Juan Chen

A New Control Method in pH Neutralization Process

PH neutralization process is composed of a complex and multivariable nonlinear coupling. This paper combines the fuzzy control and sliding mode control, and studying on the control of pH value and liquid level of pH neutralization process. On one hand, this approach simplifies the fuzzy control, on the other hand, it adjusts the universe of fuzzy control system by quantification scale factor changing adaptively and makes system control signals soften and reduces the chattering of sliding mode control. Here, quantification scale factor improves control accuracy of systems. The simulation results show that even a major change in operating point, the systems still have good anti-disturbance and strong robustness.

Research on global and local stability of continuous welded rail based on finite element analysis and discrete short-time Fourier transform

The evaluation of the stability of continuous welded rail (CWR) is a major area of research activity. In this paper, a method is proposed that uses finite element analysis and discrete short-time Fourier transform methods to evaluate the global and local stabilities of in-service CWR on the Baotou–Xi’an line in the People’s Republic of China. A local stability evaluation criterion for the rail and a global standard deviation for the thermal stress fluctuation in the CWR are proposed. The global stability of a CWR that consists of two rails is taken to be that of the rail with the largest thermal stress fluctuation, whereas for a single rail, the fluctuation state of the local zone with the largest thermal stress fluctuation is used as the criterion.

Application of a combined metal magnetic memory–magnetic Barkhausen noise technique for on-site detection of the stress-free temperature of a continuous welded rail

A change in the actual stress-free temperature of a continuous welded rail (CWR) has a major influence on its strength and stability. Therefore, it is necessary to appropriately select the stress-free temperature in each region when laying CWR. However, due to the difficulty of performing nondestructive testing, the possible application of a combined metal magnetic memory-magnetic Barkhausen noise (MMM-MBN) technique is explored in this paper and its features, such as hardware circuit, control algorithm and control system, are investigated. Also, a stability model and its associated formula for CWR are established. Additionally, formulas for the stress-free temperature of CWR and methods for its on-site detection and implementation are established based on the thermal stress and the temperature of the CWR. A support vector machine algorithm is used to calculate the thermal stress in a CWR, and the value detected using an in-house built measurement system is compared with the theoretically calculated value; a relative error of less than 4.78% is obtained.

Model approximate method of complex system

During the internal model control of multivariate multiple time delay system, process model is very important in the design of controller, but complicated mathematical model is often encountered in decoupled multivariable multiple time delay system and needs to be reduced order. So this paper proposes a low order identification structure and an optimization method for model approximation of the complex model containing the time delay and non-minimum phase parts. In this paper, with the adoption of Pade approximation, a suboptimal approximate algorithm is used for the model approximation and model identification. The integral square error index and the frequency-domain integral square error index, as well as the integral time absolute error index is used to evaluate the approximate model comprehensively. Simulation results show that using the proposed model identification structure and adopting the suboptimal approximate algorithm to deal with this kind of approximation, that can get an approximate model that well reveals the dynamic characteristics of system and has a high approximation precision.

Testing of Hardness on Long Rail Welded Joint by Means of Magnetic Barkhausen Noise Technique

The experiment shows that the Magnetic Barkhausen Noise (MBN) signal strongly depends on the elastic deformation, heat treatment state of surface and microstructure of the material, etc. Using the MBN technology that rely on the material characteristics, MBN can be used for testing the surface hardness of 60kg/m U74 seamless rail made by China Harbin welded rail plant. And the testing result obtained by the MBN method is consistent with the results obtained by the Brinell hardness (HB) method. Consequently, this non-destructive testing technique will have a strong life and an extensive market.

The Research on the Ultrasonic Focusing and TR Thickness Test Technology

A TR and ultrasonic focusing wheel probe is designed for some special engineering testing item. Ultrasonic TR thickness testing and focusing detection can be carried out without coupling medium. With the testing system and the probe set on a control machine car, aligned and marginal testing for steel plates quality and the thickness testing of corroded pipe wall can be accomplished by dry couple method. The processing method of detection signal and the design of peripheral circuit are also introduced in this paper.

Filter time constant self-adjusting internal model control based on variable domain fuzzy control for time-delay uncertain systems

Aiming at industrial processes with large time-delay, this paper presents a filter time constant λ self-adjusting internal model control (IMC) based on variable domain fuzzy control. A modified variable domain fuzzy control method is proposed on the basis of quantitative factor. Comparing with traditional fuzzy control, simulation results show that the method proposed can improve dynamic quality and robustness of process. Meanwhile, the method provides good performance when mismatch exits between model and actual process.