DE2444101B2 - PROCEDURE AND ARRANGEMENT FOR VIBRATION CONTROL - Google Patents

Description

information to generate a continuous control signal, whose duration is greater than that of the scanned frame. Therefore slower * Jj can ation ..veniger elaborate calculators to perform "the Fourier Transforn and the comparison operations are used. All elements to random machine involved in the processing of the measurement signal of the control loop so orauchen only intendUweise to act, whereby the structural and functional effort of the overall control system can be significantly reduced.

During operation, the content of the memory is periodically updated on the basis of new information frames taken from the comparison of the actual PSD with the reference PSD explained at the beginning. The invention allows the multiple use of a single frame of the scanned information, so that the can be carried out more slowly with the reactions from the time domain to the frequency domain and vice versa associated arithmetic operations as ia ^c applying the frame of the control signal to the vibration device.

In order to minimize discontinuities between "Jen successive actuating signal frame in the invention is a signal processing takes cutout such that successive frames Stellsigna :, are multiplied by a known function, and thereafter additively superimposed on the.

In the following, exemplary embodiments of the invention are explained with reference to the drawing. In the Drawing shows

F i g. 1 is a block diagram of the overall arrangement for Vibration control,

Fig. 2 is a block diagram of the random machine

according to Fig. J,

Fig. 3 shows an embodiment of the in I-Ί g. 2 shown statistical number generator,

4 shows a block diagram of the section or frame processing device.

F i g. 5 shows a series of waveforms for illustration the operation of the section processing device and

6 is a block diagram of an alternative embodiment of the statistical number generator.

In the following an arrangement and a method for controlling a vibration testing device, e.g. B. a vibrating table described. With the help of the system described, a test object can vibrate in or on the vibration device with a predetermined spectrum, e.g. B. a given power spectral density (PSD) or car spectral density are subjected. The description of the arrangement is based on a vibration device, e.g. B. a vibrating table; however, it is clear that both the arrangement and the method can be used to control a vibration device which is used, for example, for high-intensity acoustic testing and other acoustic testing processes. The terms "shaking device" or "shaking system" refer to any one of numerous vibration test units, as are known in the art to subject test specimens to acceleration force or vibration. The term "statistical signal" is also used in the following description This term should also - as far as I have expressly excluded - pseudo-statistical signals that are digitally generated.

₄₀ The in F i g. 1 is illustrated arrangement rmt exception of random machine 28 and the cutout processing device similar to the S described in US-PS 37 10 082 constructed ^v stem 29th The arrangement according to FIG. 1 comprises a vibration device 10 which is used to subject a test object or a test object 11 to vibratory oscillations. A scanning device 12, which is coupled to the test specimen 11, scans the vibrational oscillations to which the test specimen 11 is exposed. Normally known accelerometers or other scanning devices can be used for this purpose. The sampled vibratory oscillations are transmitted to an analog / digital converter 14, in which they are converted into digital form. The results of the conversion into digital form are then fed to a PSD processing device 16 in which the digital signal coming from the converter 14 is converted into a frequency domain representation, for example using Fourier transformation, and the spectral power density PSD to which the test object is exposed is calculated.

Numerous known computers can be used to obtain the PSD or other frequency domain representation. Such a computer is given in US Pat. No. 3,638,004. This computer can also be used to carry out the inverse Fourier transformation (converter 26). Other algorithms that can be used to perform the time-domain-frequency-domain conversion and for converting from the frequency domain to the time domain are described in "An Algorithm for Machine Computation of Complex Fourier Series," Math of Computation, Volume 19, pp. 297-301 , April 1965, by Cooley and Tukey, and in Franklin Institute Journal Volume 233, April 1942, by Danielson and Ta η czos. In US-PS 36 38 004 an analog / digital converter is also specified, which can be used as an analog / digital converter 14.

In the case of arrangements of the type shown in FIG. 1, a limited information sample or sample, which is hereinafter referred to as a frame is referred to, processed in the various computing units. For example, with the analog / Digital converter 14, the vibration oscillations, which the test object 11 over a predetermined period of time is exposed, and the converter 14 converts the scanned information into a plurality of the Frame forming digital words. In the embodiment described, a frame of approximately 500 digital words are used, each digital word having several bits, e.g. B. 16 includes.

