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1231 results about "Low frequency vibration" patented technology

Three-degree-of-freedom aerial photographic head with stable inertia

The invention discloses a three-degree-of-freedom aerial photographic head with the stable inertia, which comprises a stabilizer, a transmission device and a camera. The three-degree-of-freedom aerial photographic head with the stable inertia adopts a main principle that a mechanical gyro with the considerable inertia realizes stable shooting. A head bracket is connected with a horizontal rotating rack; the horizontal rotating rack is connected with the mechanical gyro to form the stabilizer; and the stabilizer is connected with the camera through the transmission device, so the synchronous movement of the gyro and the camera in the vertical direction can be realized and the stable shooting of the camera can be realized by the stability of the gyro. The three-degree-of-freedom aerial photographic head with the stable inertia can eliminate the influence of the high-frequency and low-frequency vibration of a plane on the aerial photographic images and the problem of image inclination which is caused by the inclination of the plane, can photograph very clear and stable images without any chattering removal treatment and has good application effects in aspects of line detection, fixed-point monitoring, aerial photograph and the like. The three-degree-of-freedom aerial photographic head with the stable inertia has novel design and strong stability and can meet requirements on most high-quality aerial photographs.
Owner:SZ DJI TECH CO LTD

Method and device for ultrasonic and nondestructive detection ofelasticity of viscoelastic medium

The invention relates to a method and a device for the ultrasonic and nondestructive detection of the elasticity of a viscoelastic medium, which belong to the technical field of nondestructive measurements. The method comprises the following steps of: using an ultrasonic probe to produce low-frequency vibration on a medium to be detected, emitting ultrasonic waves to the medium to be detected and acquiring an ultrasonic signal returned from the medium to be detected; selecting an ultrasonic signal range for calculating the elasticity of the medium to be detected; using the selected ultrasonic signal to calculate the transmission speed of an elastic wave produced by the low-frequency vibration in the medium and further calculating the medium elasticity according to the obtained transmission speed of the elastic wave. The device comprises an ultrasonic wave energy converter contact, a vibrator fixing the ultrasonic wave energy converter contact and a control device. In the method and device, motion compensation of the ultrasonic probe is not required, so that calculation time is shortened; meanwhile, position detection is carry out without a position sensor, so that the system complexity and cost are lowered.
Owner:BEIJING SONICEXPERT MEDICAL TECH CO LTD +1

Parallel mechanism based multidimensional vibration platform

ActiveCN104154170AAchieving Nonlinear StiffnessSolve the problem of isolating low frequencySpringsShock absorbersEngineeringUltra low frequency
The invention discloses a parallel mechanism based multidimensional vibration platform. Standard zero stiffness of a vibration isolation platform at the equilibrium position and nonlinear stiffness nearby the equilibrium position can be realized by setting certain structural parameters, and the problem about difficulty in isolating low-frequency or ultra-low-frequency vibration for a traditional linear vibration isolation system; stiffness and damping can be easily and conveniently adjusted, vibration isolation of broad frequency domains are satisfied, and good engineering applicability is achieved; the multidimensional vibration platform is high in bearing stiffness, low in movement stiffness, small in static deflection, low in dynamic inherent frequency and good in vibration isolation effect; inherent contradictions restricting the traditional vibration isolation system, namely the contradictions of low-frequency vibration transmissibility and high-frequency vibration attenuation, can be solved by flexible adjustment of the stiffness and damping; the height and the static equilibrium position of the entire platform can be changed by adjusting a shock absorber spring base in height, and the multidimensional vibration platform is applicable to vibration isolation of objects of different weight.
Owner:ANHUI UNIVERSITY OF TECHNOLOGY AND SCIENCE

Load-bearing adjustable zero-stiffness electromagnetic vibration isolator and control method thereof

