818 results about "Damping ratio" patented technology

The invention specifically relates to a mass tuned vibration reducer used for regulating the subsidence ratio of the vibration of the related structures. The mass tuned vibration reducer comprises a mass block, a spring, a damper and a base, and is characterized in that the damper is an adhesion-type damper formed by a damping cylinder, adhesive damping fluid and a piston, wherein, the piston and the adhesive damping fluid are arranged in the damping cylinder, and at least part of the piston is immerged into the adhesive damping fluid. The mass tuned vibration reducer adopts the adhesion-type damper formed by the adhesive damping fluid and the piston and can provide three dimensional damping, so as to effectively prevent side tumbling and ensure the vibration reducer realizes smooth actions; vibration mass is not needed to be provided with a special guide device, so that the mass tuned vibration reducer has reliable work and higher cost performance, and basically needs no maintenance. Meanwhile, the mass tuned vibration reducer realizes the aim of regulating the natural frequency and the subsidence ratio at any time, thus better exerting the vibration absorption performance of the mass tuned vibration reducer, ensuring stableness and safety of the pedestrians and vehicles on the large-span bridge and the thin and high building, contributing to prolonging the service lives of the thin and high building and the bridge, and having remarkable economic and social benefits.

The invention discloses a power system low-frequency oscillation mechanism analysis method based on micro-disturbance signal oscillation mode recognition. The method comprises the following steps of: providing a basis for judgment of oscillation mechanism types of power grid low-frequency oscillation accidents by using oscillation components provided by micro-disturbance recognition result in the process of a low-frequency oscillation accident; timely discovering a system running weak link and a potential oscillation source by performing statistic analysis on an entire-grid low-frequency oscillation mode oscillation frequency and damping ratio result which is calculated by micro-disturbance recognition in the given running time period; and establishing a corresponding relation between entire-grid oscillation mode characteristic change and system running condition parameter change to provide a basis for system running adjustment by performing multi-variable association analysis on the entire-grid low-frequency oscillation mode oscillation frequency and damping ratio result which is calculated by micro-disturbance recognition in the given running time period and the system running condition parameter.

The invention provides a method and system used for monitoring the vibration states of impellers of wind generating sets. The method includes the steps that the vibration acceleration of a predetermined measuring point on a vane of each wind generating set in at least one direction is detected according to a preset detection period, data of operating parameters of at least one of the wind generating sets are synchronously acquired, and the acquired data of the operating parameters of the set and the detected vibration acceleration data are recorded; data sets of recorded operating parameter data and recorded vibration acceleration data exceeding the preset amount are selected; according to the operating parameters of the wind generating sets, vibration acceleration data detected when the wind generating sets are in abnormal working conditions are removed from the data sets; operating mode analysis is carried out on the vibration acceleration data detected at the measuring points of the vanes, at least one of the inherent frequency, the damping ratio and the vibration mode of each vane in the operating state is extracted, and whether the impellers of the wind generating sets break down or not are determined according to the extracted inherent frequency, damping ratio and vibration mode.

Output-only modal testing of an object. Vibrations are excited in said object and measured by a number of vibration sensitive detectors. From the data of the measurements, a spectral density matrix function is determined. From this density matrix, auto spectral densities for the individual modes are identified performing a decomposition based on the Singular Value Decomposition technique. From the auto spectral densities of the individual modes, natural frequencies and damping ratios for the modes can be estimated, and from the singular vectors of the Singular Value Decomposition, the modes shapes can be estimated.

The invention relates to an aeroelastic stability fluid-structure interaction prediction method of turbo-machine changed interblade phase angles, which predicts the aeroelastic stability of a turbo-machine through the modal pneumatic damping ratio of different interblade phase angles by adopting an energy method. The method adopts the modal analysis containing prestress on established single-sector finite element models, realizes the vibration displacement transfer on the fluid-structure interaction interface through a data transfer method, adopts the dynamic mesh technology for obtaining mesh files taking the interblade phase angles into consideration, is used for unsteady computation fluid mechanic analysis of Junction Box modules in CFX, further obtains the modal pneumatic damping ratio of each interblade phase angle, and is used for predicting the aeroelastic stability. The method based on the fluid-structure interaction fully utilizes the cutting edge technology of the computational structural mechanics and the computation fluid mechanics, ensures the computation precision in each sub system, and improves the computation efficiency through the division of a fixed region and a movable region. The invention has good practical value and wide application prospects in the technical field of turbo-machine simulation.

