Rigid-flexible Coupling Multibody Research Articles

Design and Analysis of a 6-DOF Microsurgical Instruments Based on Rigid-flexible Coupling Multi-body System

Abstract In order to improve the operational accuracy of microsurgical instruments and increase the success rate of surgery, this paper carries out the design and analysis of six-degree-of-freedom (6-DOF) microsurgical instruments based on rigid-flexible coupling multi-body system. Firstly, the kinematic modeling method of the 6-DOF parallel mechanism with flexible hinges is improved based on the pseudo-rigid body theory in this paper. Secondly, a rigid-flexible coupling simulation system is built to analyze the error sources in terms of the remote center of motion (RCM), preload and side load. Then, the function of motion scaling, the accuracy of kinematic modeling and the validity of the workspace are demonstrated by analyzing the workspace. Finally, the maximum stress and modal analysis are solved to ensure the safety and reliability of the application. The analysis results show that the improved kinematic modeling method improves the positioning accuracy by more than two times, the root mean square error (RSME) at the end of the microsurgical instrument does not exceed 10μm in the workspace. And the microsurgical instrument can withstand a side load of 0.1 N at the RCM. This study will provide a reference for the structural design and control algorithm optimization of the 6-DOF parallel microsurgical instruments.

Vibration Characteristics and Simulation Verification of the Dual-Rotor System for Aeroengines with Rub-Impact Coupling Faults

To study the rub-impact fault between the dynamic and static parts of the rotor system of aeroengines, the dual-rotor system of a typical aeroengine is introduced and taken as the research object. The analytical kinetic model is established based on the Lagrange equation considering the structural characteristics of the dual-rotor system, the coupling effect of the intermediate bearing, and the rub-impact fault between the high-pressure turbine disc and the casing. The dynamic characteristics of the dual-rotor system under the rub-impact fault are analyzed, and the change rule of the rub-impact shape is obtained. The vibration coupling and transfer among the high-pressure rotor and the low-pressure rotor are revealed. The influence of the unbalanced position and the speed of high and low rotors on the vibration response of the dual rotor is obtained. The sensitivity of the vibration response of the dual rotor at different test points to rub-impact stiffness, clearance, and friction coefficient is compared. The simulation model is established based on the rigid-flexible coupling multibody dynamic simulation platform. The analytical results and simulation results are compared, which have a good consistency. The theoretical research can deepen the understanding of the nature and law of aeroengine rotor operation, expose the possible faults and design defects, greatly improve the development efficiency and quality, reduce repeated physical tests, reduce the development risk and cost, and accelerate the development process. This study can provide a theoretical basis for the monitoring and diagnosis of engine rub-impact faults and provide theoretical and practical reference for the establishment of the vibration fault test and analysis method system.

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

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

A New Vibration Absorber Design for Under-Chassis Device of a High-Speed Train

To realize the separation of vertical and lateral stiffness of the under-chassis device, a new type of vibration absorber is designed by using the negative stiffness of the disc spring in parallel with the rubber component. To solve its transmission characteristics, harmonic transfer method was used. A rigid-flexible coupling multibody dynamic model of a high-speed train with an elastic car body is established, and the vertical and lateral optimal stiffness of the under-chassis device are calculated. The Sperling index and acceleration PSD of the vehicle with the new vibration absorber and the vehicle with traditional rubber absorber are compared and analyzed. The results show that, with the new vibration absorber, vehicle’s running stability and vibration of the car body are more effective than the vehicle with the traditional rubber absorber.

Simulation Analysis on Flexible Multibody Dynamics of Drum Brake System of a Vehicle

Using flexible multibody system dynamic method, the rigid-flexible coupling multibody dynamic analysis model of the drum brake system was developed, and the kinematic and dynamic simulation of the system was processed as its object of study. Simulations show that the friction will increase with the dynamic friction coefficient, but high dynamic friction coefficient will cause the abnormal vibration and worsen the stability of the brake system, even the stability of the whole automobile.The modeling of flexible multi-body can effectively analyze and solve complex three-dimensional dynamic subjects of brake system and evaluate brake capability. Further research and study on this basis will result in a convenient and effective solution that can be much helpful to study, design and development of the brake system.

Dynamic analysis of a megawatt wind turbine drive train

The dynamic performance of a wind turbine drive train significantly influences the operation of an entire machine. In this work, a megawatt wind turbine drive train is subject to theoretical and experimental dynamic analysis. The method of rigid-flexible coupling multibody dynamics was applied to develop a dynamic model of the entire drive train. This model was then used to study the natural characteristics of the system. The blades, hub, main shaft, and speed-up gearbox in the dynamic model were modeled as flexible bodies. The potential resonances of the system were detected through Campbell and modal energy distribution analyses. Theoretical results show that the first-order natural frequency of the system is approximately 1.72 Hz. This frequency represents a torsional vibration mode, Moreover, resonances are not observed within the normal operating speed range of the drive train. An experimental remote real-time system was developed to monitor the torsional vibration of the drive train. This vibration was used to measure the torsional vibration of the system overall. The experimental results are consistent with the theoretical results.

