JPH0156698B2 - - Google Patents

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a vibration testing device.

(Prior Art) The term "quasi-random vibration" as used in this specification refers to the fundamental wave of a line spectrum containing multiple equally spaced spectral lines, that is, harmonic components, when the frequency of vibration is changed. This means that the frequency varies randomly over time within a given frequency range, and the amplitude of each spectral line varies randomly. In this case, the fundamental frequency varies in such a way that, when averaged over a sufficiently long period of time, it can generate a substantially continuous spectrum. Also “pseudo-random”
The term refers to a mathematical method, such as an algorithm, for selecting a sequence of numerical information in order to modify the operation of a driving means for driving a vibrating body. The term "pseudorandom" is used here because the series of numerical information is obtained by a predetermined calculation method, and is not obtained completely randomly. The term "multiple degrees of freedom" refers to the ability of a vibrating structure to move or rotate in multiple directions within a given range, and the term "spectrum" refers to the cumulative change in vibration energy over time with respect to vibration frequency at a particular vibration level. The term "multimode" refers to a situation in which multiple vibrating structures are vibrating simultaneously. Additionally, the term "node" refers to an unchanging position relative to a particular mode of vibration. A large number of nodes indicates a higher vibration mode, ie, a high frequency vibration state. The term "nodal line" means a line connecting two or more nodes, and the term "local node"
The terms "local node line" and "local node line" refer to nodes and node lines, respectively, where absolute determination is difficult.

Conventionally, vibration tests on aircraft radar equipment, infrared detection equipment, etc. have been performed using a single-axis vibration device driven at a fundamental frequency. Single or multiple motorized vibrators and controls are used to perform vibration tests in a single or multiple axes. This type of apparatus is expensive, and when performing a vibration test in a multi-axial vibration mode, it is difficult to increase the vibration frequency at a constant rate, that is, acceleration.

The use of a large number of pneumatic vibration devices to obtain vibration modes similar to random vibrations was reported in the Shock & Vibration Test Bulletin.
Vibration Bulletin)” (Published August 1976, Part 3)
No. 46, pages 1 to 14) by General Dynamics Corporation. According to the report, vibration testing for missiles was conducted on missiles held in a freely movable state.
This is done by directly attaching several pneumatic vibration devices. In-flight random vibration information is obtained, and the frequency spectrum and acceleration level are determined from the number and size of attached vibration devices and average air pressure. The supply pressure is varied periodically to prevent the inherent distortive vibrations of the missile structure and to determine the frequency spectrum. "Journal of Environmental Sciences"
(November/December 1976 issue, Westenghouse), pages 32 to 38 introduce a pneumatic vibration device for testing aircraft equipment. These vibrating devices are 2
Mounted directly on the fixed body to provide axial vibration. The air pressure is modulated to minimize the line spectrum, with emphasis on obtaining useful vibrational energy at frequencies below 2500Hz.

Other prior art is disclosed in the US Patent Specification (No.
4011749, 3686927 and 3710082). The U.S. patent specification (No. 4011749) introduces a multi-stage degree-of-freedom vibrating device with a test stand that provides time-varying deviations using a complex hydraulic drive system with six degrees of freedom. has been done. U.S. Patent No. 3686927 describes a method for coupling a given plate, beam, or concentric cylinder to another beam or intermediate vibrating body to impart multimode vibration to a test object. ing. The vibration device presented here is controlled solely by the excitation frequency and amplitude. Furthermore, the patent specification (No.
3710082) involves digitally detecting the vibration state, determining frequency information (Fourier transform), comparing this frequency information with a predetermined spectrum, and multiplying this frequency information by the sine and cosine values of the four angles. However, a method is described in which this frequency information is converted into time information (inverse Fourier transform), and this time information is converted into analog information to excite the base of the vibration device.

As described above, various vibrating devices have been provided in the past. Some of these vibrating devices are driven by input signals having a plurality of individually determined frequencies, but even in this case it has not been possible to obtain random vibrations. It has also been considered to use supports that, when excited, resonate at different frequencies in different axial directions, but in this case too it was not possible to obtain controllable random oscillations. Furthermore, in conventional vibration testing apparatuses, there is generally a tendency to suppress excitation in axial directions other than the main shaft to be tested as much as possible.
For this reason, it has not been possible to simulate random or quasi-random vibrations that actually occur in multiple axial directions.

(Problems to be Solved by the Invention) An object of the present invention is to provide a vibration testing device that can generate quasi-random vibrations in multiaxial directions as desired. Furthermore, in conventional equipment, the test object is placed on a vibration table, and this vibration table is directly driven by a vibration drive device, but this vibration table has its own resonance characteristics, so In the case of random vibration, the vibration characteristics change depending on the resonance characteristics, and there is a risk that vibrations different from those of the drive device will be applied to the test object, making it difficult to apply the desired vibration accurately. . The object of the present invention is to develop a device that can apply vibration to a test object without being affected by the resonance of the vibration table.

[Structure of the Invention] (Means and Effects for Solving the Problems) The present invention provides a vibrating body that supports a test object, and a vibration device that is coupled to the vibrating body and operates to give vibration to the test object. A mechanism for automatically changing the vibration output of the vibration device, thereby increasing randomness in multi-axis vibration, and generating quasi-random simultaneous multi-axis vibration in the test object, in a vibration testing device comprising: is coupled between the vibrating device and the test object, and a closed-loop device is coupled between the vibrating body and the vibrating device to detect and control the level of multiaxial vibration. shall be.

In one aspect of the invention, a pneumatic vibrator is vibrated to perform frequency spectrum and frequency change control, i.e. acceleration control, of a quasi-random vibration output in the frequency range of 40 Hz to 2 kHz, for example, for vibration testing. connected to the body assembly. This vibrating body assembly includes a driving section that mechanically processes vibration input from the vibrating device, and a driven section that provides multi-axial and multi-mode vibration output to the test object.
and an elastic structure that interconnects them. The drive section responds to a strong vibration spectrum generated in multiple axes and in multiple modes by the vibration device. The driven section also vibrates in response to modulated vibrational energy from the drive section via a suitable elastic material.
By appropriate selection of the dimensions, weight and resonance characteristics of the driving and driven sections, a well-controlled multi-mode, constant
Vibration tests can be performed with RMS acceleration, multiple degrees of freedom, and within a predetermined vibration frequency range. By holding the elastic coupling member locally and fixedly, nodes are formed at several points of the vibrating structure, and relative fluctuations of the driving section and the driven section provided at these nodes are suppressed. ing. Depending on whether a mechanical or pneumatic vibration input is used, the fixed holding position will be static or dynamic. Modification of the number of modes and acceleration levels is accomplished by pre-compressing or stretching the elastic coupling structure to control the amount of vibrational energy that passes through the elastic coupling structure.

