| Load simulation system is one of the important ground test equipments for rocket rudder.It reproduces all kinds of loads on rocket rudder under laboratory conditions,and completes the test of dynamic and static characteristics of the rudder.In order to address the testing work of the new generation of dual-resonant point vector engine,it is necessary to establish a more accurate multi-degree-of-freedom load simulation system with dual-resonant point load characteristics,and to conduct further research on non-linear friction load and the suppression of system resonance peak,respectively.Firstly,according to the mass distribution and flexible structure of the swing thrust vector engine,a complete mathematical model of multi-degree-of-freedom load simulation system is established,and the influence of inertia load mass on the dual-resonant peak of multi-degree-of-freedom load simulation system is detailed analyzed using frequency domain analysis method,which provides a means for adjusting the resonant peak frequency point for the servo test with different resonant characteristics.The method of describing function is used to linearize the harmonic of the system's non-linear friction load.The influence of friction load on the stability of the system is analyzed theoretically.The conclusion that the multi-degree-of-freedom load simulation system with non-linear friction load still has good stability is obtained.The amplitude-frequency characteristic equation and phase-frequency characteristic equation of the system with non-linear friction load are given.Furthermore,the mechanism and law of the influence of the non-linear friction load on the dynamic characteristics of the system are revealed.It is found that the non-linear friction load does not affect the resonance frequency of the system,but has a significant effect on the resonance peak amplitude at the resonance point.Secondly,this paper analyses the causes of the double resonance frequency characteristics of multi-degree-of-freedom load simulation system.Combining with the theory of notch compensation controller,a notch compensation controller based on three parameters of center frequency,bandwidth and attenuation depth is presented.A single resonance peak compensation controller and a double resonance peak compensation controller are designed for the system with double resonance points.The simulation results show that the single notch compensation controller has better resonance peak suppression effect.Finally,the AMESim simulation model of the multi-degree-of-freedom load simulation system is established,and the actual parameters of the load simulator are set and checked.The theory of non-linear friction load and resonance peak suppression is validated by combining AMESim simulation and experimental research.The validation simulation and experimental results not only verify the feasibility of inertial load to adjust the frequency of rudder resonance point,but also validate the effectiveness of single notch compensation to suppress the resonance peak of the system.In addition,the stability of the system under non-linear friction loading and the influence of friction load on the amplitude-frequency response of the system are also verified. |
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