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To simulate the launching process of missile complex flow, movement, and constraint states, a multifield coupling model is put forward based on a computational fluid dynamics (CFD) method. In this coupled model, a CFD method is used to solve the three-dimensional compressible transient flow, and the six-degree motion of the launching platform is considered, and the virtual contact method is used to deal with the constraint states of the guideway and the slider. The active force and moment are applied to the launching platform to simulate its rolling, pitching, and heaving motions under the 5-level waves. Collision detection is carried out through the minimum clearance distance between the slider and the guideway, and the contact force is handled by a modified Herz collision model. In the problem of launching a missile from the water surface, the change characteristics of the flow field, the load response characteristics, and the relative motion laws of the missile and the launching platform during the catapulting process are investigated. The results show that the motion laws of the projectile and the launch tube in the constrained direction are the same, and the established coupling model is able to simulate the launch separation process of the missile in the constrained state. In addition, the effect of wind load on the missile ejection process is analyzed using the coupled model. [ABSTRACT FROM AUTHOR]

The development of the straddle-type monorail tour-transit system (MTTS) has received keen attention. Regarding the unspecified regulations on the lateral stiffness limit of steel substructures, which is essential for the design of MTTSs, this work presents a comprehensive assessment of the issue. Firstly, a wind–vehicle–bridge coupling model was established, integrating multibody dynamics and finite element methods. This model was then validated against field test results, considering measured track irregularities and simulated wind loadings as the excitations. Afterwards, a trend analysis and a variance-based sensitivity analysis was performed to investigate the effect of various factors on the dynamic response of the MTTS. Results indicate that the pier height significantly impacts the lateral displacement of the pier top, accounting for 87% of the first-order sensitivity index and 75% of the total sensitivity index. In comparison, the lateral stiffness of track beams contributes over 70% to the maximum responses at the mid-span. Based on this, two responses, the lateral displacement of the pier top and the lateral deflection–span ratio of the track beam, were utilized as evaluation indicators. With the analysis of indicators in terms of lateral acceleration, Sperling index, and lateral wheel force, the limited values for the two indicators were determined as 8.04 mm and L/4200, respectively. These findings can serve as valuable references for future research and designs in this field. [ABSTRACT FROM AUTHOR]

Aiming at the problems of low soil cover and serious wear and tear of transmission parts in the soil lifting device of potato planters, this paper carries out innovative optimization design of its key parts based on TRIZ theory. The discrete element model of the soil model and the multi-body dynamic model of the soil lifting device are established, the upper scraping and lower scraping soil lifting devices are simulated respectively through the method of DEM-MBD coupling, and the working mechanism of the soil lifting device is further explored. The simulation results show that the lower scraping type lifting device has a large conveying capacity and a stable flow rate at the soil outlet. The results of the soil tank performance comparison test show that: the improved soil lifting device has a simple structure, large conveying capacity, stable flow rate, and fast flow speed and is not easily congested. It meets the standard requirements of dryland potato seedling strip mulching planting technology on mulching parameters and is of great significance for improving dryland food production on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Investigating the seeding mechanism of precision seeders is of great significance for improving the quality of cotton sowing operations. This paper designs a rotary type-hole cotton precision mulching dibbler. The main factors influencing the entry of cotton seeds into the seed wheel holes during the seeding process are then theoretically analyzed. Following this, an accurate discrete element model of coated cotton seeds is established and combined with a discrete element method (DEM) and multi-body dynamics (MBD)-coupled simulation model of the seed drill for seed picking and planting. Simulation experiments on the seeding performance of the precision dibbler were performed to study the influence of the seed wheel structure and motion parameters on the picking and planting performance under different speeds. The optimal parameter combination for the seed wheel is obtained through optimization experiments, and a precision dibbler is manufactured for bench testing. The bench test results are consistent with the simulation test results. At the precision dibbler rotation speed of 16 r/min, the qualified index reaches a maximum value of 93.28%, the skip sowing index increases with the precision dibbler rotation speed, and the re-sowing index decreases as the speed increases. These optimization results significantly improved seeding precision and efficiency and are of great significance for the reliability and effectiveness of cotton sowing operations. [ABSTRACT FROM AUTHOR]

In order to explain the phenomenon of corrugation on measured line sections of the modern tram, a numerical model of modern tram-track coupling has been established by utilizing the multi-body dynamics method, and the formation mechanism of corrugation has been studied from the perspective of wheel-rail contact creep. The results show that the smaller the curve radius is, the greater the probability of corrugation occurs. The corrugation wavelength range is 40 mm~50 mm, the wave depth range is 0.05 mm~0.1 mm, and the wave depth is relatively small compared with the corrugation wave depth of metro lines, which is in line with the characteristics of the light-load operation of the tram. The formation mechanism of corrugation on modern tram sharp curves can be described as wheel-rail contact creep saturation leads to the generation of corrugation, and the source of creep is related to the guiding mechanism of the longitudinally coupled independent wheelset bogie. The formation of corrugation on the straight line of the modern tram is related to the difference in wheel diameters between the front and rear wheelsets on the same side, which can lead to different longitudinal velocities, thus generating longitudinal creep forces and inducing rail corrugation. [ABSTRACT FROM AUTHOR]

In steel-making processes, large quantities (frequently exceeding 300 t) of liquid metal are transferred between vessels. In Basic Oxygen Steel (BOS) making process, metal is poured from Hot Metal (HM) ladles, utilising overhead gantry cranes, into furnaces for further processing. Due to the large quantities of liquid metal poured, this operation poses significant safety concerns associated with metal spillage and releases of heat emissions. This can further lead to damage being caused to surrounding infrastructure. Pouring automation can reduce the likelihood of metal spillage, optimising ladle movement for reduction in heat emission releases. Given the hazardous nature of this operation, robust testing and evaluation of automated crane pouring movements is required prior to their application. A digital twin (DT) model of an overhead gantry crane/HM ladle system is presented here, intended to provide a safe testing environment for controlled pouring movement and serve as a testbed for control system design studies. Accurate crane movement is achieved using multi-body dynamics, solving for non-linearities present due to rigid joint frictional components. The flow rate of HM is estimated through the application of a dynamic model, allowing the modelling of system dynamics due to differences in HM pouring weights. The devised DT model is evaluated by simulating real crane movement and making a comparison on the resultant changing HM weight inside the ladle. The devised DT removes the need for construction of a physical model or performing tests directly on the HM pouring system. [ABSTRACT FROM AUTHOR]

