Rigid-flexible Coupling Model Research Articles

Numerical simulation of aircraft arresting process with an efficient full-scale rigid-flexible coupling dynamic model

The arresting process of carrier-based aircraft is widely recognized as a challenging task, characterized by the highest accident rate among all carrier-based aircraft operations. Dynamic simulation plays a crucial role in assessing the intricate responses of the arresting process, favoring the design of carrier-based aircraft. An efficient and accurate rigid-flexible coupling model for analyzing the dynamic response of the arresting process is proposed. By combining the dynamic characteristics of airframe, landing gear, arresting hook and arresting gear system, the rigid-flexible coupling dynamic model is established to reflect the relative motion of the coupling parts and arresting load. The dynamic model is verified through simulations of landing gear landing drops and by comparing the arresting simulation results with corresponding data in the US military standard. Additionally, simulations of the arresting process under different off-center distance and aircraft yaw angle are conducted to obtain the dynamic response of the aircraft during the arresting process. The result indicates that the rigid-flexible coupling dynamic model proposed is effective for analyzing the arresting dynamics response of carrier-based aircraft. The axial force of the arresting cable on both sides of the hook engagement point, pitch and yaw angle of aircraft are inconsistent under yaw and off-center arresting. The analysis method and obtained results provide valuable references for assessing the dynamic responses of carrier-based aircraft during arresting process and offer valuable in-sights in the design of carrier-based aircraft.

Establishment of rigid-flexible coupling model of leaf spring detector detection arm and the optimization of its accuracy

A pipeline through-diameter detector is vital in pipeline detection. Still, the commonly used through-diameter detector is a generally complex structure, sizeable structural size, not suitable for small pipe diameters, significant deformation of the pipeline, as well as high-precision detection requirements (Zhang et al., 2019). In this paper, the rigid-flexible coupling system and accuracy optimization of the detection arm of the leaf spring detector is proposed to improve the detection accuracy under the rigid-flexible coupling state. Under the condition of rigid-flexible coupling, the process and stage of over-convex defects are studied, the effects of different motion speeds, different preload forces, and different defect L/D ratios on the detection accuracy are analyzed, and the fitting values of the defects of the leaf spring detector detecting arm are obtained under the motion condition, which needs to be corrected for the right values to reduce the error and improve the detection accuracy under the condition of rigid-flexible coupling.

Online identification methods for low-order wheel polygons coupled with axle cracks

Wheel polygons pose a threat to the safety of train operations due to wheel fatigue, necessitating online identification. The online identification of wheel polygons predominantly relies on the axle box vertical nx (n-multiple integer of axle rotation frequency) signals generated by wheel polygons. The low-order vertical nx signals are easy coupling to other faults like axle cracks, leading to errors in wheel polygon identification. A signal decoupling method is crucial for removing the crack components from the vertical nx signal to obtain more accurate identification results for low-order wheel polygons. Employing principles of signal superposition for different faults, this article proposes a method to decouple the wheel polygon nx signal from the vertical nx signal by subtracting the crack-related portion. This method has been validated through an ABAQUS + SIMPACK online rigid-flexible coupling model, indicating that it significantly improves the accuracy of wheel polygon identification. The 1x amplitude of the decoupled signal decreased by 60.78%, and the 2x amplitude decreased by 55.79%.

自走式大白菜收获机切根机理分析及装置参数优化

For Chinese cabbage cutting device in the harvesting process, the problem of cutting resistance and low cutting root qualification rate will occur. This paper takes the Chinese cabbage root as the research object, analyses the root-cutting mechanism of Chinese cabbage, and determines that the main factors affecting its cutting effect are the cutter's inclination angle, rotational speed and its working speed. The finite element method is adopted to establish a rigid-flexible coupling model between the cutting device and the cabbage root, and the Response Surface Method (RSM) central composite design method is used to investigate the relationship among the cutter inclination angle, the cutter rotational speed as well as the working speed and Maximum root-cutting reaction force (MRF) of the cabbage and to further obtain the optimal combination of parameters. Field test results show that in the optimal combination of parameters, which means cutter inclination angle of 11o, cutter rotating speed of 216 r/min and working speed of 0.28 m/s, the root cutting effect is perfect. At this time, the root-cutting qualification rate of 92.81% and field productivity of 0.12 hm2/h, meet the requirements of the standard of Chinese cabbage harvesting mechanization. The results of the study can provide reference for optimization of Chinese cabbage harvesting equipment design.