The automatic control and pseudo-random modulation of air pressure in pneumatic vibrators provides closed-loop vibration, spectral control and spectral weighting capabilities to generate better frequency information and ensure that the vibrations of a resonant structure are tuned to a specific vibration frequency. Prevent it from being locked. Vibration control is also performed in orthogonal directions to establish actual operating conditions. The vibration frequency of the vibrator can be varied by means of an orifice of variable effective area between the compressed air supply and the pneumatic vibrator. This pseudo-random change of the effective area of the orifice is performed, for example, every 2 to 3 seconds by a compressed air control controlled by a microprocessor program. That is, the vibration input to the test object is periodically detected, the effective value of this vibration input is calculated, this effective value is compared with a predetermined effective value, and the air supply to the vibration device is adjusted based on the comparison result. By digitally controlling the amount, the vibration frequency is controlled to a predetermined value. In this case, the predetermined spectrum of the resonant structure is mechanically controlled.

The output of the pneumatic vibrator is adjusted by varying the amount of compressed air, effectively increasing the vibration output and weighting the vibration spectrum. The air pressure is varied by changing the effective area of an orifice located between the compressed air source and the pneumatic drive means manifold. Further, the microprocessor is equipped with program information indicating the relationship between the effective area of the orifice and the frequency characteristics of the test object. During the test, the microprocessor periodically changes the effective area of the orifice in a pseudo-random manner using the compressed air supply control unit and the drive circuit, and supplies air with a constant pressure distribution through the manifold of the drive means. do. This change in compressed air changes the acceleration characteristics of the test object. Problems caused by variations in acceleration characteristics are resolved by weighting the spectrum. Automatic acceleration control is executed based on information obtained by comparing the effective acceleration value obtained by calculation with the effective acceleration value obtained from the test result. Acceleration information from three orthogonal axes is transmitted to a multiplexer via a low-pass filter circuit and a sample-and-hold circuit, and is digitized by an analog-to-digital conversion circuit. Meanwhile, unfiltered acceleration information is fed to the pseudo peak detector via another multiplexer. The use of a microprocessor allows for balanced data acquisition. The digital acceleration information is processed and used to calculate an effective acceleration value. The drive pressure required for a given test acceleration level is controlled periodically during the test by a pressure regulator.

(Example) Hereinafter, a vibration test apparatus according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows the entire system including a quasi-random pneumatic vibration device and an automatic frequency control device. The vibrator assembly 20 responds to pressure and volume controlled compressed air delivered from a drive circuit 24 via a compressed air control 22 . A microprocessor 26 is coupled to the compressed air controller 22 for proper operation of the vibrator assembly 20. A feedback and protection circuit 28 connects the vibrator assembly 20 and the microprocessor 2 to provide the necessary information to the microprocessor 26.
6 and electrically coupled between the two. An operator circuit 30 is also provided which is operated to enable the operator to set test parameters to the microprocessor 26 and to provide information to the operator indicating the progress of the vibration test. Additionally, a hardware protection circuit 32 is installed on the microprocessor 2 to prevent excessive compressed air from being applied to the test object due to operator input errors.
6 and the solenoid valve 4 of the compressed air control section 22
8 and a drive circuit 50 that controls the 8. The manifold 52 of the compressed air control section 22 is coupled to the microprocessor 26 via a pneumatic responsive switch 54 and a switch input circuit 56.

The output signal of the vibrating body assembly 20 is sent to the feedback circuit 2.
8, and is compared with predetermined vibration information in the microprocessor 26 to generate an error signal corresponding to the comparison result. This error signal is supplied to the control unit 22 via the drive circuit 24,
The vibrator assembly 20 vibrates the test object in response to this error signal.

As shown in FIGS. 2, 3a and 3b, the vibrator assembly 20 of FIG. It includes a plurality of coupled pneumatic vibrating sections 34, 34-2, 34-3. The entire system is supported on standoffs 37-2 at the driven body node points (FIG. 2). Drive section 36 is vibrating section 3
Various vibration modes are taken based on harmonic response characteristics to vibration input from 4 and multimode response characteristics determined by dimensions and materials such as aluminum and magnesium. Distortion movements caused by various modes of forced and free vibrations are caused by viscous and elastic structures 40, 40-2, including, for example, elastic members 40a, 40a-2, 40a-3 and damper members 40b, 40b-2, 40b-3. 40-3
Driven sections 38, 38-2, 38 through
-3. This driven section 38 will therefore generate a complex mode of distorting motion obtained by superimposing the controlled vibration mode of the driving section 36 on the forced and free vibration modes of this section 38. By setting the coupling fulcrum of the vibrator frame at the point of maximum amplitude movement of the vibrating structure, ie, the antinode point, a multimode response characteristic with maximum coupling between the drive and driven sections is obtained.

Figures 4a to 4f show the relationship between acceleration spectral density (G ² /Hz) and vibration frequency (Hz). FIG. 4a shows pneumatic vibration devices 34, 34-2,
Figures 4b and 4c show graphs 34' in a direction perpendicular to the piston axis of 34-3;
Graphs 36' and 3 in the X and Z directions of
Figures 4d and 4e show the drive sections 36, 36-2, 3 from which the data for graphs 36' and 36'' of Figures 4b and 4c are taken.
Figure 4f shows the graphs 38' and 38'' of the driven sections 38, 38-2, 38-3 in the X and Z directions opposite the point on the specimen 42, 42-2, 42 under test. Graph 4 representing the average value of vibration energy in three directions given to -3
2' is shown. Driven section 38, 38-2,
The vibration output from 38-3 is detected by accelerometer 44 and provided to feedback and protection circuit 28.

