SU739976A1 - Method and device for vibration testing of complex structures - Google Patents

Description

a certain number of forces that are valuable at the most characteristic points of the complex structure under test.

Most blyEGknm predlagaomomu to the technical essence and dostigaemrmu Uozultatu is a method vibratsiolnyh test complex designs, such as the aircraft on which ggrizvod tmngotochochnoe excitation of harmonic oscillations .konstruktsii fed via one controlled sinusoidal generator energizer i.osuschestvYaYaY5T resonant tuning to isolate the desired shape fluctuations, for which control the level of excitation of individual power drivers and the frequency of excitation, forming control drives with vibration-measuring transducers, which set If the excitation points of the structure.

At the same time, a general 15Oxenation level, which is small enough to avoid overloading the structure, is preset; an excitation reference point is chosen, in which the calculated product of mass and amplitude of oscillations is maximal for the vibration form under investigation, and a signal is sent to the power point connected and according to the signal of the vibration measuring transducer at this point, they regulate the frequency of the excitation until reaching the resonance, then successively turn on the exciters in the rest points controlling the excitation level and the energizer individual excitation frequency as long as all points not resonance is achieved. The resonance criterion is a specific (in dependence on the measured parameter-vibration) phase shift angle between the acceleration / g / force and vibration velocity (vibro-displacement, vibration velocity) at the point of excitation. In the automatic mode, the control signal is generated by comparing the phase of the signal of the vibration measuring transducer with the phase of the reference signal.

An apparatus for carrying out this method comprises a series-connected controlled sinusoidal generator, a unit for adjusting a common level of excitation, parallel

Channels are excited from the middle of the world.

level and energizer in each channel, vibration measuring transducers and by the number of channels and control switches to the control signal forming circuits, the phase detectors are turned on.

The use of the phase criterion of resonance does not always lead to a regrettable result. This is explained by

the fact that the oscillation point in which

contributes from the previously mentioned. the shift fg13 7 does not always characterize

oscillations of the whole structure. In cases where the amplitude of the oscillations noticeably affects the frequency, the process of adjusting the excitation forces is distorted by the influence of the nonlinearity of the structure, i.e. the resulting satisfactory distribution of forces for one P ° VD oscillation may not be suitable for another level. Adjusting the frequency by the phase shift only at the reference point does not always determine the correctness of the selection of the level and phase of the exciting forces at other points of the excitation, since the required phase shift at the reference point can be obtained with some random, not characterizing this form of oscillation. distribution of levels and phases of exciting forces.

The aim of the image is to increase the accuracy of the tests.

This is achieved by controlling the signals in the form of the in-phase and quadrature components of the sum of the vibration-measuring transducer signals converted to one sign and in the form of the squares of the quadrature or in-phase component signals of the vibration-measuring transducers using the first two signals of the common frequency and the excitation frequency so that the in-phase composition is constant, and the quadrature is equal to 0, or vice versa, and the level of excitation of individual energizers is controlled to ensure min immitating the sum of squares of quadrature or in-phase components of the signals of vibration-proof transducers, the failure to achieve minimization is taken as the criterion for the end of the resonant tuning.

The device for implementing the method has two control signal generation circuits, one of which contains cvMiviaTOp connected in series, a synchronous detector, one output of which is connected to the control input of a sinusoidal generator, and the other to the control input of the control unit of the overall excitation level phase inverters with an adder and vibration-measuring converters, and the other circuit of the formation contains synchronous synchronous connected in series to the vibration-measuring converters etektory, square n, otbroy cyMiviaTop, This device whose input is Mauger also be provided by the optimizer, for the exit of the second podklyu.chen sugFtatora and outputs - to the control inputs of the level regulator tori.

The drawing shows a block diagram of a device for carrying out the method. .

Claims (1)

The device contains sequentially connected controlled sinusoidal generator 1, -block 2 for adjusting the total excitation level, parallel excitation channels, each of which has a level 3 regulator and exciters 4 installed at the excitation points of the tested Design 5 vibration-measuring transducers 6 by number excitation channels and two circuits connected to converters of the control signal forming circuit. One of the formation circuits contains a series-connected adder 7, a synchronous detector 8, one output which is connected to the control input of the control unit for the overall excitation level, and the other output from the control input of the generator 1, and phase inverters 9, which are switched on selectively between the adder 7 and converters b using switches 10. Another shaping circuit contains synchronous detectors 11 that are sequentially connected to converters b, quadrants 12 and a second adder 13, the output of which can be connected to a control yuschimi inputs regulators opti.mizator 3 through 14. The test method is carried out as follows. Using block 2, the total level of arousal is set. A base point of excitation is selected. A signal is sent to the energizer 3 at the support point of structure 5 and the signal of the transducer B. installed at this point regulates the frequency of the generator 1 so that the signal of the vibration velocity is in phase with force. Then, signals are sent to all energizers 4. With the help of adder 7, a total signal is formed, beforehand, the common mode components are transmitted to a single sign using transmitting inverters 9. Using a synchronous detector 8, the total signal is spread to the common mode component (t i.e. in phase with reference signal) and quadrature component (i.e. shifted relative to reference signal). An in-phase component is supplied. block 2 and, by changing the level of arousal, maintain a constant value of the common-mode component, i.e. the level of oscillations of the structure 5 is kept constant. A quadrature component is supplied to the generator 1 and the excitation frequency is changed, the level of the quadrature component is maintained, i.e. provide a zero phase shift of the vibration velocity relative to the phase of the exciting force. A minimized signal is formed, for which, using synchronous detectors 1, the quadrature components of the transducer signals are extracted, quadratic squares are used to square them in order to eliminate the sign of the signal, and then the received signals are summed up. The excitation level in the individual channels is adjusted by means of level 3 controllers so that the magnitude of the signal being minimized decreases. This can be done by manual adjustment with observation of the magnitude of the minimized signal as measured by a voltmeter (not shown) connected to the output of the adder 13, or automatically using an optimizer 14. The process continues until the minimized signal reaches the lowest possible level (in limit zero). When using displacement or acceleration transducers instead of speed transducers, the minimized signal is formed as in-phase components, the signs of the sum components of the sum signal are determined by the sign of the w quadrature components. Accordingly, the level of oscillations is maintained by the quadrature, and the frequency by the in-phase component of the sum signal. The proposed method of testing complex mechanical structures and a device for its implementation make it possible to isolate the tone of oscillations of a nonlinear system much faster, more reliably and more qualitatively, by introducing into the process developed and theoretically reasonable adjustment criteria, such as the criterion for changing the frequency of the excitation and the criterion for changing the overall level of excitation as well as optimality criteria. . The use of the method and device for its implementation provides, in comparison with the existing methods, an increase in the accuracy of the test results, which leads to the creation of more perfect and high-quality tested structures, the time required for selecting the optimal test mode is significantly reduced, and, consequently, the test time is reduced, and the possibility of fully automating the tests, as well as eliminating the likelihood of structural failure during the test due to the limitation of the level fluctuations, which can be avoided when tested by a minimum number of expensive structures. Claims 1. A method of vibration testing of a complex structure, for example, an aircraft, according to which a multi-point excitation of harmonic oscillations of a structure is effected using a controlled sinusoidal generator