This paper introduces a new type of active fluid-film bearing and its feedback control. In particular, we propose to actively adjust the angular velocity of the pads of a tilting-pad bearing in response to changes in the operating conditions of the rotating machine. This is motivated by the observation that there is more control authority in the pad tilt motion than in its radial translation. To this end, we first develop a dynamic model for the bearing system, inclusive of the nonlinear hydrodynamic force for the infinitely-short bearing case. A model-based controller is then constructed, based on measurements of the journal position and velocity and pad tilt angles, to ensure that the journal is asymptotically regulated to the bearing center. Numerical simulations illustrate the performance of the active bearing under the proposed control in comparison with the bearing’s standard passive mode of operation.
Persistent homology is an effective method for extracting topological information, represented as persistent diagrams, of spatial structure data. Hence it is well-suited for the study of protein structures. Attempts to incorporate Persistent homology in machine learning methods of protein function prediction have resulted in several techniques for vectorizing persistent diagrams. However, current vectorization methods are excessively artificial and cannot ensure the effective utilization of information or the rationality of the methods. To address this problem, we propose a more geometrical vectorization method of persistent diagrams based on maximal margin classification for Banach space, and additionaly propose a framework that utilizes topological data analysis to identify proteins with specific functions. We evaluated our vectorization method using a binary classification task on proteins and compared it with the statistical methods that exhibit the best performance among thirteen commonly used vectorization methods. The experimental results indicate that our approach surpasses the statistical methods in both robustness and precision.
Line-laser 3D scanning is a novel and promising automation technique for turbine blade inspection. One key task encountered in line-laser 3D scanning is centerline extraction of the laser stripes. In some regions, there is asymmetry of the line profiles caused by high curvature, such as the leading and trailing edges of a blade. According to the asymmetric Gaussian distribution line profile, this paper presents a new algorithm to extract the centerline of a laser stripe based on sub-pixel boundary extraction and medial axis transformation. The candidate boundary points of the laser stripe are extracted by zero crossing. Based on Taylor expansion and interpolation, the gray gradient distribution of the boundary can be estimated accurately. Following this, the accurate boundary points are extracted by extreme values of the gray gradient, and the centerline is calculated by medial axis transformation of the accurate boundary points. The proposed method can effectively reduce errors caused by the asymmetry of line profiles in areas of high curvature. The effectiveness of this method is verified using simulation and measuring experiments. The experiment results show that the extraction error of the asymmetric Gaussian line profile is within ± 0.15 pixels, and the root mean square error in measurement accuracy experiments does not exceed 0.015 mm.
Thin-walled turbine blades with complex features are a critical part of an aviation engine, and a small change in their geometric shape can erode the performance of the aviation engine. Inspecting the blade with an optical device is a promising technique. One key task involved is the calibration of the optical sensor with the rotating platform. This paper presents a novel calibration method for the optical inspection of the blade. Three target spheres are measured by a high-precision laser tracker and an optical sensor. The positions of the sphere centers are used to build a coordinate system and an approximated plane. Following that, the rotation axis and the rotation center of the rotating platform are easily calculated. According to a direction vector from the measured stripe, the transformation parameters between the optical sensor and rotating platform are further calculated. This calibration method is simple to carry out, and it guarantees that all the measured points are represented in the same coordinate system for subsequent parameter extraction and profile error evaluation of the blade surface. The experiments demonstrate the feasibility of the proposed method, and it found that the measurement error after calibration is within 0.02 mm.
In this paper, we demonstrate the design and simulation of a baseline PID rotor collective pitch controller with a gain scheduling for WindPACT) operation. We use a FAST-Simulink model of the closed-loop system to describe simulating this controller.Through the simulation analysis and comparing the result, control effect with the control strategy of gain scheduling results in better power regulation. At the moment of wind speed make more close to the rated wind speed, the changes of pitch angle is more sensitive, and the output power is larger and more smoothly.
The system produces strenuous vibration when the wind turbine is operating, it will be a great impact on running precision and components’ life of the whole system, the theoretical study of the research of wind turbine’s vibration is incomplete because of the complexity of the wind turbine’s structure and operating environment, as well as the difficulty of theoretical analysis. In this paper, the FAST established dynamic model of wind turbine, and preliminarily study the establishment of the wind turbine drive system model with multi-body dynamics software, finally dynamic response have been analyzed that based on the establishment of whole wind turbine model, which laid the foundation for wind turbine dynamic characteristic and the system’s optimal design.
A promising mechanical bearing candidate for active operation is the tilting-pad bearing. The proposed active tilting-pad bearing has linear actuators that radially translate each pad. The use of feedback control in determining the actuator forces allows for the automatic, continuous adjustment of the pad position during the operation of the rotating machine. In the first part of the dissertation, we develop a nonlinear dynamic model of the active bearing system. The hydrodynamic force produced by the fluid film is modeled as a nonlinear, squeeze-film damper plus repellent spring. A model-based nonlinear controller is then designed to exponentially regulate the rotor position to the origin. A proof-of-concept experiment shows that the active strategy improves the bearing performance relative to its traditional passive operation. Further, the experiment demonstrates that the model-based nonlinear control regulates the rotor comparably to a linear PID control, but requires significantly less control energy. The second part of the dissertation introduces a new type of active fluid-film bearing which actively adjusts the angular velocity of the pads of a tilting-pad bearing. This is motivated by the observation that there is more control authority in the pad tilting motion than in its radial translation. To this end, a dynamic model for the bearing system is developed, inclusive of the nonlinear hydrodynamic force for the infinitely-short bearing case. A model-based controller is then constructed, based on measurements of the journal position and velocity and pad tilting angles, to ensure that the journal is asymptotically regulated to the bearing center. Numerical simulations illustrate the performance of the active bearing under the proposed control in comparison with the bearing's standard passive mode of operation.
The oil-film bearings are widely used in mechanical transmission due to the good performance. In normal operating conditions, the journal and bearing shell are separated by the oil film, which contributes to the reduction of wear. And the stability and reliability of oil film has a great effect on load capacity. The paper briefly introduces research methods of the load capacity of oil-film bearings and points out some aspects of large oil-film bearings for in-depth study. Then combining dynamic simulation with experimental test on the scaled model of whole machine, a dynamic research idea is presented for large oil-film bearings.
In the process of wind turbine operation, the blade needs to withstand various kinds of loads. With wind turbine power kept getting bigger, the strength requirement of the blades become higher. In order to improve the strength of the blade, lots of new composite materials are use in blade material component parts. This paper studies the geometry laminated structure, external and structural characteristics of composite blade.
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