Three-dimensional finite time convergence guidance law with extended state observer

Aiming at sending the line-of-sight angular rate to a small neighborhood of zero before hitting the target to achieve the interception of the missile to the target to quasi-parallel approaching state. Based on the active disturbance rejection control to estimate and compensate the uncertainties, a novel three-dimensional finite time convergence guidance law was presented accounting for the second order dynamics of missile's autopilot and target's maneuver. The finite time convergence of system was strictly proved based on the finite time convergence control theory. For the purpose of restraining measurement noise, the traditional tracking differentiator was modified to be applied in the process of designing a novel extended state observer and backstepping control. Simulation results demonstrate that the proposed guidance law can guide missiles to accurately intercept a maneuvering target with finite time, even if the autopilot has a lag, modified tracking differentiator has the advantages of high precision, fast response and strong ability of noise restraint, the extended state observer based on the modified tracking differentiator has better estimation effect.