Compliant Suspension Research Articles

Acoustic stringed instrument with spring supported top

A stringed instrument with a compliantly suspended sound board allows for deeper, richer sound in s smaller sized instrument. The compliant suspension of the sound board allows for greater acoustic excursions at the edges of the sound board. The resonance set up between the compliance of the sound suspension and the mass of the sound board may be placed below and near the Helmholtz resonance of the instrument to effectively create a broader, lower-frequency Helmholtz resonance than would typically be achievable in instruments of similar size.

Tilted folded-beam suspension for extending the stable travel range of comb-drive actuators

We investigate the electromechanical side instability and the stable travel range of comb-drive actuators. The stable travel range depends on the finger gap spacing, the initial finger overlap, and the spring stiffness ratio of the compliant suspension. Proper design of the suspension structure is the most effective way to stabilize the actuator and therefore to achieve a large deflection. In this paper, we propose an improved suspension design, the so-called tilted folded-beam suspension. Using such suspension, the stability of the comb-drive actuator is improved and the stable travel range is enhanced. We give the expressions for the spring constants of the proposed suspension, both in the stroke direction and perpendicular to it. The suspension designs are also studied numerically using the finite element method (FEM), in which the geometric nonlinearities, such as large deflections and stress stiffening, are considered. Analytical calculations and FEM simulations are compared. The results demonstrate that an enhanced stable travel range, compared to that of a comb-drive actuator with the most commonly used folded-beam flexure, can be achieved by using the proposed suspension design. Comb-drive actuators with various tilted folded-beam suspensions have also been fabricated using the standard surface micromachining technology and their operational performances have been characterized. The experimental results are in good agreement with the theoretical predictions.

Loudspeakers with panel-form acoustic radiating elements

A loudspeaker (81) comprising an enclosure, an acoustic radiator (2) in the enclosure, a compliant suspension (3) mounting the radiator in the enclosure for pistonic movement relative thereto, and transducer means (9) for driving the radiator pistonically, characterized in that the radiator is a panel-form distributed mode acoustic radiator, by a first transducer mounted wholly and exclusively on the radiator to vibrate the radiator to cause it to resonate, and by means (11) for varying the air pressure in the enclosure to cause the radiator to move pistonically.

Experimental Modal Analysis Of A Water-filledCircular Cylindrical Tank

Experimental modal analysis has been performed on an empty and water-filled, circular cylindrical tank horizontally suspended. The tank is composed of a circular cylindrical shell with a longitudinal butt seam welding and two end annular plates. A rubber disk was glued to each annular plate to close the tank. The boundary conditions imposed to the circular cylindrical shell by the thin end plates can be considered very close to simply supports. Two little pipe fittings, used for supplying water, were welded to one of the end plates in such a position that they do not affect shell vibrations. The tank was hung to a truss with its axis kept horizontal by a compliant suspension, by using cables connected to the end plates. The Frequency Response Functions (FRFs) between 100 response points and one single excitation point (SIMO test) have been measured. Burst random has been used as excitation input. Natural frequencies and mode shapes are in very good agreement with theoretical data computed using the Fliigge theory of shells and potential and incompressible fluid model.

Non-magnetic fluid grinding

This paper describes a development of the magnetic fluid grinding process for the finish manufacture of ceramic balls. Magnetic fluid in magnetic fluid grinding has three functions: to cause viscous drag on balls moving through it, so that large sliding speeds may be created at the contacts between the balls and their drive (grinding) shaft, to create a very compliant suspension for the balls and to levitate loose grinding grits so that they may embed in the drive shaft. But magnetic fluid is costly and needs to be maintained. Here it is shown how these functions have been realised without magnetic fluid. The non-magnetic fluid grinding process has achieved removal rates from silicon nitride balls 25 times higher than lapping, in the same way as has magnetic fluid grinding.

An experimental evaluation of individual partition segment configurations for the active control of sound transmission

Lightweight partitions segmented into discretely actuated subsections with mutual interstices and compliant suspensions have been proposed for active sound transmission control (ASTC). In this work, experimental efforts are undertaken to explore important active and passive characteristics of two partition segment models under normal-incidence excitation. The control objective for the configurations is to actively minimize the normal vibration of their transmitting surfaces—instead of an acoustic field quantity in the receiving space. For this functional strategy to be effective, experiments affirm the importance of efficiently and simultaneously controlling vibrations of transmitting subpanels, suspensions, and interstices to achieve high transmission loss. Distinct segment configurations and control schemes allow varying degrees of global transmitting surface vibration control. However, one configuration tested has been theoretically shown to produce efficient control of its various transmitting surfaces using simple control schemes. Measurements confirm that it also provides exceptionally high transmission loss over a broad frequency range—including very low frequencies. a)Currently at Crown International, 1718 W. Mishawaka Rd., Elkhart, IN 46515-1000.