Optimization of Motion Parameters and Structural Stiffness of Spatial Four-Bar Weft Insertion Mechanism of Rapier Loom

In view of the problems of poor stability and low precision of rapier belt motion of spatial four-bar weft insertion mechanism, the mechanism was optimized from two aspects, i.e., motion parameters and structural stiffness. Firstly, the motion law of the rapier belt was analyzed based on the spatial mechanism theory, and its correctness was verified by software simulation, so as to provide a theoretical basis for the optimization design. Then, minimize the maximum acceleration of the rapier belt and the constraint condition of meeting the requirements of weft insertion technology and performance, the mechanism was optimized and analyzed using ADAMS parametric modeling. Considering the non-negligible flexibility of the weft insertion mechanism working at high speed, a rigid-flexible coupling model was established and simulated. Finally, with the connecting rod as an example, aiming at reducing the acceleration error of the rapier belt, a method was proposed to reduce the influence of the flexible deformation of the component by increasing the section size and improving the structural stiffness. The results showed that the maximum acceleration of the rapier belt after optimizing the motion parameters was reduced by 35.7%, and the motion stability was improved; After the structural stiffness was optimized, the acceleration error of the rapier belt was significantly reduced, and the motion accuracy was improved.

Gear walk instability caused by brake-disc friction characteristics

A multi-body dynamic rigid-flexible coupling model of landing gear is established to study the gear walk instability caused by the friction characteristics of the brake disc. After validating the model with the experimental results, the influence of the landing gear structure and braking system parameters on gear walk is further investigated. Among the above factors, the slope of the graph for the friction coefficient of the brake disc and the relative velocity of brake stators and rotors is the most influential factor on gear walk instability. Phase trajectory analysis verifies that gear walk occurs when the coupling of multiple factors causes the system to exhibit an equivalent negative damping trend. To consider a more realistic braking case, a back propagation neural network method is employed to describe the nonlinear behavior of the friction coefficient of the brake disc. With the realistic nonlinear model of the friction coefficient, the maximum error in predicting the braking torque is less than 10% and the effect of the brake disc temperature on gear walk is performed. The results reveal that a more negative friction slope may contribute to a more severe unstable gear walk, and reducing the braking pressure is an effective approach to avoid gear walk, which provides help for future braking system design.

Analysis of Catapult-Assisted Takeoff of Carrier-Based Aircraft Based on Finite Element Method and Multibody Dynamics Coupling Method

Catapult-assisted takeoff is the initiation of flight missions for carrier-based aircrafts. Ensuring the safety of aircrafts during catapult-assisted takeoff requires a thorough analysis of their motion characteristics. In this paper, a rigid–flexible coupling model using the Finite Element Method and Multibody Dynamics (FEM-MBD) approach is developed to simulate the aircraft catapult process. This model encompasses the aircraft frame, landing gear, carrier deck, and catapult launch system. Firstly, reasonable assumptions were made for the dynamic modeling of catapult-assisted takeoff. An enhanced plasticity algorithm that includes transverse shear effects was employed to simulate the tensioning and release processes of the holdback system. Additionally, the forces applied by the launch bar and holdback bar, nonlinear aerodynamics loads, shock absorbers, and tires were introduced. Finally, a comparative analysis was conducted to assess the influence of different launch bar angles and holdback bar fracture stain on the aircraft’s attitude and landing gear dynamics during the catapult process. The proposed rigid–flexible coupling dynamics model enables an effective analysis of the dynamic behavior throughout the entire catapult process, including both the holdback bar tensioning and release, takeoff taxing, and extension of the nose landing gear phases. The results show that higher launch bar angle increase the load and extension of the nose landing gear and cause pronounced fluctuations in the aircraft’s pitch attitude. Additionally, the holdback bar fracture strain has a significant impact on the pitch angle during the first second of the aircraft catapult process, with greater holdback bar fracture strain resulting in larger pitch angle variations.

