Rigid Multi-body Model Research Articles

다물체 동역학을 활용한 공작기계 구조물 이송을 위한 메카트로닉 해석

In this study, a rigid multi-body dynamic model has been developed for mechatronic analysis to evaluate dynamic behavior of a machine tool. The development environment was the commercialized analysis tool, ADAMS, for rigid multi-body dynamic analysis. A simplified servo control logic was implemented in the tool using its functions in order to negate any external tool of control definition. The advantage of the internal implementation includes convenience of the analysis process by saving time and efforts. Application of this development to a machine tool helps to evaluate its dynamic behavior against feeding its component, to calculate the motor torque, and to optimize parameters of the control logic.

Flexible Dynamic Analysis of Hydraulic Excavator’s Boom

To study the dynamic response of hydraulic excavator’s boom under different road condition, this paper set up numerical model of excavator’s working device, then set up the virtual prototyping simulation model of excavator’s working device and simulated the flexible dynamic response characteristics of the boom based on multi-body dynamic software, RecurDyn. The results showed that, modeling and simulating method based on rigid multi-body coupling flexible multi-body dynamic modeling and analyzing technologies, reproduced the actual working conditions truly. The dynamic stress’s rule of variation provides an important method for the structure design and force analysis of hydraulic excavator’s working device.

A markerless estimation of the ankle–foot complex 2D kinematics during stance

A markerless technique is proposed and applied to estimate the two-dimensional joint kinematics of the shank and foot complex during the stance phase. Image sequences were acquired with a single camera from three healthy subjects while walking barefoot and with socks. Automatic segmentation of the shank and foot was performed to isolate the moving body from the background. A multi-rigid body model for the shank and foot complex, with the relevant segment anatomical axes, was defined and an image cross-correlation technique was applied to detect the anatomical axes locations throughout the movement. The proposed markerless technique was validated by acquiring the same trials also with a stereophotogrammetric marker-based system and a simple marker set. Differences in the joint kinematics estimates obtained with the two techniques fall in most cases within the intra-subject variability showing that, in selected applications, the markerless technique may replace more expensive and more experimental time demanding marker-based techniques.

Model Reduction of the Flexible Rotating Crankshaft of a Motorcycle Engine Cranktrain

This paper addresses the development of an elastodynamic model of a motorcycle engine cranktrain aimed at accurately evaluating the interactions between the crankshaft and the engine block, thus allowing an improved structural design. A rigid multibody model is first implemented and simulated; only kinematic joints are involved at this stage, leading to a statically determinate assembly of the mechanism. Such a modelling approach prevents the loads at certain interface locations to be evaluated; furthermore, high-frequency dynamic effects cannot be predicted. These drawbacks can be removed by introducing bushing-like elements and/or modelling component flexibility. In this paper, this latter aspect is the objective of the investigation; in particular, a finite element model of the crankshaft is implemented as a replacement for the corresponding rigid member. The well-established Craig-Bampton model reduction technique is used to represent the elastodynamic behaviour of the component with a limited number of coordinates. The mode selection procedure is emphasized here: a measure of modal dynamic importance, namely the effective interface mass fraction, is used to rank fixed-interface normal modes based upon their contribution to loads at the substructure interface; choosing the modal base according to such ranking leads to a minimal yet accurate representation.

Structure Improvement of the S Beam Based on the Safety of SUV

The S beam of a production SUV appeared instable deformation in frontal crash test, which was not beneficial to occupant protection. So the deformation of S beam should be controlled to improve the crashworthiness. Inner improvement structures were proposed according to the prototype S beam. A frontal crash FE model and a multi-rigid body model were developed and validated to investigate the crash safety of frontal impact. The influences of the improvements to the deformation of S beam and the energy absorption of longitudinal beams were analyzed by the FE model, and the injury risks of head and thoraces were analyzed by the multi-rigid body model. The better improvement structure was adopted in the frame for the crash test to validate the effectiveness of improved scheme, and the result shows better crash performance of frontal impact for prototype vehicle. Meanwhile, simulation study on crash safety of 40% offset crash were also conducted, which indicated that improved scheme was also beneficial for crash safety of 40% offset crash.

