Research On Missile Guidance Law Based On Active Disturbance Rejection Control

The rapid development of modern military technology has put forward higher requirements for the guidance accuracy of missiles.The guidance stages of the missile are divided into the initial guidance stage,the middle guidance stage,and the terminal guidance stage.The performance of the terminal guidance will determine whether the missile can successfully intercept the target.Since the guidance time of the terminal guidance stage is very short,when designing the guidance law,the lineof-sight angular rate should be converged to zero within the finite time.The relative motion equation of the missile and the target is a complex nonlinear system.And the high-order nonlinear terms and cross-coupling terms contained in it will affect the guidance accuracy.So the three-dimensional space should be considered when designing the guidance law.In order to improve the guidance accuracy of missile terminal guidance stage,aiming at the interception of missiles against targets in three-dimensional space,this paper designs a finite-time guidance law and a threedimensional nonlinear guidance law when the target is maneuvering at constant speed and maneuvering at high speed.In the second chapter of this paper,when the target is maneuvering at constant speed,the interception problem of the missile in three-dimensional space is regarded as a combination of two two-dimensional space interception problems.Firstly,a finite-time state observer is designed to estimate the line-of-sight angular rate.Secondly,a finite-time guidance law based on the weighted homogeneous function is designed.And a saturation function is added to the design of the guidance law to solve problems such as missile overload.In terms of theoretical analysis,the finite time stability of the closed loop control system is strictly proved.Numerical simulation also verifies that the line-of-sight angular rate can converge to zero in finite time,which shows the effectiveness of the finite time guidance law.When the target is maneuvering at high speed,this paper proposes a weightedhomogeneous-function-based nonlinear active disturbance rejection control method considering the three-dimensional relative motion between the missile and the target.Firstly,a weighted-homogeneous-function-based extended state observer is proposed to online estimate the line-of-sight angular rate of the system and the total disturbances which are composed of high-order nonlinear coupling terms and uncertainties such as target acceleration,where the line-of-sight angle is the only output used in the observer and guidance law.Secondly,a nonlinear output-feedback three-dimensional guidance law based on the extended state observer is designed to achieve high-precision interception,where the total disturbances are compensated by using the observed value.The proposed guidance law overcomes the disadvantage influence of high-order nonlinear coupling terms and uncertainties,and improves the accuracy of the interception guidance.The stability and convergence of the closed-loop guidance systems are proved strictly with the explicit estimations of the observer.And the estimations show that the observer error and the line-of-sight angle can be as small as one expected by tuning the observer gain.It is also shown that the proposed method performs better than the existing guidance law based on linear extended state observer and fal-function-based extended state observer in terms of interception accuracy.And different from the existing methods based on the extended state observer,the existing methods only prove that the system states are bounded in the proof.But this paper gives the specific bounds of system states.Numerical simulations validate the effectiveness and the merits of the proposed method.