An oscillatory thrust is applied on a rocket model in an attempt to enhance the performance of the rocket during flight. The idea came from the inverted pendulum problem subjected to a vertical oscillatory motion at the pivot for stabilization.  Modern control theories suggested different methods to control the pendulum in the inverted state , by applying a state control feedback.The closed loop feedback allows us to exert a horizotal force on the pendulum that generates a stabilizing moment to return it back to its inverted position. However, a few scholars applied a different method of stabilization using vertical oscillations with specific amplitude and frequency of the exciting force. They examined how this will affect the stability and performance of the pendulum, referring to Jan Sieber,Ge Zheng and Smith Blackburn   . The study included detecting the stability regions as a parameter changes within the system using Bifurcation Analysis. In this thesis, we applied the theory of stabilization using vertical oscillations on a rocket’s thrust. A rocket during launch is an application that could be described as a pendulum in an inverted state . The vertical oscillations in the thrust is applied in the form of a sinusoidal wave of chosen amplitude and frequency; specifically an amplitude of 15% of the the average value of thrust and frequencies ranging from 1 to 100 Hz. This method of passive control shows stabilty of the rocket for some cases as well as a change in its performance. The rocket model is build and simulated in MATLAB and SIMULINK using the 6 DOF Aerospace Block. The results showed that only specific combinations of amplitudes and frequencies cause the rocket to stabilize or perform differently during flight. At a value of frequency of 4 Hz, the rocket reached higher altitudes than it had reached before applying the oscillations. Another phenomenon discussed is the subharmonic resonance of the parametrically driven pendulum under the influence of an exciting force that shows the effect of the sinusoidal amplitudes on stabiltiy. The phenomenon occurs at twice the natural frequency of the system causing a great change in its dynamics.
|Commitee:||Kalman, Joseph, Yoozbashizadeh, Mahdi|
|School:||California State University, Long Beach|
|Department:||Mechanical and Aerospace Engineering|
|School Location:||United States -- California|
|Source:||MAI 81/4(E), Masters Abstracts International|
|Keywords:||Bifurcation, Inverted pendulum, Matlab, Rocket, Thrust, Vertical Oscillations|
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