63 results about "Periodic perturbation" patented technology

The invention relates to a discrete sliding mode repetitive control method for a periodic servo system, which comprises the following steps: identifying a difference equation model of the current servo system, and converting the difference equation model into a state space model; selecting a linear switching function; forming a discrete reaching law, and constructing an ideal switching dynamic state according to the formed discrete reaching law; constructing a discrete sliding mode repetitive controller model according to the ideal switching dynamic state; and using current control variables as the control command for a controlled servo system to enable the servo system to change with reference signals. The invention can weaken the system chattering, and simultaneously inhibit the influence of periodic disturbance on the system, thereby improving the control quality and realizing the accurate control on periodic tracking tasks.

In a crystal growth method, a seed crystal 8 and a source material 4 are provided in spaced relation inside of a growth crucible 6. Starting conditions for the growth of a crystal 14 in the growth crucible 6 are then established therein. The starting conditions include: a suitable gas inside the growth crucible 6, a suitable pressure of the gas inside the growth crucible 6, and a suitable temperature in the growth crucible 6 that causes the source material 4 to sublimate and be transported via a temperature gradient in the growth crucible 6 to the seed crystal 8 where the sublimated source material precipitates. During growth of the crystal 14 inside the growth crucible 6, at least one of the following growth conditions are intermittently changed inside the growth crucible 6 a plurality of times: the gas in the growth crucible 6, the pressure of the gas in the growth crucible 6, and the temperature in the growth crucible 6.

The invention discloses a compound control method of a photovoltaic grid-connected inverter, relating to a photovoltaic grid-connected inverter. The control method of the traditional inverter has the defects of larger harmonic distortion of the output current of the inverter and poor wave form quality. The compound control method is characterized by comprising the steps of: detecting a DC busbar voltage and a three-phase current outputted by an inverter, calculating a d shaft current reference value according to the DC busbar voltage; converting the three-phase current output by the inverter into a d shaft current measured value and a q shaft current measured value; obtaining a current difference; respectively calculating according to the current difference to obtain a PI control voltage compensating value, a resonance control voltage compensating value and a repeating control voltage compensating value by a PI control module, a resonance control module and a repeating control module; and generating a PWM (Pulse Width Modulation) wave by the PWM control module according to a composition result of the PI control voltage compensating value, a resonance control voltage compensating value and a repeating control voltage compensating value. According to the invention, specific subharmonics and periodic disturbance are inhibited, stability of the inverter is ensured, and dynamic property of the inverter is improved.

The invention discloses a fractional periodic repetitive controller suitable for a position servo. The fractional periodic repetitive controller constructs a chattering-free attractive rule based on sine switching, further introduces a suppression idea of repetitive control on tracking and periodic disturbance of periodic signals, designs a fractional periodic repetitive control method based on the sine switching attractive rule according to fractional periodic symmetrical characteristics of disturbance signals in a time domain, and seeks a control sequence so that the output can track the periodic reference input accurately after limited control steps. The fractional periodic repetitive controller effectively suppresses the periodic disturbance at the same frequency of the reference position signals in the position servo system, and has good dynamic quality.

The invention discloses an online analyzing method for grid forced power oscillation caused by internal disturbance of a power plant and relates to the field of power system operation and control. The method is mainly used for judging whether the grid forced power oscillation is caused by internal periodical disturbance of the power plant. In actual operation of a grid, the forced power oscillation caused by generator disturbance is the most common oscillation mode, but whether grid oscillation is caused by the internal disturbance of the power plant where the grid is connected or by the disturbance at the grid end is difficult to judge directly through the characteristics of oscillation amplitude, frequency and the like. Therefore, the method is provided to identify measured data parameters of the power plant connected into grid nodes based on FFT (fast Fourier transform) and conduct energy flow phase difference analysis to judge whether the grid oscillation is caused by the internal disturbance of the power plant where the grid is connected. By means of the method, judgment can be conducted directly at a measuring terminal, and the method is simple in calculation and high in analyzing speed and has good actual application value.

