Study of human body stability under the vertical vibration action into an autovehicle using Laplace transforms

The paper presents a study for imagining of generalized mechanical model for the human body/seat assembly. The model will be used for the dynamics analyze of the human body constituent parts, under the vertical vibrations influence, transmitted by the vehicle seat during its displacement. Measures of the dynamic responses of the body are represented by the transfer functions. The human body stability is given by the found poles. The human body motion laws with four independent coordinates have been as graphical representations. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Study of the Human Body Vibrations for the Seated Vehicle Driver

The paper presents some aspects about the dynamic response of the human body subjected to the vertical vibration in the travel inside the auto vehicle. There is a model presented in the specialized literature. This is transformed for the given study because was necessary to realize the vertical vibration along the human body. There are two different studies: using a linear lumped parameter systems seat - human body model; using a nonlinear lumped parameter systems seat-human body model. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Neural network control of seat vibrations of a non-linear full vehicle model using PMSM

In this paper, the dynamic behaviour of a non-linear eight degrees of freedom vehicle model having active suspensions and passenger seat using Permanent Magnet Synchronous Motor (PMSM) controlled by a Neural Network (NN) controller is examined. A robust NN structure is established by using principle design data from the Matlab diagrams of system functions. In the NN structure, Fast Back-Propagation Algorithm (FBA) is employed. The user inputs a set of 16 variables while the output from the NN consists of f₁–f₁₆ non-linear functions. Further, the PMSM controller is also determined using the same NN structure. Various tests of the NN structure demonstrated that the model is able to give highly sensitive outputs for vibration condition, even using a more restricted input data set. The non-linearity occurs due to dry friction on the dampers. The vehicle body and the passenger seat using PMSM are fully controlled at the same time. The time responses of the non-linear vehicle model due to road disturbance and the frequency responses are obtained. Finally, uncontrolled and controlled cases are compared. It is seen that seat vibrations of a non-linear full vehicle model are controlled by a NN-based system with almost zero error between desired and achieved outputs.     

弹性振动的闭环系统

细长体的飞行器在飞行中考虑了既有刚性运动又有弹性振动的运动,由于刚性运动对弹性振动的影响,通过安装在飞行器上面的仪表所测得的角速度作为反馈信号输入到控制器,由控制器输出端输出信号到执行机构来实现反馈控制,把刚性运动飞行器、弹性振动飞行器同时考虑作受控对象,这里我们研究了由刚性飞行器、弹性飞行器和控制器三者形成的闭环系统的弹性振动问题,得到了求闭环系统的频率和振型的公式,设计控制器使得闭环系统渐近稳定的条件和能控性、能观测性的条件。     

Active control of working machines seat suspension aimed at health protection against vibration

The paper presents the model and simulation of passive and active earth-moving machines seat suspension. The object of the simulation is the visco-elastic passive seat suspension with an air-spring, hydraulic shock-absorber and scissors guidance mechanism. Passive seat suspension amplifies the vibration amplitude at low frequency range of excitation signal (the resonance effect). In order to help the working machines operators against vibration, the active system with different control strategies is elaborated. Active system improves significantly the behavior of the seat suspension at low frequency excitation, with the most effectiveness obtained for the resonance frequency. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

汽车车体振动系统的对称性与守恒量研究

用Lie群方法研究汽车车体振动系统的对称性,寻找其存在的守恒量.以汽车车体做上下垂直振动和绕其质心的前后俯仰振动,采用Lagrange函数的方法,构建汽车车体振动系统.以此系统为对象,引入Lie群方法,给出该振动系统的Noether对称性理论与Lie对称性理论;由此推导该汽车系统存在的Noether对称性与Lie对称性,并得到系统相应的的守恒量.该方法对车体振动问题提出了新的对称性解法,同时扩大了Lie群方法的应用范围.     

Dynamical analysis of the rotor system

This paper aims at creating a mathematical model of a bending oscillation rotor system which enables to execute a dynamical analysis of its vibration including the influence of nonlinear bearing characteristics. More specifically, using the finite element method the model of rotating system supported by four hydrodynamic bearings was created. The basic dynamical analysis of the rotor system was performed and the eigenvalues, eigenvectors and stability conditions were evaluated. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Predicting stochastic characteristics of generalized eigenvalues via a novel sensitivity-based probability density evolution method

This paper proposes a novel numerical method for predicting the probability density function of generalized eigenvalues in the mechanical vibration system with consideration of uncertainties in structural parameters. The eigenproblem of structural vibration is presented by first and the sensitivity of generalized eigenvalues with respect to structural parameters can be derived. The probability density evolution method is then developed to capture the probability density function of generalized eigenvalues considering uncertain material properties. Within the proposed method, the probability density evolution equation for the generalized eigenvalue problem is established accounting for the sensitivity of generalized eigenvalues with respect to structural parameters. A new variable which connects generalized eigenvalues to structural parameters is then introduced to simplify the original probability density evolution equation. Next, the simplified probability density evolution equation is solved by using the finite difference method with total variation diminishing schemes. Finally, the probability density function as well as the second-order statistical quantities of generalized eigenvalues can be predicted. Numerical examples demonstrate that the proposed method yields results consistent with Monte-Carlo simulation method within significantly less computation time and the coefficients of variation of uncertain parameters as well as the total number of them have remarkable effects on stochastic characteristics of generalized eigenvalues.     

