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122results about How to "Reduce random noise" patented technology

Filtering techniques to remove noise from a periodic signal and Irms calculations

A signal filtering technique is designed to remove the effects of a periodic, low-frequency noise signal from a signal of interest. A signal waveform is sampled at different points of a number of consecutive periodic noise signal cycles and the collected samples are averaged to produce a corrected signal. The number of consecutive cycles in which samples are taken and averaged is inversely related to the signal amplitude such that as the signal level decreases, the number of cycles examined increases. The technique is particularly applicable to periodic signals associated with the output of Hall effect sensors in an electrical metrology environment. Improved RMS calculations are obtained for filtering low-frequency random noise from Hall sensors by averaging samples at different points of a signal cycle to create a composite desired signal cycle to facilitate other signal calculations. In a given electricity utility meter incorporating solid state circuitry, such metrology RMS calculations may be implemented in a metrology section of solid state devices provided on printed circuit boards, such as utilizing programmable integrated circuit components. By varying the number of cycles summed, the algorithm will adapt to amplitude changes more quickly. By using time averaged samples to filter random noise from the periodic signal of interest, the overall requirements for complex filtering is reduced. Instead, the technique relies on buffering and averaging synchronized samples for a given number of line cycles, so that by increasing the buffer size, larger numbers of line cycles can be accumulated and the filter cut-off frequency reduced.
Owner:ITRON

Measuring method for attitude angular velocity of spacecraft based on star sensor

The invention discloses a measuring method for an attitude angular velocity of a spacecraft based on a star sensor. The invention aims to solve the problem that the precision of a traditional method is seriously influenced by a measurement error of the star sensor. According to the technical scheme, the measuring method comprises the following steps of: reading a star map at an initial moment t0,thereby obtaining a measuring vector of the star sensor at t0 and navigating star information; supposing t=t0+deltat; reading the star map at the moment t; performing star point extraction and sequence star map identification, and numbering navigating stars simultaneously appearing in a previous frame map and a present frame map, thereby obtaining the total number n of the navigating stars simultaneously appearing at the moment of t minus deltat and t and a corresponding set omega1 of measuring vector pairs of the star sensor; initializing a Kalman filter, estimating the attitude angular velocity of the spacecraft and resetting an initial value of the filter; and supposing t=t+deltat, and repeating the steps of reading the star map at the moment t, performing star point extraction and sequence star map identification, numbering navigating stars and obtaining n and omega1. According to the measuring method, the influence of random noise of the measurement of the star sensor on the estimation of the attitude angular velocity can be eliminated and the measuring precision can be increased.
Owner:NAT UNIV OF DEFENSE TECH

Distance measurement method for power distribution network single-phase earth fault on the basis of aerial mode traveling wave mutation

The invention discloses a distance measurement method for a power distribution network single-phase earth fault on the basis of aerial mode traveling wave mutation. The method includes the following steps that (1) the same voltage pulse is simultaneously injected to three phases of a head end of a power distribution network, and voltage traveling waves returned from the three phases are detected; (2) the voltage traveling waves of each phase, which are obtained in the step (1), are transformed to modulus by a phase-mode transformation matrix, and further, aerial mode voltage traveling waves are obtained; (3) the aerial mode voltage traveling waves obtained in the step (2) are subjected to difference derivation to obtain first nonzero mutational point time, and thereby, travel time of the traveling waves can be obtained; (4) the travel time obtained in the step (3) is substituted into a distance measurement formula to obtain fault distance. According to the method, high voltage pulse is simultaneously injected to the three phases of the head end to detect aerial mode voltage traveling wave mutation so as to perform fault distance measurement, and thereby, the problem of fake fault points caused by unbalance three-phase loads of the distribution network is solved.
Owner:SICHUAN UNIV

Distance measurement method for power distribution network ground fault based on zero-mode travelling wave difference

A distance measurement method for a power distribution network ground fault based on the zero-mode travelling wave difference comprises the following steps: (A) injecting high voltage pulses into fault phases of the head end of a power distribution network, detecting voltage travelling waves returned by the three phases, and obtaining first zero-mode voltage travelling wave data with the voltage travelling waves returned by the three phases through phase-mode transformation; (B) injecting high voltage pulses consistent with the high voltage pulses in the step (A) into a certain healthy phase of the head end of the power distribution network, detecting travelling waves returned by the three phases, and obtaining second zero-mode voltage travelling wave data with the travelling waves returned by the three phases through phase-mode transformation; (C) conducting subtraction on the first zero-mode voltage travelling wave data obtained in the step (A) and the second zero-mode voltage travelling wave data obtained in the step (B) to obtain difference data; (D) conducting different derivation on the difference data obtained in the step (C) to obtain a first non-zero mutational site moment, and then obtaining propagation time of the travelling waves; (E) substituting the propagation time obtained in the step (D) into a distance measurement formula to obtain a fault distance.
Owner:SICHUAN UNIV
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