Full-scale vertical drop test and numerical simulation of a crashworthy helicopter seat/occupant system

A full-scale vertical drop test of a crashworthy helicopter seat/occupant system was performed to evaluate the energy-absorption capability of a new-type crashworthy seat, and to study its influence under impact conditions on the occupant responses and human tolerance. In order to gain a better understanding of the physics behind the impact, a numerical simulation of the crashworthy seat structure was carried out and the simulation results were compared with the test data. In the numerical simulation, a full-scale three-dimensional multi-rigid body model of the seat/occupant structure was developed using a commercial code, Mathematical Dynamic Model (MADYMO), associated with non-linear finite element code (LS-DYNA). Emphasis of the numerical simulation was placed on predicting the dynamic response of seat/occupant system, including the occupant motion that may lead to injuries due to intensive whipping of human body, the acceleration–time histories and the energy-absorbing behaviour of the inversion tubes and seat pan.

A simplified dynamic model for front-end loader design

The front-end loader is an indispensable machine for the off-road construction equipment industry. It is a classic example of a working machine with complex interactions between its subsystems (hydraulic, mechanical, and electrical). Dynamic models of the full-scale vehicle coupled with event-based operator models are currently used to help quantify the overall system performance, efficiency, and operability. However, these models are complex and not always necessary to characterize the response of individual subsystems. There is great value added to the design process — especially in prototyping of new vehicle platforms — in development of simpler models that can quickly and accurately define first-order measures of system loads and performance. This paper presents a subscale dynamic model, which isolates the boom and bucket manipulator systems of the front-end loader for the purpose of design load characterization. The model includes state equations governing the hydraulic dynamics across the control valves and in the cylinders, as well as soil—tool interaction loads (passive earth loads) at the bucket cutting edge. The governing equations of motion for the multi-rigid body model of the bucket linkage are developed using Kane's method. The proposed model is intended to accelerate the structural design and analysis of the boom and bucket linkage subsystems and may yield useful information for optimization purposes. The output from the dynamic simulation is compared with the field test data of the machine.

Effect of sleeper pitch on rail corrugation at a tangent track in vehicle hunting

The effect of sleeper pitch on the initiation and development of rail corrugation at tangent track is investigated using a numerical method in vehicle hunting. The numerical analysis considers a combination of Kalker's rolling contact theory with non-Hertzian form, linear frictional work model and the dynamics model of a half railway vehicle coupled with a tangent track. Kalker's theory is modified. The half vehicle has a two-axle bogie and doubled suspension systems. It is treated as a full dynamic rigid multi-body model. In the tangent track model, an Euler beam is used to model each rail, and the backward moving discrete supports of the rails are considered to simulate the action of the discrete sleeper supports on the wheels/rails in rolling contact, when the train running on the track. The sleepers are treated as rigid bodies and the ballast bed is replaced with equivalent mass bodies. The effect of the discrete sleeper supports on the normal loads of the wheels/rails is analyzed at different speeds. The easily excited resonant frequencies of the wheelset and the track at different speeds are investigated in detail. In order to find the conditions necessary for rail corrugation occurring at the tangent track through numerical simulation, the vehicle hunting at higher speed is caused by setting the appropriate initial displacement condition of the vehicle system. The numerical results show that when the yaw angle of the wheelset reaches its maximum value in the vehicle hunting the lateral creepage of the wheel and rail oscillates at sleeper passing frequency and higher track frequencies. Therefore, rail corrugation due to wear initiates with several frequencies including sleeper passing frequency, and grouped near the peaks of the wheelset yaw angle. With increasing passage number of the vehicle in hunting, the corrugation became serious and also extended further along the rail.

