15 results about "Limit cycle" patented technology

The invention discloses a combustion chamber nonlinear stability prediction method based on multi-input thermo-acoustic disturbance modeling. The method is used for evaluating thermo-acoustic stability of combustion chambers of aero-engines, gas turbines and the like. According to the method, geometric, operation and analysis parameters are input, and cooling flow distribution is calculated; solving an effective equivalence ratio, a heat release rate and a temperature field, and calculating an acoustic modal frequency; constructing an equivalence ratio and inlet flow double-disturbance MISO transfer function, and generating an FTF curve; and judging oscillation through a limit cycle detection algorithm, calling a Tanh / PowerLaw model to calculate a saturated heat release rate, and finally visually outputting a result. Multi-factor coupling accurate modeling is achieved, intervention can be conducted in the initial stage of design, calculation only needs several minutes, the prediction precision and efficiency are improved, the research and development cost is reduced, and the safety of the combustion chamber is guaranteed.

The invention discloses a shielded cable electricity testing method based on ground loop impedance potential lifting, and relates to the technical field of measurement. The electroscope comprises an electricity testing step, an induction electrode on the cambered surface of the electroscope is used for obtaining induced electricity, a broadband direct sampling framework is formed on the physical level, and broadband direct sampling of millivolt-level power frequency displacement current characteristics is achieved. Based on a variational mode decomposition-Duffing oscillator fusion weak signal extraction algorithm, a variational mode decomposition algorithm is utilized to adaptively strip broadband noise and higher harmonics, a reconstructed signal is subjected to scale normalization and then introduced into a critical chaotic state Duffing oscillator algorithm, phase transition of a phase track from a chaotic attractor to a large-scale limit cycle is monitored, and a weak signal is extracted. A non-linear dynamic weak signal extraction algorithm is formed on the algorithm level, and weak power frequency features masked by strong noise are accurately recognized; a broadband direct acquisition framework and a weak signal extraction algorithm form a dual detection framework, and a quasi-induction electric signal is detected and judged in the live part verification process of the shielded cable.

The application provides a transient synchronous stability dominant bifurcation mode identification method for an inverter grid-connected system, and relates to the field of power systems and their automation, and the steps of the method are as follows: obtaining inverter parameters and power parameters of the inverter grid-connected system and obtaining bifurcation equivalent parameters; based on a stable equilibrium point, obtaining a Hopf complex normal form coefficient real part and a normalized bifurcation parameter according to a generalized swing equation and the bifurcation equivalent parameters; obtaining a limit cycle amplitude according to the bifurcation equivalent parameters, the Hopf complex normal form coefficient real part and the normalized bifurcation parameter; obtaining a transient stability margin according to a geometric distance between a stable manifold at an unstable equilibrium point and the stable equilibrium point; and identifying a dominant bifurcation mode of the inverter grid-connected system according to the limit cycle amplitude and the transient stability margin. The method can effectively improve the efficiency and precision of transient synchronous instability mode identification, realizes quantitative evaluation of the stability margin, and provides accurate transient synchronous stability criteria for power systems.

The invention discloses a lower limb exoskeleton robot time-independent control method based on a vector field generator, and relates to the technical field of lower limb exoskeleton robot control, in particular to a lower limb exoskeleton robot time-independent control method based on the vector field generator, and the method comprises the steps: mapping a target periodic motion into a limit cycle in a phase space; constructing a vector field generator, and driving a system state error to be converged to zero by a stable item and a periodic adjustment item; designing a control law based on the exoskeleton kinetic model, wherein the control law comprises estimated values of an inertia matrix, a Coriolis force matrix, a gravity item and a friction item; a control law is applied to converge and stabilize the exoskeleton joint state in a time-independent manner at a target limit cycle. The method can adapt to gait rhythm changes and active intentions of a user, global asymptotic stability is ensured through a vector field, and a self-intersection track in a joint space is effectively processed.

The invention discloses an electric power spot day-ahead clearing method considering load increment declaration constraints, and relates to the technical field of electric power system operation decisions. The method comprises the following steps: acquiring declaration parameters to construct a boundary parameter set containing physical increase and decrease output variables, and fusing the boundary parameter set with an objective function and mutual exclusion constraints into a system state control matrix; discrete decision variables in the matrix are mapped into an energy physical model, and a lowest energy ground state solution is used as a unit and load combination state reference; and a dynamic evolution system containing a scheduling strategy and disturbance nodes is constructed, the dynamic evolution system is evolved to a stable limit cycle state in a phase space through the constraint of a differential equation set, and a final day-ahead clearing plan and a node marginal electricity price are generated. The method is used for solving the problems that a traditional algorithm is prone to falling into combinatorial explosion when processing massive discrete variables, and a static clearing model lacks dynamic evolution elasticity and a robust safety boundary when coping with high-dimensional continuous disturbance.