The vibrating device (vibrating section 34) of the vibrating body assembly 20 excites the vibrating body in different linear and rotational vibration modes, depending on the natural vibration frequency of the vibrating body and the multiple of the excitation frequency. The vibration frequency in the low frequency natural vibration mode of the drive section 36 is adjusted to keep the energy uniform in the forced vibration and natural vibration spectra, i.e.
In order to avoid concentration on a certain frequency, it is determined not to be an integral multiple of the fundamental excitation frequency obtained from the vibration section 34. Drive sections 36, 36-2, 36 excited in the initial state
-3 and driven sections 38, 38-2, 3
Due to the complex mode coupling between 8-3, various composite vibration modes are obtained from the motion of the individual and integrated vibrating bodies deformed by the elastic coupling members 40, 40-2, 40-3. This vibration spectrum input is the test object 42, 42-2, 42-
Added to 3. By exploiting the vibration transfer characteristics of the coupling means of the driving section 36 and the driven section 38, it is possible to achieve good control of the power spectrum within a particular frequency range, for example from 40 Hz to 2 kHz. Elastic member 4
0 is formed of suitable shape and characteristics and inserted between the driving and driven sections. By appropriately selecting the vibration energy transmission characteristics of this elastic member, the drive sections 36, 36-2,
Regardless of the high frequency excitation frequency in 36-3,
It is possible to attenuate the vibration spectrum input to the test object near the upper limit frequency.

The vibrating sections 34, 34-2, 34-3 are constituted by percussive pneumatic vibrators with freely movable percussion pistons, but can be replaced by shock absorbers with freely movable pistons if the desired vibration frequency can be obtained. It is also possible to use a type pneumatic vibrator, a rotary pneumatic vibrator, a hydraulic vibrator, or the like. In an impact-type vibrator, a sliding piston applies an impact force to at least one end surface of a vibrator housing when the driving air pressure reaches a predetermined value. This impact force can be applied over a very wide area, e.g.
A mechanical vibration phenomenon containing various harmonic components is generated over a range of 50 Hz to several kHz. The upper limit of this vibration frequency depends on the natural frequency of the structure to which the vibration device is attached. It is also possible to use vibration devices of different dimensions and combinations to obtain different fundamental frequencies for the vibration characteristics of the vibrating body and for any given air pressure. Air pressure determines the fundamental or lowest frequency and the final impact force level.

It is desirable that the degree of vibration energy coupling between the vibrating bodies be set constant at each frequency between the lowest vibration frequency and about 2 kHz. However, most of the vibrational input energy is concentrated at vibrational frequencies equal to multiples of the fundamental frequency of the body of the vibrating device with the freely movable piston. In this case, a change in drive pressure large enough to vary the fundamental frequency by 25% to 50% is required. This variation of the fundamental frequency provides a weighting of the vibration spectrum, making it possible to generate sufficient vibration energy characteristics for a given test period at all frequencies without being fixed to any frequency.

The distortion phenomenon occurring in the driving and driven sections shown in FIGS. 2 and 3 is illustrated in FIGS. 5a and 5b.
6a and 6b. FIG. 5a shows beam 80 attached at both ends 82 to pivots 84. Figure 5a shows the free fundamental modes of vibration with respect to a centerline 86 connecting the fulcrums 88 defining the two nodes. FIG. 5b shows a free vibration mode, ie, a third harmonic vibration mode, which has two nodes 88' in addition to the node of fulcrum 88. Figures 6a and 6b represent Figures 5a and 5b.
A beam 90 similar to that used in the figure is pivoted at both ends 92 and also has a force node point 92'.
The fundamental vibration mode obtained when . In the case of Figure 6b, which shows the third harmonic vibration mode, there are two more node points 92'';
It has 5 nodes in total. Like this, the beam 9
0 indicates yet another distortion motion, and therefore more various vibration modes are obtained.

By suppressing the movement of the vibrating body in one or more positions in this way, it is possible to generate vibration energy in higher vibration modes. As shown in FIGS. 5a to 6b, the positions where the relative motion is almost zero are called nodes, and the node pattern is determined theoretically or experimentally. It is therefore possible to equalize or differentiate the vibration energy distribution at high and low vibration frequencies. In practice, forced nodal points are obtained by supporting the beam at a fixed position on a fixed body. In addition, when driving and driven sections are used as shown in FIGS. 2 and 3, an elastic pad having a hardness different from that of the elastic bonding material between the driving and driven sections may be sandwiched between the driving and driven sections. It is possible to obtain forced node points. By applying spring-acting forces at adjacent locations on the drive and driven sections, the coefficient of vibrational energy transfer through the elastic member is increased and the vibrational characteristics of the co-acting vibratory bodies can be manually modified. It becomes possible.

The manual device for establishing forced node points is effective in controlling the operating characteristics of the drive and driven sections between excitation periods, but it also provides an air gap in the elastic coupling member between said drive and driven sections. It is possible to establish forced node points during testing by installing pressure-responsive units.

To provide a vibration mode variable device or vibration control device that mechanically, electrically or thermodynamically changes the transmission rate of vibrational energy through an elastic coupling to change vibration frequency information at various acceleration levels. is possible. This makes it possible to test specimens with different weights and hardnesses while varying the acceleration level of said driven section, using an elastic coupling member that does not need to be replaced, a common driven section and the necessary fixings. It becomes possible to do so. The vibration control device is for varying the pressure applied to the contact surface of the elastic coupling member, for example by adjusting a screw or a spring, by applying variable air pressure to the elastic member, or by heating or cooling the elastic member. have the means. for example,
By changing the temperature of the elastic member, the hardness of the elastic member changes non-linearly, making it possible to change the vibration transmissibility.

The control device is configured as shown in FIGS. 7 to 10, for example. FIG. 7 shows a V-shaped vibrator assembly with a pair of plate structures 222. FIG. The plate assembly 222 includes a driving plate 236, a driven plate 238, and an elastic coupling member 240. The plate structure 222 is a fixed side plate 22
6. It is fixed to a common solid plate 224 with 6. Some points on the drive plate 236 are forcibly restrained by coupling members 228 between the drive plate 236 and the stationary side plate 226. The coupling member 228 is shown in FIGS. 8 and 9 as including a manually adjustable fastener 230. In FIG. 10, the connecting member 22
The operating state of the air bag 8c can be controlled according to the air pressure by means of an air bag 229 that connects the pair of halves of the connecting portions 233.

