Investigation on dynamics of a three-directional coupled vehicle-road system

When a vehicle is braking or turning, the longitudinal or lateral tire forces increase greatly and it is necessary to consider the effects of vertical, longitudinal and lateral tire forces on vehicle and road dynamics. This work aims to propose a three-directional coupled vehicle-road system for revealing the properties of three-directional (3D) interaction between vehicle and road. A 23-DOF full-body heavy vehicle model considering the nonlinearity of suspension damping and tire stiffness is built, and a double-layer rectangular thin plate on viscoelastic foundation with four simply supported boundaries is employed to model the road. The equations of motion of vehicle and road, and the 3D tire forces connecting the vehicle and road are formulated. The responses of 3D coupled, vertical coupled and uncoupled vehicle-road model are compared in four maneuver conditions and the effects of parameters on 3D vehicle-road interaction are discussed. It is found that both the 3D coupled model and the vertical coupled model are good enough to predict vehicle responses accurately, but the 3D coupled model is the most suitable for calculating road responses accurately. During the maneuver of sharp steering or emergency braking, or when a vehicle runs on a road with small surface roughness and big adhesion coefficient, the role of 3D vehicle-road interaction becomes too important to be neglected

Improved bacterial foraging optimization for structural damage identification of bridge erecting machine

Aiming at structure damage characteristics of bridge erecting machine, a vibration-based identification model of structural damage acted as a constrained problem is established. In view of the crack damage, the natural frequency of vibration signal and modal assurance criterion is as the index of damage detection, and then an improved bacterial foraging optimization (NBFO) based on the chemotaxis strategy with normal distribution is proposed, meanwhile it is applied to optimizing the identification model of structural damage. Finally using the girder of TLJ900 bridge erecting machine as an example, the simulation results show that the proposed method can more accurately judge the damage position and degree of structure than its counterparts

RVM-based adaboost scheme for stator interturn faults of the induction motor

This paper presents an AdaBoost method based on RVM (Relevance Vector Machine) to detect and locate an interturn short circuit fault in the stator windings of IM (Induction Machine). This method is achieved through constructing an Adaboost combined with a weak RVM multiclassifier based on a binary tree, and the fault features are extracted from the three phase shifts between the line current and the phase voltage of IM by establishing a global stator faulty model. The simulation results show that, compared with other competitors, the proposed method has a higher precision and a stronger generalization capability, and it can accurately detect and locate an interturn short circuit fault, thus demonstrating the effectiveness of the proposed method

Dynamical analysis of fractional-order Mathieu equation

The dynamical characteristics of Mathieu equation with fractional-order derivative is analytically studied by the Lindstedt-Poincare method and the multiple-scale method. The stability boundaries and the corresponding periodic solutions on these boundaries for the constant stiffness δ0=n2 (n = 0, 1, 2, …), are analytically obtained. The effects of the fractional-order parameters on the stability boundaries and the corresponding periodic solutions, including the fractional coefficient and the fractional order, are characterized by the equivalent linear damping coefficient (ELDC) and the equivalent linear stiffness coefficient (ELSC). The comparisons between the transition curves on the boundaries obtained by the approximate analytical solution and the numerical method verify the correctness and satisfactory precision of the analytical solution. The following analysis is focused on the effects of the fractional parameters on the stability boundaries located in the δ-ε plane. It is found that the increase of the fractional order p could make the ELDC larger and ELSC smaller, which could result into the rightwards and upwards moving of the stability boundaries simultaneously. It could also be concluded the increase of the fractional coefficient K1 would make the ELDC and ELSC larger, which could move the transition curves to the left and upwards at the same time. These results are very helpful to design, analyze or control this kind of system, and could present beneficial reference to the similar fractional-order system

A revised averaging method and general forms of approximate solution for nonlinear oscillator with only polynomial-type displacement nonlinearity

In this paper a revised averaging method is presented, that does not need the detuning factor in the solving procedure. Comparison with the traditional averaging method shows that it has the similar solving procedure and the same result as the primary resonance of the traditional averaging method. Then the nonlinear oscillator with only polynomial-type displacement nonlinearity is studied, and the general forms of the first-order approximate solution by this revised averaging method, and by the traditional averaging method for the super-harmonic resonance and sub-harmonic resonance are established. At last, the Duffing oscillator is investigated as an example, and the comparison of the analytical and numerical results proves the validity and simplicity of the presented method

