21 results about "Harmonic balance" patented technology

The invention belongs to the technical field of robot milling dynamic characteristic analysis, and discloses a robot milling stability prediction method and device considering nonlinear rigidity, and the method comprises the steps: (1) employing a cubic polynomial to represent the nonlinear characteristic of the joint rigidity of a robot, and constructing a nonlinear kinetic equation of the robot; (2) solving the nonlinear kinetic equation based on an incremental harmonic balance method to obtain a nonlinear frequency response function of the robot; and (3) obtaining a stability lobe graph based on the nonlinear frequency response function and a milling stability frequency domain model constructed by adopting a milling vibration stability analysis zero-order method, and then completing prediction of the milling stability of the robot based on the obtained stability lobe graph. According to the method, the influence of the nonlinear rigidity of the joint is effectively considered, and the accuracy of prediction of the milling stable area of the robot is improved.

This invention discloses a performance optimization method for a tristable energy harvester under low-frequency excitation based on vibration resonance, belonging to the field of energy harvester optimization. The implementation method is as follows: a standard rectifier circuit is selected as the nonlinear collection circuit and connected to the energy harvester to achieve a stable DC output; a strongly nonlinear system model of the electromechanical coupled tristable energy harvester system is established; the slow variable equation of the tristable energy harvester system is derived using the variable separation method; the steady-state solution and analytical expression of the DC power of the tristable energy harvester system are derived using the harmonic balance method; an optimization model of the tristable energy harvester system under low-frequency excitation is obtained based on vibration resonance; the influence of low-frequency excitation amplitude, low-frequency excitation frequency, stiffness coefficient, time constant ratio, and electromechanical coupling coefficient on the collection performance of the tristable energy harvester system is analyzed using the optimization model, and the optimal combination is selected to achieve efficient energy harvesting of the tristable energy harvester system under low-frequency excitation.

The present application relates to a kind of piezoelectric type nonlinear energy sink optimal target energy transfer threshold acquisition method, for elastic plate-piezoelectric type nonlinear energy sink system, method includes the following steps: establishing the two-degree-of-freedom model of elastic plate-piezoelectric nonlinear energy sink system, obtains coupled system dynamics equation;Using harmonic balance method to solve the forced vibration response of system, obtains the response surface of main system;According to the nonlinear modal of coupled system dynamics equation obtained by system;The expression of nonlinear modal is mapped with system response, obtains the target frequency response curve of the change of predicted coupled system response surface, and then the lower limit and upper limit of target energy transfer threshold are solved, and the optimal target energy transfer threshold is obtained.Compared with prior art, the calculation process is reduced, and the calculation result is tested, which can ensure accuracy.

The application discloses a kind of quasi-periodic state-dependent regenerative milling stability analysis method and system.Method includes: milling system adopts two-degree-of-freedom vibration model and state-dependent time-delay differential equation modeling;Spindle periodic balance solution is expressed by finite harmonic series, and is solved by numerical iteration and verified;Quasi-periodic vibration is solved by large-period single-frequency harmonic balance method, and time-delay coupling characteristics are described by delay state vector;Spindle periodic and large-period model are associated with Floquet self-excitation frequency, forming a multi-scale analysis framework;Vibration-cutting force-time delay full coupling is simulated by using explicit dynamic method, and spindle periodic balance solution, quasi-periodic balance solution, stability spectrum radius and flutter boundary data are output, to realize milling system stability state determination and quasi-periodic flutter prediction.The application realizes the unified solution of periodic and quasi-periodic flutter by multi-scale integrated analysis, and provides support for high-speed milling process parameter optimization.