The invention relates to a horizontal vibration energy-absorbing and vibration-damping device used for large engineering structures such as a longspan foot bridge, belonging to the field of vibration control of civil engineering structures. The horizontal vibration energy-absorbing and vibration-damping device comprises a constant strength cantilever beam consisting of struts at two sides and a cross beam, two ends of the cross beam are respectively and correspondingly connected with the struts at two sides, and the bottom ends of the struts at two sides are fixed on a foundation. The horizontal vibration energy-absorbing and vibration-damping device is characterized in that the upper end of a mass block is connected with the cross beam, the lower end of the mass block is provided with a rectangular permanent magnet; and one side of the lower part of the mass block is provided with a copper plate fixedly arranged on the foundation through a supporting member, and a gap is reserved between the copper plate and the rectangular permanent magnet. The invention ensures that the rigidity and the dampness of the tuned mass damper system realize complete separation, easily realizes that the damping ratio of TMD is continuously adjustable within a larger range though regulating the gap between the permanent magnet and the copper plate, and effectively solves the problems of oil leakage failure in the conventional TMD, difficult regulation of the damping parameters and interference on the frequency.

The invention discloses an online evaluation method of electric power system dynamic stability. The online evaluation method comprises the steps of step 1, carrying out high-frequency sampling by utilizing a PMU (Power Management Unit), and extracting an oscillation mode for sampling data by utilizing a matrix pencil identification method; step 2, detecting low-frequency oscillation, and emitting low-frequency oscillation warning if a damping ratio of the detected oscillation mode is lower than a set threshold value; step 3, carrying out small perturbation calculation on a system model in a current running mode through a frequency domain analysis method, and obtaining a characteristic value, a characteristic vector, a corresponding unit and participated factor information; and step 4, screening out information of a low-frequency oscillation mode from a small perturbation calculation result according to the low-frequency oscillation mode which is determined by the matrix pencil identification method, regulating a related electric power generator to output, and obtaining tide stability limit of call lines between related domains through time-domain simulation at the same time. According to the online evaluation method disclosed by the invention, the influence of noise is effectively avoided, the identification accuracy is improved, the calculating speed and the calculating efficiency are increased, and the online dynamic safety evaluation effect of the electric power system is obviously improved.

The invention relates to a method for controlling an index time-varying slide mode of flexible spacecraft characteristic shaft attitude maneuver, and belongs to the technical field of spacecraft control. The method comprises the steps that firstly, a system dynamically equivalent model, a dynamic model and a flexible vibration model are established under a spacecraft system, then, the vibration frequency and the damping ratio parameter of a closed loop system with the index time-varying slide mode control law are calculated, and a single-shaft multi-modality filtering input shaping device with a characteristic shaft as a rotary shaft is designed according to the designing method of the single-shaft input shaping device to restrain flexible vibration in three-shaft motion. Meanwhile, a state observer is designed to estimate flexible modal information in real time, and the method for controlling an output feedback index time-varying slide mode is formed. At last, saturability analysis is conducted on control torque so as to satisfy the physical saturation constraint of the control torque. By means of the method, the application range of existing input shaping is expanded, the input shaping technology is expanded from single-shaft maneuver to three-shaft maneuver, the self-robustness of filter input shaping is enhanced, and the purpose that the attitude maneuver path of the spacecraft is the shortest is achieved.

The invention discloses a rolling bearing fault feature extraction method based on the signal sparse representation theory, and the method comprises the following steps: constructing an over-complete dictionary representing local damages of a rolling bearing through employing a multi-stage inherent frequency unit impulse response function; recognizing the multi-stage inherent frequency and damping ratio of the rolling bearing and a sensor system from a vibration response signal through a related filtering method, and obtaining an optimized dictionary; solving a sparse coefficient through employing a matching tracking algorithm, and improving the solving speed and precision through reasonable segmentation; reconstructing an impact response signal of each segment, and obtaining the sparse representation of a fault feature signal; carrying out time domain index statistic characteristic analysis of time intervals of adjacent impact response components in a sparse signal, and diagnosing the type of a fault through combining a mean value and a mean square deviation value. The method has the advantages of an analytical method and an adaptive method, improves the precision of waveform features, and can iron out the defects that a conventional method based on Fourier transform is not suitable for rotating speed fluctuation.

