2305 results about "Natural frequency" patented technology

A power pick-up for an Inductively Coupled Power Transfer (ICPT) system is provided having a resonant pick up circuit. The natural frequency of the pick-up circuit may be varied by controlling the conductance or capacitance of a variable reactive in the resonant circuit. The load being supplied by the pick-up circuit is sensed, and the effective capacitance or inductance of the variable reactive component is controlled to vary the natural resonant frequency of the pick-up circuit to thereby control the power flow into the pick-up to satisfy the power required by the load.

The invention specifically relates to a mass tuned vibration reducer used for controlling the vibration of an aerobridge in the airport, a large-span pedestrian bridge, a port trestle, high-rise buildings and the related structures. The mass tuned vibration reducer comprises a mass block, a spring, a damper and a base; wherein, the spring can be a spiral spring, a disc spring or a plate spring, and the end part of the spring is provided with a rigidity regulating device. The mass tuned vibration reducer can successfully realize the regulation on the natural frequency of a TMD system under the condition of needing not to assemble and disassemble the TMD since the end part of the spring is provided with the rigidity regulating device, so as to simplify the difficulty of regulation work, avoid the waste of manpower and materials and greatly reduce the construction cost. Meanwhile, the natural frequency and the damping of the system can be regulated in an optimized way under the condition of needing not to assemble and disassemble the TMD, thereby better exerting the vibration absorption performance of the mass tuned vibration reducer, ensuring safety and stableness of the pedestrians and vehicles on the large-span bridge and the thin and high building, contributing to prolonging the service lives of the thin and high building and the bridge, and having remarkable economic and social benefits.

A flow measuring system is provided that provides at least one of a compensated mass flow rate measurement and a compensated density measurement. The flow measuring system includes a gas volume fraction meter in combination with a coriolis meter. The GVF meter measures acoustic pressures propagating through the fluids to measure the speed of sound α_mix propagating through the fluid to calculate at least gas volume fraction of the fluid and/or the reduced natural frequency. For determining an improved density for the coriolis meter, the calculated gas volume fraction and/or reduced frequency is provided to a processing unit. The improved density is determined using analytically derived or empirically derived density calibration models (or formulas derived therefore), which is a function of the measured natural frequency and at least one of the determined GVF, reduced frequency and speed of sound, or any combination thereof. The gas volume fraction (GVF) meter may include a sensing device having a plurality of strain-based or pressure sensors spaced axially along the pipe for measuring the acoustic pressures propagating through the flow.

The invention provides a numerical value simulation method of the vibration and acoustic characteristics of a speaker. The method comprises the following steps of: firstly, drawing a 3D (Three-Dimensional) geometric model diagram of the speaker by using 3D drawing software; then, adding the 3D geometric model diagram of the speaker to meshing software to mesh the 3D geometric model diagram into body elements, defining element types, materials and boundary conditions and applying a load to acquire a finite element model; establishing a boundary element model matched with the finite element model; and finally, solving the finite element model with a finite element solver to acquire the vibration characteristics of the speaker, and solving the boundary element model with a boundary element solver to acquire the acoustic characteristics of the speaker, wherein the vibration characteristics include the natural frequency, the vibration mode (vibration type), the displacement, the strain and the stress, and the acoustic characteristics include a frequency response curve and a directivity curve.

A micro-gyroscope (10) having closed loop output operation by a control voltage (V_ty), that is demodulated by a drive axis (x-axis) signal V_thx of the sense electrodes (S1, S2), providing Coriolis torque rebalance to prevent displacement of the micro-gyroscope (10) on the output axis (y-axis) V_thy˜0. Closed loop drive axis torque, V_tx maintains a constant drive axis amplitude signal, V_thx. The present invention provides independent alignment and tuning of the micro-gyroscope by using separate electrodes and electrostatic bias voltages to adjust alignment and tuning. A quadrature amplitude signal, or cross-axis transfer function peak amplitude is used to detect misalignment that is corrected to zero by an electrostatic bias voltage adjustment. The cross-axis transfer function is either V_thy/V_ty or V_tnx/V_tx. A quadrature signal noise level, or difference in natural frequencies estimated from measurements of the transfer functions is used to detect residual mistuning, that is corrected to zero by a second electrostatic bias voltage adjustment.

Multi-wing hovering and gliding flapping Micro Air Vehicles (“MAV”) are disclosed. The MAV can have independent wing control to provide enhance energy efficiency and high maneuverability. Power to each wing can be controlled separately by varying the amplitude of the wing flapping, the frequency of the wing flapping, or both. The flapping frequency can be controlled such that it is at or near the natural frequency of the wings for improved energy efficiency. The wings can be controlled by a gear train, coil-magnet arrangement or many other actuation systems that enable variable frequency flapping, variable amplitude flapping, or a combination of both. The gear train mechanism provides gyroscopic stability during flight. The wing flapping can include a rotation, or feathering motion, for improved efficiency. The wings can be transitioned between flapping flight and fixed wing flight to enable gliding and hovering in a single configuration.

A power generating system comprising a bluff (non-streamlined) body placed in a fluid stream at ninety degrees to the flow direction creates a von Karman vortex street behind the body. In the process, feedback forces are generated that excite the bluff body into oscillation. The bluff body oscillatory movements are coupled to and energize a power generator. Means are employed for electrically varying the natural frequency characteristics of the bluff body such that, over a relatively wide range of fluid flow velocities, the bluff body oscillates at a resonant frequency of the body for maximum energy transfer from the fluid stream to the bluff body.