The increase in life expectancy and attention to the quality of life of elderly people spurred the need, in the last decades, to increase the capabilities of medical and surgical techniques. Among these, the development of prosthetic implants has been a staple of biomedical engineering research since the 70’s. In order to satisfy the challenging demands, the latest novelties in industrial engineering are being tested in their applicability to subjects. The 3D printing of metal alloys can produce a highly customizable product, which, after the proper heat treatments, can possess adequate mechanical properties to ensure a satisfactory component life. Defective products are often the results of wrong or absent post-processing treatments which may cause an uncontrolled crack propagation and a premature total failure of the implant. The behavior of such a product, with various critical crack conditions, was investigated by an integrated MBD-FEM co-simulation environment, focused on a femur subjected to total hip replacement. It was concluded that the Stress Intensity Factor (SIF) computed by the model is compatible with the premature failures experienced by patients, and as such, this model opens the possibility for further analyses aimed at understanding the role of defects on the durability of prothesis

The Cislunar Suspension Tether is a kind of ultra-long tether anchored to the Moon's surface and extending to the Earth's vicinity, looks like hanging from the Moon above the Earth. The tether is expected to be used for transportation between the Earth and Moon. The feasibility of constructing such a long tether in the cislunar space far away from the Earth has been validated by studying the statics of the tether with distributed mass by the current authors. In addition, dynamics of such tethered system with various initial conditions and small perturbations should be investigated. In this paper, the main dynamic characteristics of the tether are analyzed using the multi-body dynamic model. In the framework of elliptic Earth-Moon restricted three-body system, the tethered system with distributed mass is discretized using lumped masses connected by massless viscoelastic springs. The dynamic equations of the space tethered system are derived using the Lagrange method after obtaining the global potential and kinetic energies of the system. The tethered system is regarded as a Rooted-Tree System in the Earth-Moon restricted three-body system since the Moon with known motion is taken as the root of the system. The dynamic responses of each lumped mass are examined and the springs merely experiencing tensile forces rather than compressional forces are considered. The in-plane libration and elongation of the tether for the circular and elliptic cases with various initial (position and velocity) conditions are explored. Various dynamic characteristics of the tethered system influenced by the eccentricity and initial conditions are addressed and the results indicate that the extremely long lunar anchored tethered system is feasible as long as the initial conditions of the system fall into proper ranges. Some other conclusions are also presented based on the numerical experiments. • Simulation of ultra-long tether swings in the Earth-Moon restricted three-body system. • A Rooted-Tree System and its dynamic equations derived using the Euler-Lagrange equation method. • Various dynamic characteristics of the CST system influenced by the eccentricity and initial conditions. • The CST can maintain stable motion with the Moon by proper condition, but collapse or chaos by bad situation. [ABSTRACT FROM AUTHOR]

Carbody elastic vibration of a railway vehicle negatively affects the ride comfort of passengers. One of the sources of the vibration is excitation force induced by the longitudinal vibration of the bogies. The excitation force transmits to the carbody through longitudinal coupling devices between the bogie and the carbody, such as traction links and yaw dampers. Since the longitudinal coupling devices can affect running stability of the vehicle, it is necessary to develop a device which copes with both vibration reduction and running stability. The purpose of this study is to develop a device which achieves both vibration reduction and the running stability. To confirm the vibration isolation performance and also to evaluate the running stability, using multi-body dynamics software, we construct a simulation model of a test vehicle equipped with traction links and yaw dampers with rubber bushes. The simulation reveals that the elastic vibration can be reduced by the traction links equipped with soften rubber bushes. On the other hand, running stability decreases under the condition that the rubber bush of the traction link is soft, especially under the condition when another damper fails. In the simulation, we investigate the desirable displacement-load characteristics of a rubber bush for the traction link in order to reduce the carbody elastic vibration and to secure the running stability. As a result, we confirm that it is possible to cope with both vibration reduction and the running stability by configuring parameters on displacement-load characteristics of rubber bush so that the rubber bushes vibrate in small stiffness at micro amplitude and in large stiffness at large amplitude. Furthermore, we propose a design method of the vibration isolator considering running resistance, and confirm the effectiveness of the method on both vibration reduction and security of the running stability.

To simulate the launching process of missile complex flow, movement, and constraint states, a multifield coupling model is put forward based on a computational fluid dynamics (CFD) method. In this coupled model, a CFD method is used to solve the three-dimensional compressible transient flow, and the six-degree motion of the launching platform is considered, and the virtual contact method is used to deal with the constraint states of the guideway and the slider. The active force and moment are applied to the launching platform to simulate its rolling, pitching, and heaving motions under the 5-level waves. Collision detection is carried out through the minimum clearance distance between the slider and the guideway, and the contact force is handled by a modified Herz collision model. In the problem of launching a missile from the water surface, the change characteristics of the flow field, the load response characteristics, and the relative motion laws of the missile and the launching platform during the catapulting process are investigated. The results show that the motion laws of the projectile and the launch tube in the constrained direction are the same, and the established coupling model is able to simulate the launch separation process of the missile in the constrained state. In addition, the effect of wind load on the missile ejection process is analyzed using the coupled model.

Aiming at the problems of low soil cover and serious wear and tear of transmission parts in the soil lifting device of potato planters, this paper carries out innovative optimization design of its key parts based on TRIZ theory. The discrete element model of the soil model and the multi-body dynamic model of the soil lifting device are established, the upper scraping and lower scraping soil lifting devices are simulated respectively through the method of DEM-MBD coupling, and the working mechanism of the soil lifting device is further explored. The simulation results show that the lower scraping type lifting device has a large conveying capacity and a stable flow rate at the soil outlet. The results of the soil tank performance comparison test show that: the improved soil lifting device has a simple structure, large conveying capacity, stable flow rate, and fast flow speed and is not easily congested. It meets the standard requirements of dryland potato seedling strip mulching planting technology on mulching parameters and is of great significance for improving dryland food production on the Loess Plateau.

