SU892419A2 - Device for determining frequency characteristics of automatic control systems - Google Patents

Description

(54) DEVICE FOR DETERMINING FREQUENCY CHARACTERISTICS OF AUTOMATIC SYSTEMS

one

The invention relates to the technical means of research and control of automatic control systems and is intended to analyze the dynamic properties of industrial automation systems and their elements.

According to the main auth. No. 758079, a device for determining the amplitude is known. Phase frequency characteristics (AFCh) of automatic control systems, whose operation is based on recording the established sinusoidal oscillations at the input and output of the object under study 1 using an oscilloscope loop.

However, this device is characterized by the great laboriousness of processing the received vibration records and the need for additional calculations on them.

The closest to the proposed technical solution is a device for measuring amplitude and phase frequency characteristics of elements and automatic control systems, which contains a generator of sinusoidal oscillations, the output of which is connected to the first input of the phase shifter and the input of the object under study, connected in series.

the first synchronous detector, the integrator and the first multiplication unit, the corresponding input of which is connected to the first output of the phase shifter, the output is connected to one and the output of the object under study - to another input of the adder, the second synchronous detector, the first input of which is connected to the second output of the phase shifter, output is busy

10 through the second integrator with the second input of the phase shifter and the input of the indicator of the phase-frequency characteristic, and the output of the first integrator is connected to the input of the indicator of the amplitude-15 frequency response. In addition, the device includes a frequency sensor and a dead-band block connected in series, a gain correction block, and

20 second multiplication unit, with the first input of the first synchronous detector connected to the first output of the phase shifter, the control input of the gain correction unit connected to the output of the first integrator, the input of the frequency sensor is connected to the output of the sinusoidal oscillator, the output to the corresponding input of the second multiplication unit The output of which is connected to the second inputs of the first and second synchronous detectors, and the input of the dead zone unit is connected to the output of the adder 2. The principle of the device operation is based on the automatic compensation of the established reaction at the output of the object under study (t) aA ((Ju)) (1) by the signal XK from the output of the compensation circuit XK (t) aA sin (wt +), (2 g a, (ju is the amplitude and frequency of sinusoidal action at the input of the object; A (ui), (to) - amplitude and phase frequency characteristics of the object to be determined; A, h - estimates of the amplitude and phase frequency characteristics. At the moment of complete compensation of the inequality E, represented difference of signals from the output of the system under study and from the output of the compensation circuit E Hyych (t) -X, (t). (3 tends to zero. However, due to errors in the technical implementations of the device, as well as due to the presence of interference in E beam and a constant component due to, in particular, the measurement error of the X signal t at the output of the object and the deviations of its fop from the sinusoidal, in practice there is no complete zeroing of the gap. With a fixed dead zone contained in a known device, the process of adjusting the model is forcibly terminated at an amplitude of the unfixed E 1 D, where l is a constant value zo Nost's insensitive. At the same time, the relative value of the measurement measurement of the amplitude-frequency characteristic (AFC) i - g (i)) AM is the relative value of the amplitude Att and. the absolute error if (w) is related by the relation (((l +) g - / - t flowing in from formula (3). The magnitude of the measurement error of the APCF in accordance with expression (4) is in the range, t that at a constant value of q to the dependence of the relative measurement accuracy on the current value of A (LU). In addition, if there is a constant component in the output signal of the object, after the adjustment process is completed, oscillations with a constant amplitude are established in both the phase adjustment channel and the amplitude adjustment channel. inconvenience in counting the show indicators, these oscillations are a source of errors in determining the frequency characteristics, resulting in the need to compensate for the fixed component of the characteristic. The purpose of the invention is to improve the accuracy of the device for determining the frequency characteristics. connected to the output of the adder, the output is connected to the third input of the adder, the control input of the nonlinear element is connected to the output of the integrator of the amplitude adjustment channel amplitude. On fng. 1 shows a functional diagram of the device for determining the frequency characteristics of the elements and automatic control systems; in fig. 2 - graphs of temporary processes in the trim channels without an additional integrator; in fig. 3 schedules of temporary processes s channels of adjustment and at the output of an additional integrator when it is included in the scheme. The device for determining the frequency characteristics contains a generator of 1 sinusoidal oscillations connected by its bypass to the input of the object under study 2 and to one of two inputs of the phase shifter 3, the first output of which is connected to the first input of the multiplication unit 4 and to the first input of the synchronous detector 5, and the second output - to the first input of the synchronous detector 6. Phaser 3 with two inputs and two outputs, with the oscillation phase of the second output shifted by an angle with respect to the first one, and the multiplication unit 4 forms an output compensation circuit th signal of an object, wherein the compensation error (nev viscous) formed on the output of the adder 7, whose inputs are connected to outputs of the test object 2 and the multiplying unit 4. The output of the adder 7 through serially connected nonlinear element 8, block 9 gain correction and block 10 multiplication is connected to the second inputs of synchronous detectors 5 and 6, the outputs of which through integrators 11 and 12, equipped with indicators 13 and 14 amplitude and phase frequency characteristics, are connected respectively with the second inputs of multiplier 4 and phase shifter 3. To enter information about the frequency of the sinusoidal effect into the amplitude adjustment channels .15 and phase 16, the output of the frequency sensor 17 is connected to the second input Loka 10 multiplication. In order to compensate for the constant component of the delay, the device contains an integrator 18 connected by its input to the output of the adder 7, and an output to the third input of the adder 7. To enter information about the amplitude of the compensating signal, the output of the integrator 11 of the amplitude adjusting channel 15 is connected to the control input the gain correction unit 9 and the control input of the nonlinear element 8. In the presence of the constant component Hell, as well as the compensating signal RO (t), the negative output of the adder 7 takes the form