The actual PSD is in a PSD comparator 18 with

compared to a reference or target PSD, the latter

■ is stored in a reference PSD Ceber 20. Of the

Encoder 20 can be used as an ordinary memory

Storage of digital information be designed,

during the PSD Ve; same one to carry out

the comparisons of suitably programmed digital computers

, can be. Various comparison operations are in

Speaks 4 and 17 of US Pat. No. 3,710,082. as

I'SD Compare! · 18 and multiplier circuit

(I-ig. I) commercially available computers, e.g.

the Model PDP-11 from Digital Equipment Corporation

s or "Super-Nova" from Data General Corporation

or the Model 620 / S from Varian Corporation will end.

A statistical phase angle generator 24 can be used as

24

any device for generating a statistical Number or a pseudo-statistical number, wherein in the described embodiment the statistical or pseudo-statistical number is developed in digital form. Various methods and S Circuits can be used to generate a pseudo random signal. A suitable one Circuitry that is used in the random machine or in the statistical distributor 28 is shown in FIG. 3 shown. Methods for generating a statistical and pseudo-statistical signal are in »Random-Process Simulation in Measurements "by Granino A. Korn (McGraw-Hill Company publication).

The angle generated by the statistical phase angle generator 24 is compared with that in the PSD comparator 18 generated comparison results combined, namely in the described embodiment by multiplication in the multiplier circuit 22. The multiplier circuit 22 may be a separate digital unit or can be provided as part of the PSD comparator 18. In the embodiment described, a statistical phase angle is only four possible values are used. These values are chosen arbitrarily with +/- 45% and +/- 135%, and the Digital signals representing this angle are sequentially applied to the multiplier circuit 22. To the The explanation is simplified by the control signals and in particular those for applying these signals to the Multiplier circuit 22 and timing signals used to control the remainder of the arrangement not shown. For a precise analysis of the mathematical processes involved in generating the pseudo-statistical Signal using four phase angles and applying them to an arrangement of a comparable genre, reference is made to "A Digital Control Vibration or Acoustic Testing System" by Charles L. H e i ζ m a η, in Proceedings of the Institute of Environmental Sciences, Meeting on Environmental Testing, Anaheim, California, April 20-23, 1969, Pp. 287 to 409.

The multiplication results of the multiplier circuit 22 are converted by a frequency / time domain converter 26 using the inverse Fourier transform into a time domain function implemented. The output signal of the converter 26. that from a control signal for the vibration device 10 representing information frame is, via a line 54 to the random machine or to the statistical distributor 28 or to a section processing device 29. In known arrangements the output signal from converter 26 was transmitted directly to digital / analog converter 30 and used in analog form as a control signal for the vibration device 10.

The random machine 28 forms a device for the statistical arrangement of the output signal of the converter 26, such that a single frame of information is used by the converter 26 to generate a plurality of Control signal frame is used, which is transmitted via the line 55 to the digital / analog converter 30, there in converted into analog form and then used as a control signal for the vibration device. As will be explained below, the section processing device 29 is used for smoothing the transition between the frames. Due to the invention deviating from the prior art The processing device 16, the comparator 18, the multiplier circuit 22 can be arranged and the converter 26 can be operated with slower cycle times and therefore less expensive « Components included, with a Rege development of the vibration device 10 with a continuous borrowed statistical signal is guaranteed. There; The method described is particularly useful there moderate, where the test item 11 shows a stable or unchangeable behavior under test conditions and wc the transfer function of the test object and that of the vibration device are essentially constant stay or change slowly over time.

To explain the functionality of the random machine or the statistical distributor, the mathematical principles of the results obtained with the unit 28 are briefly explained below. It is initially assumed that Xt (ω) is the Fourier transform of a single frame of the control or actuating signal that is obtained in the time domain by the converter 2t. If a large number of frames are to be formed from the single frame, the following results for the 1st frame:

.Y, ('- Ic

I., I I

where IT is the delay associated with the / th frame and ir; is the amount by which the / th frame is rotated. If the information in the frame is subjected to a circular shift that is uniform from frame to frame, then τι = locT, where rtT is the shifting step of each frame. It can be shown that the resulting spectrum is 5 (ω) with

LT

like folüt kuHcl:

LTl '

sin., (■ / Il

! sin <■, {.1 ⁱ Il

The variable representing the ratio of the two sine functions in equation (2) causes a modulation or spike formation with periodic peaks at frequency intervals of 2.τ / (α -t-1) T of the spectrum. Therefore, when the information in the frame is rotated or shifted by a constant amount, the frame sequences give a jagged spectrum, which as such is undesirable because a continuous smooth function is required. On the other hand, if τι is statistical and independent of /, the resulting spectrum is defined by the following equation:

From this equation it can be seen that by repeated statistical shifting of the in one Information contained a plurality of frames on the basis of the information contained in a single frame Information contained in individual frames can be formed, whereby the desired output signal can be developed is. This function is of the in Fig. 2 developed the random machine shown.