A vibration generating apparatus with high yield, low cost, and can exhibit vibration tactile haptic effects even with variation in the natural frequency of a mechanical vibrator, including a damping system having a damping ratio ζ<1 to support a mechanical vibrator to a fastening part, and a magnetizing unit generating a dynamic magnetic field to vibrate the mechanical vibrator by non-contact, the mechanical vibrator generating a beat vibration by making the frequency of a drive voltage applied to the magnetizing unit, from a drive start or middle of drive, to be a non-resonant frequency out of a damped natural frequency of the mechanical vibrator, wherein the apparatus comprises a forced vibration control unit controlling to stop application of the drive voltage, in a beat wave defining an amplitude of the beat vibration, at a second valley part after a first peak part from the side of the drive start.

The invention belongs to the technical fields of simulating computational analysis and modal testing, and relates to a flutter stability domain modeling approach for a face cutting process. After all kinds of characteristic parameters of a material are known, a computer simulates a machining cutting process, calculates the cutting force in the machining process and analyzes the corresponding cutting coefficient. After the cutting coefficient is obtained, a modal experiment is utilized, modal testing is carried out on a machine tool spindle tool system, and the modal characteristic parameters of the machine tool spindle tool system are analyzed and comprise a multiple-order inherent frequency, a damping ratio, dynamic stiffness and the like. According to a flutter cutting theory, a stability lobe graph is drawn through combining the cutting coefficient and the system characteristic parameters and utilizing a computer assemble program, and is used for selecting the reasonable cutting parameter to avoid a flutter region, the processing precision and quality are improved, and a machine tool system is protected.

The invention provides an adjustable damping energy storage type tuned mass damper. A damping adjusting device of a damper of consists of a permanent magnet, coils, auxiliary rods, an energy storage battery, an adjustable resistor, a light-emitting diode (LED) pre-warning indicator light; in the reciprocating motion process that the damper absorbs the vibration energy of a main structure so as to generate inertial mass, a cylindrical spiral spring provides damping, the permanent magnet generates a variable magnetic field, induced electromotive force is generated in the coils so as to generate induction current, and the induction current generates electromagnetic damping to inhibit the movement of the permanent magnet; the adjustable resistor in the damping adjusting device is adjusted, so the magnitude of the electromagnetic damping is changed, and the damping ratio of a structure reaches the optimum damping ratio; and residual energy is recovered by using the energy storage battery, the LED pre-warning indicator light provides a pre-warning indication for a pedestrian and a vehicle, and multiple effects of vibration controlling, clean energy recovery, pre-warning and alarming of vibration conditions and the like.

A vehicle stability enhancement system that is adapted for an estimated driver workload. The system includes a driver workload estimation processor that estimates the driver workload based on certain factors, such as the vehicle speed or driver-behavior factors. The driver workload estimation is used to adjust the damping ratio and natural frequency in dynamic filters in a command interpreter to adjust a desired yaw rate signal and a desired side-slip signal. The driver workload estimation is also used to generate a yaw rate multiplication factor and a side-slip multiplication factor that modify a yaw rate stability signal and a side-slip stability signal in a feedback control processor that generates a stability control signal.

The invention discloses a test bench of the comprehensive performance of an air spring, and belongs to the technical field of vehicle engineering. The test bench can effectively achieve the aims of carrying out the vertical, transverse and twisting tests of the air spring at the same time and simulating the actual working states of the air spring. A rack of the test bench is in a four stand column type, a bearing platform is arranged in the middle of the rack, a device for bearing balance weight is arranged above the rack, a sensor is arranged below the rack, each stand column of the rack is provided with a cone-shaped fixing nut, a vertical hydraulic actuator which is arranged in a plane triangle mode is arranged below a workbench, and the volume of an additional air chamber is adjustable. The influence to the dynamics performance of the air spring by regional environment with different temperatures can be simulated by an external air conditioner system, multi-dimensional simulation is applied to the air spring through a shock excitation source, changes of loads and deflection of the air spring under the conditions with different environment temperatures and physical parameters are measured, and parameters such as dynamic stiffness, static stiffness, damping ratio and transfer ratio of the air spring are calculated through parameters of vibration characteristics. The test bench is mainly used for testing the comprehensive performance of the air spring.