Dynamic characteristics analysis for gear transmission system in shearer cutting section under different loads

Gear transmission system is an important component of the shearer cutting part. The quality of its performance affects the reliable and high-efficiency operation of the whole system. Multi-rigid body and rigid-flexible coupling models were established respectively, and the dynamic analysis is carried out in the virtual simulation software Adams for the gear transmission system of the shearer cutting section. The dynamic characteristics of the gear transmission system under different load conditions were studied. The effects of constant load torque and step load torque on the dynamic characteristics of the drive system are explored. The research results show that the simulation results obtained from the rigid-flexible coupling model of the gear transmission system are closer to the actual operating conditions. It provides a visual means of dynamic analysis, which is more intuitive and convenient. The research methods and results can provide a reference for the further exploration of the electromechanical coupling dynamic characteristics of the motor-gear transmission system.

Rigid-flexible coupling modeling of the dual-rotor system for aero-engine

The dual-rotor system is the core component of advanced aero-engine. Establishing a reasonable, accurate, and efficient dynamics model is the key to studying the dynamics and vibration of the rotor system for aero-engine. This manuscript takes a representative aircraft engine dual-rotor system as a prototype, considers the rig-id-flexible coupling characteristics of different stiffness elastic supports and rotor structures, and establishes an analytical dynamic model of the dual-rotor system. Based on the established dynamic model, the natural char-acteristics of the dual-rotor system are analyzed. The model was validated using two different research methods: the rigid-flexible coupling multi-body system dynamics simulation platform ADAMS, and finite element analy-sis. The dynamic model of the dual-rotor system established in this paper can meet the requirements of hierar-chical rigid-flexible coupling of system and structure, overall mass distribution, and stiffness distribution. In particular, it can also effectively realize the simulation of multi-facet and multi-phase unbalanced vibration of the rotor system. The research methods of this paper can further enrich the basic theory of dynamics and vibration of the aero-engine rotor system.

Research on the dynamic characteristics of wind turbine gearboxes under the spatiotemporal inhomogeneous in the wake

In response to the problem of increasing fatigue load and frequent faults caused by the wake effect, the dynamic characteristics and fatigue life analysis of wind turbine gearbox under the Spatial-temporal non-uniformity of wake region were carried out in this paper. A rigid-flexible coupling model of gears transmission system for a 2 MW wind turbine was established. Based on the three-dimensional Station-temporal inhomogeneous wake model proposed in our previous work, the wind speed distribution of six typical locations in the wake region was obtained. Results show that, the spatiotemporal inhomogeneous effects of the wake expansion have great impact on the dynamic characteristics of the gearboxes for the downwind turbines located in different positions. Vibration energy representing the magnitude of impact energy during the operation of the gearbox is significantly higher under wake conditions than under upstream conditions; meanwhile, the gearbox vibration signal contains more impact component in the wake. The velocity deficit and increased turbulence intensity results in less intense but more complex vibration non-smoothness in the turbine transmission system. As the downwind distance downwind increases, the vibration frequency distribution of the transmission system at each moment is larger, but the vibration energy is reduced. Under the 3D spatiotemporal inhomogeneous effects of the wake expansion, the downstream turbine with staggered arrangement is less affected by wake and has a smoother vibration than the tandem arrangement. At the same downstream distance, the gear life is better in a tandem arrangement than in a staggered arrangement (a maximum value happens at the downstream distance of 6D). Research in this paper can provide references for the study of the dynamic characteristics of large wind turbine transmission systems under the wake effects as well as for the micro-siting of wind farms.

