Longitudinal vehicle dynamics control for improved vehicle safety

The aim is to investigate the improvements in vehicle safety that can be achieved by limiting the vehicle speed based on GPS path information. The control strategy is aimed at reducing vehicle speed before a potentially dangerous situation is reached, in contrast with widely used stability control systems that only react once loss of control by the driver is imminent. An MSC.ADAMS/View simulation model of an off-road test vehicle was developed and validated experimentally. A longitudinal speed control system was developed by generating a reference speed based on the path information. This reference speed was formulated by taking into account the vehicle’s limits due to lateral acceleration, combined lateral and longitudinal acceleration and the vehicle’s performance capabilities. The model was used to evaluate the performance of the control system on various tracks. The control system was implemented on the test vehicle and the performance was evaluated by conducting field tests. Results of the field tests indicated that the control system limited the acceleration vector of the vehicle’s centre of gravity to prescribed limits, as predicted by the simulations, thereby decreasing the possibility of accidents caused by rollover or loss of directional control due to entering curves at inappropriately high speeds.     

Turbulent flow dynamics caused by a truncated cylinder

The turbulent flow field around a quite simple geometry has been analysed in detail based on a snapshot database taken from numerical simulation. Here, emphasis is placed on the dominant coherent motion and the flow dynamics in the separated wake. The method-based analysis is performed using POD, filtering and phase-averaging. The results obtained show a highly intermittent flow topology, which reveals different (at least three) recurring vortex arrangements, but with considerably stochastic character. Corresponding frequencies, the periodicity as well as correlation and interaction of predominant vortex motions are discussed. The methods employed are not limited to the configuration exemplarily chosen.     

Resonant dynamics in strongly nonlinear systems

This work considers the effect of resonances in systems in which the two resonant frequencies are allowed to slowly change, depending on the state of the system. A strongly nonlinear system is introduced that allows for exact solutions. This system is then coupled to a second component, and through the method of averaging, a reduced-order model is developed that approximates the dynamical behavior near a 1:1 resonance between the two components. The resulting reduced system is studied using bifurcation theory and Melnikov analysis to obtain predictions of the near-resonant dynamics. Finally, these predictions are compared to numerical simulations of the original equations. Two main points appear: (i) for nonlinear systems, the period–amplitude dependence plays an important role in the evolution of the system, and (ii) the coordinates identified within the reduced system allow for the qualitative structure of the original equations to appear.     

An instrumented vehicle for offroad dynamics testing

The paper presents an instrumented vehicle that was equipped with measuring systems to perform complete dynamics tests, especially in off-road conditions. The equipment consists of four wheel dynamometers, a steering robot, and a differential GPS system together with an inertial platform, a non-contact vehicle speed sensor, and an on-board computer with software to control the devices and collect experimental data. The four wheel dynamometers measure six elements; based on strain gage force transducers, it measures three orthogonal forces and three moments. The steering robot can control the steering wheel of the vehicle at a variety of excitation modes; it can carry out typical vehicle dynamics tests (ISO 7401, ISO 4138, ISO/TR3888, etc.) as well as custom engineered tests at a wide range of setting parameters (steer angle rate up to 1600 deg/s). The differential GPS system gives true time vehicle kinematics data (velocities, accelerations, angles, etc.) at 10-ns sample rate and 20-mm accuracy. The base vehicle, a Suzuki Vitara 4 × 4, required no special modifications or changes to install the measuring equipment. The paper also describes typical tests performed with the use of the instrumented vehicle together with sample results.     

On path-independent integrals in three-dimensional nonlinear fracture dynamics

This paper deals with the path-independent integrals in non-linear three-dimensional fracture dynamics.Both the nonli-near elastic case and the elastic-plastic case are considered,and some path-independent integrals have been worked out.Forexplaining the physical meaning of these integrals,a speci-men with plane notch is considered,and the relation betweenthe integral and dynamical crack extension force is establish-ed.Thus.such integrals may serve as a fracture criterionin nonlinear fracture dynamics.     

