4 results about "Propeller noise" patented technology

This invention relates to the field of passive underwater target identification technology, and in particular to a propeller noise cyclic coherent demodulation method based on an improved real-number genetic algorithm. Based on cyclic stationarity analysis theory, an optimal coherent weighted quadratic envelope spectrum is constructed by replacing the fixed integration frequency band with a weighting function, and an adaptive detection threshold is constructed based on the false alarm probability. The observed spectrum is modeled as the sum of harmonics and noise, and a sparse non-negative optimization problem is solved to extract the harmonics. Using the total harmonic intensity of the envelope spectrum as the cost function, an improved real-number genetic algorithm is used to optimize and search for the optimal weighting coefficient vector. The demodulated spectrum is obtained by coherently weighting and integrating the normalized cyclic modulation spectrum. This invention achieves autonomous allocation of weighting coefficients and adaptive selection of demodulation frequency bands, effectively improving the signal-to-noise ratio gain of cyclic demodulation, and is applicable to passive target identification in data backtracking and review systems.

This invention relates to a method and system for locating coaxial counter-rotating sound sources in rotorcraft, belonging to the technical field of sound source identification methods. It includes: processing the sound pressure signal of the moving sound source using continuous wavelet transform to obtain time-frequency domain variation results; performing Doppler effect correction based on experimental conditions; estimating the spatial location and relative intensity of the noise source using a cross-spectral matrix and weight vector; and performing phase-locked analysis of the rotor noise source intensity using a phase-locked averaging method. This invention differs from traditional time-domain delay superposition algorithms and frequency-domain cross-correlation spectrum methods. It can image unsteady sound sources using time-frequency domain characteristics, solving the acoustic imaging problem of counter-rotating propeller noise and possessing potential applications in the rotorcraft industry.

This invention relates to the field of ship design and propulsion technology, and discloses a catamaran and its control method. The catamaran includes a hull, with the width direction defined as the direction perpendicular to the catamaran's direction of travel in a horizontal plane. The hull includes a first hull and a second hull arranged symmetrically and at intervals along the width direction, with a channel formed between the first and second hulls along the width direction. It also includes a propulsion assembly disposed in the channel, comprising at least one fin adapted to oscillate to drive the catamaran's movement. This invention solves the problems of high propeller noise, cavitation, and difficulty in towing loads in related technologies for catamarans.

This invention discloses a method for simulating radiated noise signals from a counter-rotating propeller target, comprising: First, setting basic parameters of the counter-rotating propeller target, including simulation time, simulation harmonics, and signal-to-noise ratio (SNR). Second, setting signal parameters of the counter-rotating propeller target under stable navigation conditions, including noise fundamental frequency and frequency fluctuation variance, and setting signal parameters of the counter-rotating propeller target under maneuvering conditions, including maneuvering time and fundamental frequency increment. Third, generating signal frequency curves based on the signal parameters of the counter-rotating propeller target under stable navigation and maneuvering conditions. Fourth, calculating the signal phase point by point based on the counter-rotating propeller target signal frequency curves to generate a simulated counter-rotating propeller noise line spectrum signal. Fifth, adding noise according to the SNR and summing the results to generate a simulated counter-rotating propeller target noise signal. This method can accurately describe the time-varying frequency characteristics under different conditions, ensuring phase continuity and time-frequency consistency.