280 results about "Sinusoidal modulation" patented technology

An ac/ac converter for accepting a pulsating dc input with encoded sinusoidal modulation and providing a multiphase modulated output. The converter comprises a bridge including a plurality of switches having switch legs for modulating the pulsating dc input at a carrier frequency over a plurality of phases. The bridge is coupled at one end to a pulsating dc source and coupled at another end to a modulated signal output. A controller is provided for the plurality of switches for causing, for each of the plurality of phases, under unity power factor, one of the switch legs to modulate the pulsating dc input at the carrier frequency while the other switch legs do not modulate the pulsating dc input at the carrier frequency.

The invention discloses a high-adaptability three-dimensional measuring method based on color structured light in a three-dimensional scanning system. The method comprises the following steps of: coding according to the Gray coding principle by use of 6 pure colors; performing sinusoidal modulation of three components R, G and B at the same time to obtain a color grating for projection; designing an auxiliary grating according to the color grating; projecting the designed color grating and auxiliary grating to a measured object; performing superposition operation of the collected two grating deformation diagrams to obtain the reflectivity of each pixel; compensating the grating deformation diagrams according to the reflectivity of each pixel; performing color image division of the compensated grating deformation diagrams; decoding the divided image to obtain corresponding phase period information; graying the compensated grating deformation diagrams and obtaining the wrapped phase value of each pixel by Fourier transform; realizing phase unwrapping according to the decoded phase period information of each pixel; and finally, realizing three-dimensional reconstruction according to the corresponding relationship between the phase and the object height information.

Leakage current through stray or parasitic capacitance (which is particularly large in devices such as photovoltaic cell arrays and which are damaged by such leakage currents) due to common mode switching noise in a full bridge single phase power converter is reduced at high frequencies by magnetically coupling the two phase legs on the AC side of the power converter and connecting mid points of the AC and DC sides of the power converter and is reduced at low frequencies by use of a feedback arrangement that modifies sinusoidal modulation of the switches of the full bridge converter to function as an active filter. The magnetic coupling for the two phase legs is designed in a simple manner to avoid saturation based on volt-second considerations.

The invention relates to a control method for sharing voltage when inputting full load of an input-series-output-parallel combined converter. A sinusoidal modulation signal with a phase difference of Pi/n is increased on basis of the output signal vo_EA of a sharing output voltage regulator and the output signal vcd_EAi of each module input voltage-sharing regulator included in the drive signals of each input-series-output-parallel topology module control terminal. The increased sinusoidal modulation signal together with the signals vo_EA and vcd_EAi as a new error signal of each circuit is intersected with sawtooth waves VRAMPi inside a control chip to obtain a drive signal of each topology module switching tube, thereby controlling the ordered turn on and off of each topology module switching tube. The introduction of sinusoid with certain amplitude phase difference can obviously improve the problems that the duty cycle regulation space of some converter is lost and the problems caused by thereof when no-load or light-load. The control method of the invention has reasonable design, realizes the purposes of voltage-sharing and current-sharing under full load condition and is a control method with good stability and high reliability.

The invention relates to an optical fiber near-infrared spectrometer in the technical field of medical devices. The optical fiber near-infrared spectrometer uses multi-tail optical fiber collimator as light source optical fiber, uses a number lock technology as a technical scheme for weak signal extraction, uses a laser diode with a PD as a light source for sinusoidal modulation, uses an avalanche photodiode (APD) or photomultiplier tube (PMT) as a detector, and uses thick core-diameter plastic optical fiber, liquid-core optical fiber, silica optical fiber, a silica optical fiber bundle or glass optical fiber bundle as detection optical fiber. The invention has the advantages that the instrument can conduct nondestructive real-time hemodynamic parameter detection to biological tissues sheltered by hairs, the noise level of the instrument is low, the time resolution is high, the stability is high, the price is cheap, the hardware circuit design is greatly simplified and the portability of the instrument is realized.

The utility model discloses a method for testing the frequency properties of the photoelectric detector used for fiber optic gyroscopes. A signal generator produces sinusoidal signals and adds the signal to a light intensity modulator to carry out sinusoidal modulation on the optical power of the optical signal from the fiber source in order to produce an optical signal with sinusoidal components. The measured photodetector converts the modulated optical signal into an electrical signal and samples the electric signal by means of high-speed data acquisition card, then conducts narrowband filter and signal processing over the collected samples and calculates the corresponding frequency response. The frequency sequence pre-selected by a numerical control system changes the frequency at which the sine wave generator (NC) system sends out signals , tests a series of frequency point responses, which can be combined into an amplitude frequency response curve of the measured photodetector, and the curve is transmitted to the terminal computer for displaying and storage. By controlling all the test processes by numerical control system, the utility model has the advantages of automatic measurement, fast testing speed, high testing precision, and therefore is suitable for carefully weighing the photodetector frequency performance in the whole operating frequency range.

