High-speed elevator car horizontal vibration fluid–solid interaction modeling method

High-speed elevator horizontal vibration seriously affects passenger comfort. To reach the smooth operation of the high-speed elevators, it is extremely important to study the horizontal vibration of the elevator car. There are two main factors that cause the horizontal vibration of the high-speed elevator car, namely, the guidance system excitations and the car aerodynamic characteristics running in the hoistway. Under the coupling action of these two factors, the horizontal vibration of the high-speed elevator car system is aggravated. To accurately obtain the horizontal vibration information of the high-speed elevator, we developed the high-speed elevator car horizontal vibration fluid–solid interaction model. It is decoupled by the proposed fluid–solid interaction decoupling solution. The influence of the high-speed elevator running speed, the guide rail profile deviation, and the rolling guide shoe dynamic parameters on the car horizontal vibration is analyzed. To verify the feasibility of the proposed method, the 5 m/s, 7 m/s, 8 m/s, and 10 m/s high-speed elevators are applied in a 288 m test tower. The simulation accuracy using the proposed method reaches the minimum of 0.93% in 5 m/s case of the peak-to-peak value, reaches the minimum of 3.11% in 10 m/s case of the A95 value, and reaches the minimum of 0.13% in 10 m/s case of the main frequency value. In general, the compared results of the peak-to peak vibration acceleration, the A95 value, and the main frequency are all closed in both 5 m/s, 7 m/s, 8 m/s, and 10 m/s cases.

Feature extraction for fault diagnosis based on wavelet packet decomposition: An application on linear rolling guide

Linear rolling guide is increasingly being used as the transmission system in computer numerical control machine tools due to its high stiffness, low friction, good ability of precision retaining, and so on. The lubrication of rolling linear guide affects significantly its performance and hence monitoring the lubrication condition during its operation is of great importance. In this article, the relation between different lubrication conditions of linear rolling guide and their corresponding vibration signals is studied. Three lubrication conditions labeled as “Poor,”“Medium,” and “Good” are simulated to represent the actual working conditions. A data acquisition system is set up to acquire the vibration signals corresponding to different conditions. The wavelet packet decomposition is employed to perform time–frequency analysis of the raw signal, after which the energy distribution of the decomposed signals is extracted as the feature. Two linear rolling guides manufactured by different companies are used in the experiments. The results demonstrate that the relation between the energy distribution extracted from vibration signals and lubrication conditions follows a certain rule. A typical feedforward backpropagation neural network is used as the classifier to verify the effectiveness of energy distribution. The average classification accuracy of the network with energy distribution as input is more than 95%. The results show that the lubrication conditions can be characterized by “energy” hidden in the vibration signals and the energy distribution is an appropriate feature that can be used for fault diagnosis of linear rolling guide.

Surface roughness effects on point contact elastohydrodynamic lubrication in linear rolling guide with fractal surface topographies

Purpose The purpose of this paper is to study the effects of surface roughness on the lubrication performances of the linear rolling guide, which provides theoretical guidance for its lubrication design. Design/methodology/approach The two-variable Weierstrass–Mandelbrot function is used to represent the random and multi-scale characteristics of the rough surface topography. The elastohydrodynamic lubrication (EHL) model of contact between the steel ball and raceway is built. The full numerical solutions of the pressure and film thickness are obtained by using the multi-grid technique. Findings The presence of surface roughness can cause the random fluctuations of the pressure and film thickness, and the fluctuations can become more dramatic for the rougher surfaces. It is also found that the film characteristics can be influenced significantly by the working conditions, such as the load, velocity and ambient viscosity of lubricants. Originality/value Characterization of surface topographies regarding EHL problems in the past studies cannot reflect random and multi-scale characteristics. In this paper, the fractal-based method is introduced to analysis of the point-contact micro-EHL. It reveals the mechanism and law of contact lubrication influenced by the fractal surface roughness and enriches the lubrication principle and method of the linear rolling guide.

Guiding mechanism design and precision pressure control in composites filament winding system

During the composite winding process, pressure fluctuation will affect the density and homogeneity of the products and will make the interfacial strength disaccord with the fiber volume fraction. In order to improve the guiding precision and stability of the winding pressure, the bearing guide is replaced by the rolling guide in designing the pressure guiding mechanism, and parametric model of the guiding mechanism is established based on dynamics experiment of the joint surfaces. By analyzing the modal and harmonic response, the corresponding measures for improvement are proposed. Experimental results show that the designed guiding mechanism based on the rolling guide has high precision and perfect stability. Additionally, roundness error and installation error of the mandrel can cause the winding pressure to fluctuate and the gas compressibility, nonlinear flow, dead zone, cylinder friction, measurement noise and other nonlinear disturbances have significant impact on the pneumatic pressure control system. Considering the above circumstance, an adaptive fuzzy proportional–integral–derivative (PID) controller based on the grey prediction is proposed. By predicting the output pressure, trend of the pressure signal can be reflected accurately, which provides a reliable basis for the decision-making of the fuzzy PID controller. Simultaneously, two separate fuzzy inference systems are employed to adjust the step length of the predictive control and the scale factor of the step self-tuning algorithm. Simulation and experimental results show that the fuzzy PID controller based on grey prediction has shorter settling time, smaller overshoot and error, stronger robustness and interference immunity. The designed guiding mechanism and control algorithm have effectively improved the precision and stability of the pressure control system for the composite materials winding formation.

Analysis of the Vertical Stiffness of Rolling Guide that Involves the Elastic Deformation of Carriage Skirt

Static stiffness is an important indicator of the performance of a rolling guide, having direct influence on the stiffness and precision of computer numerically controlled (CNC) machine tools. After preloading the rolling guide, an outward elastic deformation is generated at the carriage skirt, which leads to a decrease in the static stiffness of the rolling guide. Therefore, there would be relatively large errors between the numerical results and the experimental results when the carriage is considered as a rigid body. In this paper, an analytical method for estimating the vertical stiffness of rolling guide was proposed, which took into account the elastic deformation in the carriage skirt. The contact elastic deformation model under loads was given using Hertz’s contact theory, from which the numerical results for the vertical stiffness of the surface of the rolling guide was calculated when the elastic deformation in the carriage skirt was ignored. The calculation method for the carriage skirt deformation was given using the finite element method, from which the numerical relationship between the deformation and the contact force was obtained after fitting adjustment. An analytical model was therefore established and took into account the elastic contact deformation and the carriage skirt deformation, and a universal calculation method was proposed for vertical stiffness. Experimental results show that compared to those not involving the deformation, the numerical results for vertical stiffness involving the carriage skirt deformation matched more closely with the experimental results, with relative errors no greater than 6.5%.