17 results about "Frequency periods" patented technology

The invention provides an aircraft cabin structure fault diagnosis method based on acoustic signals, and the method comprises the steps: obtaining a finite element model of an aircraft cabin structure, and calculating an acoustic response in a typical fault mode; acquiring a sound pressure level frequency response set, and forming an initial fault feature parameter set by using fault features in different frequency periods; utilizing a Gini coefficient gain algorithm to calculate the gain of the characteristic parameter component, and screening the initial fault characteristic parameter set to obtain an initial population; decoding the initial population to form a fault feature parameter subset, training a C4.5 decision tree and calculating individual fitness; iterating the initial population according to the fitness to obtain an optimal fault feature parameter subset and establishing a classification model; and establishing a to-be-detected characteristic parameter subset, identifying the to-be-detected characteristic parameters by using the classification model, and outputting the fault category and credibility of the to-be-detected characteristic parameters as a diagnosis result. According to the invention, a framework for diagnosing the aircraft cabin structure fault by using the acoustic signal is established, and the diagnosis precision is improved.

A method for operating a discharge lamp by modulating a current signal is presented. The discharge lamp is operated with at least two different frequencies. At first a probability distribution function for a first number of first frequency periods and a second number of second frequency periods is defined. Next, the first number of first frequency periods and the second number of second frequency periods are determined depending on the probability distribution function by at least one random number. The current signal is modulated by applying the first number of first frequency periods and the second number of second frequency periods to the current signal for operating the discharge lamp.

The present application relates to the technical field of laser radar, and especially relates to a non-aliasing frequency modulation continuous wave radar detection system and method, the non-aliasing frequency modulation continuous wave radar detection system comprising: a light source, a beam splitter, a circulator, a 90-degree frequency mixer, a signal conversion module and a signal processing unit, the signal processing unit being configured to: construct a complex vector signal S based on a first electrical signal I and a second electrical signal Q, S=I+jQ, wherein j is an imaginary operator, and obtain a double sideband spectrum based on the complex vector signal S, determine the frequency of a signal peak in an up-sweeping frequency period and the frequency of a signal peak in a down-sweeping frequency period in the double sideband spectrum, and obtain the distance and speed of a target to be detected based on the frequency of the signal peak in the up-sweeping frequency period and the frequency of the signal peak in the down-sweeping frequency period.The present application is at least beneficial to solve the signal aliasing problem when detecting the target to be detected.

This invention discloses an ADRC method for attenuating periodic disturbances in time-delay systems, belonging to the field of automatic control technology. The method includes: 1. Obtaining the controlled process model and disturbance frequency, and establishing an extended state model containing the periodic disturbance; 2. Constructing a reduced-order extended state observer and tuning the gain using the bandwidth parameter method; 3. Introducing a pure time-delay module into the observer's output channel to construct an ADRC structure; 4. Revealing the mechanism by which periodic disturbances in time-delay systems cannot be attenuated through two-degree-of-freedom equivalent transformation analysis; 5. Based on the frequency domain characteristic equation, analytically determining the delay of the time-delay module to achieve effective attenuation of periodic disturbances at specific frequencies. This invention solves the problem of attenuating periodic disturbances in time-delay systems without significantly increasing structural complexity. Compared to traditional schemes that require high-gain or complex prediction structures, this invention only requires adjusting the pure time delay of the observer's output channel, and the parameter tuning process is clear and intuitive, significantly lowering the threshold for engineering applications.

The invention discloses a servo control method based on low-frequency period similarity, which comprises the following steps: firstly, acquiring servo adjustment deviation of each sampling moment in a-1 optical disc rotation period through digital sampling, and then acquiring servo driving quantity of the moment in the-1 period based on a servo controller; according to the servo adjustment deviation and the servo driving amount of the adjacent moments in the-1 period, the increment value of low-frequency jitter of the optical disc at the moment in the period is obtained through a low-pass filter, and the actual servo driving amount at the moment t of the period is obtained by combining the servo driving amount at the moment t of the n period; and the position after servo drive adjustment at the moment t + 1 of the nth period is obtained, servo control based on low-frequency periodicity similarity is repeatedly executed in the optical disc rotation period, and finally the position after servo drive adjustment reaches the target position.

Method for monitoring a section (20) of a hydraulic pressure system (10), wherein a pressure of a fluid is built up in the section (20) by an upstream pump and wherein the fluid exits the section (20) via a valve (25) which opens with a valve control frequency and a duty cycle, characterized in that a pressure profile is detected by a pressure sensor (17) arranged downstream of the pump and upstream of the section (20) at least during one period of the valve control frequency, and that frequency components in the frequency spectrum of the pressure profile are determined by means of a Fourier transform.that if the frequency spectrum determined in this way matches the frequency spectrum of an intact subsection (20), it is concluded that the subsection (20) is intact, and that if the frequency spectrum determined in this way deviates from the frequency spectrum of an intact subsection (20), a defect in the subsection (20) is concluded, wherein the duty cycle of the opening valve (25) is changed from a first value to a second value, or that a period is considered in which the duty cycle changes, that local maxima of the frequency components in the frequency spectrum are determined, and that a defect in the subsection (20) is concluded if the amplitude of the local maxima decreases quasi-monotonic with increasing frequency.

