JPH0123725B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a dynamic characteristic measuring device for a mechanical structure or a control device, and particularly relates to a periodic wave excitation method for evaluating the dynamic characteristics of a target system using periodic wave excitation. Regarding analysis equipment.

[Conventional technology]

Conventional frequency characteristic analyzers using sine wave excitation include analog types using a tuning filter method and digital types using a Fourier transform method that processes measurement data in digital quantities. The former is usually 5Hz to 5000
It is represented by the frequency range of Hz, and the latter particularly has the characteristic of covering the low frequency range of 1 Hz or less.

These conventional analysis devices are two-point frequency transfer characteristic analyzers, typically called mechanical impedance analyzers, transfer characteristic analyzers, or servo analyzers.

[Problem to be solved by the invention]

The drawback of the conventional method is that it can only determine the transfer characteristic between two points to be measured.

The purpose of the present invention is to evaluate the frequency characteristics of a mechanical structure or a control system using a sine wave input in a system that evaluates the frequency characteristics of multiple points simultaneously and at high speed, without being limited to two specific points to be measured. An object of the present invention is to provide a frequency characteristic analysis device using periodic wave excitation for analysis.

[Means for Solving the Problem] The above object is to provide an output memory section in which frequency data is stored, a D/A converter that converts a digital signal of the frequency data in the output memory section into an analog signal, and a An A/D converter that converts into a digital signal an analog signal of a response value obtained by exciting a measurement object by the output signal of the A/D converter, and an acquisition memory unit that acquires the digital signal of the A/D converter. , a periodic wave excitation analyzer comprising the D/A converter and a clock oscillation section for controlling the A/D converter, the periodic wave excitation analyzer being provided between the D/A converter and the clock oscillation section; a first frequency divider that divides the frequency of the output clock of the clock oscillation section for output; and a first frequency divider that is provided between the A/D converter and the clock oscillation section, and that divides the output clock of the clock oscillation section for acquisition. This is achieved by including a second frequency divider that divides the frequency.

[Effect]

Since frequency dividers with different frequency division ratios are provided between the D/A converter, A/D converter, and clock oscillation section, it is possible to acquire multi-channel data.

〔Example〕

The background that requires the simultaneous measurement of the present invention will be explained with reference to FIGS. 1 and 2.

In FIG. 1, a control system 10 has an input section 2, a control element 4, a controlled object 6, and an output section 8.
In order to clarify the frequency characteristics of
By measuring 18 and 20 simultaneously, 46
The individual characteristics of the control system 10 or the input/output characteristics of the control system 10 can be evaluated.

In FIG. 2, the excitation system 40 consists of an input section 2, an excitation control circuit 30, an excitation machine section 32, an excitation specimen 34 connected to this 32, and feedback signals 36 and 38. 40, the periodic wave oscillator 12 is attached to the input section 2, and in order to obtain the frequency characteristics of the mechanical structure of the excitation specimen, an excitation state measurement quantity 42, a plurality of response measurement quantities, for example 44, 4
It is necessary to measure 6 and 48 simultaneously.

The present invention enables simultaneous multi-point analysis at high speed using a digital method, and performs frequency characteristic analysis using periodic wave excitation by performing fast Fourier transform (hereinafter abbreviated as FFT) with a small number of data points.

The present invention will be explained with reference to FIG. 3 by way of an example.

In FIG. 3, the periodic wave oscillator 12 that supplies the input part of the target system whose frequency characteristics are to be analyzed is shown as an output data block that stores periodic wave data with a periodic wave number l (an integer of l≧1) and a data length N _D. 60, a clock oscillation unit 62 which has the data value of the block inside or outside the device, an analog counter 64 for controlling the output data with the output clock pulse of the frequency dividing unit 63, and a D/A conversion for converting the data into analog. 66, a periodic wave signal 70 which is the output signal of the filter 68, and a frequency-voltage (F/V) converter 7 that converts the clock frequency into voltage.
2, the output frequency signal 74, and a frequency divider 76 that divides the output clock of the clock oscillator 62 for acquisition.
Channel measurement data 92 is passed through a filter 96, and a multiplexer 98 with a sample/hold circuit is controlled by the output clock 84 of the frequency divider 76.
The acquired data block 104 with the data length N ₁ of each channel acquired through the A/D converter 100 and the number of channels m is captured into the acquired data area 106 .