In thermography apparatus, a lamp 102 is modulated sinusoidally and a camera 106 captures thermal images at the modulated frequency, but delayed by an adjustable preset delay. A signal delay box 107 is connected between a sinusoidal modulation signal function generator 104 and the camera 106. The delay box introduces a delay to the function generator signal so that the thermal image is captured after a period of time, resulting in an enhanced image.

The invention discloses a fiber bragg grating low-frequency strain sensing demodulation system which comprises a narrow linewidth laser, an electro-optic/ acoustic optical modulator, a radio-frequency signal generator, an electro-optic phase modulator, a phase modulation signal generator, a coupler, a first fiber bragg grating sensor, a second fiber bragg grating sensor, a photoelectric detector, a data acquisition card and a strain demodulation module. The narrow linewidth laser provides a narrow linewidth laser source for the whole demodulation system, the electro-optic/ acoustic optical modulator modulates the laser source according to a chirp signal generated by the radio-frequency signal generator generating the chirp signal, and the electro-optic phase modulator performs phase modulation on the modulated laser source according to a sinusoidal modulation signal generated by the phase modulation signal generator generating the sinusoidal modulation signal. The coupler divides the laser source subjected to the phase modulation into two paths, the first fiber bragg grating sensor and the second fiber bragg grating sensor generate two paths of fiber bragg grating reflectance spectra under scanning of the two paths of the laser sources, the photoelectric detector performs photovoltaic conversion on the two paths of the fiber bragg grating reflectance spectra, the data acquisition card outputs two paths of optical fiber sensing digital signals, and the strain demodulation module is used for demodulating the two paths of the optical fiber sensing digital signals.

The invention discloses a super-surface color vector complex amplitude holographic element, which comprises a bimetallic nanorod unit structure with adjustable in-plane rotation angles and in-plane displacement, wherein an aluminum-silicon dioxide-aluminum super-structure grating structure generates a polarization-selective type diffraction efficiency enhancement effect in a visible light range; asum of in-plane displacement of two metal nanorods in the unit structure and diffraction phase information are in a linear modulation relationship, a difference between the rotation angles of the twometal nanorods and a diffraction light amplitude are in a sinusoidal modulation relationship, and a sum of the rotation angles of the two metal nanorods and a diffraction light polarization directionare in a linear modulation relationship; and a color holographic method is implemented on diffraction level by utilizing the phase displacement based on inherent dispersion of the super-structure grating. The super-surface color vector complex amplitude holographic element disclosed by the invention has the advantages of low requirements for preparation control precision, simple structure, high degree of control freedom and the like, and has powerful functions of simultaneously controlling four parameters of light wave phase, polarization, amplitude and frequency.

A system for detecting the eigen frequency of a sensing coil in a fiber optic gyro (FOG) that includes a fiber coupler connected to the light source, an integrated optics chip (IOC) capable of modulating light received from the light source via the fiber coupler, a sensing coil in communication with the IOC, a first modulation generator for imparting a first modulation signal to the light, and a photodetector for receiving light returning from the sensing coil that is representative of a rotation rate of the sensing coil. Along with the foregoing there is provided a second modulation generator for imparting a second, preferably sinusoidal, modulation signal to the light, a high-frequency demodulator in communication with a signal produced, at least indirectly, by the photodector, and a low-frequency demodulator in communication with the high-frequency demodulator. The high-frequency demodulator receives the first modulation signal as a reference frequency and the low-frequency demodulator receives the second modulation signal as a reference frequency. An output of the low-frequency demodulator represents a magnitude and sign of a frequency difference between a frequency of the second modulation signal and an even-harmonic of the eigen frequency.

A wavelength demodulation system with high resolution comprises a wavelength modulation sensor; a first 1 is multiplied by 2 coupler with the input end connected with the output end of the wavelength modulation sensor; a second 1 is multiplied by 2 coupler with the input end connected with the output end of the first 1 is multiplied by 2 coupler; a phase modulator with the input end connected with the output end of the first 1 is multiplied by 2 coupler and the output end connected with the input end of the second 1 is multiplied by 2 coupler; a photoelectric detector; a signal processing module connected between the second 1 is multiplied by 2 coupler and the photoelectric detector in series and used for demodulating a detected signal from an interference signal; and a sinusoidal signal generator with the output end connected with the phase modulator and the input end connected with the signal processing module and used for providing sinusoidal modulation signal from the phase modulator and the signal processing module.