Drive and driven plates 236 and 238
Devices for controlling the degree of elastic coupling between the nodes are shown as including node controllers 250, 250a, b, c. These control devices are 8th, 9th and 1st
It is shown in Figure 0. In FIG. 8, the node controller 250a includes the driving and driven plates 23
An elastic ring 25 provided between 6a and 238a
2a and a ring 254a installed outside the driven plate 238a. plate 2
A bolt 256a extending through 36a and 238a and rings 252a and 254a cooperates with a nut 258a to hold the entire assembly together. An appropriate spring acting force is applied to the ring 254a.
Provided by a spring 260a between the upper washer and the bolt head.

In FIG. 9, the control function is provided by a gap formed between drive and driven plates 236b and 238b. The control device 250b includes an elastic ring 25 that forms a sanderch structure with the driven plate 238b and the washer 257.
2b and 254b. A bolt 256b with large and small diameter axes 256b' and 256b'' passes through the plates 236b and 238b.
Gap 2 is fixed to large diameter portion 256b' with a screw relative to b, and held on large diameter portion 256b' in contact with plate 236b.
The size of 60b is determined. A pair of nuts 261b on shaft 256b'' applies a compressive force to rings 252b and 254b.

In FIG. 10, the node control device 250c
is a specially constructed bolt 25 with an air passage 257c.
Equipped with a pneumatic adjustment device using 6c. This air passage 257c is connected to the driving and driven plate 23.
Air chambers 252c, 254c and 258c form a sanderch structure with 6c and 238c
is combined with Air pressure is transmitted to each air chamber via a cap 260c having a threaded structure.

Mechanical and pneumatic controls are provided by the node control device 25
0a, 250b and 250c, thermodynamic control of the elastic members is performed on the elastic coupling members 240a and 240b as shown in FIGS. 8 and 9. In either case, the elastic coupling member is connected to a heater wire 266a to soften the elastic material so as to reduce the vibration acceleration level.
and 266b, elastic members 262a and 262b are held between the driving and driven plates by elastic coupling bodies 264a and 264b with variable vibration transmissibility. Cooling passages 268a and 268b are formed to harden this elastic member, thereby providing higher acceleration levels.

In FIG. 10, resilient coupling member 240c is connected to drive and driven plates 236c and 238.
The elastic member 262c and the air bag 270c are provided between the elastic members 262c and 270c. Depending on the amount of air in the air bag 270c, the elastic member 262c is pneumatically controlled so as to receive a predetermined load.

A similar method can be used for the annular frame structure shown in FIGS. 11-16. For example, the first
As shown in FIG. 1, the vibrator assembly 320 includes annular drive and driven sections 336 and 3.
38, and resilient coupling members 340a, 340b and 340c (FIGS. 12-16) provided between the driving and driven sections.
As described above, the fixed side plate 326 is attached to the fastening portion 32.
8 to the drive section 336 to prevent local fluctuations of the drive plate. This control is a fixed control as shown in FIGS. 11 and 12, but is variable with the pneumatic control provided by the piston assembly 329 shown in FIG.

The elastic coupling between the driving and driven sections in FIGS. 12 and 13 is provided by node controllers 350a and 350b. Each node controller has driven rings 338a and 33
8b includes a bolt 356a that extends through openings 353a and 353b and abuts drive rings 336a and 336b. This connection between the bolt and the driven ring is biased by springs 360a and 360b, and the resilient member 354
Apply pressure to a, 354b, 352a, etc. 1st
The node control device 350a shown in FIG. 2 has a threaded joint 358a that is threadedly connected to the drive ring 336a, and the node control device 350b shown in FIG. 13 has a spherical nut 358b disposed within the drive section 336b. .

Figures 14-16 show yet another pneumatic control. Node controller 350c includes a continuous or intermittent annular tube 354c between the drive and driven plates. This tube is located between bolt 356c and driven ring 338c, and is also located between drive and driven ring 338c.
An elastic member 362c is provided between 6c and 338c. This driven ring 338c is arranged between the drive ring 336c and the object under test 342. The bolt 356c is threaded into the drive plate 336c and holds the retaining ring 357. The elastic material and tube control the degree of energy transfer between the drive and driven plates through non-linear stiffening characteristics that are modified by pressure applied to the elastic material. Furthermore, in the device shown in FIGS. 15 and 16, the energy transmission means is provided by the driven ring 3
A plurality of air chambers 364 are provided at intervals surrounding the three sides of the end portion of 38c. Separate manifold passages 366 each extend to separate air chambers to provide nodal control in the annular region between the drive and driven plates, and tubes 354c are used to increase vibrational energy transfer.

The operating characteristics of the various devices described above are shown in FIGS. 17 and 18. FIG. 17 shows the vibration spectral density in an annular driven section with and without a simple mechanical node controller. where the solid line 370 shows the operating characteristics of eight pneumatic vibrators operated at 50 psig pressure using a resilient bond formed from a homogeneous foamed silicone elastomer, and the dashed line 37
2, four pneumatic oscillators operated at a pressure of 50 psig using a resilient combination of foamed silicone elastomer separated by 50 shore hardness rubber pads spaced 120° apart. Indicates the operating characteristics of the device.

FIG. 18 shows the vibration spectral density in an annular driven section with and without increased vibration energy transfer rate.
A solid line 374 indicates that no load is applied to the elastic bond;
Demonstrates operating characteristics obtained by operating eight pneumatic vibrators under 40 psig pressure,
Dashed line 376 shows the operating characteristics obtained when applying a pressure of 0.25 in.aq to the elastic bond.