The invention provides a composite high-order quasi-zero stiffness vibration isolator and an optimization method thereof, and belongs to the field of vibration isolators. The problems that a traditional quasi-zero-stiffness vibration isolator is prone to exceeding a low-stiffness displacement interval under the conditions of low damping and large excitation, dynamic stiffness is sharply increased, resonant frequency drifts and frequency jumps are caused, and the engineering applicability of the quasi-zero-stiffness vibration isolator is seriously limited are solved. A vibration isolation system with a nonlinear rigidity coupling characteristic is constructed by integrating a positive-rigidity supporting spring, a negative-rigidity mechanism and an electromagnetic vibration isolation mechanism. Analysis shows that the high-order quasi-zero stiffness design eliminates the low-order stiffness item through the specific parameter design, expands the quasi-zero stiffness displacement range, and reduces the dynamic stiffness of the system, so that the initial vibration isolation frequency is significantly shifted to a lower frequency, and the formant is well inhibited; the accuracy of the model is verified through numerical simulation and a harmonic balance method, and the advantages of the high-order quasi-zero stiffness system in the aspects of resonance peak suppression and vibration isolation bandwidth widening are proved.

The invention relates to a blade flutter evaluation method based on a complete time domain harmonic balance method under air inlet distortion, and the method comprises the steps: calculating the vibration mode of an aero-engine blade, respectively appointing a blade vibration rule and an air inlet distortion boundary condition, thereby determining and analyzing the fundamental frequency and harmonic waves of a blade vibration flow field and an air inlet distortion flow field, and further calculating the blade flutter evaluation result. A coupling flow field of air inlet distortion and blade vibration is solved based on a complete time domain harmonic balance method, accumulated work in a vibration period is obtained, and the aeroelastic stability of the aero-engine blade is evaluated according to positive and negative accumulated work. According to the method, the influence of multiple parameters and any form of air inlet distortion on the aeroelastic stability of the aero-engine blade can be evaluated at the same time; and the evaluation result is calculated based on single-channel and high-fidelity numerical values, so that the calculation time consumption and the calculation resource demand are remarkably reduced, and the method has important significance on the anti-vibration design of the rotor and stator blades of the aero-engine.

This invention discloses a computational method for vibration and stress fatigue analysis of hydraulic pipelines under nonlinear boundary conditions. The method first establishes the dynamic control equations of the hydraulic pipeline under nonlinear boundary conditions, then solves and verifies the system using the harmonic balance method and the Runge-Kutta method to obtain the response and stress distribution of the entire pipeline. Based on the calculation results, the tensile and bending stresses at arbitrary locations in the pipeline are further solved. This identifies the location with the highest stress, and fatigue life is predicted based on the maximum stress. This method more closely approximates the actual working conditions of hydraulic pipelines, improves the accuracy of stress analysis, and contributes to in-depth research on the fatigue failure mechanisms of hydraulic pipelines, providing theoretical support for engineering design and fault early warning.

This invention relates to a method for optimizing the target energy transfer characteristics of a nonlinear energy trap system, specifically an elastic plate-piezoelectric nonlinear energy trap system. The method includes: establishing a two-degree-of-freedom model of the elastic plate-piezoelectric nonlinear energy trap system to obtain the dynamic equations of the coupled system; solving for the slow-invariant manifold of the coupled system using the complex variable-average method, and obtaining the parameterized design conditions for the coupled system to exhibit a forced vibration response; solving for the forced vibration response of the coupled system using the harmonic balance method to obtain the system response surface; and optimizing the target energy transfer characteristic threshold range of the system by adjusting the system mass ratio, negative linear stiffness, damping, and nonlinear stiffness within the parameterized design conditions, based on the changes in the system response surface. Compared with existing technologies, this invention provides systematic guidance for the parameter design of the elastic plate-piezoelectric nonlinear energy trap system, improving vibration suppression effects and broadening the target energy transfer characteristic threshold range.