According to FIG. 2, the random machine or the

statistical distributors on a circular memory 32, which over the line 54 a data input frame records. The circular memory leaves the information contained in the frame continuous word for word • Circulate via line 52, clock pulses determining the circulation rate being supplied via a line 50 will. Various types of storage, including dynamic storage, can be used as circular storage be used. The output of the memory 32 is also applied to an input terminal of a AND logic element 36 applied. The other input terminal of AND gate 36 is with the output of a comparator 40 and an input connection of an AND logic element 34 tied together. The other input connection of the AND gate 34 is connected to the clock signal line 50. The output of the AND logic element

34 is connected to an N- \ counter 44. The N- 1 counter 44 is an ordinary digital counter that can count up to N-1. N is the number of words in the information frame received by the circular memory 32 via the input line 54. The content of the / VI counter 44 is queried by a decoder 46. As soon as this decoder determines the number N- 1 in the N- 1 counter 44, with the next clock pulse it develops a reset signal on the line 48, which resets a counter 38 and acts on a statistical number generator 42 in such a way that it sends a number to the comparator 40 transmits. The comparator 40 compares the content of the counter 38 with the number applied by the statistical number generator 42 and, if the two numbers match, develops an output signal which is transmitted to the AND gates 34 and 36. The output signal of the AND logic element 36 is fed to a digital buffer circuit 35, the output signal of which is present on the output line 55. Any device for generating a statistical or pseudo-statistical number, e.g. B. the in F i g. 3 can be used. The numbers generated by generator 42 are preferably between 0 and N.

The circuit elements according to Figure 2, such as the UN D gates 34 and 36, the counters 38 and 44, the decoder 46, the comparator 40 and the buffer circuit 35 can be conventional digital circuits be.

If, during operation, a single information input frame is sent to the circular memory 32 via the line 54 is supplied, under control of the clock pulses supplied on line 50 takes place a continuous Circulation of the information frame. The AND logic element 36 is continuous with the content of the memory is activated, but this is not transferred to the buffer circuit 35 until a signal from the comparator 40 is received. Assume that when the operation begins, a reset pulse is sent to the Counter 38 and the statistical number generator 42 is applied. This solves the counting operation of the counter 38 and the statistical number generator applies a statistical number to the comparator 40. If the Number in the counter 38 matches the number pending at the comparator, a fade-out signal is sent from Comparator 40 applied to the AND logic element 36, which the information in the circular memory about the AND gate 36 into the buffer circuit

35 fades out. Under these conditions that will also be

AND gate 34 is set, and the N- 1 counter 44 begins to count. When the N- 1 counter 44 has counted to N- 1, the counter 38 is reset to zero on the next clock pulse and another statistical number is applied to the comparator 40 via the generator 42. The operation repeats itself, and when the number in counter 38 again matches the number developed by statistical number generator 42, those in memory 32 become

ίο words forming stored information frames transmitted via the AND logic circuit 36 to the buffer circuit 35. It is clear that with each of the Generator 42 developed a new number, another word forming the frame as the first word for buffer sounding 35 is transmitted. In this way, each information frame is created based on the dem Circulating memory communicated original frame statistically distributed, whereby a control signal with the desired spectrum on output line 55 is developed.

The circulating memory is periodically supplied with new information via line 54. Dahei The processing device 16, the comparator 18, the multiplier circuit 22 and the converter can be used 26 according to FIG. 1 work at a slower speed than known systems, although the Vibration device 10 provides a control signal with the desired spectral content will.

In the circuit according to FIG. 2, the timing signals on line 50 can have a higher value Repetition frequency as the timing signals used in the rest of the arrangement are operated to one relatively continuous data flow to the buffer circuit

.15 35 guarantee.