The invention discloses a one-dimensional signal analysis method for a sweep-frequency series-parallel DFB array laser sensing system, and the method comprises the following steps: receiving a signal of the sweep-frequency series-parallel DFB array laser sensing system in a complete sweep-frequency period, the signal comprising a trigger signal and a data signal; reading a data signal in a complete frequency sweep period, and dividing the data signal into frequency sweep time periods corresponding to each lasing channel in the DFB array laser in a time domain; identifying and segmenting the frequency repeated overlapping part in the frequency sweeping time period of the adjacent lasing channels; processing the Mach-Zehnder interference signal by using Hilbert transform, and resampling the signal to be processed by taking the obtained phase change as a reference; and carrying out fast Fourier transform calculation, and analyzing one-dimensional distribution information of the measured object in the light reflection direction. According to the method, the problem of analysis signal distortion of the DFB array laser is solved, lossless extraction of returned information is realized, and a high-reduction-degree image is obtained.

This invention relates to the field of data processing technology, specifically to a data analysis-based intelligent operation and maintenance status detection method for generators. The method includes: monitoring and obtaining the horizontal and vertical decomposition curves of both the generator and the helicopter, and acquiring the relative acceleration of the helicopter at each moment; eliminating the influence of the relative acceleration on the horizontal decomposition curves of the helicopter and its generator to obtain the horizontal amplitude modulation curves of the helicopter and its generator; analyzing the frequency period invariance and the consistency of the frequency amplitude reduction ratio when helicopter vibration is transmitted to the generator to obtain the horizontal denoising decomposition curve of the generator; obtaining the vertical denoising decomposition curve of the generator; and fusing the horizontal and vertical denoising decomposition curves to perform operation and maintenance status detection on the generator. This invention aims to eliminate the vibration interference of the helicopter on the generator during operation and maintenance status detection, thereby improving the accuracy of operation and maintenance status detection.

The invention provides an active disturbance rejection control method and system for suppressing periodic disturbance of a permanent magnet synchronous motor, and relates to the technical field of motor control. According to the method, accurate estimation of the state and total disturbance of the system is realized by increasing the order of the extended state observer (ESO), and proportional estimation errors are introduced to change a disturbance feed-forward structure and eliminate control law gain in a disturbance transfer function, so that the difficulty in parameter adjustment is overcome, accurate disturbance observation and compensation are obtained, and the method is suitable for large-scale popularization and application. According to the method, the low and medium frequency periodic disturbance is better inhibited through the multi-frequency characteristic analysis, the change rule of the gain coefficient under the periodic disturbance of different frequencies is researched, and the gain coefficient is designed according to the change rule to inhibit the medium and high frequency periodic disturbance. The method can be applied to a permanent magnet synchronous motor high-precision servo system.

The present application belongs to the technical field of cleaning efficiency optimization, and specifically discloses an efficiency optimization method for cleaning offshore light buoys based on cavitation jet, which collects the ship attitude and the target distance between the nozzle and the light buoy in real time, samples the target distance sliding window to determine whether to trigger distance adjustment, identifies the wave main frequency period based on the attitude data when triggered, divides the wave main frequency period into phase intervals and extracts the phase angular velocity, locks the target distance adjustment phase window, predicts the wave displacement change trend in the window, matches the distance adjustment mode containing the action direction and the response speed mode, and finally generates the target distance adjustment operation instruction and outputs it to the display terminal of the ship operation management system. The present application can accurately lock the target distance adjustment opportunity, adaptively compensate the target distance fluctuation caused by the wave, thereby ensuring the stable collapse of the cavitation bubble, avoiding ineffective cleaning, and greatly improving the offshore light buoy cleaning operation efficiency.

The invention discloses a receiving circuit based on a pre-judgment structure and an operation method thereof, and belongs to the technical field of receiving circuits, and the receiving circuit comprises a hard decision circuit, a decision feedback equalization coefficient updating circuit and a pre-judgment decision feedback equalization circuit. The hard decision circuit generates a decision result and an error signal based on a filtering signal and a correction signal in a first frequency period. The operation method comprises the following steps: updating a group of filter coefficients according to the error signal of the first frequency period; and setting Z filter coefficients in the group of filter coefficients as 0. The pre-judgment decision feedback equalization circuit generates the correction signal corresponding to a second frequency period according to the group of filter coefficients. The second frequency period is later than the first frequency period.