This invention discloses a harmonic balancing method, device, and medium based on a neural network, belonging to the field of nonlinear circuit simulation analysis. The method includes the following steps: S1, establishing the node voltage equations of the nonlinear circuit; S2, constructing a neural network and an error function: constructing a three-layer BP neural network, where the input layer is a discrete time sequence of a complete cycle; the hidden layer includes a set of trigonometric functions of harmonic components or mixed frequency components; the output layer is the steady-state solution of the node voltage equations of the nonlinear circuit; the error function is constructed based on the node voltage equations of the nonlinear circuit; S3, training the constructed neural network to obtain the steady-state solution satisfying the node voltage equations of the nonlinear circuit. This invention avoids the frequent time-frequency transformations in the wave balancing method during iteration and is applicable to single-tone and multi-tone excitation. Simultaneously, it has high accuracy and good convergence, and is a method independent of initial values, making it very suitable for the periodic response analysis of nonlinear circuits.

The invention relates to a high-dimensional complex nonlinear differential equation periodic response efficient universal easy-to-use solving method, which is characterized in that an automatic differential technology and a harmonic balance method are fused, and the method comprises the following steps: step 1, solution setting: representing the periodic response of a system by using discrete Fourier series; step 2, harmonic balance: substituting periodic response in a Fourier series form of the system back to a system kinetic equation, and converting a differential equation into an algebraic equation through a harmonic balance program; 3, calculating a Jacobian matrix, namely, quickly obtaining an accurate Jacobian matrix of the algebraic equation after harmonic balance by utilizing an automatic differential technology; and 4, solving an algebraic equation, namely calculating by using a Newton-Raphson method to obtain a system periodic response. The method solves the problems that a high-dimensional complex nonlinear differential equation response solving method is low in efficiency, not universal and not easy to use, can be widely applied to calculation of high-dimensional complex nonlinear system dynamic response, and has the advantages of being efficient, universal, capable of being used immediately after being opened and modularized.

A method for carrying out a non-linear analysis of at least two gears in the frequency domain provides for generating a gear mathematical model, define a motion equation of such model and solve such equation with a method of the coupled harmonic balancing, the implementation of method comprising the solution of such equation simultaneously considering a static condition and a dynamic condition of the interaction between the gears.

The invention discloses a time-varying nonlinear aerodynamic damping identification method based on harmonic balance and wavelet transform, and the method comprises the following steps: 1), obtaining related parameters of a structure and an incoming flow condition; 2) using CFD-based fluid-structure interaction numerical simulation to output wind-induced response time history data of the structure under the action of wind; 3) according to the obtained displacement and wind pressure information, instantaneous displacement-load parameter extraction is carried out based on a wavelet transform theory; 4) performing transient aerodynamic damping identification based on a harmonic balance theory; 5) establishing a time-varying nonlinear aerodynamic damping model based on a hybrid modeling strategy; and 6) based on the time-varying nonlinear aerodynamic damping model, performing response prediction of the tensile membrane structure considering the fluid-solid coupling effect, and performing performance evaluation. According to the time-varying nonlinear aerodynamic damping recognition and modeling method for the flexible engineering structure, the time-varying nonlinear aerodynamic damping model capable of considering the time-varying fluctuation effect and the nonlinear characteristics at the same time is constructed, and compared with a traditional aerodynamic damping model capable of only considering nonlinearity, the time-varying nonlinear aerodynamic damping model has the advantages that the time-varying fluctuation effect is greatly improved; according to the method, the inherent time-varying fluctuation characteristics of aerodynamic damping can be described better, the prediction precision of the wind-induced response of the flexible engineering structure considering the fluid-structure interaction effect is remarkably improved, the applicability is improved from the source, the accuracy of structural wind-induced response evaluation analysis is improved, and reliable support is provided for wind resistance design and structural optimization of the structure.

