Клиначёв Николай Васильевич

MEASUREMENTS OF THE FREQUENCY RESPONSES IN PACKAGES WHICH SIMULATE MOVEMENT

INTRODUCTION

Rating of opportunities of packages, which simulate movement reveals absence either mathematical or measuring tools of research of systems. For example VisSim, allows to execute various kinds of the analysis for models, but the mathematical methods (root and frequency) are used only.  In other words functions of the analysis are accessible only for models consisting from a library blocks, to which correspond, as a rule, linear transfer functions and they are not accessible to models containing nonlinear blocks, logic elements and models of the users written on C++ or Pascal. The described difficulty cardinally can be overcome by development of algorithms as a matter of fact carrying out virtual measurement. The represented library for a package VisSim partially solves this task. Let's note, that if the real object is included in a contour of model, the measurement of its frequency characteristic is possible.


ANALYZER of FR of systems with NOT MODULATED (AM, FM, PWM, ...) signals

Lfi01 – VisSim

 

FUNCTIONAL
BLOCK
PERFORMANCE


gif-file, 2KB

fig.1

PARAMETERS
Dynamic range:
  1) at research of models is limited to a type double
  2) at research of objects is limited to noise: +/-80...100 db
Frequency a range:
  1) at research of models is limited to a type double
  2) is limited to a strip ADC on a DAQ-board
Range of recognition of a phase: -180 < φ < 180
Type of the accrued data: short int, ..., long
Desirable mode of accumulation of the data – asynchronous
The frequency of accumulation of the data – can be < < Nyquist frequencies
(these concepts are not interconnected)
Self-adjustment to scale of a piloted linearly increasing sequences
consisting from: 8, 16..., 256 discretes
Instructions of the processor in a cycle of data accumulation  – 20
Volume of memory of the data: 1024*sizeof(long)
Instructions of the coprocessor for calculation of the module and phase in a point – 1024
The size dll of library - 20 K
The required version of a package VisSim – 3.0

APPLICATION
Virtual measurements in simulating packages
Researches frequency of properties of real objects
The programs to which the adaptation is possible: MVS, Simulink, MBTY...

GENERAL DESCRIPTION

The line "addons32=C:\Vissim\user\AzFqRsp.dll" in a file of initialization of the program VisSim (WINDOWS\vissim.ini) connects library to the menu "Blocks" in which to occur a line "Measuring device: Generator, FR-Analizer". About the block "FR-analizer" further Analyzer it is possible to think, how about a virtual device for measurement of the frequency characteristics (see fig. 1). The functioning of the Analyzer should be provided with the virtual device – Generator, which carries out synthesis of specifying influence of the given frequency and sine wave form (it is desirable). The form of a signal can be anyone. Analyzer reacts only to the first harmonic of a signal. The automatic mode of measurements is carried out by installation of a flag of the multisession modeling (Auto Restart). In the following session the Generator should establish the following frequency in the range, determined by the user. Feature of the Generator is the additional task of synthesis of a piloted linearly increasing sequence consisting from 8, 16, ..., or 256 discrete values, on the same period. The phase of this signal can be anyone, as it pilots (conducts) the Analyzer, which has two channels. Follows as to note, that all specialized generators based on a principle of direct digital synthesis, contain the adder, which output can be used for piloting (conducting). Analyzer is not interconnected with concept "frequency", it receive only samples at the certain discrete value of a piloting signal (phase), and on their set it defines the relation of amplitudes and difference of phases of the first harmonics of entrance signals. The accuracy of definition of the logarithmic module and phases is proportional to time of samples accumulation, and at its essential value it is possible to identify signals whose periods is not identified visually on a background of nonperiodic noise at rigid synchronization of an oscilloscope. The dynamic range of Analyzer can will be reduced essentially at periodic noise in signals (at concurrence of the period of any harmonic of noise to the period of indignation). In table 1 the description of inputs / outputs of Analyzer is given.

Table 1
Pin name Functional description
(int)A Input of the channel A The input signals should belong to a range of the integer type (+ /-2^15) and have the maximal amplitude. The input signal with amplitude is less than one (1) after transformation to the integer type will be zero is will cause a mistake in the Analyzer. The small amplitude of signals reduces resolution of the Analyzer
(int)B Input of the channel B
Lin Input for a piloting signal (linearly increasing sequence)
SYNC Input, positive edge provides recording the data in Analyzer
RE Input, active forward front. Initiates process of calculation of the module and phase and occurrence of their values on outputs "L" and "fi" without reset of the accumulated information
R[..] Input, active high level (1), which resets the accumulated information
Asin, Acos Outputs of orthogonal factors, whose values are used for calculation the logarithmic module and phase (can be absent), are updated on a signal RE
Bsin, Bcos
L Output of the logarithmic module [db], is updated on a signal RE
fi Output of value of phase shift [degrees], is updated on a signal RE

