Active Control Of Helicopter Vibration By Using Piezoelectric Stack Actuators To Drive Gearbox Support Structs

Helicopters can take off and land vertically and hover in the air.Compared with other aircrafts,helicopters have many advantages.However,the helicopter fuselage always suffers from severe vibrations which will affect the normal work of pilots,reduce the pilot's accuracy and comfort of operation,lower the flight quality,increase the probability of accidents and affect equipment and weapon system effectiveness.Therefore,the control of the helicopter vibration is one of the most important challenges in the development of high-performance helicopters.In the thesis,an active control method of helicopter vibration by using piezoelectric stack actuators to drive gearbox support struts has been presented.The piezoelectric equations were deduced from the electrical and mechanical properties of piezoelectric materials.An ideal mechanical model created by using the piezoelectric equations determines the relationship between the input voltage and output of both the force and displacement in the piezoelectric stack actuator.Based on the mechanical model of piezoelectric stack actuators,the dynamic equations of the planar kinematic focal isolation system model were analyzed.The gearbox/fuselage coupled model was created by using the finite element method in Patran & Nastran software to get parameters related to the dynamic equations.The adaptive feed-forward control law of x-LMS algorithm were set up by adding the secondary controlling unit.Based on the x-LMS algorithm,several points were chosen to evaluate the vibration acceleration response.From the system dynamic equation,the state equation was deduced.The control model of the gearbox/fuselage coupled model was created in SIMULINK.The simulation results show that the system can isolate vibrations effectively and quickly in both steady exciting and change of exciting parameters.