Disclosed herein is an apparatus for evaluating the safety of a building. The apparatus includes first and second measurement instruments which measure earthquake accelerations of the top and bottom stories, a fast Fourier transform unit which performs fast Fourier transform on the earthquake accelerations, an integration unit which double-integrates the measured earthquake accelerations and creates drift data of the top story and the bottom story, a maximum inter-story drift ratio calculation unit which calculates a maximum inter-story drift ratio, a natural frequency change rate calculation unit which determines a natural frequency of the building, and compares the natural frequency with an ambient natural frequency of the building so as to calculate a natural frequency change rate, and a building safety evaluation unit which compares the maximum inter-story drift ratio and the frequency change rate with preset evaluation criteria and outputs a result of evaluation in the safety of the building.

The invention specifically relates to a mass tuned vibration reducer used for regulating the subsidence ratio of the vibration of the related structures. The mass tuned vibration reducer comprises a mass block, a spring, a damper and a base, and is characterized in that the damper is an adhesion-type damper formed by a damping cylinder, adhesive damping fluid and a piston, wherein, the piston and the adhesive damping fluid are arranged in the damping cylinder, and at least part of the piston is immerged into the adhesive damping fluid. The mass tuned vibration reducer adopts the adhesion-type damper formed by the adhesive damping fluid and the piston and can provide three dimensional damping, so as to effectively prevent side tumbling and ensure the vibration reducer realizes smooth actions; vibration mass is not needed to be provided with a special guide device, so that the mass tuned vibration reducer has reliable work and higher cost performance, and basically needs no maintenance. Meanwhile, the mass tuned vibration reducer realizes the aim of regulating the natural frequency and the subsidence ratio at any time, thus better exerting the vibration absorption performance of the mass tuned vibration reducer, ensuring stableness and safety of the pedestrians and vehicles on the large-span bridge and the thin and high building, contributing to prolonging the service lives of the thin and high building and the bridge, and having remarkable economic and social benefits.

Output-only modal testing of an object. Vibrations are excited in said object and measured by a number of vibration sensitive detectors. From the data of the measurements, a spectral density matrix function is determined. From this density matrix, auto spectral densities for the individual modes are identified performing a decomposition based on the Singular Value Decomposition technique. From the auto spectral densities of the individual modes, natural frequencies and damping ratios for the modes can be estimated, and from the singular vectors of the Singular Value Decomposition, the modes shapes can be estimated.

There is provided a golf club head that produces a loud hitting sound satisfying the golfer even if the volume of the golf club head having a hollow structure is increased to at least about 400 cc. A golf club head 1 having a hollow structure comprises a face part 2, a side part 3 comprising a back side, a sole part 4, a crown part 5, and a hosel part 9 having a shaft insertion hole, and the crown part 5. The crown part comprises a thick region 6 and a thin region 8. The thick region 6 extends through a distance W_A of at least about 20 mm from the center axis line C of the shaft insertion hole toward the highest point T of the crown part 5 and extends through a distance W_B of at least about 30 mm from the center axis line C of the shaft insertion hole toward the back side so that the crown part 5 has the first-order natural frequency of at least about 3000 Hz.

An acoustic resonance device is installed in a compartment of a vehicle so as to reduce a low-frequency sound pressure (or noise) dependent upon a natural vibration. Specifically, an acoustic resonance device is a panel/diaphragm resonator, a resonance pipe, or a Helmholtz resonator, the inner space of which communicates with the compartment via an opening. The acoustic resonance device is positioned in proximity to an antinode of sound pressure owing to a natural vibration occurring in a driver/passenger space inside the compartment. Alternatively, the acoustic resonance device increases a particle velocity at a specific natural frequency or decreases sound pressure at an excitation frequency which occurs due to an external condition of the vehicle. The acoustic resonance device can be installed in a roof, a seat, a pillar supporting the roof, or a door of a vehicle.

A control for a linear compressor energises the linear motor in harmony with the present natural frequency of the compressor. The controller monitors the present operating frequency and compares the frequency with one or more outer limit thresholds. The control may remove power from the linear motor if the running frequency drops below a lower threshold. The control may reduce power to the linear motor if the running frequency rises above an upper threshold. The control uses compressor running frequency to operate the comperssor within safe operating limits.

A tuning notch is defined preferably in the back of a blade root to tune the blade natural frequency in a gas turbine engine.

The present invention provides a high accuracy, inexpensive diagnosis method and system diagnosing an abnormality of a 10 rpm or less very low speed roller bearing using an acoustic signal, that is, detects an acoustic signal emitted from a roller bearing of a 10 rpm or less ultralow speed rotating machine using a sensor having a sound pickup performance of 10 kHz or less, uses frequency analysis to find the spectrum distribution, processes this to obtain the frequency analysis waveform, compares the spectral average value or effective value of a frequency of the natural frequency of the bearing or more of this with a reference value, and judges that the bearing is abnormal when this spectral average value or effective value exceeds the reference value.

The present invention relates to a piezoelectric energy harvester having a high energy transformation efficiency and a low natural frequency. The piezoelectric energy harvester includes an elastic substrate having a spiral spring structure, a first electrode formed on the elastomeric substrate, a piezoelectric film formed on the first electrode and a second electrode formed on the piezoelectric film.

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.