The invention belongs to the technical field of aeroelastic design and analysis of aircrafts, and particularly relates to an unsteady aerodynamic reduced-order model construction method and application based on a KAN network, and the method comprises the steps: firstly obtaining an aerodynamic response sample sequence of an aircraft in a limit cycle oscillation state; designing and filtering Gaussian white noise as an excitation signal, and obtaining high-precision aerodynamic data through fluid dynamics simulation; utilizing a linear subspace projection method to identify and obtain a linear state space model; a state estimation value of the linear model is used as input, a prediction residual error of the linear model is used as output, a KAN network is trained, and nonlinear mapping learned by the network is converted into an explicit mathematical expression through symbol regression; and finally, combining the linear state space model with an explicit nonlinear term to obtain a physically interpretable white-box aerodynamic force reduced-order model. According to the method, the defects that a traditional CFD method is high in calculation cost and has a neural network black box problem are overcome, and an effective tool is provided for aeroelastic mechanism analysis and optimization design.

The application discloses a kind of grid-connected virtual synchronous generator transient synchronization practical stability analysis method and system, belong to power grid technical field, method includes: establishing the grid-connected VSG disturbance system model of introducing lumped disturbance term, and the multiple uncertainty of parameter error, reference power fluctuation and grid operating condition change is uniformly represented in lumped disturbance term;Based on the boundary value of lumped disturbance term design deterministic comparison system, approximate representation disturbance system model;With comparison system as object, solve its unstable equilibrium point and deduce critical energy, make conservative estimate to the practical stability domain of disturbance system;Combined with Poincaré-Bendixson theorem determines the limit cycle position of comparison system and constructs equipotential surface, estimates the final boundary of the practical stability of disturbance system.The application also provides corresponding analysis system.The application improves the rigor and engineering practicability of stability analysis, and provides reliable basis for the safe and stable operation of grid-connected VSG.

The application provides a multi-machine parallel network type inverter communication-free fast power scheduling method. The method independently deploys a virtual oscillator controller with Andronov-Hopf oscillator as the core in each parallel inverter locally, and each inverter is interconnected without communication link; in the steady state, each machine relies on the nonlinear limit cycle dynamics of the virtual oscillator controller to realize power communication-free sharing through the common coupling point; when the inverter receives a scheduling instruction, the target steady-state phase angle difference is inversely solved based on the local impedance estimation, and an auxiliary reference state is generated, the phase of the main oscillator is continuously evolved to the target working condition through one-way phase traction, and a short-time compensation voltage is applied to compress the residual error of the physical circuit when the optimal switching trigger condition is met on the alpha-beta two axes; after the event is over, the local impedance estimation value is iteratively modified based on the active power residual error, and the scheduling unit is automatically exited according to the synchronization criterion.

The invention provides a transient synchronous stability dominant bifurcation mode identification method for an inverter grid-connected system, and relates to the field of power systems and automation thereof, and the method comprises the steps: obtaining inverter parameters and electric parameters of the inverter grid-connected system, and obtaining bifurcation equivalent parameters; based on the stable equilibrium point, according to a generalized wobble equation and the bifurcation equivalent parameter, obtaining a Hopf complex regular coefficient real part and a normalized bifurcation parameter; according to the bifurcation equivalent parameter, the Hopf complex regular coefficient real part and the normalized bifurcation parameter, obtaining a limit cycle amplitude; obtaining a transient stability margin according to the geometric distance between the stable manifold at the unstable equilibrium point and the stable equilibrium point; and identifying the dominant bifurcation mode of the inverter grid-connected system according to the limit cycle amplitude and the transient stability margin. The method can effectively improve the efficiency and precision of transient synchronization instability mode recognition, achieves the quantitative evaluation of the stability margin, and provides a precise transient synchronization stability criterion for a power system.

The invention belongs to the technical field of nonlinear dynamics and system control, and particularly relates to a projectile flight stability evaluation method based on Hopf bifurcation analysis. Establishing a nonlinear angular motion model of the pulse correction projectile; based on a pulse correction projectile nonlinear angular motion model, selecting interested aerodynamic parameters in a projectile nonlinear free motion stage or control parameters in a controlled flight stage as bifurcation control variables; calculating a system bifurcation point according to the bifurcation control variable, and judging a system bifurcation type based on a central manifold theorem and a normativity theory; calculating a limit cycle amplitude of the system according to the approximate equilibrium equation of the system; and evaluating the stability. Based on Hopf bifurcation analysis, the flight stability of the projectile can be accurately evaluated, the phenomenon of nonlinear flight sudden change instability is effectively avoided, and solid support is provided for aerodynamic design and guidance control process research of the projectile.