The invention discloses a phase deviation based auto-disturbance rejection isolated island detecting method, which realizes periodic disturbance on the output current of an inverter by constructing an output current phase angle control function of the inverter so as to ensure that the voltage frequency of the position of a point of common coupling (PCC) deviates after the isolated island happens,and the occurrence of an isolated island phenomenon can be ensured to be effectively detected in time. The phase angle control function of the output current of the inverter consists of two parts, wherein one part is a homeostatic control function theta 0[k] which mainly plays roles in destroying a stable running point possibly existing in the system and ensuring effectiveness of disturbance, while the other part is a main function of the phase angle of the output current of the inverter which plays roles in ensuring that the method can effectively detect the isolated island when a secondary isolated island happens, and avoiding misjudgment caused by transient disturbance influence of the system, so that the normal operation of the system can be ensured. Therefore, compared with the priorart, the isolated island detecting method not only can avoid misjudgment caused by the effect of transient disturbance, and ensure the operation security of the system, but also can ensure that the isolated island can be quickly and accurately detected when the isolated island happens in an extremely hard condition, and greatly reduce the dead zone of detection.

This invention provides the controller of a synchronous motor. It realizes a low vibration and low noise variable speed drive by suppressing a periodic interference in a driver. When a load unit generates the periodic interference in the driver, it calculates the rotor position of an AC synchronous motor, and by means of detecting a rotating speed directly. The resolving method is that: A sensorless drive is realized by calculating a difference (axial error) between the position of the magnetic flux axis of the AC synchronous motor. The position of the magnetic flux axis assumed in a controller, and correcting the rotating speed, such that the difference becomes zero. Further, according to the calculated value of this axial error, and by means of compensating, it is performed by providing a means for extracting the pulsation component of the torque generated from the motor or the load unit

The invention provides a coaxial double-waveguide optical fiber capable of generating vortex light and a toroidal field, and a preparation method of the coaxial double-waveguide optical fiber. The optical fiber comprises a cladding layer 1, a central round less-mode fiber core 2, a spiral fiber core 3 and a toroidal fiber core 4, wherein the less-mode fiber core 2 is located in the center of the cladding layer 1; the spiral fiber core 3 surrounds the less-mode fiber core 2; and the toroidal fiber core 4 is overlapped with the axis of the less-mode fiber core 2. On one hand, due to periodic perturbation of the spiral fiber core 3, a low-order linear polarization mode (such as an LP11 mode 5) of transmission of the less-mode fiber core 2 can be converted into a high-order phase vortex mode,and a vortex light beam 6 is generated at an optical fiber end. On the other hand, when a Gaussian light field 7 (or the toroidal light field) is input to the toroidal fiber core 4 in a coupled manner, a toroidal transmission mode can be excited in the toroidal fiber core 4, and finally the toroidal light field 8 is output at the optical fiber end. The optical fiber can be prepared through a direct hot melting, rotating and wiredrawing method or a wiredrawing, hot melting and rotating method. The optical fiber can be applied to the fields of vortex light beam and toroidal light beam generationand transmission, optical communication, optical sensing, optical manipulation and the like.

The present invention discloses a GPU-based real time dynamic water surface analogy method. In the method, a FX effect document is compiled firstly; time-based periodic perturbation is added to each summit normal in the FX effect document, refraction and reflection vectors are calculated, and refraction veins and reflection veins are sampled to obtain a refraction color and a reflection color; subsequently, the refraction color and the reflection color are mixed by a simplified Fresnel mixed formulation; then a 3DS Max is used for establishing a pool model, the FX effect document is applied to the model as material, and each summit is endowed with normal by normal mapping. In the procedure, a scene is rendered into a frame cache and is used as refraction veins to be transferred to a GPU Shader; then a camera is changed to the position symmetrical with the waer surface; reflection veins are obtained by rendering again and are transferred to the GPU, thereby forming a dynamic water surface effect. The present invention uses the GPU technology to realize a dynamic water surface analogy arithmetic which can completely meet the real time requirement.

The invention belongs to the field of motor control, specifically a switch reluctance machine torque ripple control system and a control method therefor. The system comprises a delay controller, a hysteresis controller, a PWM output control device, an SRM (switch reluctance machine), a current detection device, a multiplexer, and a rotor position estimation device. The delay controller is connected with the hysteresis controller, the hysteresis controller is connected with the PWM output control device, and the PWM output control device is connected with the SRM. The SRM is connected with the SRM is connected with the current detection device and the multiplexer, and the multiplexer is connected with the rotor position estimation device. The rotor position estimation device is connected with the delay controller. Through the control of a radial force between adjacent poles of the SRM, the system employs the principle of torque recombination to effectively inhibit the periodic disturbance of the SRM, and solves a problem of motor system vibration caused by the torque ripple of the SRM in operation.