The invention discloses a full digital five-level inverter sinusoidal pulse width modulation (SPWM) control method. In the method, a sinusoidal modulation waves are compared with four translation triangular carrier waves, and based on an asymmetric regular sampling principle and the comparison result, the switch-on and switch-off states of each switch device of a five-level inverter are completedin accordance with the rules. By the method, full digital control is realized, so that the five-level SPWM control response speed is higher, the pulse width control precision is higher, an output voltage has a lower harmonic content, the three-phase symmetry degree is more excellent, and a program can be conveniently and flexibly modified for meeting the requirements of various high performance control places.

The invention discloses a phase delay extraction and compensation method for PGC phase demodulation. A sinusoidal phase modulation interferometric signal is converted into a digital interferometric signal through an analog-to-digital converter after amplifying and filtering, first-order, second-order and fourth-order harmonics of the digital interferometric signal are subjected to orthogonal downmixing simultaneously, and three pairs of orthogonal harmonic amplitude signals are obtained. Phase delays are extracted from the three pairs of orthogonal harmonic amplitude signals, and corresponding phase delay correction coefficients are calculated out by using the phase delays. The phase delay correction coefficients are multiplied by the absolute harmonic amplitude signal equal to the sum ofthe absolute values of the orthogonal harmonic amplitude signals to obtain new harmonic amplitude signals which are not affected by the phase delays, and then a to-be-measured phase is obtained through antitangent operation. The problems are solved that in the PGC phase demodulation technology, phase delay is difficult to measure and non-linear errors caused by the phase delay are difficult to compensate for in real time, the phase measurement accuracy is improved, and the method is widely applied to the technical field of sinusoidal modulation interference.

The invention relates to a method and device of adopting dual wavelength structure light to measure object outline. It belongs to optical measurement technique field. The method includes the following steps: projector produces white light to make it irradiate to the object; the optical field is adjusted by the object; camera shoots the image. Its each image point phase difference is calculated by correlation method; the other wavelength is used to do sinusoidal modulation; the phase difference is gained as the same; twice sinusoidal modulation wavelength is combined to gain combination wavelength and combination phase difference; each image point depth is calculated. And it is un-envelope according to given continuity constraint condition to gain object actual three-dimensional shape. The device includes projector, camera, and computer. The invention has the advantages to good algorithmic stability and high measuring accuracy.

The invention provides a method and a device for PWM (pulse width modulation) of three-phase carrier waves. The method for PWM of the three-phase carrier waves comprises the steps of: producing sinusoidal modulation signals and three-wave carrier waves, wherein each phase of carrier waves of the three-phase carrier waves comprises two carrier waves which are stacked in the forward direction, and each two phases of carrier waves are provided with a phase difference with a preset phase angle therebetween; carrying out modulation on the sinusoidal modulation signals through the three-phase carrier waves, generating pulse width modulation (PWM) signals, and outputting the PWM signals to an electronic switch of an inverter so as to control on-off of the electronic switch. The method and the device provided by the embodiment of the invention for PWM of the three-phase carrier waves reduce common-mode voltage and common-mode leakage current outputted by the inverter, and improve the characteristic of electronic interference resistance of the inverter.

The invention discloses a full-speed-range composite strategy control method for a permanent magnet synchronous motor. The method comprises the following steps: respectively carrying out Clark transformation and Park transformation on an acquired phase current of the permanent magnet synchronous motor to obtain a synchronous rotation d-q coordinate system current value; injecting a high-frequencysignal into the direct axis of an estimated rotating coordinate system in a zero-low speed stage, and processing the converted phase current through an LPF and a BPF respectively; obtaining a fundamental component of the current signal through the LPF, and obtaining a high-frequency component of the current signal through the BPF; multiplying the high-frequency response by a sinusoidal modulationsignal, sending the multiplied high-frequency response to a position signal processor to obtain estimated feedback values of a rotating speed loop and a current loop, and generating a PWM signal through PI adjustment, Park inverse transformation and an SVPWM module, thereby realizing real-time control of the permanent magnet synchronous motor. According to the invention, no extra position sensor needs to be added, the control is accurate, the response speed is high, the robustness of the system is enhanced, and the control performance of the system is improved.

The invention discloses a method for measuring micro impulse by Doppler galvanometer sine-modulated multi-beam laser heterodyne second harmonic, relates to a method for measuring micro impulse and aims to solve the problems of low acquired laser difference frequency signal quality and low signal processing computing speed in the micro impulse measurement of conventional laser heterodyne methods. The method comprises the following steps of: exciting a working medium target to generate plasma jet to rotate a beam of a standard beam; starting a driving power supply of an H0 solid laser and a galvanometer, and causing the galvanometer to perform simple harmonic motion and modulate optical frequency incident to the front surface of the galvanometer at different moments under the action of the driving power supply; and continuously acquiring signals transmitted by an optoelectronic detector in the pendulum process of a torsional pendulum system, and processing all the continuously acquired signals to obtain the micro impulse to which the beam of the standard beam is subjected by using a signal processing system. The method has the prominent advantages of high acquired laser difference frequency signal quality and high signal processing computing speed.