The invention relates to the technical field of data processing, in particular to a generator intelligent operation and maintenance state detection method based on data analysis, which comprises the following steps: monitoring to obtain respective horizontal decomposition curves and vertical decomposition curves of a generator and a helicopter, and obtaining relative acceleration of the helicopter at each moment; eliminating the influence of the relative acceleration on the horizontal decomposition curve of the helicopter and the generator thereof, and obtaining a horizontal amplitude modulation curve of the helicopter and the generator thereof; analyzing the frequency period invariance and the amplitude decreasing proportion consistency of the frequency amplitude when the vibration of the helicopter is transmitted to the generator, and obtaining a horizontal denoising decomposition curve of the generator; obtaining a vertical denoising decomposition curve of the generator; and fusing the horizontal denoising decomposition curve and the vertical denoising decomposition curve, and carrying out operation and maintenance state detection on the generator. The invention aims to eliminate the vibration interference of the helicopter on the generator in the operation and maintenance state detection process of the generator and improve the operation and maintenance state detection accuracy.

The invention relates to measurement of a flow rate of a fluid. Transmitting and receiving a downstream first ultrasonic signal and a countercurrent second ultrasonic signal on a measurement path inclined relative to the flowing direction of the fluid, determining a first flight time of the first ultrasonic signal and a second flight time of the second ultrasonic signal, and determining the flow velocity according to the flight time difference, wherein the ultrasonic signal has a carrier frequency of a plurality of cycles, the amplitude of which is modulated in accordance with the envelope curve, the respective reception time for determining the time of flight is determined in accordance with selected oscillations of the ultrasonic signal, the oscillations being selected on the basis of the course of the envelope curve, in particular the maximum value of the envelope curve. A first difference between the first time-of-flight and a previously determined first time-of-flight and / or a second difference between the second time-of-flight and a previously determined second time-of-flight is calculated, and if the first and / or the second difference is an integer multiple of the carrier frequency period within a tolerance range, the carrier frequency period is determined. The first and / or second time of flight is corrected by an integer multiple of the carrier frequency period.

The invention discloses a multi-target track matching method based on time sequence backtracking, and relates to the technical field of avionics, and the method comprises the steps: carrying out the updating and storage of obtained low-frequency period target data and high-frequency period target data based on a cache elimination algorithm, and obtaining a low-frequency period target array and a high-frequency period target array; initial matching is carried out on the low-frequency periodic target array and the high-frequency periodic target array, and whether matching succeeds or not is judged by combining initial matching conditions; if the initial matching succeeds, performing backtracking matching on the low-frequency periodic target array and the high-frequency periodic target array after the initial matching succeeds, and judging whether the matching succeeds or not in combination with a backtracking matching condition; and if the backtracking matching is successful, performing data fusion on the high-frequency periodic target data and the low-frequency periodic target data which are successfully backtracked based on the confidence coefficient weight to obtain a target point track result. Through multi-stage matching and time sequence sampling, calculation resource increase caused by large high-frequency and low-frequency period difference is eliminated, and efficient and reliable track matching is achieved.

The application belongs to the field of laser ranging, and particularly relates to an absolute distance measurement method and device based on time delay interference, which comprises the following steps: introducing an arbitrary light source, first injecting a frequency modulation signal into the light source to prepare a frequency period jitter modulation note, then splitting the light with period jitter and injecting different frequencies, which are used to form heterodyne interference, one of the lights is used as reference light, the other light is processed twice by time delay, the reference light and the light processed by time delay are combined to realize twice heterodyne interference, and the first time delay processing contains distance information to be measured. The application uses the frequency period jitter modulation note of heterodyne interference light, combines the time delay interference method, calculates the time delay time, and calculates the absolute distance information contained in the time delay time, realizes low-cost and large-scale absolute distance measurement, and realizes the time delay interference algorithm, and the ranging reliability is high.

The embodiment of the present application provides a delta-sigma analog-to-digital converter, wherein the end point of the second reset signal (changed from logic true to logic false) received by the first non-delay component of the storage is more than one frequency period longer than the end point of the first reset signal received by other components (i.e. the reset time of the first non-delay component of the storage is longer than that of other components), so as to avoid the output of the first non-delay component of the storage from overshooting or surging. The delta-sigma analog-to-digital converter of the present application can maintain a good signal-to-noise ratio even if the internal components have low voltage swing limits.

This invention discloses a servo control method based on low-frequency period similarity. First, through digital sampling, the servo adjustment deviation at each sampling moment within the -1th optical disc rotation cycle is obtained. Then, based on the servo controller, the servo drive quantity at each moment within the -1th cycle is obtained. Based on the servo adjustment deviation and servo drive quantity at adjacent moments within the -1th cycle, the incremental value of the low-frequency jitter of the optical disc at each moment within the 1st cycle is obtained through a low-pass filter. This is then combined with the 1st... n cycle t The servo drive quantity at time t, obtain the t period. t The actual servo drive quantity at each moment, thus obtaining the first... n cycle t The servo drive adjusts the position at time +1, and then repeatedly executes servo control based on low-frequency periodicity similarity within the optical disc rotation cycle, eventually causing the servo drive to adjust the position to reach the target position.