46 results about "Modal coupling" patented technology

The invention discloses a testing method for unmanned plane flight-control structure modal coupling, and aims at providing a flight-control structure modal coupling testing method which can save resources, so as to solve the problems that stimulation signals are not injected, states of a plane cannot be effectively confirmed, a control loop cannot be divided reasonably in a unmanned plane flight-control structure modal coupling test. The method is realized by following measures that: a flight-control computer is adopted to compile software which can automatically generate stimulation signals, the flight-control computer uses received comprehensive inspection vehicle signals to generate agreement stimulation signals and plane control surface stimulation signals which are used as input of the test, ground states and air states are divided according to flight configuration conditions, vibration sensors used for monitoring plane vibration conditions are arranged on the head of the plane, the wing tip ends of swings and the wing tip end of a V-shaped tail wing, and parameters of the vibration sensors can be directly monitored by an oscilloscope.

The invention discloses a milling stability domain prediction method under multi-modal coupling to solve a technical problem that the efficiency of an existing milling stability domain prediction method is low. The technical scheme is that firstly the transmission function of a process system is determined through a modal test experiment, then modal parameters are extracted from the transmission function and two orthogonal direction modal parameters are paired and combined, a milling test is carried out to calibrate a milling force coefficient, based on the milling force coefficient and each scale of modal parameters, an improved semi discrete method is employed to obtain a stability lobe diagram under each scale of modals, and finally lobe diagrams under obtained from each scale of modals are drawn in a same coordinate system to obtain a stable domain under multi modal coupling. Through a test, when a cutting cycle is divided into 40 sections, 80 sections and 120 sections, compared with a background technology method, the method can save time for 4949.6 seconds, 74200.4 seconds and 344699.5 seconds, and the efficiency is increased by 85.9%, 92% and 88.5%.

A small aircraft engine multi-point rubbing fault simulation experiment device includes a rotor system, a drive system, a rubbing system, a support system, and a measurement and control system. The rotor system adopts a centrifugal compressor and a leaf disc integrated structure axial flow turbine, which is consistent with the real structure of the small aircraft engine; the drive system includesa motor, a speed increaser and a magnetic powder brake; the rubbing system includes a compressor rubbing structure, a turbine rubbing structure and a rotating shaft rubbing structure, wherein each structure is an independent structure, and the structures can be combined with each other to realize multi-position and multi-modal coupling rubbing; the measurement and control system includes a motor rotating speed controller, a motor comprehensive protector, a data collector, a displacement sensor and a vibration acceleration sensor, wherein the motor comprehensive protector can prevent damage tothe motor under a high load. The invention can realistically simulate multi-type rubbing faults of the small aircraft engine rotor system at multiple locations, and can be used to study the vibrationresponse of the small aircraft engine under a plurality of frictional coupling effects.

A system for reducing modal coupling of combustion dynamics includes a plurality of combustors, and at least one fuel injector in each of the plurality of combustors. The system also includes structure for dithering a combustion instability frequency in at least one combustor in the plurality of combustors. A method for reducing modal coupling of combustion dynamics includes flowing a compressed working fluid at a temperature to a plurality of combustors and flowing a fuel to at least one fuel injector in each of the plurality of combustors. The method further includes dithering at least one of the temperature of the compressed working fluid flowing to the plurality of combustors or the fuel flow to the at least one fuel injector in at least one combustor in the plurality of combustors.

A system and method for reducing combustion dynamics includes first and second combustors, and each combustor includes a fuel nozzle and a combustion chamber downstream from the fuel nozzle. Each fuel nozzle includes an axially extending center body, a shroud that circumferentially surrounds at least a portion of the axially extending center body, a plurality of vanes that extend radially between the center body and the shroud, a first fuel port through at least one of the plurality of vanes at a first axial distance from the combustion chamber, the plurality of vanes being located at a second axial distance from the combustion chamber. A second fuel port is provided through the center body at a third axial distance from the combustion chamber. The system further includes structure for producing a combustion instability frequency in the first combustor that is different from the combustion instability frequency in the second combustor.

