RU2541904C1 - Method for digital generation of continuous random process of arbitrary length - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: method comprises generating a continuous random process of an arbitrary and given length using discrete digital transforms for controlling multiple vibrating tables during tests thereof using cyclically variable buffers for DMA.

EFFECT: faster conversion with fast correction loop.

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Description

The invention relates to methods for creating broadband random processes with predetermined intrinsic power spectral densities and can be used in instrumentation, mechanical engineering, computer technology to create, in particular, multi-channel automatic systems, in tests for vibration resistance to the effects of random vibration, etc.

The generation in the time domain of a random signal x (t), having the normal law of distribution of amplitudes, is carried out according to the well-known algorithm (“Automatic control of vibration tests”, Automation Library, issue 579, M., Energy, 1978) by generating in the time regions based on a given spectrum of amplitudes of the sequence (time block a ₁ ) of real numbers a _1i (i = 0, 1, ..., N-1) in the form of a Rice-Pearson expansion with a sampling step Δt [sec] and converting the resulting sequence into continuous waveform service time ayny signal length T _B = N · Δt = 1 / Δf [sec] is inversely proportional to the step signal amplitudes of the spectrum of the quantization frequency Δf.

All of these features are present in the proposed method. As a rule, when vibration testing of real objects requires the implementation of random processes of considerable length, which creates problems with real-time control with a quick correction loop.

The present invention solves the problem of generating a continuous random process of an arbitrary given length easily implemented on a standard uniprocessor computer by a method of discrete digital transformations that do not require a large amount of computation, time and memory, which is essential when creating control systems in real time with a fast correction loop, for example, for controlling several vibration stands during testing.

A method is proposed for generating a continuous random process of arbitrary length by digital generation in the time domain based on a given spectrum of signal amplitudes of sequences of real numbers a _ri (i = 1, 2, ...; i = 0, 1, ..., N-1) in the form of Rice decomposition -Pearson with a sampling step Δt [sec] (time blocks a _r , length T _B = NΔt); constructing a cosine Hann window at a length T _HANN = (4 · n-3) points (n << N, for example, n = N / 10):

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the formation of a random process from a sequence of successive time blocks a _r (r = 1, 2, ...), joined at the last a _{r, N-1} and the first a _{r + 1.0} points of blocks a _r and a _{r + 1,} respectively, according to the following algorithm: at the end of the block a _r (r = 1, 2, ...) and at the beginning of the next block a _{r + 1} , sequences of points of length n are distinguished, to the end of the block a _r add (n-1) points symmetrical to the last n points of the block a _r, multiplied by the second window half Hanna, to the top of the unit a _{r + 1} is added (n-1) points symmetric first block point n a _{r + 1} multiplied by the left half of the ca. on Hannah, the sequences obtained in blocks a _r and a _{r + 1} are added to obtain the total sequence, the sequences of points of the blocks are replaced so that the last n points of the block a _r are replaced by the first n points of the total sequence, the first n points of the next block a _{r + 1} replaced by the last n points of the total sequence; creating for the output of the control system from separate successive blocks a _{r of a} continuous random signal of the digital ping-pong mechanism: two buffers of length N are organized in the computer's memory, one of which contains the generated data block a _r , which then the direct memory access controller (DMA) without the participation of the central processor is transferred to the memory of the digital-to-analog converter (DAC). During the issuance of the first block a _r to the DAC output, the central processor generates the next data block a _{r + 1} , matches its beginning with the end of the previous a _r and transfers it to the second buffer, which, in turn, will be transferred to the DAC through the DMA channel . Then, the buffers are automatically cyclically swapped, and a random continuous signal of arbitrary length is generated at the output of the DAC.

A distinctive feature of the proposed method is:

construction of a cosine Hann window at a length T _HANN = (4 · n-3) points (n << N):