The development of the straddle-type monorail tour-transit system (MTTS) has received keen attention. Regarding the unspecified regulations on the lateral stiffness limit of steel substructures, which is essential for the design of MTTSs, this work presents a comprehensive assessment of the issue. Firstly, a wind–vehicle–bridge coupling model was established, integrating multibody dynamics and finite element methods. This model was then validated against field test results, considering measured track irregularities and simulated wind loadings as the excitations. Afterwards, a trend analysis and a variance-based sensitivity analysis was performed to investigate the effect of various factors on the dynamic response of the MTTS. Results indicate that the pier height significantly impacts the lateral displacement of the pier top, accounting for 87% of the first-order sensitivity index and 75% of the total sensitivity index. In comparison, the lateral stiffness of track beams contributes over 70% to the maximum responses at the mid-span. Based on this, two responses, the lateral displacement of the pier top and the lateral deflection–span ratio of the track beam, were utilized as evaluation indicators. With the analysis of indicators in terms of lateral acceleration, Sperling index, and lateral wheel force, the limited values for the two indicators were determined as 8.04 mm and L/4200, respectively. These findings can serve as valuable references for future research and designs in this field.

This paper presents a new type of monorail rapid transit vehicle, which can operate in formation. In order to optimize the dynamic performance of the formation vehicles when passing through the small radius curve, this paper first analyzes the structure of the new monorail rapid transit vehicle, and establishes the vehicle dynamic model and multibody dynamics simulation model. Then the improved artificial potential field algorithm is used to build the formation vehicle operation controller. Finally, the dynamic performance evaluation index of the new monorail rapid transit formation vehicle is formulated, and the formation vehicle passing through the small radius curve scene is simulated. The simulation results show that the controller of the formation vehicle with dynamic optimization control can effectively optimize the load transfer coefficient of running wheels, unbalanced centrifugal acceleration and roll angle of vehicle body when passing through the curve. Through this control method, the dynamic performance of formation vehicles passing through small radius curve lines can be optimized. [ABSTRACT FROM AUTHOR]

This study delves into the intricacies of ultraprecision machining, particularly in the context of machining optical freeform surfaces using Diamond Turning Machines (DTMs). It underscores the dynamic relationship between toolpath generation, hydrostatic bearing in DTMs, and the machining process. Central to this research is the innovative introduction of Metal Matrix Composites (MMCs) to replace the traditional materials used in designing linear bearings. This strategic substitution aims to dynamically enhance both the accuracy and the quality of the machined optical freeform surfaces. The study employs simulation-based analysis using ADAMS to investigate the interfacial cutting forces at the tooltip and workpiece surface and their impacts on the machining process. Through simulations of STS mode ultraprecision machining, the interfacial cutting forces and their relationship with changes in surface curvatures are examined. The results demonstrate that the use of MMC material leads to a significant reduction in toolpath pressure, highlighting the potential benefits of employing lightweight materials in improving the dynamic performance of the system. Additionally, the analysis of slideway joints reveals the direct influence of interfacial cutting forces on the linear slideways, emphasising the importance of understanding and controlling these forces for achieving higher-precision positioning and motion control. The comparative analysis between steel and MMC materials provides valuable insights into the effects of material properties on the system's dynamic performance. These findings contribute to the existing body of knowledge and suggest a potential shift towards more advanced precision forms, possibly extending to pico-engineering in future systems. Ultimately, this research establishes a new standard in the field, emphasising the importance of system dynamics and interfacial forces in the evolution of precision manufacturing technologies. [ABSTRACT FROM AUTHOR]

The transportation of spent nuclear fuel is an important process that involves road and sea transport from an interim storage facility to storage and final disposal sites. As spent nuclear fuel poses a significant risk, carefully evaluating its vibration and shock characteristics under normal transport conditions is essential. In this regard, full-scale multi-modal transport tests (MMTT) have been conducted domestically and internationally. In this paper, we discuss the process of developing a multi-body dynamics (MBD) model to analytically simulate conditions that cannot be considered in tests. The MBD model is based on the KORAD-21 transportation system was validated using the Korean MMTT results from 2020 to 2021. This paper summarizes the details of the development and verification of the MBD model for the KORAD-21 transportation system under normal transport test conditions. This approach can be applicable to various transportation scenarios and systems, and the results of this study will help to ensure that nuclear fuel transportation is conducted safely and effectively.

Investigating the seeding mechanism of precision seeders is of great significance for improving the quality of cotton sowing operations. This paper designs a rotary type-hole cotton precision mulching dibbler. The main factors influencing the entry of cotton seeds into the seed wheel holes during the seeding process are then theoretically analyzed. Following this, an accurate discrete element model of coated cotton seeds is established and combined with a discrete element method (DEM) and multi-body dynamics (MBD)-coupled simulation model of the seed drill for seed picking and planting. Simulation experiments on the seeding performance of the precision dibbler were performed to study the influence of the seed wheel structure and motion parameters on the picking and planting performance under different speeds. The optimal parameter combination for the seed wheel is obtained through optimization experiments, and a precision dibbler is manufactured for bench testing. The bench test results are consistent with the simulation test results. At the precision dibbler rotation speed of 16 r/min, the qualified index reaches a maximum value of 93.28%, the skip sowing index increases with the precision dibbler rotation speed, and the re-sowing index decreases as the speed increases. These optimization results significantly improved seeding precision and efficiency and are of great significance for the reliability and effectiveness of cotton sowing operations.