复合弹性系统边界反馈镇定的Riesz基方法

考虑一个航天器控制实验室实验模型的振动镇定问题。证明了高阶微分线性反馈的闭环系统是一个Riesz系统,即系统存在一列广义本征函数列构成状态空间的Riesz基。从而系统的谱确定增长条件成立。在此过程中,简单的导出了系统本征值的渐近展开式。并因些推论出系统的指数稳定性的条件。     

A holistic finite element and multi-body systems approach for the virtual product development

This article describes the creation of a holistic modeling of a machine tool using a multi-body-systems approach with an integrated flexible body. This lower order model is validated by a detailed finite element model and its eigenvalues are improved by a model-updating algorithm. The improved model is used for investigation of the machine vibration during the cutting process and the prediction of chatter. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A finite-element mechanical contact model based on Mindlin-Reissner shell theory for a three-dimensional human body and garment

Efficient numerical methods for describing a garment’s mechanical behavior during wear have been identified as the key technology for garment simulation. This paper presents a finite-element mechanical contact model based on Mindlin-Reissner shell theory for a three-dimensional human body and garment. In this model, the human body and the garment are meshed as basic contact cells, these contact cells between the human body and the garment are defined as the contact pair to describe the contact relationship, and the mathematical formulation of the finite-element model is defined to describe the strain-stress performance of the three-dimensional human body and garment system. By using the solution given by the computer code and the programs specifically developed, the calculations of the mechanics in the basic cells of the human body and the garment have been able to be carried out. The simulation results show that the model of rationality, a good simulation results and simulation efficiency.     

Research about moving restrictions of cervical spine under the action of mechanical vibrations

The cervical spine is very important human body part, because it sustains the head and it has a higher mobility than the other parts of human spine. The vibration could influence the work performance but also could have a negative influence on human body health. There are many elements, which could be damaged: eyes, ears, brain, mandible, neck's muscle, C1 to C7 vertebras. When the operator is exposed to vibrations for a long time, he can fill a strong pain at the neck. Injuries to the cervical spine are common at the level of the second cervical vertebrae, but neurological injury is uncommon. If it does occur, however, it may cause death or profound disability, including paralysis of the arms or legs. We purpose in this study to develop a biomechanical model for the cervical vertebras and identify the influence of mechanical vibrations on human cervical spine and human head. For this study is necessary to compute the entire moving system of the neck-head. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Integrated measurement system using accelerometers and gyros as peripheral sensors to estimate the motional state of an elastic beam

Integrated navigation devices for vehicle guidance are the most common example of an integrated motion measurement system combining the signals from an inertial measurement unit (IMU consisting of three accelerometers and three gyros) and a GPS receiver with a single antenna. For this, the vehicle is traditionally assumed to be a single rigid body with six motional degrees of freedom to be determined. During periods of low vehicle dynamics the common integrated navigation systems show, however, stability problems. Nevertheless, the stability of the system can be guaranteed by distributing sensors over the vehicle structure. In this case the rigid body assumption has to be expanded to take the distributed sensors and the flexibility of the structure into account. Integrated systems in general are fusing different measuring signals by combining their benefits and blinding out their disadvantages. For instance, gyros and accelerometers are used to obtain reliable signals with a good time resolution. On the other hand, aiding sensors like radar units and strain gauges are known to be long-term accurate. Furthermore, the kernel of such integrated systems consists of an extended Kalman filter that estimates the motion state of the structure. Besides the sensor signals, the basis for the filter is an additional kinematical model of the structure which has to be developed individually. The example of the motion of an elastic beam being considered here is meant to be an approach to obtain motional measurements of a wing of a large airplane during flight. By means of a modal approach, a kinematical model of the beam was developed. This paper will compare integrated systems utilising accelerometers as peripheral sensors with systems using gyros and systems with a combination of both peripheral sensor types. Based on simulation the paper shows this approach, different sensor configurations, and estimated motion results of an elastic beam. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optimisation of pneumatic circuit aimed at improving the vibro-isolation properties of seat suspension