Electromechanical coupled nonlinear dynamics for microbeams

In this paper, an electromechanical coupled nonlinear dynamic equation of a microbeam under an electrostatic force is presented. Using the nonlinear dynamic equations and perturbation method, we investigated nonlinear free vibrations, forced responses far from and near to natural frequency, respectively. Nonlinear natural frequencies and vibrating amplitudes of the electromechanical coupled microbeam are dependent on the mechanical and electric parameters. Compared with linear forced responses, the obvious shift of the mean dynamic response occurs. Under certain condition, the jump phenomenon will occur. The studies can be used to design parameters of the microbeam and remove undesirable dynamic behavior such as jump phenomenon, etc.     

Bifurcation of piecewise-linear nonlinear vibration system of vehicle suspension

A kinetic model of the piecewise-linear nonlinear suspension system that consists of a dominant spring and an assistant spring is established. Bifurcation of the resonance solution to a suspension system with two degrees of freedom is investigated with the singularity theory. Transition sets of the system and 40 groups of bifurcation diagrams are obtained. The local bifurcation is found, and shows the overall character- istics of bifurcation. Based on the. relationship between parameters and the topological bifurcation solutions, motion characteristics with different parameters are obtained. The results provides a theoretical basis for the optimal control of vehicle suspension system parameters.     

Multi-pulse orbits and chaotic dynamics in a nonlinear forced dynamics of suspended cables

The global bifurcations in mode of a nonlinear forced dynamics of suspended cables are investigated with the case of the 1:1 internal resonance. After determining the equations of motion in a suitable form, the energy phase method proposed by Haller and Wiggins is employed to show the existence of the Silnikov-type multi-pulse orbits homoclinic to certain invariant sets for the two cases of Hamiltonian and dissipative perturbation. Furthermore, some complex chaos behaviors are revealed for this class of systems.     

Propagation dynamics of tripole breathers in nonlocal nonlinear media

Nonlinear Dynamics - We demonstrate the propagation dynamics of optical breathers in nonlinear media with a spatial nonlocality, which is governed by the nonlocal nonlinear Schrödinger...     

Application of Morse potential in nonlinear dynamics of microtubules

Nonlinear Dynamics - We here present a model of nonlinear dynamics of microtubules using modified extended tanh-function method as a mathematical tool. Interaction between neighbouring dimers...     

Fractional nonlinear dynamics of learning with memory

Nonlinear Dynamics - In this paper, we consider generalization of the Lucas model of learning (learning-by-doing) that is described in the paper Robert E. Lucas (Econometrica 61(2):251–272,...     

非线性动力学方程的一种级数解

本文针对n维未知向量v的一阶微分议程v=Hv f(v,t)进行求解,其中Hv和f(v,t)分别是右端项的线性剂次部分和非线性部分,首先,将非线性部分f(v,t)在所论时刻tk处展成t-tk=τ的泰勒级数,并通过求原函数的方法直接给出每一项的积分,从而获得了待求微分方程在级数形式下的闭合争,它的具有不同精度的各次静似解可表示成τ的分段解析函数,便于研究非线性动力学行为与其物理参数的依赖关系。本文还用算例验证了各次近似解之间的数值关系,并和解析解等作了比较。     

Dissipative dynamics of geometrically nonlinear Bernoulli-Euler beams

We consider nonlinear dissipative vibrations of the Bernoulli-Euler beam. We find that, under the action of a transverse alternating load, the vibrations may become chaotic. We study a scenario in which harmonic vibrations become chaotic, namely, the Feigenbaum scenario, and find the Feigenbaumconstant. In the present paper, we paymuch attention to the reliability of the results obtained. To this end, we use two methods, the finite difference O(h ²) method and the finite element method in the Bubnov-Galerkin form, and verify the convergence of these methods.     

