Research On Robust Nonlinear Integrated Guidance And Control Design

The ability of getting an accurate interception is the requirement of modern nation-al defense for missile weapons, and flight control and guidance algorithms are the key to achieve successful interception. Integrated guidance and control can coordinate the relationship between subsystems, and guarantee the stability of the overall system, so as to fully explore the potential of missiles and improve accurate interception capability. This dissertation focuses on the problems of guidance law design without line-of-sight (LOS) rate measurement, and modeling and control design of integrated guidance and control for homing missile against maneuvering or ground fixed targets. The main re-sults consist of the following parts:First of all, the modeling problem of the missile nonlinear integrated guidance and control system is considered. On the basis of the missile6-DOF nonlinear model and the relative motion model between missile and target, by using the coordinate trans-formation and viewing the acceleration elements in the trajectory coordinates and LOS coordinates as intermediaries, the nonlinear integrated guidance and control (IGC) mod-el is formulated considering the target maneuverability. The IGC model can reflect not only the relative motion between the missile and target, but also the varies of missile attitude (attack angle, pitch angle, and angular rates, etc.) during the flight process.Then, a three-dimensional guidance law without LOS rate measurement is pro-posed. Considering the interception of maneuvering targets and supposing all the states are measurable, a guidance law is designed based on input-to-state stability (ISS) to en-sure that the LOS rate is ISS with respect to target maneuvers. It is proved that, under the proposed guidance law, the LOS rate can converges to an arbitrary small neighbor-hood of the zero by adjusting the coefficients. The simulation results are also provided to test the algorithm. In practice, the LOS rate is always combined with missile body rates, so it is difficult to measure LOS rate accurately, which will affect guidance pre-cision. Thus, a high-gain observer is introduced into the guidance law to estimate the LOS rate, and the theoretical analysis as well as simulation results show that the perfor-mance of the closed-loop system under the guidance law with LOS rate measurement can be recovered by using a high-gain observer.Sequentially, the IGC model in pitch plane is formulated from the3D model, and the IGC law design problem is studied. To design an IGC law for missiles with sin-gle control input (canard control) against high speed targets with maneuverability, the backstepping is introduced, and adaptive control method is also used to handle the influ-ence of the nonlinear term. Canard control has its limit due to aerodynamic saturation at high angles of attack, which may affect the maneuverability of the missile, especially for long fuselage missiles, and a tail control is often preferred. Therefore, an IGC de-sign approach, against ground fixed targets, is proposed using small-gain theorem for missiles controlled by canard and tail control, which can guarantee a successful inter-ception with a desired impact angle. It is shown that the IGC law combining with ISS guidance law can be used in the interception of a maneuvering target. It is worth to claim that the designed IGC approaches do not rely on the assumption that the angle between LOS and missile velocity is almost constant. A successful interception as well as the stability of the overall system can be guaranteed by our approaches, which can be seen from both theoretical analysis and simulation results.Finally, considering the missile control system dynamics and uncertainties, the problem of approximative IGC design is studied. Due to the complexity of the3D IGC model, it is difficult to design IGC law directly. In order to improve the accurate inter-ception capability of missiles, missile control system dynamics and uncertainties may be considered in the guidance law design, which can be regarded as approximative IGC design. Here, the missile control system is viewed as one-order model and second-order model, and block backstepping and small-gain theorem are respectively used to design approximative IGC scheme based on the trajectory coordinates. The designed control can compensate for the effects of the closed-loop system dynamics and are ro-bust against the missile control system uncertainties and target maneuvers. Simulation results show the effectiveness of the approaches.