As previously mentioned, the pneumatic vibrating section 3
4, 34-2, and 34-3 are controlled by the compressed air control section 22. This vibrating section 34 is connected to a solenoid air conditioning valve 48, for example. Each valve 48 is held open during system operation and receives a constant amount of air from the drive manifold 52. It is also possible to use a single valve for all vibrating sections or to use pneumatic valves instead of solenoid valves. The solenoid valves are actuated by a drive circuit 50 coupled to the microprocessor 26 through a protection circuit 32. The protection circuit 32 opens the circuit between the microprocessor 26 and the drive circuit 50 and closes the solenoid valve 48 in the event of a condition that could damage the equipment, such as the occurrence of an excessive test condition. occluding the air supply to the vibrating section 34. This blocks vibration input to the vibration table assembly 20. Also, an air valve 51 connected to the manifold 52 and communicating with the atmosphere by a signal from the drive circuit 50
is opened, releasing the incoming compressed air.

The manifold 52 is equipped with a high pressure air reservoir to supply uniform compressed air to all the vibrating devices. It is necessary that this air reservoir be made small enough to respond to changes in the pressure and volume of the air supply. A pneumatic responsive switch 54 and a switch input device 56 are coupled in series between manifold 52 and microprocessor 26;
It acts as a limit switch to stop the air supply to the manifold if the air pressure becomes lower than a predetermined value or becomes abnormally high, and to bring the pressure in the manifold to an appropriate level before starting the test. If desired, instead of using such a switch, a pressure transducer can be used to detect the exact value of the air pressure and set the appropriate acceleration level for automatic control.

Compressed air to manifold 52 is supplied through fluid path 89 and orifice 58 of variable effective area. This changes the air pressure level in this manifold 52 over time, adjusts the amount of air supplied to the vibrating section 34, and imparts various lever vibratory energy to the drive section 36. The orifice 58 is controlled by a compressed air controller 60 driven by a drive circuit 62 in response to instructions from the microprocessor 26. This orifice 58 is configured as shown in FIGS. 20 to 22 or 26, for example, and the structure of the control section 60 is determined depending on the configuration. orifice 58
When the control section 60 is constituted by a cam-orifice structure as shown in FIGS. 20-22, the control section 60 is constituted by a shaft whose rotational movement is limited, for example by a limit switch 64. Also, if the orifice 58 is configured as shown in FIG. 26, the limit switch 64 can be omitted.

The level of air pressure supplied to orifice 58 is controlled by servo adjuster 68 and microprocessor 26.
It is controlled by a servo drive circuit 70 operated by. Since the servo adjustment unit 68 operates mechanically, a limit switch 7 is provided to limit the movement.
2 is required. Air pressure regulator 66 allows a constant pressure and volume of compressed air to be supplied to orifice 58 via fluid path 87 over a relatively long period of time. Air to this regulator 66 is supplied through an air filter 76 from an air supply 74.

Before subjecting the test object 43 to vibration conditions, the pressure in the drive manifold 52 is sensed by the pressure switch 54, which causes the air pressure regulator 66 to supply air at a pressure and amount directly related to the desired vibration. It is set as follows. When a test is initiated, the average acceleration level is detected by accelerometer 44 over a predetermined period of time, eg, 2.5 minutes, and activates air pressure regulator 66. On the other hand, the microprocessor 26 supplies the program to the orifice 58 at a rapid rate of, for example, 2.75 seconds per pressure change. The effective area of this orifice 58 is varied as the average acceleration level is detected to control the average pressure of the air supplied to the pneumatic vibrator. This allows the average acceleration response characteristic (Grms)
is improved. In this case, the air pressure regulator 66 and the limit switches 72 and 6 of the orifice 58
4 is energized to prevent the servo drive signal from operating the servo adjustment section more than necessary, and
This information is provided to microprocessor 26.

The electrical circuitry of the system of FIG. 1 is shown in detail in FIG. In FIG. 19, a drive circuit 24 for controlling compressed air drives a step motor (a specific example of the compressed air control unit 60) in accordance with a computer program in a microprocessor 26 to rotate a cam. This drive circuit 24 also drives an air pressure regulator 66 via a servo drive circuit 70, supplying air pressure to the orifice 58 based on information obtained from the pressure switch before the start of the test and from the accelerometer 44 after the start of the test. Control the area by changing the air pressure.

As shown in FIG. 19, microprocessor 26 is coupled to a pair of counters 114 and 116. When these counters 114, 116, for air pressure regulator 66 and orifice 58, respectively, are at zero count, oscillators 118, 120 are reset and do not oscillate. A microprocessor 26 coupled to servo direction control circuits 126 and 128 via latches 112 and 124 determines whether to increase or decrease air pressure or orifice effective area. Servo direction control circuits 126 and 128, comprised of a pair of NAND gates, are coupled to accept signals transmitted between counters 114, 116 and oscillators 118, 120, and increase signal path 130 and decrease signal path 1.
32 to drive circuits 134 and 136. At the beginning of a counting operation, oscillators 118 and 120 are connected to signal path 130 to control air pressure regulator 66 or orifice 58.
or 132 via drive circuits 134 and 13
6 to rotate the servo motors constituting the servo adjustment section 68 and the compressed air control section 60 in either direction.

Based on the signal from the microprocessor 26 and the start of the counting operation, ie, the number of steps that the servo motors 60 and 68 move, the selected oscillator begins to oscillate. This oscillation output causes the counter to count down until the contents of the counter become zero again. At the same time, signals from counters 114 and 116 are fed back to microprocessor 26 via feedback circuit 138 to communicate to microprocessor 26 whether the oscillator is active.

In this case, limit switches 72 and 64 for regulator 66 and orifice 58 are servo-controlled.
It is biased by the cam and limits the range of motion of this servo cam. These switches prevent the servo cam from being driven more than necessary and send this information to the microprocessor 26.

Feedback and protection circuit 28, shown in FIG. 1, is responsive to the output signal from accelerometer 44 and provides vibration test information to microprocessor 26 while providing protection against excessive abnormal test conditions. This latter function is performed by low pass filter, sample and hold circuit 46, multiplexer 140 and analog-to-digital converter 142. These circuits digitize the analog signal from a given accelerometer to determine the effective acceleration level of the test object. For multi-axial screening operations, an average value of two to six acceleration level signals obtained in at least two of three orthogonal directions is required. Multiplexer 140 allows signals obtained in two or more axes to be processed simultaneously.
In operation, microprocessor 26 provides address signals via electrical connections 143 to low-pass filter, sample and hold circuitry 46 to sample or hold the analog accelerometer signal and to multiplexer 140 to provide address signals. analog-to-digital converter 142
Select the accelerometer signal supplied to the Channel selector 145 selects the number of accelerometer channels for microprocessor 26 to address multiplexer 140.

