SU118994A1 - A device for calculating the Fourier coefficients - Google Patents

Description

In the known instruments for calculating the Fourier series coefficients, sinusoidal voltages are generated by rotating A (C transformers, and the integration is performed by electromechanical devices, which limits the frequency of the signals under study.

The proposed device allows to eliminate this drawback, as well as to increase the speed of computational operations and increase the range of operating frequencies.

This is achieved by the fact that the sinus block of the device is made in the form of an electronic generator of sinusoidal oscillations ic with adjustable frequency, and the integrating blocks are made in the form of a DC amplifier with a capacitance in the feedback circuit.

The device (see, diagram) has a command device — a generator / sweep and control, a generator 2 sinusoidal and a tangle | Soidal oscillations, two multiplying blocks 5 and two integrating blocks 5 and 6 and a output device made in the form of an electron-beam indicator 7.

The command device is designed to periodically send pulses to generator 2, Hz. They discretely change the frequency value to the output device, where the pulses control the electron-beam indicator, to integrating units, where the pulses reset to zero after each cycle.

Generator 2 generates sine and cosine voltages, which are then multiplied by the functions f (t). In the integrating blocks, the integrals of the products fed to the output device are calculated.

The principle of operation and operation of the instrument is as follows.

The relationship between the transient process and the frequency response of a linear automatic control system is established by preN 118994

F (1 co) Tr J dt,

where g (i) is the transient response of automatic control systems;

Tr is the upper limit of integration,

FS / COJ Tr - current Fourier transform.

The milling is done by steps for each of the quantities / (where r is 1,2, ... -100) and each step gives a dot |: full characteristic on the screen of the 8 electron-beam indicator with a long afterglow. Steps 0; Installed by means of a step finder, receiving pulses from the generator / sweep and control, and located in the generator unit 2 of low-frequency sinudoidal oscillations, which is assembled on the operational amplifiers of direct current.

The values of the voltage g (t) are entered by means of a photoelectric converter 9 directly from a film with a transient curve recording or from a curve set by the designer, in the form of profiled opaque tracing paper, a piece of profiled paperman, etc.

The input voltage X applied between the horizontal deflection plates of the beam of the cathode-ray tube 10 represents the voltage of the electron beam sweep along the horizontal axis of the tube and comes from the generator / scan output, the period of the beam stroke corresponding to the scanning time of the film and recording device and can vary with, if necessary, in a significant range. The voltage between the vertical plates is the output voltage g (t), since g ((K, t), where K. is a coefficient depending on the ratio of the speeds of movement of the flash during recording and the speed of sweeps of the electron beam. / C 1 we get gCX)) SOI changing the value of K opens up the possibility of introducing g (t) on a non-natural time scale, which is important when recording long-term transients.

The electronic units 5 and 4, including operational amplifiers and quadrants, provide output voltages equal to g (t) cos (Of and g (t) sin) t, respectively.

The integration of these expressions within O and Tp, where Tp is the working period of the sweep of generator 1, is performed by electronic integrators 5 and b, which are based on an operational DC amplifier with a high gain and operating accuracy. The values of the integrals at the output of the integrators 5 and 5 compose the actual Re () and imaginary terms / t (") of the Fourier transform and respectively provide the horizontal and vertical deflection of the beam of the electron-beam indicator. Working iodine sweep generator 1 emits a pulse beam opening electron-beam indicator 7, which fixes the screen 5, the found point of the frequency characteristic for the values Wj.

After the end of the moment of fixation of the solution for the pitch / on the screen of the cathode ray tube 10, the generator / issues a stopping pulse, which produces quenching of the beam of the cathode ray indicator, Fourier blocks. Practically, one has to deal with the current preFury, which complicates the ratio 2 -

integrating the output of the integrators to zero at Go time, as well as shifting the value of O), - the step finder of the sinusoidal oscillation generator by one step, setting the value M, - + I- Preparation for a new cycle of operation for a given h-1 occurs during TQ -: the time for the beam to move along the horizontal scanning of the tube of the photoelectric converter 9. At the moment of the end of Go, a trigger pulse is generated by the generator 1, which introduces the instrument into the new cycle of operation, the beam from the cathode ray tube 10 of the photoelectric converter is opened, the operation of the horizontal deflection of this beam is unblocked by the integrators and the integration process continues for a time T, p, at the end of which the beam of the electron-beam indicator opens and the integrator’s outputs are then again blocked to zero with a new stopping pulse of the generator /.

After the end of the work cycle for the value, the limit switch of the step finder of generator 2 stops the operation of the device, returning all its blocks to the initial position.

The process of automatically plotting the frequency response from the transition curve is completed. The proposed device can also be used as an automaton that determines the stability of a closed automatic control system along the transition curve of an open system. In this case, the device is supplemented with a zero-body, which is triggered at the moment of the transition of the value of 1t (w) through a zero value.

In addition, the curve g (t) € of the output of a simulator operating with the repetition of the solution is possible in the scheme of the proposed device.

Subject invention

A device for calculating the coefficients of the Fourier series of functions defined by electrical voltage, containing a command device and a sine, multiplying, integrating, and output units, characterized in that, in order to increase the speed of the device and increase the operating frequency range, the device’s sinus unit is electronic a sinusoidal oscillator with adjustable frequency, and integrating blocks in the form of a DC amplifier with a capacitance in the feedback circuit.

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