9 results about "Fourier spectrum" patented technology

This invention discloses a method, system, medium, and device for zero-speed detection of a wheeled robot. The method includes the following steps: acquiring inertial sensor data of the wheeled robot; selecting inertial sensor data based on a preset length sliding window, and calculating the modulus of the selected inertial sensor data to obtain one-dimensional inertial data; standardizing the one-dimensional inertial data; performing a discrete Fourier transform on the standardized data to obtain a Fourier spectrum; extracting time-domain feature data and frequency-domain feature data from the standardized data and the Fourier spectrum based on a preset one-dimensional convolutional neural network; and performing zero-speed detection on the time-domain feature data and frequency-domain feature data based on a preset fully connected neural network. Therefore, a high-performance zero-speed detection method that does not rely on a preset threshold is provided, improving the zero-speed detection capability of the wheeled robot in different motion modes and reducing the impact of engine and other component vibrations on the zero-speed detection effect when the robot is parked.

This invention provides a seismic intensity estimation system that can improve the accuracy of estimation when estimating the seismic intensity class based on the acceleration waveform obtained by the acceleration sensor of a smart device, while the smart device is placed on a stand on the floor. [Solution] The seismic intensity estimation system 1 includes: an acceleration waveform collection unit 23 that collects acceleration waveforms from each of a plurality of smart devices 10 during an earthquake; an acceleration waveform adjustment unit 24 that rotates the acceleration waveforms of the plurality of smart devices 10 so that their orientations in the horizontal plane coincide with each other to generate orientation-adjusted acceleration waveforms; a frame vibration characteristic derivation unit 25 that derives the vibration characteristics of at least one frame based on the orientation-adjusted acceleration waveforms of at least one pair of smart devices 10; and a floor seismic intensity class estimation unit 26 that derives the Fourier spectrum of the floor based on the acceleration waveform on the frame and the vibration characteristics of the frame to estimate the seismic intensity class of the floor.

The application provides a gravity acceleration measurement method and system based on YOLOv8, which comprises the following steps: labeling the pendulum position data in each picture in the pendulum picture data set to construct a corresponding pendulum labeling data set; taking the pendulum picture data set as the model input and synchronously taking the pendulum labeling data set as the label to train and fine-tune a preset YOLOv8 model to generate a corresponding pendulum detection model; based on the video frame rate and the video length, detecting the pendulum in the pendulum swing video through the pendulum detection model to output the center coordinates of the pendulum; normalizing the center coordinates of the pendulum and synchronously combining Fourier spectrum analysis to obtain the corresponding swing period, and calculating the corresponding gravity acceleration according to a preset formula and the swing period. The application can effectively improve the measurement accuracy.

This invention discloses a time series forecasting method based on a dynamic multi-period hierarchical interactive network, belonging to the field of time series forecasting technology. The invention constructs a time series forecasting model based on a dynamic multi-period hierarchical interactive network, selecting the top-k significant periods from the Fourier spectrum, constructing a master-slave hierarchical structure, and establishing structured associations between multiple period scales, thus solving the problems of independent branches and insufficient interaction in traditional multi-period modeling. Simultaneously, a bidirectional cross-scale periodic interactive attention module is designed, achieving parent-child period constraint-driven and sibling period information complementary fusion through directional guided attention and self-attention, respectively. Furthermore, a dual-factor driven adaptive period weight update strategy is proposed, dynamically adjusting weights based on the prediction span and data fluctuation factors to improve the flexibility and robustness of cross-period information fusion. This invention effectively improves the accuracy of existing time series forecasting on strongly periodic data and can be extended to multiple time series domains.