In this configuration, the data length N ₁ captured in the acquired data block 104 of each channel is determined by frequency analysis using a fast Fourier transform (abbreviated as FFT) method, so N ₁ =2, where n is a positive integer. ⁿ points are required, and the smaller n is, the more
High-speed processing becomes possible. In addition to the fundamental frequency output from the periodic wave output signal 70, the frequency components included in N ₁ are the frequency components of the control system 10 or the excitation system 4.
It contains high frequency components due to distortion due to the non-linear characteristics of 0. Therefore, analysis accuracy is improved by analyzing multiple k-waves rather than by analyzing one wave at the fundamental frequency. Therefore, the data length N ₁ is set so that the number of data points of the fundamental period wave number k wave is 2 ⁿ .

Also, when the number of data acquisition channels is m, A/
The clock to the D converter section is acquired data block 1.
It requires m times as many clocks as the clock required to import into 04.

The output data block 60 stores the l wave (l≧1, even number) of the excitation fundamental wave, and the frequency of the periodic wave output signal 70 when outputting the data is D/A.
It is determined by the 80 position clock rate that controls the transducer. When changing the frequency of the output signal, the pulse rate of the clock oscillator 62 may be changed continuously in accordance with the required rate of change.

In order to reduce the distortion of the output signal 70, it is necessary to increase the data length _N0 of the output data block 60. Further, a method is adopted in which the cutoff frequency of the low-pass filter 68 is controlled by the frequency signal 74 which is the output of the frequency-voltage converter 72. This method also applies to the data acquisition side.
The cutting frequency of the low-pass filter 96 is controlled to prevent data sampling errors.

In such a configuration, the main purpose of the present invention is to provide a means for making the output data block length _N0 as large as possible and reducing the acquired data block length _N1 as much as possible.The reasons why this can be achieved are explained below. explain.

In order to multiply N ₀ by α times N ₁ , frequency divider 7
6, it is necessary to set the clock during acquisition to 1/α.
Furthermore, when the number of acquisition channels is m, the clock rate at the 80th position needs to be multiplied by m, so the clock rate on the output side needs to be 1/m. However, if m is large and the output data block length N ₀ cannot be made large, m is decomposed into m = m ₁ × m ₂ by setting m ₁ and m ₂ as positive integers, and the output data block length N 0 is divided by the frequency divider 63 on the output side. By setting the frequency μ ₀ to 1/m ₁ , the output data block length N ₀ is set to m ₂ times αN ₁ , that is, N ₀ =α·m ₂ ×N ₁ .

Also, the fundamental wave is added to the acquired data block 104.
By acquiring waves, it is possible to improve the analysis accuracy of the acquired data, but when the acquired data block is subjected to FFE processing, frequency leakage occurs due to the finite data length _N1 . In order to reduce this leakage, the wave number k of the fundamental wave component within the data length _N1 must always be an integer.

In order to satisfy this condition, the frequency division ratio μ ₁ of the frequency divider 76 that determines the clock rate for acquisition must be 1/
For α, μ ₁ =1/α×1/h Here, h may be a positive integer determined by k=1·h.

Since the data length of the acquired data block always includes integer waves of fundamental period waves, the data length N ₁ is N ₁ = 2 ⁶ = 64 points if the wave number k = 3 when analyzing only fundamental period waves. It is enough if there is. This is because when FFT processing is applied to N ₁ = 64 data, frequency components can be analyzed up to N ₁ /2 analysis can be performed accurately.

When the data length of the acquired data block is small in this way, it becomes possible to acquire multiple channels, and the data processing time per channel can be shortened.

〔Effect of the invention〕

According to the present invention, it is possible to perform multi-channel data acquisition and high-speed processing of periodic wave excitation analysis.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are diagrams for explaining the present invention,
FIG. 3 is a diagram showing an embodiment of the present invention. 60...Output data block, 62...Clock oscillator, 64...Address counter, 63,7
6... Frequency divider.

Claims (1)

[Claims] 1. An output memory section in which frequency data is stored, a D/A converter that converts the digital signal of the frequency data in the output memory section into an analog signal, and a measurement target using the output signal of the D/A converter. an A/D converter that converts an analog signal of a response value of exciting an object into a digital signal; an acquisition memory unit that acquires the digital signal of the A/D converter; the D/A converter and the A/D converter; In a periodic wave excitation analyzer equipped with a clock oscillator for controlling a converter,
a first frequency divider that is provided between the D/A converter and the clock oscillation section and divides the frequency of the output clock of the clock oscillation section for output; 1. A periodic wave excitation analyzer comprising: a second frequency divider provided between the clock oscillation section and the clock oscillation section for frequency-dividing the output clock of the clock oscillation section for acquisition.