Effect of discrete track support by sleepers on rail corrugation at a curved track

The paper investigates into the effect of discrete track support by sleepers on the initiation and development of rail corrugation at a curved track when a railway vehicle passes through using a numerical method. The numerical method considers a combination of Kalker's rolling contact theory with non-Hertzian form, a linear frictional work model and a dynamics model of a half railway vehicle coupled with the curved track. The half-vehicle has a two-axle bogie and doubled suspension systems. It is treated as a full dynamic rigid multi-body model. In the track model, an Euler beam is used to model the rail, and the discrete track support by sleepers moving backward with respect to the vehicle running direction is considered to simulate the effect of the discrete sleeper support on the wheels/rails in rolling contact when the vehicle moves on the track. The sleeper is treated as a rigid body and the ballast bed is replaced with equivalent mass bodies. The numerical analysis exams in detail the variations of wheel/rail normal loads, the creepages, and the rail wear volume along the curved track. Their variations are much concerned with the discrete track support. The numerical results show that the discrete track support causes the fluctuating of the normal loads and creepages at a few frequencies. These frequencies comprise the passing frequency of the sleepers and the excited track resonant frequencies, which are higher than the sleeper passing frequency. Consequently, rail corrugation with several wavelengths initiates and develops. Also the results show that the contact vibrating between the curved rails and the four wheels of the same bogie has different frequencies. In this way, the different key frequencies to be excited play an important role in the initiation and development of curved rail corrugation. Therefore, the corrugations caused by the four wheels of the same bogie present different wavelengths. The paper shows and discusses the depths of the initial corrugations caused by the four wheels of the same bogie, at the entering transition curve, the circle curve and the exit transition curve of the curved track, respectively.

Efficient methodology for multibody simulations with discontinuous changes in system definition

A new method is presented for accurately and efficiently simulating multi-scale multibody systems with discontinuous changes in system definitions as encountered in adaptive switching between models with different resolutions as well as models with different system topologies. An example of model resolution change is a transition of a system from a discrete particle model to a reduced order articulated multi-rigid body model. The discontinuous changes in system definition may be viewed as an instantaneous change (release or impulsive application of) the system constraints. The method uses a spatial impulse–momentum formulation in a divide and conquer scheme. The approach utilizes a hierarchic assembly–disassembly process by traversing the system topology in a binary tree map to solve for the jumps in the system generalized speeds and the constraint impulsive loads in linear and logarithmic cost in serial and parallel implementations, respectively. The method is applicable for systems in serial chain as well as kinematical loop topologies. The coupling between the unilateral and bilateral constraints is handled efficiently through the use of kinematic joint definitions. The equations of motion for the system are produced in a hierarchic sub-structured form. This has the advantage that changes in sub-structure definitions/models results in a change to the system equations only within the associated sub-structure. This allows for significant changes in model types and definitions without having to reformulate the equations for the whole system.

Hybrid virtual prototype for analyzing cable shovel component stress

In this paper a hybrid virtual prototype is developed for analyzing the stress applied on cable shovel components by integrating flexible bodies into rigid multi-body model. The general mechanical system of the cable shovel is modeled as a seven-bar linkage with four degrees of freedom. The relevant theories applied for the dynamic model are described in terms of Lagrangian dynamics equation. The flexible body stress related to the body deformation is obtained by the dynamic equilibrium equation for a structural component based on the finite element method. A P&H 4100A cable shovel is used to validate the hybrid virtual prototype by loading the motions and loads on the model. Von Mises stress distributions of the boom, handle, hoist rope and sheave are visualized during cable shovel operation 3 sec. The results show that a high stress field is around the hoist rope. The maximum stress of 313.31 MPa occurs at node 441. By comparing the simulation results with reliability analysis results, the former is found to match well with the latter. Attention of this study is devoted to the mechanisms of damage of the cable shovel and also the critical high stress areas.

동흡진기를 사용한 광 디스크 드라이브의 진동저감

In high-speed optical disk drive, the excitation caused by rotation of a mass-unbalanced disk is a major source of vibration. The vibration can be a disturbance to the servo system, which is sufficient to cause severe failures in the reading and writing process. The vibration also causes users to feel unpleasantness. The vibration reduction is therefore essential for the reliable operation of optical disk drive. One of the approaches to reduce the vibration is a dynamic vibration absorber(DVA). In this paper, we analyze the dynamic behavior of <TEX>$DVD{\pm}RW$</TEX> combo drive system with DVA through 12-dof rigid multi-body dynamic model. The effective location and the optimal frequency ratio for the DVA are obtained from the analysis. The DVA are fabricated based on the analysis and its usefulness is confirmed.