This invention discloses a method and system for extracting surface defects on semiconductor wafers using single-pixel imaging, relating to the field of wafer defect extraction technology. The method includes: performing dark current subtraction and brightness flat-field correction on a bright-field image of a defect-free wafer; generating a reference mask; dividing the image into tiles and establishing coordinate mapping; generating defect-sensitive pattern pairs; projecting them tile by tile and integrating them with a single-pixel detector; obtaining phase shift difference groups through complementary differential methods; demodulating the phase-locked loop (PLL) to obtain in-phase and quadrature components using a four-step phase-shifting method; estimating the global coordinates of the defect based on the phase and frequency slopes; and constructing a frequency domain suppression weight using the Fourier spectrum of the defect-free image to obtain saliency; and determining the defect type through adaptive adjustment of the distance between the output end and the tile and secondary differential saliency. This invention directly solves for the in-phase / quadrature components and amplitude-phase distribution using a four-step phase-shifting method, and obtains the defect coordinates using the phase-frequency slope, avoiding image reconstruction, reducing computational overhead, and improving positioning accuracy.

The maximum excitation force can be easily estimated based on the measured acceleration. [Solution] The method includes an acceleration measurement step for measuring the acceleration of a vibration-isolating floor 3 provided on a support structure 2 via a support spring 4 with its spring axis oriented vertically; a maximum acceleration calculation step for determining the maximum acceleration from the time series of accelerations; a primary natural frequency calculation step for determining the primary natural frequency from the Fourier spectrum of accelerations; a transfer function calculation step for determining the transfer function from the input excitation force of the vibration-isolating floor to the response acceleration; and a maximum excitation force calculation step for calculating the maximum excitation force from the maximum acceleration, primary natural frequency, and transfer function.

The present application relates to the field of scientific research and teaching instruments, and specifically provides a Fourier spectrum interferometer, which comprises, in sequence along an optical path, a light source, a collimating lens, an object plane, an imaging lens, a spectrum plane, a spectrum imaging lens and a receiver. The imaging lens converges object plane information on the focal plane of the imaging lens by laser, forming the spectrum of the object plane information, i.e. the first Fourier transform of the object plane information. When the spectrum imaging lens is inserted into the optical path, the spectrum image of the spectrum plane is observed on the receiver. When the spectrum imaging lens is removed from the optical path, the light rays of the spectrum target plane or the gating sheet interfere at the receiver position, i.e. the second Fourier transform of the object plane information, displaying the optical image of the object plane. The present application can quickly switch the spectrum imaging lens to observe the two Fourier transforms of the optical system, and demonstrate the results of diffraction, interference and optical frequency multiplication through specific spectrum, facilitating a deep understanding of the principle of optical information transmission.

The application discloses a kind of high mountain and valley site seismic time history simulation method and system, belong to geotechnical earthquake engineering technical field, including the following steps: numerical integration solution;Fast Fourier transform (FFT);Amplification factor solution;Fourier spectrum adjustment;Inverse fast Fourier transform (IFFT);Numerical differentiation solution.The application adopts fast Fourier transform (FFT) to efficiently convert seismic input signal into frequency domain Fourier spectrum, multiply it with displacement amplitude transfer function to obtain Fourier spectrum considering valley topographic effect, reconstructs time domain response based on inverse fast Fourier transform (IFFT), provides an efficient, accurate and engineering generalization scheme for valley topographic effect analysis;Frequency domain processing avoids the discrete error of time domain numerical integration or differentiation, accurately retains the frequency domain characteristics of seismic motion by directly calculating the Fourier spectrum considering topographic amplification effect, ensures the authenticity of topographic amplification effect.

This invention discloses a single-pixel imaging method based on adaptive Fourier spectrum sampling and fast iterative adaptive reconstruction. By adaptively sampling low-frequency and important high-frequency spectra, the number of samplings is minimized while improving image quality. The obtained sampled spectra are solved using an image sparse prior and an alternating direction method is introduced in the gradient space. A fast Fourier transform is also introduced to accelerate the solution process, significantly reducing computational complexity and solving the problems of slow imaging and poor real-time performance in traditional single-pixel imaging methods. This single-pixel imaging method can quickly obtain high-quality images, solving the problem of high-quality and fast imaging under conditions of slow spatial light modulator modulation frequency and low sampling rate. It has wide application value in terahertz imaging, infrared imaging, single-photon imaging, and X-ray imaging.