With the benefits of small turning radius and high trafficability, the articulated steering half-track tractor had been widely utilized in orchard and small spaced farmland. To study the dynamic performance of the articulated steering half-track tractor and provide a model basis for studying the path tracking control, an accurate multi-body dynamic model of the tractor was required. In this study, the crucial parameters in the dynamic model construction of the tractor were investigated. Firstly, the topology model of the components of the half-track tractor was built by RecurDyn, in which the movement subs and driver functions were given. Secondly, considering the difference of dynamic characteristic of the articulated steering tractor with respect to different pavement hardnesses, the soft and hard pavement models were constructed by employing the harmonic superposition method. Finally, the simulations of the half-track tractor under straight-line and swerve had been conducted on the two types of pavements, and the simulation results were compared with the experimental and theoretical results. The results indicated that the average speed error of the dynamic model on hard pavement and farmland soft pavement were 2.7% and 2.1% compared with the real tractor tests. At the same time, the straight-line driving offset errors of the dynamic model on the two pavements were 1.6% and 3.8% for the front wheels and the rear wheels offset errors were 3.9% and 2.4%, respectively. Furthermore, the turning radius error under front wheel steering was 8.2% and the error under articulated steering was 5.3%. It is proved that the established dynamic model had high accuracy, which provides an efficient approach to analyze the dynamic features of the half-track tractor. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mechanical Strength / Jixie Qiangdu is the property of Zhengzhou Research Institute of Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The yield and quality of sweet potatoes are significantly influenced by the transplantation posture of sweet potato seedlings. The performance of the sweet potato seedling transplanting opener directly affects the transplantation posture of sweet potato seedlings. In order to improve the yield and quality of sweet potatoes, this study proposes a joint simulation method based on discrete element and flexible multi body dynamics (DEM-FMBD), which optimizes the structure of a self-covering soil opener. By exploring the influence of self-covering soil trenchers on the planting depth and posture of sweet potato seedlings during horizontal transplantation, it was determined that the influencing factors of the experiment were wing spacing, soil reflux height, and soil reflux length. Based on the DEM-FMBD coupling simulation platform, single factor, and quadratic rotation orthogonal experiments were carried out. According to the results of the simulation test, the effect of the interaction of test factors on planting depth and planting attitude was analyzed by the response surface method. Finally, the optimal structural parameter combination was obtained by a multi-objective optimization method: the spacing of the wings was 58 mm, the height of the soil backflow port was 71 mm, and the length of the soil backflow port was 163 mm; thus, the quality of transplanting is improved effectively. This study provides the method and theory reference for the study of sweet potato transplanting. [ABSTRACT FROM AUTHOR]

The separation attitude of air-to-air missile to fighter should be adjusted adaptively in wide range to meet the missile-aircraft separation requirements under different flight states, but current ejection separation mechanism with fixed separation attitude could not meet the requirements. To solve this problem, a metamorphic ejection separation mechanism is proposed. Metamorphic PR-R kinematic pair is used to replace traditional hinge kinematic pair in the key hinge of ejection separation mechanism, the ejection forces of the front and rear push arm to missile are changed in real time, then missile ejection separation attitude could be adjusted adaptively in wide range. Multi-body dynamics model of metamorphic ejection separation mechanism is established, and the dynamics simulation analysis is carried out. Simulation results shows that the proposed metamorphic ejection separation mechanism could adjust separation attitude in wide range, which lays a foundation for the further realization of real-time intelligent control of the airborne missile ejection mechanism.

Abstract The suspension-type monorail (STM) is a new type of rail transit, currently developing rapidly in China. Due to its short construction duration and high terrain adaptability, STM can save large land resources. In particular, by supplementing the traffic systems in large and medium-sized cities, STM can contribute to green tourism projects. However, no systematic study is devoted to the STM transit system in China, and there is still a lack of relevant knowledge and exploration, especially for the special combination system monorail bridge. In view of the real STM bridge, namely a long-span (55 + 100 + 55)-m cable-stayed bridge in this paper, and by applying wind-vehicle-bridge coupling vibration theory, ANSYS finite element method software, and Universal Mechanism multi-body dynamics software, finite element models are established for the bridge and multi-body vehicle, respectively. Furthermore, a co-simulation method is adopted to analyze vehicle-bridge coupling vibrations and ride comfort quality. According to the results, the dynamic responses of the monorail bridge and vehicle are greatly affected by the variation in wind speed, and it is necessary to take measures to decrease system vibrations, thereby ensuring ride comfort quality for vehicle passengers.

The compression ratio of engines is one of the factors affecting the thermal efficiency of gasoline engines. The engine needs to match the best compression ratio according to the actual conditions to meet the actual requirements. Therefore, variable compression ratio technology can help achieve a balance between engine power and fuel economy under different operating conditions. Thus, a multi-link mechanism for variable compression ratio engine is designed based on the engine principle. The correctness of the mechanism design is verified by kinematics theory modeling calculation and comparative analysis of simulation results. Based on multi-body dynamics theory and considering boundary conditions such as combustion load and crankshaft speed comprehensively, the variation rule of the multi-link mechanism with control shaft rotation angle is explored; the kinematic and dynamic characteristics of the multi-link mechanism under different compression ratio conditions are evaluated, compared and analyzed in detail with those of the traditional single-link mechanism. The results show that the multi-link mechanism can realize real-time variable compression ratio to meet the actual operating conditions, has mechanical advantages in power amplification characteristics and restraining friction between piston and cylinder wall, and brings additional dynamic benefits in engine vibration.