NVH Analysis and Optimization of Construction Hoist Drive System

The construction hoist drive system is a critical component of the construction hoist, and high speed and low vibration noise are essential development directions. In order to improve the NVH level of the construction hoist drive system, this paper carries out research and analysis of construction hoist drive system excitation, establishes the drive system rigid-flexible coupling dynamics model, and completes the establishment of the vibration and noise model of the drive system, simulation analysis, and optimization work. Ansys Motor CAD 2020 was used to establish the parametric model of the asynchronous motor and it was combined with the virtual work method to calculate Maxwell’s electromagnetic force to arrive at the radial electromagnetic force as the main cause of electromagnetic noise. For the mechanical excitation generated by the gearbox, the time-varying stiffness excitation, mesh shock excitation, and transmission error excitation are considered, and the transmission error of helical gears under different working conditions is calculated by combining it with Romax software 2020. The rigid-flexible coupling model of the construction hoist drive system is established. The load distribution analysis of the unit length of the tooth surface is completed for the first- and third-stage helical gears under different working conditions. The primary source of the drive system excitation is the tooth surface bias load. Based on the dynamic response analysis theory of the vibration superposition method, the maximum vibration speed of the drive system was analyzed by Romax. The maximum noise value of 78.8 dB was calculated from the acoustic power simulation of the drive system using Actran acoustic software 2022 in combination with acoustic theory, and the magnetic density amplitude of the stator teeth of the asynchronous motor was optimized based on the microscopic shaping design of the helical gear by Romax. The vibration and noise simulation of the optimized drive system shows that the vibration value is reduced to 0.75 mm/s, and the maximum noise is reduced to 70.2 dB, which is 10.9% lower than before the optimization. The overall NVH level has been improved. The optimization method to reduce the vibration noise of the drive system is explored, which can be used for vibration noise prediction and control during the development of the construction hoist drive system.

Dynamic Analysis and Numerical Simulation of Arresting Hook Engaging Cable in Carried-Based UAV Landing Process

Carrier-based unmanned aerial vehicles (UAVs) require precise evaluation methods for their landing and arresting safety due to their high autonomy and demanding reliability requirements. In this paper, an efficient and accurate simulation method is presented for studying the arresting hook engaging arresting cable process. The finite element method and multibody dynamics (FEM-MBD) approach is employed. By establishing a rigid–flexible coupling model encompassing the UAV and arresting gear system, the simulation model for the engagement process is obtained. The model incorporates multiple coordinate systems to effectively capture the relative motion between the rigid and flexible components. The model considers the material properties, arresting gear system characteristics, and UAV state during engagement. Verification is conducted by comparing simulation results with experimental data from a referenced arresting hook rebound. Finally, simulations are performed under different touchdown points and roll angles of the UAV to analyze the stress distribution of the hook, center of gravity variations, and the tire touch and rollover cable response. The proposed rigid–flexible coupling arresting dynamics model in this paper enables the effective analysis of the dynamic behavior during the arresting hook engaging arresting cable process.

Dynamic Simulation Analysis of Truck Crane Based on ADAMS

Background: With a reduction in the weight of telescopic boom crane and an increase in its lifting capacity, the contradiction between its speed, stability and safety becomes more prominent. The telescopic arm also has flexible deformation during operation, which will cause vibration of the whole vehicle system. Therefore, in order to ensure safety, accuracy, and efficiency in the working process, it is necessary to accurately predict the dynamic characteristics of the telescopic boom load in the working process. Objective: The purpose of this study is to establish a rigid-flexible coupling dynamic model of the crane, which can accurately reflect the dynamic characteristics of the telescopic boom during its operation in the simulation test. Methods: In theory, this study analyzes the characteristics of a truck crane and simplifies it as a cantilever beam. Based on the Euler-Bernoulli beam theory, the vibration differential equation of the mobile masscantilever beam system is established. In the aspect of simulation, the three-dimensional modeling software Solidworks is used to establish the solid model of the truck telescopic boom, the finite element analysis software is used to establish the finite element model of the telescopic boom, and the modal neutral file is generated and imported into ADAMS to establish the dynamic model of the truck crane multi-level flexible telescopic boom. The dynamic simulation of the virtual prototype model of the truck telescopic boom crane is carried out in ADAMS software to obtain the dynamic characteristics of the key components of crane under specific working conditions. Results: The vibration differential equation derived in theory can be used to solve the dynamic response of the crane jib under specific conditions by MATLAB programming. In the aspect of simulation, the error fluctuation and its causes in the key components of the crane in the working state are analyzed, and the rationality of the virtual prototype model is verified. Finally, through the trajectory planning of the crane under typical working conditions, the purpose of stable control of the telescopic boom system of the truck crane is realized. Conclusion: The derived equation is universal for solving the vibration of crane jib in general cases. The rigid-flexible coupling model also provides a reference for the dynamic modeling, analysis, design, and manufacture of a multi-stage flexible telescopic boom. The findings of this study can provide a reference for related patent research and development.

