Subjects: Mechanics >> Basic Mechanics submitted time 2023-04-24 Cooperative journals: 《应用力学学报》
Abstract： Rotor exitation is the main source of helicopter vibration,which effects pilot manipulation,comfortability as well as structural fatigue.Vibration problems are generally exposed during test flights,and problem handling and solution often require large cycles and costs,that affecting helicopter development.The prediction of helicopter vibration response is a major way to deal with vibration problems,which can be found in the early stage,convenient to carry out optimization design or solution plan in the early development stage of the helicopter.In this paper,a method to predicting vibratory response excited by rotors was presented,which takes vibratory loads of rotor center in nonrotating coordinate system as input,and based on the structural dynamic model.The method was proved to be effective,whose results had coordinated variation patterns as measured data,as well as satisfying accuracy of the engineering needs,through comparing analysis of predicted vibration response and measured ones excited by tail-rotor of the important positions of a certain helicopter.The method has high engineering value in vibration response analysis,vibration problem investigation and vibration control scheme formulation.
Subjects: Mechanics >> Applied Mechanics submitted time 2023-03-20 Cooperative journals: 《应用力学学报》
Abstract： The active vibration control system is an electromechanical integrated system which can reducethe vibration level of the platform by obtaining the vibration sensor signal and driving the actuator outputforce.The stability of the active vibration control system directly affects the experience of using the plat-form which obtains harsh vibrations.'The system is highly sensitive to component reliability when the sys-tem contains lots of hardware. In order to improve the functional reliability of the system without changingthe hardware , this paper proposes two system degradation modes of system control strategies and analyzestheir reliability.Based on the system degradation modes and switch methods , different levels of degradationmodes are designed accordig to the different number of hardware faults.According to the system controlparameters under different degradation modes, the optimal combination design of the actuator is proposed.And the optimal high-dimensional matrix of system model under different degradation modes is obtained.Finally , in the laboratory , the degradation mode of the actuator is experimentally verified in the active vi-bration control system test platform. By disconnecting the power supply of the actuator , the system workscorrectly for the vibration reduce function.
Subjects: Mechanics >> Applied Mechanics submitted time 2023-03-20 Cooperative journals: 《应用力学学报》
Abstract： The strong shock wave generated by the helicopter gun during launch not only damages the sur-rounding structure , but also causes the failure and damage of nearby equipment, the compatibility design ofaerial gun with projectile is always a dfficult problem in the development of armed helicopter. Based onthe classical theory of explosion mechanics and the measured results of an aerial gun ground target, thepressure field generated by the muzle shock wave is simulated numerically , and the difference of the timeof the positive pressure of the shock wave is considered , the space field and time pulse field of overpressuredistribution are established respectively.According to the structure scheme of the simulation platform andthe aerial gun , the overpressure dffusion process of the muzzle shock wave is simulated in the finite ele-ment software , and then the nonlinear transient analysis method is used, the impact process of helicopterplaform under overpressure is simulated , and the dynamic response of skin , frame and connecting structureis analyzed , which can provide reference for the design and structure optimization of ground platform.
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