S Х4ь, х (t) -X (t) + Ao-A (, (t) (5)

I become equal in case

and A (ui); 4 1 (u);

AO JSC

those. the tunable parameters A and H of the compensation circuit are actually estimates of the amplitude and phase frequency characteristics, and the magnitude of the constant component A of the frame is compensated by the signal AO.

The algorithm of automatic adjustment of the parameters I, i and Hell to the desired values can be obtained by the gradient method according to the well-known relation

Y Q (Y), where the positive coefficient; Q (Y) E (Y) - quality criterion

  work cHCTeNM; Y, 4, Ag - vector of adjustable parameters.

Transition to the scalar form and taking into account equation (5), we obtain the algorithm for adjusting the model

r-Xe: AaSs nC ot4 ()),

Qn

ij, | | xa ecostu (}, (b). ,,

(I'm AO

where X 2 X.

The presence of the magnitude and as a factor in the algorithm for adjusting the phase leads to the complication of the technical implementation of the algorithm. This can be avoided using the algorithm

| AESin (wi-4

 Q ieco5 (ujt-K}),

,

the operability of which is confirmed by digital modeling (Fig. 3).

With full compensation of the constant component of the AO for the permeability of the measurement of the APCF, the magnitude of the characteristic E, at which the model adjustment process ends, is determined. The presence at the output of the adder 7 non-linear element with a dead band, regulated by law

a g A (tu), (7)

where f is the specified relative measurement accuracy, it allows one to forcibly complete the process of adjusting the model at a relative level of time, independent of the magnitude of the measured amplitude A (uj. In this case

° er GM LTiT

whence, taking into account (7), we have l (El y.

Since the value of A (o)) is to be determined and is unknown, the exact realization in the form of (7) of the law of adjustment of the deadband is impossible. However, considering that at the end of the measurement process (oi), its approximate realization is possible in the form of

Y X A (t).

Technically, this law is implemented in the invention by introducing the dead band type of the signal A (t) from the output of the amplitude adjustment channel integrator to the control input of a nonlinear element.

The proposed DC compensation, as well as the deadband control of the nonlinear element, allows the device to improve the accuracy of the frequency characteristics.

The use of the invention in engineering practice will reduce the time needed to design, debug, and various kinds of control tests of automatic control systems (for example, acceptance, resource, etc.), which gives a certain economic effect.

Claims (1)

1. Vavilov A.A. and others. Experimental determination of frequency characteristics the characteristics of automatic systems. M.-L., Gosenergoizdat, 1963, p., 15-11. 2, Copyright testimony USSR W 758079, cl. G 05 23/00, 1978 (prototype), g.1 t f, 9 A7 1, OB o o, k 0,6 0,8 t, c 2 AO Of - ,one e, if oh g about -0.2 / -0,1  (7