According to FIG. 3 shows the pseudo-statistical number generator which can be used as generator 42 in FIG 25-B: t shift register 58. The information in the shift register is transmitted with the frequency of the di < Line 66 fed clock pulse sequence shifted this clock frequency differs from that described Embodiment depends on that of the pulse train on line 50. The content of the 25th level of the register is connected to the input terminal of an inverter 60 and ai is an input terminal of an OR operation limb 63 created. The contents of the third slide register level is connected to a terminal of an OR gate 64 and to the input terminal a Inverters 61 applied. The other connection de

so OR gate 63 is connected to the output of inverter 6. The other input terminal of the OR Member 64 is connected to the output of inverter 6. The outputs of the OR gates 63 and 6 are to the input connections of an OR-Ver

Linking member 62 out, and the output of the OR gate 62 is via a line 68 with the Entrance, d. H. connected to the first stage of the shift register. Due to the arrangement of the in Fig The circuit shown contains the shift register 5i

to a pseudo-statistical number, if the information is shifted into the shift register and fed back via the Leituni 68 to the first stage of the register. Other known circuits can be used to generate the statistical number in the arrangement according to FIG

6ς can be used. The positive and negative who a single number can be used if the determination of the sign is subject to chance A single number and zero can be used

when the choice between these two is made at random.

In Fig.6 is an alternative embodiment of the statistical number generator shown, which in this embodiment is an analog noise generator 90 has. This generator is a known device for generating a Noise. The noise generated by the generator 90 is applied to an analog-to-digital converter 91, in FIG which it is in accordance with clock pulses periodically supplied via line 92 or in accordance with of the reset signal on line 48 (Fig. 2) is sampled. The digital output signal of the Converter 92 is stored in a downstream output register 93. The output signal of the register 93 is transmitted via a line 94 to the comparator 40 of the arrangement according to FIG. 2 supplied and serves there as a comparison component for the comparison with the number generated by the counter 38.

The in F i g. 1 designated by 29 section processing device takes over a single frame of the setting information and forms a sequence of Frame for driving the vibrating table 10. The cutout processing device takes input information via line 54 from converter 26: s and sends an output signal to converter 30. The section processing device 29 can also receive input information from the random machine 28 process, the output signal of the random machine not directly to the converter 30, but via the line 55 is led to the section processing device 29. The output of the appearance processing device 29 is then converted into analog form by the converter 30. In the described embodiment, the information is from the Random machine 28 is applied to the section processing device 29, and the output signal of the After conversion into analog form, the section processing device is used as a control signal for the vibrating table 10 used.

In FIG. 5, to which reference is first made below, a schematic signal representation is shown to explain the mode of operation of the section processing device 29. The horizontal lines 84, 85, 86, 87 and 88 represent time axes, with the ^ s line 89 representing the time t = 0. It should be noted that the damage image according to FIG. 5 represents information in analog form, while the section processing device 29 is actually processing digital information. The control signal is shown on the line 88, which was thus formed either from a single frame or from the signal from the converter 26 (FIG. 1) or from a series of frames picked up by the randomizing machine 28. The information on the line or axis 88 is used after conversion into analog form ss (converter 30) as a control signal for the vibrating table 10. It is initially assumed that the input signal of the section processing device 29 consists of an information frame derived from the output of the converter 26. This single frame is _{shown repeatedly on lines <, 0} 84, 85, 86 and 87. The amplitude of the information frame was determined with a known function, e.g. A sine function, multiplied to define the envelopes 82 of the frames. The frames are Jv: n as shown in FIG. 5 in such a way that the information on the lines 84, 85, 86, 87 forms the information shown on the axis 88 after the additive superposition. For example, the frame shown on the line 85 is added to the information on the line 84 starting with the midpoint of the frame on the line 84. Similarly, the frame shown on line 86 is added to the frame on line 85, starting approximately at the midpoint of the frame shown on line 85. In the event that a sequence of frames is applied to the section processing device 29 by the random machine 28, the summation and multiplication with a known function for the formation of the envelope curves 82 takes place in the same way, in this case the on the lines 84, 85, 86, 87, however, previously subjected to a statistical arrangement by the unit 28.