Electrostatic Comb Drive Levitation And Control Method

This paper presents the theory, simulation results, and experimental study of the levitating force (normal to the substrate) associated with Interdigitated capacitor (electro static comb) lateral actuators. For compliant suspensions, normal displacements of over 2 /spl mu/m for a comb bias of 30 V are observed. This phenomenon is due to electrostatic attraction induced on top of the suspended structure. By electrically lsolating alternating drive-comb fingers and applying voltages of equal magnitude and opposite sign, levitation force can be reduced by an order of magnitude, while reducing the lateral drive force by less than a factor of 2. The levitation theory incorporates electrostatic simulation results, and agrees well with experimental data.

Carrying loads with springy poles

People throughout Asia use springy bamboo poles to carry the loads of everyday life. These poles are a very compliant suspension system that allows the load to move along a nearly horizontal path while the person bounces up and down with each step. Could this be an economical way to carry loads inasmuch as no gravitational work has to be done to lift the load repeatedly? To find out, an experiment was conducted in which four male subjects ran at 3.0 m/s on a motorized treadmill with no load and while carrying a load equal to 19% body wt with compliant poles. Oxygen consumption rate, vertical ground reaction force, and the force exerted by the load on the shoulders were measured. Oxygen consumption rate increased by 22%. The same increase has previously been observed when loads are carried with a backpack. Thus compliant poles are not a particularly economical method of load carriage. However, pole suspension systems offer important advantages: they minimize peak shoulder forces and loading rates. In addition, the peak vertical ground reaction force is only slightly increased above unloaded levels when loads are carried with poles.

Noise-reducing valve construction

The invention provides a two-part casing for a multistage valve, itself configured for noise-reduction. Further noise reduction is achieved by complaint suspension of the valve in a two-part casing wherein separable parts of the casing define a cavity for containing nested stages of the valve. Provision is made for selective adjustment of compressional loading of the compliant suspension.

ELECTRONIC ACCELERATION‐SENSITIVE GEOPHONE FOR SEISMIC PROSPECTING***

AbstractPreviously ignored characteristics of the seismic recording instrument are presently experienced as limitations as more sophisticated interpretive methods using wider frequency ranges are developed to extract stratigraphic information from seismic land data for hydrocarbon and mineral exploration. Most of these limitations arise from inadequate characteristics of the first element of the seismic instrument: the geophone. A geophone does not faithfully follow the motion of the earth for higher frequencies due to poor geophone‐earth coupling. This filtering effect brings about time shifts that are dependent on the frequency and the soil type. A geophone can also produce spurious outputs, brought about by the motion of the suspended part of the geophone, with a magnitude comparable to that of the desired output. The suspension is made very compliant to obtain the required sensitivity. A compliant suspension, however, gives a large sag. The geophone can therefore only be used in one position, tolerating little tilt. A compliant suspension also widens the traveling range of the movable part. Minor sensitivity changes with travel are then noticeable as nonlinearity, since the surface wave is large with respect to the reflected wave. A compliant suspension is usually realized in the form of thin, spirally shaped spring‐spiders. Such suspensions exhibit transverse or rotational resonances that are in or close to the seismic frequency band. Excited by ground roll, they can produce considerable undesirable output.The novel geophone we describe is a light‐weight (17 g) acceleration‐sensitive transducer which gives good ground coupling and partial correction for the increasing damping in the earth with increasing frequencies. It employs internal hybrid electronics for a magnetodynamic velocity‐nulling feedback system. Velocity nulling makes the movable part of the geophone virtually rigid with respect to the housing. This makes the geophone characteristics independent of the suspension. The springs used are stiff in a transverse and rotational direction so that the suspension resonances are well outside the useful frequency band. This suspension also allows the geophone to be used in any orientation while being only sensitive to the vibration component along the main axis. The feedback system makes the sensitivity flat within 1 dB from 2 Hz to 500 Hz, with a phase tolerance smaller than 5°. The geophone is robust, has no moving internal wires, employs a current output [sensitivity 1 mA/(m s−2)] and internal gain so that the signal‐to‐cable‐noise ratio is improved. This type of output allows parallel connection without any interaction between the geophones.