFlex, the proposed HLTD model shows satisfactory accuracy and superior efficiency in the heave-only mating analysis during the topside float-over installation of a jacket platform.

Research on a risk assessment model for lower limb impact injuries based on multi-body dynamics

Research on a risk assessment model for lower limb impact injuries based on multi-body dynamics

Influence of energetic heavy ion sputtering on lifetime of alloy target

When energetic heavy ions are incident on negatively charged structure that collects and deposits ions, ion sputtering will occur. Metal wire is a structure commonly used for accelerating ions, the incidence of continuous high-throughput ions can cause surface loss of metal wire, affecting the service performance and lifespan of the metal wire. The SRIM software commonly used for calculating sputtering yield cannot consider the multi-body interaction problem contained in the alloy crystal structure. so, there is a significant error in calculating the sputtering yield of high-energy ions incident on alloy target. Based on the molecular dynamics method and Langevin temperature control model, the calculation model of ion sputtering parameters of energetic metal ions incident on alloy target is established in this work. The model is used to calculate the sputtering yield under the conditions of intact surface lattice of the target material and long-term incident surface lattice damage. The damages to the cathode metal wire under different incident ion fluences are further calculated, and the cross-sectional characterization of the metal wire is carried under typical working condition. The results show that the discrepancy between the experimental value and the theoretical value is less than 10%, which verifies the accuracy and applicability of the theoretical model. Based on this model, the search direction for sputtering resistant materials is proposed, meanwhile, a theoretical optimization is carried out to improve the service life of metal wire, and a method of using Ni-Ti alloy to improve the service life of metal wires is proposed, which is of great significance for predicting the service life of the metal wire under different conditions.

Study on Wear Characteristics of Surfaces Coated with HVOF and Aluminium Alloy Using Multi-Body Dynamics Analysis

Study on Wear Characteristics of Surfaces Coated with HVOF and Aluminium Alloy Using Multi-Body Dynamics Analysis

Multibody dynamics analysis of probe-drogue aerial refueling for hose whipping phenomenon

Multibody dynamics analysis of probe-drogue aerial refueling for hose whipping phenomenon