315 results about "Stiffness coefficient" patented technology

A robotic system for steering a flexible needle during insertion into soft-tissue using imaging to determine the needle position. The control system calculates a needle tip trajectory that hits the desired target while avoiding potentially dangerous obstacles en route. Using an inverse kinematics algorithm, the maneuvers required of the needle base to cause the tip to follow this trajectory are calculated, such that the robot can perform controlled needle insertion. The insertion of a flexible needle into a deformable tissue is modeled as a linear beam supported by virtual springs, where the stiffness coefficients of the springs varies along the needle. The forward and inverse kinematics of the needle are solved analytically, enabling both path planning and correction in real-time. The needle shape is detected by image processing performed on fluoroscopic images. The stiffness properties of the tissue are calculated from the measured shape of the needle.

A bracket includes a rigid member that can be fastened to a fixture such as a wall, and flexible elements depend downwardly from the rigid member and are engaged with a tubular motor assembly of a window covering, awning, projector screen, or the like, to couple the motor assembly to the fixture while attenuating the propagation of vibrations from the tubular motor assembly to the fixture. This reduces noise in the room. The flexible elements may be flexible strings, elastic strings, or coil springs and have horizontal stiffness coefficients much lower than the vertical stiffness coefficient.

A computer-implemented method for pseudo acoustic quasi-P wave propagation which remain stable in anisotropic media with variable tilt and is not limited to weak anisotropic conditions. The method includes acquiring a seismic exploration volume for a subsurface region of interest, and determining a modeling geometry for the seismic exploration volume. The method further includes propagating at least one wavefield through the seismic exploration volume utilizing the modeling geometry and initial conditions and preventing the accumulation of energy along the axis of symmetry of the seismic exploration volume and ensuring positive stiffness coefficients in the stress-strain relations through the use of finite quasi-S wave velocities thereby producing a stable wavefield. The method includes utilizing the stable wavefield to generate subsurface images of the subsurface region of interest.

Spinal modeling is based on a concept called spinal energy which assumes that the spine assumes a shape to minimize spinal energy. Spinal energy depends on parameters called stiffness coefficients. These parameters can be determined from human data which, by hypothesis, are universal for a large class of humans. The method adapts Newton's method to the manifold SO(3)<n >to find a solution of model of the human spine. Where basins of attraction are small in Newton's method, homotopy methods are introduced to move from known solutions to unknown solutions. By setting the gradient of the spinal energy to zero, Newton's method is used to solve the inverse problem of finding stiffness coefficients from human data. A new approach to improving deformed spines uses the modeling method based on spinal energy. This approach preserves maximally the range of motion of the spine. The technique used is vertebraplasty; i.e., adding and/or subtracting material surgically from various vertebral bodies without fusing or altering soft tissue. An interactive process is used to determine the surgery to be performed to improve spinal shape.

The invention provides a voice coil motor for drives a liquid lens and a lens assembly with the voice coil motor. The voice coil motor comprises a number of sub-motor parts which are independently controllable. Each sub-motor part comprises a fixed part, a movable part movable relative to the fixed part along the optical axis direction, and a connection elastic piece which is connected with the liquid lens and the movable part. The movable part drives the connection elastic piece to press the liquid lens when the movable part is subjected to a force in the optical axis direction. The connection elastic piece is a leaf spring, and the stiffness coefficient in the optical axis direction is greater than the stiffness coefficient of the connection elastic piece in a direction perpendicular tothe optical axis. The voice coil motor further comprises a driving circuit part which controls the moving distance of the movable part. The voice coil motor provided by the technical scheme can accurately achieve autofocus and optical anti-vibration of the liquid lens at the same time.

Provided are a seismic control bearing device capable of absorbing and/or blocking vibration energy transmitted to structures due to earthquakes, and so on, as well as actively controlling various dynamic behaviors generated from the structures with low power and without additional equipment, and a seismic control system including the same. The seismic control bearing device is installed between a ground base and a structure constructed on the ground base to reduce vibration energy applied to the structure, and includes a plurality of deposition members spaced apart from each other; and a plurality of magneto-sensitive members disposed between the deposition members and formed of a magneto-sensitive material. The properties including a stiffness coefficient and an damping coefficient of the magneto-sensitive material are varied depending on a variation of a magnetic field formed around the magneto-sensitive member.