Analysis of internal drive train dynamics in a wind turbine

AbstractThree types of multibody models are presented for the investigation of the internal dynamics of a drive train in a wind turbine. The first approach is limited to the analysis of torsional vibrations only. Then a rigid multibody model is presented with special focus on the representation of the bearings and gears in the drive train. The generic model implementation can be used for parallel as well as planetary gear stages with both helical and spur gears. Examples for different gear stages describe the use of the presented formulations. Furthermore, the influence of the helix angle and the flexibility of the bearings on the results of eigenmode calculations are discussed. The eigenmodes of a planetary stage are classified as rotational, translational or out‐of‐plane modes. Thirdly, the extension to a flexible multibody model is presented as a method to include directly the drive train components' flexibilities. Finally, a comparison of two different modelling techniques is discussed for a wind turbine's drive train with a helical parallel gear stage and two planetary gear stages. In addition, the response calculation for a torque input at the generator demonstrates which eigenmodes can be excited through this path. Copyright © 2005 John Wiley &amp; Sons, Ltd.

Limiting performance analysis of biomechanical systems for optimal injury control – Part 2: Applications

Applications of the limiting performance analysis of biomechanical systems for optimal injury control are presented. A brief review of applications based on lumped-parameter injury models is given, which includes the problems of helmets with head injuries, seat belts with thoracic injuries, helicopter seat cushions with spinal injuries, toepan padding with lower limb injuries, and child seat sled test corridors with best and worst responses. Then, the problem of ejection seat cushions for the optimal control of spinal injuries is investigated. A rigid multi-body model is developed to describe the biodynamics of the entire system including the occupant. Peak lumbar load in the vertical direction is used as the safety performance index for ejection seat cushions and is minimized. Parametric optimization is performed on a particular cushion to find its optimal performance.

Experimentation and Modelling of Climbing Phenomena of Guided Transport Vehicles

The climbing of guided transport vehicles during a crash is investigated by experiment. The experimental test at real size is the collision of moved train against another stopped train. The cinematography results describe the course of events leading to climbing and the mechanism of deformation. Next, two numerical simulations are presented, the first one is based on the global rigid multi-body model and the second one is a finite element modelling. The results of modelling and experimental comparison show how these numerical methods are of interest to the study of climbing problems.

Force and Position Control of Industrial Robots for Manufacturing Purposes

In this paper contrary to the majority of conventional position control algorithms for industrial robots (IR) which are based on rigid multi-body system models a more realistic control concept will be presented that refers to a flexible multi-body system model It provides a much better disturbance behaviour because the deflection of each joint and its time derivative are additionally considered in the closed-loop algorithm. Further improvement can be achieved by a feedforward compensation. Disturbing effects of nonlinear slip-stick friction can be compensated by the injection of high-frequency “dithering”. Moreover superimposed force control algorithms for the automatic tactile edge and surface scanning of work pieces by means of a force/torque wrist sensor will be proposed.

On the Dynamics and Control of a Flexible Industrial Robot

There are several advanced manufacturing tasks like the highly accurate cutting of geometrically difficult metal surfaces which have not yet been solved in the past by means of industrial robots because of their flexible properties mainly, caused by elasticity, plasticity or backlash within the gears. In this paper contrary to the majority of conventional position control algorithms which are based on rigid multibody system models, an alternative control concept is proposed that refers to a more realistic flexible multi-body system model. It provides both a better tracking and disturbance behaviour because not only the servo motor position but also the deflection of each joint and its time derivatives are considered in the closed-loop algorithm. Disturbing nonlinear effects of slip-stick friction can be compensated by the injection of high-frequency “dithering”. The performance quality of the proposed control concept which has been implemented on a microcomputer system will be thoroughly investigated.