This application relates to an optimization method for the output matching network of a power amplifier. The method includes: performing load-pull simulations on the target power amplifier transistors at multiple frequencies within the design bandwidth based on a preset gain compression point, obtaining isopleth curves of various performance indicators; obtaining the optimal load impedance and the optimal impedance domain related to the target performance indicators based on the isopleth curves of various performance indicators; evaluating the performance of the current output matching network based on the optimal load impedance and the optimal impedance domain, obtaining an error value based on the output matching impedance; and iteratively optimizing the component parameters of the output matching network using an optimization algorithm based on the optimization objective of the output matching network until the error value meets a preset termination condition, obtaining the optimized result of the output matching network. This method can eliminate the need for repeated harmonic balance simulations during the optimization process, improving the optimization efficiency of the power amplifier output matching network.

The application belongs to the technical field of transformer core multi-physical field modeling calculation, and discloses a nanocrystalline roll core magnetic vibration coupling calculation method, system, device and medium, the method comprises the following steps: constructing a complex frequency domain field-circuit coupling equation based on the harmonic balance idea, calculating the magnetic flux density distribution inside the nanocrystalline roll core; considering the transverse anisotropy characteristics of the laminated structure, deducing the equivalent Young's modulus and Poisson's ratio of the core; considering the actual structure characteristics of the roll core, constructing a two-dimensional plane stress-strain constitutive relation; establishing a complex frequency domain magnetic vibration coupling finite element model, and calculating the vibration distribution on the surface of the roll core. The application calculates the magnetic flux density distribution of the nanocrystalline roll core by introducing Laplace transform and harmonic balance method; at the same time, the transverse anisotropy characteristics of the core laminated structure are considered, the mechanical properties are homogenized modeling, and the obtained equivalent mechanical parameters are embedded in the elastic matrix reflecting the actual core structure, and then the efficient and accurate calculation of the vibration displacement on the surface of the roll core is realized.

The invention discloses a thin-wall structure vibration control method based on an inerter type nonlinear energy trap, and relates to the field of civil aviation aircraft thin-wall structure dynamics. Aiming at the problems of complex broadband vibration characteristics, contradiction between light weight and vibration control, insufficient multi-working-condition adaptability and the like of an aerospace thin-wall structure, the invention provides a distributed inerter type nonlinear energy trap system, a coupling dynamic model is established, and related parameters and connection modes are determined to realize broadband fine control; adopting a harmonic balance method to solve steady-state response, and combining short-time Fourier transform, a subspace identification principle and a minimum mean square algorithm to realize vibration response frequency tracking and parameter adaptive adjustment; and with minimization of system response as a target, key parameters are optimized by using a particle swarm method, and a multi-working-condition adaptive control algorithm is developed. According to the invention, the nonlinear rigidity is dynamically adjusted to match the excitation frequency, and efficient, broadband and lightweight vibration control under multiple working conditions is realized.

The invention provides a marginal plate damping device optimization method based on Monte Carlo simulation and Latin hypercube design, and the method comprises the steps: selecting a certain order of vibration mode of a blade mode to carry out the structure optimization design of a damper based on the vibration mode of the blade mode, and determining the harmonic response frequency range of the blade; processing a blade group substructure by a dual-mode synthesis method, and combining an overall structure matrix through a substructure reduction matrix; obtaining a parameter matrix and a two-dimensional contact surface friction model, and constructing a dynamic equation set with dry friction nonlinearity; a dynamic equation set with dry friction nonlinearity is obtained, and an amplitude-frequency characteristic curve is solved through a harmonic balance method and an arc length continuation method; monte Carlo simulation and Latin hypercube design are carried out, a multi-parameter Monte Carlo simulation analysis program is written, and parameter optimization analysis with the optimal damping effect of the damping device as the target is completed; and obtaining an optimal parameter group to further optimize the original damping structure. The model is processed through a substructure method, and the vibration response of the blade group with dry friction damping under simple harmonic excitation can be predicted.