The invention belongs to the technical field of fluid and structure, and discloses an elastic cylinder vortex-induced vibration rule and coupling mechanism determination method. According to the method, rules of influence to dynamic flow field, vortex shedding frequency, dynamic vortex distribution, stability and vortex-induced vibration of elastic are determined as well as unsteady aerodynamic force interference characteristic and coupling mechanism between flapping wings and the elastic-vibration cylinders by analyzing unsteady aerodynamic force characteristics, flow field variation, vortexshedding frequency and vortex shedding structure distribution rule of the flapping wings. The dynamic fluid characteristics, vortex shedding frequency and vortex shedding structure distribution rule of the flapping wings under variation of parameters such as different flapping angle, flapping frequency and Reynolds number is defined; the vortex-induced vibration vibration rule and coupling mechanism of the elastic cylinders under different flapping angle, flapping frequency, mass ratio, damping ratio, spring stiffness coefficient, flow parameters under different degrees of freedom, and dynamicvortex distribution parameter along with motion of the flapping wings is determined.

The invention discloses a simulation device for vortex-induced vibration of a submarine pipeline and an experimental method. The simulation device comprises a water tank, a rectangular support frame, a pipeline model movement mechanism and a test system. The support frame is set up on the water tank. The pipeline model movement mechanism includes a simulation pipeline, two linear guide rails and a cross bar which constitute a rectangle. The two linear guide rails are mounted on the support frame respectively through guide rail blocks, and the cross bar is arranged on the top and connected to an upper beam of the support frame by means of two main springs. Test instruments in the test system are installed and then connected with a control host. The vortex-induced vibration of the pipeline under controllable damping can be simulated for the structure by installing a damping control device. When an experiment is carried out by the device, the instrument is calibrated first, and the damping coefficient of a free vibration system and the stiffness coefficient of the springs are measured by the device in a water injecting experiment. The device can be used to systematically study the vortex vibration trigger and amplitude and other issues, and the results can be referred to in the engineering design of a submarine pipeline.

The invention discloses a quasi-zero-stiffness vibration isolator with a horizontal damper. Two sets of cam-roller-spring mechanisms are horizontally and symmetrically arranged to serve as a negativestiffness structure, the horizontal damper is additionally arranged, and then the negative stiffness structure, the horizontal damper and a vertical positive stiffness spring structure are connected in parallel to form a quasi-zero-stiffness vibration isolation mechanism jointly. The matched stiffness coefficients of vertical springs and horizontal springs are selected, the height of cams and thepre-compression amount of the horizontal springs are adjusted according to the mass of an object subjected to vibration isolation and the stiffness of the vertical springs, the centers of the cam androllers are made horizontally flush, and the system has the quasi-zero-stiffness feature at the balanced position. On the basis of the certain vertical damping, the horizontal damping of the system isreasonably designed, and the resonance phenomenon of the system can be restrained or even eliminated. The vibration isolator has the high-static and low-movable stiffness feature, can achieve low-frequency vibration isolation, is simple in structure and convenient to maintain, and can be widely applied to low-frequency vibration management projects.

In a first aspect, a tensioner is provided which includes: an arm, including a pivot mount; a pulley rotatably mounted to the arm; and a strut pivotally connected to the arm. The strut includes: a base, having a pivot mount; a first body moveable relative to the base; a first resilient element connected between the base and the first body, the first resilient element having a first stiffness coefficient; a second body moveable relative to the first body, the second body having a pivot mount; a second resilient element connected between the first body and the second body, the second resilient element having a second stiffness coefficient that is lower than the first stiffness coefficient; and an actuator, connected to the base and first body, for selectively moving the first body towards the base and compressing the first resilient element.

The invention relates to a design method for stiffness matching and diameter of vehicle suspension stabilizer bars and belongs to the technical field of vehicle suspensions, aiming to fill a gap of the reliable optimal design method for diameter of the stabilizer bars due to limitation of radial deformation analytic analysis and inter-coupling of the stabilizer bars and rubber bushings. The design method is characterized by including the steps of firstly, performing matching design on stiffness of angle of roll of a front suspension stabilizer bar system and a rear suspension stabilizer bar system according to vehicle parameters and roll models; secondly, building an optimal design mathematical model of the stabilizer bar diameter d according to the matching design value of stiffness of the angle of roll, the radial stiffness coefficient Kx of the rubber bushings and the deformation coefficient expression Gw of ends of the stabilizer bars so as to obtain the accurate and reliable optimal design value of the stabilizer bar diameter d by means of a Matlab program. By the design method, design level and performance of the suspensions and the stabilizer bars can be improved, riding comfort and safety of vehicles can be improved, and meanwhile, design speed for product development can be increased and cost for design and test can be reduced.