The clipping processing means is shown in FIG. 4th shown schematically. It has two circular spokes! 71 and 72 on. The memory 7t stores the information circulate the line 74, while the information circulation in the memory 72 via the line 7? he follows. There> The output signal of the circulating memory 71 is fed to an amplitude control device 77, while c the output signal of the circulating memory 72 is applied to an amplitude control device 76. the Amplitude of the signals in the amplitude control devices 76 and 77 is controlled by means of a function generator 80. The output signals of the amplitudes Control devices 76 and 77 are applied to a summing circuit 79 in which they sum will. Timing signals are applied to the various components of the circuit shown in FIG at. which are each supplied via a Le hung 69. For the circuit elements of FIG ordinary electrical circuits are used.

The function generator 80 generates! {\ n ji> ^T it;:! ei form) a function corresponding to the envelope curves 82 in FIG. 5. The exemplary embodiment described is a sine function. It is clear that the function generator 80 must generate a signal with a first and a second phase of a function. In the case of the sine function, one signal is 90 'out of phase with the second signal. One of these signals is applied to the amplitude control device 77 and the other to the amplitude control device 7 (. The amplitude control devices 76 and Ti can be multiplier circuits which multiply the signal from the function generator with the signal from the circulating memory.

The section processing described can also be used take place in that only the beginning and the end of a repeated frame were to be pointed, only the pointed portions of the repeated would be arched Frames can be overlapped to develop a continuous signal. At dcrr described embodiment are the sum of the squares of the overlapping portions equals 1. Therefore, the beginning of a frame can have a taper and the end of the frame can be Have cosine taper. If the end of a frame coincides with the beginning of another frame or of a repeated frame is summed, the Sums of the square, d. H.

sin- ¹ Θ + cos ^: B = I.

This ensures that the information sent to the Riiulersystcm applied "performance" has no peaks or falls in the frame periods.

It is assumed for explanatory purposes that the section processing device 29 according to FIG. 4 is used in the arrangement according to FIG. 1 without the random machine 28. In this case, a single information frame is applied to the two circular memories 71 and 72 by the converter 26. At time t = 0, the information recorded by the circulating memory 71 is applied to the amplitude control device 77, the predetermined function, e.g. B. a sine function, is simultaneously applied by the function generator 80 to the amplitude control device 77. The output signal of the amplitude control device 77 is fed to the summing circuit 79. Their output signal corresponds in digital form to that on line 84 in FIG. 5 waveform. After approximately half of the frame stored in the memory 71 has been read out from the memory, the frame stored in the circular memory 72 is also read out to the amplitude control device 76. The function generator 80 in turn ran a predefined function which is used to define the envelope curve 82 in FIG. 5. The output signal of the amplitude control device 76, which corresponds, for example, to that on the line 85 em, is summed in the summing circuit 79 with the output signal of the amplitude control device 77. While the information from circulation ^c , 71 and

72 is read out, it is read out via the lines 74 or

73 and can then be read out again. The output of the summing circuit 7-t is that on line 88 in FIG. 5 signal shown, which after conversion into the Analog form is used as a control signal for the vibrating table 10.

In the preferred embodiment, the information is from the random machine or the statistical Distribution unit 28 to the cut-out processing unit 29 and not applied directly to the digital / analog converter 30. When the clipping processor is used in conjunction with the random machine 28, those from the random machine 28 supplied frames are alternately applied to the memories 71 and 72. In this mode of operation, the Memory 71 and 72 not as a circulating memory, but as ordinary memories are operated, and the information once read is not circulated. The frames alternately supplied to the memories 71 and 72 are shown in FIG. 5 illustrated manner read out from the memories with mutual phase shift, the amplitudes of these signals can in turn be combined with a known function from the function generator 80 to generate the Envelope curves 82 according to FIG. 5 to be defined.

Reference is again made to FIG. 1 below. In operation, the converter 14 sets the from the sampled signal from the sampling device into a digital signal which is sent to the processing device 16 is created. In the preferred embodiment, a single frame is generated by the translator 14 The information provided is used to calculate the PSD to which the test object is exposed. This PSD will is compared in the comparator 18 with the reference PSD, and the comparison results are stored in the multiplier circuit 22 compared with a statistical phase angle generated by the generator 24. The multiplication results are then converted into a time domain function in converter 26, and this function is applied to the feed machine 28 and in this before being applied to the cutting processing device 29 statistically arranged. A large number of frames of the control or actuating signal is used by the Random machine 28 for developing a continuous control signal for the vibration device 10 submitted. The converter 26 periodically sets a continuously updated information frame at. which replaces the information previously stored in the random machine 28 and the development A further group of control frames is made possible by the random machine 28.