An objective of the present invention is to provide an autonomous control method that autonomously controls a small unmanned helicopter toward target values, such as a set position and velocity, by deriving model formulas that are well suited for the autonomous control of small unmanned helicopters, by designing an autonomous control algorithm based on the model formulas, and by calculating the autonomous control algorithm. The autonomous control system for a small unmanned helicopter of the present invention comprises: sensors that detect the current position, the attitude angle, the altitude relative to the ground, and the absolute azimuth of the nose of the aforementioned small unmanned helicopter; a primary computational unit that calculates optimal control reference values for driving the servo motors that move five rudders on the helicopter from target position or velocity values that are set by the ground station and the aforementioned current position and attitude angle of the small unmanned helicopter that are detected by the aforementioned sensors; an autonomous control system equipped with a secondary computational unit that converts the data collected by said sensors and the computational results as numeric values that are output by said primary computational unit into pulse signals that can be accepted by the servo motors, such that these components are assembled into a small frame box, thereby achieving both size and weight reductions; a ground station host computer that can also be used as the aforementioned computational unit for the aforementioned autonomous control system; if the aforementioned ground station host computer is used as the aforementioned computational unit for the aforementioned autonomous control system, in the process of directing the computational results that are output from said ground station host computer to said servo motors through a manual operation transmitter, a radio control generator that converts said computational results as numerical values into pulse signals that said manual operation transmitter can accept; a servo pulse mixing/switching apparatus, on all said servo motors for said small unmanned helicopter, that permits the switching of manual operation signals and said control signals that are output from said autonomous control system or mixing thereof in any ratio; an autonomous control algorithm wherein the mathematical model for transfer function representation encompassing pitching operation input through pitch axis attitude angles in the tri-axis orientation control for said small unmanned helicopter is defined as $G_{\theta }\left(s\right)=e^{-\mathrm{Ls}}\frac{K_{\theta }{\omega }_{\mathrm{ns}}^2}{\left(s^2+2{}_s{\omega }_{ns}s+{\omega }_{ns}^2\right)\left(T_{\theta }s+1\right)s}$

wherein

• G_θ: parameter
• e^−Ls: dead time element
• K_θ: model gain
• T_θ: model gain
• ω_ns: natural frequency s: laplace operator
• ξ_s: damped ratio such that the aforementioned small unmanned helicopter is controlled autonomously based on the aforementioned mathematical model.

The invention discloses a modal test method of a large draught fan blade based on the photography measurement technology. The method comprises steps of using a pair of CMOS/CCD industrial cameras to carry out synchronous shooting on surface images of the draught fan blade under random excitation vibration; identifying and positioning multiple marking points in the images; extracting central sub-pixel level coordinates of the marking points and carrying out stereo matching of the double cameras; calculating three-dimensional coordinates of each measurement point through the three-dimensional reconstruction technology; carrying out micro-division processing on displacement data to obtain required vibration response (speed and accelerated speed) signals; through the Fourier transform, converting time domain signals into observation peak values in frequency domains to find corresponding modal frequencies; by combining analyzed frequency values, further using the stochastic subspace identification method (SSI) to precise calculate modal parameters of the blade; and acquiring the fixed frequency, the vibration mode and the damping ratio of the blade. According to the invention, by use of non-contact type multi-point synchronous vibration measurement, rapid high-precision model test on the draught fan blade can be achieved.