Linear and nonlinear dynamics of reciprocating engines

In the first part of this study, dynamic models of single- and multi-cylinder reciprocating machines are presented, which may involve torsional flexibility in the crankshaft. These models take into account the dependence of the engine moment of inertia on the crankshaft rotation. In addition, both the driving and the resisting moments are expressed as functions of the crankshaft motion. This leads to dynamic models with equations of motion appearing in a strongly nonlinear form. Initially, an approximate analytical solution is presented for a linearized version of the equations of motion, by applying a suitable asymptotic method. This provides valuable insight into some aspects of the system dynamics. In the second part, numerical results are presented for linear and nonlinear engine models by applying appropriate methodologies, leading to direct determination of complete branches of steady-state response. These results illustrate the effect of the system parameters on its dynamics. Finally, some results are also presented in an effort to investigate the effect of engine misfire.     

Unscented Kalman filtering for nonlinear structural dynamics

Joint estimation of unknown model parameters and unobserved state components for stochastic, nonlinear dynamic systems is customarily pursued via the extended Kalman filter (EKF). However, in the presence of severe nonlinearities in the equations governing system evolution, the EKF can become unstable and accuracy of the estimates gets poor. To improve the results, in this paper we account for recent developments in the field of statistical linearization and propose an unscented Kalman filtering procedure. In the case of softening single degree-of-freedom structural systems, we show that the performance of the unscented Kalman filter (UKF), in terms of state tracking and model calibration, is significantly superior to that of the EKF.     

Anomalous dynamics response of nonlinear elastic bar

ＩｎｔｒｏｄｕｃｔｉｏｎＩｎｒｅｓｅｎｔｙｅａｒｓ,ｔｈｅｃｈａｏｔｉｃｂｅｈａｖｉｏｒｏｆｂｅａｍｓｓｕｂｊｅｃｔｅｄｔｏｐｅｒｉｏｄｉｃｌｏａｄｂｒｉｎｇｓｍｏｒｅａｎｄｍｏｒｅｓｃｈｏｌａｒｓ’ｉｎｔｅｒｅｓｔｓ.Ｉｎ 1 983 ,ＦＣＭｏｏｎｅｔａｌ.[1]ｓｔｕｄｉｅｄｔｈｅｃｈａｏｔｉｃｍｏｔｉｏｎｓｏｆｂｅａｍｓｉｎｎｏｎｌｉｎｅａｒｂｏｕｎｄａｒｙｃｏｎｄｉｔｉｏｎｓ.Ｉｎ 1 994 ,Ｓ .ＡｎａｎｔｈａＲａｍｕａｎｄＴＳＳａｎｋａｒｅｔａｌ.[2 ]ａｎａｌｙｚｅｄｂｉｆｕｒｃａｔｉｏｎａｎｄＣａｔａ…     

An equivalent polynomial approximation technique in nonlinear structural dynamics

Summary A new technique is proposed to obtain an approximate probability density for the response of a general nonlinear system under Gaussian white noise excitations. In this new technique, the original nonlinear system is replaced by another equivalent nonlinear system, structured by the polynomial formula, for which the exact solution of stationary probability density function is obtainable. Since the equivalent nonlinear system structured in this paper originates directly from certain classes of real nonlinear mechanical systems, the technique is applied to some very challenging nonlinear systems in order to show its power and efficiency. The calculated results show that applying the technique presented here can yield exact stationary solutions for the nonlinear oscillators. This is obtained by using an energy-dependent system, and for a nonlinearity of a more complex type. A more accurate approximate solution is then available, and is compared with the approximation. Application of the technique is illustrated by examples.     

State reconstruction in a nonlinear vehicle suspension system using deep neural networks

Nonlinear Dynamics - In this paper, the optimal formation and optimal matching of a multi-robot system are investigated with a projection-based algorithm designed to get the optimal formation...