Copyright of Railway Investigation & Surveying is the property of Railway Investigation & Surveying Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Aero Weaponry is the property of Aero Weaponry Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Maintaining stability while walking on arbitrary surfaces or dealing with external perturbations is of great interest in humanoid robotics research. Increasing the system's autonomous robustness to a variety of postural threats during locomotion is the key despite the need to evaluate noisy sensor signals. The equations of motion are the foundation of all published approaches. In contrast, we propose a more adequate evaluation of the equations of motion with respect to an arbitrary moving reference point in a non-inertial reference frame. Conceptual advantages are, e.g., getting independent of global position and velocity vectors estimated by sensor fusions or calculating the imaginary zero-moment point walking on different inclined ground surfaces. Further, we improve the calculation results by reducing noise-amplifying methods in our algorithm and using specific characteristics of physical robots. We use simulation results to compare our algorithm with established approaches and test it with experimental robot data. [ABSTRACT FROM AUTHOR]

Vertical displacement acceleration and the pitch angle record produce the phenomenon of beat vibration when testing a 200 m electro-dynamic suspension (EDS) magnetic levitation (maglev) test vehicle with high-temperature superconducting (HTS) at the CRRC Changchun Railway Vehicles Co., Ltd., where the vehicle is clamped and in planar motion. First, to examine this phenomenon, this paper establishes dynamic equations of the vehicle with three degrees of freedom (DOF), and the levitation force on each superconducting magnet (SCM) is calculated by dynamic circuit theory. Second, the theory vertical equilibrium point is obtained from the average of the levitation force for a different velocity and the magneto-motive force (MMF) of the SCM. Third, this paper decouples SCM levitation forces from each other using MATLAB/SIMULINK, and a multi-body dynamic model with six DOF is developed in SIMPACK. All vertical displacements and acceleration responses, as well as the pitch angle and acceleration response from the simulation, appear to show the phenomenon of beat vibration since there are two closing natural frequencies of approximately 2 Hz and 2.4 Hz. Finally, based on the traversing method considering the influence of the velocity, initial vertical displacement, and the MMF of the SCM, the multi-body dynamic model is frequently utilized to study the response of the mean and amplitude of vertical displacement and that of the pitch angle. The results show that increasing the MMF or velocity could decrease the vertical displacement and pitch angle; the mean vertical displacement is a little larger than the theory equilibrium point; and the amplitude of vertical displacement is small when the initial vertical displacement is near the theory equilibrium point. Both the numerical and experimental results verify the validity of the dynamic circuit model and mechanical model in this paper. [ABSTRACT FROM AUTHOR]

The suspension-type monorail (STM) is a new type of rail transit, currently developing rapidly in China. Due to its short construction duration and high terrain adaptability, STM can save large land resources. In particular, by supplementing the traffic systems in large and medium-sized cities, STM can contribute to green tourism projects. However, no systematic study is devoted to the STM transit system in China, and there is still a lack of relevant knowledge and exploration, especially for the special combination system monorail bridge. In view of the real STM bridge, namely a long-span (55 + 100 + 55)-m cable-stayed bridge in this paper, and by applying wind-vehicle-bridge coupling vibration theory, ANSYS finite element method software, and Universal Mechanism multi-body dynamics software, finite element models are established for the bridge and multi-body vehicle, respectively. Furthermore, a co-simulation method is adopted to analyze vehicle-bridge coupling vibrations and ride comfort quality. According to the results, the dynamic responses of the monorail bridge and vehicle are greatly affected by the variation in wind speed, and it is necessary to take measures to decrease system vibrations, thereby ensuring ride comfort quality for vehicle passengers. [ABSTRACT FROM AUTHOR]

This study delves into the intricacies of ultraprecision machining, particularly in the context of machining optical freeform surfaces using Diamond Turning Machines (DTMs). It underscores the dynamic relationship between toolpath generation, hydrostatic bearing in DTMs, and the machining process. Central to this research is the innovative introduction of Metal Matrix Composites (MMCs) to replace the traditional materials used in designing linear bearings. This strategic substitution aims to dynamically enhance both the accuracy and the quality of the machined optical freeform surfaces. The study employs simulation-based analysis using ADAMS to investigate the interfacial cutting forces at the tooltip and workpiece surface and their impacts on the machining process. Through simulations of STS mode ultraprecision machining, the interfacial cutting forces and their relationship with changes in surface curvatures are examined. The results demonstrate that the use of MMC material leads to a significant reduction in toolpath pressure, highlighting the potential benefits of employing lightweight materials in improving the dynamic performance of the system. Additionally, the analysis of slideway joints reveals the direct influence of interfacial cutting forces on the linear slideways, emphasising the importance of understanding and controlling these forces for achieving higher-precision positioning and motion control. The comparative analysis between steel and MMC materials provides valuable insights into the effects of material properties on the system’s dynamic performance. These findings contribute to the existing body of knowledge and suggest a potential shift towards more advanced precision forms, possibly extending to pico-engineering in future systems. Ultimately, this research establishes a new standard in the field, emphasising the importance of system dynamics and interfacial forces in the evolution of precision manufacturing technologies.

The secondary evolution of quadrupedality from bipedal ancestry is a rare evolutionary transition in tetrapods yet occurred convergently at least three times within ornithischian dinosaurs. Despite convergently evolving quadrupedal gait, ornithischians exhibited variable anatomy, particularly in the forelimbs, which underwent a major functional change from assisting in foraging and feeding in bipeds to becoming principal weight-bearing components of the locomotor system in quadrupeds. Here, we use three-dimensional multi-body dynamics models to demonstrate quantitatively that different quadrupedal ornithischian clades evolved distinct forelimb musculature, particularly around the shoulder. We find that major differences in glenohumeral abduction–adduction and long axis rotation muscle leverages were key drivers of mechanical disparity, thereby refuting previous hypotheses about functional convergence in major clades. Elbow muscle leverages were also disparate across the major ornithischian lineages, although high elbow extension muscle leverages were convergent between most quadrupeds. Unlike in ornithischian hind limbs, where differences are more closely tied to functional similarity than phylogenetic relatedness, mechanical disparity in ornithischian forelimbs appears to have been shaped primarily by phylogenetic constraints. Differences in ancestral bipedal taxa within each clade may have resulted in disparate ecomorphological constraints on the evolutionary pathways driving divergence in their quadrupedal descendants. [ABSTRACT FROM AUTHOR]

This paper presents an intelligent formation operation mode (IFOM) based on straddle-type rapid transit vehicles. Taking the straddle-type rapid transit vehicles operating in IFOM as the object, the operation mode of the vehicle is defined in the control system architecture of the straddletype rapid transit system. In addition, considering the heterogeneous operating environment of formation vehicles, an evaluation index system for formation vehicles is proposed. Then, according to the vehicle longitudinal dynamics model and the artificial potential field formation algorithm, we build the formation vehicle operation controller. After that, referring to the vehicle dynamics model, a multi rigid body dynamics simulation model of formation vehicles in a heterogeneous operating environment is established. Finally, the operating performance of formation vehicles in heterogeneous operating environment is analyzed. The analysis results show that the operation performance of the formation vehicle meets the requirements of the evaluation index system, which proves the feasibility of the formation operation of straddle-type rapid transit vehicles operating in IFOM. [ABSTRACT FROM AUTHOR]