Research on stability control strategy of adjustable pressure wall-climbing robot based on adsorption identification

In order to solve the problem that it is difficult to accurately model the complex fluid domain in the negative pressure chamber of the robot in the process of wall climbing, and thus cannot quickly and steadily adsorb, a double closed-loop control strategy based on parameter identification and particle swarm optimization is proposed in this paper to improve the speed and stability of the adsorption response of the robot in the process of wall climbing. Firstly, a vacuum negative pressure wall climbing robot with a spring pressure regulating structure is developed, and the critical conditions of the robot’s instability are solved by mechanical analysis. Then, the rigid-flexible coupling model of the whole machine was established based on mass, spring and Maxwell viscoelastic elements. The model parameters of the adsorption system were identified by vacuum adsorption test. Compared with the experimental data, the accuracy of the model was more than 80%. On this basis, PID controller is used to adjust the adsorption response speed of the robot, a double closed-loop stable adsorption control strategy is designed, and the control parameters of the adsorption system are adjusted by using the dynamic weight standard particle swarm optimization algorithm. Finally, simulation and prototype tests show that, the proposed control strategy can shorten the static and dynamic response time of the adsorption system by about 3.5 s and 1.4 s, the flow response time by about 1.15s, the maneuvering performance of the whole system is improved by about 26%, and the parameter overshoot and steady-state error are lower, which provides a theoretical reference for the stability control and engineering application of the wall-climbing robot.

Impact of phase configuration of a helical idler gear system on the vibration

The helical idler gear system has a lot of applications for reducer. The number of idler teeth and the orientation angle between the center lines of the three gears directly determine the mesh phasing. However, their impact is often ignored in system design. This paper presents the phase configuration relationship of the idler gear system, which can be used to control the mesh phasing by adjusting the number of idler teeth and orientation angle, to achieve vibration reduction. By establishing the dynamic model of an idler gear system considering phase configuration, the effects of the idler teeth number, orientation angle, and mesh phasing on the dynamic characteristics are investigated. For odd and even idler teeth numbers, the change law of mesh phasing with orientation angle is revealed. When the orientation angle is constant, the number of idler gear teeth will directly affect the system vibration response from the mesh phasing. The mesh phasing and its vibration response change periodically with the orientation angle. In each cycle, there is an optimal mesh phasing that reduces the variation response of different modes, and its value of different periods basically remains the same. In a period of mesh phasing, the suppression mechanism of mesh phasing under different vibration modes is studied. The variation law of the optimal mesh phasing with the rotational speed is revealed, and the vibration reduction effect can reach 20% on average. Finally, the correctness of vibration response and mesh phasing relationship is verified by experiments and a rigid-flexible coupling model. The above research provides a foundation for realizing vibration reduction by adjusting phase configuration.

Experimental and Mathematical Study of Flexible–Rigid Rail Vehicle Riding Comfort and Safety

This paper analyses the dynamic behavior of a rail vehicle using experimental and simulation analysis on a multi-rigid–flex body model. The mathematical models are developed considering the car body, bogie frame, and wheel axle for rail vehicles of rigid–flexible and multi-rigid formulations, taking the car body as rigid for the rigid body analysis and the flexible car body for flex–rigid analysis. A finite element model of the car body was developed in ANSYS, and substructure and modal analyses were performed. The mathematical model is validated through an experiment conducted by the Research Design and Standards Organization. Then, the validated model is further analyzed to evaluate the running comfort, using the Sperling ride index and the running safety, by investigating the derailment coefficient and wheel load reduction rate. The impact of flexibility on the vehicle’s running stability is investigated using the rigid body dynamics model and experimental data. Compared to experimental data, the simulation results reveal that elastic vibration cannot be neglected in vehicle dynamics, since the rigid–flexible coupling model is slightly more significant than the rigid-body model for ride comfort and safety.

