Chaoyang Guo

Semi-active H∞ control of high-speed railway vehicle suspension with magnetorheological dampers

In this paper, semi-active H∞ control with magnetorheological (MR) dampers for railway vehicle suspension systems to improve the lateral ride quality is investigated. The proposed semi-active controller is composed of a H∞ controller as the system controller and an adaptive neuro-fuzzy inference system (ANFIS) inverse MR damper model as the damper controller. First, a 17-degree-of-freedom model for a full-scale railway vehicle is developed and the random track irregularities are modelled. Then a modified Bouc–Wen model is built to characterise the forward dynamic characteristics of the MR damper and an inverse MR damper model is built with the ANFIS technique. Furthermore, a H∞ controller composed of a yaw motion controller and a rolling pendulum motion (lateral motion+roll motion) controller is established. By integrating the H∞ controller with the ANFIS inverse model, a semi-active H∞ controller for the railway vehicle is finally proposed. Simulation results indicate that the proposed semi-active suspension system possesses better attenuation ability for the vibrations of the car body than the passive suspension system.

The investigation on the nonlinearity of plasticine-like magnetorheological material under oscillatory shear rheometry

To fully understand the structure dependent mechanical property, the harmonic strain loadings were applied to the magnetorheological plastomer (MRP) to study their dynamic properties. Under different test conditions, nonlinearity which was induced by strain amplitude and driving frequency was generated. In order to investigate the mechanism of nonlinearity, a facile and effective strategy by analyzing the response stress and actuating strain within an oscillatory cycle was introduced. In addition, the microstructures of isotropic and anisotropic MRP were observed and the time dependence of dynamic properties for MRP (from isotropic to anisotropic) under an 800 mT magnetic field was also investigated, which were helpful to further understand the structure dependent dynamic properties depending on actuating strain amplitude.

Squeeze behavior of magnetorheological fluids under constant volume and uniform magnetic field

In this work the experimental investigation of magnetorheological fluids in squeeze mode has been carried out under constant volume with a self-developed device. The magnetorheological fluids were forced to move in all directions in a horizontal plane as the two flat surfaces came together. A pair of Helmholtz coils was used to generate a uniform magnetic field in the compression gap. The normal forces within the gap were systematically studied for different magnetic field, squeeze velocity, particle concentration, viscosity of carrier fluid and initial gap distance. Two regions of behavior were obtained from the normal force versus gap distance curve: elastic deformation and plastic flow. A power law fitting was appropriate for the relation between the normal force and the gap in the plastic flow. The index of the power law was smaller than that predicted by the continuum theory, possibly due to the squeeze strengthening effect and the sealing effect. (Some figures may appear in colour only in the online journal)

Compression behaviors of magnetorheological fluids under nonuniform magnetic field

This work is concerned with an experimental and theoretical study on compression properties of magnetorheological fluids under the nonuniform field. Experimental tests of unidirectional monotonic compression were firstly carried out under constant area operation using a commercial plate–plate magneto-rheometer where the magnetic field radial distribution was nonuniform. Normal forces increased with decreasing of the gap distance, and two regions were found through the normal force versus gap distance curves: elastic deformation and plastic flow. High normal forces could be obtained in the case of high magnetic field, high compression velocity, low initial gap distance, high volume fraction, and high medium viscosity. In the plastic flow region, the normal force with the gap distance could be fitted with a power law relation

Inverse neuro-fuzzy MR damper model and its application in vibration control of vehicle suspension system

F_{\textrm {N}} \propto h^n

Oscillatory normal forces of magnetorheological fluids

, and the index n was around well in the range (−3, −2). Taking nonuniform magnetic field into account, the theoretical modeling in the plastic flow was then developed to calculate the normal force under compression based on the continuum media theory. Compared to the uniform field, there existed a magnetic field gradient-induced normal force under nonuniform field. Considering the sealing and squeeze strengthening effect, the gap distance-dependent shear yield stress was proposed, and a good correspondence between the theoretical and experimental results was obtained.

An experimental investigation on the normal force behavior of magnetorheological suspensions

In this paper, a magneto-rheological (MR) damper-based semi-active controller for vehicle suspension is developed. This system consists of a linear quadratic Gauss (LQG) controller as the system controller and an adaptive neuro-fuzzy inference system (ANFIS) inverse model as the damper controller. First, a modified Bouc–Wen model is proposed to characterise the forward dynamic characteristics of the MR damper based on the experimental data. Then, an inverse MR damper model is built using ANFIS technique to determine the input current so as to gain the desired damping force. Finally, a quarter-car suspension model together with the MR damper is set up, and a semi-active controller composed of the LQG controller and the ANFIS inverse model is designed. Simulation results demonstrate that the desired force can be accurately tracked using the ANFIS technique and the semi-active controller can achieve competitive performance as that of active suspension.

Twin-tube- and bypass-containing magneto-rheological damper for use in railway vehicles

The normal forces of magnetorheological fluids were investigated by a commercial magneto-rheometer with plate–plate geometry. Based on the analysis, it was found that the oscillatory normal forces can be achieved both under steady shear and oscillatory shear. The oscillatory normal forces obtained under steady shear developed from the nonparallelism of the testing plates, while the oscillatory normal forces under oscillatory shear mainly arose from the microstructure revolution of magnetorheological fluids. Finally, a dynamic simulation was utilized to analyze this oscillatory shear normal force and the formation mechanism was discussed.

Poly(methyl methacrylate)‐coated carbonyl iron particles and their magnetorheological characteristics

In this work the normal force behavior of magnetorheological suspensions are systematically investigated. Four magnetorheological suspensions with different volume fractions (10%, 20%, 30%, and 40%) are prepared and both the static and dynamic normal forces of the samples are measured by using a commercial plate-plate magneto-rheometer under constant and sweeping magnetic field. A positive normal force will be generated when the applied magnetic field exceeds a critical value. The normal force firstly increases with the increasing of magnetic field strength and then reaches a saturation value. A magnetization model is utilized to represent this mechanism. The oscillatory dynamic normal forces with time are studied and their changes with shear rates are dependent on the volume fraction. Comparisons between static and dynamic normal forces show that the differences between them are dependent on the volume fraction and magnetic filed. The temperature effect on the normal force is studied and under high magnetic field the normal force would increase slightly with the increasing of temperature.

Magnetic-Field-Induced Normal Force of Magnetorheological Elastomer under Compression Status

A 9-kN magneto-rheological (MR) damper for lateral suspension control of a railway vehicle is created in this paper. The twin-tube style is adopted in order to obtain a long damper stroke and guarantee the symmetry of the output damping force. A bypass MR valve with a radial flow path is utilised to control the generated damping force. Three-dimensional finite element analysis studies are performed to determine the magnetic field strength inside the MR valve region. The MR damper is mathematically modelled for the situation of a unidirectional fluid flow in the chamber and valve. The test results indicate that the MR damper can produce a considerable range of dynamic force and can operate as a fail-safe device. Sedimentation is detected in the damper; however, the response time is acceptable for real-world deployment.