The described arrangement for vibration control thus enables the multiple use of a single rule information frame to develop a continuous one Control signal, because "> has the desired spectral content and a high randomness level contains.

3 blue drawings

Claims (6)

Patent claims: 1. Arrangement for vibration control with a movement of a test object or a vibration device scanning measuring device, one a control signal consisting of several digital words as a function of a comparison between the measured spectrum and a given one Spectrum-generating computing device and a continuous control signal emitting ι ο Device, characterized in that the computing device (16 ... 26) has a continuous Developing control signal from a predetermined section (control frame) of the control signal Random machine (28} is downstream, the tinen the control frame storing memory (32), a statistical generator (42) and one connected to the memory and the statistical generator Control circuit (34-36, 38,40, 44,46), wherein the control circuit is designed so that the Control frame under a statistical arrangement, each with a different one from the statistical generator A word selected as the first word for the formation of the continuous control signal from the Memory (32) can be read out. 2. Arrangement according to claim 1, characterized in that that the memory consists of a circulating memory (32,52) for the control frame. 3. Arrangement according to claim 1 or 2, characterized in that the content of the memory (32) periodically replaceable by a new control frame consisting of several digital words. 4. Arrangement according to claim 1, characterized in that the computing device (16 ... 26) or random machine (28) is followed by a digital data frame receiving section processing device (29) which has a function generator (80), one at least the beginning and the end section a first digital data frame with a predetermined function-multiplying circuit (76, Ϊ7) generated by the function generator and a summing circuit (79), the summing circuit being designed so that in each case at least one end section of a frame (84) with the beginning section of a subsequent frame ( 85) can be summed. 5. Method for regulating the movement of a vibration device with a statistical signal for Generation of a predetermined power spectral density, initially the movement of the so Spectral power density representing vibration device with a predetermined spectral Power density compared and generated a digital signal characterizing the comparison result is, wherein further a statistical signal is generated and wherein the comparison signal and the Statistical signal converted into a statistical control signal of predetermined duration in time domain form ./ t is, characterized in that the control signal of a predetermined duration by statistical arrangement <*> is processed into a continuous, statistical control signal with which the movement of the Vibration device is regulated. 6. The method according to claim 5, characterized in that that successive frames of the control signal are multiplied by a known function and then additively superimposed. The invention relates to an arrangement for vibration control with a movement of a Test object or a vibration device scanning measuring device, one of several digital words existing control signal as a function of a comparison between the measured spectrum and a predetermined spectrum generating computing device and emit a continuous control signal the facility. . The invention also relates to a method for regulating the movement of a vibration device a statistical signal for generating a predetermined spectral power density, with initially a the spectral power density representing the movement of the vibration device with a predetermined one compared spectral power density and generated a digital signal characterizing the comparison result and a statistical signal is also generated! and wherein the comparison signal and the statistical signal are predetermined in a statistical control signal Duration is implemented in time domain form. In US-PS 37 10 082 is a vibration control system described in which the vibration oscillations, which a test object in a vibration device is exposed, scanned and converted into a digital sign; il implemented. The digital signal is converted into a Frequency range representation implemented. In addition, a spectrum of the frequency domain is displayed. ζ. B. the power spectral density (PSD) calculated. The actual PSD to which the test object is exposed is then mn a target or reference PSD is compared, and the results of this comparison are e.g. Combined with a statistical signal using a multiplier circuit. The results of this combination are then, for example, using an inverse Fourier transform into the time domain function implemented and used in analog form as a control signal for the vibration device. The invention has for its object to improve the known from US-PS 37 10 082 vibration control so n \ that the continuous actuating signal can be generated even without transmission of a continuous flow of information throughout the entire control circuit. The invention proposes to solve this problem in an arrangement of the type mentioned that the computing device receives the continuous control signal from a specified section (control frame) the random machine developing the control signal is connected downstream, which one the control frame storing memory, a statistical generator and one with the memory and the statistical Generator connected control circuit, wherein the control circuit is designed so that the Control frame under a statistical arrangement, each with a different one made by the statistical generator Selection of a word as the first word to form the continuous control signal from the memory can be triggered. For the method of the type mentioned, it is proposed according to the invention that the control signal specified duration by statistical order: / 11 a continuous, statistical control signal is processed, with which the movement of the vibration device is regulated. The invention makes it possible, from just one frame, to obtain those scanned by the test object or test object