Missile Servo-aeroelastic Stability Analysis Method

Servo aeroelastics analysis is becoming more and more important in designing modern surface-to-air and air-to-air missiles when high velocity and super maneuverability were needed. A new method is applied to analyze axial symmetry and tandem wings distributed missiles in time domain, which be succeed in emulating servo aeroelastics problem of a surface-to-air missile. The primary coverage of this paper is listed below.1. The Branch Mode Method is used to reckon missile's structural dynamic characteristic, and the whole missile is regarded to be composed of three branches—the fuselage, the wings and the rudders. Using the Piston Theory with compressive correction to calculate unsteady aerodynamic force of the wings and the rudders, and using the Linear Perturbation Slender Body Theory to calculate the fuselage's unsteady aerodynamic force. Some engineering methods are employed to take into account the influences of atmosphere wash from the wings to the rudders and the atmosphere blockage from the fuselage and the wings to the rudders. The influences of atmosphere interference between the fuselage and the wings or the rudders are also analyzed. Regarding the angular velocity at sensor position as the input signal, and using the transfer function composed of pitching control loop or yaw control loop of the automatic pilot, then looking the rudders' deflection angle as the output signal. Finally aerodynamics, structure and control system are coupled in a motion equation, thereby the purpose of servo aeroelastics analysis is accomplished.2. The transfer function of the attitude control system in Laplace-domain and the motion equation are all transformed to state space, then be solved in time-domain. So the missile's servo aeroelastics problem can be simulated by numerical expression. The problem to which the missile's static unstability conduced is also managed.3. The flutter and servo aeroelastics analysis of a missile is finished, both full fuel condition and free fuel condition are calculated. By comparing with the solutions of flutter and servo aeroelastics analysis, it can be found that the attitude control system reduces the missile's aeroelastics stability. Proved that servo aeroelastics analysis should be taken into accounted other than flutter analysis.4. The attitude control system's influence on aeroelastics system is analyzed when altering the control system's parameters and the fuselage's natural frequencies, and drew some conclusions of the influence along with the change of control system and fuselage structure. It's instructive for designers of structure and control system.