Generator block-circuit

Блок схема Генератора

As shown, at measurement of the frequency response the user should to establish in the Generator a range of frequencies (5..150 Hz), amount of points (40) and attribute of a logarithmic frequency step (button). On the first diagram is shown a piloting signal G_lin consisting from eight discrets for the Analyzer. On the second diagram – synthesized specifying (revolting) signal

fig. 2

Connections of the Analyzer and Generator for measurement
of the FR of one cascade of the discrete filter of the sigma-delta ADC

Подключения Анализатора и Генератора для измерения частотных характеристик

The adjustments of the Generator in experience correspond shown on a fig. 2. The revolting signal is multiplied on 30000, that the signals sent on channels of the Analyzer were in a range of the integer type (int). The virtual time of measurement in a point frequency scales was equaled to 3 seconds, for which was 1000 samples in the channel are collected. The characteristics are given for 40 seconds on the computer with the processor Celeron 333

fig. 3

If you wish to receive library or discuss theoretical questions can to communicate on email with the author Nikolay Vasilyevich Klinachyov. For an own rating and experiments you can take archive (12K). In tab. 2. the comments to its contents are given.

Table 2
Files of archive

Comment

Diagram1.vsm Working file of a package VisSim 3.0 (fig. 2 and 3)
AzFqRsp.dll Demonstration library of the Analyzer, in which the resolution is limited, but for ideal conditions (for computer models) will approach. Use sine wave signals with small amplitude of noise and small contents of harmonics. Take a smaller step of modeling

10.01.2001

 


ANALYZER of FR of systems with NOT MODULATED (AM, FM, PWM, ...) signals

Lfi02 – VisSim

 

FUNCTIONAL
BLOCK
PERFORMANCE


gif-file, 2KB

fig. 4

PARAMETERS
Correspond to Analyzer Lfi01

FEATURES
Simplifications in synchronization
The visual control of the accumulated information
The definition of amount accrued samples
Presence of a signal of readiness of the data (L and fi) – RDY
Automatic end of session of modeling

APPLICATION
Correspond to Analyzer Lfi01


Table 3
DESCRIPTION OF INPUTS / OUTPUTS OF THE ANALYZER BLOCK Lfi02
Pin name Functional description
(int)A Input of the channel A The input signals should belong to a range of the integer type (+ /-2^15) and have the maximal amplitude. The input signal with amplitude is less than one (1) after transformation to the integer type will be zero is will cause a mistake in the Analyzer. The small amplitude of signals reduces resolution of the Analyzer
(int)B Input of the channel B
Lin Input for a piloting signal (linearly increasing sequence)
SYNC Input, positive edge provides recording the data in Analyzer
A[Lin] Outputs for the visual control of the accumulated information per a cycle of measurement in channels of Analyzer. On the given arrays the logarithmic module and shift of a phase is calculated, i.e. the parameters of the first harmonics are identified
B[Lin]
Lin The output is an index for arrays with the accumulated information A [Lin] and B [Lin]. On end of measurement begins to be increased (Lin++), but only in the event that parameter "Expectation" of Analyzer block is not equal to zero see table 4. Otherwise A [Lin] and B [Lin] arrays are not deduced, and the speed of definition of the FR are raises.  At updating an index Lin the data on outputs A [Lin] and B [Lin] are updated. After end of a deducing of arrays the Analyzer block calls a function finishing current session of modeling (end time of  modeling, established by the user is ignored and should be obviously more)
RDY The output of the notification about readiness of the data (L and fi) for indication on the plot (is intended for synchronization of the plot)
L Output of the logarithmic module [db]. The updating proves active high level (1) of a signal RDY
fi Output of value of phase shift [degrees]. The updating proves active high level (1) of a signal RDY

Table 4

DESCRIPTION OF PARAMETERS OF THE ANALYZER BLOCK Lfi02

Parameter name

Functional description

[..]

Point Count Defines amount of a samples, accrued in one point frequency scales. At the sine wave form signals with the small contents of harmonics can be a little (4 samples), but at essential noise the resolution can continue to be increased and at increase samples over several thousand samples
Expectation At not a zero option value, outputs A [Lin] and B [Lin] and Lin (see table 3) will be made active at the end of measurement of the current module and phase. The option value is a time in msec, during which it is possible to observe values of arrays A [Lin] and B [Lin] on the plot. After the expiration of this time the current session of modeling will be completed automatically by Analyzer block msec

24.01.2001