Feedback and protection circuit 28 as shown in FIG.
is equipped with an auxiliary multiplexer 144, a pseudo peak detector 146, and an abnormal test condition detection circuit 148, and performs a protection function against abnormal test conditions. In operation, channel selector 145 determines the number of accelerometer channels that multiplexer 144 scans. This provides the output signal from accelerometer 44 to these circuits and is transmitted to protection circuit 32. If the vibration level of the vibrator assembly 20 becomes excessive, this information is processed and acts on the protection circuit 32 to prevent the activation signal from the microprocessor 26 to the solenoid valve 48, thereby causing the vibration assembly 34 to compress. Prevent air from being sucked in.

A pneumatic responsive switch 54 is used to determine the internal pressure of the drive manifold 52 and set this pressure to a predetermined value. At least two switches are used to set the rated pressure and a predetermined low pressure, and the switch is set in pressure conditions below a predetermined value to prevent vibrations from occurring below the specific switch setting. It is possible to stop the test by It is also possible to provide a high pressure switch to stop the test in a pressure state above a predetermined value.

The operator circuit 30 is the microprocessor 2
6. It is coupled to the timing circuit 150 and the protection circuit 32, and generates various information in response to operator operations. Test start and stop circuit 152 is configured as a solenoid valve control circuit that operates to start or stop a test. Test time display 154 and test level display 15
6 is configured as a display that displays the test time and the effective value of the acceleration level during the test. The test time setting circuit 158 and the test level setting circuit 160 are comprised of, for example, a thumb-wheel switch for setting the test time and acceleration level.

The timing circuit 150 is connected to the microprocessor 2
6 and protection circuit 32 to allow the operator to set a test time and to stop the vibrations after the set test time has elapsed. The timing circuit 150 includes a counter that is preset by a test time setting circuit 158 in response to instructions from the microprocessor 26. The output signal of this counter is provided to a test time display circuit 154 to indicate the remaining time of the test. When this counter indicates a zero count, it provides a signal to protection circuit 32 to terminate the test. The signal from this counter is also fed to the microprocessor at the same time.

Protection circuit 32 is for coupling various fault detection circuits, operator input devices and microprocessor 26. The fault detection control function of this circuit is derived from the output signals from the abnormal test condition detection circuit, the timing circuit, and the test start and stop circuit. When a test is initiated, microprocessor 26 controls solenoid valve 48 under the protection of protection circuit 32. When abnormal test condition detection circuit 148 detects an abnormal condition, microprocessor 26 loses its ability to control the solenoid valve. A similar result is obtained when timing circuit 150 completes its operation. Furthermore, the status of the protection circuit 32 is displayed by a status indicator 161.

The microprocessor 26 has the functions of adjusting air pressure, receiving and processing vibration signals from the accelerometer, and performing self-diagnosis. Air pressure adjustment is accomplished by varying the effective area of the orifice, which is accomplished by first passing the signal from the accelerometer 44 through a low-pass filter and sample-and-hold circuit 46;
It is converted to an analog signal via multiplexer 140 and analog-to-digital converter 142 and provided to microprocessor 26. Based on the output signal from the accelerometer 44, the microprocessor 26 detects changes in the acceleration level,
Calculate the effective value of the accelerometer signal. The rms value of this accelerometer signal is displayed on a test level display 156 and compared to upper and lower limits programmed into the microprocessor, and when the rms value is outside of the upper and lower limits, the vibration is stopped. , is also used to control the air pressure regulator 66. A system diagnosis and self-diagnosis function by the microprocessor 26 discovers a malfunction in the system.

A conventional 8-bit microprocessor 26 is suitable, but other types of microprocessors can also be used. This microprocessor 26 has random access memory (RAM),
It is equipped with read-only memory (ROM) and input/output latch circuits as required. It is also possible to use minicomputers or microcomputers.

In operation, the microprocessor 26 performs one to two vibrations to prevent the vibrator assembly 20 from locking to a particular frequency, such as the natural frequency.
It is programmed to continuously change the effective area of orifice 58 every second. This results in
The vibrational energy applied to the drive section 36 is changed every 1 to 2 seconds before the previous vibration completely dissipates. The effective area of the orifice 58 is changed in a pseudo-random manner such that the rate of change has a desired distribution, for example, a uniform distribution. As mentioned above, the pseudorandom modification method provides an arithmetic method, eg, an algorithm, for selecting a set of numerical information. This series of numerical information is random in the sense that it is taken based on statistical laws of randomness. The term "pseudo-random" is used here because this series of numerical information is obtained by a predetermined calculation method and is not taken purely at random. Furthermore, the fact that the rate of change in the effective area of the orifice 58 is uniform means that all the manifold internal pressures are selected to have the same magnitude. For example, the open state is provided in 128 stages. Therefore, the random number Ne of the microprocessor program is determined based on the following equation.

Ne ₊₁ = [J+KNe] Base 127 Here, e takes a value from 0 to 127, and J and K each represent a constant.

For the cams shown in FIGS. 20 and 22,
Ne is used as information to determine the angle of this cam. Also, for the orifice shown in FIG. 26, Ne is used to determine the pressure inside the manifold. To obtain the desired pressure inside the manifold, several opened orifices may be combined. In the above example, the effective area of the orifice can be selected in 128 steps, and a specific effective area is provided at each opening position. Since the relationship between the effective area of the orifice and the pressure inside the manifold is determined experimentally, for example, as shown in FIG. It becomes possible to associate it with

Orifice 58, compressed air control 60 and limit switch 64 can be configured as shown in FIGS. 20-22 or 26. 20th
22 shows a cam-type plate 80 and a support wall 8.
housing 85 having an orifice opening 82 formed in 4 and fluid passageways 87 and 89 coupled to pneumatic regulator 66 and manifold 52, respectively;
A cam orifice structure 78 with a cam orifice structure 78 is shown. A drive shaft 86 driven by a step servo motor 88 is coupled to the cam plate 80. Cam orifice structure 78 represents an example of a variable effective area orifice 58 , and drive shaft 86 and motor 88 represent an example of compressed air control section 60 . The limit switcher 64 shown in FIG. 1 is the limit switcher 64 shown in FIG.
Shown as switches 64a and 64b. These limit switches are configured such that extensions 80a of cam-shaped plate 80 abut against these limit switches to limit the range of rotational movement of this plate 80.