Small-scale flapping-wing micro air vehicles (FWMAVs) are an emerging robotic technology with many applications in areas including infrastructure monitoring and remote sensing. However, challenges such as inefficient energetics and decreased payload capacity preclude the useful implementation of FWMAVs. Insects serve as inspiration to FWMAV design owing to their energy efficiency, maneuverability, and capacity to hover. Still, the biomechanics of insects remain challenging to model, thereby limiting the translational design insights we can gather from their flight. In particular, it is not well-understood how wing flexibility impacts the energy requirements of flapping flight. In this work, we developed a simple model of an insect drive train consisting of a compliant thorax coupled to a flexible wing flapping with single-degree-of-freedom rotation in a fluid environment. We applied this model to quantify the energy required to actuate a flapping wing system with parameters based off a hawkmoth Manduca sexta. Despite its simplifications, the model predicts thorax displacement, wingtip deflection and peak aerodynamic force in proximity to what has been measured experimentally in flying moths. We found a flapping system with flexible wings requires 20% less energy than a flapping system with rigid wings while maintaining similar aerodynamic performance. Passive wing deformation increases the effective angle of rotation of the flexible wing, thereby reducing the maximum rotation angle at the base of the wing. We investigated the sensitivity of these results to parameter deviations and found that the energetic savings conferred by the flexible wing are robust over a wide range of parameters. [ABSTRACT FROM AUTHOR]

An auxiliary protection device (rail holding mechanism) was proposed to control the collision attitude of subway vehicles. The dynamics model of head-on collision of subway vehicles was established and verified by the full-scale collision test of the real car; then the force element structure of the rail holding mechanism was equated; finally, the vertical lift and the pitch angle of the three characteristic sections of car body and the wheelsets were used as the evaluation indicators to study the effects of the three design parameters: the gap distance ( x 1 ), the linear stage distance ( Δ   x 2 ) and the stiffness of linear stage ( k 1 ). The results show that the linear stage distance has little influence on the collision attitude of the car body, while the x 1 and k 1 had a greater influence on the collision attitude of the car body. The reasonable reduction of the gap distance x 1 and increase the k 1 can effectively reduce the vertical lift of the wheelsets and alleviate the nodding phenomenon of the train, and reduce the derailment and jumping phenomenon during the train collision. [ABSTRACT FROM AUTHOR]

This paper presents a dynamical analysis of a tethered aerostat using a multibody simulation tool called SimscapeMultibody™. Tethered aerostats are lighter than air vehicles that float in the air and are connected to the ground through the tether. Atmospheric winds are a source of disturbance to the aerostat. The wind produces drag force that causes the aerostat to displace from its mean position. This phenomenon is called blow-by. Solving the mathematical model of the motion dynamics with time step is the conventional method used for simulating the flight dynamics of the aerostat. This paper discusses the application of Simscape Multibody™ for the three-degrees-of-freedom flight dynamic simulation of spherical tethered aerostat. Simscape Multibody™, an extension of MATLAB®/Simulink, is a multibody modeling tool in which physical bodies and their interactions have to be defined to simulate the dynamics. The mathematical model of the defined system is automatically generated by the SimscapeMultibody™ solver, and the system dynamics is simulated. The simulation of dynamics using multibody modeling tools provides high fidelity simulation for the tethered aerostats.

Abstact Taking into account the long-distance and heavy-duty working characteristics of the scraper conveyor, the harsh working environment and complex working conditions often lead to jams and chain broken accidents. In order to study the transient mechanical characteristics of the scraper conveyor’s stuck and broken chain, based on the elastic wave theory, the general equation of the chain longitudinal wave is established considering the resistance of the load, the boundary and initial value conditions are determined, and the mathematical model is analyzed and solved. Using MATLAB software, numerical simulation analysis was carried out on the dynamics of the scraper conveyor under the direct starting conditions and the stuck and broken chain fault conditions. Finally, combined with the virtual prototype technology, the multi-body dynamics simulation software ADAMS is used to analyze the dynamics of the scraper conveyor jam and chain broken conditions.The research results reveal the law of chain tension changes at the moment when the chain is stuck or broken.

This paper presents pitch control of an uninhabited airship using changes in center of gravity. Changes in center of gravity are achieved by controlling the position of a movable gondola along a rigid keel fixed to the bow of the helium envelope. The longitudinal multi-body dynamic equations of motion were developed using the measured and estimated physical properties and an adaptive PID controller was designed to control the pitch angle. Flight tests on a 4 m long uninhabited airship prototype were conducted to demonstrate the effectiveness of the method.

In this study, an automatic GNU Octave code, a free high-level language, for the educational purposes was developed to derive equations of motion and constrain equations of a multibody closed chain system and to calculate the response of the system. The code for calculating the dynamic response was developed by formulating several equations in symbolic expression and extracting differential-algebraic equations in matrix form. The code has a similar structure to the previous code for the open chained system, but it deals with the constraint equation and different numerical integration. The examples of closed chain systems provide an additional procedure to derive the constraint equations by using Lagrangian multiplication theory and to solve the differential-algebraic equations using the Runge-Kutta method. The code was made to understand the theory of analysis and the structure of calculation easily. In addition, the code has an automatic process of the derivation of the Lagrange equation and the constraint equations in matrix form after inputting the number of symbolic information such as position and velocity coordinates and design variables of the system that the user wants to review. The code was validated by comparing the dynamic response of the four-bar linkage with the same design variables and initial conditions of the previous work. By using the code, the reader's ability to exchange information such as symbols and matrices will be expected to be improved.

