Study On Attitude Control Of Heavy Lift Launch Vehicle

With the increment of weight, thrust and slenderness ratio of new generation heavylift launch vehicles, control torques have to be provided by both strap-on rocket enginesand center rocket engines in attitude control. At the same time, the rocket shows thecharacteristic of low dense modal frequency, strongly coupled vibration and complexpartial deformation. what’s more,there exists a low-frequency resonance in theengine-servo loop. Thus a robust and reliable flight control system is necessarilydemanded to meet the higher performance requirements. Paper based on previous works,mainly studies the attitude control in boosting flight segment of heavy lift launchvehicles.Firstly, six degrees of nonlinear model and small deviation linear model are derivedthrough the rocket coordinate system. Meanwhile, the simulation platform is builtthrough using NI controls based on VC++6.0development environment.Secondly, duing to the complex flying surroundings the heavy lift launch confronts,The Sliding mode control strategy is adopted to design the three channel attitudecontrollers. As for chattering problem, a new dynamic integral sliding mode controlmethod derived through dynamic sliding model control and integral sliding model controlis proposed. The simulation results proved the effectiveness of the method.Thirdly, the original model is transformed to a new one with relative degree of twoand the active disturbance rejection control(ADRC) technique is used to design theattitude controller which treating the external disturbance and internal perturbance as apart of the total disturbance. The extend state observation(ESO) in ADRC observes andcompensates the value of total disturbance to achieve the purpose of hign-precisionattitude control. The effectiveness of ADRC is verified by the following simulationresults.Finally, the notch filter along with corrective network control strategy based onfrequence domain is adopted considering the influence of complex elastic vibration andengine liquid sloshing. It can be seen from the simulation results that the adoptive methodachieves the phase stability of low frequence flexure modes and amplitude stability of hign frequence modes as well as liquid sloshing which insures the stable flight of heavylift launch.