Effect of fractional-order PID controller with acceleration feedback on a linear single degree-of-freedom oscillator

A linear single degree-of-freedom (SDOF) oscillator with fractional-order PID controller of acceleration feedback is investigated by the averaging method, and the approximately analytical solution is obtained. Moreover, the numerical solution of the system is obtained by the step-down order method and the power series method progressively. The effects of the parameters in fractional-order PID controller on the dynamical properties are characterized by some new equivalent parameters. The proportional component of fractional-order PID controller is characterized in the form of equivalent mass. The integral component of fractional-order PID controller is denoted in the form of the equivalent linear damping and equivalent mass. The differential component of fractional-order PID controller is denoted in the form of the equivalent linear negative damping and equivalent mass. Those equivalent parameters could distinctly illustrate the effects of the parameters in fractional PID controller on the dynamical response. A comparison between the analytical solution with the numerical results is made, and their satisfactory agreement verifies the correctness of the approximately analytical results. The effects of the parameters in fractional-order PID controller on control performance are further analyzed by some performance parameters of the time response. Finally, the robustness of the fractional-order PID controller based on acceleration feedback is demonstrated through the control of a SDOF quarter vehicle suspension model

Locomotive drive system fault diagnosis based on dynamic self-adaptive blind source separation

Drive system is one of most important key equipment to guarantee safe and stable operation in locomotive. With time variation, unpredictability and nonstationary, fault source of drive system is not obtained by traditional fault diagnosis method. Blind source separation is a kind of method on source signals separation under transmission channel unknown instance. The method of Blind source separation based on variable metric empirical mode decomposition is proposed. Intrinsic mode function is built, redundancy factors are reduced, and recurrent neural network is used to adaptive blind separation. The method is verified by data analysis of on-line measuring. The results show that separation efficiency is improved and unaffected with iteration time in the process of fault information separation, which will be better for further fundamental research and provide technique support for the locomotive

Subharmonic Resonance of Van Der Pol Oscillator with Fractional-Order Derivative

The subharmonic resonance of van der Pol (VDP) oscillator with fractional-order derivative is studied by the averaging method. At first, the first-order approximate solutions are obtained by the averaging method. Then the definitions of equivalent linear damping coefficient (ELDC) and equivalent linear stiffness coefficient (ELSC) for subharmonic resonance are established, and the effects of the fractional-order parameters on the ELDC, the ELSC, and the dynamical characteristics of system are also analysed. Moreover, the amplitude-frequency equation and phase-frequency equation of steady-state solution for subharmonic resonance are established. The corresponding stability condition is presented based on Lyapunov theory, and the existence condition for subharmonic resonance (ECSR) is also obtained. At last, the comparisons of the fractional-order and the traditional integer-order VDP oscillator are fulfilled by the numerical simulation. The effects of the parameters in fractional-order derivative on the steady-state amplitude, the amplitude-frequency curves, and the system stability are also studied

Effect of fractional-order PID controller with acceleration feedback on a linear single degree-of-freedom oscillator

A linear single degree-of-freedom (SDOF) oscillator with fractional-order PID controller of acceleration feedback is investigated by the averaging method, and the approximately analytical solution is obtained. Moreover, the numerical solution of the system is obtained by the step-down order method and the power series method progressively. The effects of the parameters in fractional-order PID controller on the dynamical properties are characterized by some new equivalent parameters. The proportional component of fractional-order PID controller is characterized in the form of equivalent mass. The integral component of fractional-order PID controller is denoted in the form of the equivalent linear damping and equivalent mass. The differential component of fractional-order PID controller is denoted in the form of the equivalent linear negative damping and equivalent mass. Those equivalent parameters could distinctly illustrate the effects of the parameters in fractional PID controller on the dynamical response. A comparison between the analytical solution with the numerical results is made, and their satisfactory agreement verifies the correctness of the approximately analytical results. The effects of the parameters in fractional-order PID controller on control performance are further analyzed by some performance parameters of the time response. Finally, the robustness of the fractional-order PID controller based on acceleration feedback is demonstrated through the control of a SDOF quarter vehicle suspension model