This work presents a bond graph (BG) model and a robust cascaded controller for a twin-rotor system (TRS). The BG model accounts for all the energetic and dynamical couplings. An adaptive integral backstepping sliding mode (AIBSM) controller is used in the outer loop to control the slow yaw and pitch dynamics of the mechanical sub-system whereas a higher-order sliding mode (HOSM) observer-based super-twisting algorithm (STA) controller is used in the inner loop to control the fast electromechanical actuator dynamics. The gain of the discontinuous control term of the integral backstepping sliding mode (IBSM) controller is adjusted by using an adaptive switching gain law, where the adaptive gain decreases or increases as the system state variables move closer to or away from a sliding surface; thereby reducing chatter and discontinuities near the sliding manifold, and ensuring a nearly smooth reference signal to the inner-loop controller. The unavailable states are estimated by using an unscented Kalman filter. All the used controllers are shown to be Lyapunov stable. The performance of the developed controller is validated through simulation and experiment, and it is further compared with other existing robust controllers. The proposed controller is robust against un-modeled dynamics and external disturbances, and it performs better, in terms of trajectory tracking error and disturbance rejection, than presently existing controllers for the TRS. • A reduced order multi energy bond graph model of a Twin Rotor System is developed. • A backstepping sliding-mode controller is designed to control yaw and pitch angles. • Asymptotic Lyapunov stability of the closed-loop system has been examined. • The developed controller was validated on an experimental set-up. [ABSTRACT FROM AUTHOR]

The CAD parametric modeling of RV reducer parts is carried out， and the parametric assembling model of cycloidal gear modification amount and dimension error of parts is established. Based on multi-body dynamics simulation technology， with bearing clearance， dynamics simulation model that includes gear contact and pin-slot contact is established. Considering the small period factors that affect the angular transmission error of RV reducer， the diameter of the needle tooth center circle and the diameter of the needle tooth groove in the same assembly dimension chain are selected to combine the errors， and the dynamics simulation is carried out under rated working conditions，the variation rule of the angular transmission error is analyzed.

Currently,the research on the low frequency vibration coupled with brake problem of landing gear is focused on longitudinal single-degree-of-freedom coupling vibration.By establishing the multi-body dynamics model of multi-degree-of-freedom low-frequency brake-induced coupling vibration of the two-wheel telescopic landing gear,and stimulating the six-degree-of-freedom bushing model at the connection between the fuselage and the main landing gear to simulate the longitudinal,lateral and torsional stiffness and damping of the landing gear pillar,the multi-degree-of-freedom coupling vibration characteristics of the landing gear are analyzed in detail.The results show that the pillar stiffness and braking torque amplitude are of great influence on the amplitude,acceleration and load of coupled vibration under the condition of low frequency braking.The coupling vibration on the landing gear can be suppressed by increasing the structural stiffness,damping and braking torque frequency or reducing the braking torque amplitude.Under the condition of asymmetric brake of the left and right wheels of the landing gear,lateral and torsional coupling vibration of the landing gear occurs,and the coupling vibration is intensified with the extended gap between the frequency and amplitude of the asymmetric braking torque of the left and right wheels.

In the switch rail section of a high-speed turnout, the wheel–rail lateral impact of the forepart of the curved switch rail is the most important factor affecting the passing performance. In order to reduce the lateral impact and improve the passing safety, a complete vehicle–track multi-body dynamics model is devised in this paper. The variation of the wheel–rail relationship when the train passes through is analyzed. The lateral force and derailment coefficient are calculated under different parameters, and the wear index is also calculated under some working conditions. The results show that properly reducing the lateral damping of the curved switch rail can effectively reduce the wheel–rail lateral force and derailment coefficient of this section, while keeping the track shape undamaged. The optimization of rail cant design plays an important role in alleviating lateral wheel–rail impact. Decreasing the height reduction of the switch rail is helpful to optimize the lateral force of the forepart of the curved switch rail. The selection of a suitable cutting mode for switch blade and reasonable control of the wheel–rail impact angle as well as passing speed have positive effects on controlling the lateral wheel–rail impact of the forepart of the curved switch rail. [ABSTRACT FROM AUTHOR]

Aerial manipulators (AM) exhibit particularly challenging, non-linear dynamics; the UAV and its manipulator form a tightly coupled dynamic system, mutually impacting each other. The mathematical model describing these dynamics forms the core of many solutions in non-linear control and deep reinforcement learning. Traditionally, the formulation of the dynamics involves Euler angle parametrization in the Lagrangian framework or quaternion parametrization in the Newton-Euler framework. The former has the disadvantage of giving birth to singularities and the latter being algorithmically complex. This work presents a hybrid solution, combining the benefits of both, namely a quaternion approach leveraging the Lagrangian framework, connecting the singularity-free parameterization with the algorithmic simplicity of the Lagrangian approach. We do so by offering detailed insights into the kinematic modeling process and the formulation of the dynamics of a general aerial manipulator. The obtained dynamics model is validated experimentally against a real-time physics engine. A practical application of the obtained dynamics model is shown in the context of a computed torque feedback controller (feedback linearization), where we analyze its real-time capability with increasingly complex AM models. [ABSTRACT FROM AUTHOR]

Compliant robotic fish can achieve a better swimming performance than rigid-bodied robotic fish. Therefore, this article investigates the swimming behavior of the compliant robotic fish based on a new swimming model that combines the large-amplitude elongated-body theory with decoupled natural orthogonal complement matrices. The simulation reveals that the multi-order resonances are generated in tail-beat amplitude, forward speed, stride length, and transport efficiency when the compliant robotic fish is driven at the corresponding frequency. Moreover, the resonant effects demonstrate the nonlinear behaviors as the driving torque increases. A control strategy for resonance utilization is presented to improve the performance capabilities. The potential influence factors for resonant effects are also discussed, showing that the tail-generated hydrodynamic force significantly impacts the resonant effect. These nonlinear characteristics can provide important guidelines for the motion control of the compliant robotic fish. [ABSTRACT FROM AUTHOR]

Multi-body dynamics is used to calculate the physical quantities required for component design, such as calculating the dynamic response of mechanical components and the time history of dynamic loads. Advances in analysis software, including DADS, ADAMS, RecurDyn, and DAFUL, have made it possible to easily calculate dynamic responses by defining relationships between components and operating environments from 3D modeling on user-created components. However, when the understating of dynamic analysis is lacking, it is difficult to apply multi-body dynamics analysis in the design process, and it is difficult to analyze the acquired response data. In this study, we developed an automatic code to derive equations of motion in the matrix format and calculate dynamic responses of multi-body systems using GNU Octave, a free high level language. In particular, the process of defining matrices and vectors such as inertia matrix, stiffness matrix, and external force vector concerning the degrees of freedom of components by using Euler-Lagrange equations is shown to understand the structure and process of dynamic analysis. The code application by explaining how to use the code in a different mechanical system is also shown to help understand the usage method for who wants to study Multi-body dynamics.