InactiveCN102606673ALower natural frequencyAchieving vibration isolation over a wide range of frequenciesNon-rotating vibration suppressionIsolation effectEngineering
The invention discloses a load-bearing adjustable zero-stiffness electromagnetic vibration isolator and a control method thereof. An electromagnetic spring of the vibration isolator in the perpendicular direction is composed of three permanent magnets and two groups of controllable direct current electromagnets, two magnets have opposite polarity and generate repulsive force, and stiffness of theelectromagnetic spring can be adjusted by changing and controlling current. An electromagnetic spring of the vibration isolator in the horizontal direction is composed of two groups of symmetrically distributed electromagnetic springs, and stiffness of the electromagnetic spring can be adjusted by changing and controlling current. When the system load-bearing weight is changed, the stiffness of the perpendicular electromagnetic spring and the stiffness of the horizontal electromagnetic spring are led to meet a certain proportional relationship by adjusting and controlling current so that stiffness of the system at the balance position can be zero. When a vibration isolation device is in small vibration near the balance position, dynamic stiffness is very small, and natural frequency of the whole system is very low so that the vibration isolator can achieve wide-range frequency vibration isolation and has good low frequency vibration isolation effect. In addition, the vibration isolator is compact in structure, light in weight and convenient to control.
Owner:HUNAN UNIV

Stiffness-adjustable magnetic vibration isolator with quasi zero stiffness

The invention belongs to the technical field of vibration and noise control and relates to a relatively-high-applicability passive isolation technology for ultralow-frequency vibration. In order to effectively solve the problem between the low-frequency vibration transmissibility and the high-frequency vibration attenuation rate of the vibration isolator, the invention provides the stiffness-adjustable magnetic vibration isolator with quasi zero stiffness, which adopts rectangular permanent magnets generating negative stiffness and an elastic capsule providing positive stiffness; and when a load is changed, the working position of the elastic capsule is controlled unchanged, the positive stiffness of the elastic capsule is changed because the pressure inside the elastic capsule is changed, and then, the negative stiffness is matched with the positive stiffness through regulating the distance among the rectangular magnets, so that the stiffness-adjustable magnetic vibration isolator with quasi zero stiffness is adaptable to vibration isolation objects with different weights. The stiffness-adjustable magnetic vibration isolator with quasi zero stiffness is simple in structure, convenient to mount, adjustable in bearing capacity, excellent in vibration isolation property, compact in structure, light in weight and suitable for popularization and application.
Owner:NAVAL UNIV OF ENG PLA

Device and method for detecting pipeline closed cracks based on vibro-acoustic modulation technology

The invention relates to a device and a method for detecting pipeline closed cracks based on the vibro-acoustic modulation technology and belongs to the pipeline nondestructive testing field. The device provided by the invention comprises a computer, a first function generator, a second function generator, a first power amplifier, a second power amplifier, a vibration exciter, an accelerometer, acharge amplifier, a first thickness concertina-type piezoelectric ceramic sheet array and a second thickness concertina-type piezoelectric ceramic sheet array, an anti-aliasing filter and a data collection card. The method provided by the invention comprises the following steps of: acquiring a pipeline first-order bending vibration inherent frequency by swept frequency excitation; taking the frequency as the one of low-frequency vibration in the vibro-acoustic modulation detection; simultaneously exciting low-frequency bending vibration and high-frequency supersonic waves into the pipeline, determining whether there exists closed cracks inside the pipeline by the existence of frequency components which equal high frequency supersonic wave frequency subtracts or adds low frequency bending vibration frequency in a received signal frequency spectrogram. The device provided by the invention is utilized to solve the problem that it is hard to detect closed cracks by traditional methods, and can be applied to detect closed cracks in industrial pipelines.
Owner:BEIJING UNIV OF TECH

Symmetric rotation piezoelectric generation device

The invention discloses a symmetric rotation piezoelectric generation device which belongs to the technical field of micro energy and is particularly suitable for collecting varying rotation mechanical energy in a low-frequency vibration environment. The generation device consists of a rotation shaft, left and right bases, left and right bearings, left and right piezoelectric bi-crystal beam arrays, an excitation wheel permanent magnet array and an excitation wheel. The excitation wheel is in rigid connection with the rotation shaft; and the rotation shaft is supported in the center holes of the left and the right bases by the left and the right bearings respectively. In the generation device, the left and the right piezoelectric bi-crystal beam arrays are completely symmetric in structure. The excitation wheel permanent magnet array consisting of multiple excitation wheel permanent magnets is uniformly arranged at the periphery of the left side of the excitation wheel; each piezoelectric bi-crystal beam is composed of a permanent magnet block, a copper beam and a piezoelectric ceramic chip; and the piezoelectric bi-crystal beam array consisting of the left and the right piezoelectric bi-crystal beams is uniformly mounted on the left and the right bases. The device transfers the acting force by use of non-contact permanent magnetic force, thereby avoiding the energy loss and service life reduction caused by mechanical impact, and increasing the response bandwidth of a common rotation piezoelectric generation device.
Owner:DALIAN UNIV OF TECH

