Abstract: A double degrees of freedom backstepping control method is proposed for large variation in load, strong disturbing torque due to launching and high tracking accuracy requirement. Control law is designed by deriving iteratively according to the mathematical model of servo system. Degree of freedom factor is used to adjust the control parameters, and the closed-loop controlling system is proved to be sta- ble through Lyapunov function. The simulation study of the position tracking under the conditions of ex- ternal disturbance and parameter perturbation was carried out, and the constant-velocity and sine-velocity tracking performances were experimentally analyzed. The simulation and experiment results show that the proposed approach can guarantee the response speed and control accuracy and has a strong robustness to the load disturbance and parameter perturbation.

Key words: ordnance science and technology, rocket launcher, servo control, double degrees of free- dom, back stepping, load disturbance, parameter perturbation, robustness