The invention discloses a hypersonic aircraft control system limit cycle analysis method under steering engine nonlinearity. The method comprises the following steps: constructing a closed-loop control analysis model of a nonlinear link containing dead zone saturation characteristics and an equivalent transfer function; based on a harmonic balance method, representing input and output of a nonlinear link as Fourier series only containing odd harmonics, and establishing a balance relation of each harmonic to obtain a nonlinear equation set; and adaptive solving is carried out according to a system parameter scene, and limit cycle characteristic parameters are obtained. According to the method, time domain integral initial value dependence is avoided, higher harmonic lifting precision is considered, parameter uncertainty can be processed, and support is provided for aircraft control stability design.

An optimization method for sparse matrix-vector multiplication of multiple matrices with the same structure is applied to the iterative solution process of harmonic balance methods in radio frequency circuit simulation. The method includes: obtaining a first sparse matrix and a second sparse matrix of the circuit, wherein the first and second sparse matrices have the same structure and are used to characterize the nonlinear conductance and nonlinear capacitance characteristics of the circuit, respectively; in response to performing matrix-vector multiplication, in one traversal, simultaneously accessing the non-zero elements located at the same position in both the first and second sparse matrices, and performing multiplication and accumulation operations with the corresponding input vector elements to obtain the output vectors of the corresponding first and second sparse matrices; wherein the input vector is the harmonic component vector of the circuit node voltage. This invention, based on the combined access of multiple matrices with the same sparse structure, significantly reduces loop control overhead, thereby improving the overall efficiency of matrix-vector multiplication.

The invention provides a method and a device for predicting a fatigue safety coefficient. The method comprises the following steps: acquiring physical parameters, structural characteristic information, nonlinear factors and material fatigue attributes of a to-be-predicted mechanical system; based on the physical parameters, the structural characteristic information and the non-linear factors, constructing a non-dimensionalized non-linear multi-body dynamic model; simulating the non-dimensionalized nonlinear multi-body dynamic model through a harmonic balance method to obtain a system dynamic response; calculating stress-strain response data of a preset part in the to-be-predicted mechanical system based on the system dynamic response; and calculating a life prediction value of the preset part by using a preset life calculation expression in combination with the stress-strain response data and the material fatigue attribute. The nonlinear characteristics in the nonlinear multi-body dynamic model of the to-be-predicted mechanical system are accurately captured by using the harmonic balance method, the solving process is simplified, the calculation complexity and resource consumption are reduced, and the precision of fatigue life estimation is improved.

The application discloses a turbine damping blade dynamics design optimization method based on a convolutional neural network, comprising the following steps: obtaining a blade vibration reduction model, selecting model parameters and aerodynamic parameters to construct a characteristic space, calculating frequency response characteristics by using an arc length continuation method based on a multi-harmonic balance method, constructing a series of convolutional neural network models, normalizing characteristic parameters, frequency response characteristics and dynamic stress fields, and realizing vibration reduction performance optimization by combining automatic differentiation algorithms with characteristic prediction. The turbine damping blade dynamics design optimization method based on the convolutional neural network can realize accurate and rapid prediction of nonlinear response of the turbine damping blade, save calculation cost, improve solving efficiency, and obtain a friction damping structure scheme with the best vibration reduction effect in a given parameter working condition range, thereby providing theoretical support for dynamics design and optimization of turbine damping blades in engineering.

The invention belongs to the field of aero-acoustic numerical simulation, particularly discloses a frequency domain gust aero-acoustic response prediction method, and aims to solve the problems that an existing time domain method is low in calculation efficiency and a linear / nonlinear frequency domain method is insufficient in adaptability. The method comprises the following steps of: determining a control equation set comprising a continuity equation, a momentum equation and an energy equation, introducing a gust source item and a spongy layer source item, adding the source items into the control equation set, and solving by adopting a harmonic balance method; and converting to a frequency domain by combining sub-time-level sampling and discrete Fourier transform, adding a pseudo-time derivative item and carrying out implicit solution, and finally reconstructing to obtain an aerodynamic acoustic response. According to the method, time domain transition stage calculation is avoided, the low-frequency / long-period problem efficiency is improved, bounded gust is accurately simulated, and high-order harmonic solving resource consumption is reduced.