Variable Structure Guidance Law With Attack Angle Constraint

As the most important precision guidance weapons in the modern battle field, the missile has become an important research direction of the development of world military power.guidance and control system is the core part of the missile, which plays a very important role in ensuring precision strike and stable flight control. However, with the new application requirements and especially new techniques, in order to improve operational effectiveness and penetration probability of the missiles, guidance laws with impact angle constraint bring new problems and challenges for terminal guidance and control of the missile.Firstly, the paper introduces the research background, purpose and significance, the main design method of the guidance and control system and the development status at home and abroad were Summarized. The mathematical model of the missile’s guidance and control system was discussed. Meanwhile, the paper proposed the dynamics and kinematic equations,geometric equations and so on. Relative moving relations of the missiles against the targets are established.Secondly, Some missiles with terminal impact angle constraints were required in the war,a guidance law based on the sliding mode variable structure control theory with miss distance and impact angle constraints was proposed for maneuvering targets. The target maneuvering was taken as a disturbance and an adaptive sliding mode approaching law was adopted,what’s more, the estimated equation of the target acceleration is deduced based on the linear variable structure guidance law, the simulation result demonstrates the estimated value. The obtained guidance law was simple and practical. The simulation shows that the guidance law can be used to ensure the missiles hit the maneuvering targets with the desirable impact angle,and the performances of the proposed guidance law were analyzed, the research can offer some references for engineering application. According to the dynamics and kinematics of the relative moving relations of the missiles against a stationary target in three-dimensional space, a three-dimensional impact angle constrained guidance law, based on the sliding mode control theory, is derived. Then, the extended trajectory shaping guidance law using the linear quadratic optimal control theory is analyzed and extended to the three-dimensional space to meet the terminal impact angle requirement. Finally, compared with the classical augmented proportional navigation guidance (APNG), numerical simulation results are presented to confirm the validity and superiority of the derived adaptive sliding mode guidance (ASMG) and the deduced extended trajectory shaping guidance (ETSG).In order to perform salvo attacks or cooperative attack missions. Based on the missile-target relative motion equations in the three-dimensional space, a impact time constrained three-dimensional guidance law was deduced for multiple missiles in attacking a stationary target simultaneously at the desired impact time. A sliding mode variable structure guidance law was adopted in the pitch channel and the yaw channel was controlled by a maneuver control system using the dynamic inversion control, the maneuver control instruction was able to adjust the impact time to a designated value, and the pitch control command was revised as the instruction of the derived augmented proportional guidance law for comparison. Finally, Numerical simulation results demonstrate that the proposed guidance law can make time-to-go error be ultimately reduced to zero and satisfies the requirements of the impact time as well as the guidance precision, the validity and superiority of the algorithm is confirmed.Finally, Aiming at the problem of guidance law design for intercepting stationary or slowly moving targets with the impact angle constraint, Based on the missile-target dynamics in the plane, a guidance law is designed considering missile’s autopilot lag using the sliding mode variable structure and nonlinear back-stepping control methods. The missile’s dynamics of autopilot can be approximately described as a first-order process, meanwhile, the chattering phenomenon of sliding mode is weaken by the integrated application of high gain saturation function and improved variable switch term. Line of sight angle rate will converge to zero ultimately and the trajectory inclination angle will ultimately converge to the desired value, respectively. Simulation results show that the guidance law can be used to hit the targets with desirable impact angle and the influence of the autopilot lag on guidance accuracy can also be compensated, which has good adaptability and robustness against the changes of the parameters and external disturbances. The research can offer some references for practical engineering application.