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The hoist is an important equipment in the mine pit. Since the containers are lifted or lowered with flexible steel wire ropes, there are shocks and vibrations during operation, especially in the emergency braking stage, the shocks and vibration will be more severe. Mine hoist is a complex system; therefore, it is difficult to obtain all its dynamics information only by investigating the flexible hoisting subsystem or hydraulic brake subsystem. Therefore, it is very necessary to establish an accurate model to predict these characteristics of the hoist, this will provide useful tools for hoist design and maintenance. Therefore, a joint modeling methodology is proposed and implemented in this paper. A hoisting system model considering the non-linear factors such as contact characteristics and flexibility was established in RecurDyn. The hydraulic braking system model and control system model were established in AMESim, and the co-simulation model was constructed by the interface module. In this co-simulation model, not only the flexible hoisting subsystem and hydraulic brake subsystem are included, but also the coupling effect of subsystems is considered. Finally, taking the lifting condition as an example, execute emergency braking research on the hoisting system under experiment, mathematical model, and co-simulation model, respectively. Comparing the co-simulation model with the mathematical dynamics model, and the experimental test results, research indicates that the joint simulation model of coupled hoisting system and hydraulic braking system can effectively reflect the dynamic characteristics of the actual hoisting system. It provides an effective tool for hoist design, optimization, performance analysis, and operating condition simulation. In addition, the methods and techniques used in the co-simulation modeling procedure are portable. Therefore, the paper is of significance for the mine hoist.

Mine hoist is a typical flexible lifting system. Due to the cable flexibility, the system is prone to severe shocks and even slippage during emergency braking. To establish a safe emergency braking operation for mine hoist, retarded velocity should be less than the limit deceleration value. The simplified mathematical model shows that the system dynamic response along the longitudinal axis of the wire rope (longitudinal dynamics) is a typical second-order underdamped one. Due to the inherent characteristics of the flexible lifting system, the longitudinal dynamic response under slippage condition exhibits the following characteristics: the response curve deviates from the input signal, that is, the retarded velocities of cable and pulley at their contact points are no longer equal. Based on this finding, deceleration deviation coefficient is defined to normalize the longitudinal response curves, which can help us to determine the extent to which the output signal deviates from the input one; and the sudden increase in the deceleration deviation coefficient is considered as an indicator of rope slippage during emergency braking. The proposed scheme is verified and evaluated by means of simulation model. Subsequent results indicate that the limit deceleration valves obtained by the proposed approach have the same trend and magnitude as those obtained by conventional one, which illustrates that the proposed methodology is feasible. The advantage of the proposed approach is that the solution for each set of operating parameter is unique and certain. As for the conventional approach, the solution is not unique because of the introduction of safety factor, which will cause some trouble to the user. In subsequent work, a test bench will be set up to verify and optimize the proposed scheme.

Rolling element bearings constitute the key parts on rotating machinery, and their fault diagnosis is of great importance. In many real bearing fault diagnosis applications, the number of fault data is much less than the number of normal data, i.e. the data are imbalanced. Many traditional diagnosis methods will get low accuracy because they have a natural tendency to favor the majority class by assuming balanced class distribution or equal misclassification cost. To deal with imbalanced data, in this article, a novel two-step fault diagnosis framework is proposed to diagnose the status of rolling element bearings. Our proposed framework consists of two steps for fault diagnosis, where Step 1 makes use of weighted extreme learning machine in an effort to classify the normal or abnormal categories, and Step 2 further diagnoses the underlying anomaly in detail by using preliminary extreme learning machine. In addition, gravitational search algorithm is applied to further extract the significant features and determine the optimal parameters of the weighted extreme learning machine and extreme learning machine classifiers. The effectiveness of our proposed approach is testified on the raw data collected from the rolling element bearing experiments conducted in our Institute, and the empirical results show that our approach is really fast and can achieve the diagnosis accuracies more than 96%.