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the formation of a random process from a sequence of successive time blocks a _r (r = 1, 2, ...), joined at the last a _{r, N-1} and the first a _{r + 1.0} points of blocks a _r and a _{r + 1,} respectively, according to the following algorithm: at the end of the block a _r (r = 1, 2, ...) and at the beginning of the next block a _{r + 1} , sequences of points of length n are distinguished, to the end of the block a _r add (n-1) points symmetrical to the last n points of the block a _r times the second half of the Hann window, add (n-1) points symmetric to the first n points of the block a _{r + 1} times the left half of the window to the beginning of the block a _{r + 1} on Hannah, the sequences obtained in blocks a _r and a _{r + 1} are added to obtain the total sequence, the sequences of points of the blocks are replaced so that the last n points of the block a _r are replaced by the first n points of the total sequence, the first n points of the next block a _{r + 1} replaced by the last n points of the total sequence; creation of a continuous random digital signal "ping-pong" for generating at the output of the control system from separate successive blocks a _r : two buffers of length N are organized in the computer's memory, one of which contains the generated data block a _r , which then the direct memory access controller (DMA) without the participation of the central processor is transferred to the memory of the digital-to-analog converter (DAC). During the issuance of the first block a _r to the DAC output, the central processor generates the next data block a _{r + 1} , matches its beginning with the end of the previous a _r and transfers it to the second buffer, which, in turn, will be transferred to the DAC through the DMA channel . Then, the buffers are automatically cyclically swapped, and a continuous continuous signal of arbitrary length is generated at the output of the DAC.

Due to the presence of this distinguishing feature, in combination with the known ones, it becomes possible to form continuous random processes x (t) of a given arbitrary length.

As a result of a search by sources of patent and scientific and technical information, solutions containing similar features were not found.

Thus, we can conclude that the proposed method is unknown at the level of technology and, therefore, meets the criterion of "patentability".

The proposed method can find application wherever there is a need for continuous random processes of arbitrary length, which allows us to conclude that the criterion of "Industrial applicability" is met.

The method is implemented as follows. At the end of the block a _r (for example, r = 1 is taken) and at the beginning of the next a _{r + 1} , sequences of length n points are distinguished (as a rule, the value of n is insignificant with respect to the entire length of the block of N points, for example, in this example, n = N / 10 = 10), on which the docking phases of the algorithm (1) on a length T _HANN = (4 · n-3) dots is calculated Hanna cosine window (Figure 2):

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To the end of the block a _{r, N-1} add (n-1) points symmetrical to the last n points of the block: a _{1, N} = a _{1, N-2} , ..., a _{1, N + n-2} = a _{1, Nn} . Multiply the resulting sequence by the second half of the Hann window (Figure 3). To the end of the next block a _{r + 1} (point a _2.0 ) add (n-1) points symmetrical to the first n points of the block: a _{2, -1} = a _2,1 , ..., a _2,1-n = a _{2, n-1} . Multiply the resulting sequence by the first half of the Hann window (Figure 4). The converted sequences (FIGS. 3 and 4) are added to the total sequence (FIG. 5). The points of the total sequence are replaced by the points of the original blocks of the points of the blocks a _r and a _{r + 1} so that the last n points of the block a _r are replaced by the first n points of the total sequence, and the first n points of the next block a _{r + 1} are replaced by the last n points of the total sequence (Fig. .6).

Claims (1)

A method of digital generation of continuous random process of any length, including the digital generation of the time domain based on a predetermined range of signal amplitudes sequences of real numbers a _ri (r = 1, 2, ...; i = 0, 1, ..., N-1) in the form of expansions Rice-Pearson with a sampling step Δt [sec] of time blocks a _r , length T _B = NΔt, characterized in that it includes building on the length T _HANN = (4 · n-3) points (n << N) of the cosine Hann window:

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the formation of a random process from a sequence of successive time blocks a _r (r = 1, 2, ...), joined at the last a _{r, N-1} and the first a _{r + 1.0} points of blocks a _r and a _{r + 1,} respectively the following algorithm: at the end of the block a _r (r = 1, 2, ...) and at the beginning of the next block a _{r + 1} , sequences of points of length n are _selected , (n-1) points symmetrical to the last n points are added to the end of the block a _r a _r block multiplied by the second window half Hanna, to the top of the unit a _{r + 1} is added (n-1) points symmetric first block point n a _{r + 1} multiplied by the left half of the for Hannah obtained in blocks a _r and a _{r + 1} sequence is folded to obtain the total sequence, produce a replacement so that the last n points blocks dots sequence block a _r replace the first n points of the total sequence, the first n points the next block is a _{r + 1} replaced by the last n points of the total sequence; creation of a continuous random signal of a digital mechanism for generating at the output of the control system from separate successive blocks a _r , for which two buffers of length N are arranged in the computer memory, one of which contains the generated data block a _r , which is then used by the direct access controller to memory (DMA) without the involvement of the CPU is transferred to the memory digital to analog converter (DAC), for the first time issuing a _r output DAC unit CPU generates the next data block a _{r + 1,} osusches S THE docking its beginning to the end of the previous a _r and transfers to the second buffer, which in turn will be transferred to the DAC to a DMA-channel, then the buffers automatically cyclically reversed, and the DAC output is generated by a continuous time random signal of arbitrary length.

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