The invention discloses a preparation method of a graphene/aluminum composite material. The preparation method specifically includes the following steps that graphene oxide powder is evenly dispersed in an alcohol solution, and a graphene oxide alcoholic solution is prepared after emulsification and ultrasonic treatment; aluminum powder is slowly added under stirring, temperature is controlled to be not higher than room temperature, stirring speed is controlled to be 100-1000 r/min, stirring time lasts for 1-5 h, and the uniform graphene oxide alcoholic solution containing the aluminum powder is obtained; solid and liquid separation is performed through the filtering technology and the centrifugal technology, and graphene oxide/aluminum dry powder is obtained after separated paste solid is frozen and dried; and the dry powder is subjected to heat reduction under Ar/H2 mixed atmosphere, and finally the graphene/aluminum composite material is prepared. The graphene/aluminum composite material prepared through the method has the beneficial effects of being high in strength, low in heat expansion coefficient and the like, and the specific stiffness coefficient and the special strength coefficient are remarkably increased. The method is simple in technology and efficient, industrialized production and application can be easily achieved.

The invention discloses a method for determining elastic energy of a circular film under condition that maximum deflection is limited by elasticity. The method comprises the following steps of: applying a uniform load q to a circular film with a Young's modulus of E, a Poisson's ratio of v, a thickness of h, a radius of a, and a self-weight of q0 per unit area, which is initially flat and fixedlyclamped at the periphery, to enable the circular film to produce axisymmetric deformation; pushing a rigid circular plate which has a radius of a and a center on the same axis as the center of the circular film, is always parallel to the circular film which is flat at the middle, and has a smooth surface to move a distance of wm in parallel; forming an contact area with a radius b between the axisymmetrically deformed circular film and the rigid circular plate; compressing a spring having a stiffness coefficient of k from the original length L by wm by the parallelly moving rigid circular plate; and after ignoring the self-weight of the rigid circular plate, using the measured value of the load q to determine the elastic energy U of the axisymmetrically deformed circular film based on a static balance analysis of the axisymmetrically deformed circular film.

The invention provides a piezoresistive acceleration sensor and a manufacturing method thereof. The sensor is improved by comprising a sensitive structure part. The left and right sides of a mass block in the sensitive structure are symmetrically provided with four mutually independent sensitive girders. Each sensitive girder is provided with a force-sensitive resistor. The two sides of the four sensitive girders are respectively provided with one support girder for supporting the mass block. The force-sensitive resistors are arranged on the mutually independent sensitive girders, so that the widths of the sensitive girders are reduced. Therefore, the influence of the sensitive girders on the stiffness coefficient of the sensitive structure is significantly reduced, so that the high sensitivity and the high figure of merit are realized. The sensitive girders are arranged closer to the centerline of the mass block, thus being smaller in deflection. The paraxial sensitivity is reduced. The support girders are closer to the edge of the mass block, thus being large in the arm of force. Therefore, the twist of the mass block, caused by the paraxial acceleration, can be better inhibited. The upper surfaces of the support girders are lower and are free of any oxidation layer. Therefore, the structural deflection, caused by the stress of the oxidation layer, can be reduced. The thickness of the sensitive girders is larger than the thickness of the support girders, so that the stress concentration can be achieved. As a result, the sensitivity and the figure of merit are improved.

The invention provides an adhesion safety detecting method of a tower crane. The method comprises the following steps of: determining a force transmission relation between a tower roof system of the tower crane and the position of the tower body connected with an adhesion device through establishing a mathematical structural model of the tower crane, wherein the vibration parameter of the tower system is tested in the construction site to obtain a fixed vibration frequency of the tower crane and a maximum vibration amplitude of a hoisting weight in the vertical direction so that the stiffness coefficient of the adhesion system and the stress situation of the position of the tower body connected with the adhesion device can be obtained according to the force transmission relation between the tower roof system of the tower crane and the position of the tower body connected with the adhesion device; thus, the safety of the adhesion device of the tower crane is judged. By using the method provided by the invention, the possible dangerous working condition of the tower can be analyzed to find parts of the tower body and the adhesion device that may exceed the limit value so as to take responsive measures immediately; and effective guaranteeing effect can be generated on the safe use of the tower temporarily designed with the adhesion device.

The invention provides a modeling method of liquid sloshing in a microgravity environment of a spherical tank. Firstly, an equivalent mechanical model of liquid sloshing under the microgravity environment of a spherical tank is established. The equivalent mechanical model is a three-axis spring-mass equivalent mechanical model which contains the rest mass m0 and the sloshing mass ms, wherein the rest mass m0 is located in the center of the spherical tank, the sloshing mass is connected with the tank by three spring dampers with a stiffness coefficient of Ks and a damping coefficient of Cs. When the sloshing mass is in the equilibrium position, the directions of the three spring dampers are respectively overlapped with the three axes of the spherical tank. Then, the n-order natural frequency [omega]0i and the modal [phi]i of the liquid sloshing in the zero-gravity environment of the spherical tank are calculated. Finally, based on the force of the liquid applied to the wall of the tank and the kinetic energy of the sloshing liquid relative to the tank, the force of the equivalent mechanical model and the kinetic energy equivalent principle, the sloshing mass ms and the rest mass m0 of the equivalent mechanical model are obtained by calculation.