The invention relates to a single-phase inversion frequency conversion power supply based on a sine modulation wave. The single-phase inversion frequency conversion power supply comprises an inversion circuit which is connected with an overtemperature and overcurrent protection circuit, a separation power driving circuit and a soft starting circuit; the soft starting circuit is connected with a soft starting control signal generation circuit and a rectification circuit; the rectification circuit is connected with a 220-volt alternating current input; the separation power driving circuit is connected with a driving signal generation circuit which is connected with the overtemperature and overcurrent protection circuit, a digital/analog (D/A) conversion circuit, a sawtooth carrier wave generation circuit and a dead-zone circuit; the D/A conversion circuit is connected with a data memory and a voltage negation circuit; the data memory is connected with a counter which is connected with the dead-zone circuit, a voltage control oscillator and the data memory; the voltage control oscillator is connected with a voltage regulator; and the voltage regulator is connected with the voltage negation circuit. The single-phase inversion frequency conversion power supply has the advantages of changing the frequency of the power supply according to a load requirement, effectively saving the power supply, reducing the volume of a system and greatly improving the reliability of the system.

The invention discloses a multi-power-supply gridconnected system control method based on a modularized multilevel convertor. The multi-power-supply gridconnected system control method comprises the following steps: the power control part of the modularized multilevel convertor generates a sinusoidal modulation wave; the sinusoidal modulated wave is sequentially subject to direct current supply control, an interphase circumfluence control and a gridconnected current direct current component inhibit control to superpose corresponding regulation value, and is finally subject to carrier wave dephasing SPWM modulation to generate a switch driving signal. The multi-power-supply gridconnected system control method can flexibly control the interphase circumfluence according to the operation state of the multi-power-supply gridconnected system.

The invention discloses a laser ranging method and a laser ranging device based on synchronous sampling and multiple phase measurement. A system sends out a starting signal so that a laser device driving unit generates a semicontinuous sinusoidal signal with period being integral multiples of a global clock, the semicontinuous sinusoidal signal is used for modulating intensity of emitted laser, echo light reflected by a target is converted into an electric signal and then sampled by an analog-to-digital converter driven by the global clock, and a modulation frequency and a sampling interval are in a homologous frequency multiplication relationship. Number of the global clocks between a rising edge of the starting signal to a previous moment of a first echo waveform sampling point is recorded to obtain a rough distance, the sampled digital waveforms are subjected to Fourier transform, phase difference between echo sinusoidal waveform to a previous moment of its arrival is obtained by utilizing frequency domain phase discrimination, multiple phase measurement is carried out on echoes after adopting oversampling and series decomposition to increase precision, the average of phase measurement results is converted into precise distance according to a sinusoidal modulation period, and distance information is derived by adding the rough distance to the precise distance. The laser ranging method and the laser ranging device have the advantages of being free of ranging distance limitation, easy hardware implementation and the like.

Since the prior-art is based upon analog circuitry, it uses sinusoidal frequency and/or amplitude modulation to simulate a rotating speaker at a reasonable cost. This invention uses a process based upon theoretically derived frequency modulation (FM) and experimentally measured amplitude modulation (AM) to simulate the rotating speaker. The main FM equation is based upon the Doppler effect and is equal to one over one plus a sinusoidal velocity coefficient. The main AM equation has a much narrower peak than sinusoidal modulation. This invention also contains several novel methods to control the angular velocity of the speakers, including changing the horn's speed dependent upon the original audio, modeling the speaker's acceleration to allow the physically realistic transitions between angular velocities, and adding noise to simulate natural variations in rotation. The digital apparatus that implements this invented process includes a digital processor and memory. In summary, the invented process is much more realistic sounding than prior-art.

The invention relates to a multi-target large powder inverter common-mode voltage suppressing method. A direct current component is superimposed on a traditional symmetrical sine-wave modulation signal to improve direct current voltage utilization ratio and a novel modulation signal is constructed on the basis of the superimposed direct current component to enable common-mod can be fully eliminated, reducing the harmonic content and improving the direct current voltage utilization ratio. By adopting the method to control a multi-level converter, since the switch status of the multi-level converter is limited in the zero common-mode voltage, the common-mode voltage of the inverter is enabled to be zero, the common-mode voltage can be fully eliminated, the harmonic content is reduced and the direct current voltage utilization ratio is also improved. The method has the advantages that the hardware circuit is not required to be added, the realization is simple and easy, the occupied internal memory is small and the generality is high. The method of the invention is suitable for any places in which large power multi-level converters are used, such as large power variable-frequency transmission systems and FACTS devices in power systems.