This paper presents a dynamical analysis of a tethered aerostat using a multibody simulation tool called SimscapeMultibody™. Tethered aerostats are lighter than air vehicles that float in the air and are connected to the ground through the tether. Atmospheric winds are a source of disturbance to the aerostat. The wind produces drag force that causes the aerostat to displace from its mean position. This phenomenon is called blow-by. Solving the mathematical model of the motion dynamics with time step is the conventional method used for simulating the flight dynamics of the aerostat. This paper discusses the application of Simscape Multibody™ for the three-degrees-of-freedom flight dynamic simulation of spherical tethered aerostat. Simscape Multibody™, an extension of MATLAB®/Simulink, is a multibody modeling tool in which physical bodies and their interactions have to be defined to simulate the dynamics. The mathematical model of the defined system is automatically generated by the SimscapeMultibody™ solver, and the system dynamics is simulated. The simulation of dynamics using multibody modeling tools provides high fidelity simulation for the tethered aerostats. [ABSTRACT FROM AUTHOR]

To explore the influence of virtual road surface method,virtual iteration method and fixed body method on the damage of lower control arm,the data from the test site was used. The accuracy of vehicle multi-body dynamics model was verified by suspension K＆C test and vehicle controllability and stability test. The six-component force signal of wheel center simulation value was compared with test value in the time domain and the frequency domain. The analysis results show the accuracy of 3 D virtual road and tire model; Comparison of simulation value of three methods and test value of the vertical acceleration of the wheel center shows virtual iteration method has the highest precision,and fixed body method has the worst precision. From the perspective of fatigue simulation,the results show that virtual iteration method and virtual road surface method have the same damage distribution to lower control arm. Fixed body method is quite different from the two,and is more conservative. The simulation results of lower control arm under the three load methods meet the durability of the test field.,which was consistent with the test results of indoor bench.

In order to effectively evaluate the fatigue life of a light bus body structure,the multi-body dynamics body model was built with ADAMS,the accuracy of the model was validated by calibration with measurement data. Based on measured road load data,with comprehensive application of virtual iteration and fatigue life analysis methodology,the acceleration,displacement and force response signal which acquired at proving ground were reproduced,the internal forces between body and suspension were extracted,the fatigue life of body was calculated. The rounded corner of back row seat bracket reinforcing rib exists fatigue failure risk,which is consistent with failure result of road durability test. With improvement of material trademark,the body structure was ultimately passed the durability validation of proving ground,which has shown that the engineering practicability of this methodology. The practice has proved that the combination of virtual iteration and fatigue life analysis can effectively support the fatigue life evaluation of body structure,which has reasonable engineering reference value.

In order to analyze the dynamic characteristics of locomotive traction gear transmission system under different operating conditions，taking a certain type of locomotive traction gearbox as the research object，through the Simpack multi-body dynamics software，the time-varying meshing stiffness，damping，friction and other internal excitations of the gear meshing transmission process are considered to establish a traction gear pair dynamics model. Under the two typical working conditions of low speed and high speed，the dynamic characteristics of the driven gear are compared and the amplitude-frequency characteristic curve of the angular acceleration of the torsional vibration of the driven gear is obtained by Fourier transform （FFT）. The accuracy of the dynamics model of the traction gear pair is verified through the above studies，which provides a theoretical basis for the structural optimization design of the gearbox model and the study of the tooth modification of the traction gear.

In view of the fatigue life of the key components of the dynamic stabilization device, this study adopts the method based on multi-body dynamics and finite element method, and takes the clamp oil cylinder system of the dynamic stabilization device as the research object to conduct simulation analysis. This proposed method uses ADAMS software to perform multi-body dynamics analysis on the dynamic stabilization device to obtain the force load spectrum of the clamp cylinder system. Besides, the method imports the force load spectrum into the finite element software Ansys Workbench to perform transient dynamics of the clamp cylinder system analysis. According to the results of transient dynamics analysis, the fatigue life status of the clamp cylinder system is calculated using the fatigue analysis software NCODE. The simulation analysis results show that the weakest fatigue life of the clamp cylinder system is at its root, and the minimum number of cycles is 8.807×105. [ABSTRACT FROM AUTHOR]

In this study, an automatic GNU Octave code, a free high-level language, for the educational purposes was developed to derive equations of motion and constrain equations of a multibody closed chain system and to calculate the response of the system. The code for calculating the dynamic response was developed by formulating several equations in symbolic expression and extracting differential-algebraic equations in matrix form. The code has a similar structure to the previous code for the open chained system, but it deals with the constraint equation and different numerical integration. The examples of closed chain systems provide an additional procedure to derive the constraint equations by using Lagrangian multiplication theory and to solve the differential-algebraic equations using the Runge-Kutta method. The code was made to understand the theory of analysis and the structure of calculation easily. In addition, the code has an automatic process of the derivation of the Lagrange equation and the constraint equations in matrix form after inputting the number of symbolic information such as position and velocity coordinates and design variables of the system that the user wants to review. The code was validated by comparing the dynamic response of the four-bar linkage with the same design variables and initial conditions of the previous work. By using the code, the reader's ability to exchange information such as symbols and matrices will be expected to be improved. [ABSTRACT FROM AUTHOR]