Research Of Constant Thrust Attitude Control Method

Kinetic kill vehicle (KKV) is the primary weapon of the antimissile and antisatellite defence system, the rapidity and the stationary of attitude control system are the key whether KKV can intercept the target or not. The actuators of attitude control system employ 6 constant thrust on-off jets on the stern, then the issue to control the attitude of KKV is how to design the on-off logic of the attitude thrusters, and the method of pulse modulation is applied to be equivalent in practical. Bases on the attitude control of KKV, which employs constant thrusters, the continuous thrust control law is designed, and the continuous thrust is modulated to the equivalent constant thrust, and the simulation result shows that the method is valid, which responses quickly and saves fuel.Firstly, towards the nonlinear feature, the structures and the principle of the several pulse modulation methods are introduced, and the merits and faults of them are compared, then the pulse-width pulse-frequency(PWPF) modulation method is determined to make the continuous variable be equivalent to on-off variable. Secondly, the character of the PWPF modulator is analyzed, and the linear relationship between the duty cycle and the amplitude of the input signal is educed, which establishes the foundation to utilize the continuous control law in the KKV attitude control. Thirdly, to meet the challenge of the rapidity and the stationary of attitude control system, the linear quadratic optimum tracking theory is applied, and the feedback closeloop continuous attitude control law is designed, which implements the rapidity and stationary, and the election methods of the weighted matrix are discussed. Finally, the continuous attitude control law is equivalent to on-off variable by utilizing the PWPF modulation method, and the KKV constant thrust attitude control law is obtained, then the simulation and the analysis is made out, and the good control result is implement.According to the design and the simulation, the results indicate that utilizing the PWPF modulator can make the continuous thrust equivalent to the constant thrust, and designing the continuous attitude control law and implementing digital various thrust by using PWPF modulator can make the attitude control system of KKV tracking the target rapidly and stably.