Measuring device and method for vibration of flexible cantilever on basis of machine vision

The invention discloses a measuring device and method for the vibration of a flexible cantilever on the basis of machine vision. The measuring device comprises a fixed bracket, the flexible cantilever, a camera bracket, a CCD (Charge Coupled Device) camera, a lens, a plurality of LED (Light-Emitting Diode) light-emitting tubes and a PC (Personal Computer), wherein one end of the flexible cantilever is fixed on the fixed bracket; all the LED light-emitting tubes are arranged on the upper surface of the flexible cantilever in sequence; the top of the fixed bracket is provided with the camera bracket; the CCD camera is fixed on the camera bracket and is provided with the lens; and an output port of the CCD camera is connected with the PC. The CCD camera measures each frame image of the vibration of the LED light-emitting tubes, and conveys the images to the PC; and the PC processes a detected image sequence, extracts the position of the mass center of the light spots of the LED light-emitting tubes and acquires the vibration displacement of all the LED light-emitting tubes and parameters for reflecting the low-frequency vibration of the flexible cantilever structure. The measuring device and method disclosed by the invention has the advantages that the non-contact effect is achieved, the measuring range is wide and the vibration characteristic of a measured object is not changed and the like, and can be widely applied.
Owner:NANJING UNIV OF SCI & TECH

Three-degree-of-freedom ultralow frequency vibration absorber

The invention provides a three-degree-of-freedom ultralow frequency vibration absorber which has a compact structure and belongs to the field of accurate vibration attenuation. The vibration absorber respectively utilizes the principle that the positive and negative rigidities are connected in parallel in three degrees of freedom to realize ultralow frequency vibration attenuation, greatly reduces the rigidity of the system on the premise of ensuring the bearing capacity of the system, and realizes the ultralow inherent frequency. The three-degree-of-freedom ultralow frequency vibration absorber adopts the manner that the magnetic positive rigidity and the magnetic negative rigidity are connected in parallel in the z direction and the manner that a flat spring and the magnetic negative rigidity are connected in parallel in the x direction and y direction, so that the integral structure is more compact, the ultralow inherent frequency is provided, excellent vibration attenuation effect is provided for medium-high frequency vibration interference, the low frequency vibration and the ultralow frequency vibration are effectively restrained, and the three-degree-of-freedom ultralow frequency vibration absorber is applicable to the accurate processing equipment and measuring equipment sensitive to vibrations.
Owner:HUAZHONG UNIV OF SCI & TECH

Low-frequency vibration-isolation combined sandwiched structure

The invention discloses a low-frequency vibration-isolation combined sandwiched structure. The low-frequency vibration-isolation combined sandwiched structure comprises a lower uniform layer, a middle layer and an upper uniform layer sequentially from bottom to top, wherein the middle layer is of a limited two-dimension photonic crystal structure, the limited two-dimension photonic crystal structure comprises a base body and a plurality of scatters embedded into the base body, the scatters are respectively connected with the upper uniform layer and the lower uniform layer into a whole, and the lower uniform layer, the scatters and the upper uniform layer (3) are all made of rubber materials. The scatters, the upper layer and the lower layer are combined into an integrated body and are made of the same materials. The base body needs to be fixed. The low-frequency vibration-isolation combined sandwiched structure can block incident vibration along a plate and low-frequency vibration perpendicular to the plate through the designed structure, be applied to vibration control within the frequency range of hundreds of hertz, and serve as a low-frequency vibration-isolation facility of projects such as foundations and inner walls of buildings, ships and warships, and high-speed rails.
Owner:XI AN JIAOTONG UNIV
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