The invention discloses a method for judging degree of looseness of a bolt based on vibration mode information. The method comprises the following steps of firstly obtaining a freely attenuated vibration response signal by applying pulse excitation to the bolt connection structure; secondly realizing the multi-modal coupling feature separation on the vibration response signal based on a variational mode decomposition algorithm; thirdly calculating the frequency domain similarity index of each order of vibration mode component in two states; and finally judging the degree of looseness of the bolt connection structure according to the constructed index. The method is simple and practicable and is convenient for online non-destructive testing of the connection state of the bolt connection structure, is favorable for improving the judgment accuracy by judging the degree of looseness of the structure using the similarity index of the loose sensitive vibration mode component, and is beneficial to describe the change of vibration mode information caused by structural state changes and reflect the health status of the structure by constructing the detection index including frequency and amplitude information of the signal from the frequency domain, thereby having important engineering practical value.

The invention discloses a dynamic calibration method for a high-frequency force balance, which comprises the steps of performing whitening on a measurement signal x(t) to acquire a whitened signal z(t); seeking an orthogonal matrix V, enabling the whitened signal z(t) to equal to Vq(t), and thus acquiring a separated signal q(t); performing natural frequency and modal damping ratio recognition on the separated signal in modal coordinates; correcting the separated signal according to recognized parameters; and inversely deducing according to the separated signal to acquire a corrected pneumatic load. According to the invention, separation is performed on a coupling signal, and for independent components acquired by separation, natural frequency and modal damping ratio recognition is performed on the separated signals one by one by adopting a curve fitting method through combining aerodynamic characteristics, so that a dynamic amplification effect of a modal coupling system is corrected and eliminated, a real aerodynamic load spectrum density matrix is acquired finally, the reliability of parameter recognition and corresponding HFFB (High-Frequency Force Balance) dynamic signal calibration can be improved to the maximum extent, and an important basis is laid for subsequent accurate estimation for high-rise building prototype wind-induced responses.

The invention provides a milling three-dimensional stability forecasting method of a six-freedom-degree series robot and relates to the technical field of robot machining application. By means of themethod, the machining posture of the six-freedom-degree series robot is determined firstly, and the angle value of each joint of the robot is obtained; then the structural rigidity of the robot in three directions is obtained, and the milling cutting rigidity value of the robot is calculated and obtained; a homogeneous transformation matrix among all kinematics coordinate systems is obtained; theinherent frequency of various orders and corresponding modal shapes of the robot are obtained through analysis; the main rigidity direction of the robot is obtained, and the transfer matrix from cutting force to the main rigidity direction of the robot is determined; and finally, the machining direction is determined, and robot milling three-dimensional stability is used for judging and forecasting stability. By means of the milling three-dimensional stability forecasting method of the six-freedom-degree series robot, the machining feeding direction can be selected in advance, modal coupling fluttering in the milling process is avoided, and the quality of the machined surface is improved.

The invention discloses a clamp and tool bar system for providing the vibration reduction performance of a numerical control tool by utilizing a microcosmic friction phenomenon in combination with a modal coupling method for mass distribution and mass vibration reduction of the numerical control tool under the premise that macroscopic assembly sliding is not caused. By regulating forward pressure, static rigidity, a vibration reduction coefficient and dynamic rigidity on each assembly combination surface, the vibration reduction performance of an overall tool structure is optimized. A tool bar structural member 4 is made from a material with high elastic coefficient and high density ratio, and a tool bar connecting piece 5 is made from a material with high elastic coefficient, so that the vibration modal frequency and the vibration reduction efficiency are improved. By utilizing modal coupling, the vibration reduction performance of a mass vibration reduction unit is further improved, and the torsional vibration resistance and the bending vibration resistance of the tool are improved. According to the technical solution, by virtue of a modular tool bar, the ratio of extended length to diameter in a using process of the numerical control tool can be improved, and the vibration reduction performance of a tool structure is improved.