The invention relates to an online prevention and control method for low-frequency oscillation of an electric power system on the basis of two types of mechanisms. By the method, according to the idea of online pre-decision and real-time matching, low-frequency oscillation of a negative damping mechanism and low-frequency oscillation of a forced resonance mechanism can be monitored, the low-frequency oscillation of the negative damping mechanism can be monitored online and decision supporting information can be provided by utilizing a time-domain online Prony algorithm, a real-time small interference frequency-domain QR (quadrature right-triangle)algorithm, an IRA(irregular repeat-accumulate) algorithm and a characteristic value sensitivity principle; and further, when damping ratio of a capstan oscillation mode is higher than a damping threshold while oscillation exists, transmission rules of the low-frequency oscillation of the forced resonance mechanism and disturbance sources are recognized by a direct method and a hybrid dynamic simulation method which is implemented on the basis of PSD-FDS whole process stability analysis software. By the online prevention and control method which is high in credibility, real-time data source communication is guaranteed, and the low-frequency oscillation of the two types of mechanisms are monitored on line.

A method for performing bridge monitoring by using multiple strapdown inertial systems belongs to the bridge monitoring technology and includes: performing position setting for the strapdown inertial systems according to the dynamic characteristic of a bridge structure and performing installation calibration and initial calibration for the strapdown inertial systems; carrying out bridge dynamic load tests which include a pulsating test, a sports car test and a bumping test, and performing continuous monitoring by using deformation and vibration information of the strapdown inertial systems relative to a reference point and measurement points; obtaining static deformation angles and dynamic deformation angles of the measurement points of the bridge at each moment by using the deformation information obtained in an inertial test matching method; obtaining a girder deflection curve of the bridge by using the dynamic deformation angles of the inertial systems calculated at the reference point and the measurement points, and obtaining an impact coefficient of the bridge through further processing; using accelerometer output information to obtain acceleration time history curves of all the measurement points and obtaining displacement time history curves through integration; and analyzing the acceleration time history curves and the displacement time history curves in a time domain analysis method and a frequency domain analysis method to obtain structural parameters including bridge amplitude, damping ratio and vibration mode. The method has the advantages of being free of weather variation interference, little in manual operation, high in automatic degree and capable of performing continuous measurement.

The invention provides a working modal identification method based on time-frequency domain single-source-point sparse component analysis. The working modal identification method specifically includes the following steps that vibration signals of an equipment target position under the working state are obtained through measurement; time-frequency domain conversion is conducted on the mixed vibration signals; a single-source-point method is used for extracting the mixed vibration signals used for estimating a hybrid matrix in a time-frequency domain; a hybrid matrix estimation method based on K hyperline clustering sparse component analysis is used for estimating the hybrid matrix; after the hybrid matrix is solved, the time-frequency domain is returned, the l1 minimization method is used for reconstructing each order of source signals, and modal vectors of a structure are extracted; then the working modal frequency and the damping ratio are obtained through signal index expression. According to the method, the calculation amount in the hybrid matrix estimation process is reduced, under the poor condition that the number of measuring points is less than that of the source signals, modal parameters are identified effectively, and the method has good anti-interference capacity for incomplete sparsity of noise, abnormal values and the source signals.

The invention discloses a master-slave control method for an energy storage inverter based on a virtual synchronous generator. The energy storage inverter comprises a master control inverter and a slave control inverter, wherein the master control inverter adopts a voltage source output mode based on the virtual synchronous generator to provide amplitude and frequency of network voltage, provide virtual inertia and a virtual damping ratio according to the capacity of the master control inverter, and meanwhile provide static active and passive current quotas to each inverter; the slave control inverter adopts a current source output mode based on the virtual synchronous generator to receive static active and passive current quotas issued by the master control inverter, and meanwhile provide the virtual inertia according to the capacity of the slave control inverter. According to the method, in island parallel operation, a load is non-uniform and fluidity is relatively low under various load conditions, and relatively high output voltage power quality is provided; compared with traditional master-slave control, a controller structure does not need to be changed when switching between grid connection and disconnection is performed, and the master control inverter and the slave control inverter independently provide the virtual inertia without depending on communication, so that improvement on system stability under dynamic condition is facilitated, and the reliability is relatively high.

In a storage device, a bad-sector detecting unit detects a bad sector, and a process determining unit determines whether rescue process is performed for the bad sector. Upon determining to perform the rescue process, the process determining unit controls a damping ratio. A table-updating control unit records various information in an alternating-process control table, and a controller records and reproduces data with respect to a rescue sector based on the alternating-process control table.