This application provides an attractor-based data augmentation method and system, belonging to the field of artificial intelligence technology. The invention acquires action data; based on the action data, it acquires pattern actions; based on the pattern actions, it determines equilibrium points or limit cycles, wherein for non-repetitive actions, a series of equilibrium points are determined, and for repetitive pattern actions, limit cycles are determined; based on the equilibrium points or limit cycles, it constructs dynamic equations, wherein the dynamic equations are divided into tangential and normal directions, representing the evolution of augmented data sampling points along the tangential and normal directions of the pattern actions, respectively; based on the dynamic equations, it completes data augmentation. This invention can effectively perform data augmentation, providing more diverse data support for imitation learning and effectively improving the efficiency and effectiveness of the pre-training stage.

The application discloses a combustion chamber nonlinear stability prediction method based on multi-input thermoacoustic disturbance modeling, which is used for evaluating the thermoacoustic stability of combustion chambers of aeroengines, gas turbines and the like. The method is characterized in that: geometric, operation and analysis parameters are input first, and then the cooling flow distribution is calculated; the effective equivalence ratio, the heat release rate and the temperature field are calculated, and the acoustic modal frequency is calculated; the MISO transfer function of the equivalence ratio and the inlet flow double disturbance is constructed, and the FTF curve is generated; the oscillation is determined through a limit cycle detection algorithm, the saturated heat release rate is calculated by calling the Tanh / PowerLaw model, and finally the results are visualized. The application realizes multi-factor coupling precise modeling, can be involved in the early stage of design, and only needs several minutes for calculation, so that the prediction accuracy and efficiency are improved, the research and development cost is reduced, and the safety of the combustion chamber is ensured.

This application proposes a method and system for predicting the nonlinear trend of thermoacoustic oscillations based on the flame transfer function. The method includes: real-time acquisition of inlet excitation fluctuation signals and heat release rate fluctuation signals of the combustion chamber; identification of the flame transfer function (FTF) based on the inlet excitation fluctuation signals and the heat release rate fluctuation signals; phase correction of the FTF to obtain the corrected real part of the FTF reflecting the internal dynamics of the flame; determination of the linear growth rate of the combustion system; processing of the heat release rate fluctuation signals to extract the steady-state amplitude information of the heat release rate fluctuation signals and determine the nonlinear saturation intensity of the combustion system; and determining whether the current state of the combustion system tends to develop into a stable limiting-loop thermoacoustic oscillation based on the linear growth rate and the nonlinear saturation intensity, and outputting a prediction conclusion. The technical solution proposed in this application can quickly and accurately predict whether the system will develop into destructive thermoacoustic oscillations based solely on online measurable combustion data.

The invention discloses a nonlinear control method and system for telescope shafting control, and belongs to the technical field of closed-loop control. According to the method, limit cycle oscillation caused by large friction is effectively inhibited through segmented error adjustment and output amplitude limiting. The method is based on position error dynamic adjustment control output, and the implementation mode is as follows: firstly, calculating the position error, and when the error exceeds a segmentation threshold value, adopting nonlinear adjustment (parameter adjustment); otherwise, outputting in proportion. And the output value is subjected to amplitude limiting processing to ensure that the speed is within a safe range. According to the method, the error peak-to-peak value and the root-mean-square value of sinusoidal signal tracking are remarkably reduced, meanwhile, the number of adjusting parameters is reduced, and engineering application is facilitated. The method is not only suitable for high-precision control of a telescope shaft system, but also can be popularized to other closed-loop control systems needing friction interference resistance.

The application discloses a kind of even super-elliptic limit ring path planning methods under structured environment, first obtain structured two-dimensional prior map, rectangular fitting is carried out to the obstacle in map and each rectangular parameter is extracted;Second, determine the current most influential obstacle to the target point, according to the set porosity, determine the rectangular circumscribed super-elliptic frequency, build rectangular obstacle envelope even super-ellipse;Then establish the local coordinate system associated with the terminal point and obstacle, determine the solving direction of limit ring and solve the even super-elliptic limit ring trajectory, solve the coordinates of the current limit ring escape point;Finally, judge whether there is an obstacle between escape point and terminal point, if there is, continue to solve even super-elliptic limit ring for the next obstacle, otherwise, solve the trajectory to reach the terminal point;The method is assisted by the advantage of even super-ellipse, while maintaining flexibility and smoothness, has higher map space utilization, shorter path planning length.