The invention belongs to the technical field related to robot milling, and discloses a robot milling chatter prediction and main modal analysis method, which comprises the following steps: (1) constructing a dynamic cutting force model considering a regeneration chatter effect, and combining the dynamic cutting force model with a robot dynamic model considering a modal coupling effect to obtain adynamic cutting force model considering a regeneration chatter effect; carrying out modal space quality normalization conversion to obtain a final kinetic model; (2) analyzing the change of the dynamic cutting thickness of the robot along with the rotating speed under different modes according to the kinetic model, determining a mode influence factor, and judging the dominant mode of the milling flutter stability of the robot under a certain working condition by adopting the mode influence factor so as to provide a mode selection basis for predicting the milling stability of the robot, whereinthe modal influence factor is the phase difference of two times of blade ripples. According to the invention, operation data is saved, and the stability prediction efficiency is improved.

The invention discloses a load analysis method and device considering a modal coupling effect and a storage medium. The method comprises the following steps: 1, preparing raw materials; carrying out adynamometric balance wind tunnel test on the building; acquiring an overturning moment time sequence and a torque time sequence; and establishing an aerodynamic bending moment power spectrum matrix of a building structure base, analyzing to obtain a total bending moment response, a background bending moment response and a resonance bending moment response considering a modal coupling effect through the modal distribution coefficient matrix and the frequency response function matrix which are obtained through calculation, and calculating an equivalent static wind load of the building structure. The device comprises a memory for storing a program and a processor for loading the program to execute the analysis method. The storage medium stores instructions for executing the analysis method by a processor. By using the analysis method provided by the invention, the equivalent static wind load data precision can be higher, and the safety and reliability of a building can be ensured when the method is applied to building structure analysis. The method can be widely applied to the technical field of building analysis.

The invention discloses a design method for improving the elastic stability of an aerodynamic servo. The method comprises the steps: correcting a body elastic model and a transfer function through employing a whole-plane ground resonance test or whole-plane ground structure modal coupling test data design optimization technology, and then improving the elastic stability of the aerodynamic servo through employing a flight control law dynamic parameter adjustment technology; the aerodynamic force, the structural elasticity and the coupling relation between control systems can be well considered,so that the flight quality requirement, the stability margin requirement of the control systems and the pneumatic servo elastic stability requirement are met within the full envelope range, and the method is already applied and verified in the multi-control-surface unmanned aerial vehicle. The problem that the pneumatic servo elastic stability of a multi-control-surface unmanned aerial vehicle isdifficult to control is solved.

The invention relates to suppression of high frequency resonance in an electro-optical device. The electro-optical device includes an optical waveguide formed in a substrate and a plurality of electrically floating electrode segments that are positioned on the substrate to intensify an electric field in the optical waveguide. The device also includes a RF ground electrode that is positioned on the substrate. The RF ground electrode defines a slot having a shape that suppresses modal conversion and propagation of high order modes in the RF ground electrode and in the plurality of electrically floating electrode segments, thereby suppressing modal coupling to the substrate. The device further includes a buffer layer formed on the upper surface of the substrate, on the plurality of electrically floating electrode segments, and in the slot. A driving electrode receives a RF signal that induces-the electric field in the optical waveguide.

The invention discloses a sound-structure-structure coupling system structure vibration response prediction method, a system and a storable medium, and relates to the related technical field of mechanical vibration noise analysis. The specific steps of the method are as follows: decoupling a sound-structure-structure coupling system into a sound cavity subsystem and a structure subsystem, and respectively establishing a model of each subsystem; performing modal analysis on the uncoupled subsystem, respectively extracting modal data of the structure subsystem and the acoustic cavity subsystem, and calculating modal coupling parameters between the two subsystems by using the modal data of the structure subsystem and the acoustic cavity subsystem; obtaining a dual mode equation of the acoustic-solid coupling system according to the mode coupling parameters and the models of the subsystems; obtaining a system acoustic-structure coupling response according to the dual-mode equation; According to the invention, the finite element and the dual mode are combined, so that the efficiency of the prediction method is improved, data support can be provided for noise control of the engine, the research and development period is shortened, the delivery speed is increased, and the competitive advantage is increased.