Mechanics Modeling for Bearing Rigid-Flexible Coupling Multi-Body System Based on ADAMS

Rigid-flexible coupling model is the most common mechanics model for multi-body system, and discovering the law of multi-body system modeling is an important part of the study on multi-body mechanics. This paper uses finite element analysis software PATRAN to make flexibility treatment on the parts of deep groove ball bearing, combines with the virtual prototype technology and establishes the multi-flexibility body rigid-flexible coupling model which can truly reflect the dynamic characteristics of the bearing, and discusses the process and the matters needing attention for generating modal neutral file, realizes the precise modeling for fault bearing, and provides a new method for using virtual prototype to create model.

Ride comfort evaluation for road vehicle based on rigid-flexible coupling multibody dynamics

In the present research two different whole vehicle multibody models are established respectively, including rigid and rigid-flexible coupling multibody vehicle models. The former is all composed by rigid bodies while in the later model, the flexible rear suspension is built based on the finite element method (FEM) and mode superposition method, in which the deformations of the components are considered. The ride simulations with different speeds are carried out on a 3D digitalized road, and the weighted root mean square (RMS) of accelerations on the seat surface, backrest and at the feet are calculated. The comparison between the responses of the rigid and rigid-flexible coupling multibody models shows that the flexibility of the vehicle parts significantly affects the accelerations at each position, and it is necessary to take the flexibility effects into account for the assessment of ride comfort.

Dynamics Simulation of the Crank and Connecting Rod Mechanism of Diesel Engine

Based on the virtual prototyping technology and flexible multibody system dynamic theory, the author founded the rigid-flexible coupling multibody dynamic analysis model of the crank and connecting rod mechanism of diesel engine, combining the means of 3D solid modeling, finite element analysis and multi-body dynamic simulation. Through the simulation, the dynamic loads in the working cycle of the mechanism are obtained, which provides reference for dynamic stress and fatigue analysis of the mechanism.

4K11 Status and Perspective on the Motion and Vibration Control of Road Vehicle

This paper reviews the principles, methods and technologies for the research of motion and vibration control of road vehicle. Firstly, the general principles of dynamics are summarized comprehensively and systematically, and their internal relationships are presented from different points of view; Hamilton's principles for the mechanical and control systems are compared, and the canonical equations are derived; the symplectic solution methodology is introduced, which will benefit the crossover among multidiscipline by the unified mathematical expression; the modeling theories of Finite Element Method (FEM), rigid, flexible and rigid-flexible coupling multibody dynamics are put forward theoretically and methodologically; the qualitative and quantitative methods for the study of motion and vibration are presented. Secondly, some representative phenomena of road vehicle, including the stress and dynamic stiffening, bifurcation and chaotic motion etc., are examined. Thirdly, the Virtual Proving Ground (VPG) technique is introduced, and some researches related to vehicle dynamics active control, including NVH control, Integrated Chassis Control System (ICCS) and Adaptive Cruise Control System (ACCS) etc., are provided. Finally, a few perspectives on the motion and vibration control of road vehicle in the near future are advanced.

Study on the Modeling and Experiments for the Virtual Axis Hybrid Polishing Machine Tool by the Flexible Multibody Dynamics

The virtual axis hybrid polishing machine tool (VAHMPT) is the novel equipment developed by the authors that is aimed at the precision machining on the free-form curved surfaces. This paper establishes the dynamic equations of the spatial rigid-flexible coupling multibody systems considering the coupling for the rigid movement of the whole VAHMPT with the elastic deformation of each leg by means of the theory of dynamics of flexible multibodysystems. Meanwhile the dynamic characteristics of the hybrid machine tool is studied in detail by the dynamics simulation analysis. The dynamic simulation of the machine shows that the elastic deformation of each leg is very small during the movement of the machine and the influence of the flexibility of each leg on the trace of moving platform is not obvious due to the characteristics of joints. The dynamic characteristics of the VAHPMT is verified combining with the experiments. It is shown that the experiments result is almost accorded with the simulation analysis. The satisfied polishing effect on the curved surfaces can be obtained and the demand of the polishing can be achieved by the VAHPMT.

Study on the dynamic characteristics of a virtual-axis hybrid polishing machine tool by flexible multibody dynamics

This paper establishes the dynamic equations of the spatial rigid-flexible coupling multibody systems for a five-coordinate virtual-axis hybrid polishing machine tool, namely model JDYP51 developed by the authors. The dynamic characteristics of the hybrid machine tool are studied in detail by means of the theory of dynamics of a flexible multibody system and the finite element models of the whole machine tool and each leg respectively. The dynamic simulation of the machine shows that the elastic deformation of each leg is very small during the movement of the machine and the influence of the flexibility of each leg on the trace of moving platform is not obvious due to the characteristics of joints. At the beginning of the movement of the machine, the fundamental frequency of parallel mechanism easily leads to vibration of the machine. Therefore, the stable status of polishing can be obtained at all periods of the movement of the machine except the beginning of the movement.