The invention belongs to the field of power system harmonic detection and treatment equipment performance test and relates to a full-function electric-energy quality comprehensive test platform. A control system structurally comprises a human-computer interface, a background workstation, an on-site workstation, a video monitoring workstation, a signal conditioning board, a control module and a relay protection device. A data acquisition card and a serial port card are inserted in the on-site workstation. The control module strategically applies IGBT (insulated gate bipolar transistor) controllable rectifying, a CPS (carrier phase shifted)-SPWM (sinusoidal pulse width modulation) multilevel PWM (pulse width modulation) strategy based on the CPS principle is selected, voltage feedforward control is added to an inverting side, and accordingly dynamic performance and stability precision are increased, and tracking error caused by periodic disturbance is eliminated by advanced repetitive learning control so that electric energy quality of an energy-taking power grid is free of influence in test process. By the aid of the test platform, voltage disturbance and current disturbance can be output respectively as well as simultaneously.In addition, the test platform can be converted according to test requirements and is highly practical.

The invention discloses a method for suppressing the rotation speed fluctuation of a PMSM based on iterative learning. The method can suppress the periodic pulsating torque of the PMSM and improve servo precision. The method is a motor control algorithm that compensate for torque ripple by using a PI learning law and attenuates non-periodic agitation error accumulation by introducing a forgettingfactor. The method comprises steps of: firstly establishing a transfer function model of an iterative learning controller to analyze its stability; then determining the convergence condition of the algorithm; and designing two important parameters, namely the learning gain and the forgetting factor, in consideration of the steady-state performance and dynamic response performance of the system. The method is simple and easy to implement, and can track the desired trajectory with high accuracy by learning the periodic deviation signal.

The embodiment of the invention discloses a supersonic wind tunnel testing apparatus capable of generating high-frequency downstream disturbance, which relates to the field of aerodynamics, and can solve a problem that the disturbance frequency of a counter-pressure mechanism of downstream pressure disturbance. The supersonic wind tunnel testing apparatus can also simulate various forms of downstream periodic disturbance with various frequencies, and a requirement of considering both conventional counter-pressure disturbance and high-frequency disturbance in a shock wave motion characteristic test is met. The supersonic wind tunnel testing apparatus comprises a spraying pipe section (1), an equal straight section (2), a cam spindle (3), a cam spindle driving power device (4), a flow channel connecting section (5), a closed cavity connecting section (6), a closed bearing supporting component (7), upper and lower side spraying pipe profiles (8), pressure measuring points (9), a schlieren observation window (10), a stepping motor and control system (11), a coupling (12), an inner supporting rod (13) and a ball bearing (14). The supersonic wind tunnel testing apparatus is applicable to a supersonic wind tunnel experiment in which high-frequency periodic disturbance is generated at the downstream.

The invention discloses a method and device for controlling quadrature voltage based on an IQ electro-optical modulator. The IQ electro-optical modulator adopts a double parallel Mach-Zehnder interferometer, and the method comprises the following steps of: enabling an I sub-modulator and a Q sub-modulator to output two paths of BPSK optical signal orthogonal waves, and modulating to QPSK optical signals; respectively overlapping small periodic disturbance of which the frequency is f1 and f2 on the optimum bias voltages of the I sub-modulator and the Q sub-modulator, wherein f1 is not equal to f2; obtaining low-speed AC small signals generated by the IQ electro-optical modulator under the small periodic disturbance and extracting f1+f2 sum frequency components in the small signals through a monitoring photodiode (MPD); overlapping small disturbance on the bias voltage of a pi/2 phase modulation electrode, and extracting the feedback waveform of the f1+f2 sum frequency components; and judging the amplitude and phase of the feedback waveform of the f1+f2 sum frequency components to adjust the bias voltage applied to the pi/2 phase modulation electrode. The method and device disclosed by the invention only adopt low-frequency package, and thus the reliability of the IQ electro-optical modulator can be increased, and the package cost can be reduced.

An apparatus to remove periodic disturbances in a recording medium having large eccentricity and deflection mass includes an actuator to change a position of a pickup in response to a combination of first and second compensation signals, an error detector to detect an error between positions actuator and the recording medium, a first compensator to receive the detected error and to output the first compensation signal that the actuator uses to actuate the pickup along the recording medium in upper and lower directions, and right and left directions; and a second compensator to output the second compensation signal from which the disturbance has been removed, to combine the compensated error and previous first and second compensation signals, and to filter the combined result at a predetermined bandwidth.