Cam type plate 80 and orifice opening 8
2 is set so that the extent to which the end 90 of the plate 80 closes the orifice opening 82 is variable. Cam-shaped plate end 90 and orifice opening 82 are connected to opening 8 in plate 80.
2, the effective area of the orifice opening 82 can be changed at a predetermined rate of change. During the test, a pseudo-random number algorithm in microprocessor 26 causes plate 80 to rotate relative to orifice opening 82 every 2.75 seconds to create orifice effectiveness defined by cam-shaped plate end 90 and orifice opening 82. The area is randomly changed and the pneumatic vibrating section 34
The amount of air supplied to the system is changed pseudo-randomly.

The shape of the plate end 90 is similar to that of the orifice opening 8.
For example, the shape is determined as shown in FIG. 23 to FIG. 25 depending on the shape of the object. The relative relationship between the cam-shaped plate end 90 and the orifice opening 82 changes the effective area of the orifice where the vibration frequency is determined by the relative relationship between the orifice opening 82 and the cam end 90, as shown in FIG. It is set to be changed by In step 92 of FIG. 23, a theoretical equation [1] is given that expresses the relationship between the velocity of the airflow flowing through the orifice, the pressure on the downstream side of the driving manifold, and the effective area of the orifice. Also, in step 94, an empirical equation [2] representing the relationship between the speed of the air flowing through the pneumatic vibrator and the pressure inside the drive manifold, which is equal to the speed of the air constantly flowing through the orifice, is provided. These formulas [1] and [2] are
6, the algorithm is combined to obtain algorithm [3], which shows the relationship between the drive manifold internal pressure and the effective area of the orifice. By combining this algorithm [3] with the experimental formula showing the relationship between the vibration frequency characteristics of the test object and the pressure inside the drive manifold, shown in step 98, the vibration characteristics of the test object and the orifice The relational expression expressing the relationship between effective areas is shown in step 10.
Obtained at 0.

To obtain the empirical equation [2], the result information from a particular vibrator is used to calculate the standard cubic feet/
The relationship between the flow rate of air supplied to each vibrating device, expressed in minutes (SCFM), and the drive manifold internal pressure (psig) is derived. FIG. 24 shows the relationship between manifold internal pressure and air flow rate in various vibrating body assemblies. Line 102 shows the characteristic curve for a single vibrating device; line 10
4 and 106 show averaged characteristic curves of a plurality of vibration devices. Empirical equation [2] is a mathematical equation that expresses linear characteristics obtained from a plurality of vibration devices installed on a vibration table shown in a V-shaped plate structure, as shown in FIGS. 2 and 7, for example. directly required as . On the other hand, theoretical formula [1] is obtained based on the following formula from the relationship between the flow rate of air passing through the orifice, the effective area of the orifice, and the internal pressure of the drive manifold.

m=31.14C _D・M/(1+0.2M ² ) ³・Pu・A … [1] Here, m is the air flow rate expressed in standard cubic feet per minute (SCFM), and C _D is the JA Perry “Critical Flow Through Sharp-Edged Orifice” by
No. 757 of “Orifices” (Vol. 71, published October 1949)
The Pu/Pd relationship obtained from the experimental data introduced on pages 764 to 764 is shown, where Pu indicates the pressure (psig) on the upstream side of the orifice 58 controlled by the pressure regulator 66, and Pd indicates the pressure for driving. where A is the effective area of the orifice (in square inches) and M is the Mach number of air flowing through the orifice, given by:

M=1...(Pu/Pd≧1.893) M=√5 [() ^0.286 −1
...(Pu/Pd≦1.893) Empirical formula obtained from straight line 104 in Fig. 24 [2]
becomes as follows.

m=[1.9+0.151(Pd'-16.5)]N...[2] Here, N is the number of vibrating devices, and Pd' is the pressure (psig) of the driving manifold.

By combining equations [1] and [2], algorithm [3] shown in the following equation is obtained.

A=[1.9+0.151(Pd'-16.5)]N/31.14C _D M
/(1+0.2M ² ) ³・Pu...[3] The experimental formula shown in step 98 of FIG. 23, which expresses the relationship between the vibration frequency characteristics of the test object and the pressure inside the manifold, is shown in the curve 108 of FIG. 25. This is obtained based on experimental data. This empirical formula is combined with algorithm [3] to provide a relationship between the vibration characteristics of the test object and the effective area of the orifice. This makes it possible to obtain a desired vibration frequency by changing the effective area of the orifice. From this information, the geometrical relationship of cam plate end 90 and orifice opening 82 is determined.

The shape of the cam-shaped plate 80 is determined, for example, so that the pressure inside the drive manifold changes linearly with a change in the angular position of the cam-shaped plate 80. Since the effective area of the orifice is expressed as a nonlinear function of the angular position of the plate, it is required that the shape of the plate be designed as shown. The basis for using a linear function is that the acceleration characteristics are expressed as a linear function of the pressure inside the drive manifold, and linear functions can be programmed very easily. However, if it is desired to use a function other than a linear function, the shapes of the cam-shaped plate 80 and the orifice opening 82 can be changed appropriately depending on the function.

It is also possible to configure the orifice as shown in FIG. In FIG. 26, airflow through various sized openings 112, 114, 116, 118 and 120 is controlled by a plurality of solenoid valves 110. If desired, these openings can be made equal in size. In any case, appropriate combinations of these openings provide maximum, minimum and intermediate orifice effective areas. Such an orifice is described, for example, in the US patent specification (No. 3726296,
3746041, 3772877, 3785389, 3875955). By using a program that includes theoretical and experimental equations, a relational equation between the total effective area of the orifice and the pressure inside the drive manifold can be obtained. This quasi-experimental relationship is as shown by characteristic curve 122 in FIG. During the random vibration test, by appropriately selecting a non-uniform pseudo-random distribution of the total effective area of the orifice from the characteristic curve shown in Fig. 27, it becomes possible to obtain a uniform pseudo-random distribution of the pressure inside the drive manifold. .