Research on dynamic characteristics of marine engine transmission system

As the main component of marine engine, the transmission system often produces serious vibration and noise, which will significantly affect the performance and service life of the driving mechanism. In order to provide reasonable structural design basis for marine engine transmission system, the dynamic characteristics under different working conditions were studied in this paper. A simplified rectangular structure was applied to express the instantaneous motion state model of the chain link, and the equation was expressed according to Euler kinematics theory. The MNF (modal neutral file) model was derived by making the links and pins flexible parts, and the rigid flexible coupling model of the transmission system was established based on ADAMS. Since invalid constraints were adjusted and replaced, the transmission system model could be simulated and calculated precisely under the conditions of different tension, spindle rotation speed and driving sprocket teeth number. By changing the model parameters through the single variable method, the variation rules of transmission ratio, spindle radial force, transmission ratio deviation and maximum transient stress of chain link were obtained respectively. According to the design and construction of vibration test platform, the simulation result was verified, and the spectrum response results of the chain drive system were obtained. The results show that the rigid flexible coupling model can achieve high simulation accuracy in the chain drive system. Reasonable tension and sprocket teeth number can not only reduce the amplitude, but also reduce the fluctuation of output torque and transmission ratio.

The simulation of the rigid-flexible coupling model of the tank firing on the move based on fully flexible body modeling method

Generally, the rigid-flexible coupling model based on the modal reduction method cannot realize the contact between the rigid body and the flexible body. Based on the multi-body systems dynamics and fully flexible body modeling method, the rigid-flexible coupling dynamics model of the tank gun system was constructed. Then by combining with the PID control model, the mechanical/control co-simulation model of the tank gun on the move was constructed. The influences of the control system and vehicle speed on the muzzle vibration during the shooting process were respectively analyzed. It has been shown that the control system model can effectively simulate the response characteristics of the muzzle during the move of the tank. Under the same road surface and the same control law, the frequency and amplitude of the muzzle angular displacement in the low frequency range increase with the increase of the vehicle speed. The constructed model and the simulation results are of great significance to the analysis and optimization of the shooting accuracy of the tank gun on the move.

Collaborative Simulation of Mechanical Structure and Control Systems of Leighton Chajnantor Telescope

Leighton Chajnantor Telescope (LCT) will be moved from the summit of Maunakea, Hawaii to Chajnantor Plateau, Chile and be refurbished there. Strong wind disturbance at the new site will bring great challenges to the servo control of LCT. It is necessary and important to develop a simulation platform that behaves as close as possible to the real telescope for testing the performance of the designed servo controller. In this paper, a collaborative simulation platform of LCT based on Adams and Matlab/Simulink is constructed. On this platform, the mechanical structure model of LCT can be integrated with its control system model such that a collaborative simulation of the mechanical structure and the control system of LCT can be conducted. The mechanical structure model of LCT, which contains both rigid body models (i.e., the mount) and flexible body models (i.e., the primary reflector), is developed by using Adams. The servo system model and the wind disturbance model are constructed by using Matlab/Simulink. By conducting collaborative simulation, the performances of the servo controller based on the rigid body model and the rigid-flexible coupling model of LCT are compared. The comparison shows that the controller designed based on the rigid body model does not perform well when it is employed to control the rigid-flexible coupling model of LCT. However, by readjusting parameters of the servo controller, its performance can be further improved when applied to the rigid-flexible coupling model. Therefore, an LCT model of integrated mechanical structure and control systems is very helpful for analyzing its performance more accurately and designing a better servo controller.

Design and optimization of complex mechanism flip shaping subsystem based on genetic algorithm and rigid-flexible coupled dynamic model.

In this paper, the cam connecting rod system of the high-speed group vertical machine flipping shaping mechanism is the research object. In order to solve the key problem that the flipping shaping mechanism cannot accurately complete the action when the vibration of the mechanism is large. In this paper, the finite element method is used to construct the dynamic model of the connecting rod subsystem of the flipped shaping mechanism. And The dynamic model of cam roller subsystem is established by centralized parameter method. Based on the MATLAB Genetic Algorithm toolbox and using Newmark's method, the dynamic equations of the flipped plastic mechanism system are solved. The optimal parameters of the connecting rod of the mechanism, the cam profile curve and the swing power and swing torque of the mechanism at different speeds are analyzed. The results show that the speed and convex contour line are important factors affecting the performance of the mechanism. And the pendulum force (swing torque) is the main cause of the vibration of the mechanism on the frame. Therefore, the mechanism pendulum dynamic and the swing moment are selected as the objective functions of the optimization model. By selecting the node parameters of the sixth order spline motion law and the cross-section parameters of the connecting rod as the design variables. The cam linkage system is optimally designed to obtain the optimal value. Finally, the optimal design of the flipped shaping mechanism was analyzed and compared with the original mechanism.