An apparatus and method of compensating for disturbances using learning control is provided. An optical recording medium drive servo system of an optical recording/reproducing apparatus, the system including an actuator for moving the position of a head for recording data on a recording medium or reproducing the recorded data from the recording medium, an error detector for detecting the difference between the reference position on the recording medium and the actual position of the head; a compensator for receiving a value from the error detector and producing a value for driving the actuator, a first memory for storing a control input for compensating for the position error of the actuator due to a periodic disturbance such as eccentricity, a second memory for converting the content of the first memory according to phase and storing the converted content, a timing controller for generating addresses for the first memory and addresses for the second memory according to phase, and an adder for applying the content of the first or second memory together with the output of the compensator to the actuator. Accordingly, a periodic disturbance component can be rapidly and effectively compensated for using a previously-learned control result regardless of a variation.

Where realtime performance-critical processing is executed in parallel with data integrity-critical processing, embodiments of the invention improve the realtime performance by raising the data transfer efficiency for sequential access-dominant realtime processing. In one embodiment, if a non-realtime processing command is received while read-ahead is in progress for a realtime processing command, processing of the non-realtime processing command is not started until a certain amount of data is cached. In addition, in order to prevent the periodicity disturbance of realtime processing, when the processing of the non-realtime processing command is postponed, the read-ahead is continued maximally until the timestamp at which the next realtime processing command is expected to be issued.

The invention discloses a boundary iterative control method of a marine flexible vertical pipe system based on the backstepping technology. The boundary iterative control method comprises the steps of: obtaining dynamic characteristics of the marine flexible vertical pipe system, and constructing a mathematical model of the marine flexible vertical pipe system according to the dynamic characteristics; constructing a boundary control method according to the mathematical model by using a backstepping method; designing a positive definite function, and discretizing the positive definite functionto obtain an iterative term in a discrete domain; designing a Lyapunov function, and converting the iterative term in the discrete domain into an iterative term in a continuous time domain; and combining the boundary control method with the iterative term in the continuous time domain to obtain a boundary iterative control method for suppressing the vibration of the marine flexible vertical pipe system. By adopting the boundary iterative control method disclosed by the invention, more accurate and stable tracking and control of a marine flexible vertical pipe can be realized, and the influenceof of external periodic disturbance on the system can be further inhibited by adding the iterative term.

In suppression of torque ripple with a periodic disturbance observer, adjustment of a gain portion is determined sequentially during monitoring operation of monitoring an operating condition. Therefore, many adjusting parameters are involved and achievement of correction is dependent on the skill of a person in charge of adjustment or design.

The periodic disturbance observer is provided with a model correcting means or section which calculates an error of an identification model by using a time difference quantity by an output of the periodic disturbance observer and a sensed value of a plant and corrects the identification model with the error of the identification model. Finally, the system performs the torque ripple suppression control with an accurately estimated periodic disturbance.

The invention discloses a device and a method for measuring disturbance of a cross flow fan impeller of a pulsed gas laser. The device and the method are mainly used for measuring the disturbance of the fan impeller. The device comprises an exploring laser light source, a beam expanding system, two spectroscopes, two reflecting mirrors, a photoelectric detector, a data acquisition unit and a processor, wherein the two spectroscopes and the two reflecting mirrors form a Mach-Zehnder interferometric system; the two spectroscopes are respectively arranged at both ends of a flow field area to be tested; the exploring laser light source, the beam expanding system and a first spectroscope are located on the same light path in sequence; and the photoelectric detector is located on the emergent light path of a second spectroscope. The method comprises the following steps: performing filtering on a signal, and then performing fast Fourier transform (FFT) treatment on the signal through controlling the data sampling frequency and the number of samples; converting a periodic disturbance signal of a time domain into a signal of a frequency domain to obtain a signal spectrum so as to determine the disturbance of the fan impeller. According to the device and the method disclosed by the invention, the disturbance information of fan rotation is obtained through an optical measurement mode. The device and the method have the characteristics that the measuring device is simple and is high in precision and convenient in operation and the method is very high in practical applicability.

An apparatus for accelerating a destruction of a vortex is formed at the rear of a wing of an aircraft by a merging of first and second co-rotating eddies. A perturbation device is disposed adjacent of an area of creation of the first co-rotating eddy. The device is configured to generate a periodic perturbation having a wavelength capable of exciting at least on instability mode of the first eddy.