〔Effect of the invention〕

As explained above, in the present invention, feedback is provided between the vibrating body assembly that holds the test object and the vibrating device provided in the vibrating body assembly for vibrating the vibrating test body. A mold control section is coupled to the feedback control section, and this feedback control section detects the vibration level of the test object and provides control information corresponding to the detected vibration level to the control section. Based on this control information, it is possible to control the vibration device to reliably vibrate the test object quasi-randomly in multiple directions.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a vibration testing device according to an embodiment of the present invention, and FIGS. 2, 3a, and 3b are schematic diagrams of vibration transmission in the vibrating body assembly used in the device of FIG. Illustration, Part 4a
Figures 4f to 4f are vibration characteristic diagrams of the vibrating body assembly used in the apparatus of Figure 1, Figures 5a and 5b.
The figure is an explanatory diagram of different free vibration modes of the beam, 6th
Figures a and 6b are explanatory diagrams of different vibration modes of the beam when node/point control is applied.
Figures 10 to 10 are specific configuration diagrams of the vibrating body assembly used in the device shown in Figure 1, and Figures 11 to 1
Fig. 6 is another specific configuration diagram of this vibrating body assembly, and Fig. 17 shows the spectral density of vibration energy when node/point control is applied and not applied to the vibrating body assembly shown in Figs. 11 to 16. 18 is a comparative explanatory diagram of the spectral density of vibration energy obtained when the degree of coupling of the coupling members of the vibrating body assembly shown in FIGS. 11 to 16 is changed, and FIG.
FIGS. 20 to 22 are explanatory diagrams of the configuration of the orifice with variable effective area, and FIGS. 23 to 25 are
Illustration of the method and information used in forming the cam used in the orifice shown in Figure 2.
FIG. 6 is an explanatory diagram of an orifice having individually controllable openings and a variable effective area, and FIG. 27 is an explanatory diagram of a method of forming the orifice with a variable effective area shown in FIG. 26. 20... Vibrating body assembly, 22... Compressed air control section, 24... Drive circuit, 26... Microprocessor, 28... Feedback and protection circuit, 34... Vibrating section, 36... Drive section, 38... Driven section, 40... Elasticity Element.

Claims (1)

[Scope of Claims] 1. A vibration testing device comprising a vibrating body supporting a test object and a vibrating device coupled to the vibrating body and operating to give vibration to the test object, comprising: A mechanism is coupled between the vibrator device and the test object to automatically vary the output, thereby increasing the randomness in the multi-axis vibrations and generating quasi-random simultaneous multi-axis vibrations in the test object. A vibration testing device, wherein a closed loop device is coupled between the vibrating body and the vibrating device to detect and control a level of multi-axis vibration. 2. A vibration device driving means is coupled to the vibration device, and the closed loop device includes a detection means for detecting a vibration input to the test object, and a detection means for comparing the vibration input detected by the detection means with predetermined vibration input information. , a comparison means for generating an error signal based on the comparison result, an error signal processing circuit for processing the error signal from the comparison means, and an error signal processing circuit coupled between the error processing circuit and the vibrating body device driving means, and a 2. The vibration testing device according to claim 1, further comprising a control circuit that controls said driving means in accordance with an output signal from a signal processing circuit. 3. The vibration testing apparatus according to claim 2, wherein the error signal processing circuit includes means for temporally averaging the vibration output from the detection means. 4. The vibration device is constituted by a pneumatic vibration device coupled to a compressed air supply source, and compressed air is periodically supplied to the pneumatic vibration device through at least one orifice of variable effective area. The vibration test device according to item 3. 5 an air pressure regulator coupled between the compressed air source and the orifice, the air pressure regulator being controlled by the error signal processing circuit to change the effective area of the orifice at a time required to change the effective area of the orifice; 5. The vibration testing apparatus according to claim 4, wherein air having an averaged flow velocity and pressure is supplied to the orifice over a sufficiently long period of time. 6. The closed loop device is coupled to the detection means and includes abnormal state detection means for detecting that vibration energy is applied to the test object with an abnormally large acceleration; and the closed loop device is coupled to the error signal processing circuit and detects the vibration operation time setting means for setting the time at which the device should be operated; and an operation time setting means coupled between the vibration energy supply means and the error signal processing circuit, when an abnormal state is detected by the abnormal state detection means, or when the time setting means A vibration test device according to any one of claims 2, 4, and 5, further comprising a protection means for stopping the operation of the vibration device when a set vibration operation time has elapsed. Device. 7. The vibration according to claim 1, wherein the vibrating body includes a driving section, a driven section that holds the test object, and an elastic structure that sets the vibration mode of the driving and driven section. Test equipment. 8. The vibration testing apparatus according to claim 7, further comprising a vibration control device coupled to the vibration device and controlling vibration characteristics imparted to the test object. 9. Claim 8, wherein the resilient structure has inherent hardness and damping properties, and the vibration control device includes a mechanism coupled to the resilient structure to control the stiffness and damping properties of the resilient structure.
Vibration test equipment as described in section. 10 The vibration energy imparted to the test object is represented by a vibration spectrum based on vibration frequency and vibration acceleration, the elastic structure has nonlinear vibration transfer characteristics, and the selection between the driving and driven sections is a plurality of elastic sections disposed at desired positions to control vibration transmission from the driving section to the driven section; thereby selectively setting a vibration acceleration range at a predetermined vibration frequency; The vibration testing device according to claim 9, wherein transmission of vibration energy outside the vibration frequency range is prohibited. 11. The vibration testing apparatus according to claim 10, wherein the elastic structure cooperates with the vibration section to change a limit value of vibration acceleration in accordance with a change in vibration mode. 12. Claim 11, wherein the elastic structure is provided with means for controlling the pressure applied to the elastic body.
Vibration test equipment as described in section. 13 said drive and driven sections are coupled via coupling means to a fixed body and a drive section, respectively, for selectively limiting vibrational displacements of said drive section and relative vibrational displacements between said drive and driven sections to Claims comprising means for generating points and local node points to increase the fundamental frequency and harmonic frequencies of vibrations induced by vibrational energy and to change the frequency content and number of vibrational modes of the vibrational spectrum. The vibration test device according to item 9.