The invention provides a high-frequency local response indication method for a sound-solid coupling structure. A finite element method, a modal power flow equilibrium equation and a local energy indication theory are combined to indicate the high-frequency local response of the sound-solid coupling structure, the finite element method is used for obtaining the displacement modal vibration mode ofa structure subsystem on a coupling edge, the stress modal vibration mode of a sound cavity subsystem on the coupling edge and the inherent frequency and the modal quality of the subsystem, a modal coupling loss factor between subsystems is calculated, and the modal power flow equilibrium equation is established and solved to obtain the modal energy of the structure subsystem. Finally, the local energy indication theory is used for solving the local energy response of the structure subsystem, and a local stress/ strain response is solved through a relationship between the strain energy and thestress strain of an isotropy material. By use of the method, the high-frequency local response indication method for the sound-solid coupling structure can be accurately indicated, and the problems that discretization methods including a traditional finite element method, a boundary element method and the like are low in calculation efficiency and each hypothesis of a statistical energy analysismethod can not be completely satisfied usually in engineering application and is difficult to obtain the local energy of the subsystem can be solved.

The invention discloses a radiation acoustic power calculation method based on a modal partial coupling hypothesis. The method mainly comprises the steps of structure modal calculation, structure vibration response solving, vibration acceleration mapping to a surface air layer and radiation acoustic power calculation based on the modal partial coupling hypothesis. Compared with a radiation acoustic power calculation method based on a modal uncoupling hypothesis and a modal coupling hypothesis, the radiation acoustic power calculation method based on the modal partial coupling meets the requirement for energy conservation, achieves complementation of the uncoupling hypothesis and the coupling hypothesis, and achieves the purpose of eliminating theoretical energy errors.

The invention discloses a laser profile modification method for reducing the modal coupling error of a vibratory silicon micro-machined gyroscope. The method comprises the following steps: 1, signal test: testing the driving signal Vd and the modal coupling error signal Vm of a silicon micro-machined gyroscope chip, and determining the peak values and the phase relationships of the two signals; 2, determining the laser profile modification type according to the signals in step 1; 3, determining the profile modification position according to the signals in the step 1; and 4, carrying out laser profile modification according to the type obtained in step 2 and the position obtained in step 3. The laser profile modification method has the advantages of simple principle, simple operation, reduction of the modal coupling error, and improvement of the working performances of the silicon micro-machined gyroscope.

The invention discloses an ultrasonic sensor and an electronic device. The ultrasonic sensor includes a piezoelectric layer, a matching layer, and a backing layer; the matching layer is formed on onesurface of the piezoelectric layer; the matching layer is made of metal and a polymer; the backing layer is placed on the other surface of the piezoelectric layer; and the backing layer and the matching layers are respectively placed on the two opposite surfaces of the piezoelectric layer. According to the ultrasonic sensor and the electronic device provided by the embodiments of the present invention, the matching layer is additionally arranged on the piezoelectric layer of the ultrasonic sensor, so that the plurality of resonant frequencies of the ultrasonic sensor can undergo multi-modal coupling, so that the bandwidth of the ultrasonic sensor can be extended.

The invention discloses a sensor sensitivity improving method and system based on nonlinear domain modal coupling, and the method employs the coupling characteristic between at least two vibration modes in a resonator, employs a first mode in the two modes as a frequency output mode, and employs a second mode as a cavity mode to sense an external variable to be measured. In order to excite a coupling characteristic between the first mode and the second mode, the method entails the application of at least one pump. Meanwhile, in order to improve the sensitivity of the sensor, according to the method, the vibration state of the first mode needs to be excited to a nonlinear vibration area, the high-branch frequency of the second mode serves as final output, phase closed-loop control can be conducted on the first mode through a phase-locked loop, and rapid collection and measurement of the frequency are achieved. The invention is applied to a frequency output type sensor, can improve the sensitivity of the frequency output type sensor, does not need to introduce other auxiliary devices, and has the advantages of easy operation, convenient integration, stability, reliability, wide application range and the like.