This paper introduced a process to prepare novel Cu-Cu2O/TiO2 two-layer nanocomposite films with Cu-Cu2O mixture layers grown on TiO2 films prepared by a magnetron sputtering method. The structure, the morphology and optical properties of the films were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), fluorescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectroscopy (DRS). XRD patterns indicate that the Cu-Cu2O mixture layer does not change the crystalline phase of TiO2. XPS results show that the presence of Cu restrains the oxidation of Cu2O surface for Cu-Cu2O/TiO2 layer. SEM analysis reveals that the well crystallized Cu-Cu2O mixture nanoparticles are dispersed uniformly on the surface of TiO2. Owing to UV-vis diffuse reflectance spectroscopy, an red shift of the extended absorption edge of Cu-Cu2O/TiO2 takes place. PL spectra confirm the presence of Cu which reduces the recombination rate of exited electron-hole. Photocatalytic experiments demonstrate that compared with pure Cu2O/TiO2, the as-prepared Cu-Cu2O/TiO2-8 shows greater efficiency in photogenerated carriers and a significantly improved photocatalytic performance. In addition the reason for improvement in photocatalytic activity of the Cu-Cu2O/TiO2-8 films was also discussed.

11th International Fluid Power Conference, 11. IFK, Aachen, Germany, 19 Mar 2018 - 21 Mar 2018; Aachen : [Mainz], 346-357 (2018)., Published by [Mainz], Aachen

Flow control valves are extensively used to control the motion of hydraulic actuators in industry. In this paper, a two-stage proportional flow control valve with pilot digital pressure compensator is presented. The proposed valve is composed of two pressure sensors, a proportional pilot valve, a Valvistor poppet valve (main stage), and an electronic controller. The pressure drop across the pilot valve metering orifice is detected by two pressure sensors and fed into the controller which changes the pilot valve input voltage to compensate pressure influence on the outlet flow. The presented valve is investigated theoretically by simplified analytical models as well as numerical methods and also evaluated experimentally. The results show that the proposed scheme is feasible. It has a reasonable static performance and an acceptable dynamic characteristic for low bandwidth disturbances. The flow force on the Valvistor poppet should be estimated and considered in the controller design.

Rolling element bearings constitute the key parts on rotating machinery and their fault diagnosis are of great importance. In this paper, a novel Two-Step fault diagnosis framework is proposed to diagnose the status of rolling element bearings with imbalanced data. The Wavelet Packet Transform (WPT) is used to determine the feature vectors. 16-dimensional wavelet packet node energies were extracted from the original datasets as the feature vectors prepared to input to the classifiers. Next, our proposed framework consists of two steps for the fault diagnosis, where Step One makes use of Weighted Extreme Learning Machine (weighted ELM) in an effort to classify the normal or abnormal categories, and Step Two further diagnoses the underlying anomaly in details. The effectiveness of our proposed approach is testified on the raw data collected from the rolling element bearing experiments conducted in our Institute, and the empirical results showed that our approach is really fast and can achieve the diagnosis accuracies more than 95%.

Electro-hydraulic proportional flow valves are widely used in hydraulic industry. There are several different structures and working principles. However, flow valves based on the existing principles usually have some shortcomings such as the complexity of the system and additional energy losses. A concept for a two-stage poppet flow valve with pilot pressure drop – pilot spool opening compensation is presented, and the linear relationship between the pilot stage and main stage, the semi-empirical flow equation are used in the electronic flow controller. To achieve the accurate control of the outlet flow, the actual input voltage of the pilot spool valve is regulated according to the actual pilot pressure drop, the desired flow rate and the given input voltage. The results show that the pilot pressure drop – pilot spool opening compensation method is feasible, and the proposed proportional flow control valve with this compensation method has a good static and dynamic performance.

In the fluid engineering, many projects involve movement and deformation of the boundary, but it is difficult to describe them by a simple algebraic expression because the movement of the boundary is determined by the force of hydraulic pressure, torque and other force which work together on the boundary. However, the previous numerical analyses are limited to the steady method or directly giving a speed to the spool which is difficult to actually simulate the movement of the spool. This paper developed a 6DOF model of a three-dimensional poppet valve to stimulate the transient flow field in the opening process by means of computational fluid dynamics software-Fluent. The movement of the spool is decided by fluid force which exert on it and its gravity. By comparing numerical simulation results of the valve displacement, pressure of the control chamber and the inlet and outlet flow rate of poppet valve with the experimental results, the numerical results are the same as the experimental results. So the method that the paper proposed is feasible and more truly to simulate the flow state in the opening process of hydraulic valve. And on this basis, the pressure field, velocity field and flow regime are researched when poppet valve reaches steady state, which provides an important theoretical basis for further research on hydraulic valve performance.