The invention provides a mixed vibration control device and method based on negative stiffness and variable damping and application. The device comprises a negative stiffness component and a variabledamping component connected in parallel between a component on a reed and a component under the reed, a sensor I for measuring vibration of the component on the reed and transferring vibration information, a sensor II for measuring vibration of the component under the reed or a substrate and transferring vibration information, and a controller. The controller receives the vibration information ofthe sensors I and II and adjusts the stiffness coefficient of the negative stiffness component and the damping coefficient of the variable damping component according to attribute parameters of a structure and a control algorithm. The mixed vibration control device solves the problem that semi-active control cannot provide a control force, the direction of which is as same as a vibrating speed direction, so as to execute the control algorithm to obtain the optimum theoretical control force integrally, thereby obtaining a vibration control effect as same as that of active control.

A device is provided by which the stiffness coefficient of a flexure, in either a pitch or roll direction, can be measured while a slider is mounted thereon and while the flexure and slider are in a loaded condition as might be obtained during normal operational conditions of a HGA in a HDA. There are two methods of making the measurement, a static method in which the slider is loaded by an external weight called a pendulum and the angular displacement of the slider is measured, and a dynamical method in which the pendulum is caused to oscillate while in contact with the slider and its natural and loaded frequencies of oscillation are measured.

The invention discloses a piezoelectric type variable stiffness and variable damping dynamic vibration absorber. The dynamic vibration absorber comprises an upper bearing platform and a lower bearingplatform; a mass inertia block and a plurality of vibration absorbing units are arranged between the upper bearing platform and the lower bearing platform; the lower bearing platform is fixedly connected with equipment awaiting vibration damping; and each vibration absorbing unit comprises two first piezoelectric elements, a friction lever, a plurality of vertical elastic elements and a second piezoelectric element, wherein the two first piezoelectric elements are arranged on the upper bearing platform and the lower bearing platform correspondingly, the two ends of the friction lever are connected with the two first piezoelectric elements, and the middle part of the friction lever penetrates through the mass inertia block, the two ends of each of the multiple vertical elastic elements areconnected with the mass inertia block and the first piezoelectric elements, and the second piezoelectric element is arranged on the joint face of the friction lever and the mass inertia block. The dynamic vibration absorber disclosed by the invention has the advantages that the stiffness coefficient and the damping coefficient of the vibration absorber can be designed according to the vibration characteristics of the equipment; stiffness and damping can be adjusted by controlling voltage; the dynamic vibration absorber can be effectively applied to architectural and mechanical equipment variedin vibration property; semi-active control over vibration can be realized; and a good vibration damping effect can be achieved.

A multi-axial fatigue testing machine is disclosed. A drive unit is adopted to provide circulation power, and circulation force is transferred through a force transmission arm, a sliding device and a force transmission spring to a test piece such that the test piece is in a multi-axial fatigue stress state. By selecting the drive unit to connect bolt holes at different positions, multi-axial stress amplitude load applied on the test piece is adjusted; by replacing force transmission springs with different stiffness coefficients, stress amplitude load applied on the test piece is adjusted; and by changing moving displacement of a fixed device in a slide, different magnitudes of one-way initial stress or multi-way initial stress are applied. Therefore, the multi-axial fatigue testing machine can carry out a multi-axial fatigue test of a component by selecting reasonable magnitudes of stress amplitude and initial stress according to different force environments.

The invention provides a secondary relief valve, a hydraulic lowering system for cranes and a crane. The secondary relief valve comprises a valve body, a spool and a pressure regulator, the pressure regulator comprises a first-stage pressure-regulating spring and a pressure-regulating plug which are coaxial with the spool, one end of the first-stage pressure-regulating spring abuts against the end of the spool, the other end of the first-stage pressure-regulating spring abuts against the pressure-regulating plug, the pressure regulator also comprises a second-stage pressure-regulating spring, the diameter and length of the second-stage pressure-regulating spring are less than the diameter and length of the first-stage pressure-regulating spring, and the stiffness coefficient of the second-stage pressure-regulating spring is greater than the stiffness coefficient of the first-stage pressure-regulating spring. The pressure-flow relation of the secondary relief valve has two states; when the secondary relief valve is applied on the hydraulic lowering system for cranes, the hydraulic lowering system for cranes has two lowering control modes, i.e. self-weight lowering and powered lowering; the self-weight lowering mode can be adopted for low-speed lowering in order to achieve good lowering control performance; if lowering needs to be accelerated, an accelerator can be stepped to increase flow, consequently, powered lowering is carried out, and the lowering speed is increased.