The object of a numerical simulation and optimisation is the seat with a visco-elastic passive suspension, with improved vibro-isolation properties by means the multi-criteria optimisation. Basing on the verified passive seat suspension model, a modification of the pneumatic circuit in order to help the working machines operators against vibration is considered. The root mean square (RMS) acceleration measured at the seat and the maximum relative displacement of the seat suspension are minimised as the chosen vibro-isolation criteria. (© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Analysis of vibration effects on the comfort of intercity bus users by oscillatory model with ten degrees of freedom

The paper analyzes the effects of vibrations on the comfort of intercity bus IK-301 users. Evaluation of vibration effects was carried out according to the criteria set out in the 1997 ISO 2631-1 standard for comfort in public means of transport. Comfort is determined for the space of a driver, passenger in the middle part of the bus and passenger in the rear overhang. Also, the allowable exposure time to vibrations in drivers for the reduced comfort criterion was determined according to the 1978 ISO 2631-1 standard. The bus spatial oscillatory model with ten degrees of freedom was developed for the needs of the analysis. Bus excitation was generated applying the Power Spectral Density of the asphalt-concrete road roughness, as described by the H. Braun model. The allowable vibration exposure time for the driver’s body decreases as the spring stiffness of the driver’s seat suspension system increases. Simulation was performed using the MATLAB software.     

Shape control of piezolaminated thin-walled structures using nonlinear piezoelectric actuators

In the present paper a 2D-shell finite element model is proposed to carry out static analysis of piezolaminated composite shells by incorporating nonlinear constitutive relations in order to describe the electromechanical coupling under strong electric fields. The present shell element has 5 mechanical DOFs and 3 electrical DOFs per node. The developed composite piezolaminated shell element is employed to study the static behavior and shaping of spherical antenna reflector laminated with piezo-patches under both weak and strong electric fields. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Development of a biomechanical model to study the horizontal vibration transmitted from shoulder to head

On daily activity a human operator is exposed to vibration in working environment. So, the human body will react in different way. The problem is how much from the initial signal will be sent to the other parts of the body and how much that motion will be damped along the studied parts. The vibrations in horizontal plane are some unexpected, so the human operator will not take any position to prevent them. In this condition the horizontal vibrations will have the higher effect possible. In this paper, the shoulder, neck and the head are modeled together like a mechanical system with four degree of freedom. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

车桥系统的耦合振动

通过用正弦波形模拟桥面的不平和考虑移动车辆-桥梁间的相互作用,在Euler-Bernoulli梁理论的基础上建立了一种车桥系统的耦合振动模型．利用模态分析法和Runge-Kutta法对模型进行数值求解,获得了车桥系统耦合振动的动态响应和共振曲线．发现车桥耦合振动的共振曲线中存在两个共振区域,一个反映主共振而另一个反映次共振．讨论了桥面不平、桥梁振型和车辆间的相互作用对系统振动的影响．数值结果表明,这些参数对系统振动的影响很大,桥面不平和振型对车桥系统耦合振动的影响不能忽略,设计车速应该远离临界车速．     

随机激励下四自由度车辆-道路耦合系统动力分析

采用四自由度车辆模型,以 Gauss平稳随机过程模拟路面的不平整度,编制程序得到不同路面等级下的不平整度序列;并将车辆和道路看作一个相互作用的整体系统,建立了车辆 道路耦合系统的动力平衡方程.在对车辆施加随机激励时,为了简化分析过程,避开以往研究中使用随机振动理论求解动轮胎力的复杂性,将得到的路面不平整度序列,直接以向量的形式输入到所建立的动力平衡方程中.基于增量形式的Newmark-β法开发了一个MATLAB程序对该方程进行求解.并对所提出的理论模型进行了试验验证,证明了模型的可靠性.随后,通过一个实例,分析了车速变化、路面等级变化对车辆动荷载系数和车体垂向加速度的影响.最后,对不同路基刚度对车辆振动特性的影响规律进行了探讨.     

Numerical and experimental investigation on stochastic dynamic load of a heavy duty vehicle

Numerical simulation and field test are used to investigate tire dynamic load. Based on multi-body dynamics theory, a nonlinear virtual prototype model of heavy duty vehicle (DFL1250A9) is modeled. The geometric structural parameters of the vehicle system, the nonlinear characteristics of shock absorber and leaf springs are precisely described. The dynamic model is validated by testing the data, including vertical acceleration of driver seat, front wheel, intermediate wheel and rear wheel axle head. The agreement between the response of the virtual vehicle model and the measurements on the test vehicle is satisfactory. Using the reliable model, the effects of vehicle speed, load, road surface roughness and tire stiffness on tire dynamic load and dynamic load coefficient (DLC) are discussed. The results demonstrate that the proposed model can offer efficient and realistic simulation for stochastic dynamic loads, so as to investigate vehicle road-friendliness.